I have a Basement Watchdog battery powered sump-pump backup system. I have recently been adding distilled water every month or so. I used to go 6 months or so before the attached monitor would indicate low fluid levels.
The FAQ in the web link above indicates that if I’m adding water frequently, then perhaps the battery is being overcharged and might need service. Sending the system in for servicing is a pain-in-the-patoot (I sent it in a few years ago for a different problem).
I have noticed that the battery is very hot when I add the water. Is the water needing replacement because it is boiling away? Would this be due to a bad battery perhaps? Or is it more likely that the charging system is messed up?
Bottom line: I want to know what would cause a 12 volt non-sealed battery to get very hot?
I can’t answer the specific problem, but I can explain this much. All batteries produce heat when in use. They’re using a chemical reaction to produce electrical energy. This chemical reaction gives off heat. Now, obviously, an AA battery isn’t ever being used to produce more than a few milliamps of current - so little that you won’t even notice the heat being produced. The ones you’re dealing with, however, are going to be far more powerful - hence far more heat.
And the don’t-try-this-at-home urban legend - if you get a 24v lorry battery, and put a spanner across the terminals, it gets so hot it bursts open. (I’ve no idea if that’s true…)
No, not really. Some battery chemistries, like lithium-ion, are somewhat exothermic but many, like alkalines, are not (or at least not significantly). Much, if not most, of the heating in batteries is caused by I[sup]2[/sup]R losses due to internal resistance.
I’d guess that your charging system is overcharging your battery, which would cause gassing. This would also cause your plates to overheat, possibly damaging them. Is there a gauge on the charger, so you can observe its output? Presumably, there should be very little activity unless that battery has been discharged…
As I was checking the system last night, the control box (which does not have any guages – just “idiot lights”) is indicating that there is a “battery problem: clean the posts and re-connect; or replace battery.”
I happen to have a spare battery, so here is my plan:
a) clean the battery posts; ensure fluid levels are proper; and re-try
b) if that fails to correct the error warning, I’ll try connecting my spare battery.
This should isolate the problem. If the spare battery works, then my current battery has bit the dust. If the spare battery experiences the same problem, then the control box is overcharging and needs servicing.
My only hesitation is that my spare battery has sat unused for 7-8 years – I don’t know if it’ll charge properly or not.