Multiple Batteries

[kclark]

As was talking with an old timer yesterday about how he had is 6 volt car wired up. He has 2 6volt batteries in it and somehow he has the ability to use both to crank the car and he can switch to use Battery A and if needed, he can switch to Battery B. He has one of the green knobs on the floorboard to do the switching. I was wondering if anyone has done this as my car ('29 Dictator) runs fine during the day, but it will not have good power when it gets dark enough to have to turn the lights on. I've read one article and it intrigues me but not sure if keeping both 6 volts together all the time like it appears to be stated with be bad.

 

Anyone else done something like this?

 

 

[Matt Harwood]

It sounds like he had two 6-volt batteries wired up in parallel, in which the system remains at 6 volts but improves the cranking performance by pushing more amperage--essentially a bigger battery. It's overkill in many cases unless you have a big cubic inch engine that's particularly tough to turn--your car started on a single 6V battery when it was new, it should do the same now. If you are having problems at night, your generator might not be putting out enough amperage, which is adjustable. This is a balancing act that many of us face and it really depends on how much night driving you're going to do. If you turn up the generator's output to keep up with the headlights, you're going to over-charge the battery when you're not using the headlights. Or, as seems to be the case now, if you turn it down so that you're not boiling the battery, your charging performance with the headlights on will suffer.

 

This is a common issue on cars with unregulated electrical systems. I have my 1929 Cadillac's generator running about about 10 amps max, and at that level the headlights and generator just about fight to a standstill at night and at idle it shows deep discharge. I have to turn off the headlights to energize my electric overdrive, for example, then turn them back on once it is engaged. There's a limited amount of electricity to work with. I am running an Optima battery, which turns it over easily and doesn't mind running at a slight discharge for a few hours--there's always plenty in reserve. If I'm on a long daylight drive, I will sometimes turn on the parking lights to burn off some of the excess electricity and save the battery from over-charging.

 

I'm not quite understanding what you mean by "it will not have not good power when it gets dark." Does that mean it's not charging with the headlights on or the engine is actually misfiring due to inadequate spark energy? The former is probably normal and the latter is not. I also don't have a clue what this means: "not sure if keeping both 6 volts together all the time like it appears to be stated with be bad."

 

My guess is that your electrical system is performing normally. Your generator probably can't keep up with the lights at night, and definitely not at idle and most unregulated cars are similar. If you do a lot of nighttime driving, you might want to consider adjusting the third brush of your generator for a bit more output. If you don't do much driving at night, then perhaps leave it as-is (as long as your battery is staying charged with lights off), and just accept that when you run at night, the battery will discharge slowly. Unless you're driving for hours in the dark or doing it every day, it is unlikely that it will kill the battery and the generator will top the battery off next time you drive it in the daylight.

 

Also, the very first step should be to make sure your battery cables are big enough and your grounds are good. That can only help no matter what your electrical problem is.

 

Before going to two batteries in parallel, I'd try an Optima 6V battery instead. I bet I could drive my '29 Cadillac a quarter-mile just using the starter and that battery. It's STRONG.

Edited November 22, 2017 by Matt Harwood (see edit history)

[Grimy]

I run a pair of Optimas in each of my 8-cyl Pierces (1930, 1934, 1936) not for starting benefit but for RESERVE capacity for nighttime driving.  Long stretches at constant speed will not deplete your battery nearly as much as stop and go driving.  I've upgraded tail and stoplight bulbs for increased output with different number (brighter but higher consumption) incandescent bulbs, so the amperage used in nighttime driving is greater than stock.  Each of these cars originally came with a Group 3 battery with 140 amp-hrs (AH) reserve capacity (RC).  Each Optima typically has a 100 AH reserve, so a pair in parallel (full time) will have 200 AH.  The 1930 & 1934 have simple cutouts and 3rd brush regulation, so Matt's explanation is exactly why I run a pair--to avoid having to change the 3rd brush setting (or run with lights on during long daytime runs); the 1936 has a two-stage regulator with a 3rd brush.  Interestingly, the 1918 Pierce has factory regulation, so despite its 525 cid I run a single Optima in that one.  Really, my only comment to Matt's excellent post is a caution that a single Optima has a Reserve capacity of 100 AH, which may be sufficient for many cars with single taillights.  So please see what RC was specified for your OE battery unless you have changed your lamp consumption.

[kclark]

16 minutes ago, Grimy said:

Long stretches at constant speed will not deplete your battery nearly as much as stop and go driving.

 

 

This may have been my problem the last 2 times I had it out. It was for Christmas parades. Ran great during them, but afterwards I had a little trouble.

[Spinneyhill]

Did they specify battery reserve capacity in 1929?

 

My 1930 Dodge Brothers Eight Instruction Book specifies a battery of three cells, 15-plate, six-volt, 100 ampere-hour capacity... So it looks like they specified the RC but not the cold cranking amps (CCA)!

Edited November 22, 2017 by Spinneyhill (see edit history)

[kclark]

12 minutes ago, Spinneyhill said:

Did they specify battery reserve capacity in 1929?

