Forklift Battery Question

[RCpilot]

I have a GNB 24Volt 750AH battery that I have had a desulfator running on for a month or so. The battery is going to be the base of my Solar System. I split the battery to 12 volts so now I have a 1500AH battery. Today I decided it needed a good charge, it really hasn't had a good charge since I got it. All cells are within .1 volt of each other the fluid inside is clear. The battery holds a charge around 12 volts for quite some time. I connected a car battery charger to it and the charge rate started around 20 amps and after about 3 hours was down to 15 amps. The voltage of the battery is sitting at 13.39 volts and hasn't come up any more in the last 6 hours or so. How can I get the battery to 14.1 volts for an equalization charge? Do I simply need more current? At 15 amps of current, will it eventually come up? 15 amps is only C/100 instead of C/10 like I see many post that these batteries need. I don't have any other way to charge it any higher than the 15 amp charger that I have without spending a mint on one of those Forklift battery chargers. Can somehow I overcharge it with my setup? Damage it? The Forklift company I bought it from guaranteed it to be a good battery in the sense it would hold a charge, which it does. I haven't tried to load it yet but I have a Xantrex ProSine 2.0 2000 watt pure sine inverter ready to connect to it in the next day or so and wires ran to a breaker box. I'm just concerned about it reaching the voltage that it is at and not going any higher.

Kelly

[TomW]

RCpilot;

If it is a 12 volt system and you can get within jumper cable [or other suitable cable] range maybe your vehicle alt could boot some bigger amps into it? While you carefully monitor voltage, of course.

Or, if you have grid, rig up an AC motor to drive a junkyard auto alt. A decent one should do 30 to 60 amps.

Just ideas on "the cheap".

Cheers.

TomW

[bob g]

in my opinion, you should forget the voltmeter except as a reference of rough condition of the batteries state of charge,, and i do mean rough!

get a  hydrometer, this is the only way to determine the state of charge of a lead acid cell with any certainty. learn how to use it properly, temp compensation as well. and get yourself a log chart started for each cell, so you can track the cells over time.

you will want to charge it with enough current to get it to boil a bit, so that the electrolyte doesn't stratify, boiling a bit will mix it well.

you want to charge it until the specific gravity will not rise any further, it would help if you contact the battery manufacture to find out what the specific gravity for that battery should be when fully charged. also ask them at what voltage they recommend you equalize the cells at. Don't get cute and think you know better than them, follow their recommendations and you will have much better luck keeping this battery up to its best condition.

using a voltmeter is fine for routine charging, but when you fully charge and especially when you equalize the cells a voltmeter is worthless (for determining state of charge), get a quality hydrometer!

at 1500amp/hrs, that battery will accept around 375amps charging current at between 50 and 80 percent depth of charge. so if you plan on working this battery you will need some way of putting some current into it or it will take forever to charge. 15amps might be fine for finishing off the charge, but will take a long time to charge the battery and will not get the battery to bubble which is needed to keep the electrolyte from stratifying.

and in my opinion, forget the damned desulfator!

in conclusion, contact the battery manufacture, find out at what voltages and currents they want it charged at, find out what equalization voltage they would like, and find out what the specific gravity should be on a fully charged cell in that battery.

follow their directions and you will have no need for a desulfator (those things drive me nuts!)  

after going back and rereading your post, you state the battery has set for about a month and the voltage is around 12 volts,, that is basically a dead battery, so at 15 amps it is going to take several days to see the voltage come up. without a hydrometer it is going to be difficult to determine where you are with this battery.

hopefully this is helpful to you,

bob g

[Flux]

I agree with bob.

Try charging each section separately, you don't have enough current to charge 750Ah.

Just leave it on at 15A for a week and see if the volts move. If not you may need to hit it with about 50A to get it to gas after standing for a long while.

If it is old then 15A may not supply its self discharge. You are going to need a lot of solar power to handle that capacity with the self discharge of a lead antimony high cyclic duty battery.

Agreed about desulphators and the hydrometer.

