Battery Equalization question

[Roc]

Hi all,
Thought an electrical savy person can have a reason for this situation.  I have 6 volt golf cart batteries that I started equalizing last weekend.  I have a Truecharge 40+ charger.  Here's the situation.....  I isolated the bank to be equalized by putting my selector switch to the reserve battery.  So my systems were powered by the reserve battery and the bank to be equalized was off the grid.  I triggered the equalization process on the charger.  All seemed like it was going fine.  I washed my hands, and the water pump went on.  When the pump cycled, I noticed the volt meter reading (set to read the bank that was being equalized) dipped down a few tenths of a volt.  As soon as I turned the water off and the pump stopped, the volt meter returned to the display it was before the pump cycled.  I switched the volt meter to read the reserve battery.  I turned on the water and noticed the volt meter reading to significantly change, which made sense since that battery was taking the load based on the selector switch position.  I can't figure out why the volt meter moved when it was reading the bank being equalized when the pump cycled.  Intuitively, that bank should not have any load since my selector switch was set for the other battery.  I checked the connections on the battery switch and it all seemed correct.  Any idea of why the meter moved a few tenths of a volt?

[KWKloeber]

Roc

Here's my analysis (unproven, just my $0.02.) 
The reserve isn't totally isolated from the house bank.  By whatever different cable paths, you have all your negative battery posts tied together.  Remove the neg cable from the house and I bet you see no V difference with the pump circuit closed.

Let's say all batteries read at an even 12 volts.  But a voltmeter isn't reading some absolute voltage, it's merely reading the difference between points.  In this case it's reading the difference between the house positive post and the reserve neg post (assuming "zero" V loss in all the negative cables.)

When we run current thru a circuit, the difference between the pos and neg posts isn't exactly 12V any more (until the circuit is open again.)

The neg post of the reserve battery (and therefore the house neg posts) had some voltage bled to then thru the pump circuit, so the meter showed the difference between them to be a few 10ths less than 12 volts.

Or, something like that. Ha.

I hope J Sail agrees!!

PS: (Ken's corollary) - You'll get a different V drop on the reserve with the house bank totally isolated.

[Roc]

Hi Ken
Your explanation is exactly what I was thinking, but couldn't come up with the theory behind it.  I did figure intuitively, it may have been the fact that the neg leads are all connected and there was some kind of trace bleeding of the load.

[captran]

does it take over a week to equalize a bank of golf cart batteries?    I just started my equalization last night on two banks, but won't be on power beyond noon today.

[Roc]

Hi Randy
My friend equalized his bank of 6 volt golf cart batteries, with the same charger I have.  He said it took three separate periods, about a few hours each time, to get his bank to read 14.8 volts.  I did mine for 6 hours the first try with the bank reading 13.95 volts.  The second try was for two hours and the bank reached 14.03 volts.  I'm guessing maybe one or more tries to get the voltage to increase.

[captran]

thanks.  I'll write down those numbers and see what I get.  I use a link 20 to give me amp hours and amps.  I started my equalization last night at 8ish.  at 830 this morning my link says the volts are 13.65 and 13.70 (banks 1 and 2) and the amps being delivered are .2 for each bank and total amps delivered in past 12 hours is 2.6 and 3.1.  same true charge 40+ that you have.  I often see 14.6 when charging on shore hook up, but usually just keep tabs of what's going on with volts and amp hours when out cruising for the summer.

[Stu Jackson]

My understanding is that equalization should ONLY be done with full battery banks.

That's why it is so surprising to me that you're both reporting that it is taking ages for the voltage to rise.

[Noah]

I also heard that any equalizing the batteries operation should not be left unattended for safety reasons.

[Roc]

The truecharge instructions state that upon starting equalization, the charger will bring the batteries to full charge (if they are not already).  Before I triggered the process, my bank was on the charger overnight, so I'm guessing they were at or close to full charge.  Also, I didn't leave the process go unattended.  I think the long time is due to the sulfate on the plates to slough off.  I haven't done this in over 10 years, so that's why it takes time.  My friend, who recently did this with the same charger, did this after several years and it took him three tries to get the voltage up.