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Dan2973
Samba Member
Joined: April 12, 2019
Posts: 436
Location: NJ
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 Posted: Sat May 15, 2021 1:34 pm Post subject: Re: Another voltage regulator ? |
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| EVfun wrote: |
| Dan2973 wrote: |
| EVfun wrote: |
| Dan2973 wrote: |
| EVfun wrote: |
Starting batteries die fastest from deep cycling and from spending to much time at a low state of charge. Overcharging can kill them but takes longer. They die in 5 to 10 years even when treated well. Charging and discharging slowly damage the plates.
I would measure the voltage of your new battery before installing it. Then install the battery and start the car. Right after starting, with the fast cold idle still on and no accessories on, measure the voltage between the regulator output and the engine case. Now run around quickly and measure the voltage between the battery posts. Both should be within a few hundredths of a volt of each other and higher than your reading of the battery before installing. |
I guess I’m ordering another optima 6v. 200 bucks. I’m just wondering could the very loose trans ground strap have caused this all along? I was always having to charge the battery with a jump pack and trickle charge |
Yes, it can cause this because the battery may have been trying to live at a low state of charge. "SLI" (Starting Lighting Ignition) batteries cannot handle that well, the plates fall apart much faster than in a good life. The bad connection means you needed to charge the battery to a high level to start the car, because it caused a voltage drop between the battery and starter when cranking. It also caused a voltage loss between the generator and battery that hurt charging. The poor battery may have been mostly near dead, except when you manually charged it. |
Thanks. Just ordered a new optima and the battery load tester you showed me. And just to clarify... the car wouldn’t start at 6.2v with the bad battery because once I turn the key with the load the battery drains to 3 v and cannot turn the starter? Is that correct? |
If you are measuring at the battery posts that would be the end of life expectation. It could hold a surface charge, but most of the active plate material had become detached from the plates so it had almost no actual storage capacity.
The bad connection issue would cause the voltage at the battery to be higher, sometimes a lot higher, that what would be measured at the starter when cranking. It would mean that once the car was running the voltage at the regulator would be higher than at the battery.
When you get the new battery in it is important to verify the connections and then do a running test to make sure you are charging the battery. 7 volts on the running engine would be great but if that was still only 6.4 volts at the battery you would have a bad connection to find so the new battery doesn't get killed. Most batteries don't die of old age, they're murdered!
It did get one to die of old age. I put a battery in my '65 Dart back in 1994 and drove the car until 2003 with that battery. When new I bet I could have left the headlights on for 8 hours with the car off and still started the engine. At the end of life the positive post was loose in the case and if you left the headlights on for 15 minutes it was not going to start the engine, little active plate material left. It was fall and I was pretty sure that battery would leave me walking home in a cold rain if I tried to push another winter out of it. I also had to replace the positive battery cable due to corrosion from the loose post. I replaced it with an Optima. That car had the mechanical voltage regulator adjusted so the peak voltage occasionally hit, but never exceeded, 14.8 volts. |
OK great thanks. The battery is coming in next week. Once I put it in the car and run a few tests I will report back OK great thanks. The battery is coming in next week. Once I put in the car and run a few test I will report back. Any idea what the voltage will be on a brand new battery? |
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Sat May 15, 2021 2:35 pm Post subject: Re: Another voltage regulator ? |
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| Dan2973 wrote: |
| The battery is coming in next week. Once I put in the car and run a few test I will report back. Any idea what the voltage will be on a brand new battery? |
Should be about 6.3 volts new. Lead acid batteries usually leave the factory fully charged and loose a little bit over time while waiting to be sold.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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Dan2973
Samba Member
Joined: April 12, 2019
Posts: 436
Location: NJ
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| Posted: Mon May 17, 2021 4:16 pm Post subject: Re: Another voltage regulator ? |
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| EVfun wrote: |
| Dan2973 wrote: |
| The battery is coming in next week. Once I put in the car and run a few test I will report back. Any idea what the voltage will be on a brand new battery? |
Should be about 6.3 volts new. Lead acid batteries usually leave the factory fully charged and loose a little bit over time while waiting to be sold. |
Ok here we go ugghhhh. Got the new optima red top battery and the battery load tester you recommended. I tested the old optima with the load tester just to confirm it was shot. I also tested the new optima to confirm it was good check check. Tested the voltage on the brand new optima before I did anything and it was 6.45v. After the load test it was 6.42v
With the engine off I tested at the battery and at the voltage regulator and got 6.43v.
Start the engine and with the engine running at idle at the battery I have 6.28v and at the regulator I have 6.17v
I rev up to about 3000 rpm and at the battery the voltage goes up to about 7v and pretty much the same at the regulator
At the battery with the tester as a rev up and hold it for about 15 seconds it climbs to 7v and as I let off it falls back down to 6.30v
I shut the engine off and it goes back up slowly to 6.41v
I really don’t want to kill this battery too so please help. What do you think and what should I do next. Thanks so much |
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KTPhil 
Samba Member
Joined: April 06, 2006
Posts: 34013
Location: Conejo Valley, CA
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| Posted: Mon May 17, 2021 4:34 pm Post subject: Re: Another voltage regulator ? |
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Sounds like normal battery and charging behavior.
You may have a voltage drop elsewhere, or a short in the starter/solenoid. |
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Mon May 17, 2021 6:57 pm Post subject: Re: Another voltage regulator ? |
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Take it out for a good drive in the daytime with the headlights off. It looks pretty good. The battery will be below resting voltage at a slow idle because the generator doesn't charge below around 1000 rpm. The engine draws a little power from the battery and gets nothing from the generator until above idle.
