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Odd current draw problem with switches

Old 06-30-2004, 12:31 PM
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NE0
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Default Odd current draw problem with switches

I have 3 batteries in and Edge 540 (RX, IGN, Smoke), and they're presenting some odd behavior in terms of voltage drain...

If I charge the batteries to full, and leave them on a table over night, the next day the voltage reading doesn't drop. However, once I put them in the plane and connect them to their respective switches over night, they lose voltage. They'll drop a few tenths of a volt, and a subsequent peak charge will show them to have lost almost 10% mah over night.

Here are the specifics...

1) RX: 2100mah 6v NIMH with MPI Miracle Switch/regulator/charge jack
2) IGN: 1400mah 4.8v NICAD with MPI Heavy Duty Switch/charge
3) SMOKE: 720mah 8-cell AAA NIMH with MPI Heavy Duty Switch/charge

The RX & IGN batteries are new... about 8-10 cycles. The Smoke battery is a year or so old, with at least 30-40 cycles on it.

I know that a solid state switch like the MPI Miracle Switch nevery "really" closes, and theoretically would have some amp draw. However, I'm getting the same problem on all 3 switches, and 80-200mah over night is a lot of leakage. Any advice?

Thanks,

Tom
Old 06-30-2004, 01:41 PM
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azvmax
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Default RE: Odd current draw problem with switches

Hi
I would check to see if the regulator is before switches.
I wouldent think they would be.
Also due a continuity test of all switches.
Check at all ranges on your meter to be sure they are not conducting at high ohm readings.
They are possibly conduting a little current through the grease in the swt but I doubt it.
I would also perform the same test you allready did to confirm your results.
When you charge a battery they will have a surface charge that usually disapates the peak of in a short period of time.
The surface charge will disapate without being plugged into anything.
This is what I would due first to get to the bottom of the situation.
You stated a few tenths of a volt, to me that is normal.
How are you determining that there is 80 to 200 mah's missing out of the batteries ?
AZVMAX
Old 07-03-2004, 10:13 AM
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Default RE: Odd current draw problem with switches

The regulator is not before the switch, and there is only a regulator on one of the three swithches... all 3 of which are doing this.

I only determined the 80 to 200 mah by noticing the few tenths of a volt drop in voltage and then throwing it on a peak charger where they each took about 10% of rated mah to peak out again.

Tom
Old 07-04-2004, 06:59 AM
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Default RE: Odd current draw problem with switches

My experience is a few 10th's is normal.
Also if you charge a pack wait 30min then charge you can usually stuff more in.
We charged a 8 cell sub c 1700mah pack yesterday and we topped it off several times each time at a lower current and it kept taking more in like 400ma.
Old 07-04-2004, 11:15 AM
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Default RE: Odd current draw problem with switches

Gotcha, I suspected as much. I have some glow planes that stay on trickle on a DigiPulse too, and if I take them off trickle, I can still pump more mah in with an Orbit peak charge.

I flew 4 flights yesterday and the batteries performed very well... I think I'm OK. After four flights at 8-10 min each I put them back on peak detect slow charge. The 1400 IGN took about 450 in, and the 2100 RX took about 700 in. So they both used about a third of their batteries capacity to get 4 flights in, and the voltage was still in acceptable range.

I think I'm OK, but I'll keep my eye on them and be sure to top them off before flying.

Thanks,

Tom
Old 07-04-2004, 12:44 PM
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mr.rc-cam
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Default RE: Odd current draw problem with switches

One of the clues that a cell is going south is that the leakage rates will start to become excessive. It is good to observe the leakage when the pack is new, then compare it as it ages. During off-season, I usually charge the pack, let it rest a week, then recharge to see how much mAH was lost. If too much, then the separator layer in a cell is in trouble. Packs with high leakage are not good candidates for use and should be retired.

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