Battery issue or Charger issue?

[vandamit]

I have a 3 battery set up with a Minn Kota 330D charger in my boat. 2 Trolling motor batteries and one Cranking battery. The only thing running off my trolling motor batteries is the trolling motor. Everything else runs off the cranking battery. I unplug

the trolling motor when i back in the garage so it doesn't have anything drawing from it. When i charge the batteries they all get full, then within a week i would guess the trolling motor batteries are below 50% and take a couple hours to charge again. The cranking battery is down some as well but not as much as the trolling motor batteries even though it has a radio and fish finders plugged in. The cranking battery is 4 years old, the trolling motor batteries are only 2 years old. What is draining my trolling motor batteries down? Could the cranking battery some how be going bad and drawing power from the trolling motor batteries thru the charger some how? I charged them last night and unplugged them at full charge. this morning the Cranking battery showed 12.49 volts and the trolling motor batteries showed 12.8 volts although they were down already according to the charger. This is driving me nuts, i would love some opinions on what you guys think might be happening.
thanks in advance,
travis

[Spidergrub]

Main power switch left on, power switch to power poles/talons, lighting in a hatch. Some trolling motors will pull power if not disconnected from battery Cranking battery is getting a little old

[vandamit]

Key is out of the main switch so it's not on, don't won power poles. All lighting and everything are hooked to starter battery. The trolling motor batteries that are draining and only for the trolling motor and it's unplugged. only other thing it's even connected to is the charger?

Main power switch left on, power switch to power poles/talons, lighting in a hatch. Some trolling motors will pull power if not disconnected from battery Cranking battery is getting a little old

[Murph McB]

Give them a full charge, remove the leads from the charger. Leave them like that for a few days. Hook ‘em back up and see if they are drained. Should be able to isolate the problem that way

[vandamit]

is the MK330D an acceptable charger to leave plugged in 365 24/7? This has always scared me but i believe it's designed to do that?

[DougL58]

is the MK330D an acceptable charger to leave plugged in 365 24/7? This has always scared me but i believe it's designed to do that?

I leave mine plugged in. 7 years now, no issues.

[vandamit]

i'm seriously thinking about keeping mine plugged in 24/7 since it's made for that. That scares the crap out of me but it's probably the best way to go?

[Ann-Marie]

I don't think the situation is as bad as you think. You said "this morning the Cranking battery showed 12.49 volts and the trolling motor batteries showed 12.8 volts"
When the batteries are idle like that 12.8 is fully charged. But when charging is in progress fully charged is around 14.2 volts. So the trolling batteries were still fully charged.
If you connect a charger to a fully charged battery it will still try to charge it from 12.8 up to 14.2 and then maintain around 13.6 depending on the charger and settings.
Your indication of how long it takes to get it back to full charge is a better guide based on past experience.
As batteries get older they lose capacity. If capacity is lower it takes less charge to fill them up so the length of time to charge gets shorter. Spending a long time suggests batteries in good condition.

[vandamit]

I don't think the situation is as bad as you think. You said "this morning the Cranking battery showed 12.49 volts and the trolling motor batteries showed 12.8 volts"
When the batteries are idle like that 12.8 is fully charged. But when charging is in progress fully charged is around 14.2 volts. So the trolling batteries were still fully charged.
If you connect a charger to a fully charged battery it will still try to charge it from 12.8 up to 14.2 and then maintain around 13.6 depending on the charger and settings.
Your indication of how long it takes to get it back to full charge is a better guide based on past experience.
As batteries get older they lose capacity. If capacity is lower it takes less charge to fill them up so the length of time to charge gets shorter. Spending a long time suggests batteries in good condition.

thank you, i'm starting to think your right, it's not as bad as i think. The fact that the cranking battery was made in 2015 and has some lower volts than the trolling motor batteries has me thinking of changing it out, that's pretty cheap "insurance" for the most important battery on the boat.

[ifishinxs]

Ann-Marie is correct!
I have the 330MK charger. I unplug mine once the charger goes green on all three batteries. Then I plug back in the night before I fish to top off the batteries. lead Acid batteries over time will slowly degrade. 4 to 5 years of service is doing very well. I fish once or twice a week year round so my batteries get a lot of cycling. I just changed all three of my batteries to AGM. I’m hoping for 5 to 7 yrs.