Can this 40 battery bank work??

Freewilley

My friend has a son in the fire dept and just got  40 of these
AGM by C & D Technologies UPS 12 540 MR 20 hr rating 149
They are 5 year old backups from the fire dept.

He has about 1200 watts of solar panels on his off grid system. He intends to hook up all 40 in his bank. His bank is 24 volts.

Will that work? (I suspect not) If not, what kind of bank would you design with these free batteries?

littleharbor2

What is he powering that he needs 20 parallel strings of batteries?  That will give him a 2980 ah bank. It's absolutely ridiculous but if he insists he's going to need around 300 amps of charging power to maintain all those batteries.
 He can set up 10, 48 volt banks

mike95490

UPS batteries are good for a couple dozen deep cycles.   That's why they are "given away", so that the FD does not have them die next month. 

Best use, get the $5 each from the county recycle program and buy DEEP cycle batteries

Estragon

Putting the core/recycling credit towards new, properly sized, deep cycle batteries makes sense to me.

If I really HAD to use them, I'd put them in a 2 series (24v) x 2 parallel (~300ah) bank. 1200w of pv might provide ~1200x.75/28v= roughly 30a charging - about right for a 300ah bank. They'll likely fail regularly, so float the remaining 36 batteries periodically, and swap into the active bank as required. Some may be near-dead already, so culling with a load test might be a good idea.

706jim

I was given Nife batteries from the railroad. Ten years old but "still perfectly good".

NOT!!!!

And was lucky enough to get the coast guard to dispose of the hundred or so dead turkeys that I was otherwise stuck with on an island.

Buy new deep cycle batteries would be my recommendation.

Photowhit

mike95490 said:  

Best use, get the $5 each from the county recycle program and buy DEEP cycle batteries

Right idea, but seriously wrong value! I believe lead acid batteries are currently going for 30 cents a pound here in Missouri, a 12 volt 149 Ah battery should weigh 130 pounds or so! That's big bucks! around $40 each... If he's near by, I'll pick them up for $5 each!

I would hope Canada has a market for lead acid batteries. This 2011 report is saying $5-$15 for a car battery (car batteries will weight much less)

http://www.canadianbatteryassociation.ca/files/2011 Annual Report.pdf

Estragon

Most places locally (MB) are ~$30 refundable core charge added to price at purchase. May be lower for little powersports batteries etc., but seems to be the same for car/GC/L16.

just starting

So same senerio, my batteries came from a weather station, I have 12 2s6p so around 900 ah same batteries, they have worked for 2 1/2 years now, I only did it because I got them for 1500$ and they definitely paid for themselves, now I'm on LiFePO4 so they just float now, it's a decent battery for what it is.

Marc Kurth

FWIW, the recycle rate with my guy is currently $0.38/lb.  A typical 150 ah AGM weighs around 95 to 100 lbs.
So, 40 x 95 = 3,800 lbs.is $1400+

C&D is well known in the world of OEM and standby applications. They are also well know for not making an actual deep cycle battery designed for repetitive deep cycles.

If the old batteries are now going to be used in a grid tied battery backup app, then install around 50% more than your load calc requires and it might work just fine. If the app is more demanding than standby, sell them all for scrap and do something more effective with the money. Good AGM's don't normally just go belly up suddenly. They will warn you that they are going soft for quite awhile. People who know how to read that curve, know when to replace.

There are good reasons for this type of battery getting replaced on a regular schedule.

Marc

 

Photowhit

He is in Canada, I meant to come back and suggest if he intended to sell for scrap, he might pick up a pallet and 'palletize' them and then ask for bids, Particularly if he has a loading dock where he can store them for pickup. AGM's aren't a hazardous load in the US, so likely not in Canada.

mcgivor

The scrap value will still be there when dead, I say use them for educational purposes, find out first hand why it's difficult to parrallel so many batteries, why 5 year old batteries are disposed, why the charge rate is important, why standby batteries are ill suited to cyclical use and so forth, as pointed out. Then absorb the information provided, sell them for scrap then get into something serious, nothing like experience to gain knowledge, because information is not knowledge, others can only supply information.

mike95490

But the cost of all the interconnects ....

Estragon

If he wires them all up, the bank would be something like 149a x 20 = ~3000ah@24v. 30a solar may not even float that. Wired 2s2p for ~300ah would be about right for available solar, and not cost much in wiring. Just a bit of work swapping them out as they die.