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LiPo / LiIon in cold conditions


#1

I was looking in the owners manual for a new Icom handheld that uses a LiIon battery. I was surprised to see that the handheld locks itself in low power mode (0.5W) when the temperature is below 0C to protect the battery. I had a look for performance data for LiPo packs at low temperatures and all I have been able to find so far is lots of RC modelers regurgitating other peoples’ “sage advice” about the lack of performance form their packs when it’s cold but no hard performance curves. Now RC modelers hammer their batteries compared to us so it’s no surprise that they show up the worse performance of batteries when it’s cold.

I was wondering if those who have been using LiPos for some time have actually experienced poor performance when it’s cold to such an extent that it has affected their operation. Also if anyone else with a modern handy using Lithium battery technology has noticed low temperature problems.

Andy
MM0FMF


#2

In reply to MM0FMF:

Hi Andy,

my camera uses a LiPo cell and I noticed an enormous drop in battery performance during wintertime at temperatures below 0°C. At a certain point the camera simply wouldn’t power up any more although the battery had been fully charged at home. Keeping it warm for 15 minutes always did the trick.

Maybe one of these will be of some help:
http://tinyurl.com/mhh7es
The sheets come along with a diagram “discharge temperature characteristics”.
AFAICS you’ll lose about 50% performance at -10°C, at -20°C only 1/3 of the nominal capacity is left.

73 Bernhard DL4CW


#3

In reply to MM0FMF:

Hi, Andy.

It’s possible to damage Lithium cells by getting them too cold. The capacity is related to temperature so if you fully charge them at room temperature then freeze them on a hilltop, you effectively end up with overcharged cells.

When we ship them freight, we have to make sure they are at a known state of (dis)charge - for safety reasons.

I guess the answer is to keep them warm. That way they’re safe and able to give best performance.

73, Richard


#4

Andy
In the RC world (Helicopters personally, 25A discharge rate for a 3 cell Li-po) we keep them in an inside jacket pocket prior to use on cold days, and suffer very little by way of reduced flight times. A couple of club members found out the hard way when the technology was first affordable by crashing models due to significantly reduced capacity and the esc cutting power to the rotor blades after a couple of minutes of flight time. They had fitted the cells to the air frame and then waited for up to an hour for a peg (authority to fly). The cells of course then cooled to the ambient temperature (frosty morning).
Being a mostly fair weather flyer these days, its not so much of a problem for me…
Tim
G4YTD


#5

In reply to G4YTD:

Thanks for the info from everyone. The Sanyo site is most useful, hard data to digest and comprehend.

I’ve picked up some RC packs off eBay for small change in reality and a test of one pack showed it to be ideal for my HF QRP SOTA needs. My 4Ahr 15C pack driving the 817 in a test showed that after 3hours on receive and 30minutes CW TX at 14wpm from the beacon (3 x 10mins TX followed 1 hour RX) I could still get the full 5W on FM from the 817. With the 817’s power thirsty receiver and some transmission that period accounts for about half of the pack’s capacity. That’s more than enough for 1 activation. If the capacity were halved because it’s a cold and frosty day it would still do for 1 activation. Allowing the fact that 2 packs weigh 600g for 8Ahr capacity and my old SLAB weighed 1300g for 2.8Ahr I can carry both for a winter activation and still be able to out perform the old SLAB and be 800g better off. That’s about the weight of a 500ml flask of something hot and tasty.

I was concerned that the drop in performance when it’s cold may preclude their use. However, it looks like ensuring the cells don’t get too cool, i.e. wrapping them up in some thermal insulation in the bag during the walk in will help. I might also be able to use the thermal gel handwarmers I bought on the packs as they’re bog all use on my hands!

Andy
MM0FMF


#6

In reply to MM0FMF:

Hi Andy,

The Lithium cells LiFeS2 (not LiPo or something else) work very well at low temperatures. I used 8 x AA Lithium batteries during my activation in Lapland last March just in case that the temperature would be very low. My Alkalines weigh 214 g in the battery holder and the Lithium cells are even lighter. The battery voltage exceeds initially the nominal 1.5 V, so some manufacturers say that Lithiums should not be used in their equipment. See for example

http://data.energizer.com/PDFs/lithiuml91l92_appman.pdf

73, Jaakko OH7BF/F5VGL


#7

Hi all

using Lipos with FT817 over 3 years now i can confirm that in low temps (OVER 0c) they appear to drop their voltage sooner than it was expected (for a 11.1V unit you have to stop operating at abt 9V).

I speak about 3C RC-models LiPos 11.1v in the range of 1800-2500 mah, 20-26C.

Keeping them in a small wool or fleeche bag seems to make a difference.

But i think that they are still the perfect choice for a quick activation where the radio load weigth is critical .

73, Panos, SV1COX


#8

In reply to SV1COX:

LiPos - at least the once used for model aircrafts - loose capacity and high current ability at low temperatures. Heating is needed to fly these batteries in winter. Obviously this is not a problem when using LiPos for QRP.

I would never carry them close to my body to warm them since they present a - small - risk of fire (and not just when charging as it was said here).

Just follow the model aircraft forums attentively.

73,

Gerd.