Anyone upgraded their DX7 Battery?

[GizmoB73]

I seem to be spending a lot of time recharging my DX7 lately and was thinking about upgrading the battery from 1500mAh to something that will last longer.

I have seen that some people have done LiPo upgrades which I guess is an option. They also appear to be still charging them in the TX which seems wrong to me. I would expect any internal charging circuit to be geared towards NiMH rather than LiPo. Is this correct?

Assuming it is correct and I want to stick with internal charging, has anyone found any good NiMH packs that fit at a reasonable price?

I am thinking I could probably buy 8 x AA NiMh 2500mAh cells and solder a pack together but it gets messy and I am a bit lazy, so are there any already done that don't have a ridiculous price tag?

Any other ideas?

Thanks

Gary

[Ade_Law]

there isnt an internal charging circuit so you have to use "a charger" externally, which in this instance is a good thing as you can stick a lipo in and charge it with a lipo charger.

personally i charge my battery out of the tx, theres an 800ma fuse in the tx which limits the speed you can charge at.

Ade

[scallybert]

I have seen that some people have done LiPo upgrades which I guess is an option.

There are (IIRC) dire warnings against doing this on the Horizon web-site.

Says the Tx is designed for NiMH voltages, and LiPo voltages will upset its regulation circuitry.

Ade says there's an 800mA fuse in the Tx. I'm not sure on this. I blew the fuse in mine (plugged in the wrong charger with reversed polarity - oops...), and this was a 3A fuse. I didn't see another fuse, and I would presumably have blown an aditional 800mA chargig fuse too/instead.

[Unless it actually said .8A rather than 3A on it. It did look like there was a '.', but I'm sure it was a '3'. Seems unlikely.]

[Toolman]

I bought a Flight power pack for my DX7 but haven't got round to fitting it yet & have now got a DSX9. For some reason the std battery in this seems to last longer. What I did conclude though from post by Mac_man and others was if you switch to lipos you need to drop the voltage a bit.

The way I was going to do this was using a tail servo voltage drop lead. I think that CSM do one that drops 1.2V. (I think realraptors sells themfor instance) What you would need to do though is have some means of charging the battery direct ie NOT through the drop diode. So you would have to make up your own leads.

Tim.

[GizmoB73]

From what I have read on the net, I was of the belief that it was about a 3 or 4 amp fuse rather than 800ma.

I am a little surprised to hear there is no charging circuit in the TX but I guess it makes sense.

As for not being set up for LiPo's, I would be interested to hear what Horizon have to say about that. It does seem a bit odd to me as the TX battery voltage scale does seem to be perfectly calibrated for a LiPo. You never reach max on a fully charged NiMH battery, but it is apparently spot on with a charged LiPo.

I think I would personally be quite happ with a NiMH solution as there is plenty of capacity available in NiMH cells anyway. I don't think I need any more than 2500mAh.

All good stuff so far, so can anyone recommend any packs that they have used to upgrade, or that look like a good option?

Thanks all

Gary.

[robgt]

You want one of these.

Cheers,
Rob

[Andy from Sandy]

At my club one battery in DX7 was not holding its charge and has been returned and another exploded whilst being charged. These were the standard packs supplied with the set and charged with a JR charging lead.

[SRH990]

I've been using the Flightpower lipo TX pack in my 9XII for a while now with no problems and even though it's only a 1500mAh pack it lasts much longer than the 1800mAh nimh pack I had in before. The problem with nimhs is the high self discharge rate on most cells whereas lipos have a very low self discharge rate.

One question, we are all happy to charge our bluetooth headsets, MP3 players, mobile phones etc. with the lipo batteries still fitted (you can't take most of them out anyway!) so why take the lipo batteries out of a transmitter to charge them. If you use a dedicated lipo charger set correctly then surely it's as safe

[raptorheli2]

check out what i done a few months ago....

http://www.rcheliaddict.co.uk/showthread.php?t=9251

i have not charged the tx since the day i put this battery in....superb upgrade.

btw you can get access to the hidden menu and change the voltage warning beep if you want. i set mine to 10v i think as that was the max it would go. i wouldn't run it that low myself but there is some movement on it.

cheers

[Made2Fade]

You want one of these.

Cheers,
Rob

I got the 2400mah version of the vapextech pack and it lasts forever. I never seem to charge my DX7 these days. I use their rx packs on my rappys and there cracking packs that last forever also.
cheers
Lee

[Smoothound]

I use a 2600mAh 3s Lipo in mine now as I grew bored of the constant trickle discharge of my 2 NiMh packs. I've had the lipo for ages and only charged it twice.

I have to say I never charge it in situ as it has a warning with it not to use until 5mins after the charge has finished. I think it has some sort of balancer voltage dropper circuit built in as the 3s fully charged voltage of 12.6v is thought to be a bit high for most Tx's to run on.

[moyesboy]

how much are you using this tx with the original 1500 pack?
In my experience it lasts for ages and ages.
however being nimh it does self discharge, so if you leave it a week it needs topping up again before the flying session.
My dx7 lasts much much better then my 7CAP, even after I upgraded the 7CAP battery from the 700maH poxy one that was in it.

If you want to fit an alternative battery then consider making one from eneloop, or instant nimh. AA cells up to 2000mAh, but come fully charged and do not self-discharge (85% left after 12 months). I've not seen these with solder tags or in made up RC packs yet but they seem the way to go.
http://www.component-shop.co.uk/html/instant.html

Surely you are not flying anywhere near 1500mah out of the tx, it must be jsut going flat (self discharge) between flying sessions.

Self discharge rather than increaed performance was why I changed my nitro helis to lipo rx power. Then they sare ready to go and fly whenever with no planning. My tx I charge regularly becuase I am always hoping to get a flight with my 450 on week days.

[handthrottle]

Robgt told me about the vapextech batteries and have them for both my transmitters....they last for ever....and fairly cheap!!
TC

[GizmoB73]

You want one of these.

Cheers,
Rob

That looks perfect.

Good to see what is being done with the LiPo's too, but I am happy to stick with the NiMH I think. I will add one of these to my list.

[scallybert]

One question, we are all happy to charge our bluetooth headsets, MP3 players, mobile phones etc. with the lipo batteries still fitted (you can't take most of them out anyway!) so why take the lipo batteries out of a transmitter to charge them. If you use a dedicated lipo charger set correctly then surely it's as safe

It's all about balance...

Mobile phone, PDA, etc LiPos are sinlge cells, 3.6V.

So, there's just one cell to charge, and it can be charged through the one pair of leads without any balance issues.

If you have a 7.2V, etc, LiPo, it has 2 or more cells in parallel. These really ought to be balanced. (Otherwise, one can end up over charged/discharged with bad effects.)

To balance the cells you need separate connections to each cell. Hence the separate charging connector.

Personally (ie I might be talking crap...), I'm sceptical about any LiPo charger that doesn't balance the cells. Though I guess it's possible to use one if you're very careful.

[The problem is that charging a 2S, 3S etc through the pair of power leads means all the cells get the same charging current, and receive the same charge.

If one cell has a lower capacity (manufacturing tolerances) than others, or one starts off more charged than the others, either this cell gets overcharged, or the rest get under charged.

Since the charger is only seeing the total voltage (adding up each cell voltage), it can't tell this. The best it can do is stop at a certain voltage, or when it's put a certain charge in.

Balancing is much safer IMHO.]