potential for free batteries!

[birdhouse]

hello-
a friend of mine is an electrician and has been working on a school.  they have some sort of back-up system that has/or is been replaced.  i don't have as many details as i would like.  i DO know that there are 30 batteries.  they are 2 volt and weigh 85 lbs a piece, and they have my info for when i can pick them up for free!  i have been working on a 24 volt system, so could use 24 of them in a series/parellel wiring scheme.  i figured i could high grade them to get the best 24. 

questions:
what is fully charged voltage on a 2v battery in good shape?  2.25?  2.3?  2.2?  i think it is in that range.
 
what would the voltage be in battery in good shape that has been sitting for 1 week or 2 without charge?
 
is it worth picking up a hydrometer to check the batteries?  i've never used one but am sure i could learn! 

any guesses on amp/hour capacity on one of these 2v jobbies? 

will 400 watts of solar be enough juice to do an equilization charge on this bank?  or maybe half at a time? 

any suggestions welcome.  i don't want to haul off 2500lbs of batteries just to bring them to the recycler! 

thanks!
adam

[thirteen]

A name off of the batteries would help and there should be numbers on them . Their age might be stamped on them or a tag wouls help.  If they were charged before bing discontected they should be ok.  When checking the batteries you might want to number them as and list their voltage as a record.  If you can I would get all of the cable connections that were on the batteries and look for problems mainly corrosion on them. Sounds like a good bargain.

[dapdan]

A 2V cell at rest (for a minimum of 12hr with out charge or discharge) should have the following voltage at full charge:

FLA 2.12 - 2.14
AGM 2.14 - 2.16

If there are no identifying info on the cell I find the following formula is good for estimating the capacity a 20hr rate:

Voulme in cubic inches = capacity

Just measure all dimensions of cell in inches calculate volume in inches^3 and "voila" the capacity at 20hr approximately.

More than likely they are AGM if they are used in a UPS where off gasing is a no-no. At around 85lbs I would guess they are in the region of about 600 - 700Ah.

Once they are AGM in a UPS system that was working  before being removed then they should be OK since the UPS would have kept them topped up and the self discharge of AGM are in the order of 1% per month giving them a long shelf life once they are fully charged.

One more thing, you will need 12# 2V cells to make a 24V bank and not 24# that would be two banks.

In respect of 400w of charging for a single bank of about 700Ah I would say that is on the low side and you need to double you panels to meet the recommended minimum of 5% charging rate

Cheers...
Damani

[Isaiah]

Using the hydrometer is just about the same as using a an  antifreeze tester only it is battery acid so be careful  what you do with the solution out of the hydrometer.
 You can get a cheap one at wal mart that uses little balls or I would go for a better one and I rince it out with clear water when done testing.
The cheap ones you would get at wal mart or discount stores the rubber bulbs dont last long!!!
 This sounds like you made a good find good luck with them.
  I have herd the scrap price is up quite a bit on scrap battery's.
2500lbs of scrap ones may buy a couple new golf cart battery's.
 We dont recycle til there is no hope at all for them some sit around a year or more.

[birdhouse]

thanks for all the info! 
i'm supposed to get "the call" to pick them up either some time today, or tomorrow!  i'll let you folks know how it goes. 

damini-  i hear what you're saying about the 5% thing with such a large bank and small panels.  would it make any difference if this system is going to be installed at my ranch, where it would be used for a weekend, then have a minimum of two weeks for the batteries to get charged up again?  currently our draw is minimal also.  some lights and a stereo.  i'd like to use 24 of em and wire them into two banks that are then connected intyo one (series/parellel). 

thanks!
adam

[Ungrounded Lightning Rod]

Batteries from building UPS systems (typically for computer server farms and the like) seem like a good source of "free batteries".  They need 'em to work well in case of an outage, so they are typically rotated out of service at something like a third of their rated life.

If you haven't had a bunch of power outages during their service they mostly floated, rather than being deep-cycled a lot.

[dapdan]

Bird,

I have 800w (max 26amps measured through a Victron Battery monitor) directly hooked up to 1000Ah AGM bank and it just manages to fully charge that bank while there are no other load connected. The only way know for sure is to hook them up and observe the voltage.

Cheers...
Damani

[dnix71]

Even at 10c a pound those batteries are worth some decent money for scrap if they are not usable. 2v sounds like lead. They sound like the bricks forklift batteries are made from.

You will need a lot more panel unless you are careful about discharge. You could pick the best 1/2 of the lot and sell the rest for scrap and buy another small panel.

[birdhouse]

well, i got a call, and they said i could pick them up tomorrow (thursday) but i want to pick em up friday on my way out of town up to my ranch.  will call again to make arrangements.  got fifty free 12' 2x4's the other day, and want to load those and all the batteries on my buddies truck on the way out of town.  (it's a f-350 diesel doulie 4x4 with a 12' flat bed) 

so lets say they are in OK shape.  i want to make two series banks of (12) 2v bats then parellel them together for a big 24 volt bank.  this leaves 6 of the worst cells un-used.  then charge them with two 200 watt 12v volt panels in series.  i hear what you're saying about not taking too much out of them as the panels would struggle greatly to get their voltage back up.  if i don't even use them this weekend, they will most likely have 400w of solar going into them for three weeks straight before anyone goes up there again.  i would think this would make an ideal "trickle" type charger for this bank, but maybe not.  is it even worth setting up the morningstar ts-60 i bought?  is there any chance they could overcharge? 

i'm getting really excited to get a re system off the ground!  i'll take some pics for sure! 

adam 

[dnix71]

I wouldn't leave them on 400 watts of panels for 3 weeks without some kind of charge controller. Charge them first and then add distilled water to level off the cells and charge them some more before deciding which ones to keep.