Voltage drop ok?

[Vanagon-tom]

On my 81 VW Vanagon, with engine running, voltage across battery is 13.9 volts. When I turn on all accessories, voltage drops to 13 volts. Is this an acceptable drop?


Thomas

[mazdatech177]

yep, sounds good to me. as long as it doesnt hang below 12.6 volts you arent in discharge condition. 2.1V per cell, 6 cells in your battery

[curtis73]

Agreed. that's fine.

[bm2boats]

Hmmm, The voltage is right. What amps do you need? Why are you measuring the voltage? Is there a problem with the electrical system?

[curtis73]

Because voltage is an accurate measure of the state of charging. You can't practiaclly measure amps without cables the size of your thumb.

[UncleBob]

Originally Posted by curtis73

Because voltage is an accurate measure of the state of charging. You can't practiaclly measure amps without cables the size of your thumb.

with an inductive clamp, you can measure just about any amperage. Its been a while since I bought one, but sears used to have a 600amp inductive clamp meter for under $100

[curtis73]

Very true, but finding one that does DC amps is costly and difficult. Even then, it won't tell you anything about the charging system. The amount of amps moving through the wire could be anything up to the alternator's rated capacity. If you see 10amps, it doesn't tell you anything without knowing voltage.

[UncleBob]

Originally Posted by curtis73

Very true, but finding one that does DC amps is costly and difficult. Even then, it won't tell you anything about the charging system. The amount of amps moving through the wire could be anything up to the alternator's rated capacity. If you see 10amps, it doesn't tell you anything without knowing voltage.

DC inductive clamp meters are quite common. The one I suggested above was DC. That was years ago, I'm sure they offer plenty of models these days.

Most inductive clamp meters still function as a normal multimeter, so you could use the same meter to measure voltage

[curtis73]

If you find one, let me know The last one I found was $538.

[UncleBob]

I'm repeating myself, but sears, under $100. Its sitting in my tool box at work.

[KiwiBacon]

Originally Posted by curtis73

If you find one, let me know The last one I found was $538.

My one was about $US130. It has been invaluable in finding charging and starting problems. Mine has proved accurate +/- 0.1 amp down to the 1 amp range and can read 1000amps.

For example, sluggish starting with the batteries dropping to 16v (24v starting).
Could be the batteries.

Throw the clampmeter around the earth lead, hit the starter and find it recorded 511 amps.
Instantly showing that batteries, connections and wires area ll good. Clean out the starter and it drops to 130amps.

A knowledge of ohms law with a clampmeter will let you know exactly what's going on. Most items you deal with in a vehicle are fixed resistance.

[Vanagon-tom]

[quote=bm2boats]Hmmm, The voltage is right. What amps do you need? Why are you measuring the voltage? Is there a problem with the electrical system?[/quot


My battery kept dying, I would run my va once a week just to charge the bat. I thought it was the alternator being bad but after replacing the bat, its all good.