over charging 65 jaguar s type

[gripper180]

hi all, i have a problem of over charging on my 65 s type jag. i changed the voltage regulator for a new after market one same as what was on the car and also tried a friends genuine lucas one and they all read the same. i get 18.3 volts at the battery at 1500 revs and 19.3 volts at 2000 revs. anyone got any idea as to what the problem could be. i have another old car and that goes to 14.7 to 15 volts tops. im lost.

 

[mainline]

hi all, i have a problem of over charging on my 65 s type jag. i changed the voltage regulator for a new after market one same as what was on the car and also tried a friends genuine lucas one and they all read the same. i get 18.3 volts at the battery at 1500 revs and 19.3 volts at 2000 revs. anyone got any idea as to what the problem could be. i have another old car and that goes to 14.7 to 15 volts tops. im lost.

What symptoms were/are you getting to have made you actually check ?
I would have thought that at 20 volts, any filament lamps would be going open.

I'm assuming that the car uses a smart charge system controlled by an ecm using pwm.

Have you tested the battery ?
What sort of meter are you using to measure the voltage ?

 

[gripper180]

hi thanks for your reply. i have a volt gauge in the car which is where i noticed it and made me check. battery all tested fine. i have tested with a multi meter on the battery and also a digital one you plug into cigar socket. no ecm on car. old school electrics.

 

[mainline]

hi thanks for your reply. i have a volt gauge in the car which is where i noticed it and made me check. battery all tested fine. i have tested with a multi meter on the battery and also a digital one you plug into cigar socket. no ecm on car. old school electrics.

Oh, sorry, I thought you were on about a 2015 jaguar .

Did this have a dynamo originally ?

 

[gripper180]

yes it did dynamo as standard

 

[Avo Mk8]

Cars are not my strong point, but if you are talking about a 1965 car, the current and voltage regulator is an electromagnetic/mechanical device which probably requires its contacts to be set up in the car. There's apparently a Lucas (RB310?) document somewhere out there that explains how to do it.
If you are managing to get 18V across the battery terminals, there's surely something wrong with the battery itself? The impedance of a healthy battery should be milliohms, so surely you cannot push the voltage up that high without many hundreds of amps?

 

[gripper180]

Cars are not my strong point, but if you are talking about a 1965 car, the current and voltage regulator is an electromagnetic/mechanical device which probably requires its contacts to be set up in the car. There's apparently a Lucas (RB310?) document somewhere out there that explains how to do it.
If you are managing to get 18V across the battery terminals, there's surely something wrong with the battery itself? The impedance of a healthy battery should be milliohms, so surely you cannot push the voltage up that high without many hundreds of amps?

the regulator on the 1965 jag is a RB340.

 

[Avo Mk8]

the regulator on the 1965 jag is a RB340.

Thanks. Same applies.

 

[mainline]

the regulator on the 1965 jag is a RB340.

To be honest, I would convert it to an alternator.

The only downside of that is that you would have to change to negative earth.

Have the battery checked properly.

 

[gripper180]

To be honest, I would convert it to an alternator.

The only downside of that is that you would have to change to negative earth.

Have the battery checked properly.

neg earth not the only downside, alternator pumps out 45 amps instead of 30 amps and that not good for old wiring or electrical parts that were made to cope with 30 amps.

 

[gripper180]

the battery is fine. i dont have 19 volts in battery. i have 19 volts across the terminals when revving engine. battery is 12.7 volts. spot on.

 

[Avo Mk8]

Sorry, could you clarify - Post#1 "18.3V at the battery"
Post #11: 19V "across the terminals" but 12.7V at the battery.
Exactly what terminals is 19V across? Presumably not the battery leads off the battery, cos isn't that what you'd expect?

Do you have a figure for what the charging current is at the moment?

 

[gripper180]

Sorry, could you clarify - Post#1 "18.3V at the battery"
Post #11: 19V "across the terminals" but 12.7V at the battery.
Exactly what terminals is 19V across? Presumably not the battery leads off the battery, cos isn't that what you'd expect?

Do you have a figure for what the charging current is at the moment?

sorry if im confusing things. start again. if i test battery with multi meter i have 12.7 volts (ok) if i leave meter connected to battery and start car it charges at 18.3 volts at 1500 revs and 19.3 volts at 2000 revs and will probably rise if revs go higher. i have tried 3 regulators and all read exactly the same. with these figures it will cook the battery.

 

[Avo Mk8]

sorry if im confusing things. start again. if i test battery with multi meter i have 12.7 volts (ok) if i leave meter connected to battery and start car it charges at 18.3 volts at 1500 revs and 19.3 volts at 2000 revs and will probably rise if revs go higher. i have tried 3 regulators and all read exactly the same. with these figures it will cook the battery.

Thanks for the clarification.
I am gobsmacked that you can get 18V across a 12V battery. I can't see how that is possible with a properly healthy battery, the battery chemistry should be clamping the voltage around 14.5, and it should take hundreds of amps to raise it above that, if it could even be done.
Are you measuring the 18V directly on the pillars of the battery when charging, or using the chassis for a connection?

I was hoping someone with more knowledge of lead acid batteries would be along to say "18V is impossible", but so far not!

 

[gripper180]

Thanks for the clarification.
I am gobsmacked that you can get 18V across a 12V battery. I can't see how that is possible with a properly healthy battery, the battery chemistry should be clamping the voltage around 14.5, and it should take hundreds of amps to raise it above that, if it could even be done.
Are you measuring the 18V directly on the pillars of the battery when charging, or using the chassis for a connection?

I was hoping someone with more knowledge of lead acid batteries would be along to say "18V is impossible", but so far not!

both

 

[Avo Mk8]

both

So the voltage across the battery posts actually gets to 18/19 volts, and we can't blame a corroded connection somewhere?
The multimeter is on the DC range, not AC (sorry I'm sure you know what you're doing - just looking for an explanation of the impossible!)
I cannot see how the battery is OK. Know anyone with a high load battery tester? Or can you take it along to a garage for them to test?

interesting article here suggesting that a battery might be 'conditioned' over time to take up an 18V characteristic voltage, don't know if this applies only to AGM batteries.

How does a 12 Volt Alternator charge a battery to read 18+ Volts

Hi All, The last few days I have had a riddle to solve and haven't. My Son owns a 2011 Kia Soul and had a very nice battery I could use for my Healey. When checking the battery, it red close to 20 volts if the car was running or not. Surprised by this condition, I placed my charger on the...

www.britishcarforum.com

Might still be easier to try another battery (briefly) to check if this 18V continues?

 

[mainline]

neg earth not the only downside, alternator pumps out 45 amps instead of 30 amps and that not good for old wiring or electrical parts that were made to cope with 30 amps.

Having a fault like you have where a 12 volt lamp having 19 volts across it is far worse.

The alternator feed cable to the battery would be the only one to carry any more current.

Another alternative would be to fit an Electronic Dynamo Regulator