First build - input appreciated!

photon_trap · October 2012

Hi, After what seems like a zillion hours of research in a topic I was previously unfamiliar with (I'm a mechanic by trade) I have what I think I need on paper.
My plan is to operate the 110v side of my two car garage essentially off grid (although I do have 110/240v service) reducing my electric bill (hopefully enough to get my bill into a lower tier) and, most importantly have backup power source for emergency use.

The system is based on 1.5Kwh per day energy usage (in reality this a considerable over-estimate) so, for my areas worst case insolation of 2.72, I should require 551 watts of panel.
I plan on two 315w Kyocera totaling 630w and Morningstar Tri-Star 45 mppt charge controller (24v system)

I have purchased four Crown 6V 395ah batteries to be wired in series for 24v (9480wh) After 80% efficiency loss and assuming 50% DOD this should yield 3792wh if my calculations are correct.

I also have planned on a Exeltech XP-1100 24v inverter

I have a like new Honda eu200i generator that can be used to augment my solar input as needed -
I have not concluded the best way to equalize my batteries however. Will the panels be of sufficient output or will a 110 charger be needed?

Any educated comments and/or suggestions are very much appreciated as I sure don't want to have any do-overs ($$)

Thanks
Jeff A

Cariboocoot · October 2012

Re: First build - input appreciated!

Methinks you made a small calculation error on sizing the array. To get 1500 Watt hours AC per day from a battery-based system you have to put up with the inefficiency of going from array * time to AC out * time. It's a horrible little number around 0.52 and it works like this:

551 Watts of panel * 2.72 hours of sun * 0.52 = 779 Watt hours AC, or roughly half what you want. Work it backwards and you get 1500 Watt hours AC / 0.52 / 2.72 = 1060 Watts of panel.

Furthermore, 551 Watts of panel won't do much for 395 Amp hours of 24 Volt battery. Try this: 39 Amps * 24 Volts / 0.77 = 1215 Watt array.

The batteries @ 50% DOD would be good for about 4.2 kW hours AC, but do you really want to take them that low? For an occasional use system it's fine. For every day you'd want to reduce the DOD.

Likewise you can shrink your array to get away with a 5% charge rate. This will work for emergency power, but not suitable for every day if you have loads drawing while you're trying to recharge.

As far as the electric bill is concerned, it may lower it but will it save you money? Your off-grid power bill is going to be in the $1 per kW hour neighborhood. How much does the utility charge?

The Honda for emergency back-up power is probably a much better deal.

photon_trap · October 2012

Re: First build - input appreciated!

Thanks! This is why I am asking. So, I will plan on more panel and.....

>551 Watts of panel won't do much for 395 Amp hours of 24 Volt battery. Try this: 39 Amps * 24 Volts / 0.77 = 1215 Watt array.
What is the .77 value? Is it an efficiency value? I have read (and was perhaps mislead) by charge controller Mfg. claims of 99% efficiency. Is this a trickeration of wording?

In actual day to day usage my garage sees little consumption during the week with considerably elevated levels on weekends and as I said I have grid power available.
Lowering my electric bill ranks a distant second in goals - I should have mentioned that

Thanks

Cariboocoot · October 2012

Re: First build - input appreciated!

The 0.77 number is an over-all efficiency of panels + MPPT type controller. In other words a 200 Watt panel will actually produce and average output of 154 Watts from the controller over the hours of good sun.

The controller may have an efficiency rating of 99%, but that is not the whole story. It will vary depending on system design and operation. For instance the greater the difference between the array Voltage and the system (battery) Voltage the less efficient the controller will be.

Since this is basically an experimental system (with both grid and generator available should either be needed) you could use the lower 5% minimum charge rate and get away with a smaller array. The trouble is those 395 Amp hour batteries you've picked will be L16 size, and they will last longer with a 10% peak rate.

