trickle charger current

Lead acid batteries float at a constant voltage (as noted above), not at a constant current. A charger which forces a fixed amount of current, like 1/2 amp, through a lead acid battery will eventually overcharge it unless the available current is less than the leakage current. In this case, the charger will serve to offset some of the self discharge and keep the battery charged longer.

Lead acid maintenance chargers need to set the float voltage and let the battery draw whatever current it takes at that voltage (up to the maximum the charger can supply). This is just like the charge system in an automobile, which regulates at a fixed voltage, and only limits charge current to what the alternator (or generator) can supply without overheating.

On the other hand, NiCad batteries like are used in most cordless tools float at a constant current, which is why they can be left on a simple current limited trickle charger (like a wall wart) indefinitely.

Keith

Furthermore, many of them are "high frequency", which impose a high frequency pulse along with the DC, which is reputed to prevent battery plate sulfation, and even to partially restore batteries that have begun to sulfate.

I have about a half-dozen of them on various tractors and vehicles, including 2 on a 24-Volt Deere 4020. Over several years, I've had not trouble with the chargers, and very good results from the batteries with their use.

Extended battery life, and quick, easy starts of seldom-used equipment make them very usefull things to have!

I tend to be overly cautious, and make sure they are installed well away from anything burnable, and I install a 5 Amp fuse in-line with the battery connection, as some are in use at a remote location, where I may not even check on them for a month or two, and I want to be as safe as possible in the event of any failure as they age.

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They're Chinese, unfortunatly, but that's how it goes nowadays. I suppose some others will chime in about the more "upscale" brands.

However, they readily available, and are not very expensive, and, so far, have been doing the job for me. The units run cool, and I have not noticed any signs of the batterys being overcharged, pushing out electrolyte.