Batteries Over Charging?

[MtB]

1 hour ago, ditchcrawler said:

It may be possible to get it refurbished, we did the fork lifts when they went down, just a single cell if the others are still OK

 

Yes I was thinking the same. I'd imagine a 2V traction cell could be taken to pieces and the shorting material/sludge cleaned out, then it all put back together again. 

[Tracy D'arth]

The specific gravities of the cell has been compromised by some of the electrolyte being removed. Perhaps the cells were topped up when they were not charged.

The readings may therefore be erroneous.

Cells will make water as they charge until they are fully charged. 

[Tony Brooks]

9 hours ago, Tracy D'arth said:

The specific gravities of the cell has been compromised by some of the electrolyte being removed. Perhaps the cells were topped up when they were not charged.

The readings may therefore be erroneous.

Cells will make water as they charge until they are fully charged. 

 

I think that you have that back to front. Cells remove sulphur from the acid as they discharge, so the acid gets weaker and put it back into the acid as they charge.

 

If they are gassing under charge, then they are losing water unless they have a catalytic breather system, then they do "make" water, but it is only water that has been lost to gassing in the cells, so no overall gain.

[nicknorman]

1 hour ago, Tony Brooks said:

 

I think that you have that back to front. Cells remove sulphur from the acid as they discharge, so the acid gets weaker and put it back into the acid as they charge.

 

If they are gassing under charge, then they are losing water unless they have a catalytic breather system, then they do "make" water, but it is only water that has been lost to gassing in the cells, so no overall gain.

I think there’s a bit of confusion going on. The OP said he had removed 300ml of electrolyte from each cell. This will have removed some acid. But if the same amount was removed from each cell, and no water added since, one would still expect the sg to be much the same for all cells.

I think Tracy’s point about making water is that the level of electrolyte lowers as the battery discharges, and rises again as the battery is charged, due to the changing chemical composition. This is why battery electrolyte levels should only be checked and adjusted when the battery is more or less fully charged.

[cuthound]

12 hours ago, MtB said:

 

Yes I was thinking the same. I'd imagine a 2V traction cell could be taken to pieces and the shorting material/sludge cleaned out, then it all put back together again. 

 

We used to do this regularly with 2 volt batteries when I worked for BT.

 

The easiest cells to work in were the open, lead lined wooden box cells, were even individual plates cut be cut out and new or refurbished ones welded back in.

 

Too big to be practical for a boat though.

1 hour ago, nicknorman said:

I think there’s a bit of confusion going on. The OP said he had removed 300ml of electrolyte from each cell. This will have removed some acid. But if the same amount was removed from each cell, and no water added since, one would still expect the sg to be much the same for all cells.

I think Tracy’s point about making water is that the level of electrolyte lowers as the battery discharges, and rises again as the battery is charged, due to the changing chemical composition. This is why battery electrolyte levels should only be checked and adjusted when the battery is more or less fully charged.

 

Perhaps Tracy was thinking of VRSLA's (AGM's etc), which are recombination cells, where any electrolyte is trapped in an absorbent mat. The oxygen and hydrogen evolved during charging is recombined into water to recycle the electrolyte. 

 

Totally irrelevant though as the OP has flooded cells.

[Tracy D'arth]

1 hour ago, cuthound said:

 

We used to do this regularly with 2 volt batteries when I worked for BT.

 

The easiest cells to work in were the open, lead lined wooden box cells, were even individual plates cut be cut out and new or refurbished ones welded back in.

 

Too big to be practical for a boat though.

 

Perhaps Tracy was thinking of VRSLA's (AGM's etc), which are recombination cells, where any electrolyte is trapped in an absorbent mat. The oxygen and hydrogen evolved during charging is recombined into water to recycle the electrolyte. 

 

Totally irrelevant though as the OP has flooded cells.

No, Tracy was getting at the fact that the level will rise as a flat battery charges. Never top up a battery unless it is charged quite well.

