Dual Battery setup

[ChilliSpoons]

I have a 16’ Lowe aluminum boat that use in the lakes and rivers. It came with a two battery setup, one 14 years old and the other 9. I’ve set the boat up with a couple of two belt Scotty electrics which suit my needs perfectly.

On my last outing I had issues retrieving my downriggers which after a load test from CT turned out to be a bad house battery. The older of the two batteries was my starter battery which tested out good. I’ve since purchased two new batteries from Costco which will be installed this weekend as well as a new circuit breaker which show quite a bit of corrosion.

So my boat doesn’t have any kind of isolator switch that I can easily find in the battery compartment. And the batteries aren’t wired in parallel. Could there be an isolator wired further away from the batteries or is there something that I’m missing or not understanding?

 

[ship happens]

ACR add a battery kit

 

[ChilliSpoons]

I get that being the upgrade I’ll eventually go with but I’m trying to wrap my head around how it’s currently wired. The electric trolling motor and downriggers run off of the dead cycle battery. What separates the two batteries?

 

[ship happens]

Do you have a battery switch?

 

[ChilliSpoons]

Do you have a battery switch?

No battery switch. The starter battery is wired directly from the 75hp Merc and the house battery seems to run forward to the console. Somewhere there must be something that isolates the starter battery from the house, I just haven’t found it yet. I just assumed that it should be right close to the batteries. There is a 20 amp circuit breaker off of the positive side of the starter battery but I’m assuming that that’s just protecting the starter battery.

 

[ship happens]

Sounds like you need to add a switch and an ACR. Ontop of a reconfiguration.

 

[ChilliSpoons]

Sounds like you need to add a switch and an ACR. Ontop of a reconfiguration.

Most likely a winter project.

 

[ship happens]

Most likely a winter project.

Probly a half or a days work. Not too bad

 

[ChilliSpoons]

Yup, just mo money. Not a ton but still gotta pace myself lol

 

[Newf]

I get that being the upgrade I’ll eventually go with but I’m trying to wrap my head around how it’s currently wired. The electric trolling motor and downriggers run off of the dead cycle battery. What separates the two batteries?

Don’t fully understand your question but a battery combiner allows two batteries to be charged from a single charging source. From what I read online most small boats would be set up this way. The start battery would charge to a certain voltage, say 12.8 volts and then it would switch and charge the house battery. Sorry if this is irrelevant to your question.

 

[ChilliSpoons]

That is exactly how I understand it as well. I just can’t find any kind of an isolator anywhere and was wondering if there was another way that it could be set up that I’m unaware of. I’ll need to start removing some panels to investigate further.

 

[zurk]

boats usually dont have isolated battery banks unless you deliberately design them to have isolated banks and then its $$$ to isolate them.
mine are running isolated banks. but i paid a ton to have them isolated. you need isolated battery chargers, no common negative ground, isolated engine battery, isolated DC to DC converters, isolated MPPT controllers etc etc. unless its mission critical (cross an ocean and potentially die scenario) its not usually worth it.

 

[Saxe Point]

If you’re going to be using an electric trolling motor, then obviously you’ll need 2 batteries. But if not, and you’re just going to have downriggers, chart plotter, fish finder and VHF radio, you might want to consider the simplicity, along with weight and cost savings, of going with a single battery. I have, and it has worked out perfectly.

 

[ChilliSpoons]

If you’re going to be using an electric trolling motor, then obviously you’ll need 2 batteries. But if not, and you’re just going to have downriggers, chart plotter, fish finder and VHF radio, you might want to consider the simplicity, along with weight and cost savings, of going with a single battery. I have, and it has worked out perfectly.

I run a bow mounted trolling motor as well. I’d love to shed the weight and go with one battery but I like the idea of a dedicated house battery. I see some affordable kits that have a Split Charge Relay, I’m curious if it would suit my needs???

 

[Max123]

If you’re going to be using an electric trolling motor, then obviously you’ll need 2 batteries. But if not, and you’re just going to have downriggers, chart plotter, fish finder and VHF radio, you might want to consider the simplicity, along with weight and cost savings, of going with a single battery. I have, and it has worked out perfectly.

Totally agree. I went from a dual battery setup to a single high output AGM battery. I carry a NOCO jumper kit as my backup.

The NOCO is great. We were up in the Okanagan with the family for a weekend using the ski boat - battery wouldn't hold a charge and couldn't get a new one that day. Grabbed the jump kit out of my truck and used it for a full day of starting/stopping on that big 350 V8 with zero issues, and it was still at 75% capacity when we finished (maybe 10 starts).

 

[ship happens]

I'd be real careful running any modern outboard with a low battery condition or the wrong type. Good way to damage ECUs and rectifier/regulators

 

[ChilliSpoons]

I do have a jump starter onboard to be used in emergency situations.

 

[Max123]

I'd be real careful running any modern outboard with a low battery condition or the wrong type. Good way to damage ECUs and rectifier/regulators

Good to know - in this case it was an older Mastercraft with electronics limited to an ancient throttle body EFI - but my etec may be more sensitive.

If you have to jump a modern engine due to draining down the battery (say from a day on the water, not a stone dead battery that won't hold charge) - any recommendations on how to proceed to minimize the chance for damage?

 

[kingblazer84]

alot of modern electronic stuff is super sensative to voltage differences and drop outs etc.. like @ship happens said we see a ton of problems in the automotive repair world.

 

[ship happens]

Etecs are the most sensitive. It's because they have a 50 amp charging circuit along with a second and third set of stator coils that run the engine. That also produce high amperage. However on startup the engine draws directly from the battery to drive the injection, starter, ignition and basically everything that runs through that rectifier to create the 55volts the engine needs to run all the devices. Once started the engine creates its own power and switches back. This is call the SAC circuit and its part of the rectifier chip. Which is split into multiple zones.

All other injected 4 stroke engines need battery power to run. These ECUs do not want deep cycle batteries or low battery conditions. It will damage electronic equipment. Same with cars as stated above