how many battery cca needed

[Jasper_ghost]

Suzuki DF300 manual recommand a 135AH battery but no info about cca. I intend to use two separate batteries but with a switch between (and extra start amps if needed).

To save weigth I consider following
A "super quality" 100AH start battery (with let say 900cca) for start and a 70AH for others.

Is this recommanded or any good/bad experience or advise with batteries

[PAR]

Generally, you match your battery needs against the draw you expect, which is based on the devices you have installed and the typical amount of time they'll be used, per charging cycle.

If your engine needs a 135 AH (reserve minutes in Amp Hours @ 25 amps draw until the battery reaches 10.5 volts) then you'll need something like a group 27 with at least 135 AH which typically have a CCA of 500 and up. Exide # ST27DP700 fits this bill easily with 160 AH at 575 CCA. A cheaper alternative is West Marine's "Sea Volt" group 27 # 27M6, which provides 650 CCA and 182 AH.

The house battery should match the needs of your equipment, with a little "expansion" room for accessories that might get installed at a later date.

Using a smaller starting battery isn't particularly wise, you'll just burn it up quickly. Batteries of this size usually weight about 50 to 55 pounds and you'll not save much weight by switching to a slightly smaller battery, maybe a few pounds is all.

[Jasper_ghost]

I intend to isolate start battery, so dont care about AH but only how many CCA needed. Also i want to save weigth, so think the Exide Nautilus 61500 Marine type with 115Ah and 950CCA could be a good choice...

[charmc]

For isolated starter use, focus on CCA. Anything above 500 amps should start that engine easily, but a battery with a higher CCA rating should last longer. PAR is correct when he says you won't save much weight by using a smaller starter battery. The small amount of extra cost and weight buys you big insurance that the engine will start whenever needed. No harm in using a slightly lower AH rating for starting, so long as it is top quality marine rated and has a high CCA rating, but don't look to your battery as a weight saver. The differences in weight are small, so focus on capacity and quality. Even a backup starter battery would not cost as much in purchase and extra fuel as a call for a tow, especially in rough weather. For deep cycle accessory use, the same goes, but focus on AH rating. I suspect that the Suzuki recommendation is for a single battery doing double duty.

[redtech]

the suzuki recommended battery is 770cca 239rc 130ah

[Jasper_ghost]

Thanks, but please explain what 239rc mean.

I have got both service and installation manuals but no info there. Where did you get the info from?

[PAR]

RC (Reserve Capacity), is the amount of time a battery can sustain a 25 amp load before it drops to 10.5 volts. A battery rated at 120 RC will operate for two hours (120 minutes).