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Another battery question

mherrcat

Contributing Partner
What is the difference between a "deep cycle" battery and a "starting/deep cycle" battery? Could a deep cycle battery be used to start an M18 engine if it has the cranking amps?
 

Frank Langer

1984 Ericson 30+, Nanaimo, BC
Mark,

I'm no pro at this, but I have a regular group 24 wet cell starting battery, and two group 27 deep cycle gel cell house batteries. I often start our 5416/M-20 16 hp diesel engine with our house batteries rather than switching to the start battery. I have no trouble starting it with the deep cycle house batteries. I have seen other posts where many people use their house battery to start the engine and only keep the start battery as an emergency reserve. So it shouldn't be a problem as far as I know.

The starting batteries are designed to give a higher initial kick to start the engine, but on a small diesel I don't think that is required. The hybrid start/deep cycle seem to be a compromise between a start and a deep cycle, doing both reasonably well, but neither as well as the start or the deep cycle batteries on their own. A well-running engine doesn't take much to start.

Frank
 
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mherrcat

Contributing Partner
Thanks. I figured about the same. I took my old batteries to WM; the "battery health" tested "0". They said the batteries would take a charge but when a load is applied they would quickly go flat. Which is kinda odd; if they were so dead, why did they start my engine twice the day before I discovered one of them cooking away? Anyway, I also discovered the date code indicated one battery will be 9 years old in Jan. and the other is almost 8 years old; a good time to replace, I guess.

A friend told me Costco had "RV" deep cycle batteries, so we picked up two Group 24 Marine Deep Cycle with more amp hours, more cranking amps and more reserve capacity than the WM batteries I am replacing for a tad over half their price. Now I am sitting here staring at the indicator lights on the charger hoping it shifts into float mode soon...
 
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Rick R.

Contributing Partner
Thanks. I figured about the same. I took my old batteries to WM; the "battery health" tested "0". They said the batteries would take a charge but when a load is applied they would quickly go flat. Which is kinda odd; if they were so dead, why did they start my engine twice the day before I discovered one of them cooking away? Anyway, I also discovered the date code indicated one battery will be 9 years old in Jan. and the other is almost 8 years old; a good time to replace, I guess.

A friend told me Costco had "RV" deep cycle batteries, so we picked up two Group 24 Marine Deep Cycle with more amp hours, more cranking amps and more reserve capacity than the WM batteries I am replacing for a tad over half their price. Now I am sitting here staring at the indicator lights on the charger hoping it shifts into float mode soon...

Mark,

I took my old pickup to WM for an oil change a few months ago and they said my battery needed replaced. Funny, I've had no problems with it cranking the engine. This is in a vehicle that gets used only for hauling dirtbikes, bicycles and such....maybe a few times per week and not a daily driver.

Maybe be there was a directive from the ghost of Sam that they needed to turn a profit in the automotive department...lol!
 
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mherrcat

Contributing Partner
Mark,

I took my old pickup to WM for an oil change a few months ago and the said my battery needed replaced. Funny, I've had no problems with it cranking the engine. This is in a vehicle that gets used only for hauling dirtbikes, bicycles and such....maybe a few times per week and not a daily driver.

Maybe be there was a directive from the ghost of Sam that they needed to turn a profit in the automotive department...lol!

I was confused until I got to the end of your post and realized the WM you were referring to was Walmart, not West Marine. Pretty funny.

My battery charger finally kicked over into float mode, so I guess my problem was the batteries being old and not the charger.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
So many factors, no?

I use two Trojan 27s, "combined starting and deep cycle", for everything. I practice electrical economy when off shore power.

My current notion is to carry the Black and Decker $60 500 amp package in the picture for emergency engine starting. Goes a month or two without recharge, cranks anything hard, has usb ports too.

However, my M25 cranks slow using the house bank.

However furthermore, that may be the glow plug circuit. I am about to troubleshoot the harness for corrosion and maybe add a preheat solenoid.

However even more, I just discovered that only one of my glow plugs gets hot--the center one. This may be cause of the typical 10-second crank time at 60F.

However ad infinitum, is it the glow plugs themselves, or the wiring? I have ordered three new glow plugs in any case.

I am listening if anyone considers the B&D portable starting battery a questionable fail-safe. It has the merit of cheap, is easy to carry and store, has self-test for peace of mind, and requires no yacht wiring or yacht charging system involvement.
black and decker.jpg
 

Rick R.

Contributing Partner
Slow cranking and battery problem solved for me......


A few months ago the admiral and I set off on a week long cruise down the coast. The winds were on the nose in the ICW so we had to do a significant amount if motoring.


We tried to sail as much as possible and had to sail, start the engine, sail, start the engine..... On one start the engine barely cranked which led me to discover I needed a new start switch. Luckily I contacted a mechanic buddy who picked up a new one at WM (not Walmart....) and installed it.


