Amp Hr question.

[Jerry]

I have 40 batteries in a 48 volt battery bank.  These are 30 lb each lead acid gel cells. The  specs on the side of the cases reads. 12v, 150w/cell, 15 min.

How many amp hrs do I have at 48 volts? They are configured 10 rowes perelelled of 4 each in siries. Befor I take some heat about gel cells, 2 things. they were free and like new. This 1200 LB bank should have a few AH.

Thanks for any help.

Jerry

[Rover]

Hi Jerry!

Man you come up with some strange stuff. I have to figure at 30LBS/12V each these are not deep cycles. 15min = reserve capacity ? ...  (way out guess)

Small battery size?

the  150w/cell kinda gets me .. er umm real curious

Yeah I know , Absolutely no help ...

Rover

 

[rossw]

I have 40 batteries in a 48 volt battery bank.  These are 30 lb each lead acid gel cells. The  specs on the side of the cases reads. 12v, 150w/cell, 15 min.

How many amp hrs do I have at 48 volts? They are configured 10 rowes perelelled of 4 each in siries. Befor I take some heat about gel cells, 2 things. they were free and like new. This 1200 LB bank should have a few AH.

At face value, 40 batteries in 48 volt bank, each being 12V would indicate 10 parallel strings of 4 series batteries each.  *DOH* You already said that.

150W/cell doesn't make any sense.

Based on my own 2V/500AH SLA cells, around 30 watthours/Kg energy density, your batteries are 13Kg each suggests about 400 WH per battery, or around 30 amphours per battery.

IF all these assumptions are right, you have 320 amphours @ 48V. But for maximum battery life, you don't want to discharge them more than about 10-20% of that, so you probably have a bank you could regularly use to around 30-40 amphours discharge (2000 watt-hours, give or take).


Edit:  Actually, 150W, 15 mins....   150W @ 12V = 12.5 amps.
12.5 amps for 15 minutes = 3.125 amp-hours.
that's about exactly 1/10 the estimated cell capacity.....  coincidence?

[mab]

I've seen some UPS batteries that were specified in watts/cell as the normal Ah ratings don't mean much when you're draining a battery in 15mins.

rossw: I think you left out a factor of 6 as it's 150w/cell so 900w per 12v battery

so 900w @12 v for 15 mins is 75A.

which gives 18.75Ah (at the 0.25 hr rate) - at the 10hr or 20hr rate it might be more like 40 or 50Ah I would guess? - need an expert opinion here. 

mab

[Jerry]

Thanks guys. Concidering the price I paid for the batteries ($ 0 ) I'll just use them till they give up the ghoast. Then they'll bring a good scrap price and I'll more then recupe what I've got into them.

I was just curious what kinda prefomance I could expect from these? I'll check the manufactures specs if available?

Jerry

[artv]

Hi Jerry,...I wasn't a member here when you posted,...but read everything(your threads) I've found so far......did you ever do anything without batteries???.........The EV thread is excellent,.......thats where I am now in my search......looking forward to your postes......
Thanks for returning ........artv

[Jerry]

Hi artv.

Thanks for the welcome back. I did fly a 1/3 hp ecm just for fun. I connected it directly to some small CFLs. They seem to ignight at 60 to 70 volts. They also run on DC just fine.

They did light up fairly bright on a good wind gust but dimed out of cource when the wind tapered off. But it was all in good fun.

Jerry

[Rover]

Hi Jerry,

You probably are already going this way, but just charge one of the batteries up and come up with our own  A/hr capacty after applying a load .. even if its just voltage drop based. Probably be more accurate than any sticker or claim anyway

Rover