 

My 1930 Dodge Brothers Eight Instruction Book specifies a battery of three cells, 15-plate, six-volt, 100 ampere-hour capacity... So it looks like they specified the RC but not the cold cranking amps (CCA)!

 

I have know idea one that one. I don't have a book like that. I just ordered 2 optima batteries and I'm looking at battery switchers but I think I'll just wire them up parallel. 

[Grimy]

I'm old enough to remember the pre-alternator days when one had to keep an eye on the charging rate of one's generator during nighttime stop and go driving.  It certainly helped that 35 amp generators became the norm shortly before WW2, but my teenage daily drivers included some 3rd brush unregulated systems.  It can be hard to imagine what an advance alternators (charge at IDLE!) were when they arrived in the early 1960s.

[mike6024]

 

 

 

There are marine battery swwitches, 1, both, 2 or off

 

https://www.westmarine.com/buy/blue-sea-systems--e-series-compact-battery-switch-off-1-both-2-no-alt-field-disc--3831393?

 

I think you use "both" when you know you are in a charging situation. When discharging just use one or the other so you keep one in reserve.

 

 

 

 

[Grimy]

I can see the usefulness, Mike, but not in my particular situation.

 

kclark, here's how I have the dual Optimas arranged in parallel in my 1934 Pierce.  Both + (postive) ends are at the right, and the car is Positive ground.  Battery compartment is under the driver's floorboard.

[kclark]

8 hours ago, mike6024 said:

 

 

 

There are marine battery swwitches, 1, both, 2 or off

 

https://www.westmarine.com/buy/blue-sea-systems--e-series-compact-battery-switch-off-1-both-2-no-alt-field-disc--3831393?

 

I think you use "both" when you know you are in a charging situation. When discharging just use one or the other so you keep one in reserve.

 

 

 

 

 

I looked at those earlier today. I assume that you use 1 or 2 for ordinary driving. Then use 1+2 for night driving or cold morning starts? If I decide to add this, does NAPA make battery cables?

[mike6024]

 

I'm not implying I recommend this thing, it just seems you may be able to use it if you want. It requires nothing special battery cable wise. It would need a double-eye cable for connecting the output to the starter. Or you could buy marine cable, or other cable and crimp your own ends on. Double-eye cable-

 

https://www.napaonline.com/en/p/MPB781115

 

 

 

So you tie the grounds together and ground them. You have positive ground? Assuming so, then one negative battery terminal gets connected to input #1 with conventional battery cable. Other battery negative terminal gets connected to input #2 with another conventional battery cable. Then output gets connected to the starter with a double-eye.

 

Edited November 23, 2017 by mike6024 (see edit history)

[Matt Harwood]

Just make sure you're using heavy cables, not the pre-made 12-volt cables they sell at the auto parts store. Most electrical problems on 6-volt cars can be traced back to inadequately sized battery cables and bad grounds. There are shops that will make you heavy battery cables (0 or 00 gauge) to whatever length you need and whatever ends you want. I don't like the look of that switch for 6-volts (half the voltage means twice the current) and still think that you should analyze the problem and try other solutions before throwing more batteries at the problem. You still haven't clearly identified what your problem is--is the car simply discharging a bit with the lights on, is it running out of electricity and dying while you drive at night, or is it sputtering because there's not electricity to fire the plugs? Three different problems with three different solutions, only one of which is "more battery."

 

We can help better if we understand the problem better. It sounds like you're just concerned that your battery is showing a discharge at night when you're driving in parades. I'd say that's not an issue unless that's all you do with the car.

[kclark]

1 hour ago, Matt Harwood said:

Just make sure you're using heavy cables, not the pre-made 12-volt cables they sell at the auto parts store. Most electrical problems on 6-volt cars can be traced back to inadequately sized battery cables and bad grounds. There are shops that will make you heavy battery cables (0 or 00 gauge) to whatever length you need and whatever ends you want. I don't like the look of that switch for 6-volts (half the voltage means twice the current) and still think that you should analyze the problem and try other solutions before throwing more batteries at the problem. You still haven't clearly identified what your problem is--is the car simply discharging a bit with the lights on, is it running out of electricity and dying while you drive at night, or is it sputtering because there's not electricity to fire the plugs? Three different problems with three different solutions, only one of which is "more battery."

 

We can help better if we understand the problem better. It sounds like you're just concerned that your battery is showing a discharge at night when you're driving in parades. I'd say that's not an issue unless that's all you do with the car.

 

 

I have checked my cables, all is good there (at least I don't see anything out of sorts). What I have been experiencing is the car seems to be discharging with the lights on. If I turn the car off after stopping on the way back to the shop at night, it grunts to start back up. and it will drive a little ways and loose power after sputtering. 

[Grimy]

At, say, 1500 rpm with headlights on, your 3rd brush is properly adjusted if you show a very slight charge.  It is within the original design parameters if you show a discharge with lights on at 1000 rpm or less--that's the way it was before alternators.

 

If night driving at low rpm in parades is something you'll be doing more than very occasionally, perhaps you should get your generator converted to an alternator--if such is even feasible, because your generator may be driven by the chain and driving the water pump and/or distributor.

