Re-battery-ing

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potter water

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C Dory Year
1997
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R-21 Tug
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Poopsy
Going to replace the batteries in Still C-razy in another month. I've been very interested in lightening up the rear end of the boat, plus, the batteries in it are about 4 to 5 years old.

I've been fascinated with the comments of the folks who've gone to motorcycle batteries. I REALLY like that idea. 15 to 17 lbs each as opposed to 23 or so pounds for the automotive style crankers really appeals. I'd rather carry the weight with a relatively large house battery.

Anyone out there have a real downside to a pair of those smaller batteries to crank my two Suzi 50 hp injected engines??
 
I don't have any downside, just another happy user. I suppose you could say that with fewer cold cranking amps you could run the battery down sooner. Not an issue for me for these reasons: The engines start quickly so no need for a lot of cranking; I can put both start batteries in parallel to combine cca, I still have (in my case 2) gp24 batteries to use with a little moving of wires, and finally, with the small engines I could (maybe :roll: ) manually start them. Mine fit into one group 27 battery tray.
 
I have carried several of the AGM PWC batteries as both starting batteries in larger inflatables (25 hp plus engines), and for emergency start purposes.

They will certainly start the smaller engines with ease. However, you still have the need for house batteries and the demand of electronics, lights etc. You can put an AGM battery in the main cabin if you wish--If I was replacing the original I would tend to go to high capacity Group 24 or Group 27 for the 22. The larger boats I would go to the group 31. Remember that the "group" number is only a case size. Group 24 can run from 65 amp hours up to 120 amp hours depending on brand, quality and weight (higher capacity batteries will weigh more). The minimum wt of a group 24 will be in the 34 lb category, on up to 50 lbs for the highest capacity group 24 battery. You are not going to find any of the quality group 24 battery (which the boats come with) at a weight of 23 lbs.

I think it is wisest to stay with at least equal size group 24 batteries for the house and engine start. This will allow equal charging with both batteries.
 
thataway":3py25im6 said:
I think it is wisest to stay with at least equal size group 24 batteries for the house and engine start. This will allow equal charging with both batteries.
Click to expand...

That's what I just finished doing today. I got 2 Interstate SRM-24 deep cycle batteries which are also rated for starting, so I can use an identical pair. I also used the Blue Sea Add-A-Battery which comes with a nice on-off switch that turns on and off two separate circuits (house and start) instead of running both circuits off the same battery like an 1-both-2-off style switch. It also comes with an ACR that selectively bridges the batteries for charging when one or the other of the batteries has an elevated voltage level (a.k.a. is getting charged).

Very nice system, but it took some work to get it all set up.
 
What is the amp hour capacity of the pwc/motocycle batteries that are working well for you who are using that type battery. (more the better?)
 
The motors manufacturers have a minimum cold crank requirement per engine size. Might check that out . They require a battery capable of supporting the EFI fuel injection system with some reserve power .
Marc
 
Wefings":24uhcv0k said:
The motors manufacturers have a minimum cold crank requirement per engine size. Might check that out . They require a battery capable of supporting the EFI fuel injection system with some reserve power .
Marc
Click to expand...

I'm sure Marc has two important points here:

1. "The motors manufacturers have a minimum cold crank requirement per engine size."

Too small of a battery, and the voltage drops quickly upon starting, particularly during cold weather and repeated attempts. Low voltage means more amps are required, which is a vicious cycle for a weak battery, lowering the voltage available further. The problem is that higher amperages at lower voltages produces more heat and less torque in the electric motor, shortening armature and brush life. New armature = $300-$400 + labor. (est.)

2. "They require a battery capable of supporting the EFI fuel injection system with some reserve power ."

The EFI is essentially two systems. One is the computer with all it's sensors that make decisions, the other is the injector fuel control that operates the little solenoids that pulse the fuel to the intake manifolds at the ports.

How well does your computer run on low voltage? Nuf' said!

The second problem is that those little solenoids take quite bit of power, too. Quite a bit of the extra alternator output of the new motors is actually used by the EFI systems, probably between 5-10 amps.

Most all sophisticated electronic devices don't like low voltage, period.

Worse yet, if your alternator quits, you can go as far as you can until the battery voltage drops below a critical level.

Ever watch a NASCAR race with a competitor with a bad alternator? (Of course, they have a lot of other electrical demands besides ignition, and now fuel injection). The car goes as far as the battery allows, then goes dead.

