Battery upgrade project

[sailinggreg]

Hi Tom,

Thanks for your simple and clear reply. This certainly seems to be my set up. You can see the smaller wires in the picture. I remember when I had an electrician on the boat he added a fuse on each wire just as you mentioned. Those small wires are even labeled so I will double check when I'm on the boat but I remember they go to the charger.

So I guess the boat yard did in fact move the red cable from the positive terminal of one battery to the other. I guess either since the battery was smoking they didn't want to leave anything connected to it, didn't want to leave the red cable just dangling, or maybe since they didn't know which one was battery 1 and battery 2 they connected both the red cables to the one battery to try and charge it and start the boat. Any thoughts on that?

Thanks,

Greg

Thanks Tom, Loren and everyone for the good discussion and info regarding batteries.

I installed my new batteries but still have a couple questions.

There is only one small wire going from my charger to the positive terminal on only one of the batteries. I even traced it back to the charger to make sure another wasn't laying loose someplace, but on my boat there only appears to be the one small wire from the charger to the positive terminal of one battery. (The two other small wires I recalled (and in the previous pic) go to the auto-helm and a USB power supply in the cockpit).

So, I went ahead and installed my batteries as described by Tom but with just the one small wire from the charger to the positive terminal of one battery. Engine started right up. To test, I drained the batteries one at a time (left a couple cabin lights on overnight), but one battery would only recharge to about 10 volts.

A boat buddy thinks that there should only be one small wire from the charger and looked in Calder's "Boatowner’s Mechanical and Electrical Manual (the bible? ), which said if one battery doesn't charge completely you should put the battery selector knob to BOTH. I did this and both batteries fully recharged.

Does this make sense to you experts?

I'd really appreciate further thoughts.

Thanks,

Greg

 

[Kevin A Wright]

Loren,

As usual when I have a boat project I check in here first for advice. Took the grandkids down to the boat for an overnight at the dock and house battery wouldn't hold a charge above 8v. So time to replace. Had a big 4D in there before but frankly the effort of moving that thing in and out of the cabin and onto the dock was something I didn't enjoy. So decided to go with your 2 6v plan.

Wasn't able to find any Trojans available in the local Port Townsend area (no surprise there) but did get 2 6v 220AH flooded Golf Cart batteries at the local Les Schwab. They stock lots of them for RV's. Total cost (including WA sales tax) was $299. They had AGM's available for twice that price but since I've got an ancient dumb charger didn't want to go that route since I've heard they are prone to damage from overcharging. Keep thinking I should switch out the charger for a smart one some day, but it is buried behind the Espar heater and the pressurized water pump so I usually find other projects that have more priority.

Also found a low profile battery tray with straps on Amazon for $20 that should hold these in place perfectly once I screw it down.

One question, what gauge jumper should I use to connect these batteries in series? I've got a 4ga one but the ones in your picture look a lot beefier than that.

Kevin Wright
E35 Hydro Therapy

 

[Tom Metzger]

One question, what gauge jumper should I use to connect these batteries in series? I've got a 4ga one but the ones in your picture look a lot beefier than that.

The easy answer is the same size wire as the main battery leads to the battery switch. The jumper carries the same current.

 

[Kevin A Wright]

True. Although with the very short run compared to my main cables it can probably be a size smaller. Of course the difference between a 12" #2 and 12" #4 jumper is about $2. When in doubt, bigger is better.Kevin WrightE35 Hydro Therapy

 

[Tom Metzger]

True. Although with the very short run compared to my main cables it can probably be a size smaller. Of course the difference between a 12" #2 and 12" #4 jumper is about $2. When in doubt, bigger is better.Kevin WrightE35 Hydro Therapy

Your thinking is valid, but a surveyor might (unlikely) pick up on the jumper being too small for the fusing if there is any.

I'd ask around to see if anyone had an extra foot of the correct size. I might have a piece, but the shipping would cost more than the wire. Now if you want to drop in...

 

[Kevin A Wright]

I probably have a chunk somewhere myself, although the effort to search for it was weighed and found wanting. Clicking on Amazon only required me to lift a finger.... And I can trip over it tomorrow on my porch.

Kevin Wright
E35 Hydro Therapy