[steve.sharratt]

2 hours ago, Tracy D'arth said:

 

 

3 hours ago, cuthound said:

 

 

5 hours ago, nicknorman said:

 

 

6 hours ago, Tony Brooks said:

 

I have charged the batteries to 100% then disconnected the charger (in case the AC in influenced the readings).  I made a small table to show the results:

 

Battery	1	2	3	4	5	6	7	8	9	10	11	12
Voltage	2.116	2.122	2.095	2.063	2.097	2.097	2.092	2.089	2.095	2.081	2.080	2.081
SG	1225	1250	1225	1220	1250	1250	1225	1250	1250	1225	1225	1250

 

You can see that battery 4 looks questionable.  Voltage variation is well under 0.1 so on the surface that would appear ok.  The SG variation is more of a concern with Battery 4 being lower that preferable.  The interweb tells me that 25 is the acceptable variable limit and number 4 pushes it to 50.  Regardless, all of the SG is sitting on the low side of good so I suspect I am up for some new batteries. 

 

I wanted to avoid this for a while but maybe it’s time for LiFePo4.  I can buy one battery that will give comparable usable amps (around 300) that is already fitted with BMS and is friendly all for und £2000.  I don’t think I could do much better with replacement traction.  And I won’t have to drop a dozen forklift batteries through the hatch!  

 

15 hours ago, MtB said:

 

 

[Tony Brooks]

7 minutes ago, steve.sharratt said:

 

 

 

I have charged the batteries to 100% then disconnected the charger (in case the AC in influenced the readings).  I made a small table to show the results:

 

Battery	1	2	3	4	5	6	7	8	9	10	11	12
Voltage	2.116	2.122	2.095	2.063	2.097	2.097	2.092	2.089	2.095	2.081	2.080	2.081
SG	1225	1250	1225	1220	1250	1250	1225	1250	1250	1225	1225	1250

 

You can see that battery 4 looks questionable.  Voltage variation is well under 0.1 so on the surface that would appear ok.  The SG variation is more of a concern with Battery 4 being lower that preferable.  The interweb tells me that 25 is the acceptable variable limit and number 4 pushes it to 50.  Regardless, all of the SG is sitting on the low side of good so I suspect I am up for some new batteries. 

 

I wanted to avoid this for a while but maybe it’s time for LiFePo4.  I can buy one battery that will give comparable usable amps (around 300) that is already fitted with BMS and is friendly all for und £2000.  I don’t think I could do much better with replacement traction.  And I won’t have to drop a dozen forklift batteries through the hatch!  

 

 

 

How did you assess the 100% charged? If it was from an Ah counter then they are known to lie and the Smartguage is not accurate during charge and until a little electricity has been used. The relative densities do not look fully charged to me because typically that will be between 1.275 and 1.300. Your overall low readings, if the batteries are fully charged, is probably down to sulphation. Can you do an equalisation chargee to see if they get better readings?

 

 

[steve.sharratt]

8 minutes ago, Tony Brooks said:

 

How did you assess the 100% charged? If it was from an Ah counter then they are known to lie and the Smartguage is not accurate during charge and until a little electricity has been used. The relative densities do not look fully charged to me because typically that will be between 1.275 and 1.300. Your overall low readings, if the batteries are fully charged, is probably down to sulphation. Can you do an equalisation chargee to see if they get better readings?

 

 

Correct.  I used the Victron VRM to tell me that they were 100%.  I was aware that I should have allowed some settling but I live aboard and ‘stuff’ is using power!  I’m not sure how to do an equalisation charge with a Multiplus but I’m looking on the interweb now.

[Tony Brooks]

14 minutes ago, steve.sharratt said:

Correct.  I used the Victron VRM to tell me that they were 100%.  I was aware that I should have allowed some settling but I live aboard and ‘stuff’ is using power!  I’m not sure how to do an equalisation charge with a Multiplus but I’m looking on the interweb now.

 

The VRM seems, from a quick Google, to only be an interface for the battery monitor, so it will tell the same lies as the monitor. If you are 100% sure it has been set up correctly, the set-up has been kept up to date AND it is very regularly re-synchronised then the reading is probably accurate enough for your purposes, but if those conditions are not met we are back to misleading output.

 

If this were mine, I would charge from the alternator whilst monitoring the charging amps. (the amps and volt readings are accurate). Keep charging until the current reads 1 to 2% of battery capacity with a voltage in excess of 28.4V. HOWEVER, as it looks as if you have a shorting cell this is not now an option, but is something to bear in mind if you get a new cell(s) dropped in.

