Lithium upgrade to the EVO 9 or 12 transmitter

[Ib Jensen]

I wanted higher performance from my TX battery on my EVO so I decided to try Lithiums, I investigated flight packs and found that 2 cell LiPo packs would rum me about $60. I am sure that there may be better deals available on packs with less than 10C discharge rates, but I didn't run across any. Since I only needed about 300 ma discharge rate max I found that BatterySpace.com had laptop Lithium cells available in 2400 ma size for $8.16. This seemed like a good deal, but I was concerned about preventing over charge or discharge. There is a unit available for flight packs that performs this function. It goes between the battery and the load and cuts off the battery before it goes under its fatal discharge voltage. It would work, but I found that BatterySpace had a small circuit board that when attached to the battery pack not only prevented over discharge but also over charge and acted as a discharge current limiter. It cost $4.99. I found a deal available for a two cell Lithium pack pr wired with the protection board and a 1 amp two cell Lithium charger:

Smart Li-Ion 7.2V charger + 7.2V 2400mAh Li-Ion battery with PCB(bottom)

Part#: CH-UNLI1C04

(Qty: 1 x $35.99)



This looked like the ticket, but since I subscribe to the philosophy that if more is better, then much more is much better I ordered the above kit and 4 2400 ma cells and the protection PCB



One 7.2V PCB for making Li-ion 18650 / 18500 7.2V battery packs

Part#: PCB-LI18650S2

Manufacturer Part#: 0

(Qty: 2 x $4.99)



One LG Li-Ion 18650 Cylindral 3.6V 2400mAh Cell --- New Product
with Pre-Wired Tabs

Part#: LC-18650S4-tab

(Qty: 4 x $9.15)

Discounted Item. You Paid: $8.16



For $37.63 not including shrink tubing and connector (made from standard servo connector) I made a 4800 ma pack.




The two cell pack fit fine by placing a thin piece of foam in the transmitter to cushion the battery I was able to put in the two cell pack without any modification. For the 4 cell pack and found that if I took off the battery clips (which I then placed to the sides so I did not loose them) I could fit in the 4 cell pack. I am not sure what voltage to put as the shutoff voltage in the TX setup since the lowest it will go is 6.7 volts I think but the Li cells will go down to 5.2 without damage, so I put it at minimum. Also the max battery capacity that is programmable is 2450 (about) so the TX will give a false reading using the 4 cell pack. I did buy a spare battery circuit board so I could make three 2400 packs.

Now how do I test the system? I could leave it on all day at the field I suppose, now that I have 3 packs that will work in the EVO. In any event,using my 3300 flight packs and the 4800 EVO the 8 hour level 5 flight requirement is easy.

Ib

Shown are the 4800 ma 4 cell pack (2 X two cells in parallel), the two cell 2400 cell pack and the original 6 cell NiMH pack .

[Geoff Akerlund]

are you able to charge this through the transmitter? :confused:

[alexcmag]

Here in Brazil most people (including me) are using 3S LiIon packs on Futaba TXs, instead of the original 9,6V NiCd pack.

Main advantages:
- Increased capacity (1400mAh on LiIon, 650mAh on NiCd)
- Less weight (120g on LiIon pack, 200g on NiCd pack)
- Less self-discharge (LiIon can last months charged if unused, NiCd is almost useless after 2 weeks)
- There is no memory effect on LiIon, I can charge it without recharging before
- LiIon has a more linear discharge curve, I can use my pack between 12,3V (fully charge) and 8,4V (fully discharge) without fear of sudden voltage fall (and airplane crash...)

I use 5C discharge rate LiIons, but TX will last several hours with then, so 1C discharge is good enough. The brand of my cells is DLG.

We pay around US$6,00 each 1400mAh cell here. Brazil has a lot of taxes so I believe these cells will cost US$2,00 or less in other countries.

My Futaba TX has a diode in charger input, so it is not a good idea to plug a LiIon charger on the TX.

I remove the pack from TX and charge it in my Hobbico MKII charger, far from combistible materials like any other LiIon or LiPo cell.

[wildnloose]

I know a guy who has tested this using a tp 3cell/1320ma (older 8c) battery in his 10x and it powered it for 4hrs before it needed to be recharged. Also, it fits in his battery compartment without issue.

[Ib Jensen]

are you able to charge this through the transmitter? :confused:

I do charge it through the TX plug. I added a connector in the charging lead from the Multiplex charger so I can use the Li charger I got with the cells.

This system works great. With 4000 mah I can fly all day and if I forget to charge up overnight I don't wory about it. I just fly the next day and still have 1/2 the charge left.

Ib

[Geoff Akerlund]

So the PCB protects the pack when using the Multiplex wall charger? I'm thinking of doing the same to my evo

[Ib Jensen]

In theory it should, but not having had experience with it I use a Li charger that I got with the cells. I added an in line connector to the Multiplex charger wall wart so I can ise the Multiplex connector with either charger.

Ib

[Geoff Akerlund]

Thanks, I ordered a charger and a 2 cell 4800 pack (looks like batteryspace is selling them already joined now). How did you figure out which wires are positive/negative on the charging leads? Both the wires on the Multiplex charger are black, however one does have a white stripe on it.

[Ib Jensen]

The Li charger came with colored clips at the end. I measued the voltage in the pins of the Mpx plug before cutting. The only gripe I have with the setup is that you cant program the EVO for battery packs with more than 2000 mah capacity. Thi s means that when the EVO indicates its time to recharge, I still have half the battery left :)

Ib