Interesting, thought provoking possible problem with my on-board charger

Kris · July 06, 2017, 03:11:11 PM

This just happened earlier this week.
A Friend and I went to Piney Run Park to fish for the day. The lake is only 350+ acres and my Minn Kotas don't have a problem running the whole lake. On the way down from the top I started noticing the transom mount, Traxxis, 24 volt, 70 lb thrust was running slower than normal. I also noticed that the bow mount, Edge, 12 volt, 55 lb thrust was a little weak on speed 4.
When I got home I hooked up my three bank, on-board charger that I use like a portable. I also hooked up one of my other chargers to take care of the fourth battery. Out of curiosity I unplugged everything when the on-board lights lit up green. Disconnected the on-board and connected a charger that would read the charge in percentage. First battery tested showed 80%. I hooked the same charger to the studs and the charger showed "Bad Batt". Knowing these batteries are still good i connected the clamps to the battery posts and the charger did its thing to 100%.
This may seem a little far out but here goes:
Both battery chargers were connected to the studs and could not charge the battery sufficiently. When the clips were moved to the battery posts the battery charged up to 100%. Do you think it is possible that the studs have corroded inside and now causing a problem on charging? I think my next move will be to put marine battery conversions on the posts and see if it charges normally. What do you think?

Mike Cork · July 06, 2017, 03:32:05 PM

It could be that your on board charger hits with 10 amps up to 80% charge then drops to 2 amps for the last 20%. At this point it calls it okay to use?

If I'm understanding you right....

I don't see how corrosion could be the issue. It goes to full charge on one charger but not the other. This would lead me to believe it's a charger issue.

bigjim5589 · July 06, 2017, 04:37:59 PM

Is there wire that connects the studs & the batteries? That would likely be the place for a problem, If there's a corrosion issue. I've seen wire corroded inside of the wire insulation, and that can reduce amperage to the batteries. The wires may look fine, but if the wires inside look black or green, then chances are there is internal corrosion on the wires. Corrosion on studs is usually very obvious.

Oldfart9999 · July 06, 2017, 07:03:45 PM

2 goo0d replies!! Hook the onboard up then let it go longer and see what it does.
Rodney

Princeton_Man · July 06, 2017, 07:58:20 PM

Quote from: Oldfart9999 on July 06, 2017, 07:03:45 PM
2 goo0d replies!! Hook the onboard up then let it go longer and see what it does.
Rodney

X2

I agree as well. If your 3 bank charger is a digital (smart charger), connecting/disconnecting doesn't tell the truth. It has to "get to know" your batteries. -J

Kris · July 06, 2017, 09:18:43 PM

I have been using this charger for a couple of years now. It has been hooked up since my last use on Thursday last week. The three indicator lights had turned green indicating fully charged. My automatic charger was on the fourth battery showing 100%. Unplugged the chargers and moved the automatic charger to one battery that was charged with the on board. Onboard connection went to the battery the automatic one was connected to. I plugged the chargers back in and recovered the boat. Two hours later checked on it and auto was showing 80%. Both chargers had been connected to the studs, Trojan SCS225's have both connections. Moved the clamps to the battery terminals and the battery charged to 100%. More tomorrow when I double check the second battery tomorrow.

Princeton_Man · July 07, 2017, 06:51:47 AM

Those batteries have removable caps right? Use a battery hydrometer to test the cells of the battery showing 80%. If there's a weak cell, that will identify it.

You can pick up a hydrometer from any autoparts store for $1-$20 depending on quality. Even the $1 ones work just fine.

BTW, having both chargers connected at the same time is probably not a good idea if either of them are digitally controlled and since the chargers apply charge based on voltage measurement. they'll probably be measuring each other's voltage and not apply a charge.

Kris · July 07, 2017, 07:19:17 AM

No, never connected both chargers at the same time. On the parallel pair I even disconnect the ground link to keep them separate when charging. I know I have a cheap hydrometer in my tool box somewhere and will try and find that. Good idea.
I noticed during my last trip that the boat has never been that slow. Not that the trolling motors are noisey but they were very quiet. I even asked my co-angler if the transom motor was at full. The boat was also quite a bit slower according to GPS.