converting from Nicad to lipo reciever

[Dan Murphy]

hi guys. im just buidling a new RTF tucano 5 foot span aeroplane. i want to use lipo now . I intend to use a 7.4v 1000mah lipo to power the Rx.. can any of you guys tell me what i need to buy.i.e regulator .. i am using the battery to power a spektrum AR610 Rx for the model.

[Martin Harris - Moderator]

I would use a 2S LiFe pack (6.6v) - safe to leave/charge in the model and within the voltage range for most servos. In case of any doubt, you can always connect a 3 or 5A silicon diode in series with the input line to the receiver and it will drop it 0.6v

Edited By Martin Harris on 12/02/2017 18:32:36

[MattyB]

I agree with Martin - LiFe is a better chemistry in general for RXs and servos - but if you still want to run a Lipo just get a 5A rated switching BEC, or if it's a bigger model either retracts and flaps too a 10A would be safer (the Castle Creations one is good and is rated to a true 10A on up to 3S).

[Ian Jones]

If you are not tied to Spektrum, many Hitec receivers have a SPC connection which can take up to 35V.

[Dave Wilshere]

All Rx's will take a 2s Li-Po battery, its the servos that need to be suitable. I always use Li-Po Rx packs, Li-Fe are fussy to charge properly like Ni-mh. Current of a regulator required comes down to the type and number of servos, but since its not a 3-D model a 3A constant load switch regulator or just regulator if you don't mind a sliding switches potential weak point. Powerbox Digi Switch or they do a stand alone regulator too

[MattyB]

Posted by Ian Jones on 12/02/2017 20:52:25:

If you are not tied to Spektrum, many Hitec receivers have a SPC connection which can take up to 35V.

Not a lot of servos can handle 35V though...!

[Phil Green]

That sweeping statement is simply not true Dave, not all receivers will take a 2S Lipo.
And charging a LiFe pack is the same CC/CV process as a Lipo, not 'fussy' in the least and nothing like the CC to delta peak process of an NiMh.

Cheers
Phil

[Dan Murphy]

thanks guys iv ordered a 5amp BEC

[Martin Harris - Moderator]

I've got to agree with Phil - LiFe cells don't need balancing on every charge, although it's no more difficult than with a LiPo, can be fast charged in situ as safely as NiXX cells and don't need the complication and additional failure point of a regulator to work with most servos. A123 and similar cylindrical cased varieties are virtually bullet-proof although I use soft cased ones regularly.

Edited By Martin Harris on 12/02/2017 22:31:54

[John Tee]

The SPC connection on hitec only powers the Rx not the servos

John

[Rich too]

LiFe for me, I like the fact that they can be left in situ for charging unlike Li-Po.

Edited By Rich2 on 14/02/2017 06:35:21

[Martin Harris - Moderator]

I store most of my models in the house so leaving LiPos in situ would be a no-no for me.

[Trevor]

As one who frequents the slopes and flies electric from the flat, I now equip the gliders with 'retired' power packs from the electric models. These are mainly 3s LiPos which still have more than adequate capacity but whose equivalent internal resistance has got a bit high for high current applications. A 5v 3a uBEC is generally used for voltage regulation.

The downside, as has been mentioned, is that receiver packs are often buried deep in the nose of the glider and charging in situ isn't the best arrangement. However, because LiPos hold their charge so well and need charging so infrequently, I usually do this when needed, on the slope, so that model and charger are out in then open. Again, a larger electric flight 3s or 4s LiPo comes in handy for powering the charger.

I've nothing against LiFe batteries but, by not having any at all, my charger stays permanently on the LiPo setting, avoiding one source of human error.

Edited By Trevor on 14/02/2017 10:13:54