New off-grid home in Honduras - could use some advice

Simple Guy · August 2010

We've already built our 2000sq ft home, and have a small compound of other buildings running on our off-grid solar energy system (grid tie isn't available to the site). We've already suffered through our first round of mistakes with our equipment. We're going to be purchasing some new (different) equipment this fall, and are looking for advice on two specific items.

First, what are your thoughts on forklift batteries? Because we can only get new equipment once a year, we want a workhorse of a battery. We are thinking along the lines of a 1000Ah/1500Ah 24 v forklift battery (or two). Does anyone have any experience using these with solar? We are being told that if we do not gas these batteries more often than once a week, and do not equalize them more than once a month, that we should anticipate 12 - 15 years of service from them. Is this realistic? We have 20-200watt solar panels and bring in about 600 - 800 watts per panel per day, average, which is more than sufficient for our needs. We use a lot of our power during the sunny hours (washing machine, refrigerator, fans, etc).

We have a generator for rainy days, so we're not trying to store massive amounts of electricity - our main concern is battery longevity.

The second question is similar to the first, but involves inverters. We had a 5000/10,000surge inverter (Walmart quality), that recently burned up (possibly related to a ground surge from a nearby lightning strike). We would like an inverter that also gives the most bang for the buck - a real workhorse.

Is it better to pay the extra money for a bigger inverter, so that you never encroach upon the limits of the inverter?

Maybe my real question is, what have people successfully used, and found to be reliable for 5 or more years?

Thanks for your help!

icarus · August 2010

Re: New off-grid home in Honduras - could use some advice

I think it a good idea if you give us some idea of your typical loading. It seems the best suggestion is to design from the ground up taking into account your loads, rather than trying to make the loads fit the system.

Tony

PS Welcome to the forum.

Cariboocoot · August 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy wrote: »

Maybe my real question is, what have people successfully used, and found to be reliable for 5 or more years?

Thanks for your help!

I might as well be the one to ask the question that is going to get asked:

What are your load requirements?

Lots of systems of all sorts can be found in the experiences of the forum members here, and most of them exceed a 5 year lifespan. Almost inevitably the failures can be directly linked to buying "inexpensive" components which turn out to be cheap instead.

Forklift batteries can be a viable option if they are readily and inexpensively available and you can manage them physically. But 15 years? That's probably stretching things a bit. It would depend on how often and how deeply they are cycled, the same as with any battery.

You've got quite a bit of panel there. No doubt the Honduran heat affects output significantly, but your figures indicate of 10 kW hours production per day? That's a lot of off-grid power! Are you sure you need so much? Running Air Conditioning by any chance?

Dave Angelini · September 2010

Re: New off-grid home in Honduras - could use some advice

Surrettes! L16's only for nearly 19 years! I expect 10 to 15 years and design for it! It is so simple and it is made to sound difficult. The deeper you discharge the shorter the life! Good Luck, in Guanaha?

niel · September 2010

Re: New off-grid home in Honduras - could use some advice

my comments in bold.

Simple Guy wrote: »

We've already built our 2000sq ft home, and have a small compound of other buildings running on our off-grid solar energy system (grid tie isn't available to the site). We've already suffered through our first round of mistakes with our equipment. We're going to be purchasing some new (different) equipment this fall, and are looking for advice on two specific items.

good for you in going this route, but maybe you could elaborate more on what you have and what you viewed as a mistake.

First, what are your thoughts on forklift batteries? Because we can only get new equipment once a year, we want a workhorse of a battery. We are thinking along the lines of a 1000Ah/1500Ah 24 v forklift battery (or two). Does anyone have any experience using these with solar? We are being told that if we do not gas these batteries more often than once a week, and do not equalize them more than once a month, that we should anticipate 12 - 15 years of service from them. Is this realistic? We have 20-200watt solar panels and bring in about 600 - 800 watts per panel per day, average, which is more than sufficient for our needs. We use a lot of our power during the sunny hours (washing machine, refrigerator, fans, etc).

many of the guys could tell you fork lift batteries work fine and are durable, but will suffer a bit on efficiency and will not keep its shelf-life charge (self discharge) very long. if those factors don't matter then you can use them.

We have a generator for rainy days, so we're not trying to store massive amounts of electricity - our main concern is battery longevity.

The second question is similar to the first, but involves inverters. We had a 5000/10,000surge inverter (Walmart quality), that recently burned up (possibly related to a ground surge from a nearby lightning strike). We would like an inverter that also gives the most bang for the buck - a real workhorse.

there are plenty of cheap modsine inverters out there and rather than get one huge inverter you may opt for several smaller ones and it may even save on the idle power. you must do research on this as to what is appropriate for you to use. there are plenty of name brand modsine inverters too that will cost more with xantrex and magnum just to name a few off the top of my head. there are also sine wave types out there that i would recommend getting for use on anything that contains an electric motor or coil like refrigerators or fans. the sine wave will allow better operation with lower power consumption than a modsine inverter and a better lifespan on the appliance too. the drawback is that sine wave inverters cost more.

Is it better to pay the extra money for a bigger inverter, so that you never encroach upon the limits of the inverter?

as i said, it depends, for that bigger inverter will have a larger idling draw of power. would you want to have a large basic draw due to having the large inverter available when you may only be needing a few hundred watts of power for lights, tv, etc?

Maybe my real question is, what have people successfully used, and found to be reliable for 5 or more years?

Thanks for your help!

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

icarus wrote: »

I think it a good idea if you give us some idea of your typical loading. It seems the best suggestion is to design from the ground up taking into account your loads, rather than trying to make the loads fit the system.

Tony

PS Welcome to the forum.

