Battery Choices

larrybc1 · November 2012

Hi,

Need some help on deciding the best battery to go with..I am in the Philippines so dont have a lot of choice on batteries--No Rolls Surrette..Trojan was the best I could find.

My system is 25 ==210 watt panels..loads initially 9000-10,000 Watt Hours per day--but it is a beach resort and I want a bigger system in case of expansion I will be able to handle the increased loads.

Battery choices:

1. Trojan Premium Line L16RE-2V--1110 AH/20 hr rate..$400 each..need 24 batteries= $9600

2. Trojan Industrial Line IND17-6V--897 Ah/20hr...$952 each..need 8 batteries= $7616

3. Trojan Industrial Line IND23-4V--1233AH/20hr..$906 each..need 12 batteries= $10872

trying to keep just 1 string of batteries..Been told that the Industrial Line will last much longer..

thks Larry

Cariboocoot · November 2012

Re: Battery Choices

Well 10kW hours on a 48 Volt system is about 208 Amp hours. Keeping the DOD down to 25% would be 834 Amp hours minimum.

That array (5250 Watts) should be able to produce 84 Amps on a 48 Volt system, which would support 840 Amp hours (above battery capacity fine).

For 1110 Amp hours that's a 7.5% peak charge rate.
For 897 Amp hours that's a 9.3% peak charge rate.
For 1233 Amp hours that's a 6.8% peak charge rate.

Looks to me like over-all the IND17-6V is the best choice.

larrybc1 · November 2012

Re: Battery Choices

Cariboocoot wrote: »

Well 10kW hours on a 48 Volt system is about 208 Amp hours. Keeping the DOD down to 25% would be 834 Amp hours minimum.

That array (5250 Watts) should be able to produce 84 Amps on a 48 Volt system, which would support 840 Amp hours (above battery capacity fine).

For 1110 Amp hours that's a 7.5% peak charge rate.
For 897 Amp hours that's a 9.3% peak charge rate.
For 1233 Amp hours that's a 6.8% peak charge rate.

Looks to me like over-all the IND17-6V is the best choice.

thks for the info..I have the Outback FM80 charge controllers..I was looking at the peak efficiency chart and it shows the best efficiency at around 68 volts input from the panels..with my array setup ( 2x5 and 3x5) i will have 92 volts going to the charge controller and it shows an efficiency drop of around 2%..istill around 95% efficient..is that anything to worry about? thks

Cariboocoot · November 2012

Re: Battery Choices

larrybc1 wrote: »

thks for the info..I have the Outback FM80 charge controllers..I was looking at the peak efficiency chart and it shows the best efficiency at around 68 volts input from the panels..with my array setup ( 2x5 and 3x5) i will have 92 volts going to the charge controller and it shows an efficiency drop of around 2%..istill around 95% efficient..is that anything to worry about? thks

No, not really. That efficiency drop will occur only at full power and only if the controller chooses to load the array in that manner. It may choose a completely different current * Voltage setting than Imp * Vmp at any given time depending on what it 'thinks' is best.

The FM80's output current is limited to 80 Amps, so any current possible above that will not be available to charge the batteries. Another reason to not got with a larger bank as it will further decrease the peak charge rate (by a small amount).

H2SO4_guy · November 2012

Re: Battery Choices

I would consider a forklift battery like a Crown (NAWS carries them) or something along the lines of 2 volt cells. The Trojan L16RE is basically an L16 with the 3 cells wired in parallel so you already have 3 strings when you buy them. The forklift cells are pretty forgiving but do have a little more self-discharge so would require a bit more power, but tend to last a very long time. If a forklift-type 2 volt cell goes bad there are used ones available to put back so the pack can be used more. Not so much with the L16 types. Shipping is so expensive for you it doesn't make sense to go with anything that won't last a very long time, so I would factor that in.

Good luck and let us know how it went.

Skip

larrybc1 · November 2012

Re: Battery Choices

H2SO4_guy wrote: »

I would consider a forklift battery like a Crown (NAWS carries them) or something along the lines of 2 volt cells. The Trojan L16RE is basically an L16 with the 3 cells wired in parallel so you already have 3 strings when you buy them. The forklift cells are pretty forgiving but do have a little more self-discharge so would require a bit more power, but tend to last a very long time. If a forklift-type 2 volt cell goes bad there are used ones available to put back so the pack can be used more. Not so much with the L16 types. Shipping is so expensive for you it doesn't make sense to go with anything that won't last a very long time, so I would factor that in.

Good luck and let us know how it went.

Skip

Hi skip,

will look for some forklift batteries in Manila..should have some there..So the Trojan 2 Volt is not so good? thks larry

H2SO4_guy · November 2012

Re: Battery Choices

In batteries, the less strings the better and the 2 volt Trojan L16RE is 3 of the 2 volt cells in parallel so you're already dealing with 3 strings. It is the same thing as getting 24 of the L16's at 6 volts each and making 3 parallel strings, just that the hookups are done inside the jar. Not the best way to go and not known to last near as long as the 2 volt cells that are large like the Crown type. Here's a link to the NAWS ones, but like you said, check out the local fare. http://www.solar-electric.com/2voltbatteries.html

Good luck,

Skip

Cariboocoot · November 2012

Re: Battery Choices

Yes the 2 Volt Trojans are the 6 Volts with the cells paralleled instead of connected in series.
Yes they are less than ideal for a 2 Volt cell because you have three reservoirs to check instead of one.
No they do not present the parallel string problem found with multiple batteries because the parallel connections are fixed and internal to the battery; not much different from constructing one larger cell in electrical terms. The main problem is the 3X as many reservoirs.

In any case they aren't a good choice here.

The forklift batteries may not be either; they are monolithic, which means heavy and difficult to manage. Otherwise a fine source of power.

niel · November 2012

Re: Battery Choices

actually, if you look at the sunxtender l16 lineup you'll notice the same pattern so i believe the 2v l16 is also using the 3 cells paralleled internally. a few of their other 2v batteries are similar as other 6v versions, but with the cells wired for parallel internally. in the case of agm batteries though you can't check on the individual cells by specific gravity so i would prefer in a case like that to take the risk of 3 parallel strings using the 6v batteries that you could at least isolate the batteries and check their individual voltages.

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