Question regarding charging a 6 volt battery...

[Dodge55Royal]

My '55 Dodge has a 6 volt positive ground electrical system-the last year for MoPar products. I wanted to charge the battery because it doesn't sound like it's fully charged when I start it. When hooking up the charger do I put the red cable on the positive side of the battery just like it was a 12 volt system? Also, is it true that the generator doesn't keep the battery fully charged like an alternator does? Thanks...

 

PS............I took it to an AACA car show on Labor Day in Louisville and met a lot of nice people and had a good time....

 

 

[TerryB]

Yes, red to + and black to -.  The typical generator doesn’t do as good a job of charging at low rpms like idling however the one wire alternator doesn’t either from what I read about them.

[JACK M]

The one wire alternators will charge at idle, but one needs to rev the engine a bit to excite the rectifier. Then it will charge at idle,

The car will run off of the battery until the rectifier gets excited. A good goosing will do it in most cases.

I usually wait for a minute or three so as not to be revving a flat cold engine.

[Dodgeman]

If your car is cranking slowly check the battery cables. Too small of a cable will cause slow cranking. Check and clean all connections also. Your generator will charge the battery just fine. It just doesn’t charge at idle. While driving look at your amps gauge. If it’s not swinging to the charging side then your battery is charged. Hooking it up to a charger won’t hurt. Then you know it’s fully charged.

[Pfeil]

One step at a time. First charge the battery fully, then do a load test. If the battery passes the load test and the car still has cranking problems, then we look for resistance in the wiring and in the starter. We also check resistance in the engine. What I mean by that is a friend with a 37 Ford had a cranking problem every time his car got up to operating temp. He tried new battery, then a 6/12 battery and nothing would turn it over. After a couple of years of disgust, I found the woody in my back yard one day with a frustrated friend and said, "please do whatever it takes before I push it over a cliff or something". What I found was the rebuilder of the engine clearanced the block for cast iron pistons and used aluminum pistons. The engine would lock up or become very tight when warmed to operating temp.

 

Most generator equipped cars will show a discharge at Idle. That is NORMAL. If you want to make a generator charge at Idle and you don't do a lot of driving or high-speed driving, you can change the pulley size diameter to accommodate this problem you THINK you have.

 

[Dr B]

1 hour ago, Dodgeman said:

Check and clean all connections

I have found that a bad or poor battery ground has been the culprit on more than one occasion.  Make sure you have a good ground for your battery (or even a second ground).

 

Robert

[60FlatTop]

I had a 1935 Nash that was positive ground. One spring the battery was completely dead and I hooked up the charger backwards, no spark, no juice. The car started right up after an overnight charging.

Then I noticed my ammeter moving backwards. I asked an electrical engineer friend if I could have reversed the battery polarity. He said it would be very hard to do but if anyone could it would be me. Per his instruction I took the battery back to the original condition, completely dead. I put an old firewall mounted heater fan across the terminals and drained it for a few days. Then I was able to recharge it correctly and things worked fine.

 

Just in case someone mixes things up.

[TTR]

15 minutes ago, Pfeil said:

One step at a time. First charge the battery fully, then do a load test. If the battery passes the load test and the car still has cranking problems, then we look for resistance in the wiring and in the starter.

This ^^

16 minutes ago, Pfeil said:

 

Most generator equipped cars will show a discharge at Idle. That is NORMAL. If you want to make a generator charge at Idle and you don't do a lot of driving or high-speed driving, you can change the pulley size diameter to accommodate this problem you THINK you have.

You can also make adjustments to some voltage regulators to increase output at idle, but this requires basic understanding of how automotive charging/electrical systems work and how to perform any such adjustments.

 

[Dodge55Royal]

Thanks for the comments. The battery has a sticker on it which says "H-18"which probably stands for August 2018 so the car is probably ready for a new one. I'll find out this winter when I try to start it when the temperature is below freezing. Thanks again....

 

 

[Paul Dobbin]

Nice old Dodge, don't wait until winter to drive and enjoy it..   i suggest planning a Leaf Peeping Tour for next month and i

invite anybody with an old car to join you.    There is some safety in numbers, especially when somebody has jumper cables.

[Marty Roth]

26 minutes ago, Dodge55Royal said:

Thanks for the comments. The battery has a sticker on it which says "H-18"which probably stands for August 2018 so the car is probably ready for a new one. I'll find out this winter when I try to start it when the temperature is below freezing. Thanks again....

 

 

What you consider 
Slow" cranking may actually be correct for a 6-Volt system. They generally do not spin as fast as a 12-Volt system.

Don't just" ASSUME" because it could still be OK.

