Are these batteries dead?

[samuk]

 Hi

I got hold of some old forklift batteries. I was told they were fully charged and therefore let them stand for a couple of months. I have just checked them and they are flat as a pancake. (I am kicking myself)

I realise that they are probably now sulphated and beyond repair but I want to try to stick a charge into them just to make sure.

I have a new charger that I have never used before and is quite complicated. I am unsure if I am getting any charge into the cells.

I have connected 12 batteries to create a 24v bank. I have connected my charger. Two lights flash which indicate "the charger operates in equalize mode" This mode is described as "The multi plus will charge with increased voltage for one hour (2v for 24v battery). The charging current is then limited to 1/4 of the set value.

The charger has been flashing these two lights for over four hours.

When I measure the voltage across the battery terminals they show 1.9v (the same as they did before) I would expect that they would show higher than this when actually connected to the charger ?

Am I correct that even with severely damaged batteries, you would expect to see 2.6v across each cell whilst the charger is actually connected?

The charger is similar to this (exact same manual does not appear online)

http://www.victronenergy.com/upload/documents/Manual-ML-MultiPlusIn.pdf

The image at bottom of pg 12 describes the state that the charger is in.

[ghurd]

They are not big on explaining much.

Might try Forced Absorption.

Might try a simple battery charger to get the voltage up.  

Some chargers have a safety feature and will not put out amps until the voltage reaches a minimum, and I expect it is about 18~20V.

I would not kick myself over it.  A couple months should not get them down that low.

Sounds like they were scrap when you got them.

G-

[Flux]

I tend to agree with Ghurd, they were probably scrap when you got them.

You don't need fancy complicated chargers for that type of cell, you just need something to shove lots of amps into them until they are boiling. Even working properly clever multistage chargers will not deal with them effectively unless it is a pretty big charger and you have got the batteries into some sort of reasonable condition.

Flux

[Jeff]

A battery that size (all you said was "a fork lift battery") is probably.....well, let's say more than a couple hundred amp-hours. Closer to 1000 amp-hours. With something that size, even charging at C/10 could take a good 24 hours.

From reading the manual and your post, your only charging at 1/4 of the full output of the charger. Even if this charger is capable of 70amps max xharging, that's only 17.5 amps. Again, with a battery that size at that 17amp charge will take a long time. Be patient, let it charge a couple days, and use a good specific gravity checker.

If they are that low to start with, it will take a while also before you start seeing more than 2.2volts per cell.

[Flux]

Looking at your post a little closer, yes something is obviously wrong. Equalising volts for 24v is near 30v. If you are seeing 1.9v per cell with the charger on then there is no way it should be showing the equalising lights.

First step treat the charger as brain dead and stupid and actually check that it is producing current with a real ammeter in the line, I suspect it is doing nothing.

With a decent current flowing you should see a voltage rise across the batteries, if they are dead flat and good it will take a fair while to see the volts rise but it must do so in the end. If the cells are sulphated then the volts will rise quickly and you shroud get up to 2.5 v or more with the charger set for equalising.

Symptoms of the modern age I suppose, a battery charger must have a computer in it, but the basic essential of an ammeter to show what it is really doing seems too much to provide.

Flux

[samuk]

Hi all thanks for your comments.

I discovered that one of the cells was completely knackered. I replaced that cell and there is charge going into the batteries now.

I will let you know how I get on..

Thanks

Sam

[elt]

ghurd wrote:

> Might try a simple battery charger to get the voltage up.

Thank yoU! I've desulfated an abused battery for about a month but my "smart" charger still wouldn't charge it ... I put my "simple" charger on it and now the volts are up and the battery is taking amps.

Thanks again,

 - Ed.

[ghurd]

Keep checking it for a day or 2 too.

Sometimes the 'smart charger' will decide it is too low again and kick back off.

Might even keep both chargers on for a while, if the simple charger amps are kind of low compared to the battery AH.

Nothing like thinking it is charging for 3 days when it isn't, then having to start over.  Grrr.

G-

[samuk]

Hi All

FYI there is 1000 amp hours of batteries. They are split into 4X 500ah sections. I have  charged one of these 500ah sections for 2 hours at 30volts. The charger drew about 1.5kw from the mains.

I then charged them at 28.8volts for about 12 hours.

They now show 2.1volt across each cell. I believe they should be 2.4v.  Is it worth trying 30v charge for a little longer?

Thanks

Sam

 

[samuk]

OK I have charged these at 30volt for 2 hours and then 28.8v for about 14 hours. They now show 26v across a open circuit.  The 3 stage charger has now stopped putting the 'bulk' charge in and is just putting in a absorption charge. The charger is only drawing 90watt at 240v (0.375 amp) I assume this means it has gone into 'float mode'.

I now plan to

1. Leave the batteries to stand to 6 hours.
   
2. Take the voltage of each cell and record it.
   
3. Draw 500w from the bank for a few hours.
   
4. Take the voltage of each cell and record it.
   
5. Replace any cells where the voltage has dropped proportionally more than the other cells.
   
6. Recharge the bank again and repeat 2) -6)
   
   

I have read that "SLA batteries with mild sulfation can be restored but the work is time consuming and the results are mixed. Reasonably good results are achieved by applying a charge on top of a charge. This is done by fully charging an SLA battery, then removing it for a 24 to 48 hour rest period and applying a charge again The process is repeated several times and the capacity is checked with a final full discharge and recharge." http://www.batteryuniversity.com/parttwo-35.htm

Would this also apply to flooded cells as well as the Sealed cells mentioned? It it worth trying?

Thanks

Sam