QPCM Receiver dual Battery question ?? - RC Groups
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Dec 19, 2006, 01:53 PM
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Easystern's Avatar

QPCM Receiver dual Battery question ??

Dear Mike,

i have 8 hitec rx's in use , 2 qpcm HPD-07RH !! and i am very satisfied with all my hitec products include my eclipse 7 an my Laser 4.

My question , i will use 2 Rx batterie packs as an safety pre caution in my expensiv rare bear reno racer.
Does the receiver equalise the batteries ? and if one fails does the rx use the right and strong one.The rx is made for two batteries and has two connectors.

in some cases i think it is naccesarry that the two batteries have some diods to get not empty by each other, if i understand this right , iam not a professional elektronik guy.

thanks for info

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Dec 19, 2006, 05:26 PM
Registered User
Good reference courtesy of the R/C Battery Clinic is :
Parallel Operation = Reliability & More Flight Time
Have used this system in my large models for many years using a variety of RX including QPCM RX. If using 5 cell packs in an expensive model, I suggest use of voltage regulators of at least 5A set at say 5 - 6V max will provide greater peace of mind. Voltage regulators prevent early burn out of servos (especially digital) as voltage of 5 cell packs is excessive when used to soon off chargers, especially fast top up at the field.
DIY regulators under "Electronic Circuits & Connectors for RC & Modellers." on my web page.
Alan T.
Alan's Hobby, Model & RC Web Links
Dec 19, 2006, 06:02 PM
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XJet's Avatar
Alan, I've been running all my flight-packs on 5-cells for years (and fast-charging at the field) without a problem.

I see no point in using a 5-cell pack and then regulating it down to 5V, all you're doing is introducing another point of failure, spending more money and wasting power heating that regulator.

Although most 5-cell NiMH packs come off a charge with over 7V, this is *very* transient and will soon drop back to nearer 6.5V, something that a good quality servo and receiver will handle without any problems.

People ought to also be aware that a good digital servo can draw well over an amp. If you're using a 5A regulator you might still overload it doing manuvers such as snap rolls (where all the servos are drawing high currents simultaneously). If you're using Hitec digitals with such a setup, there's a very real risk that the regulator will not be able to provide the necessary current and this will cause the voltage to sag -- with subsiquent servo-reset, a process that takes about a second before the servos wake up.

When it comes to batteries my philosophy is "keep it simple" because simple=reliable.
Dec 27, 2006, 04:18 AM
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Easystern's Avatar
Thank's for the info and thank's for the links , that will help
Mar 30, 2017, 03:40 AM
Registered User
I have a lipo connected to a BEC giving out 5Volts, I wish to also use a 5 cell NIHM as a back up battery just in case the BEC failed can I plug both into my Spektrum receiver I have a spare slot.
Mar 30, 2017, 11:18 AM
Xpress..'s Avatar
Originally Posted by ferring
I have a lipo connected to a BEC giving out 5Volts, I wish to also use a 5 cell NIHM as a back up battery just in case the BEC failed can I plug both into my Spektrum receiver I have a spare slot.
Generally speaking, no you cannot. Spektrum related questions need to be asked in the appropriate forum, this forum is strictly for questions pertaining directly to Hitec RCD and Multiplex equipment.

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