Will Rx be able to take more mAh? - RC Groups
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Jan 06, 2005, 02:16 AM
Registered User

Will Rx be able to take more mAh?


I have some old EXPERT Rx with old batteirs that Don"t hold a charge. I wanted to make some new battery packs. I bought some Rayovac NIMH AA's. Will the 1800mah AA's harm the Rx's or will it just give me more time to fly? R0D
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Jan 06, 2005, 04:23 AM
Registered User
No harm, just more flying time.

Only extra VOLTAGE can cause problems, extra capacity has no effect.

Steve
Jan 06, 2005, 09:40 AM
S.A.D. member
ivanc's Avatar
Slipstick is right. I just want to add another hint - if you're in the US, you can buy 4-pack Energizer 2500mAh at Wal-Mart for around $9. You'll get even more time to fly with these. :-))
Jan 06, 2005, 11:17 AM
Fly R/C writer
Receivers have voltage regulators and really could care less about the input voltage...except maybe when being asked to take about 10KV. Just kidding. But I would be wary of the very high capacity battery packs like the 2500-mA cells. They may not have the low internal impedence to meet the demands of the servos in the air, and that could cause you some problems. If you're just droning along and most of the flying is basically hands off free-flight, no problem. But if you are turning constant rolls, snaps and loops, you might not like what happens when you call for a snap roll, and because of the power demand by the servos, you get a receiver shutdown when the battery cannot provide the current.

mlee8249
Jan 06, 2005, 01:33 PM
Registered User
ebill3's Avatar
Quote:
Originally Posted by mlee8249
Receivers have voltage regulators and really could care less about the input voltage...except maybe when being asked to take about 10KV. Just kidding.
Every voltage regulator I have ever heard of does in fact have an input voltage limit. The statement that they could care less about the input voltage is not accurate. I don't know what the limit is, but for sure there is a limit.

Bill
Jan 06, 2005, 04:52 PM
Registered User
Most of the receivers I've looked at don't have an internal voltage regulator at all. And certainly servos don't and they get the full battery voltage too. So excess voltage will kill the lot of them very quickly.

mlee8249 has an interesting theoretical point about current demand....at least if you're flying a huge model with lots of digital servos. But for more normal models I don't think I've yet seen any 1800mAh cells which can't deliver at least as much as the basic 600mAh NiCds that were standard with most equipment.

Steve
Jan 06, 2005, 05:12 PM
Registered User
ebill3's Avatar
Yep, I think mlee8249's statement that "Receivers have voltage regulators and really could care less about the input voltage......" Is irresponsible.

I suspect that if a person were to connect their 5 cell LiPo directly to a receiver, there would be a lot of smoke from the receiver and the servos. Given mlee8249's assurance that anything is OK, I'm not sure everyone who reads these threads has the electrical knowledge to prevent such a disaster.

Agree with slipstick - it is going to take a whale of a load to take a 4.8 volt, 2500 mah pack down to the point a receiver will not function.

Bill


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