It looks like your volt meter is pretty accurate. I see you are charging and you have eliminated any significant voltage losses between the generator and the battery with this; "I rev up to about 3000 rpm and at the battery the voltage goes up to about 7v and pretty much the same at the regulator."
Now try repeating that test with the headlights on. It will make sure you are getting decent output from the generator.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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Dan2973
Samba Member
Joined: April 12, 2019
Posts: 436
Location: NJ
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| Posted: Tue May 18, 2021 2:36 am Post subject: Re: Another voltage regulator ? |
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| EVfun wrote: |
Take it out for a good drive in the daytime with the headlights off. It looks pretty good. The battery will be below resting voltage at a slow idle because the generator doesn't charge below around 1000 rpm. The engine draws a little power from the battery and gets nothing from the generator until above idle.
It looks like your volt meter is pretty accurate. I see you are charging and you have eliminated any significant voltage losses between the generator and the battery with this; "I rev up to about 3000 rpm and at the battery the voltage goes up to about 7v and pretty much the same at the regulator."
Now try repeating that test with the headlights on. It will make sure you are getting decent output from the generator. |
Just curious why I have suck a difference between battery and regulator at idle? |
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Dan2973
Samba Member
Joined: April 12, 2019
Posts: 436
Location: NJ
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| Posted: Tue May 18, 2021 2:49 pm Post subject: Re: Another voltage regulator ? |
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[quote="Dan2973"]
| EVfun wrote: |
Take it out for a good drive in the daytime with the headlights off. It looks pretty good. The battery will be below resting voltage at a slow idle because the generator doesn't charge below around 1000 rpm. The engine draws a little power from the battery and gets nothing from the generator until above idle.
It looks like your volt meter is pretty accurate. I see you are charging and you have eliminated any significant voltage losses between the generator and the battery with this; "I rev up to about 3000 rpm and at the battery the voltage goes up to about 7v and pretty much the same at the regulator."
Now try repeating that test with the headlights on. It will make sure you are getting decent output from the generator. |
Just curious why I have suck a difference between battery and regulator at
Just an update. I’m not able to take it for a ride because I have 4 yards of mulch in front of the garage. I was able to check the generator output buy grounding the DF and testing voltage on the D+. As I rev up the voltage spikes to over 20 volts. |
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EVfun
Samba Member
Joined: April 01, 2012
Posts: 5481
Location: Seattle
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| Posted: Tue May 18, 2021 2:57 pm Post subject: Re: Another voltage regulator ? |
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| Dan2973 wrote: |
| EVfun wrote: |
Take it out for a good drive in the daytime with the headlights off. It looks pretty good. The battery will be below resting voltage at a slow idle because the generator doesn't charge below around 1000 rpm. The engine draws a little power from the battery and gets nothing from the generator until above idle.
It looks like your volt meter is pretty accurate. I see you are charging and you have eliminated any significant voltage losses between the generator and the battery with this; "I rev up to about 3000 rpm and at the battery the voltage goes up to about 7v and pretty much the same at the regulator."
Now try repeating that test with the headlights on. It will make sure you are getting decent output from the generator. |
Just curious why I have suck a difference between battery and regulator at idle? |
I'm not sure, but that is what to watch. One source of funny readings is the ripple. The generator voltage is bouncing up and down, just a little and very rapidly as each commutator segment goes by. Some volt meters don't average that out very well. The battery is a big filter smoothing it out and doesn't care about ripple.
A repeat of the voltage tests with the headlights on may tell you more. Hopefully you can still hit 6.5 volts at about 2000 rpm with the headlights on. If the voltage just won't rise under load I would suspect the generator. The regulator has already demonstrated it can charge and regulate voltage. I think 99% of your problem was that loose ground, causing a voltage drop between the battery and rest of the car when charging and when cranking. The other 1% is that the VW 6 volt system was not built with much working margin.
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| Wildthings wrote: |
| As a general rule, cheap parts are the most expensive parts you can buy. |
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Dan2973
Samba Member
Joined: April 12, 2019
Posts: 436
Location: NJ
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| Posted: Tue Jun 22, 2021 9:06 am Post subject: Re: Another voltage regulator ? |
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| Ok guys I just wanted to update about the battery issue. I believe the dead battery was coming from the trans axel ground strap being loose as a goose. I received a new red top 6 volt battery and installed it. Drove the car and ran some tests with a test light and meter and everything seems to check out. My question is with the meter on the battery and the door open (interior light on) should the voltage be dropping from like 6.50 to 6.45v as I’m watching? Is this normal? |
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Eric&Barb
Samba Member
Joined: September 19, 2004
Posts: 24764
Location: Olympia Wash Rinse & Repeat
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| Posted: Tue Jun 22, 2021 9:32 am Post subject: Re: Another voltage regulator ? |
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Only if you have something turned on in the VW.
BTW you are missing the boot around the clutch and accelerator cables where they go into the body. That boot is need to keep water, mud, dirt, dust, sand, etc. out of there.
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In Stereo, Where Available! |
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herbie1200
Samba Member
Joined: April 27, 2006
Posts: 833
Location: Rome - Italy
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| Posted: Fri Jun 25, 2021 2:58 pm Post subject: Re: Another voltage regulator ? |
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Stop with wrong hints, the measured values are pretty normal.
It is normal that, when engine idling, voltage on the B+ terminal is lower than when engine is shut off.
It is typical of an old electromechanic regulator.
It has a "reverse current" when idling, i.e. when idling a lot of current (>5A) goes back from the battery to the generator. This is an issue especially when driving in town with a lot of stop and go.
If you want a more scientific argumentation, the regulator has not a diode (as it is in solid state regulators) and when generator is revving low, but the "minimum" contact are still closed, energy flows from battery to the generator.
When the minimum contact finally opens, the waste of energy goes away, this is noticeable by the red light going on. |
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