Charging Trolling motor battery from the Outboard

Sorry if this question has already been asked, I did some searching and couldn’t find anything.

I have a 16 foot lund with a 60 HP Merc. There’s a battery in the back that I use for starting, running lights, depth finder, etc. The alternator in the outboard does a fine job of keeping that battery topped off. In the bow I have a 27 series deep cycle that runs the trolling motor. No connection between the two batteries right now. Here’s the deal: I spend a week on vacation somewhere and after a couple of days I’ve run that trolling motor battery down. I’m not too excited about the prospect of pulling it out of the boat and lugging it up to the cabin so I can put it on the charger. The dock is too far away for an extension cord.

Is there any good way to use the alternator in the outboard to charge BOTH batteries?

I did some Internet searching and found somethng called a “Battery Combiner” but it’s hard to tell if I was reading sales hype or if these things really work. Anybody doing anything like this, or is there a better way to handle the situation?

Many thanks

Rootski

Rootster,

I had looked into these chargers a couple years ago. Everyone I spoke with said that the big motor doesn’t run enough to charge the trolling batteries…as it’s used to (normally) get the boat to the fishing area…then the trolling motor is used.

I don’t have any personal experiance with these…just that this made sense to me. Extension cords are farily cheap??

I also was thinking about doing the same thing.

I know of one company that offers what you want. Stay-in-Charnge
I have heard many different opinions about them.
I do know that most smaller outboards like ours, 50 horse, have small output alternators, 10-15 amps. I was told by, Pro Rigger, Jim Wentworth that he could make it work but it would take forever to charge the trolling batteries.

Ron

Thanks for the input guys. My gut feeling is that I’d have to run the big motor for a long time to get any significant amount of charge into the trolling motor battery, but you never know. The resort we’re gong to has a dock for every cabin so theoretically I could run an extension cord but it would be well over 100 feet long. Maybe the best idea is to pull the boat out and park it next to the cabin when the battery gets low.

In the future I’m going to buy smaller batteries, physically smaller and lighter. And get two of them and a “two wheeler” cart. Then I can have one charged up and ready to swap, the two-wheeler so I don’t have to carry it the whole way, and a 24 series would be a lot easier to horse in and out of the boat.

Thanks again!

Rootski

100ft is not too long a run for a good extension cord and a charger. Your not drawing any huge amp load. Just saw FF or Menards had one on sale. 12ga wire too.

I saved this link a long time ago, maybe this will help you.. Click this

I lived in an apartment for a while that didn’t have electricity in the garage, and the 2 wheel dolly is the only way to go. I attached a plastic battery box to it and rolled it back and forth for charging. But in this case, I think I’d go with the long extension cord.
my $.02