small/light starting battery options for engine/sonar/lights?

[Macintosh]

I'm looking at getting a new starting battery for a 25hp 1990's merc, which will also power a 9" sonar/gps, nav lights and a few very small LED interior lights. I have a giant of a commercial starting battery for this purpose in my bigger boat, but in order to maximise space and keep weight distributed where I want it, I'd like to go with as small a battery as I can realistically get away with and retain reliability. I do have a pull-start should this battery crap out, so it's not the end of the world, but I would like to be able to run sonar for at least 2-3 days without too much running to recharge the battery from the alternator, and if possible still be legal with nav lights, etc for a nighttime return. Anyone have experience with a similar rig that can offer experience or suggestions for some smaller batteries?

Note: Sadly, lithium is out of my price range and I'd like to keep using my current charger, which means I'm limited to regular wet-cell or AGM batteries. Mostly I'm wondering about size I can get away with based on others experience with smaller batteries. I see a standard group24 marine starting battery is about 45lb, that'll be my choice unless there is a good option well under that weight. Motor specification says to stay above 465MCA/350CCA.

 

[DaleH]

You probably won't like the weight, but I'd recommend a G4-sized 'dual purpose' battery that has CCAs to crank, but can draw down like a deep cycle. That's what I use on my 14' with similar devices and an 18hp OB engine.

Maybe there's a lighter one outh thar' somewhere, but I buy the batteries from Walmart as they are made by Johnson Controls (they also own Optima gel series batts) and have a 'born on' date on them. I routinely get 5+ years out of them, but replace them @ 5-years anyway (in the boats); keeping the old ones as backups to a sump pump at the house.

 

[Makaw]

Are you able to do any amp-hour estimates based on the draw ratings for your sonar and lights? My first thought would be to try and use the manufacturer data to make intelligent guesses on how much power you’ll need for 2-3 days of running that equipment. Then try and size for BOTH the CCA and amp-hour ratings of a specific battery. As DaleH suggested, a dual-purpose is a good choice.

I would venture a generic 24 would be perfectly sufficient, but you could probably step up to a 27 (6-10 pounds heavier) which might get you a nice amp-hour bump. I oversized my trolling motor batteries for that reason to group 31s. They run 60lbs each, but last FOREVER. A few pounds might be worth the added capacity. Pay attention to each specific battery though, even within a battery group size there will be weight and power output/reserve differences.

 

[Macintosh]

Thanks for the replies. I have a bigger-than group31 starting battery in my bigger fishing boat running the big engine plus multiple sonars, lights, etc, plus 2 group29 trolling motor batteries--all together I have more than 200lb of battery in that boat, so no argument in making sure i have enough power when I can get away with it. I'm also a fan of the everstart deep cycle batteries, as I've found them to be the most cost effective and pretty good quality. In this case, the entire point of this boat is to be as light and easy to drag around as possible--it will serve plenty of fishing duty, but I also will use it much of the time for camping and hunting, where I will need to drag it over beaver dams, up onto beaches, etc, so I am trying to minimize weight. When fishing I'll definitely have a BIG trolling motor battery, maybe even 2, but this particular battery I'm asking about is only for starting and accessories. I'm wondering if anyone has experience with any of the smaller tractor/ATV/RV type batteries, I've seen some that meet my on-paper requirements and weigh less than 20lb, so I'm wondering if anyone has used anything in this weight class for the purpose and can share their experience or knows of some good options like this with just a tad more reserve. If not, I'm quite certain the group 24 or 35 will be plenty for this application, I just suspect it's a bit overkill and weighs more than double this, so I'd just assume shed the weight and bulk if I can.

I see batteries in group-sizes h5, 51r, S46B24R, 96R, etc that meet the CCA requirement and are in the 18ish pound range, but I have no idea how to do the math to see how much reserve capacity I'd need, etc, so hoping someone else has gone down tis road and has some real-world experience they can share. Thanks in advance!