 

You may well ask "why alternator" when you have a battery charger. The answer is simple, most modern "smart" chargers drop into float far too soon so there is every possibility the batteries never reach 100% charged. The vast majority of alternator do not drop into float voltage at all so will fully charge the batteries - and then some if you keep running, which very few people do.

[cuthound]

2 hours ago, steve.sharratt said:

 

 

 

I have charged the batteries to 100% then disconnected the charger (in case the AC in influenced the readings).  I made a small table to show the results:

 

Battery	1	2	3	4	5	6	7	8	9	10	11	12
Voltage	2.116	2.122	2.095	2.063	2.097	2.097	2.092	2.089	2.095	2.081	2.080	2.081
SG	1225	1250	1225	1220	1250	1250	1225	1250	1250	1225	1225	1250

 

You can see that battery 4 looks questionable.  Voltage variation is well under 0.1 so on the surface that would appear ok.  The SG variation is more of a concern with Battery 4 being lower that preferable.  The interweb tells me that 25 is the acceptable variable limit and number 4 pushes it to 50.  Regardless, all of the SG is sitting on the low side of good so I suspect I am up for some new batteries. 

 

I wanted to avoid this for a while but maybe it’s time for LiFePo4.  I can buy one battery that will give comparable usable amps (around 300) that is already fitted with BMS and is friendly all for und £2000.  I don’t think I could do much better with replacement traction.  And I won’t have to drop a dozen forklift batteries through the hatch!  

 

 

 

There is a significant variation in specific gravity readings between cells.

 

You need to charge them until each one is  2.66 volts per cell and monitor the current until it has remained constant for at least 30 minutes. The SG's should thden be within 0.005 of each other. Only then will the battery be at 100% charge.

[steve.sharratt]

15 minutes ago, cuthound said:

 

There is a significant variation in specific gravity readings between cells.

 

You need to charge them until each one is  2.66 volts per cell and monitor the current until it has remained constant for at least 30 minutes. The SG's should thden be within 0.005 of each other. Only then will the battery be at 100% charge.

I am trying to do that now.  The batteries have been at 100% (according to the monitor) for 1hr &1/2 and it it still sitting on bulk.  Charging voltage seems to be slowly creeping up. Currently at 27.03v.  My biggest concern is that as soon as the monitor reads 100% the smell becomes quite strong.  I now have a fan at the top of the engine room steps to see if it will help.

[steve.sharratt]

Well it has taken a while but I think I have had some results.  I charged the batteries to full (float).  It sat on Absorption for over 9 hours but I persevered and found that the bad smell progressively disappeared.  The Absorption voltage of 28.8 was not achieved immediately - it took several hours.  When it did achieve the correct voltage everything seemed to settle down.  When it finally went to Float The voltage correctly dropped to the 27.6 float voltage.  So everything seems to be doing what it should.  I left it overnight and the ran the Equalisation mode.  Again, everything seemed correct. Voltage was 29.something - it stayed on for 1 hour and then dropped back to float as per the manual.  

 

I switch off all power for 1/2 hour and then did the voltage and SG tests.  Chart below.

 

Battery	1	2	3	4	5	6	7	8	9	10	11	12	Avg	Var
Voltage	2.158	2.161	2.149	2.127	2.154	2.155	2.152	2.152	2.154	2.144	2.143	2.145	2.150	0.034
SG	1270	1275	1260	1250	1265	1265	1265	1260	1270	1260	1260	1260	1263	25.000

 

Number 4 still seems to be the weak link but according to my research voltage variation for a resting battery should be less than 0.05v. 0.034 is my result.  SG is within the 100% charge range and 25 is just on the boundary of acceptable variation.  To my mind, everything is now fine (unless you guys tell me otherwise).  Not sure what happened to cause the boil over and the days of rotten eggs, but it seems to have clear itself.  Perhaps the 9 hours + of Absorption helped to clear the pipes?

 

Cheers to everyone for your help and I hope you all see this as I couldn’t work out how to link you all to this message.

[Alan de Enfield]

Maybe it is the 1st time you have ever properly charged the batteries - you now just need to do the same every couple of days, with a longer charge at weekends.

[dmr]

If you do a bit more equalisation then you might get that weak cell up even higher, harder sulphation can take a bit of shifting.