Interesting question. Not sure exactly what's going on with the solar charger, but you might try a different connection point that's closer to the batteries. The diode thing you suggested might work too, as might a higher resistance value for the pre-charge resistor. Your comment about charging the caps being unnecessary doesn't make sense to me. I think that's the whole point of having the pre-charge resistor in the first place - to keep the controller's filter caps charged all the time so you don't arc the power switch every time you turn it on.
You can get away with no pre-charge resistor if your switch is hefty enough. I've run Alltrax controllers for several years on a couple different boats without using pre-charge resistors. There is a significant "pop" when I turn on the main cutoff, which is one of those big round marine battery switches, rated at 3 or 400 amps. With such a beefy switch I think it will take hundreds of cycles for it to erode away enough contact material to make a difference. Switching it quickly probably helps a little too. I'm using 48V, your 24V system should produce even less arcing.
I say try it without the resistor and see if the charging situation improves. That would also confirm your theory about the caps being the culprit.
Let us know what you find out.
Jim
--- In electricboats@yahoogroups.com, "mattelderca" <mattelderca@...> wrote:
>
> Good day all,
> I've been away from this group for a while but I see some of the regular people are still around.
> I have a bit of a puzzle that I just can't seem to resolve in my head.
> It is in regards to precharge of my Curtis type controller and I was wondering if someone here may have a simple answer.
>
> Here is the setup,
> 24 volt solar charged pontoon boat with twin MinnKota's controlled by a Hyundai golf cart controller. ( similar to a Curtis)
> I have a manual battery disconnect (newly added), key switch for the controller on, and reversing contactors after the controller.
>
> Previously I had no battery disconnect so the precharge was done once when the batteries were connected. It served me fine for the last 6 years, but I was always a bit concerned that I had no emergency off.
> We don't need to debate that.
>
> One other problem that came up with this setup was the fact that the capacitors held the voltage high and fooled the solar charge controller into thinking the batteries were charged. They were, just not fully topped off.
>
> Now I am re wiring my controller and have added the manual battery disconnect switch. I know I should have a precharge resistor across that disconnect but I don't want the charge controller to "see" that the caps are connected. I could add a switch to the resistor but that throws another thing to think about before turning on the power.
>
> I have gone over a few possible wiring schemes but wondered what some others may have done and what issues they may have had.
> My final thought is to have a diode in series with the resistor thinking this may keep the caps and batteries separated enough so the charge controller isn't effected. This would keep the caps charged all the time as well, which is not necessary. I would like a scheme that would keep the controller completely out of the circuit until the main disconnect is turned on. But I can't think of an idiot proof way of doing it.
>
> Got any suggestions?
>
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