ianellison

My cab has a 75 amp/hour battery which I ran down last year by test raising and lowering the electric hood. Took it to a motor electrics place and they found the electrolyte needed topping up (was about 66% depleted) and they recharged it over 48 hours. I don't know how old this battery is.

Meanwhile I bought a new Exide 65 amp/hour battery and ran my car on it.

I have a modern self adjusting trickle charger that I use alternately on my car and the old battery (kept as a spare)so they are both constantly topped up.

Question is should I put the old 75 amp/hour battery back (which is the correct capacity for a cab) or should I leave the new 65 amp/hour in? I intend to take a long trip and the battery will need to cope with plenty of cold starts and hood lowering and raising without the trickle charger. I have checked my alternator and it is producing 13.8 amps at average revs.

Is there a non destructive way of measuring the condition of a battery and its ability to hold a charge? Your opinions & experience welcomed!

ianellison

Ooops! I mean't 13.8 volts at average revs!

Edgy01

The density of the electrolite is your first clue. They make battery testers. Start with that, and then monitor it. With a battery you're not familiar with you will have to test it over and over again, as you have no history on the cells themselves (the lead plates). Many times older batteries build up a bunch of junk at the bottom of their cases. That's what ultimately kills it, when two or more plates are shorted out by all that debris in the bottom.

ltc

The easiest/best way to test a battery is with an AC transconductance (or transimpedence....it's sometimes called by either name) meter. Very quick and reliable, at least from an electrical engineering perspective.
Most shops have one, they're a couple hundred $$.

Richard Curtis

Dunno if this is accurate but I've read that an alternator should be putting out 14.5 volts at 2,000 rpm. Your 13.8 volts might be low and indicative of an alternator-related problem.

92C2Targa#119

Get a low cost battery load tester for $10-20 from a auto parts store and a multimeter form a electronics store and then load test the battery.
http://www.harborfreight.com/cpi/cta...emnumber=90636

If the voltage drops off fast (below 11.5 volts) it's bad. Before you load test it, you should have an open cell voltage of +12.5 to 12.8VDC.
2.25 to 2.35VDC ( 13.5 - 14.1VDC) per cell is a good charger or alternator.
13.8VDC sounds good to me.

After adding water you should equalize charge a battery (14.4VDC) for 72 hours, and float it (13.8VDC )for additional ~30 hours. I would do this with the battery out of the car and checking occasionally that you’re not boiling the electrolyte.

Walton

porschedog

Ask your brother-in-law to touch his tongue to the terminals.

Bearclaw

Ask him? It's hard to stop mine from doing it!!!
He says he only does it for the lead. Yeah, right...