Thanks for responding, and thanks for the welcome to the forum.

In regard to our load, first let me say that we are in the mountains, but we are also in the tropics. Typical temperatures are 60's to upper 80's, and we more or less have sun year around - even in rainy season, when it rains every afternoon, we usually have good morning sun. There are seven of us currently living on the property, in two buildings. We process a lot of used clothing to give away, some of which has to be washed, my children use the computer for school, and we use it for communications back to the US.

2 - 3 loads of laundry per day, the machine seems to be using about 550 watts (according to my watt meter), with about 30 minutes use per load - 825 kwh (Also a concern of mine is that the washer kicks on and off very hard during agitation, about once a second, and I'm wondering if this might be hard on my inverter.)

refrigerator, 140 watts running approximately 12 hours per day - 1680 kwh

computer with satellite modem, running about 120 - 140 watts for 10 hours per day - 1300 kwh

dishwasher (although my wife lived without one for 14 years, she's really enjoying this luxury now) - 2 loads per day, 600 watts - 1200 kwh

fans at 80 watts per unit, 3 running about 4 hours per day - 960 kwh

TV/VCR and Xbox, 4 hours per day at 130 watts - 520 kwh

Lights, 4-25 watt light bulbs running 6 hours per night - 600 kwh

Other odds and ends (including occasional use of toaster, blender, grain mill, and lots of power tools) - only a guess, but around 500 kwh

That comes to 7585 kwh per day. When we have guests staying with us, this obviously goes up. Also, if we have enough power, I'd like to start running a chest freezer that we own, and I want to plan to have enough power for lights and fans in future buildings, and more lights for security.

Also, I realize that all the equipment has a diminished return as it processes the electricity.

Thanks again for your help!

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Cariboocoot wrote: »

I might as well be the one to ask the question that is going to get asked:

What are your load requirements?

You're right - it got asked! You can see my answer in the post above.

Lots of systems of all sorts can be found in the experiences of the forum members here, and most of them exceed a 5 year lifespan. Almost inevitably the failures can be directly linked to buying "inexpensive" components which turn out to be cheap instead.

Yeah, I've kind of gathered that, about the inexpensive components.

Forklift batteries can be a viable option if they are readily and inexpensively available and you can manage them physically. But 15 years? That's probably stretching things a bit. It would depend on how often and how deeply they are cycled, the same as with any battery.

I'm not afraid of them physically - I have a backhoe on site. The gentleman I spoke with suggested that I should never discharge them below 20%, and should try for more like 50%. He was also suggesting that if I didn't gas them I would have more like 95% when they were "fully charged." His idea was basically to get a battery that was big enough to handle staying between 95% and 50%, and then gas them once a week. He compared it to your grandmother's sterling silver, and every time you gassed it was like polishing the silver. In other words, in rubbing off the tarnish you were also removing some of the silver.

You've got quite a bit of panel there. No doubt the Honduran heat affects output significantly, but your figures indicate of 10 kW hours production per day? That's a lot of off-grid power! Are you sure you need so much? Running Air Conditioning by any chance?

We're not running AC, but we are using a refrigerator and would like to put on a freezer. We have steered away from appliances that we can't get parts for in country, so we haven't purchased special low-energy appliances. We also didn't use tracking mounts, because of the high winds, and also because with the sun more directly overhead for us here it doesn't change in position as much as for someone in Canada, for instance. So, to some degree, the extra panels are to make up for the panels being in a fixed position.

Thanks for your help.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Dave Sparks wrote: »

Surrettes! L16's only for nearly 19 years! I expect 10 to 15 years and design for it! It is so simple and it is made to sound difficult. The deeper you discharge the shorter the life! Good Luck, in Guanaha?

Hey Dave - you've anchored in Sandy Bay, haven't you? We lived in Guanaja for five years, but we're not there now. We've moved inland, and are up in the mountains of Western Honduras. Been here almost 5 years now.

I did a cost comparison of Surrette's L16's vs Industrial Forklift batteries, and I believe that I came up with a number that was about 80% more expensive, per lifetime kwh, for the Surrettes. Obviously all manufacturers gives you their best case scenerio when giving you their expected lifetime cycles. I am not afraid of the discharge on forklift batteries, as we will be using them every single day, and have 20 solar panels to replenish them. I am more concerned about getting an "indestructable" battery - even though I know none are really indestructable.

I think it is very important to me to get the right sized battery, so that my cycles are correct, although I don't want to get more battery than I need.

Thanks for the input!

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Originally Posted by Simple Guy

We've already built our 2000sq ft home, and have a small compound of other buildings running on our off-grid solar energy system (grid tie isn't available to the site). We've already suffered through our first round of mistakes with our equipment. We're going to be purchasing some new (different) equipment this fall, and are looking for advice on two specific items.

good for you in going this route, but maybe you could elaborate more on what you have and what you viewed as a mistake.

First, what are your thoughts on forklift batteries? Because we can only get new equipment once a year, we want a workhorse of a battery. We are thinking along the lines of a 1000Ah/1500Ah 24 v forklift battery (or two). Does anyone have any experience using these with solar? We are being told that if we do not gas these batteries more often than once a week, and do not equalize them more than once a month, that we should anticipate 12 - 15 years of service from them. Is this realistic? We have 20-200watt solar panels and bring in about 600 - 800 watts per panel per day, average, which is more than sufficient for our needs. We use a lot of our power during the sunny hours (washing machine, refrigerator, fans, etc).

many of the guys could tell you fork lift batteries work fine and are durable, but will suffer a bit on efficiency and will not keep its shelf-life charge (self discharge) very long. if those factors don't matter then you can use them.
We have a generator for rainy days, so we're not trying to store massive amounts of electricity - our main concern is battery longevity.

