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Old 10-10-13, 08:18 AM   #301
MetroMPG
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I think it's theoretically possible, but you'd have to tap (through the case) the electrodes of the middle cell(s) to re-charge them. But I don't know how healthy the battery would be after this.

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Hate to hit a man when he's down.. but you shoulda been monitoring each battery while mowing!! If you're not running a management system, it's the only way to prevent battricide.

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Old 10-10-13, 08:25 AM   #302
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If they are floodies, check the water level first and then see if you can equalize charge them.
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Old 10-10-13, 08:29 AM   #303
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Quote:
Originally Posted by MetroMPG View Post
Hate to hit a man when he's down.. but you shoulda been monitoring each battery while mowing!! If you're not running a management system, it's the only way to prevent battricide.
Yeah, I know. Ive known for quite a while (which you know haha). What is worse is that I have a 4 battery monitor and I just never have hooked it up.


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If they are floodies, check the water level first and then see if you can equalize charge them.
They are floodies. I checked the water level not long ago and they were good. I'm 99% sure an equalizing charge won't undo a reversed cell.
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Last edited by Daox; 10-10-13 at 08:33 AM..
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Old 10-10-13, 08:37 AM   #304
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Some quick googling comes up with this:

Reversed polarity cell in Lead Acid Batteries Forum


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Normally cell reversal occurs when a weak cell goes to zero volts and the continuing load induced current through the cell places a reversed charge on the cell.

This is ONE of the reasons you are NOT supposed to take a 12V batt below 10.5V.

Recovery procedures are to run the entire battery down with a VERY LOW load (100 ohm to 1K resistor) untill the battery zeros out. Then recharge at VERY LOW charge rates (0.1 amps) while pulsing (0.050 amps pulser, 0.050 amps charge).

I have had some successes using this technique.
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Old 10-10-13, 02:06 PM   #305
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Using my electric tractor seemed to work very well, when I added a mower deck it got hard on batts. Am using old batts and run them through desulphation for a few months every year, have blown two 6V golf cart batts using the mower. Tried putting a small 24V batt just for the mower, but that did not seem to work very well. When my ship cometh in I am gonna buy a new set of 4 for tractor & a set of 6 for the coach. 'Till then will buy rum and not worry about the batts.
Note to self; check water levels monthly.
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Old 10-10-13, 03:04 PM   #306
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Yeah, tooling around on the mower only pulls 15-25A. The mower deck pulls another 60-90A depending on the grass you're cutting. On average I'd say I'm pulling just under 100A while mowing.
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Old 10-11-13, 08:57 AM   #307
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100A! Wow! I pull around 50A on my E15 Elec-Trak and I thought that was high (it goes higher through tall, tough grass if you don't slow down, but I try to keep it at 50A or less on average). Its a 36V system, really not high enough. Are you running 24V?

Unfortunately, I know from experience about this. Put a resistor (a light bulb works great) in series with your bad battery and charge it separately until the voltage comes up to a more 'normal' range. Then you can take the resistor out and charge with a normal charger. The reversed cell will re-reverse. The damage has been done, however, and that cell will never recover its full capacity. To get the battery charged again, the one cell will charge normaly, but the undamaged cells will be overcharged every time. Therefore the life of that one battery will be much shorter, and the capacity of that one battery is limited to that of the damaged cell. Naturally, this brings down the entire pack's capacity to that same point.

I just recently had one battery go bad on the ET in the same way - one bad cell had a lot less capacity than the rest, so it tended to get discharged further than all the others every time until it finally would reverse while mowing. You could feel it and hear it in the motors, even a 2V overall drop is very noticeable in a 36V system. Eventually it would not come back. Fortunately, my local battery place sells "blems" - lightly used, reconditioned batteries - for only $45, so I got one of those to replace it. You will likely only be able to wring enough extra life out of that battery to last til you can buy yourself a used one to replace it.
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Old 10-11-13, 09:27 AM   #308
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Well, I think it something like that. I had an older ammeter and it read around 90A-110A while cutting grass. My new ammeter (old one took a dump) reads lower than that, more like 75A-90A while cutting. I'm not sure which one to trust. I do have a lot more belts and things than you do, so I have more losses that way. But, I am running a 48V system though, so that should reduce amp draw vs 36V.

I charge all my batteries separately via four Soneil chargers. Thats why I'm surprised this happened.
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Old 10-11-13, 10:10 AM   #309
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Have you tried to charge the battery to see if it rests at a normal 12.6+v after the charge to see if it survived or are you just declaring it dead because you drained it dry(and then some) once? Lead-acid batteries in general live short lives and its not uncommon to have an unexpected loss in capacity or otherwise early death. Even if you stopped the discharge before the voltage was pulled super low in the cell, the problem of a low capacity cell or two would most likely still be there just as it would be if it charged up okay for you to use it again. Seems to me that no matter how you look at it, this lead-acid battery took one for the team and will need to be replaced. I strongly support lithium but can see where its tough to justify its cost for a lawn mower especially when the cycle count is low and the expected life is generally expected to be higher because of that. I'm considering roughly a 1kwh LiPo pack to power my lawn mower, snow blower, and any other power tool using a 120v universal motor getting year round use out of it but $300+ is a tough pill for sure but I expect it would cover my full 1/4 acre lot of mowing and be plenty to chew through a driveway of about 9 inches of snow in one charge.

What do you plan to do going forward? Replace the bad 12v lead-acid battery with another?
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Old 10-11-13, 10:49 AM   #310
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I'll see if I can't fix it somehow. If I can, I'll see how it holds up. Its working as is right now, my run time is just lower. If I can't fix it, I'll replace it.

Lithium would be great, but we're talking around $1500-2000 for as much capacity as I would need/want (~16S, 100Ah). Then I'd have to look into a new charger too.

The low cycle count is the key here, I think lead will continue to work fine. I just really need to get that battery monitor hooked up so this doesn't happen again. I will be doing that sometime this fall. I still have to replace one of the chargers that went kaput on me too. I have the new charger, just haven't installed it yet. I'll take care of em both at the same time.

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Last edited by Daox; 10-11-13 at 11:02 AM..
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