Going semi-off grid

grav80 · June 2014

Hi all, I'm new here and trying to learn as much as I can about living off grid.

I have a house which is situated in an area with lots of power failures so I have been thinking of getting a backup supply. I live in South Africa by the way. In the house we have the following appliances which would need to be powered:
10 x 14w bulbs (can't remember if these are LED or CCFL)
2 x CCFL tube lights
1 x washing machine twice a week
50" Plasma TV (I think it uses around 200-250w)
1 STB which uses about 40w
One small music system with 80w speaker (I don't know what else to use apart from speaker wattage

)
Then numerous smaller devices (phones, tablets, laptops)

The DB board has the following breakers:
Main Switch: 60a
Stove: 30a (going gas, so this can be ignored)
Geyser: 20a (might go for a thermosyphon)
Lights: 10a
2 x Plugs: 20a each.

I need advice on the following.

I can get my hands on some 102ah deep cycle batteries through a friend's business. I can then get 6 x 250w solar panels from somewhere else for not too much. After which I'll get an inverter and MPPT charge controller. I'm going to be getting these in stages, so once I'm done I'll start connecting things up.

1. I've been thinking of going with a 48v system, but I noticed the inverters are hellishly expensive for 48v systems, so I've been pondering about going down to 24v. Any idea why I shouldn't? I can probably save up a while longer and get a 48v inverter.

2. What's the sweet-spot in terms of number of batteries. I can probably get about 12 and then connect them up 3 rows of 4 batteries each to give 48v. Any advice would be appreciated.

3. What would my reserve power be with 12 batteries connected as above?

4. Would I be able to use an automatic transfer switch to switch over to the backup system in the event of a grid failure?

I'm gradually trying to move completely off the grid, but its a bit expensive

I'm hoping to have my conversion done within the next 12 months so wish me luck!

stephendv · June 2014

Re: Going semi-off grid

grav80 wrote: »

I can get my hands on some 102ah deep cycle batteries through a friend's business. I can then get 6 x 250w solar panels from somewhere else for not too much. After which I'll get an inverter and MPPT charge controller. I'm going to be getting these in stages, so once I'm done I'll start connecting things up.

1. I've been thinking of going with a 48v system, but I noticed the inverters are hellishly expensive for 48v systems, so I've been pondering about going down to 24v. Any idea why I shouldn't? I can probably save up a while longer and get a 48v inverter.

Howzit boet. A lot is going to depend on what you can live without during the power cut and how long the powercuts last. Can't imagine that the geyser (hot water tank) draws more than 3kW, but that's still a huge load to draw from batteries. 3kW at 48V = 62A and at 24V = 164A. This means that your 24v system would need really thick cables to handle that current. Also you can fit twice as many solar panels on a single MPPT controller on 48V than you can on 24v, since the controller's Amp rating is based on its output.
Good that you have a handle on the maximum power draw from the appliances, but you'll also need to know how much energy they use every day. E.g. How long does that 3kW (guessing) water heater stay on for in a 24 hour period?
Looking at that list, the water heater is by far the biggest consumer. If you can find an alternative to that you'd get by on a reasonably sized system, but to provide water heating from PV in winter will be very costly.

If your motivation is purely to see the home through power outages then a generator makes more sense, it can handle higher loads and will cost less. But if you want to get into Renewable Energy and this is the first step, then read on

grav80 wrote: »

2. What's the sweet-spot in terms of number of batteries. I can probably get about 12 and then connect them up 3 rows of 4 batteries each to give 48v. Any advice would be appreciated.

Depends on how long the power outages typically last and how much the batteries cost. Also too many parallel strings can lead to early battery death because of unequal charging (another reason why 48V is nicer in your case).

grav80 wrote: »

3. What would my reserve power be with 12 batteries connected as above?

102Ah deep cycle battery shouldn't be discharged more than 50%, so that's 51Ah useable at 12V = 612Wh x 12 batteries = 7.3kWh

grav80 wrote: »

4. Would I be able to use an automatic transfer switch to switch over to the backup system in the event of a grid failure?

