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nuckolls.bob(at)aeroelect
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 Posted: Mon Jan 14, 2013 11:46 am Post subject: Battery spoofer for testing smart charger maintainers |
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While contemplating a series of tests to investigate the
condition of a couple of Bob Noffs' chargers, I suffered one
of those epiphany moments that suggest the legacy test
protocols were exceedingly slow, clumsy and not very creative.
The smart charger maintainer has no way to KNOW what kind
of device is connected to its output terminals. All it can do
is output energy under some protocol (probably semi-constant
current), watch how the 'battery' responds to that output and
react to changes over time.
Went to the bench and clipped these parts together:
[img]cid:.0[/img]
In my case, a 5W 100 ohm resistor was used for a load. A convenient
alternative would be a 35 or 55w halogen lamp from Walmart. You need
two meters and a bench supply capable of carrying the lamp load at
15 volts or more. The lamp load total (along with ratings on your
bench supply) needs to be some value greater than the output current
rating for the SCM under test.
First, hook up the power supply, voltmeter, and load. See power
supply for say 10 volts (depleted battery level).
Clip SCM to the load while monitoring the charger's
output on the ammeter. You should see a current reading that is in
the ball park for the SCM under test. I just did this test with a
Battery Tender. Got an initial charge current of 0.9A.
Put on your "battery spoofer's" hat and slowly increase the voltage
while watching the ammeter reading. Somewhere north of 14 volts you
should see a sharp drop in current. That voltage reading will be
the top-off termination point for your particular SCM.
Slowly decrease the power supply and watch for the amperage to
increase from zero. Adjust the voltage so that you get current
reading on the order of 10 milliamps. This voltage will be the
maintenance float voltage for your SCM under test.
I just tested the two SCMs that Bob Noffs sent me some weeks
ago. Both tested a zero output. So one couldn't do a comparative
looksee for voltage switching levels or maintenance protocols.
You were right Bob. These critters just laid there.
If anyone has a relatively new SCM that seems not to function,
this test will confirm/deny your suspicions. Further, the results
of the testing will offer concrete justification for warranty
claims for either gross failures like I just described . . . or
failure to demonstrate recharge rates and voltages commensurate with
expected performance.
Bob . . .
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james(at)etravel.org
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| Posted: Tue Jan 15, 2013 3:41 pm Post subject: Battery spoofer for testing smart charger maintainers |
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I would encourage everyone to acquire some form of
bench test power supply . . . 3A is sort of a minimum
10A is really capable of running everything but pitot
heaters.
Amen to that!
I bought a bench PSU for the first time a couple of years ago, and it has been invaluable. It's just a little 0-3A, 0-20V unit. It was a bit cheaper back then, but even at today's price I'd buy it just to save messing about with batteries, mains adapters, etc.
http://www.maplin.co.uk/bench-power-supply-with-lcd-screen-219129
Well, it was the best thing I've bought, and it's more than repaid me in time saved. I use it all the time, at home and in the hangar.
Case in point, tonight, I've been tweaking the brightness of 12V self-adhesive LED strips. This would have been a tedious task without one, but took 30secs to give me the valuable data that the optimum voltage is about 7.6V and draws less than 0.01A.
On 15 January 2013 17:20, Robert L. Nuckolls, III <nuckolls.bob(at)aeroelectric.com (nuckolls.bob(at)aeroelectric.com)> wrote:
[quote] At 07:04 PM 1/14/2013, you wrote:
| Quote: | Bob,
Any reason the power supply couldn't be replaced with a couple of batteries (maybe a 6V and a 12V) and a rheostat of sufficient capacity? For those of us who don't have a large enough bench power supply.
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Sure. The goal is to provide an adjustable current 'sink'
that can be made to look like a battery that's accepting
a charge. The resistor-lamps 'load' needs to draw only
a tad more current than the rating of the SCM. What
ever source of power you use to drag it over a 10-15
volt range is up for grabs. There are dozens of ways
to do it.
I would encourage everyone to acquire some form of
bench test power supply . . . 3A is sort of a minimum
10A is really capable of running everything but pitot
heaters.
Marlin P Jones has a nice selection which you can view
at mpja.com and doing a search on 'bench power supply'.
eBay has some attractive options in new and used
power supplies. If anyone is attracted to an eBay
offering and considering a bid, I'd be pleased
to review the offering if you'll email me directly
so as to avoid creating a bidding war amongst members
of the List.
An adjustable, current limited power supply is a
real asset during the design, construction and maintenance
of your airplanes electro-whizzies. I own a half
dozen of various sizes . . . couldn't do what I do
without them.
Bob . . . | Quote: |
ist" target="_blank">http://www.matronics.com/Navigator?AeroElectric-List
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