To that end, why not go for the more economical golf cart size batteries? With 220 Amp hours @ 24 Volts and 50% DOD you'd have roughly 2kW hours AC to work with; more than your desired 1.5 kW hours. These batteries are typically less expensive than the L16's (even for an equivalent amount of power) and you could recharge with a smaller array of about 685 Watts.

niel · October 2012

Re: First build - input appreciated!

i totally agree with coot and otherwise you would need to about double the number of pvs. you did not mention the inverter you plan to use. there are inverters that can be battery backed and also can sell to the grid.

Photowhit · October 2012

Re: First build - input appreciated!

I like the idea of going with golf cart batteries the first time out, Sams club and Costco usually have these around $80 + core/swap. It makes for very good $ per Ah.

You have been reading here? and you do understand that you'll loose another 20% or so through your system, battery and inverter ineffeciencies. So if you want a usable "1.5Kwh per day energy usage" you'll need to generate 2x that with a complete system losses of close to 50%.

vtmaps · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

I have a like new Honda eu200i generator that can be used to augment my solar input as needed -
I have not concluded the best way to equalize my batteries however. Will the panels be of sufficient output or will a 110 charger be needed?

You will need a 110 volt AC powered battery charger to augment your solar. Do you know about Power Factor? It will be an important consideration in selecting a battery charger for your Honda. Read this thread (long, but worthwhile):
http://forum.solar-electric.com/showthread.php?10123

--vtMaps

photon_trap · October 2012

Re: First build - input appreciated!

Thanks again all, I will read on the battery charger / power factor and, the 395ah batteries are already in my possession so they will be used. I am thinking perhaps the battery charger, either generator or grid powered depending on the situation may be helpful with a modest increase in panel may work (?)
How, in terms of charging cycle would that work? Meaning if the batteries are under charge from the solar charge controller and I introduce current from an independent (smart) charger like an Iota, would they be so smart as to realize what the other is doing or....? I am also unsure the little Honda will suffice in terms of output for this application - I have reading to do!

If anyone can suggest other good sources of information please relay them - I see myself as just coming to grips with the big picture in terms of efficiency (or inefficiency)

Jeff

stephendv · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

Thanks again all, I will read on the battery charger / power factor and, the 395ah batteries are already in my possession so they will be used. I am thinking perhaps the battery charger, either generator or grid powered depending on the situation may be helpful with a modest increase in panel may work (?)

Usually grid is easier and cheaper than generator, also less noisy

If you haven't yet bought the the inverter then consider getting a combined inverter/charger unit like the Magnum or outback inverter/chargers. It works out cheaper to buy an integrated unit than a separate charger and inverter. Another nice feature of the combined unit is that it gives you a built in automated transfer between grid power and battery power. So it can be programmed that if the battery voltage drops to X, then throw the switch and run on grid power and at the same time charge the batteries. Then once batteries are charged, throw the switch again to run off the batts. All this automatically and without interrupting the power to your loads.

Cariboocoot · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

Thanks again all, I will read on the battery charger / power factor and, the 395ah batteries are already in my possession so they will be used. I am thinking perhaps the battery charger, either generator or grid powered depending on the situation may be helpful with a modest increase in panel may work (?)
How, in terms of charging cycle would that work? Meaning if the batteries are under charge from the solar charge controller and I introduce current from an independent (smart) charger like an Iota, would they be so smart as to realize what the other is doing or....? I am also unsure the little Honda will suffice in terms of output for this application - I have reading to do!

If anyone can suggest other good sources of information please relay them - I see myself as just coming to grips with the big picture in terms of efficiency (or inefficiency)

Jeff

Do not worry about using two charge sources at the same time. This question comes up a lot: it's a non-issue. They will not 'interfere' with each other.

The Honda EU2000i will work fine. It's capable of 1600 Watts, and even without a power factor corrected charger can handle the job. You're only asking for 960 Watts for full charging, and even with a poor PF that's below the gen's maximum (less than 1200). If the gen has to carry loads at the same time it could be slightly problematic, but you should be able to keep loads off until the Bulk charging stage is done and the charging power need reduced.