Yes. Most of the off-grid inverters that have chargers built into them (called inverter/chargers), also have an automatic transfer switch built in. They'll switch over to batteries in less than 20ms which means that electronics keep running without interruption.

grav80 wrote: »

I'm gradually trying to move completely off the grid, but its a bit expensive I'm hoping to have my conversion done within the next 12 months so wish me luck!

Aha. My parents live in South Africa and as much as I love living off-grid, every time I run the numbers for them it just doesn't make sense because grid power is so cheap there. If you go 100% off-grid it means you'll need a generator and a large battery bank. But if you go for a hybrid system where you keep your grid connection but supplement your power with solar, then you can get by with a small battery bank and fewer panels.

If you're certain about going off-grid then the one component you must get right is the inverter/charger. This must be able to meet 100% of your loads or you should be prepared to watch your loads and only turn on high consumption devices at specific times. This is where the water heater throws everything out. If you look at all your other loads, you could get buy on a 3kW inverter or even less if you're careful about when you do the washing. But if you need to support water heater + washing machine + fridge at the same time then you're looking at a quality 5kW+ inverter.

Good luck!

TucsonAZ · June 2014

Re: Going semi-off grid

grav80 wrote: »

One small music system with 80w speaker (I don't know what else to use apart from speaker wattage )

1. I've been thinking of going with a 48v system, but I noticed the inverters are hellishly expensive for 48v systems, so I've been pondering about going down to 24v. Any idea why I shouldn't? I can probably save up a while longer and get a 48v inverter.

2. What's the sweet-spot in terms of number of batteries. I can probably get about 12 and then connect them up 3 rows of 4 batteries each to give 48v. Any advice would be appreciated.

3. What would my reserve power be with 12 batteries connected as above?

This is all I can really help you with with my knowledge base. My vintage Pioneer SX-535 which is under 25 watts per channel uses 35-40 watts while running depending on the volume. I'm not sure how that would compare to something more modern.

I would go with 48v at your panels and 24v for your battery bank if you're under 2,000kw of solar. I looked into this a lot and it's the sweet spot for that amount of solar, if you have no concerns about shading, you could go 72v with the panels into a 48v bank but again, for me cost is a factor that prevents that along with my application having shading issues that make 3 panels connected undesirable.

Batteries do best in series, I would do what you can to make that happen, twelve 12v batteries on a 48v (or 24v) system may cause some issues. If you could manage twelve 2v batteries you'd be in great shape. If you're getting them at a low cost however, that's a different story and you'll have room to experiment and see what works best for you.

You would end up with a battery bank able to supply 14,688 watt hours of power, of that 50% is usable without impacting the battery life. Even in ideal conditions your solar panels couldn't supply enough power to fully recharge that bank to 100% if you discharged to 50% so keep that in mind.

Also know that I hardly know what I'm talking about with this but I'm mostly getting the hang if it so trying to offer input where I can and as I go.

Good luck, I'm sure somebody will be along shortly to mind melt you with impressively technical data (:

grav80 · June 2014

Re: Going semi-off grid

TucsonAZ wrote: »

This is all I can really help you with with my knowledge base. My vintage Pioneer SX-535 which is under 25 watts per channel uses 35-40 watts while running depending on the volume. I'm not sure how that would compare to something more modern.

I would go with 48v at your panels and 24v for your battery bank if you're under 2,000kw of solar. I looked into this a lot and it's the sweet spot for that amount of solar, if you have no concerns about shading, you could go 72v with the panels into a 48v bank but again, for me cost is a factor that prevents that along with my application having shading issues that make 3 panels connected undesirable.

Batteries do best in series, I would do what you can to make that happen, twelve 12v batteries on a 48v (or 24v) system may cause some issues. If you could manage twelve 2v batteries you'd be in great shape. If you're getting them at a low cost however, that's a different story and you'll have room to experiment and see what works best for you.

