Battery Maintainer - Installed (w/ pics)


Well-known member
Steel Soldiers Supporter
Davis County, UT
I read a lot of posts around Steel Soldiers about various battery chargers, trickle chargers, and maintainers. Many of them arguing the best solution of either dual 12v or single 24v charging.

I feel that the best comment in this continuing debate was made by steelypip:

Note that all the cells (nominal 2.0 volts) are in a string together.
Because they're in a string together, if a current passes through one cell, the same amount of current passes through all the cells. There's no difference between the first and last cells in a string as far as current availability is concerned.

Chances are good that the cells do not charge and discharge identically. When charging, it is important to charge the battery until the most discharged cell is fully charged. The 'right' way to do this is to measure the specific gravity of each cell with a hydrometer during charging, and when the lowest cell reports a 'fully charged' specific gravity, you're done. It's a pain, and almost nobody does it.
So my opinion was that if you charge the batteries individually, you're still subjecting all 6 cells to the conditions of the weakest cell. So I see the disadvantage of charging both batteries together is that you're subjecting both of the batteries to the cumulative weakest cell.

I decided that for me, ease was the best solution, as I didn't want to disconnect the "dog bone" between the batteries each time I parked the truck for a few weeks, and I knew that I wouldn't anyway. I'd rather do possibly suboptimal charging than let my laziness kick in and do no maintaining at all.

I picked up a 24v Battery Tender from Amazon for about $75.00
Some of the features Battery Tender promotes about this particular product is that it's waterproof (but still warns about not exposing it to rain? odd), fully mountable, and vibration resistant.
I then used the following stainless steel hardware:
Four 10-32 x 3/4 Pan Head screw, $0.37 ea
Four 10-32 nylon lock nut, $0.55 ea
Four #10 washer, $0.17 ea
Four 5/32 x 7/8 fender washer, $0.45 ea (placed these on the tire side of the sheet metal)

In retrospect I wish should have used the 1/2" screws, but an extra 1/4" shouldn't matter any - maybe a spot for dirt to collect...

I liked the idea of keeping the battery tender installed on the truck, and I looked at various positions of it being installed inside the cab, but ultimately settled on putting it in the battery compartment.

I installed the Battery Tender while I had the battery box removed for a battery disconnect installation:

Inside the battery compartment there were only about 3 places you could put the battery tender, upside down on the underside of the cab floor, on the truck frame, or on the front sheet metal that separates the compartment from the wheel well.

Ultimately I'm really pleased that I put it on the front sheet metal. Even though the Battery Tender may see more vibration in that spot, I can see its display LEDs very well and can monitor the reported charging/maintaining so much easier. The little booklet that came with the Battery Tender is now part of my truck's papers, to remind me what the different LED light states mean.

I also plan on picking up a couple extra 7.5 A fuses to store on board since there are two of those fuses on the Battery Tender cables.


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