General > General Technical Chat
12V lead acid battery question...
PwrElectronics:
Spring weather finally arrives in my area. :) So, break out the mower. :-\ Turn key, and its dead of course... >:(
I got my old time charger (the sort with a transformer, rectifier, circuit breaker, and ammeter w/o anything else or smarts, etc).
Connect it up. No current is initially drawn. Then, slowly the current rises, and rises, and rises! Eventually pegs the ammeter and then the circuit breaker trips. It has an auto-reset breaker so it came back on and did the same thing. Let it go a few times before I disconnected it.
I then checked the battery voltage with my DMM and it was something like 2-3V.
I went and got a current limited DC bench supply from my home lab and set that for about 1-2A. It did not take too long before the supply switched from CC to CV (supply set at 13V). Took off the supply and checked the battery voltage. Now at something like 10-11V. So, I put the bench supply back on and left it for about 30 minutes. I then removed it and put the battery charger back on. Charger is now sourcing ~5A with applied voltage about 15V. Left that on for another 20min or so.
Removed charger and tried to start the mower. Success! I ended up mowing for a while before other problems cropped up (failing belt) but was able to restart it a couple of times OK.
I guess I will find out in a week or 2 but wondering if this battery is EOL ? Years ago, remember a battery in my winter car (that sat all summer) was dead and took no charging current. But, for fun I left the charger on it for a few hours and when I checked it later it was taking a charge. That battery went on to last a couple of years longer.
Benta:
And the question is?
Stray Electron:
OP That sounds like a nice problem to have. The OP must be somewhere in the northern US where they don't use their mowers for months on end. Here we mow at least every other week, even in the winter. By the end of summer, we mow twice per week.
Get a Battery Tender or some other small regulated 12 voltage power supply and leave it connected to your battery over the winter. Problem solved.
You're lucky that your battery recovered and you didn't have to buy another one!
PwrElectronics:
--- Quote ---The OP must be somewhere in the northern US where they don't use their mowers for months on end.
--- End quote ---
Yes, upper midwest/west abt 270km south of the US-Canada border. Mowing season runs from usually mid May to mid October.
For sure hoping to not need a new battery just yet. Cost of even small batteries has gone up considerably the past few years.
I was just surprised at the behavior here as I have not seen this before. The more modern chargers would not even attempt to charge this as they shut down if the target battery is "too dead".
David Hess:
When a lead-acid battery is discharged, the lead and lead-oxide is converted to amorphous lead sulfate. If left for too long without recharging, the amorphous lead sulfate crystalizes and becomes high impedance. This is what happened to your battery.
A battery in this state may start charging after a while, however it will remain severely damaged and have a short remaining operating life. Plan on replacing it soon.
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