Deep cycle battery charger

MEXICOWANDERER wrote:
Hey BFL, I perused the Power Max 100's and they don't seem to state which ones can hold fixed voltage

Is there a prefix or a suffix that designates a "voltage hold" charger? I'd like to flip through the manual...

Mex, they don't do manual very well. :(

The ADJ models do a "voltage hold" in that they stay at the dialed in voltage until you dial in a different one. They have an external knob for the voltage pot.

They also make/made an "LK" version which has the usual three or four stage, but also can be switched to the ADJ mode when it only does the dialed in voltage. With those you have to get at the internal pot through a hole in the side. The other hole is for the switch. You find LKs on Amazon from boatandrv, but not on boatandrv. Sort of a weird situation, just ignore.

However, you can also get the cheaper, regular PowerMax converter (PM3 or PM4) and take the lid off -drill out the rivets and replace with screws), which exposes the little blue internal pot with its white screw head. You can then dial a particular voltage like 14.8 and it will act like a single voltage at 14.8 until you change that.

There is no difference using a PM3 100 amper where you set the internal pot to 14.8 and the PM3-100ADJ where you dial in 14.8 with its external knob, for how it acts. If you never change that 14.8, but if you often change voltages, the external knob is vastly more convenient of course.

You do have to set the 14.8 with the battery not connected, so you get the right voltage. If you connect up first, the lower battery voltage drags down the voltage you see on the meter, to somewhere between the converter's setting and the battery's voltage.

Set the 14.8, connect, power on, and wait till the voltage you see rises to what you set and you are charged up. Now dial it back to 13.6. That makes it look like something went wrong (no amps or even neg amps) until battery voltage falls to 13.6. Now things get back to normal and look right at steady 13.6. It could be it is not quite at 13.6 because you did that when connected. Just tweak it to 13.6 until it is.

You can beat that by marking your usual voltages around the knob when not connected. That way, when connected you can just dial to the marks and not to the "wrong" voltage seen on the meter.

My 55amper ADJ with marks



BTW I love the 55ADJ for my two 100AH AGMs which spec 27amps max at 14.8. So I set 14.8 for the two at 55 amps and wait till amps are down to under 1 amp (0.5a each) in the Trimetric and then dial it to 13.6 Float. Ta da!