I have a 36 v trolling motor and don't want to have 3 12 volt batteries to use it. I am not needing long run times so the loss of amp hours isn't a concern.

Does a single unit that provides 36vdc exist? keeping up with a bank of batteries isn't working for me but I might can handle a single.

Not in a lead acid battery. It would too heavy to lift without equipment. You can get a lithium iron phosphate (lifepo4) in 36v, but they are expensive plus need a special charger. Like over $1,000.

I'd get a three bank charger for the batteries you have.

I have the charger. All three batteries are dead plus it is an extreme pain to get on my knees and move them around inside the center console.

Not that I know of. You want 3 AGM 12 volt batteries.

Ok How about three lead batteries but smaller than the group 24? Is that an option?

You can make 36v as small as you want. Just pick any three 12v batters and have at it. You lose amps in proportion so find the balance you want.

How about 35 amp hour wheelchair batteries? They weigh about 24 pounds each and are under $100 each.

Out of curiosity, why do you have to move them around?

12v batteries come in every imaginable size. Figure out how many amps you need and adjust accordingly. Problem will be that deep cycle batteries are not likely to be in the very small sizes but again if you know your load you can plan around that. You can also get li batteries in 12v (I use them on racing motorcycles) but I have no idea their character in this kind of application. If I get a chance I’ll look. But in general they scare the pants off me as I have seen too many on fire.

Once installed they are fine. This is a very tight fit and access is very hard. Imagine trying to lift a full battery into a tiny hole while on your 66 year old hands and knees. Now do this with not one but three big old batteries. Oh, and the leaning post is right in the way.

Houdini I ain't.

This is a boat I hope to sell one day and would like to get the trolling motor back in service. I don't use it like I once did. A great craft but I'm getting too long in the tooth to really enjoy it. The last two years I've just left it at home on my trip to the shore.

What group size are the current batteries?

quote:

Originally posted by 9x18:
Once installed they are fine. This is a very tight fit and access is very hard. Imagine trying to lift a full battery into a tiny hole while on your 66 year old hands and knees. Now do this with not one but three big old batteries. Oh, and the leaning post is right in the way.

Houdini I ain't.

This is a boat I hope to sell one day and would like to get the trolling motor back in service. I don't use it like I once did. A great craft but I'm getting too long in the tooth to really enjoy it. The last two years I've just left it at home on my trip to the shore.

I just did it today in a 27' whaler. Hire someone to change them or come up with a system to slide them in, such as a board or something. I'd keep them the same size. Will your battery trays/boxes hold smaller or different ones securely? Do you really want to mess with changing up a bunch of cables to match smaller batteries?

If you are looking to sell it, Jimmy is right. Just pay someone to do it. No potential buyer is going to want a jury rigged smaller battery set up.

Install a water resistant boat 3 bank battery charger on the boat and then just plug it in and forget about it.

Waterproof 3 bank charger

not sure what you think the charger has to do with the problem?

Yes, I have the three bank charger and it is fine. I have three trays that will hold group 24 (smaller) or 27 (larger) batteries securely. I have the cables and connectors ready to go.

What I don't have is three good batteries or the strength to deal with them. The opening is about 2' wide by about 12 inches high . 2 small hatches .
A sitting post is permanently mounted directly in front of the opening severely limiting access.

I was thinking of a simple single source of power more of a demonstration/light use rather than a full time fix. I was trying to avoid the hard work of a proper fix.

The boat (a Seapro 180CC) is at least out of the garage and in the water. The Merc 125 is running like a champ and is a beast compared to my pontoon and it's 75. Loud though.

Thanks to everyone for the replies and suggestions. They are greatly appreciated.

A 17 pound 50 amp hour lifepo4 battery discharged to 20% will give you the same amount of juice as 80 amp hour group 24 lead acid battery discharged to 50%. Even with an 80% Depth of Discharge (DOD) before charging, the lifepo4 battery will last 4 times longer than a lead acid battery at 50% DOD before charging. The downsides are the lifepo4 battery runs $400-$500 and requires a special charger.

I had to change the batteries on my boat. Even with lifting the engine hatch and what looks like tons of room around the 8.1L Mercruiser, it was still a pain in the ass. It's not like it's straight dead lift getting the batteries out and in the trays. Getting the cables out of the way while getting the batteries positioned and then reconnecting the cables. Ya, I'm glad it's not something I do on a regular basis.

I'm only 52, but I've adopted the attitude that there's no shame in paying someone else to do something. Running wires in my attic for example. Roof has a 4-12 pitch, there's maybe 44" inches inside at the peak. About 15 years ago, I took out all the fiberglass insulation and had spray foam insulation done. I then ran some new circuits for lights and such. Last year, I paid someone to run Ethernet for 8 security cameras, 2 WAPs, and speaker wires. The thanked me for having left all the boards up there I had used to get around. It was money well spent.

quote:

Originally posted by 9x18:
Yes, I have the three bank charger and it is fine. I have three trays that will hold group 24 (smaller) or 27 (larger) batteries securely. I have the cables and connectors ready to go.

What I don't have is three good batteries or the strength to deal with them. The opening is about 2' wide by about 12 inches high . 2 small hatches .
A sitting post is permanently mounted directly in front of the opening severely limiting access.

I was thinking of a simple single source of power more of a demonstration/light use rather than a full time fix. I was trying to avoid the hard work of a proper fix.

The boat (a Seapro 180CC) is at least out of the garage and in the water. The Merc 125 is running like a champ and is a beast compared to my pontoon and it's 75. Loud though.

Thanks to everyone for the replies and suggestions. They are greatly appreciated.

What brand of battery trays do you have? If they're gil, you can twist and remove the upright bolts that the top hold down goes over and bolts to. Then remove the cables, zip tie them and know where they go, then pull the closest battery, and then slide the next over to closest, then the next...(if it's set up that way)...then reverse order......Keep note what orientation the batteries are (if positives are towards the bow etc., probably 2 have the positives facing forward and 1 aft, or vice versa). I'd go with AGM deep cycle. The way I see it, you have 2 choices......pay some strong helper to do the heavy lifting, or a battery place that does installations or a marine place.
The other option, since you probably have a small center console, is just unscrew the center console from the floor and tip it up enough to change the batteries (without having to unhook electrical) and screw it back down (don't forget to 5200 all of the screws.)

As far as I know. LIFOPO batteries are not USCG certified in a gas boat, and I wouldn't take a chance on them being mounted inside of a small center console right in front of the gas tank.

Changing batteries sucks on boats/yachts. I used to do 8D's at almost 200 lbs each, that really sucked.......now I don't do anything more than a group 31, otherwise I have someone else do it.

If you're going to sell the boat don't worry about installing the batteries . Buy 3 new batteries and hook up a temporary cable to demonstrate that the trolling motor works .

Have you thought about just picking up something like say a 2 1/2 or 4 HP gas Yamaha outboard?