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Old Nov 16, 2004, 12:09 AM
Registered User
Gilbert, AZ
Joined Aug 2004
129 Posts
nimh receiver pack failure???

I just had a receiver pack failure in my glider, it was like some one shut off the receiver, one second it was flying the next second zero control. it was a 640mah 4 cell pack that had recently been charged and it was only a few months old. when I tested it after the crash(more like a really bad landing) it had 4.8 volts static and when I turned on the receiver in dropped to 2.7 volts and wouldnt move a thing. anyone heard of a failure like this. could I have done something wrong. too high of a charge rate? discharge battery too much? I just started using nimh batterys for receivers and I dont know if I should continue to do so , maybe I just got a cell that was made on a monday, if this is an isolated incident I would love to keep using nimh receiver batterys mostly because theyre size allows shoving them way up into the nose of the gliders. by the way I the failure occured in a descending spiral I broke my v-tail on landing and should have it back in the air after a $20 tail replacement. sometimes you get lucky
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Old Nov 16, 2004, 01:15 AM
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Chicago
Joined Feb 2003
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Did you try to charge it?
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Old Nov 16, 2004, 06:45 AM
Southern Pride
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Haralson County GA. USA
Joined Oct 2004
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it was a 640mah 4 cell pack that had recently been charged and it was only a few months old. when I tested it after the crash(more like a really bad landing) it had 4.8 volts static and when I turned on the receiver in dropped to 2.7 volts and wouldnt move a thing
-------------

That's the reason that battery voltage has to be checked under a load.
This is what happens a lot when you fast charge transmitter and receiver packs.The volts goes up fast but it takes time for the Ma's(capacity) to be replaced.

Charles


Charles
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Old Nov 16, 2004, 06:45 AM
Southern Pride
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Haralson County GA. USA
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-------------
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Old Nov 16, 2004, 07:03 AM
Registered User
Letchworth, Great Britain (UK)
Joined Jul 2004
11,715 Posts
My first NiMh motor battery did the same thing first time out. I had charged it at about 2A (it was a 3300 pack, so 3A or more would be 'normal' charge rate), but friends at the field told me that I should charge and discharge it at a much lower rate a few times. So I cycled it a couple of times on my slow charger (probably only 100mA) and it's been okay from then onwards.

So, you need to charge it at much less than its normal charge rate for the first couple of times.
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Old Nov 16, 2004, 08:17 PM
EDF Head
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Stavanger, Norway
Joined Feb 2000
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Quote:
Originally Posted by Johnnie
when I tested it after the crash it had 4.8 volts static and when I turned on the receiver in dropped to 2.7 volts and wouldnt move a thing.
Your cells are empty. Recharge for 16hrs at 65mAh and discharge it, repeat once.
How recent is recently charged? What was the ambient temperature?
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Old Nov 16, 2004, 08:43 PM
RIP Ric
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Marietta, GA
Joined Jun 1999
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Any model that uses a Rx pack, I cycle that pack the day before I plan to fly it.
..a
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Old Nov 17, 2004, 01:07 AM
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Gilbert, AZ
Joined Aug 2004
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in response to several questions I charged the pack the night before, I did not try to charge the pack after "the incident" , I did not cycle the pack when I first bought it or any time after that, ambient temp was 70 F , I,m going to replace the pack(I already have a new replacement) and I'll try the low amp rate cycle a couple of times before putting it into service Thanks everyone for the input
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Old Nov 17, 2004, 01:28 AM
EDF Head
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Stavanger, Norway
Joined Feb 2000
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Since you say the pack was charged the night before new questions arrise:

1 - What charger did you use?
2 - What charge rate did you use?
3 - For how long?
4 - How long did you fly before it failed?
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Old Nov 17, 2004, 06:56 AM
RIP Ric
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Marietta, GA
Joined Jun 1999
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Charging does not ensure a pack is good, which is why I put one cycle on my Rx packs before flying - some models don't get to fly very often..

Capacity under load (I usually use C for Rx packs, with a 1V/cell cutoff) is, however, a great indication of pack health.
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Old Nov 17, 2004, 01:50 PM
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Chicago
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Quote:
Originally Posted by Andy W
Capacity under load (I usually use C for Rx packs, with a 1V/cell cutoff) is, however, a great indication of pack health.
Exactly, and considering that this pack is small and its capacity under load will be even smaller, depending on the amp draw of your glider and flight time, its possible that you just used it up, also nimh self discharge pretty fast, so if it was not charged before the flight there were less mah to start with...
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