Flux

[RCpilot]

Bob G thanks for the comments, I have a hydrometer and was thinking that it was lying to me hence focusing on the meter readings. It seemed no matter how long I left the battery charging (Never more than 6 hours) it's reading always said the battery was dead. You make a great statement that gives me hope and was what I was wondering, that I simply wasn't stuffing enough juice into the battery to get any results. I had a brainstorm late last night after reading my Prosine 2.0's manual. I don't have it hooked up yet, still NIB. It has a battery charger built in and it goes to 100 amps. I think I will hook it up if nothing more than to charge the battery with right now. I'm not ready to power any household circuits with it yet. I left the battery at 15 amps all night and just went out and checked and it's actually at 12.44 volts this morning .5 more than when I went to bed last night. So, it seems it is coming up. I will get out there today and run another hydrometer test. Sorry the desulfator drives you nuts I have had pretty good luck with smaller batteries and using it to "bring them back" It's the first time I have tried it on something so large. I guess I was just expecting faster results with my charger. To recap: I will rely more on the hydrometer, I need more charging current and I need to contact the BM to see what kind of data sheet I can get for the battery. I just connected my Solar panels in addition to the charger which from the looks of the sky, I am going to finally get some sun (been rainy for a few days now) and that will get me about 8-10 more amps as well.


Kelly

[Nando]

RCpilot:

The Desulfator you have is for small batteries (car size range)for 1500 AH the unit will have to work for months before you notice something positive.

Desulfators for high current (ah) batteries, do require much higher power than the 0.6 or so watts that are presently used by these small desulfators.

For 1500 AH, the desulfator needs to be around 10 to 20 watts capable with 500 amps discharge capacity (minimum) to deeply penetrate the large plates and to be able to overtake the large internal capacitance of the batteries and hit the plate with reasonable fast peak current.

Nando

[RCpilot]

Thanks for the comments Nando, how did you know what size Desulfator I have? But, you must be psychic as I do indeed have a small model. I have seen the killer circuits on the Desulfator web site and just haven't had time to try to build one. If the little one I have will do Anything at all and do it in lets say three or four months, I have the time. At least someone believes in them!

Kelly

[Nando]

RCPilot:

I have designed them, several decades ago, for very heavy AH battery banks.

I am quite familiar with the present available desulfator sold in Internet which is a copy of a simple pulser ( LM555) with a 330 Uh choke with a 2200 microhenry choke to isolate the 330 uh choke pulse from the power supply for the pulser section.

They are available from 20 to 120 dollars and most of them have the same basic principle and it seems that they have not discovered the circuits for high power which implies to have a lot more of technical knowledge to make them.

Nando

[bob g]

its not that i don't believe in desulfators its just that if you take care of your batteries and charge them properly, fully and equalize when needed you won't need some technology that may or may not work.

alot of folks think that sulfation is a bad thing, when the reality is it is a normal chemical process that takes place when a battery discharges. What drives me nuts about the hype surrounding desulfactors is the claim that sulfation is bad for your battery.

hard and crystallized sulfation is what you get if you allow partially charged plates with their normal sulfation sit for an extented amount of time, harden and crystallize.

a desulfator should only be sought when someone has neglected their batteries to the point that normal charging, and equalization cannot break down the hardened or crystallized sulfation,, even then my bet is most of these units are worthless

and don't do anything that a controlled equalization would not have done anyway.

this is a classic case of "create the crisis (where one does not exist) and provide the solution (a solution you can make money with).

bob g

[RC in FL]

I am not a believer in desulfators.  The variables of A-H size and constuction makes any single solution impractical.  Probably more batteries have been damaged then helped by desulfators.

Work on each batteries individually.  This will get the amps needed down.  You need 75 to 150 amps charge capability for these batteries.  If you can hit them with a 20% A-H charge this will help clear sulfide build up.  

You should, however, be able to bring them up to full charge with 20 amps unless there is internal leakage problem.  When fully charged it should not take more then 5 amps at a 14.3 vdc to maintain bulk charge voltage.  It could take several days to get there at 20 amp charge rate.

I hope you don't have one of the auto parts store plastic hydrometer.  They are trash.

[RCpilot]

You say work on each batteries individually, you mean each cell? I tried charging a few cells today and it pegged out my charger even on 6 volts. It was awesome though, hitting around 40 amps. But the charger is only rated for 12 and wouldn't last long.

