Positive ground 6 volt charging system

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53_mercLuke

Member
I'm curious, what is a 6 volt charging system suppose to be putting out? I'm getting a reading of 6.75 volts at idle and reved up alittle it gets to about 6.94 volts. I try and start my car, 1953 Mercury with the Flathead, at least once a week but every time the battery is dead for some reason. I took apart and cleaned the generator and put new bushings and bearings in it and the battery and regulator are a couple months old from napa. When I unhook the battery when the car is running it stays running so that tells me the generator is doing something, but I feel like the charging system should be putting out more voltage. Not sure if I have another issue somewhere or if something is going wrong in the charging system. Thanks for any help and ideas
 
Your way low aim for 7.1-7.4V.
Keeping a battery not fully charged get the acid more aggresive on the lead and shortens the life of it.
At 1.28 density of acid your fully charged and resistance is lowest giving best cranking powwer at 1.08 the acid eats the lead up.
 
If the battery is loosing power between weekly startups you most likely have a short somewhere. Unhook one of the terminals of the battery between starts and see if the battery will hold a charge.
 
I've been running well since 2009. changed my battery August 2015. Last year during summer The Batt would go down after a couple weeks. Finally tested it in September and one cell was low. No warrantee more than 6 Months on the battery.
 
Luke, to test your generator voltage output setting, connect your voltmeter to the "A" or "B" terminal on the voltage regulator and with a warmed up engine rev to about 2000 rpm and hold for a couple of minutes and voltage should be reading at 7.5 volts. If battery is not fully charged then reading may be a little lower say 7.2 volts or so. I like to set them at 7.6 volts with engine, generator/voltage regulator up to operating temperature. Regards, Kevin.
 
I totally agree with all the above about getting your charging rate properly set. Before doing that, get the battery thoroughly tested and charged.

However, "Tinker" raises an important concern. Even if your generator is charging at a rate under spec, and you only run the engine once per week, it seems unusual to me that the "good" battery goes completely dead every week. I recommend checking the obvious .... simply be sure there's no short (leak) in your electrical system by temporarily connecting a test lead containing a volt meter between the neg batt terminal and the starter solenoid when the car is totally shut down. Won't hurt to be sure.
 
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Whether 6v, 8v, 12v, or 24v, a lead acid battery behaves by chemical rules. Rather than memorize the parameters for a singe cell, or for 3 cells, it is most practical to know the numbers for a 12v (6 cell) modern car battery at room temperature as this is most common battery for all of us.

A fully charged 12v battery exhibits 12.6v when disconnected. An exhausted or in-use 12v lead acid car battery should be charged at 14.5v ± 0.2v.

Half the voltages for a 6v battery. AND know that cheap voltmeters don't read exactly right but are close enough for government work. Gell cell chemistry such as Optima Redtops are par, BlueTop and YellowTop voltages a tiny bit higher but not enough to loose sleep over.

So next time you suspect your modern daily driver has a bad alternator, you know what the battery should read and you also know whether to replace your battery if it fails to achieve that voltage after a few hours of full voltage charging. Memorize those two voltages and your battery will love you.
 
If a battery is going dead in about a week of none use there is drainage somewhere in the system and/or the battery is bad. I had this kind of a problem with a '57 Bird I had for many years, the problem drove me and a couple of my mechanics nuts. I finally put a battery disconnect on negative side of the battery, solved the problem temporally. However, if I forgot to turn the disconnect off for a couple of days, the battery would be dead.
A volt meter between the negative cable and the battery would show a small draw when the ignition was off. Because of the complexity of the many circuits in the car, power windows/seats, heater, backup/stop/turn lights, etc., disconnecting circuits proved to be a daunting task. Finally resorted to R/R,ing components, to no avail.
Long story short, the problem turned out to be a horn relay..
The horn relay is one of the circuits that is hot all the time, the power is controlled via the ground..
 
So I took my generator down to the battery and electrical shop to have them test it just to make sure I wasn't doing it wrong. The guy said it was putting out 40 amps and everything looked like it was working. I asked him about my hook ups just to make sure I had them hooked up right since I don't have the greatest wiring diagram but according to him I had it right. He told me to check the points on the voltage regulator so I just got home and checked them. They look clean, it's a brand new one, but when I start the car to see if they open and close while running, they just sit there. The only time I have any spark is when I have a jump wire straight from the battery to the battery post on the regulator and I push down on the point to make contact. So does this mean my regulator is bad?
 
The cutout relay should close when you start and rev up the engine a bit.
If it doesn´t close neither voltage or current regulator will do anything.
Why not bring the regulator for testing while at it ??
 
Might be better off having the charging system tested as a whole. Most auto parts places will test them for you, just be sure they understand it's positive ground 6v system. Can the electrical shop you used check it on the car?
 
Polarizing sets up not only the polarity but it charges the field pole shoes with a bit of residual magnetism. The residual is what gives the gen the capability to close the cut out points and bring the system on line.

The voltage regulator points open and close so fast, you may not be able to tell they are moving. The current limiter just keeps the current in line while in operation.
 
If the battery is not fully charged, or bad the charging voltage can be low with nothing wrong with the charging system----

try charging the battery and letting it sit unhooked---if it goes dead then the battery is bad
 
Luke, It would be advisable to take both your generator and voltage regulator to the Auto electrical shop and have them run them up in their test bench. They should be able to adjust your new regulator to the correct specs. Better still, take the car down there if you can. New voltage regulators are not necessarily adjusted correctly. Don't alter or mess with the regulator if you don't understand how and why it works because you may do damage to it. There are very specific adjustments on each of the three units inside the regulator which have to be very correct for your charging system to work correctly. Regards, Kevin.
 
B-O-B said:
Did you polarize the system after you had the generator off & put it back on?
Click to expand...

If you take the generator off, and put the same generator back on, doing nothing else, you do not have to repolarize the system. Put a new generator on, yes, repolarize.
 
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