Li-Po voltage regulator

[Teaker11]

Evening all
Sorry for so many questions, I have been out of the RC modeling for 25 years, so my learning curve is big right now. When I bought th WFT08 radio it came with a cable called Li Po Voltage regulator. I want to get recharable batteries for the transmitter. I know there are nicad, and lithion ion batteries. Do I install the li po in line with the Lithion Ion battertes to the transmitter, but if I buy nicad do I still need the the cable. I cant find anything in the instruction.
Thanks in advance for your help
Jim

[trout]

Jim,
That is a great question because I got one of those LiPo guards myself and never posted the question. Does it perform the same function as the LiPo guard sold by Caswell (minus some advanced features)? It goes to the receiver because the transmitter has its own low voltage alarm.
There is a charging port on the side of the transmitter, do I put NiCad batteries in and use my old Futaba charger? Inquiring minds want to know.

[Subculture]

Lithium ion batteries are slightly different to Lithium Polymer batteries.

They need a different charger, and also have a different cell cutoff point (2.5 volts instead of 3 volts). The latter point makes them better suited for use in a transmitter, as most low voltage alarms built into the transmitter are designed to sound at well below 9 volts. I use three Li-ion batteries in my Futaba FC16, these are batteries left over from redundant pocket PC's, although other sources could be old mobile phone batteries etc. I took them out of their casing, soldered them into a small pack with a balancing connector and a deans plug to hook them into the TX. That gives a small pack with about 1700maH capacity- enough to keep my FC16 going all day long. It has no problem with the increased voltage, although I'd advise caution doing this with other sets unless you know what you're doing.

You'll have a tough time finding Nicads these days, they've been phased out- cadmium is nasty stuff. NiMH is now the technology used in place of Nicad, with much larger energy density. Unfortunately NiMH cells tend to self discharge at very rapid rate, which means they go flat quickly, even when not in use. However there is a new generation of NiMH batteries developed by Sanyo called 'Eneloop' which are specced to retain most of their charge even after a year on the shelf.

I was sceptical until I tried them. I purchased some for a digital stills camera that used this type of battery, and can confirm that they live up to the hype.

So I'd recommend you get some of those for your transmitter.

[KevinMc]

What's the discharge curve on LiOn batteries like in comparison to NiMh? I've always updated my transmitters with 1600mAh (or so) NiMh packs on the argument that 1.)the working voltage range and low voltage alarm in the transmitter is designed to work with that type of chemistry, 2.) I can fit NiMh packs into the battery compartment, and 3.) if I need to I can use the wall-wart charger that was included with the transmitter to charge them up.

I'd never heard about the new "low self discharge" chemistry, how readily available are they?

[Subculture]

They don't drop off a cliff like lipos, although the curve is steeper than NiMh. The voltage monitoring works fine, as the alarm on my FC16 is set to go off at 8.5 volts, and I would have to go down to 7.5 volts to ruin my batteries, clearly I'd be in trouble with Lipos, unless I modified the alarm circuit in some way. I made up two packs, but haven't had to swap them out mid sail yet.

Regarding the low self discharge NiMh's. I got them from a seller that was advertising via Amazon (the UK site though). These were genuine Sanyo Eneloop AA size batteries, with 2000mAH capacity, which you might notice is a little lower than some NimH capacities out there. You can now get them in 2500mAH sizes, but the cycle life is lower. Personally I think 2AH capacity is enough for a transmitter anyway, unless your rig is particularly thirsty.

Hobbyking do some generic low self-discharge NiMH batteries. Haven't tried them, as they weren't released when I purchased the Sanyo's, but I've used their Lipos and they're excellent, and the user reviews for these batteries look extremely favourable, which is usually a good indicator.

http://www.hobbyking.com/hobbyking/store/__10456__Turnigy_AA_LSD_2200mah_Low_Self_Discharge_ready_to_use_.html

[He Who Shall Not Be Named]

Good stuff from our resident electron-chasers. Thanks, guys!

David,

[Teaker11]

Here is an update I bought Powerrex 2700 rechargable AA MH Batteries with the lipo adapter the transmitter reads 9v with out 10.7 thease were rather expensive batteries and the charger, Am I ok not useing it . droping to 9v is sending current somewhere so it would drain the batteries when not in use. Or is my theory wrong?
Thanks
Jim

[Subculture]

You don't need to use a lipo adapter with NiMh batteries. Just run the batteries straight to the TX power leads.

[trout]

I am confused and looking for clarification......
It is preferred to use NiMh batteries? (NiCads are history - I am feeling old)
LiPo will not work because of the voltage sensor in the TX and the voltage output? would LiFe work?

What transformer/Power Adapter do you use? Is there one that plugs directly into the TX or do I need to remove and add batteries to charge?

and What about the LiPo Guard included in the kit??? Anyone play with it?

[Subculture]

I never said Lipo won't work. But if you rely on a sounder to tell you your batteries are going down, you run the risk of ruining the pack, because lipos end up knackered if you run them down below 3 volts per cell, so unless your TX comes with an adjustable cut-off, I don't advise fitting Lipo.

LiFE batteries will work great in a transmitter. They're far less senstive to low voltage discharge, plus they come with the right cell voltage to give 9.6 volts (three cells). They also have a very long cycle life.

In a nutshell if you want a simple to maintain TX battery pack, I would get the NiMH pack. They can be charged simply using a normal trickle charger, and will work perfectly with the built in voltage monitor.

I charge my batteries externally, becuase Lion batteries need to be balanced.

[KevinMc]

I agree with Andy on this - if you want simple stick with NiMhs for your Tx. Personally I don't like having to hack my transmitter to fit a different pack or leave empty space that could have been filled with a better shaped battery pack for the available envelope. You can always find a NiMh pack that will drop right in 'cause that's the form factor 95% of all transmitters were designed to take. I know that in many respects NiMh chemistry is considered "old school", but a smart modeler uses the right tool for the job and in my view that includes giving due consideration to battery chemistry selection for the various applications we have. I'm a big advocate of LiPos for driving subs, but all my transmitter save for one run on NiMhs, and the only one that's not on NiMh's was designed specifically to use LiOn. YMMV

[trout]

Kevin, Thanks for your input. Have you seen the LiPo guard that comes with the wFly 8ch tx/rx?

[KevinMc]

I haven't. But I've had my WFT-08 for a long time now, perhaps this is something that's since been added to it. (And to be specific, I have to assume by LiPo Guard you mean that the WFT-08 is including some kind of LiPo regulator. LiPo Guard is one of my products and is not designed for use with a transmitter.)

[trout]

Kevin,
You are right it is called a LiPo Voltage regulator.
Here is what it looks like:

Thoughts?

[KevinMc]

Well, that definitely wasn't included in my transmitter, but then again I've had mine for quite some time now and even if it hadn't been there I wouldn't use it anyways. It must be some kind of series voltage drop device though, otherwise it would likely drain the battery 'till it was flat.