24v/875ah Hi Lo Batteries

[Bigwheel]

Hi Everyone,

Here's the story, Got permission from the safety god at work today to take home two banks of 24v/875ah hilo batteries.  Not bad for a 20oncer of pop.  Maybe/maybe not,  Well at least the lead core is worth that and probably some.  We've got 2 machines that use the batteries.  The guys in shipping hate changing them out so they don't and are just sitting there in the way.  From what I gather there around 7-8 years old.  some of the cells are low on water and haven't been on the charger in a while.  The last time from what I was told they wouldn't take a charge.  But I would like to know the proper procedure to getting these back on line.  I'm going to get one of those hydro meter from the auto parts store to check the gravity of the 2v cells.  Should I top them off with distilled water and through them on the charger and then check the gravity.  From what I've read, and being that the batteries have been parked for a while, I got a feeling there's build up on the plates thus causing the inability to take a charge.  I have no experience and am timid when it comes to batteries.  My luck would be to smoke em and out some good ah batteries.  I'm just looking for your thoughts and low dollar approach to saving them.  It be a nice score for a small battery back up for the wind generator.  My 1kw of solar is grid tied in and being the wind generator is dc, I needed some place store.  Let me know what you think.  Thanks again for your input.  Chad

[disaray1]

Chad- Do all of this outdoors if possible, wear gloves and goggles etc...think safety.

 Top off the batts with distilled water before anything else. Invest in another 20oz pop for god, and borrow the correct charger for over the weekend. Stop at the auto parts and buy a hydrometer. Connect the charger friday night and let er' rip. Visually inspect every few hours- look for gassing (boiling) in the cells. Sunday, check all cells with the hydrometer and record each cell SG. Report youre findings here on monday for the next step.

 I'll bet they're junk- but it's certainly worth finding out..especially for free!

 Have fun and be careful.

 David

[Bigwheel]

Hi David,

Well, picked up a hydrometer this morning.  Last night when I got in.  I did top of the cells with distilled water.  It was below the top of the plates.  Quite a shame but oh well.  Though I did notice small pieces of black scale loose on top of the plates.  Don't know what that stuff was.  Checked the voltage on both banks.  The driest one was at 14.42 and the other was 21.2.  Put the charger on around 11:oopm and took it off at 5:30 and read at 25.7.  I then rechecked  it at 7:30 and read 23.4v.  I hooked it back up and told the guys to unplug it at 3:30pm.  That way they could charge up there current bank.  I'll check when I get in and see where the voltage is at.  I did notice that all of the cells were bubbling and letting off gas.  I'll use the hydrometer probably on friday morning to allow time for the cells to mix some more and get things moving around. I'll shut it down early and let things settle and take the measurements.  Got my fingers crossed.  I'm going to do all of this at work,  I'm thinking the charger is a 3 phase 24v charger.  No good for me here.  I'm going to put this one out there.  If and I mean if, half of the cells are good, can I cut those bad one's out and use it as a 12v bank?  Or if the other bank provides good cells, swap them in for the bad one's.  I'm almost certain they were all purchased at the same time.   So age, usuage and condition could be close in condition.  Just a thought.  I'll get back and report on what I find. Thanks again for your time.  Chad

[Bigwheel]

Hi David,

Well, checked on the first one when I got in last night.  From last night to this morning is was holding a charge at 24.4volts.  This morning I checked with the hydrometer and all 12 cells floated in at 1.150  basically in the red and needed to be recharged.  Let me know what route to take on this one.  Don't know if I should put some type of load on it and recharge it again.  The second bank was quite thirsty.  I left it on the charger for about 7 hours and the voltage went from 14.4 to 24.01.  that was with about an hour and half of off time this morning.  The little bulb in the hydrometer didn't even rise on any of the cells.  Just thought I'd give you somewhat of an update.  I will wait for your reply.  Thanks again Chad

[AbyssUnderground]

The hydrometer is showing dead so put it back on charge. Voltage has very little meaning on charge %age.

[DamonHD]

I don't agree with 'very little', but the relationship is complicated:

Look towards the end of my page, above "Sources/Links", the SOC table: http://www.earth.org.uk/solar-PV-pilot-summer-2007-more.html

It would be impossible to build purely electronic charge controllers if there wasn't a fairly strong relationship.