You would end up with a battery bank able to supply 14,688 watt hours of power, of that 50% is usable without impacting the battery life. Even in ideal conditions your solar panels couldn't supply enough power to fully recharge that bank to 100% if you discharged to 50% so keep that in mind.

Also know that I hardly know what I'm talking about with this but I'm mostly getting the hang if it so trying to offer input where I can and as I go.

Good luck, I'm sure somebody will be along shortly to mind melt you with impressively technical data (:

Thanks for the feedback!

stephendv wrote: »

Howzit boet. A lot is going to depend on what you can live without during the power cut and how long the powercuts last. Can't imagine that the geyser (hot water tank) draws more than 3kW, but that's still a huge load to draw from batteries. 3kW at 48V = 62A and at 24V = 164A. This means that your 24v system would need really thick cables to handle that current. Also you can fit twice as many solar panels on a single MPPT controller on 48V than you can on 24v, since the controller's Amp rating is based on its output.
Good that you have a handle on the maximum power draw from the appliances, but you'll also need to know how much energy they use every day. E.g. How long does that 3kW (guessing) water heater stay on for in a 24 hour period?
Looking at that list, the water heater is by far the biggest consumer. If you can find an alternative to that you'd get by on a reasonably sized system, but to provide water heating from PV in winter will be very costly.

If your motivation is purely to see the home through power outages then a generator makes more sense, it can handle higher loads and will cost less. But if you want to get into Renewable Energy and this is the first step, then read on

Depends on how long the power outages typically last and how much the batteries cost. Also too many parallel strings can lead to early battery death because of unequal charging (another reason why 48V is nicer in your case).

102Ah deep cycle battery shouldn't be discharged more than 50%, so that's 51Ah useable at 12V = 612Wh x 12 batteries = 7.3kWh

Yes. Most of the off-grid inverters that have chargers built into them (called inverter/chargers), also have an automatic transfer switch built in. They'll switch over to batteries in less than 20ms which means that electronics keep running without interruption.

Aha. My parents live in South Africa and as much as I love living off-grid, every time I run the numbers for them it just doesn't make sense because grid power is so cheap there. If you go 100% off-grid it means you'll need a generator and a large battery bank. But if you go for a hybrid system where you keep your grid connection but supplement your power with solar, then you can get by with a small battery bank and fewer panels.

If you're certain about going off-grid then the one component you must get right is the inverter/charger. This must be able to meet 100% of your loads or you should be prepared to watch your loads and only turn on high consumption devices at specific times. This is where the water heater throws everything out. If you look at all your other loads, you could get buy on a 3kW inverter or even less if you're careful about when you do the washing. But if you need to support water heater + washing machine + fridge at the same time then you're looking at a quality 5kW+ inverter.

Good luck!

Howzit!

Thanks so much for this.

What I forgot to make clearer was the water heater issue. I merely mentioned it because its also on the DB board and thought that you guys might need that information. I'm going solar with that as well, however I'm still doing research as I do not know nearly enough about the subject

So for all intents and purposes lets forget about its existence and ignore it from calculations.

grav80 · June 2014

Re: Going semi-off grid

I should also add: Rethinking about my ultimate goal, I'd want the devices to run off solar, but still have the ability to flip a switch (or automatically have it switched) when I run out of solar power to be connected to the grid.

stephendv · June 2014

Re: Going semi-off grid

grav80 wrote: »

I should also add: Rethinking about my ultimate goal, I'd want the devices to run off solar, but still have the ability to flip a switch (or automatically have it switched) when I run out of solar power to be connected to the grid.

Yep, this can be automated in most of the quality inverter/charger units. Most can be programmed to connect the grid when:
a) the batteries are low
b) you're drawing too much current

Both those limits can be programmed too of course. As an example the Victron multiplus rated at 800W has an internal transfer switch of 16A, so if it can't handle the load it can call on the grid to deliver 3.6kW through the transfer switch (actually it can boost the grid and deliver 4.4kW, but that's another topic).

