All About Boat Batteries

[NiceAft]

Just read this article in a B.O.A.T.U.S. e-mail.

https://www.boatus.com/expert-advice/ex ... aign=eline

[Inquisitor]

I wish I had read something like this years ago. I might have kept my batteries in better shape.

House Battery
I've killed two house batteries in 12 years... probably due to sulfation (according to this article). Although, my brother-in-law, being a professional fisherman, goes through top quality AGM's in one year. For my third set, I'm going with Lithium. Although more attention to charging is necessary, it it automated by electronic circuitry. I'm also doing it DIY from China which gets it at the same up-front price as eBay AGM's. It used to be that you had to take into account that they'd last longer and would only be "cheaper" after you've bought your second set of AGM replacements. No longer.

Starter Battery
I have a deep cycle battery for starting the motor. Although it shows its maintains a full charge, it seems to struggle starting my 60 Hp Mercury. I'm not sure if the battery is weak or just its CCA is not up to the task. I may just replace it with a standard starter battery.
I originally assumed that I could just use the Lithium house battery. Although, it will be capable of 560 amps (continuously) I'd have to add some extra hardware to keep the lithium battery from destroying the motor's alternator. I decided to keep the two systems totally separate except to run a trickle charger from the house to the starter.

[Neo]

My Mac came with an AGM and a cranking battery, both of similar age. The AGM battery went faulty first and it did so in a really weird intermittent and progressive way. I was out on the lake one day and made the mistake of selecting 1+2 on the switch and the AGM drained all the life out of my starting battery
Marine batteries are expensive over here so I tracked down a battery importer (who had been in business for over 20 years). He sold AGM batteries but he advised me to just buy cranking batteries (in contrast to what the article advises), because, when looked after, they are the least likely to give trouble in the longer term.
In the past I've had many car and boat batteries go soft on me but this last year I've managed to bring some back to life with an intelligent high voltage pulse charger.... BUT NEVER use one of these when the battery is still connected to other things .... I did not get the same good results using a Reverse Pulse Charger which often claim to cure sulfation.

Let us know how you go with the Lithium battery? .... Prices are falling but still too expensive for me.

It's worth investing in a cheap $25 battery load tester to see what happening with your battery. ....https://tinyurl.com/yyepz7k3 But if it checks out Ok I'd be checking for loose or corroded connection issues from the battery all the way to the starter motor
I've had starting issues in the past and discovered my starter motor was not earthed properly against the engine casting ... many low conductivity points can be diagnosed by feeling how warm points get after you've been cranking the engine a few times with the spark plug caps disconnected.... Best of luck

[Inquisitor]

When I started the refurbish, I had the batteries out to charge them and am sure its a good connection on the battery side. And... it was in the shop to have the engine worked on and the mechanic didn't mention anything, but I will double check the connection at the motor.

As part of my Lithium project viewtopic.php?f=8&t=28020#p346304 I'm getting a device that will allow me to check capacity under load (up to 100 Amps). I can use that to test the motor battery.

[Russ]

Ray, thanks for the article. BOATUS magazine makes it worth the membership alone.

I have a deep cycle battery for starting the motor. Although it shows its maintains a full charge, it seems to struggle starting my 60 Hp Mercury.

I would strongly check other things like connections/cables etc. besides the battery. It is possible the battery is failing, but I would doubt it unless you have a bad cell. Does the motor star with another battery?

Our motors will start with a motorcycle battery. They don't require a lot of "cold cranking amps".

I keep a small battery jumper pack just in case.

[Russ]

Marine batteries are expensive over here so I tracked down a battery importer (who had been in business for over 20 years). He sold AGM batteries but he advised me to just buy cranking batteries (in contrast to what the article advises), because, when looked after, they are the least likely to give trouble in the longer term.

This might be good advice if you ONLY used it to start the motor.
However, the purpose of deep-cycle batteries on boats is to prevent sulfidation when the battery is discharged and subsequently recharged.

