RCR123 3.6v maximum current output

[Fallingwater]

How many amps can I reasonably expect a 3.6v RCR123 cell to give before it overheats and its voltage sags into uselessness?
Could one maybe deliver a constant two amps with peaks of three?

 

[bfg9000]

Depends on your particular RCR123, but generally the consensus is no more than 1.2A (~2C) or it will sag too quickly to be of much practical use.

 

[Fallingwater]

*sigh*
There goes my project of running my RC helicopter on a 2s2p pack of RCR123s...

Thanks anyway.

 

[SilverFox]

Hello Fallingwater,

Li-Ion cells are rated for a mid point voltage of 3.6 or 3.7 volts under normal loads. In high draw applications, it is best to try to keep the voltage around 3.5 volts. When the mid point voltage drops below that, the cell heats up, a lot.

If you don't value cycle life, and have unprotected cells, you can run them under a load that gives a mid point voltage of 3.0 volts, but you should provide cooling for the cells under those loads. Cell temperatures, under those kinds of loads, will exceed 145 F in the open air. The temperature will be higher if you enclose the battery, and the exponential increase in temperature may get you into a thermal runaway situation.

Most Li-Ion cells will handle a load equal to twice the actual capacity of the cell, but don't expect high cycle life from them.

Tom

 

[barkingmad]

What about something like a lithium ion 18650 cell - typically around 2200-2400mah capacity so if you stick with 2C you should be able to draw about 4-5a.

Otherwise I have seen some NiMH cells that let you draw a lot more (20-30a) - but might be too heavy as you would need more cells for the voltage.

 

[Fallingwater]

What about something like a lithium ion 18650 cell - typically around 2200-2400mah capacity so if you stick with 2C you should be able to draw about 4-5a.

Too heavy. My helicopter runs on 7.4 volts, so I'd need at least two 18650s, and the motors don't have enough power to lift that kind of weight.
I've been using two LiPo batteries (each with two cells), but one is getting old and the other just puffed up on me.
I'm looking at alternatives that are cheaper and safer, but apparently the only way to go that isn't LiPo is NiMH AAAs: less run time, heavier and more likely to die due to overstress, but at least I won't have to worry about them puffing up and starting a fire...

 

[bfg9000]

Well there are a lot of other sizes. Two 14670s or 17500s should deliver 2A just fine.

 

[AndyTiedye]

Can you use LiFePO4's or A123's? They seem to really like high currents.

 

[Fallingwater]

Well there are a lot of other sizes. Two 14670s or 17500s should deliver 2A just fine.

The heli has a peak draw of six amps. 2A won't even get it to lift off.

Can you use LiFePO4's or A123's? They seem to really like high currents.

A123s are too heavy. Good for larger-size helicopters (actually many people over at RCGroups have been making a great deal out of them for a while), not good for micro-sized ones like mine.
I never heard of LiFePO4. Any more info?

 

[FlashCrazy]

I buy all of my Li-Po battery packs for my r/c airplanes from Common Sense R/C. They have a 7.4V 800 mAH 8C pack (good for 6.4 amps continuous, with bursts of 9 amps) for $12.00. A 10C pack from them is $13.95. I love their batteries, and they have great service and prices. Here's a link to the 8C packs...the one you might be able to use is at the top: http://www.commonsenserc.com/index.php?cPath=37_35

 

[mdocod]

interesting... you are planning on running 2s2p RCR123s... is the amp draw you are talking about on a per cell basis or for the completed pack? (cause the pack you are describing could deliver ~2.4A total safely[never mind, just noticed above you need 6 amps to get it off the ground]

anyways... if the plane can lift a 2s2p (4 cell) pack of RCR123s, then it can definitely lift a 2x18500 pack.. which would actually be smaller and lighter and have more useful capacity and deliver ~3A safely.[scratch that idea too... 6amps.... hmmmm, would need 4 18500s]

 

[Fallingwater]

I buy all of my Li-Po battery packs for my r/c airplanes from Common Sense R/C. They have a 7.4V 800 mAH 8C pack (good for 6.4 amps continuous, with bursts of 9 amps) for $12.00. A 10C pack from them is $13.95. I love their batteries, and they have great service and prices. Here's a link to the 8C packs...the one you might be able to use is at the top: http://www.commonsenserc.com/index.php?cPath=37_35

I'm aware LiPo packs are ridiculously cheap for you americans, but getting them in Italy from online stores that aren't eBay is surprisingly expensive.
Don't get me wrong, I love eBay, but the pack that just puffed up on me was an eBay special. The next pack will come from a more reputable source than some random dude...
I know most american battery stores from threads on RCGroups, but they all have ludicrous international shipping prices, so ordering from them is out of rhe question.

By the way, I've given up on LiIon for the helicopter. It's clear the LiIon chemistry can't stand such high draws without being unacceptably heavy, so it's going to be either new LiPos or homemade NiMH AAA packs... still gotta decide.