This leaflet explains backup system like this quite nicely: http://www.studer-inno.com/upload/folders/2502.pdf

vtmaps · June 2014

Re: Going semi-off grid

grav80 wrote: »

I'm going to be getting these in stages, so once I'm done I'll start connecting things up.

Here's some very important advice: Don't buy the batteries until you are completely ready to charge them. They do not keep well.

Since you indicated that you will not be using an electric hot water heater, you should be fine with a 24 volt system.

Regarding the batteries, you would be better off if you can find some larger batteries. Larger batteries means fewer batteries, and fewer batteries means fewer points of failure, in the batteries themselves, and in all of the connections. As has been mentioned, avoid parallel batteries. And as has also been mentioned, if you need two strings of batteries at 24 volts, you would get the same energy storage with one string of the batteries at 48 volts.

--vtMaps

stmar · June 2014

Re: Going semi-off grid

As most of you probably do, I read these posts to gain knowledge. I went to the pdf posted by stephen (This leaflet explains backup system like this quite nicely: http://www.studer-inno.com/upload/folders/2502.pdf) and they reference "priority voltage" along with float. This is the first I have heard of that term and I could not find a definition in my searches. Anyone know what priority voltage means?

BB. · June 2014

Re: Going semi-off grid

It appears the Priority Voltage is what we call the "Sell" voltage on this side of the pond.

It is the voltage that the AC inverter uses to decide when to pull power/current from the battery bank to support the AC loads (or "sell to the grid" if GT/Hybrid type inverter and "sell" is enabled).

The solar/wind charge controllers are set higher than the Sell/Priority voltage--So they are always pumping energy into the battery bank "system" and the AC inverter is skimming power off the top like a "dump" load.

This ensures that the batteries have enough charge (>80% of capacity) to operate in off grid/backup mode if the AC mains fail.

-Bill

stmar · June 2014

Re: Going semi-off grid

Thanks for clearing that up. With these systems you don't want to miss something; be it opportunity or necessary action.

grav80 · July 2014

Re: Going semi-off grid

Sorry for the haitus, folks. Didn't have internet for a while (long story).

Just on the parallel vs series issue quickly: I did some research, but can't really find any info on this, would you guys mind explaining? If I were to go for a 2 rows of 24v (12*2v (series)) in parallel would be better than 2 rows of 2*12v? Its a silly question, but I feel I need to understand that before I dive into this

It might be the one thing that's going to be a stumbling block because looking at the 2v or even 6v battery prices, its going to be a bit tight

stephendv · July 2014

Re: Going semi-off grid

grav80 wrote: »

Just on the parallel vs series issue quickly: I did some research, but can't really find any info on this, would you guys mind explaining? If I were to go for a 2 rows of 24v (12*2v (series)) in parallel would be better than 2 rows of 2*12v? Its a silly question, but I feel I need to understand that before I dive into this

The best is plain series, then the least number of rows possible.

grav80 wrote: »

It might be the one thing that's going to be a stumbling block because looking at the 2v or even 6v battery prices, its going to be a bit tight

Check that you're comparing like for like. Batteries are rated based on the number of cycles at a particular depth of discharge (DoD). A 2V cell rated at 1500 cycles, 80% DoD that costs $100, would mean $300 for a 6V battery. But a 6V block rated at 400 cycles at 80% DoD might only cost $150. Comparing the two, although the 6V block is half the price, it will last only 30% as long as the 2V cell- so although the initial outlay for the 2V is more, in the long run its better value for money.

vtmaps · July 2014

Re: Going semi-off grid

grav80 wrote: »

Just on the parallel vs series issue quickly: I did some research, but can't really find any info on this, would you guys mind explaining?

The basic problem with parallel batteries is that while charging them it is difficult to get the current to divide equally among the parallel paths.

