I had a similar problem in my trailer. When I bought it the previous owner had wired it with an older Magnatec 45 amp charger/12v power supply. One week it decided to start putting out too much voltage, and overcharged and cooked my 2 nice new deep cycle batteries.
Shopped around, and Magnatec is now Parallax, and the equivalent unit is now a 7345. I looked into better things, but rewiring would have been a pain. So they have the 7345RU which is basically just the replacement "guts" for the unit, you just change that out and don't have to rewire the whole mess. Allegedly the newest, greatest, surge & spike free version of the unit. Worked OK for 1/2 a year, then started the same crap all over. Only cooked one battery this time.
Did not change the unit, it seems to be behaving for the most part at that point, but it has really quirky behavior. Seems to work just fine to stay plugged into 110v to keep the batteries charged for standby. During use when we are camping it sometimes does all sorts of strange things. Some days it works fine under any load. Other days if we are only running a few lights it will just let the battery drain until the lights are dim and the fridge shuts off from low voltage then we have to turn on all the lights to get it to start charging, but if we are using more power from the get go it will work just fine. Other days if we are using more lights it will jump back and forth between "normal" and overcharging, as the lights keep going from normal to way too bright and back. But most days it is good.
That is on shore power. If we use a generator, all bets are off and it does all sorts of weirdness, and some days it is tricky to get it to charge the batteries at all.
Any help out there on this similar problem?
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