Must move the battery cut off switch

Doug,

I am just curious, why did you replace the two Optima batteries?

Did they discharge beyond their ability to recharge?

Are they ancient?

I ask because an Optima 6V Red Top should be good for between 8 & 10-years.

I did the same a few years back, but that was for a weekend when I needed to run he car.

I had left the ignition ON!    EESCH!

My two charged up within a few days and the standard NAPA wet-cell 6V battery is now on the shelf awaiting my next screw-up.

I now have two Optima batteries in my battery box, but only one is hooked up and the other sits idle as a backup.

You might want to put them on a serious charger (NOCO Genius-10 – https://no.co/genius10)

Again, I am just curious.

Good luck!

Peter

Arnold,

Below are a couple of tables on 6 volt batteries. The first is a size table vs. Group number for 6 volt batteries. The second is out of PASB 2019-2 which is a comparison of AGM (Optima) batteries vs. regular flooded lead/acid batteries. The full article includes the pro and cons of AGM batteries vs. lead acid.

I use a Group 4 in my Series 36 cars, although this may be too large for your 1930.  Part number is Carquest 4-30. Check the table and see what size fits your battery box correctly.  My group 4 is slightly smaller than the dimensions in the first table, so it is probably worthwhile to confirm the dimensions of any battery you are going to buy. I think there is probably some difference in size and capacity between different manufacturers.

I have not put an Optima in my cars, mainly because my batteries always seem to fail when the sale is 6 months away.  The flooded lead-acid battery in my touring car is 7 years old and still working fine.  I do occasionally charge it with a desulfation battery maintainer.

Dave

Hi Doug and others,

1.  I have a battery cutout switch on the floor under the driver’s seat in my ’34 convertible coupe  (ok because it’s easy to lift the small seat); and on the short vertical riser board under the front of the front seat in my ’33 convertible sedan, nearly out of sight because the board is recessed.

2. Regarding batteries -The most important spec to me is Ampere-Hours (A-H).  It is directly related to the size of the battery, and how LONG it will crank. (Almost any battery will start a car several times.)  Example: a 50 A-H battery will supply 200 amps (typical starting current) for 15 minutes, 50 amps for one hour, or 1 amp for 50 hours.  The more modern spec of “Reserve Capacity” (RC) is related to A-H by specifying the number of minutes a battery will last when supplying 25 amps.  So a 50 A-H battery will have a RC of about 2 hours, or 120 minutes.

Single Optimas have a rating of 50 A-H, and a RC of 100 minutes (=42 A-H, due to different levels of discharge involved in the specs).

Double Optimas thus have a 100 A-H and 200 minute RC rating.

I use an Interstate group 4xhd commercial battery (about $140) in my V12, which has an RC rating of 295 minutes.

So, I can crank the engine about 3 times as long as a single Optima, and about 50% longer than a double Optima.   If my generator stops charging while I’m driving on a mountain road at night (25-30 amps draw including brake lights) I have almost 5 hours, vs. 3.3 with double Optimas, or 1.6 hours with a single Optima.  Of course, I have to check water level every 6 months. (I do use single Optima batteries on other cars  because of their low current draw.)

The 4xhd A-H rating is not listed, but is estimated to be 150 A-H.  The 1933 P-A salesmen’s “Green Book” lists the battery for the 1933 V12 as “…Willard 160-165 ampere-hour battery”.

Cheers.