Re: (ET) re: battery testers

["Steve & Sandy Naugler" <snaugler earthlink net>]

Thanks for your responses on battery testers, but its not enough.  
Therefore
I have what I call "More questions on a battery testers:"
1.  Wouldn't you need to actively adjust resistance to maintain 75 amps?
After all, as the voltage drops from 12ish to 10.5 V ( or 6ish to 5.25 for 
a
6 V battery) the current would drop proportionately, about a 12 % drop in
current.  Couldn't that lead to a significant error in the test results?
2.  Would you test the 36 V pack, and then test individual batteries if a
problem was found?
3.  Is 75 A the correct testing current for our 6 V batteriess?  How about
for the 12 V batteries used in E8s?  Is this published somewhere on the 
web?
Is the 10.5 V for a 12 V battery and 5.25 V for a 6 V battery the correct
test voltage for all liquid electrolyte lead acid cells?
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?
And related questions on chargers?
1.  Has anyone tried one of these new battery desulfators yet?  I was
thinking of it, but haven't yet?
2.  Has anyone tried some new technology testers yet?  My research so far
suggests that a decent modern charger new is priced from $300 - $400.  If
your charger is well and truly dead, it might be worth it, but my chargers
are still functional.
    Looking forward to all your responses, and maybe some controversy if
we're lucky
Steve Naugler

----- Original Message -----
From: David Roden (Akron, Ohio, USA) <roden ald net>
To: <elec-trak cosmos5 phy tufts edu>
Sent: Monday, August 23, 1999 12:29 PM
Subject: Re: (ET) re: battery testers


> From:           "Wombat" <Wombat RealNS com>
>
> > The
> > generally assumed correct test is to load the battery at some level
until
> > its voltage drops to 10.5 volts.  The resultant time is its capacity.
> >
>
> Correct.  Just a few more notes regarding this.
>
> Typically golf car batteries are measured for their minutes of "reserve
> capacity" (RC) at 75 amps.
>
> You would need to connect 3 headlights in series for a 36 volt pack.
> Then you would have to parallel enough trios of headlights to reach 75
> amps.
>
> There are other ways to create loads.  One (somewhat risky) one is to
> fill up a large bucket with water and plunge in heavy conductors.  Raise
> or lower the conductors to change the load.  Some people add salt to the
> water to change the resistance (don't breathe the gas that is evolved if
> you do this).
>
> Another way is to use one or more paralleled electric water heater
> elements of appropriate size in a large bucket of water (this works
> better with the higher voltage packs used in road EVs, however).
>
> And yet another is to use multiple electric space heaters with the
> elements paralleled and connected to the pack, and the fans wired
> separately to run on the AC line.
>
> Testing is a miserable task on a 98 degree day -- a load bank mounted
> outside the garage makes it more bearable.
>
> 10.5 volts is the discharged voltage specified (under load) for a 12 volt
> battery.  For our 6v GC  batteries, it's half that amount.
>
> The most common golf car batteries used (T-105 or US 2200 type, 220 amp
> hours at the 20 hour rate) are rated for around 105 minutes RC.  A
> battery is considered to be at the end of its useful life when it can no
> longer produce 80% of its specified reserve capacity.
>
> FWIW, the usual reserve capacity spec for most 12v deep cycle batteries
> is at 25 amps, not 75.
>
>
> David Roden - Akron, Ohio, USA
> 1991 Solectria Force 144vac
> 1979 General Engines ElectroPed 24vdc
> 1974 Honda Civic 96vdc
> 1970 GE Elec-trak 36 vdc
>