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Discharging the battery in the DX8

How do you do it?

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Tony Read18/05/2012 09:54:39
404 forum posts
13 photos

Since I bought my DX8 I have found that I am only topping up the charge in the NiMh pack. Obviously this is not good for the health of the battery and it should really be discharged before charging.

With my other Tx sets I can discharge through the transmitters charge port to cycle the battery. Apart from the size of the DX8 port being different to all my others, I am concerned that it may not be possible on the DX8?

Is the only way to disconnect the battery? If so what sort of connector is required? I assume that by disconnecting the battery no data is lost.

Bob Cotsford18/05/2012 10:47:54
8261 forum posts
454 photos

You could always leave the transmitter switched on for a few hours.

I've not cycled transmitter batteries for donkeys years, not since they started to be fitted with NiMh rather than NiCads. Most knowledgable sources seem to say the NiMh don't suffer from memory effects.

Come to that, a lot of transmitters have a diode in the charge circuit which makes cycling difficult without removing the pack anyway.

Tony Read18/05/2012 11:10:55
404 forum posts
13 photos

Not sure about NiMh's. I was reading 'Current Affairs' in Q&EF and the author seemed to be saying that 'top up's' were a 'no-no'.

I have to say that I can never get a full charge being shown on the DX8, but I think this is a common problem.

NigelH18/05/2012 11:15:34
891 forum posts
1 photos

What about the inactivity alarm ? You'd need to keep responding to it or it would shut down.

Connect it to a bulb ?

Chris Bott - Moderator18/05/2012 11:23:44
6724 forum posts
1392 photos
1 articles

When using a NiMh in the DX8, my information is that the fully charged light will never come on, it is only associated with using a LiPo. I have read on another forum that it is entirely possible to damage the NiMh just by leaving it on charge too long, to me this is a poor design. Apart from the battery charger I think my DX8 is excellent.
Some people have added a plug and socket between battery and Tx so that they can take it out and use an external charger. This would work for a discharge too.

Alan Randall19/05/2012 20:46:16
446 forum posts
108 photos

Are you sure you need to keep topping up the Nimh pack up. In my experience those in the DX8 last for several weeks before you need to recharge.

Andrew Ray19/05/2012 22:53:47
760 forum posts
19 photos
Posted by Alan Randall on 19/05/2012 20:46:16:

Are you sure you need to keep topping up the Nimh pack up. In my experience those in the DX8 last for several weeks before you need to recharge.

It's good practice to go out with a fully charged battery as you start the day from a known point rather than a partially charged, half full, half empty battery. As the battery ages this will become more important.

The article referred to in Q&EFI is by Stephen Mettam, very knowledgeable and one time editor of EFI.

Some TX's like my JR PCM 9X cannot be discharged through the charging socket, (I've not tried it, but that is what the instructions tell me). Removing the battery to discharge is not usually a problem and cretainly not with the DX8 'cos I've done it. I think it is a JST connector.

I have also read that the bar graph on the DX8 will not show full status with a NiMh, (does it with a Lipo?) because it has to cater for the diffent voltages between NiMh and Lipo. The numerical voltage display is the only way to tell apparently.


Paul Marsh19/05/2012 22:59:52
3853 forum posts
1115 photos
On the DX8, you have to tell it what battery it's using, and it will alter it's alarms, accordingly.
Wolfiemac20/05/2012 08:32:24
10 forum posts
8 photos

I charge my batteries outside the TX on the DX8, when the TX first came out i could not get a spare battery that came with the little plug, I wanted a spare battery and also found the TX getting hot while charging, I also wanted to cycle the battery, so phoned BRC and Don said many people are cutting the lead off and fitting a new one, which is what i did.

you need to keep the little white connector that fits in the TX, so cut the battery wire and solder on a female futaba plug off an "old extension lead", you can now put any reciever pack inside the TX that has a male plug.

"so you end up having the white connector one and and a futaba female plug the other"

On the battery pack you cut the wire off, solder on the male plug you cut off the extension, you now have a working battery pack again.

Be careful cutting the off the wire on the battery, do one at a time so you dont short out the battery.

hope this helps

Alan Randall20/05/2012 14:10:29
446 forum posts
108 photos

Sounds like folk law to me. I would guess that during a normal days flying only a few folks fly so much that they take an appreciable amount out of the battery, that it then needs topping up immediately. Especially if you then start to worry about the need to cycle the battery because you are topping it up because you are not using anywhere like its full capacity in the first place.

Ben B20/05/2012 14:57:12
1421 forum posts
4 photos

If I do a good days flying with mine it takes up a fair amount of the juice in the battery but we're probably talking a good two to three hours solid flying and I tend to forget to switch it off until the alarm reminds me

I'm getting the HK lipo as soon as they've got some in stock....

Tony Read20/05/2012 19:46:29
404 forum posts
13 photos

I like Wolfies idea a lot and will give it a go unless I follow Ben and go Lipo. Ahh decisions, decisions smile.

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