Discussion Which batteries and why? How about LiFePO4 for DLG?

[Fly2High]

Originally Posted by tai626

Is the charging rate important for DLG?

If it is, this lipo is a good candidate:
http://www.allerc.com/product_info.p...oducts_id=4503

2s 7.4v 450mAh 29g and it can be charged at 5c or over 2 amperes!!!

The only downside to this battery is that it weighs a bit much. Since you need to add a voltage regulator and the average plane like a 25-30gr battery, it already weighs 29. It might be just a bit too much but if you have the room to shift it, it could work.

[tai626]

AFAIK, there are some Rec/servos combo to avoid regulator: Hitec electron/neutron 6 + dymond d47, for example.
How do you charge NiMH at field?

[Fly2High]

Originally Posted by tai626

AFAIK, there are some Rec/servos combo to avoid regulator: Hitec electron/neutron 6 + dymond d47, for example.
How do you charge NiMH at field?

I have been flying Super Gees and a LightHawk. Both easily allow a pyramid battery pack to be removed easily.

Actually, I never remove them though. I have a switchjack and put them on the charger between tasks and they are always up to snuff.

[kcaldwel]

NiMh don't seem to work well for me. They are always dead when I want to go flying (high self discharge rate). They don't seem to like the way I use them, because the capacity seems to disappear within 9 months. Except for the new nano particle NiMh which I have been using in my transmitter, which seem great. Unfortunately I hadn't found in less than AA size until just now, but even AAA is too big:

http://www.greenbatteries.com/hybrionimhaa.html

Charging rate isn't a big deal for me in a DLG. I charge my LiPos at very low rates because I'm not in a rush anyway, and I hope it avoids the thermal run-away issue. I've been using the eTec 450mAh liPo, with a switching regulator, and that gives me over 500 mAh of usable capacity for 30 grams total.

That other LiFePo4 battery you found, Tai, looks to have about the capacity of the Tenergy ones I tried before. Not enough for the weight, and the Tenergy ones are much cheaper.

If the new NiMh batteries are available somewhere in smaller than AAA size I'd switch to them. I didn't even charge them for the first outing this year after not flying for months over winter, and they had lots of charge. And they are now in their 3rd year, and still working well.

Kevin

[Fly2High]

For me charging small NiMH is no problem. I have an old Alpha 4 that can c/10 charge at 1 mAh. Nothing today can go so low. As for self discharging, I usually charge my stuff up the night before. Since I have 4 ports, I charge my Tx and 3 Rx batteries all at once. Comes morning, I am ready to fly till my arm falls off!

I may not do LiPOs but I do love my Alpha 4 , especially for the small batteries we use in DLGs.

[tai626]

Fly2High:
Do you need check them underload at field?

Kevin:
I did a little search and these RCR123a LiFePO4 might be manufacture by same company, believe or not: www.dlgbattery.com (DLG! coincidency? :-)
I will send a mail to K2 and ask for some extra information, charging and discharging rate, for exemple, before I bite the bullet. The "fast" charger they have is only 0.5C!
and the discharge rate is around 1C or 500mA, really marginal if you have 2.4 receiver and 4 digital servos.

[John255]

[quote=kcaldwel]NiMh don't seem to work well for me. They are always dead when I want to go flying (high self discharge rate).

You can solve self-discharge problems using cheap lamp timer set to come on every night at midnight for one hour. The timer can switch on a wall-wart DC supply with modified to output to charge your cells at 1/10C once a day while in storage.

Since I don't do Rx charging on any of my gliders I had to come up with a way to make the Tx's always ready to go also. I've been doing the timer method this on my Tx's for more than 4 years with no so called "memory " problem.

We had a good thread going last summer on couple cheap ways to slow charge and condition small packs using wal-wart DC supplies. I started the thread with the light dimmer method, and Frans Ball came in with a resistor method on post #31 page 3.
http://www.rcgroups.com/forums/showthread.php?t=1016948
Regards,
John255

[Fly2High]

Originally Posted by tai626

Fly2High:
Do you need check them underload at field?

