Battery drain/charging…?


New Member
Reaction score
Hello, first post here…..

I bought a new SX23 Premium in 2020 and it has two batteries plus an onboard charging system. The first summer I didn’t charge the batteries at all and they were on “ALL” switch (which means both batteries). It worked fine until the end of summer when the whole boat went down. I went out and bought two brand new batteries at the end of the summer 2020. This summer I started charging the new batteries all night before taking it out. Since this is at our vacation condo, we usually just ride on weekends. And, after studying on it I now use “1” mostly and “2” as a backup.

This summer my alarm is going off again indicating that batteries are low. A couple of friends with Bennington’s never charge their batteries, have just one, etc. and it doesn’t seem to be a problem like with mine. My question is something wrong with my auto charging system?

Again, I’ll plug in my onboard charger all night before and still only get 6-7 hours out of each battery. I do run the bluetooth sound all the time and the depth finder half the time. Thanks in advance.
Last edited:


Well-Known Member
Reaction score
The common wisdom is to run on 1+2, and float/relax on 1 or 2 so you have a spare battery if one goes dead. If you only stay on battery 1 or 2, only that battery gets charged when running.

Personally, I always run 1+2, and I've just never bothered switching to 1 or 2 when stationary.

Do you turn the switch completely off when unattended? How about the master switch at the helm?


Well-Known Member
Reaction score
Sanibel FL
You really should only leave it on 1+2 when charging either from shore power or when the alternator is running and charging while underway. When not being charged, the 2 combined batteries (1+2) will always try to "equalize" their voltage. So, if one is stronger than the other, the weaker battery will draw from the stronger one until they equalize. If the weaker battery is really run down flat, it may completely drain the good battery trying to do so or it can't do it at all and both go dead.


Well-Known Member
Reaction score
I have a 2020 and had similar issues; What I had found out was that my boat was wired incorrectly. With a dual battery set up you should have a distribution panel. If that is correct, you should also have a battery isolator and a switch that only has the option for "on" "off" and "combine batteries". From what was told to me by the marine that fixed this issue was the dealer I purchased it from wired it according to a schematic that is from 2013. There is an updated schematic, 2017, which shows proper wiring which I have attached.

I am not saying this is your issue, but sharing my experience. Fortunately, I know enough about electrical wring that I was able to diagnose the issue myself as the dealer I bought it from kept telling me it was fine. After some digging and confirmation from Bennington, I took my boat to another dealer which more or less said, they were not surprised I was getting the run around (I guess not all dealers are equal in their experience)

Below are also images of how it was wired and after it was fixed to help visualize the schematic. The small leads on the battery are my on board battery charging system (after market) so you will not see that in the schematic.

Wired Correctly.jpg


  • Dual Battery Wiring.GIF
    Dual Battery Wiring.GIF
    47.4 KB · Views: 29
  • Battery Compartment.GIF
    Battery Compartment.GIF
    297.9 KB · Views: 26