Frankly and in all modesty there is no better source of information about solar electric power systems than this forum. And no I do not work for NAWS and neither do any of the other moderators.

BB. · October 2012

Re: First build - input appreciated!

There is this thread where we have a ton of information/links/etc. to care of solar systems, projects, books, other websites around solar/renewable energy/conservation.

It may be reorganized someday (yea, right), lots of random posts in no particular order right now.

-Bill

photon_trap · October 2012

Re: First build - input appreciated!

Cariboocoot wrote: »

Do not worry about using two charge sources at the same time. This question comes up a lot: it's a non-issue. They will not 'interfere' with each other.

The Honda EU2000i will work fine. It's capable of 1600 Watts, and even without a power factor corrected charger can handle the job. You're only asking for 960 Watts for full charging, and even with a poor PF that's below the gen's maximum (less than 1200). If the gen has to carry loads at the same time it could be slightly problematic, but you should be able to keep loads off until the Bulk charging stage is done and the charging power need reduced.

Thanks,
I will certainly take your word on the dual charger (non) issue alyhough it seems counter intuative to this wrench oriented individual (ha, like so much of the electrical world)
I read about the Mean Well charger in another post that was referenced - have there been furthur updates on it or another good charger to to use with the eu2000i?

I read about the

vtmaps · October 2012

Re: First build - input appreciated!

Cariboocoot wrote: »

Do not worry about using two charge sources at the same time. This question comes up a lot: it's a non-issue. They will not 'interfere' with each other.

I agree that the question comes up a lot. I disagree that its a non issue, at least during bulk charging.

During bulk stage of charging the sources of charging current will be additive. This may result in peak charge currents that are higher than safe.

My 24 volt system and the OP system have similar battery capacity. My solar array often pushes 30 amps into my batteries on a sunny (winter) morning. If I start up the generator to use some shop tools I have to remember to turn off the battery charger or the generator will push an additional 35 amps into my batteries. I do not want to be charging my batteries at 65 amps!

--vtMaps

Cariboocoot · October 2012

Re: First build - input appreciated!

vtmaps wrote: »

I agree that the question comes up a lot. I disagree that its a non issue, at least during bulk charging.

During bulk stage of charging the sources of charging current will be additive. This may result in peak charge currents that are higher than safe.

My 24 volt system and the OP system have similar battery capacity. My solar array often pushes 30 amps into my batteries on a sunny (winter) morning. If I start up the generator to use some shop tools I have to remember to turn off the battery charger or the generator will push an additional 35 amps into my batteries. I do not want to be charging my batteries at 65 amps!

--vtMaps

You have a flaw in your system.
The generator should not be permanently connected to the inverter's AC IN. You should always have it disconnected when starting or stopping the gen. Yes, I know autogen starts don't work that way but they are usually dedicated and will only start when the battery is low (no solar power available).
How you are coming up with a situation where both panels and charger can put out full current for more than a moment is beyond me. I run almost identical equipment and this never happens.

vtmaps · October 2012

Re: First build - input appreciated!

Cariboocoot wrote: »

How you are coming up with a situation where both panels and charger can put out full current for more than a moment is beyond me. I run almost identical equipment and this never happens.

My question is how do you avoid it? Perhaps you never run your generator when there is bright sun.

When the generator is on, if I start up a large AC load the Outback will respect the generator's limits and divert generator power from the charger to the AC load. If I start the generator and the phone rings before I start the load I will be pushing 65 amps into a 375 ah battery.

The Outback inverter/charger and the Outback charge controller can both be programed to limit their charging current. Despite Outback's famous integration, there is no way to regulate the total current into the batteries during bulk stage charging if you have both an Outback inverter/charger and an Outback charge controller.

