Used battery project - wish me luck!

[markopolo]

I saw an ad .......... that's my excuse

Before I left home I figured I'd take a chance on these batteries if they measured 12.5v.

12 x 12V/18AH in a custom aluminum case for $100. Navy surplus unit. AGM batteries from some sort of UPS unit.

They measured 12.2V but ......... I liked the box



The lid is fastened with 20+ screws and it presses down slightly on the batteries to hold them securely in place.



The box is precisely sized to fit two batteries in one direction and, because you need a bit of space to place or remove batteries, there are two clever compression plates (simple wedge) to hold them in there tight. The batteries sit on and are cushioned on the sides by rubber mats.





They were wired in a series / parallel configuration to be a 72 volt battery pack.



I removed the old wiring and control or monitoring board and reconfigured it to be a 12v battery pack, basically two parallel strings that were also paralleled. My wiring does not cross the under the lid's compression beams. I ran 8 gauge wire internally to the external connectors on the box. I don't plan on drawing large amounts of current from this if it works.

This is day 3 on the charger. I actually used two chargers, a basic bulk charger to bring them up and now an RV type 3 stage charger. They did not charge fast so that could indicate excessive internal resistance.

This would be a 216AH battery pack if new. To test it, I'll repeat this test: http://www.classbforum.com/phpBB2/vi...tart=11#p16513 . If the results are similar then I'll get some help to lift the 120lb box into my van. If it works, I plan on putting them near where the side entrance to the van is. On edge, the box only measures 8 inches.

Wish me luck!

[booster]

The slow charging may not be an issue if it is from a UPS setup. When I was reading about that kind of stuff, they said the batteries they use are a bit different, because they are made to be on constant float charge type voltages, with rare cycling. Slow charging rates, and low discharge rates were also mentioned about them.

[markopolo]

I'm hoping they work.

The specs on this type of battery are a little different. 14.9 and even 15 volts are noted as max charging on the spec sheets I've read.

They are near fully charged now I'd think.
At 13.55 volts they're taking 0.25 amps right now. That has slowly come down.
I just gave them 14.5v as a quick test and they'll take 0.75 amps and I just gave them 15v as a quick test and they'll take 3.0 amps. I don't let them stay at higher voltage for more than a quick test though. It's not much current on a per battery basis if you divide the amps by 12.

I had started charging 4 of the 12 before I decided to assemble the whole unit. I think the second round of charging started with the whole pack around 12.5v. The whole pack was taking 7 amps then. The pack was brought up to 15v at some point overnight because that's what I found them at in the morning. That was probably only a couple of hours at most though because they weren't anywhere near that when I checked before turning in.

[booster]

It looks like they are coming into the amps that AGMs would normally do. Most manufactures talk about .5-1.0% of capacity at absorption voltage.

[markopolo]

I'm quoting the previous test for easy reference ( http://www.classbforum.com/phpBB2/vi...tart=11#p16513 ):

Originally Posted by markopolo

My battery bank: 180ah
Unplugged van from utility power, removed fuse from solar panels
Fresh off 13.2 volt float charge, so fully charged batteries.
I used a 60w incandescent bulb on the inverter for the test.

At 0 minute 13.2v applied 5.7 amp load
At 3 minute 12.5v
At 7 minute 12.5v
At 10 minute 12.5v
At 40 minute 12.5v
At 60 minute 12.5v

Turned off the inverter at that point and unplugged the 60w bulb.
The battery voltage immediately recovered
at 1hr 5 minute 12.8v (used another meter then and it showed 12.82v)
at 1hr 30 minute 12.8v
at 2 hr 12.9v (used another meter then and it showed 12.85v)

Today's test results from the 12 AGM UPS style 216AH battery pack: (different inverter, different wiring, no RV related parasitic losses)

At 0 minute 13.49v applied 5.64 amp load (60W incandescent plugged into MSW inverter)
At 3 minutes 12.72v 5.64a load
At 7 minutes 12.67v 5.64a load
At 10 minutes 12.66v 5.65a load
At 40 minutes 12.65v 5.70a load
At 60 minutes 12.64v 5.74a load

I turned off the inverter at that point and unplugged the 60w bulb. The battery voltage recovered to 12.85V at the 1hr 5 minute point in the testing.