Rgds

Damon

[Bigwheel]

Hi Again,

Well left it on the charger for the weekend and the voltage was up to 25.6 when I got in last night.  The charger is automatic so I couldn't tell ya when it shut off.  Before I turned it on and used the equalize command, I checked the cells and they were measuring just above 1.200.  This is better than the other day but seem to think this is the best it's going to get just being on the charger.  I did a little thread reading and found some hope with using EDTA.  Woundering if I should take the route and see if getting the sulfates off the plates will allow the hydrometer to improve.  Or is it going to be a lost cause.  Just looking for some advise.  I have yet to haul them home.  just using the free energy to get a final decision.  When I get these things home would it be best to (if flusing them with EDTA and Distilled water)to cut the lead bar straps and pull out the individual 2v cells.  Easier to work with and could you use a standard charger 6v/12v on it?  or reconnect them to correct them to make 6 packs of 2v cells thus making a 12v bank.  I think from what I've read that I'm going to have to keep an eye on the 2v cells when running 12v into them.  Meaning they could easily boil over and loose it's water.  Hopefully I've got my facts straight.  Let me know how to approach it.  Thanks again for your guy's advise.  Chad

[disaray1]

Chad-

 Went on vacation here and just got back. It sounds like you may be dealing with a lost cause on those batts. It happens when it sits in a discharged state for some time. Yes, you could cut the bars and seperate into individual cells. It would be prudent to cut the center bar and make two 12 volt sections so you could use an automotive style 12v charger for further charging. I WOULD NOT use a 12v charger on a two volt cell!

 EDTA is something that has been discussed many times here, but I dont think there's concensus on it's ability to restore the damage that's already done. I've never used it. You might check whatsnext's diary- I think he was doing a long term test using the stuff on some old batteries...I'm not sure of his conclusions.

 You say all cells were in the 1200sp range? Can you take another set of readings and post?

 David

[Bigwheel]

Hi again,

Took a reading last night and it seem to improve by sitting.  The readings are hovering around 1225 about right on the white and red line.  Voltage was reading at 24.75volts.  I haven't done a thing with them since the weekend.  I did put them back on the charger and equalized the bank again.  Let me know what you think.  Thanks again  Chad

[disaray1]

 I don't want to sound too optomistic, but it does sound better than when you first started. Your readings say it's about 75% currently. Target sg should be around 1265 to 1275 for all cells, and total voltage at 25.4v. If one cell is off by 50, thats enough to cause headaches (called a bad cell). I think the next step would be to charge again- does the charger have any selectable settings, or is it one that just has a go button and turns itself off after some preset time?

 The step after this is to find a load to attach to the battery. You'll have to know precisely what that load is. Find something that can draw maybe 10 amps...maybe a couple of big lamps, a fan or a heating element. With a multimeter, confirm the amp draw of your load, and note it. Now, with a voltmeter connected to the batt, attach the load and take note of the battery voltage and the time. Note the voltage at say, 15 minute intervals. At 10 amps, this batt (new) should be able to deliver that 10amps for 87 hours. In your case, note how long it takes for the voltage to drop to 24.0 volts. From this info, we can roughly figure out the overall condition and it's usefullness.

 Keep your fingers crossed.

 David

[Bigwheel]

Hi David,

I'll report back on what I find out.  I'm going to be loading them up and hauling them home this weekend.  Everythig is official on getting them out of the shop.  That charger basically has only two setting, charge and equalize.  Before, I leave I am planning on one last charge.  Get them home and seperate the bank in half so I can run my 12v inverter and put a load on.  It will be interesting to see how long things will go for.  Like I said before, it will be nice to get some more use out of them and keep the green in the pocket until maybe something better comes along.  Thanks again for the help and I'll report back.  Chad

[Bigwheel]

I'm Back,

Did some testing the other weekend and got the results that hopefully are good.

I strictly did s resistance load test on the bank.  So it was a long drawn out process.  Basically used a load of 300 watts.  It's all the light sockets that I had on hand.  Once the load was turned on the voltage on both banks dropped to about 12volts.  (I split the bank in half inorder to run the cheap inverter I got.  Though I bought a used trace sw4024 last week)  I was able to run easily for 10 hours and the voltage dropped to 11.1 before I shut it down.  I'm waiting for the inverter to show up so I can get things charged back up and do an inductive load test on the battery.  That's basically what I have for know.  I did take the other bank to the recycler to turn it in.  At nine cents a pound, I'm already way a head.  Let me know what you guys think..  Thanks again Chad