The second question is similar to the first, but involves inverters. We had a 5000/10,000surge inverter (Walmart quality), that recently burned up (possibly related to a ground surge from a nearby lightning strike). We would like an inverter that also gives the most bang for the buck - a real workhorse.

there are plenty of cheap modsine inverters out there and rather than get one huge inverter you may opt for several smaller ones and it may even save on the idle power. you must do research on this as to what is appropriate for you to use. there are plenty of name brand modsine inverters too that will cost more with xantrex and magnum just to name a few off the top of my head. there are also sine wave types out there that i would recommend getting for use on anything that contains an electric motor or coil like refrigerators or fans. the sine wave will allow better operation with lower power consumption than a modsine inverter and a better lifespan on the appliance too. the drawback is that sine wave inverters cost more.

Is it better to pay the extra money for a bigger inverter, so that you never encroach upon the limits of the inverter?

as i said, it depends, for that bigger inverter will have a larger idling draw of power. would you want to have a large basic draw due to having the large inverter available when you may only be needing a few hundred watts of power for lights, tv, etc?

Maybe my real question is, what have people successfully used, and found to be reliable for 5 or more years?

Thanks for your help!

We made three mistakes (in my opinion), maybe four.

1. I took advice from some people I probably shouldn't have.

2. We had a chance to get inexpensive marine batteries, and were told that these would last for 2 - 3 years (if we were careful with them), and then we could purchase something more substantial at that time. We originally had a bank of 16 12v 120amp hour batteries. The first battery died after seven months, and three more have died since. We are now at month 10, and we're limping along until we can get our next shipment from the US - in December.

3. As I mentioned, we went with 12volt, something we were told wasn't that important. When we went to get controllers, it made a big difference, obviously wire sizing is very different, 12volt vs 24volt or even 48volt. We are currently running 4 Outback FM80's, and although when we go to 24 volt we'd only need 3 of these, I'm planning to keep all of them on, so that they can dissipate any extra charge more easily. I would be interested in a 48 volt system, except for the fact that the higher the DC voltage seems to go, the fewer products seem to be available.

4. We used a 5000watt Wagan inverter. I figured by going bigger we wouldn't have to worry about many things running at once, such as washing machine, dishwasher, refrigerator, freezer, fans, etc, especially during the day, when the sun is shining hard. To the best of my knowledge we never had more than a 2500 watt load on the inverter, but it still burned up. However, we're not really sure if it burned up due to our usage, or if it was related to the recent lightning strike 600ft from the house.

On an up note, the solar panels seem to be working great, and the FM80 controllers seem to be doing a good job. These are obviously the things that we initially put most of our funds into.

On inverters - when you mentioned xantrax and magnum, are you talking about something along the line of a 2000/2500watt in size? What about a washing machine, with its hard on-off cycling every second or two during the wash cycle - is that hard on the inverter? Are you running a washing machine on an inverter, and can you tell me your experience with that?

Thanks for the help!

Cariboocoot · September 2010

Re: New off-grid home in Honduras - could use some advice

From my POV:

You're spot on about the mistakes you've already made. You're not alone; almost everyone does it wrong to begin with!

As far as batteries are concerned, the lifespan vs. depth and frequency of cycling is the same across all types; the more you use them, the deeper you drain them, the shorter the life. Those marine batteries aren't "true deep cycle" but are a sort of hybrid design that doesn't really work well for RE applications.

I'm a bit confused about that washing machine. During agitation the motor itself should run continuously; it is a mechanical operation to alter agitation function. This might be some kind of odd machine I've never encountered before, though. A good inverter should not be affected by how often or how deeply it's drawn upon providing the demand is within specs. This is why I say never relay on surge ratings for anything. I suspect your inverter was an MSW type, which are notoriously incompatible with any AC induction motor.

You just might want to go for a multiple inverter set-up here, to keep the constant draw to a minimum. You could use inexpensive MSW for lighting and non-motor applications, a medium sized TSW type for refrigeration draw (about 2 kW) and perhaps an additional one switched on just for laundry. Or a back-up generator for laundry, if it's feasible (fuel availability & cost).

Sounds like lightning protection would be a real good idea. Remember you can never get 100% protection, you can only reduce the risk of damage from the elevated stray Voltage that surrounds a strike. A direct hit still blows things to bits and melts all the metal and starts fires.

Kamala · September 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy,

I'm sure it is a benign oversight, but you have over estimated your loads by a factor of ten. In post #6 you have repeatedly used the term kWH when you should have used simply WH. Near the end of that post your daily load is given as 7585 kWH per day. That's about 7.6, call it 8 MEGA watt-hours. I checked a few of your calcs and noticed the spurious k in the WH nomenclature.

So you're at about 8 kwh per day.

K

Cariboocoot · September 2010

Re: New off-grid home in Honduras - could use some advice

Good catch, Big K!

You know I "automatically edited" that to something that made sense; 8 kW hours.

It's so easy to make a slip like that - we all do it from time to time. It's something to be careful about.

niel · September 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy wrote: »

Originally Posted by Simple Guy

We made three mistakes (in my opinion), maybe four.

1. I took advice from some people I probably shouldn't have.

2. We had a chance to get inexpensive marine batteries, and were told that these would last for 2 - 3 years (if we were careful with them), and then we could purchase something more substantial at that time. We originally had a bank of 16 12v 120amp hour batteries. The first battery died after seven months, and three more have died since. We are now at month 10, and we're limping along until we can get our next shipment from the US - in December.