Listen to other 6-Volt MoPar products, or any other brand still on the 6-Volt battery before you give up on a perfectly usable battery-

But definitely check to be sure there is no paint or corrosion at either end of any of your cables-

and Absolutely be sure your cables are NOT MODERN 12-Volt skinny cables !

Many of us still on 6-Volt, have cables made of Aught or Double and even triple Aught (0, 00, 000) gauge cables with preferably soldered terminals for real conductivity.

It really makes a difference.

 

Good luck with the lovely Dodge.

[human-potato_hybrid]

After the battery has had some time to rest after a drive or charge (several hours), simply check the voltage with a meter to determine the level of charge from voltage. Obviously it should be at half this scale.

 

If it still cranks too slow when it's at full charge, then get a new battery cable. Clean your connections before installing it. You need a 0 or 00 size (00 is larger).

 

Remember that these old cars naturally crank slower than new cars, so your point of comparison should be cars of a similar era, or if it won't crank fast enough to fire off.

 

Edited September 10 by human-potato_hybrid (see edit history)

[Bloo]

Older engines just turned slower when running. Their cam profiles were suited to the RPM they turned, and as such they had good compression at a lower RPM than a modern engine typically would. The starting RPM was also lower. It is kind of set by the starter motor design and the number of teeth on the ring gear vs the number of teeth on the starter drive. In the 50s, it hadn't been that many years since we were starting them with cranks. That said, there is a big difference between a starter sounding slow to modern ears as most 6V starters do, and one that chugs to a stop every time another cylinder comes around. Others mentioned the cables. They matter.

 

8 hours ago, Dodge55Royal said:

is it true that the generator doesn't keep the battery fully charged like an alternator does?

On most cars 1940 or later, the generator is big enough to do it's job without straining too much. In the generator days, it was a thing to check the battery with a hydrometer and set the voltage (or current on cars with really archaic generators) so that the battery is staying full with the driver who drives the car driving it. After 1940 or so American generator systems were mostly higher capacity systems with 3 relay regulators, and in practice they behave exactly like alternators with one difference. Instead of less charge at idle you typically get no charge. Does it matter? In the real world, for most of the population, no.

 

In the 1950s, the charge rate probably still got turned up a couple of tenths of a volt or even more for some people. If you were commuting up old 99 in Seattle to Boeing's graveyard shift in the pouring rain every night, with the lights, heater, and wipers on, stopping at every stoplight, you probably had different needs than someone driving across rural Nebraska in the daytime regularly. Under extreme conditions, no charge at idle can matter. I have daily driven a bunch of cars with generators though, and the factory setting has always worked for me so far. I have never yet noticed any difference in charge level compared to an alternator in daily use.

 

If you aren't daily driving it though, put a "battery maintainer" on when you aren't using the car. It makes a night and day difference from the way things used to be when maintainers didn't yet exist. That's good advice on any car, 6 or 12 volt, generator or alternator. For what it's worth, it seems easier to completely kill a 6v battery than a 12v one if it is allowed to go dead.

 

Edited September 11 by Bloo (see edit history)

[human-potato_hybrid]

One thing people don't really get is that the car itself barely takes any power to run, compared to running the accessories like headlights and blower fans. Obviously excepting starting the motor.

 

But if the car starts easily and you aren't running any accessories, the car should run for HOURS with NO charging. That's why no charge at idle doesn't matter in a generator charging system, except in high idle duty, high accessory draw driving. Example: taxis, which used a smaller generator pulley to charge at idle; the cars never drove fast enough to exceed the roughly 10k generator RPM max typical speed.

[Dodge55Royal]

4 hours ago, Paul Dobbin said:

Nice old Dodge, don't wait until winter to drive and enjoy it..   i suggest planning a Leaf Peeping Tour for next month and i

invite anybody with an old car to join you.    There is some safety in numbers, especially when somebody has jumper cables.

 

It's been my daily driver since May when I bought it. I will drive it all winter too unless there is snow or salt on the roads which doesn't happen in Louisville very often. (We only got 2" of snow last winter.)

 

The car has big, thick battery cables on it which were installed two years ago when the previous owner bought it from an old lady after it had been sitting in her garage for 15-20 years. He also had the entire brake system replaced, tuned up the engine, rebuilt the carb, replaced the belts, hoses and tires. Thanks again for all the helpful comments....

[Paul Dobbin]

That's a cool story, congratulations and welcome to the AACA Forums.    Louisville has to have a AACA Chapter or Region

and those folks love to drive their cars too and would love a new guy to lead them for a drive in the country.   When I moved to

NC from Florida, I offered to lead some rides in the country to the local old car folks.   They love it and I've now done almost

60 of those rides.   (You can lay out a tour ahead of time in about one hour)

You don't  need a fancy tour,   you can do a simple "Follow the Leader" ride.   (We do it in age order of the cars, so that we don't

drive off and leave them.    The car behind me sets the pace and everybody is responsible to watch the car behind them, to make

sure we don't loose anybody.   ( I tell them all "to make sure the car behind you sees you turn")

On bigger rides of a hour or more I type up some route directions, which include local history of things and places we pass and

always find a place to end where we we can get refreshments and talk old cars

You'll find that participation breeds friendships and a wealth of old car knowledge.    