Short discussion here: http://www.wind-sun.com/ForumVB/showthread.php?14674

--vtMaps

Blackcherry04 · July 2014

Re: Going semi-off grid

stephendv wrote: »

The best is plain series, then the least number of rows possible.

Check that you're comparing like for like. Batteries are rated based on the number of cycles at a particular depth of discharge (DoD). A 2V cell rated at 1500 cycles, 80% DoD that costs $100, would mean $300 for a 6V battery. But a 6V block rated at 400 cycles at 80% DoD might only cost $150. Comparing the two, although the 6V block is half the price, it will last only 30% as long as the 2V cell- so although the initial outlay for the 2V is more, in the long run its better value for money.

The only problem with this theory is that the 30% is something you pulled out of the air. The cost of 2 V cells is more like 2.5 times more than 6 V cells.

stephendv · July 2014

Re: Going semi-off grid

Blackcherry04 wrote: »

The only problem with this theory is that the 30% is something you pulled out of the air

Hehe, yes I may even have pulled it out of some other place

The numbers are just an example so that the OP compares prices based on the rated cycles.

Here's a concrete example of prices for different batteries from the same distributor on this side of the pond for comparison:
- 6V 250Ah (c5) Battery with 675 cycles @ 80% DoD goes for 188 Euros, so that works out to 0.27 Euros/cycle
- 2V 250Ah battery with 1500 cycles @ 80% DoD goes for 80 Euros per cell, need 3 of those for a 6V battery = 240 Euros and converted to a per cycle cost is 0.16 Euros/cycle

So the 2V come out at almost half the cost. The comparison is not quite fair since they're from two different manufacturers though. Anyway, point is to compare batts of the same capacity and at a per-cycle cost to get a good reflection of the lifetime costs.

Cariboocoot · July 2014

Re: Going semi-off grid

You've got some good prices there.

Over here: same size battery bank (700 Amp hours @ 12 Volts) with same technology (no difference in cycle life indicated) from same manufacturer; in 6 Volt units is $1,376, in 2 Volt units is $4,038. That's 3X the cost for identical capacity, and does not include the eco-fee difference between four 6 Volt and six 2 Volt - never mind the taxes.

We also wouldn't draw these down to 80% DOD. Did you mean 80% SOC?

stephendv · July 2014

Re: Going semi-off grid

Ouch on the prices. BTW, those I listed are also excluding 21% taxes.

Cariboocoot wrote: »

We also wouldn't draw these down to 80% DOD. Did you mean 80% SOC?

Yeah, not going to draw them down to that, that is just the standard rating used by manufacturers. It's also an IEC standard for measuring battery life: IEC 61427:2005-05

BB. · July 2014

Re: Going semi-off grid

stephendv wrote: »

Here's a concrete example of prices for different batteries from the same distributor on this side of the pond for comparison:
- 6V 250Ah (c5) Battery with 675 cycles @ 80% DoD goes for 188 Euros, so that works out to 0.27 Euros/cycle
- 2V 250Ah battery with 1500 cycles @ 80% DoD goes for 80 Euros per cell, need 3 of those for a 6V battery = 240 Euros and converted to a per cycle cost is 0.16 Euros/cycle

So the 2V come out at almost half the cost. The comparison is not quite fair since they're from two different manufacturers though. Anyway, point is to compare batts of the same capacity and at a per-cycle cost to get a good reflection of the lifetime costs.

Is there an AH conversion issue here (i.e. 6 volt at 250 AH vs 2 volt at 750 AH)--Otherwise, the 2 volt 250 AH battery is ~1/3rd the weight and 1/3rd the energy storage of the 6 volt 250 AH battery--And for cycling the same amount of energy (volts*amps*hours), the 3x 2 volt batteries (same amount of energy as the 6 volt example) would cost 0.48 Euro per cycle vs the 0.27 E/cycle of the 6 volt.

