Dual battery setup check

[PDubs]

We've been having battery issues with our boat recently, and it's possibly due to bad batteries following the unwinterizing process. Boat was unwinterized, transported down, and we have had issues ever since. Before it left origin, it was confirmed the boat was running (this was a family deal, no smoke and mirrors). So far,we replaced the main battery everything connects to with a brand new one, and it was working fine for a few days. I then connected the secondary battery to it and came back today (about four days later) and had to use a battery charger.

I disconnected the older (secondary) battery and connected a heavy duty charger against the main one. Eventually got it started and ran the boat on a single battery for about an hour, hopefully enough to recharge the main battery. I plan on getting a new secondary battery (deep cycle?) but want to verify the wiring. Some notes regarding the setup:

- Stereo requires a second battery and is already setup on a factory ACC switch
- Stereo only comes on when above switch is activated
- Diagram below does not indicate in-line fuse on positive lead to the stereo equipment
- I do not intend to have the secondary battery setup on a switch

I can't imagine it being that difficult to connect a secondary battery, but a little verification/suggestion wouldn't hurt.

 

[Bucks45]

Re: Dual battery setup check

A couple of good examples here.


http://forums.iboats.com/showthread.php?t=249593&highlight=dual+battery+wiring+diagram

 

[RickJ6956]

Re: Dual battery setup check

I do not intend to have the secondary battery setup on a switch

Then you don't have "Main" and "Secondary" ... You have a single bank of batteries in parallel. Because there is nothing to separate the two batts, both will charge and discharge together.

A battery isolator will prevent this from happening, or you can save some cash and install a switch.

 

[Silvertip]

Re: Dual battery setup check

The way you have the batteries wired (in parallel) as pointed out the two batteries merely act as one great big battery. The down side to this is that in a short time on non-use, the weaker of the two batteries will suck the life out of the stronger of the two until both batteries equalize. So you need to do one of several things: 1) add a dual battery switch, 2) add an ACR or VSR (same function different terminology) or 3) add an isolator. Any of these will provide the battery isolation you need to protect the starting battery so you can operate the other loads off the secondary battery. A dual battery switch also allows operating the starter from either or both batteries so they are more versatile in that regard. Some ACR/VSR's have a combine feature that connects both batteries to perform a "jump start" capability. Anyway, what you have will continue to plague you especially if the boat is not used on almost a daily basis. And by the way, you cannot fully charge a deeply discharged battery in an hour. Even an I/O with a 60 amp alternator will take longer than that. Most outboards have far less output than that - except for the very newest models.

 

[PDubs]

Re: Dual battery setup check

Thanks for the responses guys, I obviously have much to learn.

Silvertip - Thanks for the added note of discharge refresh time. I have a 99, but maybe that's not recent enough. How long should I have run it in order to fully recharge the battery?

 

[PDubs]

Re: Dual battery setup check

Let me ask another stupid question.

I saw the diagram on how to wire the battery switch up; fairly simple. However, where do you mount the actual switch unit? I ask this because I would rather put it in the engine bay (or whatever the boating term is) but then I wouldn't be able to raise/lower the hatch when switch is in "OFF" position. Is there a prescribed location for this piece? It's starting to sound like I may have to drill through the fiberglass between the engine area and seating/storage.

 

[Silvertip]

Re: Dual battery setup check

Most people get way to concerned about having to constantly fuss with the switch but that's because they don't understand how it works and why they should or should not change settings. 1) mount the switch where it is easily accessed -- but as close to the batteries as possible. Why?? Because all of the cables coming fromt the batteries to the switch, and from the the COM terminal to the engine are battery cable size cables. The longer they are the more expensive the install becomes. 2) For a days boating you can set the switch from OFF to BOTH and run just like you have been when the batteries were permenantly connected. BOTH means just that -- both batteries are being charged and both operate all accessories. Unless you beach or dock the boat for long periods of time with accessories running, there is no need to switch to BAT 2 (if that is the house battery). You can also run all day on BAT 1 or BAT 2. The engine and accessories don't care where the juice comes from and the engine will direct it's alternator output wherever it is told to go as directed by the switch. The switch is a versatile tool. Learn to use it to your advantage. You don't need to constantly fool with it. Just don't turn it OFF with the engine running.

All we know is you have a 99 engine. We have no idea what make or HP or whether it is an I/O or an outboard so we have no idea how long you need to run to charge the battery. With a typical 75 HP outboard of that vintage the alternator output for example would be in the 16 - 20 amp range at wide open throttle. You would need to run wide open for several hours to fully charge a deeply discharged house battery. Since you have two batteries, double that time if both are deeply discharged.