 

From what you've told us, if the car were mine I'd run one Optima and carry another fully charged one to change out at the end of the event before the drive home.  Optimas are one-hand installation and all you need is a 1/2-9/16 combination wrench.

Edited November 24, 2017 by Grimy
correct typo (see edit history)

[kclark]

On 11/23/2017 at 9:27 PM, Grimy said:

From what you've told us, if the car were mine I'd run one Optima and carry another fully charged one to change out at the end of the event before the drive home.  Optimas are one-hand installation and all you need is a 1/2-9/16 combination wrench.

 

I haven't decided whether to install the switch or not but wouldn't that aid in the quoted scenario? install both batteries and then just turn the switch from 1 to the other without a wrench.

[Grimy]

1 hour ago, kclark said:

I haven't decided whether to install the switch or not but wouldn't that aid in the quoted scenario? install both batteries and then just turn the switch from 1 to the other without a wrench.

Yes, but be sure to use 0 (aught) or better 00 (double aught) cables for all connections.  Do you have space in your battery box for two Optimas, or can you modify the box?  For me, how much I'd need it, plus the available space, would be the decision elements.

[mike6024]

Can regulators be retrofit to unregulated generator systems?

[Grimy]

By the way, buried in the fine print in Optima instructions is a caution to NOT use a battery lift strap on them.  You should be able to pick up with one hand. For under seat / under floor installations, the no water and no corrosion aspects of Optimas are significant advantages. 

[Grimy]

5 minutes ago, mike6024 said:

Can regulators be retrofit to unregulated generator systems?

Probably can, Mike, but we are limited by 25 amp max output of those generators, and when the temperature compensator (de facto regulator) kicks in, a 25A generator will be producing only about 17A.  I'd be interested in knowing the generator number, which MAY for this application (hearse) be the optional higher output generator, but still only 30A with the third brush turned all the way up.

[Bloo]

1 hour ago, mike6024 said:

Can regulators be retrofit to unregulated generator systems?

 

Yes and no. Adding voltage regulation to a completely unregulated system is possible. @ply33 right here on the forum has done it. Maybe he will stop in here. I don't think the unit he used is still available. Someone probably makes one.

 

http://www.ply33.com/Repair/voltreg

 

Adding current regulation gets a bit more complicated.

 

Edited November 25, 2017 by Bloo (see edit history)

[keninman]

One thing that I did was replace all of my bulbs except the headlights with LED. Even the 3 dash, 1 tail and brake all use some current. It really reduced the load on the generator. I also put LED bulbs in the parking lamps, these would be quite bright enough for a parade I would think and draw nearly nothing. I have left mine the bright white for now but I do have a spray coating I can apply that will give them a more amber appearance like an incandescent if I decide to. 

[kclark]

I received 2 optima batteries and installed one. What a difference. My battery is registering around 9 on the ammeter. I see that now. My old one which was a new battery from AutoZone registered right at 3. I really didn't pay any attention to the meter readings until today. 

[Matt Harwood]

That's still odd. The ammeter measures the movement of current through the system, either from the generator into the battery or from the battery to things like the headlights. If it went from +3 amps to +9 amps just by changing the battery, that seems odd. The ammeter does not measure the condition of the battery itself.

 

Keep an eye on what the ammeter says while you drive, at idle, and with lights on and lights off. It should show its highest reading at speed with everything off and that's as much charge as you'll ever get. It will show a negative reading at idle with lights on, and that's normal, as long as it moves back to the positive side when you accelerate to speed. Keep an eye on it and tell us what you see.

[Stude Light]

I purchased an electronic voltage regulator that fits under the band of my generator. It replaces the third brush and can be used with or without a cutout relay. It really works well. I get the correct amperage when needed. Of course you are still constrained to the maximum current your generator is capable of but you get the full output when needed and little to no output when you don't need it. Fully concealed under the band.

 

Bought it from:

James Peterson

P.O. Box 884

Bend, Oregon 97709

 

jpetersonbend@yahoo.com

 

EDIT:   I just noticed that Bloo already posted this info in a link from ply33.  So take this as a testimonial that it is a great solution. This is what the regulator looks like:

 

Jim is still selling these.

Edited November 26, 2017 by Stude Light
update (see edit history)

[Marty Roth]

I use a pair of 6-Volt Optima batteries in Parallel on my 1941 Cadillac.

The reserve amperage is awesome.

I also use Triple-Aught (000) cables with the ends soldered.

The result is fast cranking, no diminished capacity.

 

The idea of using a Marine Switch is certainly a decent idea, but requires much longer cable runs.

[Bloo]

47 minutes ago, Marty Roth said:

 

The idea of using a Marine Switch is certainly a decent idea, but requires much longer cable runs.

 

Worse, it adds more connections to the system. Worst of all it adds a switch.

 

I know some of us NEED a switch to shut things off when not in use, but battery switches are slightly less reliable than dashboard clocks.

[Spinneyhill]

When my car is not in use, the battery cable is disconnected at the starter. It has a wing nut on it for this purpose. A short piece of hose is shoved on the terminal end to make sure there is no short possible. It is easy to change to the proper nut if I wanted to show the car.