I just procured an ATV which hasn't run in some time, and the first thing I did was checked the battery, and it reads NEGATIVE eight volts. I have never seen that in a lead acid battery before. Naturally I was apprehensive to hook the charger up to it. Is this battery totally junk, or can it simply be depleted and then charged the right way? The vehicle in question is about four years old and only has a few hours on it (bought for a girl who never rode it).
Dog arms wrote: "I just procured an ATV which hasn't run in some time, and the first thing I did was checked the battery, and it reads NEGATIVE eight volts. I have never seen that in a lead acid battery before. Naturally I was apprehensive to hook the charger up to it. Is this battery totally junk, or can it simply be depleted and then charged the right way? The vehicle in question is about four years old and only has a few hours on it (bought for a girl who never rode it)." *************************************
Steve W wrote: "Toss it. Reverse polarity means it is toast." *********************************
Thank you for your response. I guess I have a couple more questions, if you don't mind.
1). Is the ONLY way the battery could be in this condition, is from someone hooking a charger up backwards?
2.) Is it possible / probable that any other electrical systems (charging, ignition etc) on this ATV are damaged or fried, from this situation?
I beg to differ.. My wife had a Fiat 131 when we lived in Venezuela that developed some other problem... I had to take the battery out to fix the other situation. When I put it back in, + to + and - to -, shit erupted. It had been installed backwards for a long time. I discharged it, and then recharged it with the appropriate polarity.. No problem.
I wouldnt have believed it, but this is true. The battery NEVER gave a hiccup and we sold the Fiat a year or two later.
Looks like he's got reverse polarity in four or five of the six cells and one cell doing nothing (perhaps internally shorted). The possibility of one or two shorted cells makes this worth scrap but, if there's time available it might be worth a try to salvage it.
Back in the early days of 12 volt batteries in passenger cars (with exposed lead straps between cells -- circa 1953-1955) this was a common happening as acid venting to the top of the battery would cause irregular current flow between different cells during the charge/discharge process. Charging current would then flow backward through some cells and cause them to reverse polarity. Battery folks caught on in the late 50's and started embedding the straps in the asphalt sealant.
Also, discharging a battery to a point where the individual cells are no longer 'similar' in their internal resistance can cause a cell to reverse when charging.
Agree with the idea of fully discharging the battery. This might require a couple of days and three or four discharge attempts. Take it all the way down, then remove the load for a couple of hours, then discharge again etc.
Start charging with a very low current for a just a few minutes. Remove the charging current and check the no-load voltage for something above
10.5 VDC. If you get that, apply full charging current for a half-minute and check the no-load voltage again. If it hasn't dropped below 10.5 volts, go ahead and slow charge the battery for a few hours then go on up to a normal charging rate and finish with a topping charge.
If the battery, once fully discharged, won't maintain cell polarity then it's, 'open the wallet time.'
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