3. As I mentioned, we went with 12volt, something we were told wasn't that important. When we went to get controllers, it made a big difference, obviously wire sizing is very different, 12volt vs 24volt or even 48volt. We are currently running 4 Outback FM80's, and although when we go to 24 volt we'd only need 3 of these, I'm planning to keep all of them on, so that they can dissipate any extra charge more easily. I would be interested in a 48 volt system, except for the fact that the higher the DC voltage seems to go, the fewer products seem to be available.

4. We used a 5000watt Wagan inverter. I figured by going bigger we wouldn't have to worry about many things running at once, such as washing machine, dishwasher, refrigerator, freezer, fans, etc, especially during the day, when the sun is shining hard. To the best of my knowledge we never had more than a 2500 watt load on the inverter, but it still burned up. However, we're not really sure if it burned up due to our usage, or if it was related to the recent lightning strike 600ft from the house.

On an up note, the solar panels seem to be working great, and the FM80 controllers seem to be doing a good job. These are obviously the things that we initially put most of our funds into.

On inverters - when you mentioned xantrax and magnum, are you talking about something along the line of a 2000/2500watt in size? What about a washing machine, with its hard on-off cycling every second or two during the wash cycle - is that hard on the inverter? Are you running a washing machine on an inverter, and can you tell me your experience with that?

Thanks for the help!

1> yes, that happens sometimes.

2> really cheap ones could give problems when pressed into a solar setup where they are relied upon greatly. they may have warranties that may be 30 or 90 days. don't get me wrong here as sometimes they do fine and it depends on if you plan it out well enough and you get lucky as to premature failures. do note that any battery can have a premature failure, but the better ones have better quality control and less premature failures. i do agree that mistakes should be with crappy batteries or more specifically cheaper in cost. all batteries do need to be charged up with 5-13% of a charge rate and not depleted below 50% depth of discharge (dod) in addition to adding distilled water (for flooded lead acid batteries {fla}). when it starts going low as any exposed plates will quickly sulfate and eventually destroy the battery.

3> working battery voltage can make a big difference. if you decide on higher voltages for the battery bank you must get the inverter to match that voltage and being in the market now for one it is time to make that decision on the voltage.

4> as i said multiple inverters may be a better answer for you, but if you go with one it should be of quality. those loads you cite some should be with sine wave as the modsine will cause an excessive dissipation of power on the loads due to harmonic content and a shortening of the appliance lifespan. i can't tell you the best way that will work out for you let alone make your decisions on equipment and how much you spend on it as that will be your choice as we only advise, but most times you get what you pay for.

the lightning is a very strong possibility on your inverter blowing out and as advised already you should implement some measures against it.
there are many threads throughout the forum on all of these areas that you need to address.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Cariboocoot wrote: »

From my POV:

You're spot on about the mistakes you've already made. You're not alone; almost everyone does it wrong to begin with!

Yes, but I don't want to repeat myself! :roll:

As far as batteries are concerned, the lifespan vs. depth and frequency of cycling is the same across all types; the more you use them, the deeper you drain them, the shorter the life. Those marine batteries aren't "true deep cycle" but are a sort of hybrid design that doesn't really work well for RE applications.

I'm a bit confused about that washing machine. During agitation the motor itself should run continuously; it is a mechanical operation to alter agitation function. This might be some kind of odd machine I've never encountered before, though. A good inverter should not be affected by how often or how deeply it's drawn upon providing the demand is within specs. This is why I say never relay on surge ratings for anything. I suspect your inverter was an MSW type, which are notoriously incompatible with any AC induction motor.

This is what I thought, but I had a mechanical engineer tell me that the motor cuts on and off. I don't know for myself that this is true, although it does appear on the inverter that the wattage jumps up and down. On the Kill A Watt Meter, the wattage seems to remain more constant. ???

You just might want to go for a multiple inverter set-up here, to keep the constant draw to a minimum. You could use inexpensive MSW for lighting and non-motor applications, a medium sized TSW type for refrigeration draw (about 2 kW) and perhaps an additional one switched on just for laundry. Or a back-up generator for laundry, if it's feasible (fuel availability & cost).

How bad is it, to use an MSW for refrigeration?

Sounds like lightning protection would be a real good idea. Remember you can never get 100% protection, you can only reduce the risk of damage from the elevated stray Voltage that surrounds a strike. A direct hit still blows things to bits and melts all the metal and starts fires.

Yes, the equipment was grounded, but actually the surge seems to have come up through the ground, as none of the solar panels or buildings were affected. ???

Thanks for your thoughts.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Kamala wrote: »

Simple Guy,

I'm sure it is a benign oversight, but you have over estimated your loads by a factor of ten. In post #6 you have repeatedly used the term kWH when you should have used simply WH. Near the end of that post your daily load is given as 7585 kWH per day. That's about 7.6, call it 8 MEGA watt-hours. I checked a few of your calcs and noticed the spurious k in the WH nomenclature.

So you're at about 8 kwh per day.

K

LOL! Sorry - actually I overestimated my loads by a factor of 1000! Thanks for catching that.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

niel wrote: »

1> yes, that happens sometimes.

2> really cheap ones could give problems when pressed into a solar setup where they are relied upon greatly. they may have warranties that may be 30 or 90 days. don't get me wrong here as sometimes they do fine and it depends on if you plan it out well enough and you get lucky as to premature failures. do note that any battery can have a premature failure, but the better ones have better quality control and less premature failures. i do agree that mistakes should be with crappy batteries or more specifically cheaper in cost. all batteries do need to be charged up with 5-13% of a charge rate and not depleted below 50% depth of discharge (dod) in addition to adding distilled water (for flooded lead acid batteries {fla}). when it starts going low as any exposed plates will quickly sulfate and eventually destroy the battery.

fyi - we are currently only using 8 solar panels for just this reason - to control the charge rate and protect the batteries.

