Floating Ground?

[capndan]

I'm a newbie, just trying to learn a few things. I was studying the wiring schematic and saw the note that said "Notice wire connecting the 24vNeg to the 12vNeg. this keeps grounds from floating."

What does that mean?

I'm specifically asking because I plan on installing a 2 battery (24v) trolling motor, and likely, a 2 bank charger.

Thanks,
dan l

 

[bruceb58]

Re: Floating Ground?

If you don't reference the grounds together, it is possible to get a very large voltage delta between +12V and +24V banks depending on what is charging the two banks.

 

[Silvertip]

Re: Floating Ground?

That shouldn't be an issue since all of the grounds on a smart charger are isolated. The trolling motor system and engine system can remain totally isolated with no issues. Where issues may arise if it is decided to power some accessories from one of the troller batteries and others from the starting battery.

 

[capndan]

Re: Floating Ground?

Ok, thanks. If I'm reading that diagram correctly, it looks like we have only the trolling motor on the 24v, and everything else on the starting battery. Is that typical of what you recommend?

It seems to me nothing on the starting battery would draw much (lights, fishfinder) except maybe the livewell? If you leave the livewell on the starting battery, would you recommend a certain type of battery there?

I think I'm a bit confused about these batteries. I knew about "deep cycle" and "starters", and what their intended uses are, but I've picked up the occasional mention of a battery that is both a starter and a deep cycle battery.

Is that typically what one should use, and what comes with a new boat?

 

[Silvertip]

Re: Floating Ground?

Batteries are "buckets of electricity" so obviously a bigger bucket (larger capacity battery) is never a bad decision. A battery with too little capacity is a bad decision. Battery type is important. Marine Starting or dual purpose Starting/Deep Cycle for the engine. Large deep cycles for the troller. AGM and other hi-tech batteries are ok but are expensive and in my view provide no advantage other than emptying your wallet. Leave the 24 volt system totally isolated and dedicated to the troller. Keep the batteries topped off with a dual bank charger. A three bank can be used with the third output dedicated to the starting battery. Unless you add a killer stereo or some other very high current draw items, the configuration I just described is fine.

 

[capndan]

Re: Floating Ground?

That's awesome, thanks!