Hope you're not up in the Inside Pasage or offshore chasing the Albies with a dead alternator and battery.

Not trying to be a fear monger here, just trying to make a good argument for decent size in battery capacity, which I prize highly!

Relative allegory: "Never send a boy to do a man's job." :lol:

Joe. :teeth :thup
 
"Most all sophisticated electronic devices don't like low voltage, period.

.......

Not trying to be a fear monger here, just trying to make a good argument for decent size in battery capacity, which I prize highly!

Relative allegory: "Never send a boy to do a man's job."

Joe."
Click to expand...

What Joe Said.

I have 2 Group 27 Interstates, Deep cycle marine. They seem to do the job, (electronics, a few lights, start and run, and my CPAP at night). Not sure which would be worse, to be out of CPAP or out of start power in the morning :evil: :thdown

Yes they do weigh some, and it is aft ( lazarettes, both sides ), but the boat sits pretty level on the water, and my CPAP works all night :smile :thup

Harvey
SleepyC :moon

1_10_2012_from_Canon_961.sized.jpg
 
Another point which Marc was making, is that it is not the Reserve Amp hours which are important. It is the Cold Cranking or Marine Cranking Amps of the battery. The Reserve capacity is more important in the house battery aspect as to how long it can run electronics. Many folks do not realize that the battery voltage may drop to 6 volts when cranking--as a follow up to Joe's point.

I have started some large diesels with a PWC battery--but you only have one shot....and it is only for an emergency.

I also agree with Harvey's approach, My boat has Group 24's, but when I replace them they will be group 27's at highest amp capacity I can find.

20 lbs in the stern does not make that much difference in handling--and you can always move the house battery forward.
 
By the way, Those Group 27's in the lazaretttes ..... Had to be put in with shoe horns and lubrication. One thing for sure, they won't fall out if the boat turns upside down :roll: I didn't put them in, my mechanic did, and He is a VERY BIG guy.

Harvey
SleepyC :moon
 
hardee":m56114kx said:
By the way, Those Group 27's in the lazaretttes ..... Had to be put in with shoe horns and lubrication. One thing for sure, they won't fall out if the boat turns upside down :roll: I didn't put them in, my mechanic did, and He is a VERY BIG guy.

Harvey
SleepyC :moon
Click to expand...
Tell me about it! :x I just completed a major project in the %*#@ extremely tight starboard lazarette. No fun! Details in the "What did you with your C-Dory" thread.
 
Jazzmanic":3jjzhsl7 said:
I just completed a major project in the %*#@ extremely tight starboard lazarette. No fun! Details in the "What did you with your C-Dory" thread.
Click to expand...

Me too. I rewired the starboard compartment (group 24 battery, switch, ACR, 50A house breaker, 60A fuse) and port compartment (group 24 battery, fuse). I can't imagine getting a group 27 in both sides with all that hardware in there.

I don't see your project in the "What did you do with your C-Dory" thr
 
ferret30 and others,

I just completed posting the details in that thread. I do have a question. I noticed you and others, notably Dr. Bob mentioned that the Add-A-Battery system should be installed with the same type of battery. My batteries are both Interstate Group 24 but one a cranking and the other a deep cycle. I looked at the chart and I believe they have the nearly the same specs as far as CCA and MCA. I believe I have the Cranking/Starting 24M-HD (but will check) which has a CCA=500 and MCA=625 vs the Deep Cycle/Cranking SRMN-24 which has a CCA=550 and MCA=690.

With my pair, is it necessary to have exactly the same battery or will mine be fine? It worked fine with the standard Blue Seas battery switch. And I didn't see a section in the Blue Seas documenation that said the batteries need to be the same. Just curious.

Peter
 
Jazzmaniac,

I think it should be fine, especially since they are kept on separate circuits with that type of switch, but if I were you I'd actually call Blue Sea. I called last week and was surprised at how easy it was to get in touch with an engineer. He gave me some assistance over the phone and worked through my plan and confirmed it looked ok. I have 2 of the SRM-24 batteries (both deep cycle&cranking).

Blue Sea is in Bellingham.

FYI, here's my final layout. This doesn't represent the actual placement on the boat, just the connections and components:

wiring_001.jpg
 
Similar types of batteries, close to same specs should be fine.
 
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