3> working battery voltage can make a big difference. if you decide on higher voltages for the battery bank you must get the inverter to match that voltage and being in the market now for one it is time to make that decision on the voltage.

4> as i said multiple inverters may be a better answer for you, but if you go with one it should be of quality. those loads you cite some should be with sine wave as the modsine will cause an excessive dissipation of power on the loads due to harmonic content and a shortening of the appliance lifespan. i can't tell you the best way that will work out for you let alone make your decisions on equipment and how much you spend on it as that will be your choice as we only advise, but most times you get what you pay for.

hence my curiosity about 24 volts vs 48 volts - it seems to me that there are a lot more inverters available at 12 volts than at 24 volts, and even fewer at 48 volts. ???

the lightning is a very strong possibility on your inverter blowing out and as advised already you should implement some measures against it.

What do you think I should be looking for - a lightning arrester? I already have the inverter grounded, but this seems to be where the electrical surge (if there was one) would have had to come in.

there are many threads throughout the forum on all of these areas that you need to address.

Thanks again so much for your help.

BB. · September 2010

Re: New off-grid home in Honduras - could use some advice

A few random answers:

The washer power draw is probably varying as the dasher moves back and forth... The Kill-a-Watt meter only displays readings ~once per second--so it is averaging/missing the peaks and valleys of your power usage. However, usually motors take a lot more current when they first start and average less once running, they don't vary the current usage that much.

Note, especially with motors, there can be a big difference between current and power. We usually type the power equation as:

Power = Voltage * Current

and that is pretty much 100% true for DC current.

For AC current, the relationship between the voltage and current sine waves is also critical... That equation can be written as:

Power = Voltage * Current * Cos (angle between voltage / current sine waves)

Also written as:

Power = Voltage * Current * Power Factor (PF)

So, if you measure the current from your motor (and Volts*Amps), you will probably not find as much as much change as when measuring power (voltage*Current*PF)... The PF for a typical motor is around 0.6-0.7 and will change with load (getting closer to 1.0 as the load goes up).

If you remember your math/physics, Power is a Vector Quantity and you need to account for the phase angle between the voltage and current.

For the inverter, Volts*Amps or Amps is important. No meter the value of Power Factor, the Current is real and they wiring and components need to be large enough to handle the power.

For the battery bank, the inverter's DC input is more or less the Power (V*I*PF) and that is what the bank and your solar panels will be designed around.

Regarding lightning, our host (Windsun) said that lightning damage tended to take out the AC output side of Off-Grid inverters (that was the most common damage he saw).

Unfortunately, that is the price of going off grid--having spares on the shelf to take care of failures/lightning induced damage.

There have been lots if bits and bytes spilled around here about lightning and how to best protect equipment--But, in the end, there will be damage if the bolt hits close enough. And lightning/surges can damage electronic components and cause earlier life failures (everything works, but something fails a few months later and you think it was caused by some load you may have plugged in).

Regarding MSW vs TSW inverters... If you can afford TSW, go with TSW.

Probably 80% of the equipment will work fine on MSW and 10% will die an early death/waste a lot of extra power... The problem is predicting which will work and which will fail.

Small wall transformers, sealed motors (like refrigerator/freezers), power transformers, heavily loaded motors, and some "cheap electronics" tend to overheat/fail with MSW inverters.

Electric heaters, oversized motors with low duty cycles (saws, drills, water pumps), filament light bulbs, etc. tend to be OK on MSW inverters.

Interestingly (because of the electronic designs), electronic appliances with high Power Factor (>0.9 or 0.95) may work OK on MSW inverters too. Electronics with poor Power Factor ( <0.8 ) may tend to fail/overheat/short life.

If I was designing a system for minimum costs... I would probably go with a 1.5 to 2 kW TSW inverter and use a large/cheap MSW inverter to run a non-electronic washer/vacuum/shop tools/etc...

You may even go with three inverters... A small TSW (with search mode for lower power) to run cell phone chargers, laptop, a few lights, radio, etc... A larger one that runs optional loads (TV, desktop, refrigerator, etc.). And the MSW for a well pump.

A couple of Inverter FAQs:

All About Inverters
Choosing an inverter for water pumping

-Bill

Cariboocoot · September 2010

Re: New off-grid home in Honduras - could use some advice

I confess to getting a bit "lost in the sauce" already but ...

Your washing machine will not like the MSW inverter's (which I suspect you have/had) output. It will draw more current and run less efficiently and heat up and fail prematurely. More so than a refrigerator.

Yes there are more 12 Volt inverters than anything else, but when you go up in Wattage you want to go up in system Voltage to reduce current draw. And while were on the subject, what sort of AC power do you use there? 120 @ 60 Hz, 240 @ 60 Hz, 230 @ 50 Hz ??? Lots of possibilities.

I hate to sound like an advertisement for Outback, but their equipment might be a good choice for an integrated, multi-power level system such as your needs seem to be. On the other hand, Xantrex is 240 VAC "right out of the box".

Dave Angelini · September 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy wrote: »

Hey Dave - you've anchored in Sandy Bay, haven't you? We lived in Guanaja for five years, but we're not there now. We've moved inland, and are up in the mountains of Western Honduras. Been here almost 5 years now.

I did a cost comparison of Surrette's L16's vs Industrial Forklift batteries, and I believe that I came up with a number that was about 80% more expensive, per lifetime kwh, for the Surrettes. Obviously all manufacturers gives you their best case scenerio when giving you their expected lifetime cycles. I am not afraid of the discharge on forklift batteries, as we will be using them every single day, and have 20 solar panels to replenish them. I am more concerned about getting an "indestructable" battery - even though I know none are really indestructable.