--vtMaps

Cariboocoot · October 2012

Re: First build - input appreciated!

This is very odd. Both charge sources are regulated. If the batteries do not require high current they both 'back down'. It makes me suspect your inverter-charger isn't working right.

When mine is first energized the charge current is zero. It then ramps up to maximum, and falls back as the battery charges. The MX60 plays "second fiddle" to this and instantly drops current even if more is available from the panels. Mine are not connected by a HUB, btw; simply have the charge parameters set the same (5 Amp AC limit on the inverter-charger which is about 25 Amps DC, panels free to put out whatever they can).

I have run both in bright sun: the MX60 just throttles back. I'd hate to think there's a flaw in the FM60 that won't let it respond properly. Or that something is wrong with your 3524 and its charger isn't adjusting properly. What Voltage are you reading on the batteries when this happens? If its above Absorb there shouldn't be any possibility of this psychotic current flow.

vtmaps · October 2012

Re: First build - input appreciated!

Cariboocoot wrote: »

What Voltage are you reading on the batteries when this happens? If its above Absorb there shouldn't be any possibility of this psychotic current flow.

Nothing wrong with the equipment. Your system works the same way and will do the same thing. The current flow is not psychotic. As I mentioned, this only occurs during bulk charging and it stops and regulates as soon as absorb voltage is reached. During bulk stage the charge controller will put out all the amps it can. During bulk stage the inverter/charger will put out all the amps that I allow it to (by programming). Outback does not have a solution.

--vtMaps

Cariboocoot · October 2012

Re: First build - input appreciated!

Well I've never still been in Bulk by the time the sun is full on the panels. Normally by then most of the charging is done, one way or another.

And you're 100% correct that there is no co-ordination of charge between the SCC's and the inverter-charger. This has only been a problem for me because you can't use End Amps on the AC charge, which is where you need it most! Who wants to run even an inverter-generator to squeeze out that last 10%?

Right now my panels are down while I replace the roofing underneath. When I get them back up I'll see about experimenting with this a bit. Providing there's still sun then; nothing but rain turning to snow in the forecast now! :grr

inetdog · October 2012

Re: First build - input appreciated!

Cariboocoot wrote: »

This is very odd. Both charge sources are regulated. If the batteries do not require high current they both 'back down'. It makes me suspect your inverter-charger isn't working right.

When mine is first energized the charge current is zero. It then ramps up to maximum, and falls back as the battery charges. The MX60 plays "second fiddle" to this and instantly drops current even if more is available from the panels. Mine are not connected by a HUB, btw; simply have the charge parameters set the same (5 Amp AC limit on the inverter-charger which is about 25 Amps DC, panels free to put out whatever they can).

I have run both in bright sun: the MX60 just throttles back. I'd hate to think there's a flaw in the FM60 that won't let it respond properly. Or that something is wrong with your 3524 and its charger isn't adjusting properly. What Voltage are you reading on the batteries when this happens? If its above Absorb there shouldn't be any possibility of this psychotic current flow.

Leaving aside any "psychotic current flow", the issue remains that, as vtmaps pointed out, when both chargers are in Bulk mode, they will each be trying to deliver a constant current, and the result will be that as long as the voltage does not rise to the Absorb setting of either CC, they will know nothing about the current that the other CC is supplying.
If they both somehow looked at the battery current via a shared external shunt, then they could coordinate. But if they are each only measuring the current that they are supplying, then the batteries will potentially be getting double current.

What you describe, of the current ramping down as the battery charges, indicates that you are looking at the Absorb stage.

Now with either FLA or AGM, as long as the battery temperature is being monitored by each CC, there may not be any harm done to the batteries by this high rate Bulk stage, but if the output of one CC comes close to the safe maximum charge current of the bank, then there can be a problem.

