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Old Mar 31, 2008, 01:22 PM
jrerickson
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Valencia, CA
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Battery pack test under load

Just wondering if anyone has used the products here for testing a 4 cell 200 mah nimh pack:

http://www.troybuiltmodels.com/Voltagetester.htm#H9
http://www.maxxprod.com/mpi/mpi-6.html

I'm looking for a flight box tester that won't give the pack too high a load.

JE
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Old Mar 31, 2008, 01:55 PM
Dragons, Windmills. All Same.
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Hi John,

I have the Hanger 9 version from your first link and like it very much. Small, light, accurate and super easy to use. Notice that it is Not limited to cell count as many other units are and have been.
You can check mime at the next SC2 if you like.

There is also a sister product too for testing each or all servos in your ship.
http://www.horizonhobby.com/Products...?ProdID=HAN172

Jared
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Old Mar 31, 2008, 02:04 PM
jrerickson
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Valencia, CA
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Thanks, Jared. I've seen that unit in person and it seems to be a nice way to test the "older" packs. Just wondering if a 500 mah amp load would harm a 200 mah pack. That's 2.5c, pretty high.

John
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Old Mar 31, 2008, 02:45 PM
Dragons, Windmills. All Same.
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Yes, the 1/2amp is a little high the little planes. Yet, a full house DLG can pull this load.
I used this unit when I was flying DLG w/ my 180mah packs and developed no problems.

Jared
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Old Mar 31, 2008, 02:54 PM
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Reno Nevada
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John,

Are you asking about testing the pack while in the DLG? Adam Weston/Phil Pearson had one that plugged into their charging/switch jack. I made one which I have used. Basically the linear LEDs with a few resitors to simulate the on condition. Ping me separately if more info is needed.

Chris Adams
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Old Mar 31, 2008, 03:00 PM
jrerickson
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Valencia, CA
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Hi Chris,

Yes, testing a pack that is in the plane. The units I linked to put the pack under load to see if there is a voltage drop; I'm just concerned that the load applied is a little high. I'd think the most the battery would ever see would be 300 mah with a mini full house (6 servo) plane.

John
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Old Mar 31, 2008, 03:50 PM
Come out swinging
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San Diego
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This may seem crazy, but I fly until the servos start to slow down, slightly. Then, I know the voltage is dropping, and time to charge.

Or maybe one of these: http://www.hobby-lobby.com/testequipment.htm with an added resistor for your load?

Sean
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Old Mar 31, 2008, 04:11 PM
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Chandler, Az.
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Battery pack tester under load

A word of caution, 500 ma load on a 300 mah NMH pack is not recomened for more than a few seconds. Since you would be looking for an immediate voltage drop, you would be ok with either tester, but be aware that neither have the resolution (mollivolts drop) required to tell whether the pack is any more than already dead or just about to die. Nmih batteries have a very flat discharge curve until near 90% depletion.

Bob
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Old Mar 31, 2008, 04:19 PM
jrerickson
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Valencia, CA
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Thanks, Bob. That's what I thought. Not sure if any of the commercial products go down to a low (200 mah) test load.

John
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Old Mar 31, 2008, 06:41 PM
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Battery test - again

John

If I were going to load test a 200 mah pack, I would connect a 24 ohm 1 watt resistor accross the leads of a good digital voltmeter (Radio shack has one that will work I think).

Bob
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Old Apr 03, 2008, 02:23 PM
Scott Zastoupil
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USA, WI, Waupaca
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Another Idea

I use a Hobbico VoltWatch with a ~50ohm resistor soldered in parallel and heatshrunk into the harness. Also had to change the gender of the plug.

http://www.hobbico.com/radioaccys/hcap0332.html
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Old Jun 06, 2008, 08:47 AM
De tramacazo en tramacazo
United States
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Can you post a pic of your Voltwatch-resistor set up?

Hey Szastoupil!

Can you post a pic of your Voltwatch-resistor set up?

What's the difference of having this set-up vs. just "simulating a load" by moving the servos?

Would this resistor do the job?
http://www.radioshack.com/product/in...ductId=2062292

I got a Voltwatch 2 yesterday at my LHS, it works pretty good and I can even see the led lights through my kevlar pod!

-Christian
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Last edited by Christian_C; Jun 06, 2008 at 01:36 PM.
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Old Jun 06, 2008, 03:13 PM
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Pensacola, FL, USA
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Quote:
Originally Posted by jrerickson
Just wondering if anyone has used the products here for testing a 4 cell 200 mah nimh pack:JE
John,
Although no single measurement will tell you how much usable charge is remaining in a pack, it seem logical to look at the voltage DECAY RATE with a digital meter using a load equal to the rated capacity of the pack (1C).
The load resistor for a 4-cell 200 ma. pack would be 4.8/.200=24 ohms. This is not critical, 25 ohms would be fine.
If pack voltage is decaying by hundredths of a volt you are probably OK. Decay by tenths of a volt needs a charge.
I use a double banana plug (Mouser Electronics $2.88)
that fits the spacing of most digital meters from http://www.mouser.com/Search/Product...8%252b8A%3d%3d
And a one to five watt resistor from RS for about $.50 for the load.
The terminal end is a 2-pin JST connector from your junk box that plugs into the pack. See picture below. There are many ways to do this job, but this works good for me.
Regards,
John255
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Last edited by John255; Jun 06, 2008 at 04:42 PM.
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Old Jun 07, 2008, 08:30 AM
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Pensacola, FL, USA
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Quote:
Originally Posted by Christian_C
Hey Szastoupil!Can you post a pic of your Voltwatch-resistor set up?What's the difference of having this set-up vs. just "simulating a load" by moving the servos?Would this resistor do the job?
http://www.radioshack.com/product/in...ductId=2062292
I got a Voltwatch 2 yesterday at my LHS, it works pretty good and I can even see the led lights through my kevlar pod!-Christian
Christian,
I don't have any experience with the Voltswatch but it does appear that is does not have a load resistor. The servos only draw current while they are moving so the load is of very short duration and soon as current stops the pack recovers voltage.

Szastoupil says he puts a resistor in series which would lower the voltage to the reciever from his pack. I suspect an error there.

The resistor you showed is 10 ohms which would give you a .480A load on a 4-cell pack. I Don't know what capacity you pack is. And you would have to have a way to put the resistor across the pack (parallel) to observe the voltage drop with that load.

How's old Gainsville these days? Almost moved there a few years back. Beautiful area and probably better hurricane protection than here on the coast.
Cheers,
John255

Edit:
The resistor shown in your picture is 10 ohms, but the stock nr. indicates 50 ohms. So if you use the 50 ohm the load would be .100A for a 4-cell pack.
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Last edited by John255; Jun 07, 2008 at 10:34 AM.
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Old Jun 07, 2008, 10:37 AM
So. Cal. Glider
Costa Mesa
Joined Mar 2007
134 Posts
Sentry battery capacity gauge.

John,

I have been using a Sentry battery gauge from www.dynamiterc.com. Measures li-po, ni-cad or ni-mh.
Applies a 300ma discharge for 5 seconds.
I have been very happy with the performance.
rcandgolf
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