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Rx Battery Questions

Old 11-07-2011, 01:36 PM
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RCFlyer44
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Default Rx Battery Questions

OK, I totally get the charging deal for LiPos as far as not letting the go below their nominal voltage and where they should be when fully charged (about 4.2 volts per cell), however I can't find the same information for NiMH batteries and I am using a 2000 mAh 4.8V NiMH battery pack for my receiver and controls in my new Super Cub, typically I haven't been letting it get below 4.8V before charging and usually get 5 or 6 flights before charging.

Can anybody give me the break down for NiMH batteries?

Thanks in advance!
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Old 11-07-2011, 04:25 PM
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flydiver
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Absolutely full > about 1.4v/cell
Nominal > 1.2v
Near dead > 1.0v
Unfortunately the unloaded voltage reading on NiXX are pretty useless. You can take a dead cell, put a very small charge on it and it will read 1.2v even though there is nothing in it. You need to put some kind of a working load on it to test properly.
They have a discharge curve like lipo with an initial sharp drop to nominal area for a good while then another sharp drop at the end.

2000mA RX pack in a [Horizon] Super Cub? What are you running in it? That should last for hours and hours unless you are running a bunch of additional stuff on it. At 4.8v you have merely gotten into the middle of the operating range.

Lots of good reading:
Technical Tips for NiCd and NiMH Battery Pack Users

Learn About Batteries
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Old 11-07-2011, 06:47 PM
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dumo01
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If you are using a seperate receiver pack you might consider getting a meter that checks the battery with a load like:
http://www.hobbico.com/fieldequip/hcap0356.html

I have this one and it works well and realtively cheap. The are other variations on the market as well
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Old 11-07-2011, 10:52 PM
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Interesting on both replies, thank you. Yes I don't think I need to charge it all day but after a few flights guys at the field were telling me to check it and it gone down only about .2 volts. I have all the control surfaces including flaps (which I do play with a lot) and then nav and landing lights which I really don't mess with unless it is twilight or a little darker.

I just knew nothing about them as I do the LiPos so wasn't sure what to get other than reading voltages and charging whenever I got down to about 4.8 volts. One guy said he keeps his plugged in all the time at home to his plane but has a timer that comes on for two hours a day, sounds reasonable to me, but I just didn't know.

I like the Hobbico tester, might have to invest in one, but since I crashed the plane for the second time today and it is the only one with a Rx battery I may hold off. I have Castle BECs (10amp) for my Sportster EP and going to put the another one in my Airfield T-28.

Thanks guys!!
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