Good Luck

P. S.   I went to Louisville for the NSRA Show and Rod Run in 2002 and took a antique car to their free 23 point Safety Inspection, and passed with flying colors.   I also found the Street Rodders to be a very friendly bunch.

 

Edited September 11 by Paul Dobbin
deleted duplicate text (see edit history)

[ABear]

17 hours ago, human-potato_hybrid said:

After the battery has had some time to rest after a drive or charge (several hours), simply check the voltage with a meter to determine the level of charge from voltage. Obviously it should be at half this scale.

 

If it still cranks too slow when it's at full charge, then get a new battery cable. Clean your connections before installing it. You need a 0 or 00 size (00 is larger).

 

Remember that these old cars naturally crank slower than new cars, so your point of comparison should be cars of a similar era, or if it won't crank fast enough to fire off.

 

Actually, using the voltage is notoriously inaccurate at best, as the chart you have posted is not 100% accurate either.

 

You can find hundreds or even thousands of voltage charts and not one of them will agree. There is a lot of variability that affects the actual battery voltage reading, temperature, meter quality and calibration, how clean the terminals are, electrolyte and battery construction all have some affect on the battery voltage.

 

Generally it is well accepted that a fully charged 12V FLA battery should have a resting voltage of no less than 12.6V up to 12.8V

 

That would be 6.3V up to 6.4V for a 6V battery.

 

Generally it is accepted that a 12V FLA battery fully discharged battery voltage will range from 10.5V to 11.0V

 

That would be 5.25V to 5.5V for a 6V battery.

 

Here is a website that has charts a little closer to reality..

 

https://learnmetrics.com/lead-acid-battery-voltage-chart-for-6v-12v-24v-48v-batteries/

 

Checking via hydrometer with temperature corrected chart is the most accurate way to check state of charge and condition but not all batteries have removable caps.

[Dodge55Royal]

2 hours ago, Paul Dobbin said:

 Louisville has to have a AACA Chapter 

 

These guys must have a lot of money because they bought an entire church on about a 3 acre lot in a nice part of town. They removed all the pews and put in a lot of tables and chairs. It has a big basement with a kitchen where they sold food. The proceeds go to the WHAS Crusade for Children which you can read about below. It's a really great group of caring people....

 

https://www.whascrusade.org/whas-crusade-for-children-history/

[human-potato_hybrid]

@ABear not saying it's 100% accurate, but should be good enough. By the way, if your terminals are dirty enough to throw off your voltage reading, that's a problem in and of itself, since any resistance apparent across a 10MΩ meter will greatly affect a starting circuit of roughly 0.05Ω impedance...

 

Likewise if your meter can't tell the difference between 5.9V and 6.3V then it's garbage. 

[Paul Dobbin]

The AACA is the Antique Automobile Club of America, that I was referring to.   Is the Crusade one of their activities?

A AACA Chapter or Region of the Antique Car Club of America is the group I was trying to get you involved in.

[Lee H]

19 hours ago, Bloo said:

Older engines just turned slower when running. Their cam profiles were suited to the RPM they turned, and as such they had good compression at a lower RPM than a modern engine typically would. The starting RPM was also lower. It is kind of set by the starter motor design and the number of teeth on the ring gear vs the number of teeth on the starter drive. In the 50s, it hadn't been that many years since we were starting them with cranks. That said, there is a big difference between a starter sounding slow to modern ears as most 6V starters do, and one that chugs to a stop every time another cylinder comes around. Others mentioned the cables. They matter.

 

On most cars 1940 or later, the generator is big enough to do it's job without straining too much. In the generator days, it was a thing to check the battery with a hydrometer and set the voltage (or current on cars with really archaic generators) so that the battery is staying full with the driver who drives the car driving it. After 1940 or so American generator systems were mostly higher capacity systems with 3 relay regulators, and in practice they behave exactly like alternators with one difference. Instead of less charge at idle you typically get no charge. Does it matter? In the real world, for most of the population, no.

 

In the 1950s, the charge rate probably still got turned up a couple of tenths of a volt or even more for some people. If you were commuting up old 99 in Seattle to Boeing's graveyard shift in the pouring rain every night, with the lights, heater, and wipers on, stopping at every stoplight, you probably had different needs than someone driving across rural Nebraska in the daytime regularly. Under extreme conditions, no charge at idle can matter. I have daily driven a bunch of cars with generators though, and the factory setting has always worked for me so far. I have never yet noticed any difference in charge level compared to an alternator in daily use.