I now have 2 deep cycle Wal-Mart batteries. Outboard doesn't need cranking amps, but I do drain the house battery often. Then I can trade them like rotating tires. Seems to work well so far.

[dlandersson]

I use marine 12 volts, and I expect to replace them every 5-6 years.

House Battery
I've killed two house batteries in 12 years.

[NiceAft]

I have has two AGM's for maybe four years now. As they are being charged all winter, I am always checking the volts and % charge. They never get over 74% charged sitting in my driveway. If they go bad, I don't look forward to replacing them. If I remember correctly, each weighs about 60 Lbs. (27.2Kg).

[Neo]

... the purpose of deep-cycle batteries on boats is to prevent sulfidation when the battery is discharged and subsequently recharged.

Yep I know the theory I but I've not experienced that and the guy I spoke to seem to have lots of experience with this. Different experiences can sometimes be the result of different environmental factors.... For example, it gets dam hot here .. and not that cold here too

Then I can trade them like rotating tires.

Trade them?? ... Please tell me more?
Someone gave me $20 once for an old battery. But I've never seen a trade up scheme where I live .... that's not just a scam

They never get over 74% charged sitting in my driveway.

How are you ensuring they never get charged over 74%?

[NiceAft]

How are you ensuring they never get charged over 74%?

It's not that I am insuring this, it's that the gauge I installed to show voltage and % charged on each battery show me this. When I start the engine during warmer weather to run it for about fifteen minutes, the charge goes up. When I do this a few times, it gets up to over 90%. In the cold of winter I can not do that.

Fifteen years ago, when I bought my , I had the dealer install a battery charger. Today the technology may be different, and would be able to maintain a greater charge About three years ago I installed the gauge. It made life easier by not having to guess what the state of the batteries are.

[Neo]

... it's that the gauge I installed to show voltage and % charged on each battery show me this. When I start the engine during warmer weather to run it for about fifteen minutes, the charge goes up. When I do this a few times, it gets up to over 90%. In the cold of winter I can not do that.

Ok so I'm assuming your gauge is set for 13.8V = 100%??

I try to look at "Charge" (holding capacity, which voltage is an indicator) many hours after the charging has taken place because even an "off load" voltage will always drop after a few hours. "How much" and "how quickly" it drops can be a good indicator of battery health too.
The only time I've seen a battery hold a high voltage (for days sometimes) is after using a high-voltage-pluse charger .... But I personally suspect it may damage the battery if used on a regular basis and is more suited as a restoration tool.

[NiceAft]

Awhile back, I discovered the plug came out of the wall socket. I have to assume that there was no charging for several days. When I checked the gauge, it showed the batteries down to about 24% (if I remember correctly) it might have been slightly more.

[Neo]

Awhile back, I discovered the plug came out of the wall socket. I have to assume that there was no charging for several days. When I checked the gauge, it showed the batteries down to about 24% (if I remember correctly) it might have been slightly more.

That's 3.3Volts!
Hmmm ... that sounds stuffed to me... sorry

[NiceAft]

Is “stuffed”, Australian for “not good”

Voltage was never that low, so must have been a higher %. 71, that’s my excuse.

Now I’m going to unplug the power cord for two days and see what the gauge shows.

Hopefully I will report back Thursday morning (East Coast U.S. time).

[Neo]

Is “stuffed”, Australian for “not good”

Voltage was never that low, so must have been a higher %. 71, that’s my excuse.

Now I’m going to unplug the power cord for two days and see what the gauge shows.

Opps yes

Ok good luck with that ... battery maintenance is kind of a black art ... But I am curious to know how you Charing Gauge is calculating it's measurements... It could be that 8 volts is 0% (pretty stuffed too ) making a delta of 5.8Volts for the 100% range. Which by my calculations would make 24% = 9.4Volts (almost pretty stuffed ) but I'm most likely wrong.