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Discussion Starter #1
I need advice on how to perform quick simple discharge tests on Hawker
PC925s. I've caught references to things as simple as using an automotive
headlight as a load to building a simple discharger, but I'm unclear on
parameters. What is ideal as a discharge tool, how many amps do I want to
draw, for how long, and at what intervals should I monitor status?

Thanks,
Lon Hull,
Portland, OR

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Discussion Starter #2
Hi Lon,

I usually like to test my batteries at a load similar to what I am expectin=
g to use them out. When I test batteries for my motorcycle, I usually try =
to discharge at around 120 amps. I do this with a contactor a couple of pi=
eces of 0/2 cable, a piece of wire hanger and a 5 gallon bucket of water. =
I connect the heavy guage cable to the battery through the contactor and co=
mplete the circuit with the piece of wire hanger in the bucket of water. I=
trim the piece of wire hanger to the correct length for the discharge curr=
ent I am after. This is quick and easy, but does not provide a constant cu=
rrent discharge, so I graph the current over the discharge time and add it =
all up at the end. Light bulbs do a lot better at giving you a constant cu=
rrent discharge, but it can take quite a few of them in parallel to give yo=
u a decent load. John Wayland has a nice aircraft headlight which draws ab=
out 30 or 40 amps when hooked across a 12 volt battery. It's great for ind=
ividually testing a set of batteries. Of course it explodes rather dramati=
cally if you have a brain cramp and hook it across an entire pack :)

damon

> From: [email protected]
> To: [email protected]
> Date: Fri, 2 Nov 2007 09:18:27 -0700
> Subject: [EVDL] Need help with discharge testing
>
> I need advice on how to perform quick simple discharge tests on Hawker
> PC925s. I've caught references to things as simple as using an automotive
> headlight as a load to building a simple discharger, but I'm unclear on
> parameters. What is ideal as a discharge tool, how many amps do I want to
> draw, for how long, and at what intervals should I monitor status?
>
> Thanks,
> Lon Hull,
> Portland, OR
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev

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Discussion Starter #3
I'm not entirely sure what you want to do, but a
simple discharger I've used is a 12VDC to 120VAC
inverter, and light bulbs on the output. Since the
inverter will draw whatever current is necessary to
keep 120VAC on the output, as your battery voltage
goes down, the current goes up. So it's more of a
constant power discharger; usually people use constant
current. But it's still a useful way to match
capacities of random batteries, or see when to stop
cycling batteries when trying to "wake them up" (when
the capacity stops increasing). On the output of the
inverter, I also plug in a mechanical clock, so I can
measure (unattended) how long the battery was able
power the load. The nice thing about this setup is
that the inverter will automatically shut down once
the battery voltage drops below a setpoint.

An old computer UPS can also be used, but the higher
output ones (900W, etc) usually run off 24V, so you
would have to discharge two 12V batteries at once.

- Steven Ciciora


--- Loni <[email protected]> wrote:

> I need advice on how to perform quick simple
> discharge tests on Hawker
> PC925s. I've caught references to things as simple
> as using an automotive
> headlight as a load to building a simple discharger,
> but I'm unclear on
> parameters. What is ideal as a discharge tool, how
> many amps do I want to
> draw, for how long, and at what intervals should I
> monitor status?
>
> Thanks,
> Lon Hull,
> Portland, OR
>
> _______________________________________________
> For subscription options, see
> http://lists.sjsu.edu/mailman/listinfo/ev
>


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Discussion Starter #4
>> From: [email protected]
>> To: [email protected]
>> Date: Fri, 2 Nov 2007 09:18:27 -0700
>> Subject: [EVDL] Need help with discharge testing
>>
>> I need advice on how to perform quick simple discharge tests on Hawker
>> PC925s. I've caught references to things as simple as using an automotive
>> headlight as a load to building a simple discharger, but I'm unclear on
>> parameters. What is ideal as a discharge tool, how many amps do I want to
>> draw, for how long, and at what intervals should I monitor status?
>>

I just use a 2000W inverter and plug in as many 500W (or whatever)
lights as I want for a load. lets you choose
the loading pretty easily.

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Discussion Starter #5
Loni wrote:
> I need advice on how to perform quick simple discharge tests on Hawker
> PC925s. I've caught references to things as simple as using an automotive
> headlight as a load to building a simple discharger, but I'm unclear on
> parameters. What is ideal as a discharge tool, how many amps do I want to
> draw, for how long, and at what intervals should I monitor status?

The standard load for a 12v battery is 25 amps, so I bought a 25 amp 0.5
ohm power resistor. I use a home made cycler, made from a Rudman Mk2
regulator, switching a 12v 40amp automotive relay instead of its normal
on-board 7.5 ohm load resistor. I added trimpots to set the turn-on and
turn-off voltages to 10.5v and 15v. The relay's NO contact connect the
0.5 ohm resistor until the battery falls to 10.5v, and then the NC
contact connect an external charger until the battery rises to 15v. It
automatically cycles the battery (charge/discharge) as long as I leave
it on.

I log data with an E-meter with serial port to an old PC. It's worked
fine for years and thousands of test cycles!

--
Ring the bells that still can ring
Forget the perfect offering
There is a crack in everything
That's how the light gets in -- Leonard Cohen
--
Lee A. Hart, 814 8th Ave N, Sartell MN 56377, leeahart_at_earthlink.net

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