Dear Ole Mechanic;

I have seen ads on TV for the little battery chargers that are supposed to maintain a battery’s charge while it is in storage.  I wonder how something that small can charge any battery except a little motorcycle or deer-feeder battery.  Are they any good?  Would it keep the battery charged up on my old antique truck that is in storage for months at a time?Battery Maintainer

What is your opinion of the battery maintainers?

Needing Charged


Dear Needing Charged;

The battery maintainers have their place, but there are charging situations that they are not intended to do. First, a little explanation of what they do.  They have an extremely low charging amp rate; it is usually in the one half to two-Amp range.  If you have a battery bigger than a motorcycle battery that is really low or completely discharged, the maintainer will take for ever to charge it up.  The very low charging rate is only intended to bring a mostly charged battery up to a full charge of 12.8 to 13.2 Volts and then simply maintain that voltage by cycling ON and OFF.  If the battery is in good condition, they usually work just fine.

However, one time I had an older battery that was marginal; I was just trying to get another year of use out of it.  I put my maintainer on it and left it ON for about four months.  Then, before I went to use the battery, I checked the electrolyte (water) level, and it was so low that the top of the plates were exposed in two of the cells.  That is not good!  Even with a low charging rate of one Amp, it had boiled about one third of the water out of the two cells.  I tried adding water to the cells, but I still had to go buy a new battery.  As a result of that experience, I now hook up the maintainer about once a month and leave it on for a full day--24 hours.  Then I move it to the next battery in storage and the leave it on that one for a day.  With all my toys (junk), it takes me about a week to get to all of the batteries, and that works fine for the various sizes of batteries that I have from lawn mower size up to tractor size.  Do to my past experience, I check the water level both before and after storage.  I find that the maintainers work very well on computer-equipped cars and trucks.  The computer memory draws anywhere from 100 milliamps to 500 milliamps with the key OFF.  Even that small a draw will usually run a battery down in from one to three months.  By putting a maintainer on for a full day once a month, I do not have a dead battery when I go to pull what ever it is in out of storage. 

The maintainer I have has two lights: a Red one which comes on when the unit is plugged into a wall socket, and a Green one that is ON all of the time it is charging, but flashes when it is in the maintain mode.  Sometimes the miniature electronics can be a good thing. because that's what senses the 12.8 to 13.2 Volts and then cycles ON and OFF to maintain that charge.  It makes a very smal,l handy package.  It also prolongs the life of those expensive batteries.  I have one that is now eight years old, and it is cranking my old pet tractor just fine.  I also have a motorcycle battery that is six years old.

OK, now for the short version.  The battery maintainers work fine; just check the water level regularly.

Herr Professor Nuzanbolts