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Using LiPo's in Spektrum Transmitters

colorex

Rotor Riot!
Mentor
#1
Ok, so my friend Nick asked me for a solution. He uses a DX5e to fly, but he wants a longer lasting battery for it. I looked around and found this one for a DX8 ($17):

19481.jpg

It is supposedly intelligent with LVC built in, but I don't know if it will fit in a DX5e.

Is it worth the money? Will it fit? Will it work?
 

pgerts

Old age member
Mentor
#3
The battery is really good - dont think that i have to charge more than a few times a year.
The battery is for the intelligent charger built in the DX8 and not for the DX5.
Try a receiver pack of low self discharge NiMh in the DX5. It has to be modified to get place for the pack but it is not impossible.
I have not tried the http://www.hobbyking.com/hobbyking/...2200mah_Low_Self_Discharge_ready_to_use_.html but think they can do the job.
 

colorex

Rotor Riot!
Mentor
#4
So the battery shown is a no-no.

So what's the best thing possible? As in longest use time without charging for a DX5e?

The NiMh AA batteries look quite good, I'll show those to my friend.
 

Ak Flyer

Fly the wings off
Mentor
#5
I never used rechargable batteries in my DX5e but the regular alkaline AA's last a really long time. Never seemed worth it to do anything else.
 
#7
I use a 3S LIPO in my DX7 (2650mAh) but then it also uses a 8cell NIMH as stock...

No worries and I recharge 1 every "cannot remember when I did it last time" so it lasts months

//UndCon
 
#8
My friend uses rechargeable, he says he has to recharge them every 2-4 hours of use.
That seems a bit strange. Almost makes me think perhaps the ones he's using might just be junk, too old, or something.
I use some energizer rechargeable batteries in my DX6i and they last multiple weekends.
 

fred0000

Senior Member
#9
rechargeables wont last nearly as long as regular alkalines.

rechargables are rated 1.2v where as the regular ones are 1.5v for that radio I would honestly just stock up on some decent AA's and keep some on hand at the field.

another thought i've had but i've never done it, for radios that use 4xAA's is to just get a cheap UBEC that operates at 5v and wire that in, then you could use pretty well any battery you want to make fit. (you would have to disconect the battery everytime you were done, the power switch wont shut the BEC off)
 
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colorex

Rotor Riot!
Mentor
#10
another thought i've had but i've never done it, for radios that use 4xAA's is to just get a cheap UBEC that operates at 5v and wire that in, then you could use pretty well any battery you want to make fit. (you would have to disconect the battery everytime you were done, the power switch wont shut the BEC off)
That could be a solution, it would last forever with a single charge, but you'd have to add a switch that cut's the battery power.
 

colorex

Rotor Riot!
Mentor
#11
I use a 3S LIPO in my DX7 (2650mAh) but then it also uses a 8cell NIMH as stock...
I use the exact same battery for my Tx, but it's also 8cell - NiMH. I haven't charged the battery fully as I'm afraid this would overheat something. Should I worry? I mean, what's the voltage difference between a fully charged 3S LiPo and a fully charged 8S NiMH?
 

fred0000

Senior Member
#12
I use a fully charged 3s lipo in my 9x, was using old 900mah 20c packs at first but now have a propper 2650mah unit, best thing i've done so far was convert my radio's to lipos, some people only do a storage mode charge to keep the voltage down, or you could get a 3s life pack if your concerned.
 
#13
You take a risk using a fully charged LIPO as it exceeds 12Volts.

To avoid this add a couple of diodes to drop the voltage to 11.9 (and sometimes get correct reading)

I only use a 2S in my Turnigy (ER9X)
 

colorex

Rotor Riot!
Mentor
#14
You take a risk using a fully charged LIPO as it exceeds 12Volts.

To avoid this add a couple of diodes to drop the voltage to 11.9 (and sometimes get correct reading)

I only use a 2S in my Turnigy (ER9X)
My voltmeter has a dead battery, so I can't determine exactly the right voltage. Is 11.9 the maximum NiMH battery voltage limit?
 
#15
No but in some radios they do not show proper voltage when using LIPO so you have to drop below 12V for voltage meter to show correct values
There is no guarantee things still work when you use more than 12V so it is a good thing using diodes to protect the radio

//UndCon
 

colorex

Rotor Riot!
Mentor
#16
No but in some radios they do not show proper voltage when using LIPO so you have to drop below 12V for voltage meter to show correct values
There is no guarantee things still work when you use more than 12V so it is a good thing using diodes to protect the radio

//UndCon
Do you happen to know what diode values one can use to regulate the voltage? Or do I just keep charging until 11.9 - 12 V?
 
#17
Colorex - as you can read swedish:

SMFF

Others can look at the images ;)

Diodes used are 1N5400 50V 3A

Solder 2 in parallel to have a backup if 1 should fail.
1 or 2 diodes in series might be needed to drop the voltage on certain radios.


Personally I find it easy to abort the charge at 11.9/12V
//UndCon
 

colorex

Rotor Riot!
Mentor
#19
Thanks! That's a very good tutorial!

For those who can't read Swedish, it says "solder the diodes like in the picture"

@Rcjim11 What is considered a "standard" diode?
 

fred0000

Senior Member
#20
for the cost of it, and how simple it is I may have to get some diodes and do this, in the meantime I will still continue to use the lipo in my radio fully charged since its been fine for the past few months, I would love for the voltage reading to be accurate.
the diodes can be found on eBay for $3.50 for 50 of them i'm going to look localy first as this isn't an urgent issue for me.

(hey Andre, I had a thought about the BEC powered radio, we could take the radio apart and jump the existing power switch so it's on all the time, then use the factory switch to turn the BEC on and off, it would effectivly turn the radio on and off aswell)