Twin Optima Batteries

[Richardonly]

Gentlemen,

After seeing on this site, the dual optima battery hookup, I have been considering putting a second one in my 1948 Fleetwood.

It would then supply 1600 cold cranking amps.

Does this make the starter crank at a faster speed or are more amps just available?  The only "additional" draw on the battery is for an electric cooling fan for hot days over 90 degrees.  The car is original and still uses the 6V system.

So once again, if the car is starting fine, is this doing anything to make the electrical system stronger or is it more for the difficult starting cars?

BTW, Amazon has them at this time for about $115.00.  I had paid about $145.00 for my 2 month old one.

Thank you, Richard

[LeRoy DeVol]

Richard, I have owned 6 flathead Cadillacs with 6 volt systems and i never had problems with them starting. What you need to do is make sure the cables are heavy duty, attach the ground cable to the bolt that secures the starter, & use a high cranking amp battery. If you still have problems, the starter may need new bushings Or you might have the timing to far advanced.

Lee DeVol

[Doug Houston]

I have 5 Cadillacs with the flathead V8. A few years ago, I finally came to my senses,  removed the starter and installed a grounding stud on the commutator end plate of the starter. This is the piece where the brushes ground on the far end of the starter. I use a 3/8" hex head bolt, set in the plate, clearing the workings of the starter. The bolt must stick out around an inch outside the starter.

Then, back together, ground the battery right to the grounding stud. That takes care of all the engine grounding, and you won't believe what that starter can do.

This is now on three of my V8's, and on one of my V16's. It will soon be on all of my V8's and on the other V16.  I got the clue from the starter on my '41 Oldsmobile straight eight. The battery grounds right to the end of the starter. You never hear a slow starter on those cars, and that's the reason.

One of our guys on this board does use two Oprtimas  in parallel for a V8, and he's sold on it. However, it's overkill, but he's happy, so that's all he needs to know.

I'm a graduate EE, and have worked on military vehicles that start on 24 Volts.  They do ground the starter at the commutator end.

[Scot Minesinger]

I was installing two Optima batteries so that during car shows, could run accessories on one battery and switch over to the other to start the car.  Anyway, what kit on Amazon or site are you guys discussing?  I was just going to use one of those Perko marine battery switches for $50.  Please let me know, don't want to miss some diode that might be needed.

[Jay Friedman]

Doug,

Would it be possible to post a photo or drawing of your grounding stud installed on the commutator end plate of the starter.  I have heard of this before but without a photo or drawing cannot figure out exactly how it is done.  Thanks in advance,

Jay

[Terry Wenger]

Jay:

Doug Houston's complete article with pictures on putting the grounding stud on the end plate of the starter is in th Sept. 1998  Self-Starter on page 20. I have used this stud on my V8's and V16 with great success.

I will copy it and try to get Steve Stewart to put it in a future Self-Starter. It has been referred to many times in this forum.

Terry Wenger

[Scot Minesinger]

The V-16's are positive or negative ground?  The car I'm thinking about is a negative ground 1970 Cadillac.  The starter has a starter to frame ground.  The batteries are supposed to be grounded to body and frame.  There is also a block to body ground strap. 

[bcroe]

A dual battery works for an RV situation, running one (possibly down) with
the engine off, the other to guarantee enough power for starting.  For
normal use, the battery starts the engine & rides through occasional short
high drains, but mostly it just stabilizes the system while power flows from
the generator to the loads.  With everything working properly, the only
need I see for dual batteries is starting a diesel engine. 

If you are running down a battery, you will run down 2 batteries (it will
just take longer).  Bruce Roe

[Philippe M. Ruel]

It would then supply 1600 cold cranking amps.

Does this make the starter crank at a faster speed or are more amps just available?

Just more amps are available. V = RI, so a given V (6-volt voltage) and R (wiring resistance) produce only one possible amps intensity I.

An engine that's hard to start on a new, good quality battery will be hard to start on a zillion batteries in parallel - but you can try it a zillion more times. The problem is in the starter, or more likely in connections, quite sensitive on 6-volt systems as mentioned above - a major reason for the 6-to-12-volt switch sixty years ago.


By the way, no auto wire will hold 1,600 amps. The standard 1/0 or 2/0 gauge wires we have on our cars hold about 200 amps. More than that will be mostly wasted in heating the wire, up to melting it at about 2,000-3,000 amps.

[Richardonly]

Gentlemen,

Thank you for your replies.

There is NO problem with the car starting at all.  It has started every time (always keep your fingers crossed so as not to jinx it.)

I only asked, as I read about the dual system optimas in parallel, and the question as to why has been on my mind.

Any other input as to it's pros and cons?

Thank you, Richard

[Joe G 12138]

       I did this once. I advise against it. Here's why. No two batteries are exactly the same, even if they came from the same run on the same day. Even if one has a slight internal resistance difference, or on has only a millivolt of voltage difference, one will dominate. This is especially true if the car is not driven daily. A very simple circuit diagram would show the stronger one pushing a slight reverse current through the weaker one when the batteries are not on active charge. This condtion snowballs over time. The weaker one gets weaker, the reverse current gets stronger, and the "better" battery discharges more into the weaker one.This will eventually ruin one battery completely, and severely discharge the other (dominant) one if left alone for an extended time. If you are not using the car, the parallel connection should be opened.
       If an 800 CCA optima (which is at least double what these cars had back in the day), one really should look into improving or repairing other electrical, timing, fuel delivery, carburetion or other issues out there first.
        Good luck!.......Joe Gibeault
   

[Doug Houston]

This is one of the prime reasons why it isn't practical nor wise to parallel "identical" batteries. It's done in military vehicles, with 12 volt batteries in both series and parallel to get a high cranking current at 24 Volts. Without some pretty husky 24 Volt batteries (there are none), that's the only way they can get that voltage at that ampere hour capacity. I worked on those trucks for several years, and it's whith that situation in mind, that I don't like the idea of paralleling storage batteries.

No mater what engineering based common sense you write in these places, there is always some character with notions that contradict whatever you say.   

As far as Steve Stewart printing a past article, or even a new one on an electrical situation, forget it. In recent years, the SS has a technical editor, and HE is the source of technical material. A few years ago, I sent an article to Stewart, on a CD, with graphics and all. He neither acknowledged receipt of it, nor returned it to me.  Back in the sixties, I had a serial article in the SS on radio service. That could never be done today. I guess that the SS is going to get a new editor, but I hold no optimism for their appreciation of articles.  While I have kept copies of the SS from issue number one (It was called: "The Standard" then), One of our members here will be getting a lot of my SS copies from the last few years. The SS means very little to me now, and really, neither does the club.