-Bill

stephendv · July 2014

Re: Going semi-off grid

BB. wrote: »

Is there an AH conversion issue here (i.e. 6 volt at 250 AH vs 2 volt at 750 AH)

Don't think there's a conversion issue I multiplied the cost of the 2V by 3 to make it a 6V battery, i.e. compared 6V 250Ah with a 3 x 2V 250Ah.

BB. · July 2014

Re: Going semi-off grid

OK... That makes sense. You did convert to 6 volt "bank" of 2 volt cells.

-Bill

drraptor · July 2014

Re: Going semi-off grid

so you guys recommend comparing batteries prices as Currency(your local currency)/ cycle after you have equalized it to same AH and voltage ?

BB. · July 2014

Re: Going semi-off grid

It is easier to do the calculations in Watt*Hours/$$$ or $$$/Watt*Hours...

Example:

Trojan T105-RE 6 Volt, 225 AH Deep Cycle Battery $174.00

6 volt * 225 AH / $174 = 7.76 WH/$

Concord 12 volt 108 AH (at 24 hour rate, usually we use 20 hour rate):

[TH="class: style2, align: center"] PVX-1080T[/TH]
12
86
97
108

12 volts * 108 AH / $229.95 = 5.64 WH/$

Now--If you can find the cycle life for each battery and how many years of life--You can take that into account.. A battery that has 2x cycle life will be less costly per cycle. Or one that last 2x longer (aging), will cost less to have in service.

For the Trojan:

http://passiontech.com.au/index.php/energy-solutions-shop/product/1061-trojan-225ah-c20-6v-battery-t-105-re-made-in-usa/category_pathway-68

In the flooded type of lead acid batteries, Trojan manufacture 3 models of batteries:
Industrial Line: designed for 1500 cycles at 80% DOD (Depth of Discharge), or 2800 cycles at 50% DOD

Premium Line: designed for 1600 cycles at 50% DOD

Signature Line: designed for 1200 cycles at 50% DOD

The T-105-RE battery belongs to the Premium Line category, and presents excellent value for money. It is a quality product manufactured in the USA. It is a 6V battery, so can be easily connected in series to assemble into a 12V, 24V or 48V battery bank. When fitted with the optional Trojan HydroLink watering system, the electrolyte level of every cell in the battery bank can be topped up to the correct level in under a minute, vastly reducing maintenance time.

6 volt * 225 AH * 1,600 cycles / $174 = 12,400 WH total /$ = 12.4 kWH total energy per $

For Concorde, page 40 for cycle life vs discharge:

http://www.solar-electric.com/lib/wind-sun/techmanual.pdf

50% discharge 1,000 cycles

12 volts * 108 AH * 1,000 cycles / $229.95 = 5,640 WH total /$ = 5.64 kWH total energy per $

Not picking on any brand/model of battery--Just using two examples from what specifications I could find. Not even claiming that the above numbers are correct (I try, but always "trust but verify").

Other things will affect life such as average battery temperatures, how they are charged/discharged, etc...

-Bill

drraptor · July 2014

Re: Going semi-off grid

Watt*hours Wh remain same over the life of the battery ? :-)

I can't find the data sheet for crown batteries.

BB. · July 2014

Re: Going semi-off grid

It does depend what life is. ... battery with 80% capacity or with 50% remaining capacity.

If you are trying for life cycle cost, then both above should be multiplied by 0.5 times as this only used 50% capacity for this life cycle cost. Or 2x the costs I calculated above.

-Bill

Cariboocoot · July 2014

Re: Going semi-off grid

drraptor wrote: »

Watt*hours Wh remain same over the life of the battery ? :-)

I can't find the data sheet for crown batteries.

No, Watt hours do not remain the same over the life of a battery.

However that is irrelevant when comparing batteries for purchase as all batteries will go down in capacity over time.

What you have to look for is the difference in price between comparable Watt hours with similar cycle life. That last bit of data can be hard to find. For the most part batteries of the same technology will have the same cycle life and so can be compared directly.

