Starting Battery Capacity

[TBOT422]

What's really required to start the M35B? I can't seem to find any specifications anywhere as to CCA required to start the engine.

We have 3 dedicated house battery banks (the 2 original 4D's @185 AH each and another bank created by 2 golf cart batteries that provides another 200 AH) plus a dedicated 12V starting battery. The 12V starting battery has gone bad and I need to replace it. It is labeled at 800 CCA and 1000 MCA. I haven't located a marine starting battery of that capacity yet, but the Sears Die Hard comes close at around 750 CCA but costs over $100. The local auto parts store has marine starting batteries with 450-500 CCA for around $65. What's really required?

We spend most of our cruising time at anchor, and also have a Honda 2000 to re-charge the battery banks if needed.

Thanks

[JerryRoss]

Gary,

I don't know the minimun size battery that could be used for only start but my operator's manual says the battary capacity should be 400-600 cold cranking amps (CCA). My start battary is a West Marine Sea Volt Starting 800, Model 1196708, 110 RC at 25 amp, 800 CA at 32°F, Group 24, 38.5 pounds. I purchased it 9-Feb-2008 from West Marine in Clear Lake, TX. It had a 12 months free replacement and 36 months pro-rata guarantee. It is still working fine but is sealed so I can't check anything. At the time I could not shop around but might try to find a cheaper battery next time. However I might not fight success if this one lasts a few more years. I trickle charge from my house batteries with a Balmar Duo Charge.

[tranquilcat42]

at Costco, found 750 mca and 600 cca marine start battery quite cheaply....Costco in Chicago area has a separate auto area, which is where they are located.
Good luck!

Tranquil hull #187
Teri Weber

[wolfe10]

First question is whether you really want starting batteries. The two 4D batteries that came standard have plenty of cranking amps for the engine and serve as both deep cycle and starting batteries.

But, if you add a separate "start battery" (which we have done as well), my preference is for Optima Spiral Batteries (red post= starting batteries). In fact, in addition to the one in the boad, I just installed two in parallel as start batteries in our motorhome (Caterpillar engine). They are 800 CCA, 1000 CA at 32 degrees F EACH.

http://www.optimabatteries.com./battery_selector/

34/78 (8004-003)

In addition to being high amp, they are also AGM sealed batteries-- a good choice, particularly if you have upgraded your house bank to AGM's. No out-gassing except under extreme overcharging, no water to check, etc.

Brett

[TBOT422]

Brett,

I thought I heard that it was a not good idea to mix lead-acid batteries (4D's) with AGM batteries.

Yes, I'm really looking for a starting battery. We have 3 other house banks, each of which, as you say has plenty of capacity to start the engine unless they happened to be drained too low for some reason. I leave the 4th bank (the starting battery) completely off most of the time when at anchor, so it is always in reserve if needed to start the engine. That's why all it really needs to do is to be big enough to crank the engine over and start when needed. Jerry, seems to say he found something in the manual that mentioned a requirement of 400-600 CCA, so that sounds sufficient for our purposes. I certainly don't want to buy a new "reserve" battery that doesn't have what it takes to start the engine. That said, if I can find a 800 CCA for a reasonable price, it doesn't hurt to have a little more capacity. I'll do some more reasearch this week.

If for some reason, all 4 banks are drained then we also have the Honda 2000 to fire up and re-charge one of the banks to get things started.

Thanks

[wolfe10]

The ideal charging curve and float voltages for wet cell and AGM's are very similar. Gel's are different.

Would agree that all one "technology" is best-- all ours are AGM's. But AGM and wet cell do "play well together".

This issue is more important if you are tying batteries into the same battery bank, particularly if paralleling them. But since you are isolating this battery, will be less of an issue.

With no out-gassing (unless severely overcharged) the AGM's make a good choice for installation in that virtually sealed locker under the port settee.

Brett

[AynB]

Simply put ( perhaps too simply ) : the difference between a 600 CCA battery that is inexpensive and a 600 CCA battery that is more costly is the thickness of the lead plates. Yes, you can purchase a cheap battery at just about anywhere, but it will last only as long as it takes to sulfate the lead and then you have lost the battery. A more expensive battery has more lead, thus will last longer. In the end, and practice bears this out, you will pay more for cheap batteries than you will for their more expensive counterparts. One way you pay every 18 months, the other you pay every 48 months. If you need a new battery and are going to offload the vessel or vehicle, by all means go cheap to make the sale. On the other hand, if you yourself are going to rely on that battery, then pay now and sleep easy.
Just for grins, take a portable scale to Costco and weigh the cheap battery, then take the same scale to a prominent battery retailer and weigh the same CCA battery - I think that you'll see that there is a huge difference. I did.
Al

[TBOT422]

Al,

You do not always get what you pay for. The 800 CCA battery at West Marine costs $145 and weighs 45 lb. The 800 CCA battery at Advance Auto Parts costs $85 and weighs 45 lb.

They're probably made by the same vendor.