I think it is very important to me to get the right sized battery, so that my cycles are correct, although I don't want to get more battery than I need.

Thanks for the input!

Yes, Sandy bay was beautiful! Probably you are much better off in the mainland mountains during the mean season. I would buy whatever the local dealer can support in Honduras. Always buy the best offgrid! I do remember one thing about sunrise and sunset in the tropics, damn fast!
Take Care!

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

BB. wrote: »

A few random answers:

The washer power draw is probably varying as the dasher moves back and forth... The Kill-a-Watt meter only displays readings ~once per second--so it is averaging/missing the peaks and valleys of your power usage. However, usually motors take a lot more current when they first start and once running, they don't vary the current usage that much.

Note, especially with motors, there can be a big difference between current and power. We usually type the power equation as:
Power = Voltage * Current

and that is pretty much 100% true for DC current.

For AC current, the relationship between the voltage and current sine waves is also critical... That equation can be written as:
Power = Voltage * Current * Cos (angle between voltage / current sine waves)

Also written as:
Power = Voltage * Current * Power Factor (PF)

So, if you measure the current from your motor (and Volts*Amps), you will probably not find as much as much change as when measuring power (voltage*Current*PF)... The PF for a typical motor is around 0.6-0.7 and will change with load (getting closer to 1.0 as the load goes up).

If you remember your math/physics, Power is a Vector Quantity and you need to account for the phase angle between the voltage and current.

For the inverter, Volts*Amps or Amps is important. No meter the value of Power Factor, the Current is real and they wiring and components need to be large enough to handle the power.

For the battery bank, the inverter's DC input is more or less the Power (V*I*PF) and that is what the bank and your solar panels will be designed around.

Regarding lightning, our host (Windsun) said that lightning damage tended to take out the AC output side of Off-Grid inverters (that was the most common damage he saw).

Unfortunately, that is the price of going off grid--having spares on the shelf to take care of failures/lightning induced damage.

There have been lots if bits and bytes spilled around here about lightning and how to best protect equipment--But, in the end, there will be damage if the bolt hits close enough. And lightning/surges can damage electronic components and cause earlier life failures (everything works, but something fails a few months later and you think it was caused by some load you may have plugged in).

Regarding MSW vs TSW inverters... If you can afford TSW, go with TSW.

Probably 80% of the equipment will work fine on MSW and 10% will die an early death/waste a lot of extra power... The problem is predicting which will work and which will fail.

Small wall transformers, sealed motors (like refrigerator/freezers), power transformers, heavily loaded motors, and some "cheap electronics" tend to overheat/fail with MSW inverters.

Electric heaters, oversized motors with low duty cycles (saws, drills, water pumps), filament light bulbs, etc. tend to be OK on MSW inverters.

Interestingly (because of the electronic designs), electronic appliances with high Power Factor (>0.9 or 0.95) may work OK on MSW inverters too. Electronics with poor Power Factor (<0.8) may tend to fail/overheat/short life.

If I was designing a system for minimum costs... I would probably go with a 1.5 to 2 kW TSW inverter and use a large/cheap MSW inverter to run a non-electronic washer/vacuum/shop tools/etc...

You may even go with three inverters... A small TSW (with search mode for lower power) to run cell phone chargers, laptop, a few lights, radio, etc... A larger one that runs optional loads (TV, desktop, refrigerator, etc.). And the MSW for a well pump.

A couple of Inverter FAQs:

All About Inverters
Choosing an inverter for water pumping

-Bill

You say that lightning is one of the problems with an off-grid system, and there isn't much I can do about it, so would you think that it would be smarter, then, to go with a lower cost (lower quality) piece of equipment, with the plan that if lightning strikes, the replacement cost is less?

As far as the difference between TSW and MSW, is $1000 difference worth it, or do you think it is better to just plan to replace equipment that died because you were running the MSW? None of our appliances are of especially high value.

Thanks so much for all your input on this.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Cariboocoot wrote: »

I confess to getting a bit "lost in the sauce" already but ...

Your washing machine will not like the MSW inverter's (which I suspect you have/had) output. It will draw more current and run less efficiently and heat up and fail prematurely. More so than a refrigerator.

Yes there are more 12 Volt inverters than anything else, but when you go up in Wattage you want to go up in system Voltage to reduce current draw. And while were on the subject, what sort of AC power do you use there? 120 @ 60 Hz, 240 @ 60 Hz, 230 @ 50 Hz ??? Lots of possibilities.

I hate to sound like an advertisement for Outback, but their equipment might be a good choice for an integrated, multi-power level system such as your needs seem to be. On the other hand, Xantrex is 240 VAC "right out of the box".

We use 120 @60 Hz, and we really don't need 240 except for welding. We have a propane oven and hot water heater, and we don't run a dryer. I'm very interested in the Outback inverter, as I very much like my FM80's, and I notice Xantrex wants you to use their controllers with their inverters. Does anyone know what it takes to maintain a warranty with either Outback or Xantrex?

What do you think of the Outback Power VFX3524 3500 Watt Sine Wave Inverter?

Thanks for your help.

mike95490 · September 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy wrote: »

As far as the difference between TSW and MSW, is $1000 difference worth it, or do you think it is better to just plan to replace equipment that died because you were running the MSW? None of our appliances are of especially high value.

There is another difference, power consumption. Motors and transformers of all types will consume about 20% more power on mod-square wave, than they do on pure sine. The extra power is a drain on your system, you 100 motor or cordless drill charger is now consuming 120W, and can overheat and die, or just drain your battery faster.

