CHARGING PROBLEMS?

[felix]

i have a swallow charger and jaycar 2000mah nimh batteries for my tx.my tx doesn't have a charging jack so i pull them out and charge them in a battery case.my problem is that the batteries are not taking full charge/discharge.thinking it is because the battery pack is wired in series and somehow the charger is reading the resistance as a full charge? is it possible to wire a pack so the batteries are in parrellel without frying something?

i have checked all the cells for voltage before and after load,also checked the resistance of all the cells with a multimeter and they all seem spot on.

[Pij]

Felix, I wonder whether it would be worth doing a discharge-charge cycle on each battery INDIVIDUALLY with your Swallow, and noting the discharge capacity and charge capacity of each one from the Swallow's data? First, you should give each cell a number or letter, and prepare a page to write all the data you get for each cell.

You might not get the exact discharge capacity the first time you do this, as one or more cells may not have been properly charged previously. But if the first time shows one or more cells has a lower discharge capacity, that could be your first but of good info.

The second time you do the discharge-charge cycle, hopefully each cell will perform close to the others.

Leaving unmatched cells always in a pack together can have cumulative issues.

I learned a bit about these things because I've been flying electrics, at first exclusively with NiMH packs.

But I have a question of my own:

My Duck is my first glider, so my first experience with "Receiver Batteries". How do others check the completeness of their charge, or the condition of their batteries? I've been charging my Rx battery from my JR charger, which can top up the Tx and Rx battery simultaneously. Should I be using my Swallow, to get the same data I was telling Felix about?

[thevon]

Felix, I've never had success with cheap NimH's of any sort! Not sure if I'm on the mark but you may find it's the batteries, not the charging. I had all sorts of probs with a digicam, had to take it to camera shop, bought more batteries - same result. Camera shop insisted I should use Sanyos, I thought they were crapping on but finally bought some Sanyos and it was perfect. Never used anything else since. Plain Sanyos are great, and Eneloops are awesome.

Pij, not sure if I'm missing something but the Swallow is the thing to use for all batteries, RX or Tx. You need the delta peak charge function which the Swallow has. The Tx wall charger doesn't have that.

I also have one of those little Rx battery testers, with 5 tiny LED lights in a strip - got it for less than $10 on Ebay, and in the field I occasionally plug it in to check the charge.

[sean]

Hey Pij, I check the voltage of my rx pack by briefly putting in on disharge using the Swallow. This will give you the voltage of the pack under load. I usually discharge at 0.2 - 0.3A to get a reading, not sure if that is the ideal amperage but it seems to give an accurate reading. I don't take any chances - less than 1.2V per cell and it goes back on charge.

I've also had bad experiences with cheap nimhs, but have had good luck with Sanyos and Panasonics.

[Pij]

Thanks Andrew and Sean. I was relying on the trickle-charge system of the wall charger to ensure charge without overcharge. I've always done my Tx that way, overnight, before flying. But with my electric planes, the high-discharge-rate batteries needed the good treatment that the Swallow gives them with its peak-detection system. My impression was that if they included the wall-charger with a JR Tx pack, including Rx battery, then it should be OK to do the Rx battery the same way.

I suppose that was a bit silly, when I have the Swallow on hand. But it sure was convenient to have the Tx and Rx battery both charging from the little JR wall charger.

Yesterday I even made up a lead to charge our rechargable vacuum cleaner off my Swallow, because I didn't think the trickle-charger was doing a perfect job. Looks like I'd better look after my Rx battery properly, too.

[drcuzo]

Felix
I also have a swallow charger. It consistently stops charging soon after I start charging NiMH battery packs. I have found that if I immediately start the charge cycle again I get a full charge. This may be a bug in the chargers programming. I have not had a problem with overcharging doing this over the last 12 months. I would suggest not trying to parallel charge cells as the charger is designed for series charging. The charge current will increase in proportion to the number of parallel cells and you could cook the charger.
Steve
PS: I agree with Andrew and will only use eneloops in future

[felix]

thanks all for the advice gives me a few ideas.if all else fails where can i get these sanyos cheap around brisbane?
one other thing is charging lipoly batteries,i am building myself a 30's era racer parkflyer and have a venom brand 2c lipo, 30amp ESC and brushless motor/gearbox combo .....do i need a balancer and what are the things i need to know about using these things?

god i hate electrics!

[Pij]

I wondered, Felix, if it might be worthwhile to change your Tx to take a ready-made Tx battery pack, instead of those loose cells? That way, the batteries should be matched to each other (you understand what happens if you have one weak cell in a set, don't you?) and they are all connected together ready for charging. Can go to NiCd too, if you trust those better.

[thevon]

Felix, do you have a Tx with 8 cells, with 4 stacked on top of 4 (like a normal Hitec, JR etc)? If so, Oz-RC at Geebung recently had a properly made-up Eneloop Tx pack there, for only $50 as someone had ordered it but didn't turn up.

[sean]

I recently bought Eneloops from here:
www.ozbatteries.com.au/eneloop-nimh.htm

Good prices!

[felix]

pij changing to a ready made pack is not an option on my tx unfortunately (cheap and uncheerful tx lol).as for the dead cell i have a an idea.i load tested each cell and found one which was at a much lower charge then the rest.i have since cycled that one and now it has recovered.
thevon my cells are 8 in a row.pity $50 is very reasonable!
thanks for the link sean,if i continue to have troubles with these i will definately get myself some (just spent another $250 for gear for a parkflyer and other supplies so have to lay low for awhile lest the better half finds out ).

just bought myself a single cell holder so plan is now to cycle each cell individually a couple of times and then see how they charge as a pack.cheers for the advice guys