Hi

i have an old Sanwa 2 channel radio, think it dates back to somewhere in the vicinity of 1986, 87 or 88, (it's got a needle indicating battery strength 1-8) i'd like to bring back to life with a 3s lipo.
My question is would it be possible to use a 3cell pack on it ?

For my old jr x378 radio i used a 3 cell pack without problems, just would like to know if it would be a problem to use 3 cell lipo's on this 2 channel old radio, for an rc car ?

Originally Posted by Axefly

Hi
i have an old Sanwa 2 channel radio, think it dates back to somewhere in the vicinity of 1986, 87 or 88, (it's got a needle indicating battery strength 1-8) i'd like to bring back to life with a 3s lipo.
My question is would it be possible to use a 3cell pack on it ?
For my old jr x378 radio i used a 3 cell pack without problems, just would like to know if it would be a problem to use 3 cell lipo's on this 2 channel old radio, for an rc car ?

No problem if a simple cheap voltage reducer is added, see schematic attached:
Batteries_Lithium Polymer - Do Not Use 3S Lipo in Transmitters

Alan T.
Alan's Hobby, Model & RC FAQ Web Links

o krut i don't have access to any of those goodies, will it not work without it ?

I mean my jr which x378 which also used to work on 8 nicads just as this old transmitter works well without voltage reducers, should it not be the same with this old transmitter ?

Originally Posted by Axefly

o krut i don't have access to any of those goodies, will it not work without it ?

I mean my jr which x378 which also used to work on 8 nicads just as this old transmitter works well without voltage reducers, should it not be the same with this old transmitter ?

It will probably work. The possible issue is that a 3-cell LiPo puts out 12.6 volts, considerably more than the NiCd pack it's designed for, and may destroy the voltage regulators sooner or later. One solution is to charge the pack to 12v or less. The same is true for the 378.

A more important issue is that the radio may be illegal (it would be in North America) and being wide-band can interfere with other radios on the 72 band.

Thanks, what you guys say make sense, however no one ever even mentioned the fact that the lipo's will damage the transmitters, is it that probable that it would just blow some or other time ?

If it does, will it fry my radio ?
I've been using it on my jr for over a year now without issues

Originally Posted by Axefly

no one ever even mentioned the fact that the lipo's will damage the transmitters

You didn't ask enough people!

Originally Posted by Axefly

is it that probable that it would just blow some or other time?

Heat...if you use a higher voltage the regulator will create more wasted heat energy. If you leave the transmitter on for a long period of time and live in a hot place there is more chance of damage than using it for short periods of time in freezing conditions. But it is only a chance thing...no guarantees that it will blow today, tomorrow or ever.

Originally Posted by Axefly

I've been using it on my jr for over a year now without issues

You might be lucky or maybe this particular transmitter manages to keep cool enough at all times. What you have to decide now is whether you continue doing what you've done for the past year or not. I suppose the question you need to ask is "how would I feel if if blows next week and I crash or injure someone?"

BTW, in Alan's post above he links to a very simple method of reducing the voltage of a 3s lipo using a couple of 1N4001 diodes. As these devices reduce the voltage they will get warm but should not fail under normal circumstances.

Thanks, Well since i went lipo on my jr, i cannot go back so i guess i'm stuck with it.

Do you know if there is any cheap home appliances that i can buy at say a local hardware or so with one of these diodes, otherwise from now on, i'll only charge up to 12v and i guess have more limited battery capacity because of it.