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01-14-2006 04:58 PM  13 years ago
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Mr.Bowflex

rrApprentice

Toronto Canada

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4-cell NIMH RX pack
What are your guys thoughts on these batteries in helis? JR NIMH 2000mah AA?
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01-14-2006 09:45 PM  13 years ago
SteveH

rrProfessor

Texas

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I'm useing NMHI 4 cell packs in all my helis with good success. I'm using a 2100 mah pack in my Schweizer 300 (the one I don't fly very much) 2700 mah packs in my 50's (the ones I fly a lot) and a 3300 mah pack in my Predator because it has digital servos. One thing to remember about NMHI batteries is they have a high self discharge rate, so make shure you charge them right before you fly them. I charge all my batteries when I get finished flying and then leave them on trickle charge until I go flying again and it has been working well. I know there will be lots of the new school, fast charge crowd that will scream that that is wrong, but hey, it works for me.The government cannot give you anything without first taking it from someone else.
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01-15-2006 01:47 AM  13 years ago
catzazz

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Vancouver Island, BC, Canada

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keep in mind also that as the Mah is used from a NimH battery it drops its volts quicker than a NiCad, so they are NOT really that great if you run all digital servos, If you use digitals I would suggest that you a 4000 Mah and charge every second to third flight,

Cheers, Mark M,
http://www.pdqflyers.com
Fly like you borrowed it!! Land like you stole it!! visit www.virc.ca
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01-15-2006 01:51 AM  13 years ago
alvinrc

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Mobile, AL, USA

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Just today, I bought a new 2700 mil Ni-MH four cell to replace the 1800 Ni-Cad that went bad in my TSK MyStar 46.

It is charging now on a wall charger at 150 mils. only charger I have at home.
Will use fast charger at field charging at one amp.

I reckon this get the electricity in it OK.

I hate to buy another charger for it.

No digital servos and just easy flying.

Will this work OK.
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01-15-2006 01:58 AM  13 years ago
catzazz

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Vancouver Island, BC, Canada

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I would figure you could charge at 1 C rate or maybe more. That would = to 2.7 amps (2700 mah), should be fine at 150 mah. However it is reccommend that you slow charge the battery the first few times to extend the life, Also keep in mind that you must time the battery, A NimH battery fry intenally if over charged for too long, that is where peak detection chargers come it effect.

Use this program to calculate the charge time

http://birdcagesoft.com/winheli/

Cheers, Mark M,
http://www.pdqflyers.com
Fly like you borrowed it!! Land like you stole it!! visit www.virc.ca
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01-15-2006 02:11 AM  13 years ago
marked23

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Lynnwood, WA

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I use NiMH rx packs exclusively. For helis, I use sub-c cells. I'd generally avoid "AA" size batteries, but "4/5 A" size are OK. It's all about the internal impedance... less is more.

My sub-c NiMH batteries are 3300mah and even with all digital servos, I can fly several flights (6+) before I consider recharging.

You can get GP3700 cells now. If I needed new batteries, I would go with that. hangtimes.com is where I buy them.

-Mark
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01-15-2006 05:52 PM  13 years ago
oldfart

rrProfessor

Vancouver, Canada

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I have used both, high Mah NiMh & high Mah NiCd.

Using analoques in 30/50 size is not critical.

But I found with my two Preds, using all digitals, that I could push the loads high enough in the third flights using the NiMh sells (2400 and 3000) to cause the battery failsafe on my 9Z and 14MZ to kick in.

This does not happen with the NiCds. This is because the NiCads do not drop as much voltage under heavy load so they will not drop low enough in voltage to trigger the low battery failsafe (3.9V if memory serves correctly.

Consequently I now only use NiCd units in most all my helis.

Phil
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01-15-2006 06:56 PM  13 years ago
marked23

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Lynnwood, WA

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Phil,
That's why you need to look at the internal resistance of the cell. Something less than 10mOhms is best for a heli with digital servos. The GP3300 cells I use are 5mOhms, and have no trouble keeping up.

If the NiMH batery you are using does not state the internal resistance, you just don't know.

-Mark
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01-15-2006 08:58 PM  13 years ago
oldfart

rrProfessor

Vancouver, Canada

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I Agree 100% Marked23.

That is why I use NiCds - They all have the appropriate internal resistance
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01-17-2006 02:04 PM  13 years ago
sreuss

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Ontario, Canada

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I went back to NiCd cells on my all-digi PMax
Just to reiterate what a couple of others have said, NiMH cells don't seem to be able to deliver enough current (internal resistance too high) for more than a couple of flights.

I found that I needed to recharge a 2700 mah NiMh pack after the second flight on my all digi PMax, whereas I can get 4+ flights before rechargning on a 2400 mah NiCd pack. To determine that I need to recharge, I'm using an on-board LED indicator that shows voltage while I wiggle all the sticks quickly.

Note that all of this is for pretty hard 3d'ish flying. Im sure that if you're only flying around and doing the odd loop/roll/stall turn, you will find the NiMH cells to be adequate.

FWIW, other local fliers moved away from NiMH as well, but they went to regulated LiPo packs. That seems to be the way to go from a performance stand point, but there is a cost/mainenenance hit that comes with such a move.

HIH,
SteveR
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