BB. · September 2010

Re: New off-grid home in Honduras - could use some advice

That is the $1,000 question... I would suggest that you talk with your local supplier and find out what they find to be a reliable unit.

Sealed units with good cooling and high efficiency (less wasted energy means less heat build up internally)--Should be a higher quality/longer lasting unit.

But a near/direct hit from lightning--nothing is going to withstand that strike.

Lightning protection--Lots of different ideas and theories--And I am certainly no expert... A few threads where lightning has been discussed:

Off Grid Grounding Technique?
Another Question, this time about Lightning

From Windsun's general FAQs; Lightning FAQ:

Lightning Protection for PV Systems

What is best for your setup??? Generally, the less expensive MSW inverters only allow you to ground the electrical system in one place--Typically the negative battery bus to earth/safety ground. If you try to "ground the neutral" like the NEC does for homes in North America to the same safety ground--It will generally toast the MSW inverter the first time it is turned on.

And, with most TSW inverters, you can ground the DC side to the ground rod, and also "bond the 120/240 VAC neutral" to the same ground rod just fine. Will this be a more "lightning resistant" setup? Don't know.. A bolt that has just traveled miles through the air is not going to care much about a 1/4" insulation gap somewhere in your inverter.

Note: As always, read the instruction manuals, there are exceptions to every rule of thumb.

Read about grounding a system... The biggest issue (from my humble opinion) is when you have grounds that are separated by distance--Say you have a solar array 100' away from the battery shed/home... If you put a ground in at the array and another ground at the home--you can inject current into your wiring from ground (strike near array raises the ground voltage at the array ground--and sends some of the strike energy down the grounded wires into the shed/home which then flows to the local ground).

Generally, it is better to use the same (single) ground point for all equipment. If you have to drive a bunch of rods... Wire them all to a central rod and run all electrical grounds to that one rod (center of a star type grounding).

-Bill

Cariboocoot · September 2010

Re: New off-grid home in Honduras - could use some advice

Simple Guy wrote: »

We use 120 @60 Hz, and we really don't need 240 except for welding. We have a propane oven and hot water heater, and we don't run a dryer. I'm very interested in the Outback inverter, as I very much like my FM80's, and I notice Xantrex wants you to use their controllers with their inverters. Does anyone know what it takes to maintain a warranty with either Outback or Xantrex?

What do you think of the Outback Power VFX3524 3500 Watt Sine Wave Inverter?

Thanks for your help.

This is the inverter I use personally. It's excellent, but ... costs money. Especially as you need a MATE controller to program it with, which is extra cost. To really do a good OB system, you need a HUB and the wires so that all the pieces (including the FM80's) "talk" to each other and share data regarding battery state and set points and temperature. The standby current on the OB is a bit high; mine uses roughly 20 Watts when it's doing nothing. The other issue is your maximum draw at any one time; if it is likely to be over 3 kW then you may want to double up on inverters, as 3.5 kW is a tad "optimistic" output. A second OB inverter can be stacked to add capacity, and it will sit idle until needed. But at roughly $2,000 each ... plan carefully!

I think I'd go with some type of true sine wave inverter if only for the motors. Look at the Magnum line up as well: http://store.solar-electric.com/maensiwainac.html You can get a 4 kW unit for about the same money as the 3.5 OB.

Dave Angelini · September 2010

Re: New off-grid home in Honduras - could use some advice

One flaw I see in your thinking is that you say you do not want more battery than you need! The thing you don't want is more battery than you can fully charge on a daily basis. Having more battery than you need is the basis for long battery life offgrid!

I am remembering more about Sandy Bay on Guanaja thanks to you! I think the rum was cheaper than drinking water and the huts over the water only had rum...
There was a dolphin we swam with there every morning.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Dave Sparks wrote: »

One flaw I see in your thinking is that you say you do not want more battery than you need! The thing you don't want is more battery than you can fully charge on a daily basis. Having more battery than you need is the basis for long battery life offgrid!

I am remembering more about Sandy Bay on Guanaja thanks to you! I think the rum was cheaper than drinking water and the huts over the water only had rum...
There was a dolphin we swam with there every morning.

Yes, many days we had dolphins swimming alongside our boat or diving with us!

I was told that we should almost fully charge our batteries every day, almost up to the point of "gassing" them, but without gassing them, and then once a week we should gas them. The electrical engineer I spoke with at Giant Battery suggested that in staying above 50% charge and below 99% charge would give us the greatest battery longevity. But by gassing them once a week, we could maintain the battery's full capacity. Do you have thoughts on this?

I've been looking at purchasing either one or two forklift batteries. These 24volt batteries have a 6 hour 80% discharge of 1000 Ah and a 20 hour 80% discharge of 1560 Ah. I could go with a 48 volt battery, but actually they are a bit more expensive per watt hour, and there seemed to be less inverters available in the 48 volt range.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

BB. wrote: »

That is the $1,000 question... I would suggest that you talk with your local supplier and find out what they find to be a reliable unit.

Sealed units with good cooling and high efficiency (less wasted energy means less heat build up internally)--Should be a higher quality/longer lasting unit.

But a near/direct hit from lightning--nothing is going to withstand that strike.

Lightning protection--Lots of different ideas and theories--And I am certainly no expert... A few threads where lightning has been discussed:

Off Grid Grounding Technique?
Another Question, this time about Lightning

From Windsun's general FAQs; Lightning FAQ:

Lightning Protection for PV Systems

What is best for your setup??? Generally, the less expensive MSW inverters only allow you to ground the electrical system in one place--Typically the negative battery bus to earth/safety ground. If you try to "ground the neutral" like the NEC does for homes in North America to the same safety ground--It will generally toast the MSW inverter the first time it is turned on.