 

If you aren't daily driving it though, put a "battery maintainer" on when you aren't using the car. It makes a night and day difference from the way things used to be when maintainers didn't yet exist. That's good advice on any car, 6 or 12 volt, generator or alternator. For what it's worth, it seems easier to completely kill a 6v battery than a 12v one if it is allowed to go dead.

 

Just for fun, I did a quick cranking speed comparison of 1952 models (all with 6V systems) to 1957 models (all 12V, I believe). The average speed increase is roughly 50%. I know there are other differences in cam design, compression, etc. over those 5 years, but I think it’s still informative.

 

 

[zeke01]

1 hour ago, Paul Dobbin said:

The AACA is the Antique Automobile Club of America, that I was referring to.   Is the Crusade one of their activities?

A AACA Chapter or Region of the Antique Car Club of America is the group I was trying to get you involved in.

The local AACA region in Louisville is the KYANA region. It is very large with a waiting list of applicants. It would be easy to believe that they support the Crusade for Children. It is also very large organization. Zeke

[human-potato_hybrid]

22 minutes ago, Lee H said:

Just for fun, I did a quick cranking speed comparison of 1952 models (all with 6V systems) to 1957 models (all 12V, I believe). The average speed increase is roughly 50%. I know there are other differences in cam design, compression, etc. over those 5 years, but I think it’s still informative.

 

 

Interesting. It's easier to build a more powerful starter that runs on a higher voltage compared to lower, as you get more magnetic effect for the same cross section of wire. In other words, you need larger wire for the same amount of current when you have less voltage, which ultimately forces a limit on the magnetic flux density.

[John348]

On 9/10/2024 at 2:01 PM, TTR said:

This ^^

You can also make adjustments to some voltage regulators to increase output at idle, but this requires basic understanding of how automotive charging/electrical systems work and how to perform any such adjustments.

 

You can, but I think one's knowledge would be have to be a little more than basic. For action there is a reaction. My father was determined to this back in the 80's with a 50 Chevy he had, while it worked at idle as he hoped it over charged the battery at high speeds and started to boil over batteries, so his cure was to drive with the headlights on during the day to put a load on the generator, that seemed to work, as long as he remembered to shut them off when he was idling at a light in traffic. I remember the Oldtimers in the Region (at the time) told him he was asking for trouble, everything was set up at the factory, but he was stubborn and a thought good understanding of electricity. The Autolite 6-volt regulators that I have seen are adjustable if you have a spare regulator, maybe give it a try. As an electrician I presume people have some knowledge of electricity. but I had discovered most have none and admit which is good

Or just put in neutral and give it light throttle, my father was not too happy with me years after he sold the car, and I asked him wouldn't had been easier if he just did that   

[Bloo]

The low/no output at idle is not really something the regulator has control over. The generator either generates enough to pull in the cutout relay or it doesn't. If the generator is charging but not keeping up, the voltage regulator points are closed and the field is as "on" as it can possibly be.

 

I see no real way to improve this other than spinning the generator faster. Spin it too fast and inertial forces will destroy the armature. Alternators, by comparison, can work over a wider RPM range because they spin the field instead of the charging windings, and as such the rotor assembly can take more stress. Both generators and alternators on antique cars spin faster than the crankshaft in practice, so the crankshaft RPM is multiplied by the pulley ratio. The generator already has a larger RPM range to deal with than the engine, and that's before you start changing pulleys. It only gets worse when you do. I suspect there was some headroom in the 30s. Buick did spin the generator a little faster as part of a scheme to flatten out the output of their "3rd brush generator plus voltage regulator" systems around 1937-38.

 

The Buick Eight was a low speed engine though. With most OHV V8s of the 50s, the crankshaft RPM range is wider, and I suspect the generator drive ratio is already about what it needs to be to start charging reasonably soon and still not do harm to the generator at high speed or during passing. You'd need the actual numbers to know for sure.

 

 

[human-potato_hybrid]

Remember also that generators are self-exciting. The more voltage that the arm produces, the greater the magnetic field generated by the field coils. So while generator output voltage would be proportional to engine speed if the field coils were powered by the battery, the relationship is actually much more complex so you end up with the generator not doing much up through several hundred generator RPM then pretty suddenly it is at full output voltage. 

Edited September 12 by human-potato_hybrid (see edit history)

[Dodge55Royal]

8 hours ago, Paul Dobbin said:

The AACA is the Antique Automobile Club of America

 

Thank you for explaining that to me. Even though I have owned dozens of classic cars over the years I always thought AACA stood for Alcoholics Always Consume Alcohol. I'll make sure to mention that to everyone at my next Mensa meeting. LOL....