36V panel, 12v inverter what controler options??

maxhighlife · September 2014

I have 4- 270 watt 36V Panels, a 12v 2500watt inverter, 100 of 12v18ah battery's and my goal is to learn and test solar options while running a pool pump for 8 hours a day. is there a controller I can use that will utilize the 36v panel and the 12v inverter ?? Thanks

inetdog · September 2014

Re: 36V panel, 12v inverter what controler options??

Any MPPT type controller will work fine with a 36V (Vmp?) input to charge 12V batteries. You cannot use a PWM type CC.

But did I read correctly that you will be trying to put a total of 100 12V batteries in parallel? For a bank capacity of 1,800 AH? That is just absurdly complex to wire up and will kill batteries right and left.

maxhighlife · September 2014

Re: 36V panel, 12v inverter what controler options??

I have the batteries left over from a security contract,I was trying to use the things I already and understand more about the solarworld so my thought would be to use the panel at 35.3Vmp with the batteries 36vparallel series and a controller feeding the 12v power inverter. Is there a wayI can set the batteries up to avoid the issue, Thanks

BB. · September 2014

Re: 36V panel, 12v inverter what controler options??

Be very careful with series/parallel connections of batteries. There are a lot of issues to watch for.

For example, you usually do not want to have, for example, 3x 12 volt batteries in series for a 36 volt bank--Then connect 1-3x 12 volt batteries to each of the series batteries in the 36 volt bank. Batteries in series need to be discharged equally, or you end up with some batteries near full and other near drained--And with a single 36 volt charger, the "full batteries" get over charged (hot, use lots of water, lots of wear and tear from over charging) and the "drained batteries" do not get charged enough (from unbalanced energy use among the three series batteries).

Also, these days, 36 volt (and even older 32 volt) systems are becoming orphans in the Renewable Energy world. Try to stick with the 12/24/48 volt standards unless you really need 36 or other voltage for your specific loads.

In general, if you have a large AH/kWH stored energy requirement, going to 48 volts for RE off grid systems is usually the best bet... In your case, that allows you to put 4x 12 volt batteries in series. And now your 100 parallel battery bank becomes 25 parallel strings of 4x batteries each).

My only personal comment--I would recommend designing a bank for a single string of batteries--That usually means getting larger AH batteries in 6 volt, 4 volt, or even 2 volt size (3/2/1 cell "batteries"). A single string of batteries is usually the easiest to install and maintain.

If you need more AH capacity--Adding 2-3 parallel strings can work OK--Just may need more care in connecting the bank and a more rigorous inspection regime.

It is not to say that 100x 12 volt batteries in parallel will not work--It just brings a whole bunch of issues to the front and center--That can haunt you for years to come.

My humble suggestion--Lets start with your loads/energy needs. That will tell you what size/type/AH/Voltage battery bank you need. Starting with a battery bank first--Really does not help you design a system that will "optimally" support your loads (both cost and long term maintenance).

-Bill

jcheil · September 2014

Re: 36V panel, 12v inverter what controler options??

Don't even waste your time with 100 of those little batteries. You will be frustrated in no time. They will NEVER charge properly, you;ll have bad ones all the time which messes up the charging of the others.

I tried this once as an experiment. I got 48 UPS batteries for free (bigger than yours, they were 75ah) and put them all together.
What a mess. Every couple weeks trying to find the bad battery. Not to mention they were sealed (like yours likely) so I couldn't test them via SG.
Not to mention how much $ it cost in cross-connect cables. They were worth more than the batteries!

trust us...don't go there.

36V panel, 12v inverter what controler options??

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