Charging voltages...

GBsPanhead

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OK, it's late. Can get pics of gauges in morning if necessary. Will try to explain as best as possible.

Stock '69 300 convertible for the most part. Installed new battery as was unsure of condition of the old battery. The following issues were seen before battery swap. But that's not why I swapped battery. Just want peace of mind with new battery.

OK, here we go. Start car, AMP gauge shows charging, new SW volt gauge shows around 14ish volts at idle. Press brake pedal, volts drop to 13ish, turn on headlights, volts drop to 12ish...all at idle. AMP gauge showing discharge. Give a little gas to raise RPM's...volts go up slighty to maybe just under 13. Go back down to idle....12ish. Let go of brake pedal, volts go up a little, turn off headlights..volts back up to 14ish. Turn signals cause volts to drop alittle. Volts change maybe 1.5 volts as signals go on/off/on etc. Driving around during day...no issues with volts/charging. But as soon as headlights go on, I'm concerned too much 'cruising' and not at higher RPMs will cause my battery to discharge.

I'm researching on here, just curious of causes, or is this normal? Thanks!!
 
Had those same issues. Rewired alternator and all the power wires with thicker GA high quality wire and also bypassed the ammeter. I do see a substential drop when my -electric- fan comes on but usually my volatges hover just above 13v with loads applied
 
It's quite normal for the non-electronic voltage regulator cars to display what you describe. At night, or with the a/c on also, the needle drops just to the negative side of charge at idle. The headlights might dim a very slight amount, at stop signs and such, but once in motion again, no problems. It's all temporary and just part of the way they were back then. I always thought it unusual that GMs did not display similar these same actions, but I trusted the Chrysler guys to do it right. Sooo, as long as it doesn't get any worse at idle at night, then no real issues.

Of course, you could add a larger capacity alternator to put out a bit more amps at idle. Make sure ALL charging system terminals are CLEAN, too. As I saw with my own eyes, a modern 140amp OEM system can lose about 10% of total charge performance with must a bit of grumge on the battery terminals (even a side-terminal battery of good condition).

Follow that 10ga red wire through the bulkhead connector, which is another area that is forgotten but can have terminals which have accumulated a bit of grunge on them.

I know that some have re-wired for other electrical paths, but my own experiences and observations from seeing the state patrol cars at the local dealership back then, the issues which some have mentioned in here were not seen by myself, or heard about at the dealership, seemingly weren't needed in TX, for some reason. Even when the cars were newer. Be that as it may. It was about keeping things stock and OEM warrantiable. Be that as it may.

When GM put voltmeters in their 701/2 Camaro/Firebirds, it was "counter culture" of sorts, but they claimed it was a better indicator of charging system condition. Took some getting used to, but they stuck with it and still put in voltmeters. Now computer-controlled differently than in the past, which show higher voltages that then decrease to just over 12v, all within the "normal range" on the gauge.

CBODY67
 
IMHO, what you are experiencing is normal. The solid state voltage regulators (which I sell) will help some but you need to keep in mind that the factory alternator output in a non-A/C car was around 37 amps. This is one reason that the cars use big batteries so that when you are stopped for a long traffic light at night the battery has enough reserve capacity to be discharged some but it will charge right back up when you start to move. When the battery is fully charged it should be at 13.8 volts so if you are getting 14 volts on your voltmeter at idle 5 minutes or so after you start the car you are getting the correct voltage. Some of us have learned to put the car in neutral at a long light at night to increase the engine RPM a little bit, which in turn ups the voltage output. I would always have the car running when lowering or raising the top due to the draw that the top motor takes. I don't think you need to worry but if you aren't comfortable, upgrade to a 45 or 50 amp battery and a solid state electronic (vs. mechanical) voltage regulator and you will be fine. As noted above, inspect and clean all of the wiring connections and look for melted or cracked wires in the charging circuit.
 
Basically normal. It won’t hurt a good battery. Everyone freaks out Over this. Back to basics, you don’t test alternator outputs and voltages at idle on1960’s cars. You raise to 1200 or higher to test and condemn parts and pieces. And don’t toss a 100 amp alternator on old wiring, it will cause more problems.

Yes check connections and th basics, but you describe a normal,function of a. Stock mopar charging system. These charging “problems” were no problem when the car was new.

Your new jap car charges fine at idle, but your mopar is no jap car, it’s works different, accept it.
 
Seems like the "police" alternator was 60amps, back then? The 100amp alternators didn't happen until about 1974 or '75, in conjunction with the first electric defrost back glass option on C-bodies and RWSX cars. FWIW

CBODY67
 
Thanks everyone for all the feedback! Glad to see that what I'm seeing is normal, and from extra research I did last night, I see there are some 'fixes' if I want.

When I replaced the old battery, I did see that someone had installed a smaller battery. I had plenty of room , so went with a bigger group size. I haven't had any issues, but wanted to make sure what I was seeing is normal. I don't want to be out late at night and have issues, if I can avoid it.
 
Some of the later "smaller" batteries can have more CCA in them than some of the older larger batteries. I always put the optional Group 27 batteries in my cars. That's what the battery tray is built for. Group 24 was standard.

Enjoy!
CBODY67
 
I run one of the solid state regulators sold by the gentleman above on a 60A alternator system with a HUGE battery which I had to modify the carrier pan to accommodate, yet I still have the same normal fluctuations you experience at the same delta Vs. So long as you use the original Mopar charging system for the C-body period, you will get some delta V dependent on your engine's angular speed (rpms). I drove a 66 NYer in 2004-05 equipped with a 100A alternator (MONSTROUSLY HEAVY!) with an old school solid state ignition on a 440 and this too fluctuated, too much as it turned out.

Mopar first installed alternators on their vehicles, ahead of GM and Ford, felt smug about it for 20 years and while I LIKE the old school setup, I admit it could have been improved a little sooner than it was.....

Be this as it may, for flexibility and non-automotive hack applications, the old round or square back alternators both can be easily converted to 3 phase power plants at ~ 60 Hz, by finding the correct pulley or shaft coupler, and a good 4 stroke small engine and ditching the rectifier setup. You will need to still regulate the field of course and then get 3 small transformers. I recommend variacs made for the 80VAC-277VAC range there.....

Old School is COOL SCHOOL!
 
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