 

[gogittum]

Not sure about going 2 or 3 days without charging / running the engine....seems a little unrealistic to me. Surely you can plug in the charger at night ??

For mine, in the interest of light weight, I looked at my 60 hp Suzuki V-Strom 650 motorcycle which called for and had space for a 10 amp/hour battery. Surely that would work with my 25 hp Johnson outboard.....??

At first my cables were too long, even tho' a heavy gauge, so re-mounted the battery behind the rear seat and shortened the cables to 3 ft. Works like a charm.

I had some carburetion issues with the motor and that little battery started the motor at least 15 times in a row on a couple of different days.....and it really spun it. Not draggy, even a little bit. It also runs my chart plotter and 2 bilge pumps.

 

[Macintosh]

Thanks, that's exactly what I was looking for! Am I understanding correctly that you did have some issues using that setup with the full-length electrical cables on the engine? Can you tell me what battery that is so I can look at similar? You have used to start and power a sonar or gps for a full day though? Any issues other than the cable length? Have you had any opportunity to try it in colder weather?

Also re plugging in to charge--there's no electricity, when I say camping I mean backcountry/wilderness camping. Suppose I could get a solar panel, but it rains here a lot so not too crazy about relying on solar.

I did find some folks were using Odyssey pc950 or 925 on flats skiffs, which looks like a bigger battery than what you have.

 

[wmk0002]

I use a U1 size lawnmower battery on my Yamaha F25. It worked fine for a 30hp 2stroke as well. It powers my Helix 5 and a few other small things. Not sure what they weigh but I can grab it on the top with one hand and lift it easily. I think they are $25-30 at Walmart for an Everstart one. I also have one in my mower that is a 2015 model and still works fine and I never put mine on a trickle charger or anything over the winter.

 

[gogittum]

Thanks, that's exactly what I was looking for! Am I understanding correctly that you did have some issues using that setup with the full-length electrical cables on the engine? Can you tell me what battery that is so I can look at similar? You have used to start and power a sonar or gps for a full day though? Any issues other than the cable length? Have you had any opportunity to try it in colder weather?

Also re plugging in to charge--there's no electricity, when I say camping I mean backcountry/wilderness camping. Suppose I could get a solar panel, but it rains here a lot so not too crazy about relying on solar.

I did find some folks were using Odyssey pc950 or 925 on flats skiffs, which looks like a bigger battery than what you have.

Well, yah, but.... I don't fish all day without ever running the motor. Drift for a way, then power back, etc. Move to new area from time to time, so it does get some charging. When I bought the motor recently - it's a 1993 model 25 Johnson, it wasn't charging. Found that the coil under the flywheel was bad, so replaced it, which means it's getting full charging output when motor is running.

With no generator or other power source, a solar panel could at least help. I don't see any other options.....ummm....maybe one: Is it possible to jump from a car battery to charge the boat battery ?? I don't know if that's a good thing beyond getting something started, but it may be an option to check out.

When I got the motor, it had about 6 ft extensions on the power cables that were about 8 gauge and a sloppy connection job. I mounted the battery in front of the middle seat and it did start the motor but sometimes I had to give it a couple or 3 tries. It had trouble getting past the 1st compression stroke - motor has 130 psi on both cylinders.

I cut the cables back to the original Johnson ones from the motor which are about 3 ft long and much heavier and moved the battery to the rear seat. Then when i hit the starter it nearly flipped the motor onto the ground. I was amazed - didn't think it had been all that bad.

When I was fussing with the carb problem, on 2 trips, it would start, run for a bit and die when I hit the throttle. I got some frustrated and was cussing....hit the start....hit the start....over and over and over. I was amazed and pleased again - didn't seem to ever slow down and it started a bunch of times in a row.

 

[poorthang]

you could get two lawn mower batteries like wmn002 said. one for cranking, one for everything else. one on each side would be balanced and still lots less weight. i have two i use for my pond boat trolling motor. 10e pelican.

 

[cyclops2]

Lets put 30,000 amp trolling batteries in a 10' boat.