And, with most TSW inverters, you can ground the DC side to the ground rod, and also "bond the 120/240 VAC neutral" to the same ground rod just fine. Will this be a more "lightning resistant" setup? Don't know.. A bolt that has just traveled miles through the air is not going to care much about a 1/4" insulation gap somewhere in your inverter.

Note: As always, read the instruction manuals, there are exceptions to every rule of thumb.

Read about grounding a system... The biggest issue (from my humble opinion) is when you have grounds that are separated by distance--Say you have a solar array 100' away from the battery shed/home... If you put a ground in at the array and another ground at the home--you can inject current into your wiring from ground (strike near array raises the ground voltage at the array ground--and sends some of the strike energy down the grounded wires into the shed/home which then flows to the local ground).

Generally, it is better to use the same (single) ground point for all equipment. If you have to drive a bunch of rods... Wire them all to a central rod and run all electrical grounds to that one rod (center of a star type grounding).

-Bill

I read all of your linked articles, thanks for those! It does seem like there are two different schools of thought on grounding, and as you said, there's nothing that is lightning proof.

I am not convinced that with thousands of volts of electricity hitting your building that a #4 copper wire is going to be sufficient to carry the electricity off the roof (especially in our case, as our roof is metal). I am wondering if a piece of 1" rebar going up to the roof, or something like that, would work better. Just thinking out loud here. I have even thought about putting insulators between the solar panels and the mounting brackets and roof, with the idea that if lightning hit the roof, it would be less likely to go out into the solar panels, and more likely to go down the lightning rod. Hopefully, if it actually hit one of the panels, it would only burn that one up. Again, just thoughts.

I have been looking at the Magnum Energy MS4024PAE 4000 Watt Sine Wave inverter 120/240 Volt or the 48 volt unit. I'm trying to keep the need for communications between the controlers and inverters as simple as possible. Any thoughts on the Magnums?

Thanks again for all your help with this!

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

Cariboocoot wrote: »

This is the inverter I use personally. It's excellent, but ... costs money. Especially as you need a MATE controller to program it with, which is extra cost. To really do a good OB system, you need a HUB and the wires so that all the pieces (including the FM80's) "talk" to each other and share data regarding battery state and set points and temperature. The standby current on the OB is a bit high; mine uses roughly 20 Watts when it's doing nothing. The other issue is your maximum draw at any one time; if it is likely to be over 3 kW then you may want to double up on inverters, as 3.5 kW is a tad "optimistic" output. A second OB inverter can be stacked to add capacity, and it will sit idle until needed. But at roughly $2,000 each ... plan carefully!

I think I'd go with some type of true sine wave inverter if only for the motors. Look at the Magnum line up as well: http://store.solar-electric.com/maensiwainac.html You can get a 4 kW unit for about the same money as the 3.5 OB.

I took a look at the Magnums - I like the idea of keeping the units separated, even if they are a bit less efficient. Thanks for your help.

BB. · September 2010

Re: New off-grid home in Honduras - could use some advice

Actually, a 1" rebar is one of the worst ways of addressing lightning connections...

Two issues (that I know of)--One is that lightning is a relatively high frequency wave front (nominally around 10kHz or higher)--and the energy tends to flow in the "skin" of the conductor (all that current moving in the same direction forces the electrons to the skin of the wire). If you look for real lightning cable--you will see that is a bunch of strands "woven" together so that there is a lot of surface area for the current to flow.

The second is that Iron (and other ferrous metals) are highly inductive (because of their magnetic properties). This reduces the current flow (increases impedance/"resistance") and can force the lightning to find other paths.

You need to look at lightning as "Radio Frequency Energy"... Those rules are quite a bit different than that for large DC currents.

HAM sites (amateur radio) webs sites and look at their lightning protection can be very educational.

-Bill

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

BB. wrote: »

Actually, a 1" rebar is one of the worst ways of addressing lightning connections...

Two issues (that I know of)--One is that lightning is a relatively high frequency wave front (nominally around 10kHz or higher)--and the energy tends to flow in the "skin" of the conductor (all that current moving in the same direction forces the electrons to the skin of the wire). If you look for real lightning cable--you will see that is a bunch of strands "woven" together so that there is a lot of surface area for the current to flow.

The second is that Iron (and other ferrous metals) are highly inductive (because of their magnetic properties). This reduces the current flow (increases impedance/"resistance") and can force the lightning to find other paths.

You need to look at lightning as "Radio Frequency Energy"... Those rules are quite a bit different than that for large DC currents.

HAM sites (amateur radio) webs sites and look at their lightning protection can be very educational.

-Bill

Well, I was pretty sure the 1" rebar wasn't the best idea. I'm just always looking for available (to me) options. Would multiple strands of #6 solid copper wire work? Or we can also get #2 and #4 welding line, which would give it a lot of surface but it would be insulated, and I'd be afraid that lightning would just burn it right up. Also we can get aluminum relatively cheap, but again I'd be afraid it couldn't take the strike.

Thanks again.

Simple Guy · September 2010

Re: New off-grid home in Honduras - could use some advice

mike90045 wrote: »

There is another difference, power consumption. Motors and transformers of all types will consume about 20% more power on mod-square wave, than they do on pure sine. The extra power is a drain on your system, you 100 motor or cordless drill charger is now consuming 120W, and can overheat and die, or just drain your battery faster.

Draining the battery faster is not as important to me as the overheating and dying of the tools and equipment. I will certainly take this into consideration. What do you think of the Magnum Energy MS4024PAE 4000 Watt Sine Wave inverter 120/240 Volt?

Thanks for the input!

New off-grid home in Honduras - could use some advice

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