Some manufacturers will claim more cycle life for their technology. Take these claims with a grain of salt as you probably won't see them stepping up to guarantee those claims: "1,500 cycles to 50% DOD or your money back!" I've never seen it at least.

I have heard a lot of explanations why the dead batteries aren't the company's fault, and most of the time that is true. A couple of times it wasn't.

drraptor · July 2014

Re: Going semi-off grid

BB. wrote: »

It does depend what life is. ... battery with 80% capacity or with 50% remaining capacity.

If you are trying for life cycle cost, then both above should be multiplied by 0.5 times as this only used 50% capacity for this life cycle cost. Or 2x the costs I calculated above.

-Bill

Most of the off grid system are designed with 50% DOD and with occasional 80%DOD or deeper cycle ?

you mean

Trojan 105-RE @ 50% DOD will cost
6 * 225 * 2800/174 = 21 KWh total energy per $

while Concord 12 volt 108 AH @ 80% DOD will cost

12 * 108 * 600 / 229.95 = 3.81 KWh total energy per $

Cariboocoot · July 2014

Re: Going semi-off grid

drraptor wrote: »

Most of the off grid system are designed with 50% DOD and with occasional 80%DOD or deeper cycle ?

you mean

Trojan 105-RE @ 50% DOD will cost
6 * 225 * 2800/174 = 21 KWh total energy per $

while Concord 12 volt 108 AH @ 80% DOD will cost

12 * 108 * 600 / 229.95 = 3.81 KWh total energy per $

More like most of the time it's 25% DOD which is 75% SOC with an occasional dip to 50% DOD which is 50% SOC. It can really mess up the calculations if you get these reciprocal functions reversed.

Then there are forklift batteries which really can take 80% DOD making their real Watt hour capacity greater than the equivalent rating in a standard FLA.

Not to mention different battery chemistries like LiFePo and NiFe which have similar greater discharge ability.

drraptor · July 2014

Re: Going semi-off grid

Cariboocoot wrote: »

No, Watt hours do not remain the same over the life of a battery.

However that is irrelevant when comparing batteries for purchase as all batteries will go down in capacity over time.

What you have to look for is the difference in price between comparable Watt hours with similar cycle life. That last bit of data can be hard to find. For the most part batteries of the same technology will have the same cycle life and so can be compared directly.

Some manufacturers will claim more cycle life for their technology. Take these claims with a grain of salt as you probably won't see them stepping up to guarantee those claims: "1,500 cycles to 50% DOD or your money back!" I've never seen it at least.

I have heard a lot of explanations why the dead batteries aren't the company's fault, and most of the time that is true. A couple of times it wasn't.

VRLA vs FLA which one will last longer at the same DOD, with charging and discharging according to the manufacturer's instructions.

Cariboocoot · July 2014

Re: Going semi-off grid

drraptor wrote: »

VRLA vs FLA which one will last longer at the same DOD, with charging and discharging according to the manufacturer's instructions.

Well if you're talking AGM vs. FLA (it is possible to have FLA that's valve regulated) the FLA will outlast the AGM. They are very tolerant batteries.

The thing is the AGM's other qualities (no gassing, safe transport, higher current) makes the two not exactly 100% interchangeable.

If you mean strictly sealed FLA vs. non-sealed it would be a pretty close tie for lifespan with possible extra time on the sealed battery as there would be less environment-induce acid loss. But again the open batteries are more forgiving of mistakes.

BB. · July 2014

Re: Going semi-off grid

Pick your numbers and the model that makes sense to you. And then your kids kill the bank when they visit for the summer.

-Bill

Cariboocoot · July 2014

Re: Going semi-off grid

BB. wrote: »

Pick your numbers and the model that makes sense to you. And then your kids kill the bank when they visit for the summer.

-Bill

No truer words have ever been spoken!

Going semi-off grid

Comments

Categories