The other side of this coordination conundrum is that, unless an external shunt is used, the CC has no idea how much of that current is going to the bank and how much is going to a load. So limiting the current to what is safe for the batteries can waste power. This problem does not occur with an inverter-charger alone, because it will either be charging or inverting, not both.

In both cases, the problem only occurs during the Bulk stage. Once a voltage-regulated charging stage, either Absorb or Float, is reached by either CC the two CCs will indeed coordinate, and if there is an external load the current output of either CC will rise to keep the battery seeing the Absorb voltage.
That suggests that a possible partial solution is to set the Absorb voltage lower than the standard value on only one of the two CCs.

Cariboocoot · October 2012

Re: First build - input appreciated!

Inetdog you may have found the key: I do not use the RTS on the inverter-charger, only on the MX60. As such even though the Voltage set points are the same on each they do not both see the same Voltage from the battery at any given time due to one having the temp compensation. Most of the time the problem is solved by the sun angle, of course.

I'm still going to poke at this if I get the chance to see if there's not a more sure-fire solution for vtMaps. Something that does not involve $10,000 worth of external add-ons of course.

photon_trap · October 2012

Re: First build - input appreciated!

Ok, so now my biggest concern is an AC battery charger model I can operate from my Honda eu2000i or (more commonly)from grid power.

I have read the maximum charge rate s/b battery ah/8. This would put that number at just under 50 amps for my 395 ah 24v FLA battery bank.
Does this sound correct or is there a better ideal formula?
Do I need to alter it for 24v?

I have read on the Iota but see no reference to an equalizing feature. Are they lacking this?
Also, I am looking at Xantrex Trucharge 24v 30 a anyone have any experiences to share?

vtmaps · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

I have read the maximum charge rate s/b battery ah/8. This would put that number at just under 50 amps for my 395 ah 24v FLA battery bank.
Does this sound correct or is there a better ideal formula?
Do I need to alter it for 24v?

A lot depends on temperature. The higher the amps, the higher the battery temperature becomes. Don't let the batteries get too hot. Make sure you have a remote battery temp sensor. Higher temperatures mean the battery needs lower voltages. If the temp goes up and the voltage does not go down (due to temperature compensation) the battery will draw still more current and heat up more and draw more current and heat up more and (thermal runaway!).

photon_trap wrote: »

Also, I am looking at Xantrex Trucharge 24v 30 a anyone have any experiences to share?

I am also looking. I know that it does have an optional remote battery temp sensor and is power factor corrected. I think it was removed from the market for a few years but has recently been redesigned and reintroduced. I've never seen one and have not found any reviews of the unit.

--vtMaps

photon_trap · October 2012

Re: First build - input appreciated!

So, what rule do I use when choosing a charger? My current gen (eu2000i) has limitations but as I have been told should be sufficient (remember, it will most often be used on grid power but I want it to be within limits of my Gen in emergencies)
I am reading 10% of Batt ah is a good number, perhaps a starting point - That would mean ~40a which brings me to my next question, dose system voltage a consideration for this value? I have (4X 395ah @ 24v)
I understand the value of a Temp sensor

I'm kinda surprised there are not more choices... The Xantrex 24v 30a seems a bit smallish

Jeff

BB. · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

I am reading 10% of Batt ah is a good number, perhaps a starting point - That would mean ~40a which brings me to my next question, dose system voltage a consideration for this value? I have (4X 395ah @ 24v)

Yes, voltages matter a lot... Remember Power=Volts*Amps ... So, if you have 40 amps charging a 24 volt bank, that is 2x the amount of wattage as 40 amps into a 12 volt bank.

For example, if you use a non-power factor corrrected power supply, here is the calculations I use to estimate AC power needs (if power factor corrected power supply, you can use 0.95 instead):

40 amps * 29 volts charging * 1/0.80 charger eff * 1/0.67 PF = 2.417 VA

Note, Power is Watts, but with AC, when you have Voltage Sine Wave and a current waveform that may be non-sine wave and/or out of phase with respect to voltage, the amount of current required is larger (1/0.67 in above example means ~1.49x as much current).

