Dead boat batteries?

KsRancher

WKR
Joined
Jun 6, 2018
Messages
542
Can't figure out my issues. Need some help. Bought a boat this spring. Bought a new 24v trolling motor and 2 new 12v batteries. I have them wired in series. The boat had a new looking 12v charger with 2 wire banks on it. The place I bought the batteries told me wire them in series for 24v, but hook the 12v charger leads up just like I would if the batteries were separate.


I used to boat for a month in the spring and worked great. Life got in the way so the boat set in the shed for a little over 4 months without being touched. Drug it out and batteries are DEAD. As in ZERO reading on the voltmeter. Currently have them separated and charging using the 2 bank charger. They were so dead that I had to hook them up to my truck and get a little juice to them before the charger would begin to charge them.

Wondering where the juice went with only the trolling motor and charger hooked up. Bad charger maybe? Any thoughts? Thanks.
 

RMac5

Lil-Rokslider
Joined
Feb 13, 2019
Messages
101
Location
Amarillo/Salado, Texas
My battery guy tells me to always disconnect the negative on everything that might sit for any length of time. He said everything has some sort of drain, disconnecting the negative stops all of that.
 

49ereric

WKR
Joined
Jun 21, 2022
Messages
834
Battery tender 👍
My previous wood truck had a dead short so lived with disconnecting the battery. 🤷‍♂️
 
Joined
Sep 24, 2019
Messages
923
Get a battery disconnect for the ground. Also, when charging in series, connect positive of one battery and negative of other. Your guy told you wrong.
 

Marbles

WKR
Classified Approved
Joined
May 16, 2020
Messages
3,686
Location
AK
Install a battery disconnect. Most everything has some level of parasitic draw. A battery tender would also work, but a disconnect will protect your charge when not at home as well.

Blue Sea makes quality marine electrical components.
 
OP
KsRancher

KsRancher

WKR
Joined
Jun 6, 2018
Messages
542
Here is how I have it hooked up
 

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Binz17

Lil-Rokslider
Joined
Feb 21, 2021
Messages
133
Install a perko switch to cut off. I do it even on my newer boat, seems like there is always something that has a short in a boat and slowly drains the batteries.
 

Jeffro

FNG
Joined
Oct 17, 2019
Messages
38
Location
Coeur d 'Alene, ID
The charger as you have it drawn is a single bank charger with 2 batteries hooked up. A true 2 bank battery charger will have 2 separate pairs of output wires coming out of it. 1 pair for each battery. If you want to charge them as 2 separate batteries, they need to be completely isolated from each other. Your picture has them tied together at the charger.
 
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KsRancher

KsRancher

WKR
Joined
Jun 6, 2018
Messages
542
The charger as you have it drawn is a single bank charger with 2 batteries hooked up. A true 2 bank battery charger will have 2 separate pairs of output wires coming out of it. 1 pair for each battery. If you want to charge them as 2 separate batteries, they need to be completely isolated from each other. Your picture has them tied together at the charger
Yep. My drawing is not exactly right. It has two different sets of wires coming out of the charger to charge separately. Its a 2 bank charger
 
Last edited:
Joined
Jul 23, 2021
Messages
457
Did you have them charging while it was parked in the shed?

I was roasting batteries for several years but I would always charge them to full and only plug it in when needed. The past 3-4 years I have my boat plugged in any time it isn’t in the water and my battery problem went away.
 
Joined
Aug 10, 2019
Messages
2,487
Location
Lowcountry, SC
Did you have them charging while it was parked in the shed?

I was roasting batteries for several years but I would always charge them to full and only plug it in when needed. The past 3-4 years I have my boat plugged in any time it isn’t in the water and my battery problem went away.

Trickle charge works. Disconnect switch also works.
 
Joined
Jul 23, 2021
Messages
457
Trickle charge works. Disconnect switch also works.
Yeah mine has a disconnect that kills power to everything besides my power poles which are on my cranking battery so I’m not sure what the problem was all I know is it is fixed by leaving them plugged in.
 
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