Kevin:
I did a little search and these RCR123a LiFePO4 might be manufacture by same company, believe or not: www.dlgbattery.com (DLG! coincidency? :-)
I will send a mail to K2 and ask for some extra information, charging and discharging rate, for exemple, before I bite the bullet. The "fast" charger they have is only 0.5C!
and the discharge rate is around 1C or 500mAh, really marginal if you have 2.4 receiver and 4 digital servos.

I do not recall ever doing so but the Alpha does have a loaded (1A) and unloaded voltage meter built in and I have looked at them in there and all seems fine.

I typically fly with Aradhana's 250mAh or the GP for about 45min - 1 hour using 3 analog (2-D60, 1-D4.7) and a Jr 285 digital. Typically I am down about 2/3 to 3/4 at most. sometimes less but this is just a guess. I haven't really looked at it in some time. I would need to discharge it on the Alpha to know how much is put back into them which I tend not to do at the field and once they are formed.

[ROOSWH]

I just recently started using a Sirius Charge Pro Series. Not the Plus charger which is for larger receiver Packs. If I decide to go flying I can usually top off all of my several DLG 250mah NiMh packs and my transmitter in less than a 1/2 hr provided they have been been charged some time in the last week or so. It's a Pulse type charger which can put a fast charge safely into your pack and you can just leave it on if you want to, but I always remove my batteries as soon as I notice the blinking ligh t charge indicator. IT's really a great plug in and forget it field charger. It charges both Transmitter and receiver at the same time. They are a bit expensive so if interested look for a used one here on RC Groups. I think I paid $80 used.

After the regular charge it matains the battery with a current pulse every once in a while. I decided to get mine when I saw a bunch of the fliers at the DLG contests using them. I figured I'd use it as a back up to my well worn, and loved TRC pulse charger. But I find it so easy to use that unless I want a capacity read out I prefer it over the TRC.

BTW the receiver charge rate switch only changes the cut off profile not the charge rate, which is fixed at 500ma. The switch really is an approximate value so if set on, say "250mah" you can still charge that 180 or 300+ pack there.

walt

PS 72mhz receiver + 4 D47 servos in 60" DLG use only about 80 mah of capacity out of my 250 mha packs , give or take 15%.

[tai626]

John:
As Kevin states, using Sanyo Eneloop, ultra low self discharge, solves the NiMH in Tx. But it is not available smaller than AAA.
Charging C/10 one hour a day makes NiMH ready to fly anytime but what to do at field? It wouldn't last all day long. The solution maybe multiple pack and change? Or fast charge between task?

[G_T]

Always a good idea to have a spare packs handy for receiver and transmitter, just in case.

When at a contest just leave the plane on a Sirius charger when not flying. I have ones for NiMH and for LiPO. I'm all LiPO right now so the other one doesn't come out. The charger will keep the receiver pack topped off. That's what many including myself tend to do. A gel cell provides the power. I recharge the gel cell at home. I keep a spare transmitter pack, plus I have two transmitters anyway (2.4 and 72) so I can transfer packs around as I need to. They get charged with a triton charger off the car battery.

There is enough time between tasks in contests to not require fast charging.

I have a Radio South battery tester that has a switchable load for testing battery condition at the field when I feel the need to.

Gerald

[tai626]

Walt
Now you bring up another issue: charger! Should I start another thread:" which charger and why?" :-)
DLG is sooo light, all my rc equipment can't work on it. I have 600w power supply, that charge 7s A123 at 26A every 20 Min easily, useless in this case. I need new servos, receiver and Batt, of course.
When I started electric power, I was a little lost. But once I decided what batt, everything went smooth. I hope I am doing the right thing here: What Batt???

[tai626]

Gerald:
that is exactly what i looking for, field experience!

[tai626]

Fly2high:
In case of 1A load and 4 cell NiMH, what is the min voltage to be safe?

[tai626]

Another LiFePO4: Hyperion...

Part#HP-FG305-0850
TYPE: 2S 6.6V "flat"
Capacity: 850mAh
Max Current Continuous: 4.25A
Max Charge Rate (4C): 3.4A
L x W x H (mm): 54.5 x 29.5 x 15.4
Weight (g): 48.8

http://aircraft-world.com/shopexd.asp?id=6764

If only smaller....