Generators are rated both in Watt output and VA (Volt Amp or Volts*Amps) output. For smaller gensets and inverter, usually maximum Watts=VA rating.

So, in this case, a 40 amp regulator @ 24 volts, non power factor corrected (most battery chargers are still not PFC), would required around a 2.5 kW minimum genset.

If you had a PFC corrected battery charger, then:

40 amps * 29 volts charging * 1/0.80 charger eff * 1/0.95 PF = 1,526 VA

So, at first look, a PFC power supply would work on a Honda eu2000i (1,600 watts). Although--it is pretty close.

Quite a few of the Inverter/Charger units do have Power Factor Correction--And some have have programmable chargers too (you can program the maximum AC current they will consume). A lot of choices out there.
I understand the value of a Temp sensor

I'm kinda surprised there are not more choices... The Xantrex 24v 30a seems a bit smallish

Yea--I am surprised too. There are very few (if any) AC Battery Chargers that hold a candle to some of the Inverter/Chargers out there.

It is probably is difficult to convince people that they should pay 2x as much money for a 40 amp configurable battery charger with PFC... But for off grid folks with generators--I believe it can be well worth the money--The difference between an eu3000i vs eu2000i and less fuel usage with a smaller genset.

Of course, there are Yamaha inverter generators (similar to the Honda eu family--although, I am not sure if as fuel efficient at lower loads--factory fuel numbers seem to be science fiction at times).

If you need/want electric start/autostart, ChrisOlson has some good information about a newer Honda "delux" engine series:

Generators, Gen sheds, Gen fuel systems, etc.

-Bill

photon_trap · October 2012

Re: First build - input appreciated!

I am seriously considering an outback FX2524T and, in reviewing the programing manual I see the charge rate adjustments in aac (which I assume is amps AC) can anyone explain this and how I can relate it to DC battery charging?
Also, does anyone have any experiance with operating this unit on a eu2000i?

Thx
Jeff

Cariboocoot · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

I am seriously considering an outback FX2524T and, in reviewing the programing manual I see the charge rate adjustments in aac (which I assume is amps AC) can anyone explain this and how I can relate it to DC battery charging?
Also, does anyone have any experiance with operating this unit on a eu2000i?

Thx
Jeff

I can explain it: it's crazy.

On a 24 Volt system the AAC (yes; Amps AC) is roughly 1/5 what the DC charging Amps will be. This is somewhat inaccurate of course, but they figure it's close enough. In reality, it is.

I use the bigger inverter, the VFX3524, with the EU2000i. Functionally the two inverters are identical except for capacity. I have the charge limit set to 5 AAC on the inverter-charger which is about 25 Amps DC and it works fine with my 232 Amp hour battery bank. I usually only Bulk charge this way when the weather is bad, but for the past few days the panels have been down for roof repair so the gen has been doing all the work - including gas-demanding full charges.

vtmaps · October 2012

Re: First build - input appreciated!

photon_trap wrote: »

I am seriously considering an outback FX2524T and, in reviewing the programing manual I see the charge rate adjustments in aac (which I assume is amps AC) can anyone explain this and how I can relate it to DC battery charging?
Also, does anyone have any experiance with operating this unit on a eu2000i?

The amps AC is a useful way to tell your fx2524 about your generator. You program the fx with the aac capacity of the generator. You also program the fx to use up to a certain number of those aac for battery charging.

For example, you might set the generator limit to 13 aac and the charging limit to 8 aac. If you run an AC load (while charging with the generator) that is greater than 5 amps, the fx will cut back on the battery charging so as not to exceed the generator's capacity of 13 amps.

--vtMaps

photon_trap · October 2012

Re: First build - input appreciated!

Thanks! makes sense.
This unit is sweet, although a bit more expensive, seems you get a lot more

First build - input appreciated!

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