One battery bank not charging

RMC3

Member
Joined
Jul 15, 2025
Messages
6
Reaction score
1
Points
3
Age
71
Model
Freedom 307
I have a 2018 Freedom 307. One of the battery banks appears not to be charging. The other is fully charging. What should I do? Any advice greatly appreciated.
 
Chris, thanks for responding. There are 4 batteries. I’m not sure what is linked to which bank or how to tell.
 
Ok, then your battery setup is different than mine.
You need to find out how your batteries are connected as this info is needed to pinpoint the problem.
My guess would be
Stbd engine -> stbd side engine battery (the one on stabd side)
House -> two betteries connected with a link cable between the +12V posts (the two ones in the middle)
port engine -> port engine battery (the one port side)
There is probably a ACR/VCR relay what connect engine batteries with the house batteries (and this may malfunction)

Can you take a photo of the whole battery compartment and of your battery switch box/panel?

Check also your GW user manual, there is a chapter how to use the battery switches and make sure you follow the directions in the manual.

Chris
 
Not charging? When? With engines running? On board charger? Battery switch position? Typical OEM setup is starboard engine alternator connects to starboard battery switch which is house circuit and port engine connects to the port switch. Test voltage at the battery with switches in various positions, should be 13-14 VDC. Of course is you are referring to an on board AC powered charger, battery switches are not in the loop and don't matter. Your on board charger should have indicator lights. Don't confuse banks with switches. Each switch decides which bank powers a circuit or receives power from a charging source. If it wasn't modified from OEM standard, Starboard switch always receives charge from Starboard engine alternator and port switch always receives charge from the port engine. Each switch therefore charges the selected (#1 or #2) bank from the respective hardwired engine alternator.
 
How old are the batteries? May be time to replace. What group/sizes are they. 4 batteries - look to see which ones are in parallel.

Battery charger cables may have inline fuses at the battery. My ProMariner does. If this is blown you won't charge.

Get your voltmeter out. Batteries off charger should be 12.8 volts. Charger on 13.1 volts.
 
Check the fuse between battery charger and the battery
 
You have two choices. Either go to the dealer and let them sort it out, or start learning about your boat. A harsh truth, but a novel could be written from what is left out of your original post.


Get the manual for your boat and find the DC diagram pages. If you don't have one, download from the Grady White site. Start comparing it to what you see in the battery compartment. It may or may not align, depending on what previous owners and dealers did.

Make a diagram that shows all the connections between batteries and the additional wires. Figure out where they go.

Determine if you have a shore charger or not. If you do, find the manual. Look at the lights displayed on the unit, and compare to the manual.

There are a couple of great books about DC wiring for boats, one is something like the Boat Owners DC wiring bible.

Buy and learn how to use a multi-meter. Start at the batteries. f batteries are good, work downstream from there. Go to an accessory which is not working and check the power at that switch and so on.
 
How old are the batteries? May be time to replace. What group/sizes are they. 4 batteries - look to see which ones are in parallel.

Battery charger cables may have inline fuses at the battery. My ProMariner does. If this is blown you won't charge.

Get your voltmeter out. Batteries off charger should be 12.8 volts. Charger on 13.1 volts.
Often the in-line fuse isn't blown but the fuse holder has failed. That was common with certain models but I can't remember which ones. I had a Guest 2 bank 20A charger in one of my previous boats and the fuse holders in that one did go bad, fuses looked fine.
 
Often the in-line fuse isn't blown but the fuse holder has failed. That was common with certain models but I can't remember which ones. I had a Guest 2 bank 20A charger in one of my previous boats and the fuse holders in that one did go bad, fuses looked fine.
ProMariner was terrible before. Glass fuses. Back on charger after a days fishing you grab fuse holder and they were uncomfortably hot. When cold they weren't working. Fuse came out in pieces. Chop it off and switch to blade type.

The new ProMatiner which I have is great. I still recommend ProSport 20HD.
 
Last edited:
Thanks for the helpful advice. Turns out there is a box under the starboard gunwale that has a fuse reset for the charger. Turning it off and resetting it got the other bank charging again.
 
Are you saying that only one battery is wired to the charger? I would think that if there is a breaker reset for the charger, both batteries would not be charged.

Perhaps your house bank was not charging during normal running, not shore power maintenance charging. In that case I would suspect that ther is a charging relay (ACR) that is not working.

I am gld you got the battery charging. I just don't understand exactly is configured and what function the charger has for the other battery (or batteries)
 
Hoping this helps. I can't explain it, but as soon as I reset the shore power breaker, the lower lights on the charger, which had not been illuminated when I discovered the issue, came back on indicating charging had resumed. The indicators showed two bars less than the ones for the upper bank, but by this morning, both were equal as shown in the picture. Thanks for responding. You all got me to keep looking.
 

Attachments

  • Shore Power Breaker.jpeg
    Shore Power Breaker.jpeg
    1.5 MB · Views: 6
  • Battery Banks.jpeg
    Battery Banks.jpeg
    19 KB · Views: 6
  • Battery Charger.jpeg
    Battery Charger.jpeg
    21.8 KB · Views: 6
  • Like
Reactions: Sardinia306Canyon
In your photo you show a green wire connected to one of the negative battery terminals. Where does that wire go? I ask because typically green wires are earth grounds and i don't think that earth ground should be connected to your batteries

That ECLI breaker is both ground fault protection and over current protection and the fact that it triggered can mean that you have an electrical issue with the boat or perhaps a problem with the shore power itself. You need to keep an eye on it to see if it trips. Since you weren't aware that it had tripped, I will assume that the only service on shore power is you battery charger.
 
Last edited: