TX batteries

[spar]

Anyone have experience with rechargeable batteries in the stock SC transmitter? Any issues with NiMH and the transmitter's low battery alert?

[flydiver]

I use either Energizer 2500 or Duracell 2500 NiMh. Both work fine, last for a long time, and I get a "normal" low battery warning signal. I don't continue to fly after low battery as the discharge curve on NiMh is rapid. I have no idea how much longer it might go.

I've used lower MAh rechargeables too without problems. If you check the rechargeable "commercial" packs that come with a lot of TX you'll find that they are generally Sanyo NiCads or similar, often pretty low MAh (like 600). Any rechargeable is just that, rechargeable. No magic involved.

fly

[hack73]

After hearing others switching to AA 2500mAh NiMH rechargable batteries, I tried it out. It was easy because I had already had a bunch of these batteries & a charger that I used for my wireless keyboards & mice, etc. I can't remember the last time I had to charge them. Last a long time between charges. Definitely, worth the investment and you will not regret it.

[cjg]

I added a charging plug to my stock SC transmitter and put energizer 2500mah NIMH. Works fine.

[spar]

cjg said:

I added a charging plug to my stock SC transmitter and put energizer 2500mah NIMH. Works fine.

Do you use one of the SC chargers for that set up?

[retiredbri]

Hi
Searched the forum for TX rechargeable batteries and found this one.
I used 2100maH NiMH batteries in the TX and made a temporary connection so I could charge them from my Hobbico PKZ1519 charger (5 - 10 cell, selectable .5A to 1.8A charge rate, peak detector) and set it to 1 amp. This was C/20 so thought all would be fine. I left the battery cover off.
The charge took 2hours before the peak detector cut out (as expected).
BUT the outer of the cells were hot and the middle group were too hot to touch.
This can't be good for them.

Anyone else had problems like this?

For now, I'll charge them with a normal 4 cell charger.
Retiredbri

[duck9191]

^^ the cells could be way out of balance. try to discharge it some and keep an eye on it when you recharge them, keep checking the temperature.

[flydiver]

TX batteries (and this means most home AA) are low discharge type and will do better with a slow charge. Many individual home chargers have pulse charging or other mechanism to keep the temp from getting too high. I doubt the PZ charger does this since it's designed for fast charging low resistance batteries.
NiMh do not like heat. Warm is normal. If you can't hold it in your hand it's too hot. In that case, slow down, or try another charger.

[retiredbri]

Thanks for the replies.

Because these were new cells of the type that do not loose their charge while on the shelf (Vapex), I thought the cells would be balanced. Also, that the centre ones were hotter because they were in the middle of the "sandwich".
The manufacturer's data says:

......you can still use a standard NiMH charger to charge them up again (maximum charge current 2000mA)

Charge Current & Approx charge time from empty battery:
100mA 27 hours, 250mA 12 hours, 500mA 5.4 hours, 1000mA 2.7 hours, 1200mA 1.8 hours
Max discharge current 6300mA at ambient temperature 20 .. 50°C

Because I like the idea of not taking them out of the TX, I'll try them out at 0.5 amp charge current next time and keep checking the temperature.

Regards
Retiredbri

[retiredbri]

Just had a chance to measure the current drawn by the TX. It is 125mA with the antenna extended (the antenna extended puts a proper load on the RF circuits) and 114mA with the antenna retracted.

With 2100mAH cells, this should give over 15 hours of use (or overnight if I leave it switched on!)

Retiredbri

[flydiver]

My JR charger is 65mA for the stock (600mAh) pack. That's a C/10 charge rate-takes ~15 hours to charge.
I put a 2500 NiMh pack in there. Took 3 days to charge with the stock charger now.

So I get a used 400mA wall wart, reversed polarity (JR are reverse, don't do this if you don't know what you are doing), and now use that in a reasonable time frame. Works fine, only get warm packs.

I can also hook it up via an adapter to my Great Planes NiXX charger and use 500/1.2/2.5A rates. They all work fine. Nothing gets hot.

So, I suspect something is not right with your system. Not sure what though.

I had a buddy put some 2600 cells in a small 4-cell AA charger. Got hot enough to wrinkle the skins. The specs on the charger would not lead me to think this would happen. Hard to figure what is wrong.

[retiredbri]

I'll check each cell voltage when next charging.
Regards
Retiredbri