A few questions!

[RichN]

Hi,

I've just bought some GP1300 Nimh cells for my KO Vantage but I don't know where I can find a suitable charger to plug into the transmitter to charge them. Anyone know where I can get one? I've heard some people use an old Riko one but I'm not sure if they're NiCd only? Would I be able to charge them off a general AA charger like a uniross one? Failing that I'm thinking I could connect them all together and charge them off my CDC but this would be a bit of a pain to do regularly.

Secondly, I've got some new EP cells which I've made up as 4 cell packs. The first pack charged fine, but the second doesn't seem to want to charge as it says the battery voltage is too low. Is there any way I can get them to charge? I'd thought about briefly connecting a 6 cell pack to them because as they're connected in series wouldn't this increase the voltage of the new cells? I'm not sure if it would damage them though.

I've been charging them at 4.5A and I think it's 6mV / 20mV (definately 20mV but unsure if it was 6), is this ok? I'm after punch more than duration.

Thanks very much, great site you've got going!

Edit - Just seen Keven Bissel's post on the CDC issue, so I'll try some of his suggestions :)

[kevin bissell]

Hi Richard

I hope you sorted out your 4 cell packs.

I also use the CDC to charge my Transmitter AA cells. Buy yourself a lead and plug (available from hobby stores) or make up a lead yourself (the plugs are available from the likes of Maplin) ensuring you get the polarity correct.

Settings on the CDC are
No. of cells - 8
Capacity - 1300mAh
Charge current - 0.7A (you could go to 1C but why bother)
Peak 5mV/Cell

I've been doing this with a CDC charger for years on a range of Transmitters - KO Esprit II, Sanwa Gemeni II and Futaba 3CVS and never experienced any problems.

Hope this helps
Kev.

[RichN]

Cheers, an ac wall charger just seems much easier lol.

With the cells, I tried charging them as a 3 cell pack and put about 200mah in them which is did fine. Tried to charge them again and same problem so I put them on the smart tray. No light on one of the cells :rolleyes:. Tried charging that cell on its own and it refused to do it. Duff cell by the looks of it! Brand new EP4200 as well lol.

I've got a spare new ep4600 so I'll have to put that in for now and get some new cells bought. Tried the 4600 pack out at racing tonight and it was much better than my old cells :)

I've only ever used a novak millenium pro which I had about 5 years ago when I last raced lol, so still getting used to the CDC.

[kevin bissell]

Richard

What put me off the AC wall charger option was that I didn't know if I could get one that would cut off once the cells were fully charged. The AC chargers I have experienced simply chuck out a continuous low current. With NiCad this isn't a problem because they will accept a continuous trickle charge even when they're fully charged. On the other hand, from what I've read, with NiMH a continuous trickle charge is not recommended (overcharging the cells can damage them).

By using the CDC, it will charge the cells then stop when they're full... job done. You can charge the previous day, 1300 mAh should be more than enough for a full meeting. I bought a set of eight 2100 mAh cells from Vapextech and I can easily get three meetings out of a single charge.

As for mixing a single 4600 cell in with three 4200s... be very careful. The charger may not see the peak voltage and stop charging. Think about it, the 4200s are all full and peak but one cell is not yet fully charged so doesn't. There is a danger of overcharging the 4200s and the consequences of overcharging are documented all over this forum... there is a risk of one of them going bang.

My advice... don't use this pack until you've replaced the faulty 4200 cell with another identical cell.

Hope this helps
Kev.

[Skiddins]

Richard

What put me off the AC wall charger option was that I didn't know if I could get one that would cut off once the cells were fully charged. The AC chargers I have experienced simply chuck out a continuous low current. With NiCad this isn't a problem because they will accept a continuous trickle charge even when they're fully charged. On the other hand, from what I've read, with NiMH a continuous trickle charge is not recommended (overcharging the cells can damage them).

By using the CDC, it will charge the cells then stop when they're full... job done. You can charge the previous day, 1300 mAh should be more than enough for a full meeting. I bought a set of eight 2100 mAh cells from Vapextech and I can easily get three meetings out of a single charge.

As for mixing a single 4600 cell in with three 4200s... be very careful. The charger may not see the peak voltage and stop charging. Think about it, the 4200s are all full and peak but one cell is not yet fully charged so doesn't. There is a danger of overcharging the 4200s and the consequences of overcharging are documented all over this forum... there is a risk of one of them going bang.

My advice... don't use this pack until you've replaced the faulty 4200 cell with another identical cell.

Hope this helps
Kev.

The AC wall chargers current is usually so low (70mA for mine) that leaving it on a bit longer than you should is OK, the cells never get warm etc.

I have a pack of 2300 AA cells fitted and from empty they would take over 32hrs (if charging was 100% efficient which it never is, so lets say 40hrs) to charge.

Wall chargers are more convenient, more gentle on the cells, can never be connected the wrong way around etc.

Skiddins

[RichN]

Cheers for the info guys. I've since realised that putting the 4600 cell in could be a problem. I'm going to order another 4200 cell if I can't get the current one to charge. I'll see if I can get someone else to charge it to get the voltage up.

Kevin, you mentioned buying some connections etc to connect up the 8 aa's; have you got a pic of what you use?

I'd be tempted to use a wall charger for ease, but can't find/don't know of a suitable one.

I was hoping the 1300s would last more than one meeting :eek:. Im just using some energizers for the time being and I've used them for 2 meetings and they've stil got loads of life in them.

[rob_g]

Hi Guys,

I also have some 2100 batts for my tx whats the mv cut off for these please

Thanks
Rob

[kevin bissell]

Richard

Here's what I mean about a charger lead for use with your radio Tx and CDC.



If Skiddins says that a normal mains wall charger is OK at 70 or so mA then go for one of those if its more convenient. The advantages of having a charging lead for your race battery charger are:

1. Quicker charging.
2. If your Tx battery goes low during a meeting you can bang a quick 20 minute charge in at 1A which should see you through.

Rob
I always use 5mV per cell even for AA cells. I do this for both my safety and the safety of my wallet. With all this talk of cells failing when overcharged I don't want to risk wiping out a £300 tranny... :'(

I have been charging my Tx batteries for at least four years using this method and I have never experienced any problems.

Cheers
Kev.

[RichN]

Ah so you leave the cells in the transmitter and then connect the plug to the transmitter and the other 2 leads to the CDC?

With regards to the dodgy cell, will it most likely be a dud? I'll have to see if someone else can try to charge it.

Thanks for all the help!