 

[Weldorthemagnificent]

I imagine a lawn tractor battery would do. I use a small solar panel to keep my battery topped up when out for multiple days.

 

[airshot]

Lots of battery options today, I use a small wheel chair battery ( deep cycle) that I bought off Amazon for 40 bucks shipped to my door !! It is used for my 36 lb trolling motor in my pond and also as a battery to run my big boom sprayer for my 5 acer lawn. I have run my TM and boom sprayer for over an hour continous and never had the battery drop in power. About the size of my side x side (atv) battery but is a true deep cycle. Over 5 years old now and still like new..

 

[thill]

https://www.amazon.com/gp/product/B09JNSSSD7/I'm about to buy this battery for $159 delivered. Only 11 lbs!
I'm told that this 50 AH battery has more useable charge than many 100 AH lead acid batteries. I'm planning to use it to power a Garmin 93SV, a Livescope setup, and a few other accessories. Plus, as a backup for starting and the trolling motor. I'm told this battery will handle the task well, and I'm about to find out for myself.

 

[airshot]

What about a charger? Cant use the charging system from your boat motor!! Lipos are great but Don't make a mistake with them, be positive with you connections and charging. One wrong move and BOOM....

 

[gtodd]

I've used a DieHard Gold U1R-2 (340 cold cranking amps/425 cranking amps at 32°F) lawn/garden battery for the last 12 years on my 14' Gregor/15hp 4-stroke Yamaha to power fish finder and downrigger with no problems and as I troll all day, the motor keeps it charged. Though it only got used for a coup[le weeks per year, the first one lasted close to eight years but I will be changing out the second one at/or before five years. I keep it on a battery tender when not in use but the first one died on me even though voltage tested good on the bench before my trip. I didn't realize that I should have considered battery age as a factor. The size and weight: 7.75L x 5.187W x 7.312H at 18.2 lbs. works well for me.

 

[thill]

What about a charger? Cant use the charging system from your boat motor!! Lipos are great but Don't make a mistake with them, be positive with you connections and charging. One wrong move and BOOM....

You are absolutely correct about that, Airshot. There are some that supposedly can handle being charged by certain engines directly, but most need a digital interface which raises the cost a lot.

Better to go with a 20-50 AH AGM battery if that is enough to crank your engine. I use a 12 AH for a little 9.9 merc and boat accessories but that's a pretty small engine.

 

[poorthang]

What about a charger? Cant use the charging system from your boat motor!! Lipos are great but Don't make a mistake with them, be positive with you connections and charging. One wrong move and BOOM....

lol. yep! or even worse, BOOM and FIRE! its why all the electric cars are burning homes and melting asphalt. i had a ducati motorcycle, came with LIPO battery to save weight so they could mount it higher and not affect handling. it rested right between my knutzes.

 

[airshot]

Those who buy EVa's and charge them in their garage are seeing healthy increases in home insurance...those that were flooded by saltwater from the n hurricane just ignite from the corrosion of the saltwater. Lipos are great when used correctly, but no room for any error!!

 

[LDUBS]

Those who buy EVa's and charge them in their garage are seeing healthy increases in home insurance...t

I know some folks with electric vehicles that are charged at home. One has two Teslas. There was no impact to their HO premiums. This may be one of those "internet facts" that never really happened. At least not yet.

 

[poorthang]

I know some folks with electric vehicles that are charged at home. One has two Teslas. There was no impact to their HO premiums. This may be one of those "internet facts" that never really happened. At least not yet.

two things destroy the integrity of your post. nothing personal.
1. in california, how would you know if insurance rates were raised for a particular reason? they are so extremely high, how would you know?
2. remember the hybrids? everyone climed a bajillion mpg and drove 35 mpg on the freeway trying to achieve what was advertised. trying to justify their purchase?, well chances are your buddies are "misinforming" to justify their purchases of electric cars. the insurance companies WILL adjust. they know the fire hazard of the cars and they are learning of the fire hazard of the charging equipment.