At the 1hr 30 minute point in the test the battery voltage was 12.9v.

These batteries seem to be in pretty good condition. The resting voltage after the duplicated test pretty much matches the previous test of the batteries in my RV. To me that indicates the batteries should all play nicely with each other.

[booster]

That does look pretty good. Is the 12.9 volts fresh off the charger or rested to remove surface charge?

[markopolo]

Voltage was 12.91V two hours after the charger was disconnected. The first hour was continuous 5.7A load powering a light bulb (5.7ah used). Second hour was resting, after the load test.

[booster]

That makes it look even better-good bargain

[papab]

Cool, where did you find these?

[markopolo]

Local online ad here. I see used UPS batteries for sale periodically. Standard procedure is to replace UPS batteries on a schedule before they get too old.

[markopolo]

I found a great place to put these batteries in my van. 12 of them can measure 12" x 21" and the bottom of one of the closets in the van is 12" x 24".

Found a place:


Added new closet floor:


Exterior panel re-installed after cut-outs:


I ran the wiring to the new location and added 100 amp reset-able breakers on each end of the positive wire.

Bonus project - I added exterior access to the rear of the closet. It's deep enough to store two fold-up-in-a-bag chairs there and the new cut-out makes for easy access to them

[wincrasher]

Really coming together! Looks awesome.

[markopolo]

Thanks Win.

I pretty much finished wiring up the batteries last night. 24 little nuts, bolts and lock washers to undue and then 24 little nuts, bolts and lock washers to re-do in a different config & a whole lot of crimping connections I forgot to add a 12v accessory outlet right there so I just have to do that.

Approx 396 amp hours total capacity now. I can't wait to test running the small air conditioner. I'll update this topic: http://www.classbforum.com/phpBB2/vi...hp?f=12&t=2286 after the test.

[wincrasher]

I take it you are charging across the whole bank (neg on one corner, pos on another)?

What are you doing for heat dissipation? Didn't see any venting in those pics. Or do you not think it will get hot on discharge?

[booster]

Originally Posted by markopolo

Thanks Win.

I pretty much finished wiring up the batteries last night. 24 little nuts, bolts and lock washers to undue and then 24 little nuts, bolts and lock washers to re-do in a different config & a whole lot of crimping connections I forgot to add a 12v accessory outlet right there so I just have to do that.

Approx 396 amp hours total capacity now. I can't wait to test running the small air conditioner. I'll update this topic: http://www.classbforum.com/phpBB2/vi...hp?f=12&t=2286 after the test.

That is a lot of capacity compared to what you had. It will be very interesting to see if the UPS batteries give up charge as quickly as "regular" AGMs do. I have read conflicting info on that. Also will be interesting to see how the charge balance works out, as in if the batteries get to full at the same time as your originals.

Interesting stuff.

[markopolo]

It is going to be interesting

I think it will help that my batteries are being charged or maintained most of the time (almost all of the time). The timer based charging profile should get them all full eventually. The boost voltage from the alternator when cold might be a good thing.

I installed a cut-off switch so I could isolate the banks if needed.

[markopolo]

I made a bit of a mess - I had an old cartridge of black silicone and used it to stick 1" blocks on top of the batteries to act as hold-downs when the new closet floor is fastened in place. I guess it was too old .... two days later the silicone still has not cured so I have to go clean up this black goop. I have a bad habit of being generous with caulk ...........

Maybe it froze in the cartridge or something.

[booster]

Yuck, I have had that happen, too, and there doesn't seem to be any predictability to it.

Isopropyl will usually take off silicone pretty well without damaging thing, especially if you have some of the non diluted stuff.

[markopolo]

Thanks for the tip re: Isopropyl - it worked great removing the oily residue.