Battery: is Interstate Group 24M good enough?

[rnln]

Hi guys,
I hope everyone had good Christmas and new year days.
I have a question on battery, has anyone use weaker/smaller battery on your 911? Is this Interstate Group 24M good enough for our car? Does anyone know the required CA/CCA?
Thanks.

[Dpmulvan]

That’s a deep cycle battery,

[eastbay]

I'm currently running a Group 48, bolts right in. Have run a Group 24 previously just to get the terminals away from the fender.

Even though I always buy the highest CCA on the shelf per my size, I don't think CCA is too important as the motors are so small and I don't live where I need to start the car at 0 degrees.

Lots of options.

[darrin]

Originally Posted by rnln

Hi guys,
I hope everyone had good Christmas and new year days.
I have a question on battery, has anyone use weaker/smaller battery on your 911? Is this Interstate Group 24M good enough for our car? Does anyone know the required CA/CCA?
Thanks.

Even a VERY small battery (e.g. the odyssey 925) will have no real problem starting our cars. Issue (IMO) is reserve capacity -- e.g. how long the battery can power an unforeseen load (dome light, glove compartment light, etc. left on) -- a Group 48 or 49 battery has the reserve capacity to start a car after leaving such an unforeseen load on overnight - while a smaller battery may well not (and would cause the battery to discharge a LOT further in the process, compromising its lifespan).

Thus, I consider a group 48 battery (still smaller than the group 49 boat anchor that came stock on my '86) to be a cheap insurance policy. AND, it bolts right onto the battery tray using the stock clamp w/o issue.

I'd also recommend going with an AGM-type battery, which captures the battery's acid in a fiberglass mat and greatly reduces the chance for battery leakage.

Finally, a deep discharge battery (like the one pictured) is optimized for powering RVs, boats/etc., where it is tasked to provide a lower amount of power for a longer period of time -- better to avoid deep discharge batteries and go with one designed for automotive use. I've had great luck with the various house brands sold by our various FLAPS (friendly local auto parts stores)

[Mark Salvetti]

Our cars have two threaded holes for the battery clamp. One is for a shorter battery than the other.

I can never keep this straight - is the Group 48 for the shorter hole, and the Group 49 is the big one? It looks like a Group 48 is about 3 inches shorter than a Group 49.

Mark

[Sajan]

I put this in in my 87. it's the smaller one. no way i am shoving the bigger version size 49 in there.
BCI Group Size BCI No. 48
https://www.napaonline.com/en/p/BAT9848

[PeteKz]

Backup what Darrin said. Just about any battery for automotive use will start our older 911's. If you had something 964 or later, I might be concerned about parasitic drains if it sits for a long time, in which case you should put a battery tender on it. In my case (1973T) I've started it with a motorcycle battery. Since my car originally had 2 batteries, I replaced those with one NAPA group 70 in the right front battery box. the Group 70 fits snugly in that battery box. This type has the GM side terminals, so no danger of shorting them to the fender or top of the battery box. The spare tire further ensures the terminals are protected and the battery is safely retained. There's about 1/2 inch clearance between the spare tire and the screw-in regular terminal adaptors that I put on the GM side terminals so that I could clamp on the battery connections in the original wiring. 4 years and it's working great.

[Rtrorkt]

running this one in my 69 RS Clone with a 3.2l Just fits in the left front battery box with mm to spare

[Rtrorkt]

sorry link did not transfer for some reason. It is an Odessey Battery PC1200

[na2ub]

I've been running the Jack Olsen special, in my rig for the last 6 years or so. Only weighs about 8lb and starts the car down to about 32F. (Below 32F is a no go).

Don't know how many CCA it is, as it's for a wheelchair or lawnmower battery or something.

[Packin4]

Group 24 battery wil be taller than "stock" battery. If you want a smaller (not as long) battery that uses the stock clamp hold down and terminal location get Group 48 (same as H6). Plenty of CCA/amps. My local Costco carries Interstate batteries in wet acid or AGM with 3yr no proration warranty. My last Interstate lasted 10+ years (with battery tender).

[EauRouge]

I use a Costco 51R battery (i.e. Honda) in my 930

[RFP]

Originally Posted by Sajan

I put this in in my 87. it's the smaller one. no way i am shoving the bigger version size 49 in there.
BCI Group Size BCI No. 48
https://www.napaonline.com/en/p/BAT9848

on your recommendation, I just installed this NAPA battery in my car. I'm confident it will provide years of dependable service. Thanks!

[darrin]

yep, group 48 AGM is the way to go! -- Napa's good, but other FLAPS house brands will be just fine too

[rnln]

I always use group 46 and 48. I *****ed every time to have to get it out of the car. It is too big for the spot with a bunch of wires on top of the spot. I wish I can use smaller battery.

Originally Posted by Sajan

I put this in in my 87. it's the smaller one. no way i am shoving the bigger version size 49 in there.
BCI Group Size BCI No. 48
https://www.napaonline.com/en/p/BAT9848

[rnln]

Interesting. Any info on it, brand model etc?

Originally Posted by na2ub

I've been running the Jack Olsen special, in my rig for the last 6 years or so. Only weighs about 8lb and starts the car down to about 32F. (Below 32F is a no go).

Don't know how many CCA it is, as it's for a wheelchair or lawnmower battery or something.

[darrin]

Originally Posted by rnln

Interesting. Any info on it, brand model etc?

Poor Man's Lightweight Battery

[tschall]

Expensive Anti Gravity Group 48 is light weight, perfect fit, and so far (over a year and a half) reliably starts ALWAYS even in 0 degree weather. Being LifePOE battery it is extremely light. With no parasitic drain in our car, it has sat for as long as 3 months in winter with zero problems. Add the battery Tracker app to monitor a host of online feature/feedback from your car & battery. Extremely useful. Would not like to NOT have that functionality... can't recommend anything better in my experience.

[WolfeMacleod]

Originally Posted by tschall

Expensive Anti Gravity Group 48 is light weight, perfect fit, and so far (over a year and a half) reliably starts ALWAYS even in 0 degree weather. Being LifePOE battery it is extremely light. With no parasitic drain in our car, it has sat for as long as 3 months in winter with zero problems. Add the battery Tracker app to monitor a host of online feature/feedback from your car & battery. Extremely useful. Would not like to NOT have that functionality... can't recommend anything better in my experience.

Just dropped one of those into my Cayman a few weeks back. Very impressed by how it cranks now. Thinking about my 911, too.

[darrin]

Originally Posted by WolfeMacleod

Just dropped one of those into my Cayman a few weeks back. Very impressed by how it cranks now. Thinking about my 911, too.

Suspect the difference in cranking stems from the difference in voltage of a lithium battery vs a lead acid battery. A fully charged 12v lead acid battery puts out 12.6v (its "resting voltage"), while a fully charged 12v lithium battery puts out around 13.3v. The higher resting voltage of a lithium battery would, by definition, spin a dc motor a little faster, causing it to appear to crank "better"