While he was down there, he rewired my starting circuit so it would no longer require holding the glow plug button when cranking. My starting process was to hold the glow plug button for 10-15 seconds then crank. This sucked a bunch of power from my starting battery (AGM) . So much so that I replaced the battery last summer thinking it was faulty.


With the new wiring setup I no longer have to engage the glow plugs to fire the engine (unless it's cold and I want to).


The engine now fires up fast......ah miracles!

BTW I also carry a jump starting setup.
Rick
 

mherrcat

Contributing Partner
I wish I could fit Group 27 batteries in my boat but there just isn't any room. It would be nice even to add an additional Group 24, but again, no room.

I was reading a book about marine and RV 12-volt electrical systems that I picked up at a swap meet a while back. (Funny how I didn't think of that book when I asked my original question!) The answer to my original question seems to be that starting batteries have thinner plates, provide lots of amps for starting and charge faster. Deep cycle batteries have thicker plates, not quite as many starting amps and charge slower; they may also be built to handle vibration better.

Another thing mentioned in the book is that the batteries should be discharged (not completely) and re-charged once every three months. This apparently will help the batteries last longer than keeping them fully charged constantly.
 

Christian Williams

E381 - Los Angeles
Senior Moderator
Blogs Author
I can't say the G27s fit very well in the 32-3, either. Mine are jammed down in the factory box, and protrude about an inch. I put a batten on either end of the lid, raising it an inch, which works fine.

I added a hold-down strap after this pic was taken, but I think the boat could invert without the batteries moving. Prying them out some day will be a challenge.
orig batteries Trojan 27tm.jpg
 

ref_123

Member III
Starting battery options

Well, the theory behind "deep cycle" is that they get thicker plates that do not get killed as fast by deep discharges. As the drawback, they do not have as much wet surface as thin-plated starting batteries and thus do not give as high amps cranking as staring batteries.

If you have some time and a bit of money, do research racing batteries. You can get a small 20Ah battery with 800-1200 amps cranking that would be of a size of a brick or smaller. And light, too. Lithium-iron/ion technology also will last through 20K cycles, so you have a lot of cranking to do :). $300-400 bucks will buy you a battery with built-in charge controller.

On the downside (you knew it's coming, didn't you) this is the kind of battery that consistently burns Boeing 787s down :).

There was a manufacturer for marine use specifically (RaceCell) but they do not reply to the phone or email lately. Still, it turned out there is quite a marketplace for Li/ion batteries in a race car circuits. So, there is a ton of manufacturers and sellers out there. Quite a few of them sell "marinized" versions.

On a lighter side... While researching, I also found a high-end fuel cell solution intended for sailboats. Looks promising. The only issue is that they use methanol! I wrote to them with a common sense suggestion - what are you guys thinking? Where the hell do you expect sailors to find methanol? It's poisonous, and it is a controlled substance in many countries. If you used ethanol instead, one can get a bottle of cheap high alcohol content drink almost anywhere in the world... While I understand a bottle of rum would kill the catalyst, vodka or gin should do OK. And I'd much rather carry fuel that I can also consume :). Will also help with customs - it's no longer alcohol, it's fuel!

No reply so far :). And I do not think I'll ever get one.

Regards,
Stan
 
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mherrcat

Contributing Partner
If you have some time and a bit of money, do research racing batteries. You can get a small 20Ah battery with 800-1200 amps cranking that would be of a size of a brick or smaller. And light, too. Lithium-iron/ion technology also will last through 20K cycles, so you have a lot of cranking to do :). $300-400 bucks will buy you a battery with built-in charge controller.

I have brought up the Race Cell Lithium Iron Phosphate batteries here a few times, but no one seems to have any direct experience with them. I like the idea of the brick-sized battery as a dedicated starter battery; and it could easily fit almost anywhere in the engine compartment. The big question for me (aside from the cost) is if they are compatible with my charging system. Having to install some super high-tech charging system to cope with that battery would be a deal killer for me...

That little shelf about halfway down into the battery compartment that you can see at the top of Christian's pic is what prevents me from using a Group 27 size battery. The shelf in my compartment is about twice the width of the one in the pic.
 
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ref_123

Member III
Mark,

so did I - meaning I brought RaceCell up a few times. As I said, they seem to be out of business.

As for charging, most manufacturers claim they are just fine with 15V or so coming out of the alternator. Most of them claim they can be charged with current chargers in "wet" mode - apparently charging current pattern for wet cells is more inline with what Li/ion wants.

Funny thing is - most of them internally are built from generic Li/ion "C" or "D" type cells! I figured that by searching for pictures of open batteries. I am sometimes thinking - why the heck can't I build a battery for myself? I am not worse with electrics than an average worker at the factory in China that produces all these "brand-name" boxes with the same insides...

Regards,
Stan
 
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