I have discovered another problem and this may be why whoever owned the battery before got rid of it. One of the buss bars that connects one cell to another is loose. I can take a screwdriver and lift it up enough to see the post underneath. I discovered it when I was trying to charge individual cells today and heard a crackling sound from that bus bar and some smoke coming from it.

How do I fix this?

 As I lifted it up, around 1/8" or so I can see the post underneath is corroded. So, I guess I really need to remove the Buss Bar from the other cell as well so properly clean the corroded post. On a "How it's Made" show about a month or so ago I watched as they built a battery very similar to mine. And it showed them using a torch to solder the buss bars together but I would imagine that they were doing it before the battery had acid and gas. Now I would be afraid to get a flame around it unless someone can convince me that it can be done without blowing myself up.  

So, anyone know how to re-attach a loose bus bar?

[RP]

I've never seen this done but since the bussbars are essentially solid lead, here's how I'd do it (for what it's worth):

Take the battery off charge for a while and perhaps remove the vent caps for a bit to relase any hydrogen gas that may have accumulated under the caps (then replace them).  Cover the battery with cardboard or something to reduce the chance of an accidental short from metal tools while working on it (except for the surgical area of course).

Assuming you don't get a better idea from others (or a forklift battery dealer), I'd drill a hole through the top of the bussbar down to the top of the post using a drill bit just a bit smaller than the post diameter.  (Be careful, lead tends to "grab" a drill bit)

Next, measure the distance from the bottom of the bussbar to the top of the battery and make a "dam" out of plywood or some such of the appropriate thickness and fit it under the bussbar and around the post.  Without a picture I'd guess you could take two small pieces of plywood, clamp them edge to edge and then drill a hole (same diameter as the post) through the joint.

Install the dam around the post (under the bussbar) and liberally coat the inside of the holes in the bussbar and the top of the post with solder rosin (plumbing section at the hardware store).  Using either a large soldering gun (100watt) or a small propane torch start filling in the large hole you drilled with solder being sure to join it with the lead of the post and bussbar as you work toward the surface.

Since you'd have a tin of rosin handy anyway, you could use solid core solder also from the plumbing department.

Lead isn't the worlds greatest conductor of heat but just to reduce the chance of heat related damage, this could be done in small steps allowing time for things to cool before proceeding.

Hope this helps

[wdyasq]

Before I tried 'cut and paste' on the existing cell, I would remove the buss-bar, clean the post, then 're-slot' the buss-bar, taking enough lead from the inside to assure it would clamp back together.

If it was decided that that post, or others needed recasting, I would ask the battery re-builder if he could do it. If not, I would remove the battery from the 'group', and fill the cell with CO2 before soldering. I would use a whole lot more than a 100W soldering iron. I think a heat-gun might work, but I'm not sure. A small oxy/fuel torch, IMO, will be better than a propane torch because one could melt part of the post  and apply solder/lead. It could then be reshaped with wood-working tools.

I would practice on a dead car battery filled with water before operating on the real patient.

Ron

[RCpilot]

Thanks for the tips everyone! I succeeded in fixing it tonight! Got off work and headed straight for the battery. What I did was as you suggested was to remove the bar. I got a torch and after using air to blow any hydro gas out of the cells covered them with a wet rag. Then heating the good side of the bar, got it pried off and cleaned it and the posts real good. By then, there was a gap on the ID of the bar on each cell post. I then just laid the bar back on, took a wet rag and made a rope out of it to contain the lead. I had some lead strips I have saved over the years and cut them into sticks. Then heating the top of the post fed the lead into the gap. It filled the gap and then puddled on the top of the bar and melted into the bar, and when it cooled the repair looked as good as the others. Then, I FINALLY connected my new inverter (Xantrex Prosine 2.0) up to "ShorePower" the A/C outlet, and using the charge function was seeing 50 amps going into the battery. I am pleased with tonights accomplishments and probably wouldn't have been quite so brave had it not been for the help and tips of everyone. The battery is coming up little by little and my car battery charger of 15 amps can have a break. It was smelling sort of but still working after 3 days. I took some hydro readings and was getting around 1.250 on all cells. They were 1.225 a few days ago. Gotta get the other two solar panels built.... Just not enough hours in the day (sigh)

Kelly