Re: (ET) re: battery testers

[XURQ03A prodigy com ( LEE A HART)]

> 1. Wouldn't you need to actively adjust resistance to maintain 75 amps?

Ideally, yes. In practice, no. If you just want to know amp-hours, use 
average
amps [ (AmpsAtStart+AmpsAtEnd) / 2 ] and multiply by time. If you use light
bulbs for a load resistor, you'll find they automatically draw about the 
same
current despite the voltage change during the test.

> 2. Would you test the 36 V pack, and then test individual batteries if
>    a problem was found?

For only 36v, I would test the individual batteries. It takes a little 
longer,
but you can immediately spot any weak ones. The weakest battery sets the
amp-hour capacity of the entire pack.

You can test the whole pack if you are in a hurry and have a big enough 
load.
However, you will have to watch individual battery voltages and end the 
test
when the first one falls below 5.25v (for 6v) or 10.5v (for 12v batteries).

> 3. Is 75 A the correct testing current for our 6 V batteries? How about
>    for the 12 V batteries used in E8s?

The standard test for a 6v golf cart battery is to see how many minutes it 
can
deliver 75 amps before the voltage falls to 5.25v.

The standard test for a 12v battery is minutes at 25 amps before voltage 
falls
to 10.5v.

This isn't necessarily the best (or worst) way; it's just a standard way 
to do
it. All battery manufacturers take this data, and customers can use it to
compare different batteries.

> 4. Has anyone built their own tester where they didn't need to stand next
>    to the test rig constantly making adjustments and taking readings?

Yes; I have. I currently use a Cruising Equipment E-meter with lift lockout
option. The lift lockout output powers a relay whose contacts switch the
battery between the load resistor and battery charger. The E-meter and 
relay
will cost you about $250.

Or, I used to use a home-made tester. It was just a 6v relay, load 
resistor,
and battery charger. The relay coil had a zener diode and rheostat in 
series,
which were set so the relay dropped out at 5.25v (dead) and pulled in at 
7.5v
(fully charged). Its contacts switched the load resistor, charger, and a 
clock
to record discharge time.

> 1. Has anyone tried one of these new battery desulfators yet?
> 2. Has anyone tried some new technology testers yet?

Most batteries don't die of old age; they are MURDERED by abuse. But they 
are
pretty tough; even after years of abuse, a little tender loving care will
bring back some capacity.

You can buy a little black box to "rejuvenate" a battery. The instructions 
say
 - clean and tighten the battery terminals
 - charge the battery with a good charger to 2.5v per cell, and hold it 
there
   until the current falls below 2-4% of the battery's amp-hour capacity
 - check the water level, and add water if it is low
 - discharge the battery with a modest load to 1.75v per cell
 - charge it up again as described above.

The battery will have miraculously improved in performance and amp-hour
capacity, even though the "black box" has nothing in it but hot air. Simply
taking proper care of the battery is what made it improve; not the magic 
black
box.

Some miracle cures are totally worthless. Some actually work (sort of), 
but at
a very high cost; like a tiny bottle of sulfuric acid (ordinary battery
electrolyte) at $10 an ounce, or a 1amp battery charger for $100.

The real problem with most of them is the lack of proper double-blind 
testing.
They depend on high-pressure marketing and testimonials from people with no
credentials, rather than actual specifications or scientific measurements.

Lee Hart                     If you would not be forgotten
4209 France Ave. N.          Soon as you are dead and rotten
Robbinsdale, MN 55422 USA    Either write things worth the reading
phone (612) 533-3226         Or do things worthy of the writing
e-mail XURQ03A prodigy com   (Ben Franklin, Poor Richard's Almanac)