GT9111

Anyone replaced their Porsche battery with a lighter one? I am not too familiar with electrical ohm or amp requirements, so can this actually be done without sacrificing the car's street usage. Please enlighten me.

George Stevens

I have encountered big problems with the smaller battery fitted to the Euro RS.

My retro fitted CD Radio, alarm, and car kit were just too much for it and it would not hold a charge.

I bit the bullet and fitted a full sized regular 964 battery and no problems since.

The smaller battery does save weight but is only any good if you have absolutely no additional electrical equipment

GT9111

So, in other words, not a good idea, huh?

George Stevens

A brand new Bosch Silver RS spec battery lasted only one winter

FlyYellow

Just replaced my battery as well & I went through the same dilema. Here was my conclusion:

Current battery weighed in at 46 lbs.

Options:

Drycell batteries weigh less.
The optima weighs in at 38lbs.
The hawker genesis 1200T weighs in at 36lbs
The hawker genesis 900T weighs in at 28lbs.

I went with the optima. All were capable in my opinion. The 900T had the minimal CCA's that I would have considered.

Cheers,

Boris

GT9111

thanks fo rthe info, guys.

Boris, what's the minimal CCA's that is suitable for the 964? Does this mean that I shouldn't consider any batteries below this CCA level to run a street 964?

FlyYellow

Depends on how cold it gets in your part of the world. I live in California where it doesn't drop below 30F on a cold day. So my requirement for cold cranking amps is much lower than yours. I can live with 400 CCA's. I hope that answers your question.

Cheers,
Boris

Adrian

Guys,
CCA rating is only a factor if you live in a cold environment. Cold Cranking Amperage. Higher is better because this indicates that the battery has high initial current capability. However the CCA number is not a good indication of loaded capacity over time. The critical rating (for the 964) is the Amp/hr capability of the battery which in the USA seems to be missing from the data plate. Here in Europe it is on every battery (well all the ones I have seen). The minimum amp/hr or capacity rating you need for a 964 is 72amp/hr. Now the CCA can change on the same capacity battery. If you own a cab you should have a 88amp/hr battery. The roof requires a slightly stronger battery.
Ask the supplier to give you the actual amp/hr figure for the battery you are using. The 964 has a high electrical hunger (high load) and a low capacity battery will not last long. Colder weather really sorts them out The 964 RS and RSRs were fitted with a 36amp/hr battery and installing this into a standard 964 would not be a good idea. I had huge problems with my 964 when I first purchased it because the PO had installed a 55amp/hr battery.
There is a lot of data on this subject in the archives.
Ciao,
Adrian
911C4

PS: Please remember that battery capacity is the ability to retain its voltage under load. The charging ability of the the alternator/regulator assembly is limited.

DaveS

If anyone in the US is looking for the OEM replacement battery, the manufacturer is Douglas Battery (www.douglasbattery.com 1-800-DOUGLAS).

The correct model number is 48-675 with 70 amps/hr. The porsche dealer wanted $131 for the battery, a local shop has it for $74.

George Stevens

Adrian is absolutely right

As soon as the weather turned below zero my smaller RS battery could not cope with providing enough power to the starter.

Andy Roe

George,

What capacity was the RS spec battery you had? I'm now a little worried as my C4 has a 60 amps/hr! Have I got an RS style battery in mine?

Andy

George Stevens

The standard fit RS lightweight battery is 36 amps the RS touring and RS America had a standard C2 battery