[Ken Currell]

I just put a new battery pack in my Royal Evo transmitter.
It's been turned on for 15 hours and it has just dropped to 7.2 volts which is the nominal voltage on a Royal Evo transmitter.

I am using a 2S2P Makita Lithium Ion pack. It gives me more than 3000 ma capacity.

I'll post some photos of the conversion process.

1. Remove the back cover.
2. Remove the battery pack.
3. Undo the screws that hold the battery clips in place and remove the clips.
Your tx should now look like the one in the photo.

[Ken Currell]

Continued ....

4. Replace the screws from the battery clips. This is necessary to hold the circuit board in place.



5. Get some stiff file folder paper or bristol board and carefully cut out a template to fit on the bottom of the circuit board. The one in the photo isn't quite completed.



6. Be sure to carefully measure and mark out the holes. The heads of the screws you replaced should fit in the holes. I used a leather punch to do this.

[Ken Currell]

Continued ...

7. Take care to cut the template now or the velcro later to fit around this small group of electronic components. You can see the battery holder screw fits into the hole that was copied from the template to the velcro loops.



8. Cut a length of 2 inch wide velcro and lay it face down on the table. Turn the template over so that the face is against the bottom of the velcro. Center it on the velcro and mark the outline and the holes on the backing of the velcro.

9. Cut out the velcro and punch out the holes.

10. Do a test fit to see if it fits properly. You might need to elongate or slightly enlarge the holes that the screw heads fit into.

11. Be sure that the velcro will not cover the electronic components as previously pointed out. It should look similar to the photo.

[Ken Currell]

continued ...

12. Now you should select whether you want to use a 2S1P or a 2S2P pack. I chose a 2S2P to see how well it would perform and also to see if it would physically fit inside the transmitter case.

NOTE: The Makita cells have a very thin heat shrink insulator. Do not add to the thickness or the pack will not fit inside the transmitter.

13. I started by test fitting the batteries and then wiring each set of cells in parallel.

14. The cells are arranged offset so they will not interfere with the battery connector and the switch connector post.



15. An initial piece of heat shrink helps to keep the cells together but you can slide them sideways to fine tune the fit. Here you can see that Ihave added the wiring as well as a balance connector and battery connector. The grey/white plug has been modified to make it a polarized connector.

[Ken Currell]

16. Here are the connectors



More to follow when I get the pics done.

[Ken Currell]

Battery duration

19 hours 30 minutes down to 6.8 volts

20 hours 45 minutes 6.7 volts

20 hours 54 minutes low voltage alrm sounded. 6.6 volts

[Vulcan1]

Whew thats a long time. Maybe with the amount of flying I got last year I may be able to charge in the fall.
If you look at the first picture you can see the extra switch's Ken has mounted in his transmitter. They are in the upper corners and they are the CK type as they are red but others will work also. Good pic's.
John

[Ken Currell]

Here is the wiring diagram for a 2s2p Makita Lithium Ion pack.

I used a 4 pin polarized connector to attach the battery packs.
The 2 wires on the plug are shorted across the 2 positive (red) and 2 negative (black) pins to make it a 2s2p pack when it is plugged in.

[Ken Currell]

Thins photo adds the balancing connector and leads.

It also shows the shorting jack that changes the pack from a 2s2p to a 4s pack so it can be charged as a single pack. The charging is done at 1 amp and only through the balancer leads.

This ensures that the cells are all balanced.

[Ken Currell]

Here is the completed installation.

The balancer connector tucks neatly into the left hand corner.
It's a fairly snug fit but the 2 extra cells also help to keep the balance close to the original balance point.
It's easier to hold the transmitter that way.