Upgrading ?

tcvb · February 2014

I am doing a little upgrade to my current system,i currently have 3 12v 140W panels feeding a 12V 450AH BB,wet cell's 2 6v's parraled.I am looking to go with adding 3 more 140 W panels and wiring in series to get 24V.Should I leave the bank at 12V or build a new bank at 24V.Current batteries are 3 years old.

Thank's

Cariboocoot · February 2014

Re: Upgrading ?

Do you have 12 Volt loads you must run?
If not, going up to a 24 Volt system is a good idea.

Right now you've got 450 Amp hours @ 12 Volts. Rearrange the same four batteries and you get 225 Amp hours @ 24 Volts which is the same amount of stored power. But the power will be used and replaced more as Voltage than current, which makes the operation more efficient.

You need about 700 Watts of panel for that size battery bank. The 420 Watts you have is a bit shy to say the least. Doubling it to 840 would be very good indeed. And you would probably be able to keep your Morningstar 30 Amp controller (ProStar?) On 12 Volts the combined panels would be over 40 Amps and that controller wouldn't handle it.

tcvb · February 2014

Re: Upgrading ?

What I am looking at is this:

4 12V 90AH AGM Batteries wired in series then parraled,6 140W 12V Panels wired in series then parelled,Midnight Solar Classic 150 With E-Panel + with Outback 2000W 24V Inverter.It looks like this might give me a little more power if I am doing the math correct 4032W=2700W,in VB,VA. 24V 112AH-dble that 225AH,i may be a little shy on bank size though.Any thoughts?

Cariboocoot · February 2014

Re: Upgrading ?

90 Amp hour batteries? Why? Two 24 Volt strings in parallel would be only 180 Amp hours. At 50% DOD that's (90 * 24) 2160 Watt hours DC.

One string of 225 Amp hour batteries @ 24 Volts gives you 112 * 24 = 2700 Watt hours DC.

AGM's are more expensive per Watt hour, harder to keep track of, and easier to destroy. Unless you actually need the AGM no gassing or high current advantages you're better off with flooded cells.

For a 24 Volt system you would need to wire those 12 Volt panels two in series at least. With six panels you could put three in series for Vmp of about 52.5, then have two strings in parallel. Out of the Classic this should provide (840 Watts @ 77% efficiency / 24 Volts) about 27 Amps of charge current, more than enough for the 225 Amp hour batteries.

zoneblue · February 2014

Re: Upgrading ?

I think what coot is saying is that golf carts are considered the best all round entry level battery. Anything less is just a toy.

tcvb · February 2014

Re: Upgrading ?

Got a ? I have already purchased the two 90AH AGM 12V batteries,being that the 6V Flooded batteries are over three years old with little load put on,would it be advisable to wire then in series to 24V,then parallel them with the AGM's?

Cariboocoot · February 2014

Re: Upgrading ?

tcvb wrote: »

Got a ? I have already purchased the two 90AH AGM 12V batteries,being that the 6V Flooded batteries are over three years old with little load put on,would it be advisable to wire then in series to 24V,then parallel them with the AGM's?

No, because there would be a large difference between the capacity of the two strings (225 Amp hours vs. 90) and the battery types (flooded cells charge at higher Voltage than AGM's). It would ruin the AGM's fairly quickly.

tcvb · February 2014

Re: Upgrading ?

OK Thank's I am getting away from the flooded batteries due to the gases,i have them set up in my garage,even though it is vented I still have gases.I eventually want to add two more of the agm's 90ah.I am deciding on the inverter whether to go with 12v or 24v.I really don't have any 12v loads in garage.I have a battery imn my ham shack for my radios and stuff hooked up.

zoneblue · February 2014

Re: Upgrading ?

So around 650Wp PV. Nah id be staying away from 12v, unless you really have a big investment in 12v gear.

If you are dead set against FLA, then have you considered Lithium, they are increasingly common now and have a lot of great advantages, amongst them that small Ah ratings being happy on big loads.

The problem with 90Ah agms, is that a) they are probably automotive/marine/ups, and hence not sure about the cycle life /peak load support, and b) their low Ah rating forces you into lots of parallel batterys, which just complicates everything.

Im guessing cost and/or local availablity are drivers here, but you are getting into the slightly more 'serious' system territory, and that really calls for better core components. I mean you can patch some stuff together, but more often than not youll be having to go back and fix things up again later.

westbranch · February 2014

Re: Upgrading ?

Again we ask the question of: What are your loads? Before you can develop a good system design, the loads need to be defined...

jcheil · February 2014

Re: Upgrading ?

tcvb wrote: »

OK Thank's I am getting away from the flooded batteries due to the gases,i have them set up in my garage,even though it is vented I still have gases.

Then simply put them in an enclosed box in your garage (as they should be for protection) and put an external exhaust fan (to the outside) on the box triggered by the gassing voltage.

mike95490 · February 2014

Re: Upgrading ?

AGM's need to have the SAME provisions for gas venting, as overcharging, or thermal runaway causes acid spew and gas venting, then you can have a real mess to clean up. And then you get to buy new batteries, when AGM's vent, you usually have had something bad happen to them, and they are on their way to the recycle store.

tcvb · February 2014

Re: Upgrading ?

I am building this system as a back up stand by for my generator.I want it to have at least 2kw,run a few lights,the fridge,tv,and maybe a fan in case generator will not come on line or there is no gas.

Thank's

tcvb · February 2014

Re: Upgrading ?

I have my flooded batteries in a wooden box I built now,i ordered the midnight solars battery box recently and will look at venting it to the exterior.where would I find the fan device that would trip on like you had said.

Thank's

tcvb · February 2014

Re: Upgrading ?

I see in your tag line that you are using AGM's how's that working for you?
Thank's

zoneblue · February 2014

Re: Upgrading ?

Me? Yeah i have 400Ah 2v AGM cells in one series string. They are now 1.5 years old with no observable changes. I have no idea how long they will last, ask me again in another 6 years. They are very lightly used, i use a fairly low float voltage. In that scenario you do need to dream up some tricks to give the cells some occasional activity.

Upgrading ?

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