As readers of the reflector and active users of SOTA Watch are aware I was let down by my two brand new LiPo batteries when I had set myself up for an HF activation of Birks Fell G/NP-031 on Tuesday.
The two EC Power 14.8v 5000 mAH batteries were purchased from bulk-verhauf in Hong Kong on e-bay at Xmas. I also purchased the Imax B6AC unit to charge them with, these were Xmas presents from my XYL.
On Birks Fell on Tuesday in lying snow at an air temp of -3c the LiPo’s would not even turn on my FT-857. The LiPo’s were outside my rucksack and lying on a nylon bag.
I did not have a multimeter to check the LiPo’s voltage and the rig would not turn on to provide a readout of the supply voltage on the display. After packing up and returning to the car near Redmire Farm at 10.45am, the temperature was 0c and the LiPo cells would still not do the job intended. My 7 AH SLAB in the car proved that it was indeed the LiPo’s that had failed and not the radio.
When I returned home the LiPo’s worked fine in the warmth of my shack.
Testing has been minimal so far. I left one of the LiPo batteries outside for two nights in a plastic bag. It has now warmed up so the minimum temperature was 1.7c overnight. The LiPo worked fine when I brought it in after lying in a temperature of 3c. I need more cold weather before further testing can be conducted.
What I am also going to do today is determine how much time I can get out of these batteries by cycling them with the FT-857 set up at 50w as a CW beacon transmitting for 15 seconds TX and 15 seconds RX whilst monitoring the battery voltage until the rig refuses to function on transmit. I will measure this with a fully charged LiPo that has been in the warmth of the shack (approx 16c) and then I will compare this will a fully charged LiPo that has been left outside in overnight temperatures and compare performance. I also want to determine at what temperature the LiPo cells stop working, so it may take some time to determine that whilst I wait for outside temperature variations.
Hi Phil…tnx fer the detailed report abt your LiPo experiment.
I was also thinking to use LiPo…
Let us know about the results of your further investigations!
Phil, stick a thermometer in your fridge and reduce the temperature in steps, mine will go to about -1C flat out, a newer one might go lower. Also you can make up salt solutions of different strengths and put them in the freezer, they will melt at temperatures decided by their strengths, break up the frozen brine and seal the batteries in polybags then immerse them in the broken up brine.
In reply to G8ADD:
Sounds like a good method, but fridge may not get cold enough. I’ll put the thermometer that I had with me on NP-031 in there Brian. Will try later.
Your initial results are most surprising Phil. I have operated with my 4000mAH 11.1V LiPos in temperatures as low as minus 6C without any perceived loss of performance. I transport them to the summits inside Jiffy bags which are put into an outer zipped section of my backpack and they are farthest from my back so do not get the benefit of body heat. Recently, as a result of changing to an 857, I have removed them from the backpack and laid the LiPos in their Jiffy bags on the ground, but no problems have been experienced even in freezing conditions.
73, Gerald
P.S. I assume that you have a diode or two in series with the 14.8V supply - there is not an issue with those is there?
I too have not experienced any problems with using 11.1v LiPO’s in subzero temperatures, and have been transporting them in a similar manner to Gerald (G4OIG). Been using them for about 10 months on approximately 50 activations.
No diode. I am running the FT-857 now at 16.8v (fully charged state) with no adverse effect. Currently testing and after 25 mins cycling at 50w the battery voltage is reading 15.7v on TX at 50w into a dummy load.
The Yaesu handbook states 13.8v ±15% which at max would be 15.87v and at min would be 11.73v. I took the chance - it is my risk and at 16.8v nothing has melted! I think Yaesu have built in an extra margin which most manufacturers do.
Firstly, like everyone else, I’m relieved to hear you got back home safely. For me, it’s not the summits so much as the unpredictable nature of our roads that has kept me off the hills so far this year. I have had more than enough fun driving to work every day over the Cotswold escarpment.
If you can’t get to the bottom of the temperature-related problem with the cells, I’m happy to put them in our environmental chamber here and load test them. For sure, you’ll not want to take them out again until you understand what happened.
In some ways I’m not surprised to hear of problems but not as severe as Phil’s failure to proceed. There’s lots and lots of gumph in my Icom IC80AD manual about long term storage (discharge to 50% and disconnect), charging and use of the LiIon pack that it comes with. The IC80 is not on sale in the UK yet and was only released about 9 months ago so this is a SOTA (state of the art) SOTA handheld!
The interesting point is highlighted in the manual.
Even when the transceiver power is OFF, a small current
still flows in the radio. Remove the battery pack or case
from the transceiver when not using it for a long time. Otherwise,
the battery pack or installed batteries will become
exhausted.
The battery protection function sets transceiver to Low
power (0.5 W) automatically when temperature is 0°C
(+32°F) or below. In this case, transmit power selections
(Hi/Mid) are also disable.
I’ve noticed on a few occasions that I’ve not been able to select higher powers when it’s cold which fits in with the radio’s built in battery protection. This feature is designed to prevent damaging the cells when attempting to draw higher currents at low temperatures.
Thank you for your interest. These readings may interest you, especially if you run the FT-857:
G4OBK Battery Tests 25/02/10
FT-857 on test with 4S1P 14.8v LiPo 5A battery.
Cycling on TX/RX 15s each 7032 KHz CW
Shack temperature 16c
RX Current 620 mA
Current @ 50w CW output 5.3A
Time Voltage
Start 16.6v
30 mins 15.4v
45 mins 15.1v
60 mins 14.9v
75 mins 14.6v
85 mins 13.3v
87 mins 12.5v (Note still sounding fine on monitor RX)
88 mins 10v No TX No tone
89 mins 9v RX still working at low volume - amazing
Charge time at 3A max from flat was 112 minutes, voltage restored to 16.78v
TX SSB on 144.300 MHz into dummy load
50 Watts (Max) 7.5A on whistle
TX FM on 145.500 MHz into dummy load:
Power Current Drain
5 Watts 3A
10 Watts 3.75A
25 Watts 5.5A
50 Watts (Max) 7.75A
My fridge will not go below 7c and my freezer is at -17c so I guess I shall wait until the overnight temperature falls below zero before I do some LiPo temperature testing.
I’m going to now do the same tests with a 7A SLAB (used since 2008 so probably going off a bit now) and see how that performs as a comparison, albeit at normal room temperatures.
In reply to G4OBK:
[23/01/2010 12:33:25] Frank G3RMD: I have looked at the data sheet for the CPU and confirmed that Max V on pin 35 is 7V. GM4TOE is correct.
[23/01/2010 12:37:33] Frank G3RMD: The resistor potential divider feeding pin 35 has a ratio of 2.7 to 1 (27k/10K) and 13.8 in delivers 5.11V to pin 35. At 16V in, V=5.9 on pin 35, so well in spec. At 18V in Vcc = 6.3v on pin35, still within spec. Conclusion is that there is ‘nothing to worry about’.
[23/01/2010 12:38:40] Frank G3RMD: Would obviously do no harm to limit Vin and reverse protect as well, but I will probably not bother! 73.
Above is a message I exchanged with Robert, G0PEB. The problem with high input V on the 857 is not with the radio bits, but with the Vmax limitation on pin 35 of the CPU. This pin is powered, even when the radio is switched off, and if Vmax(7V) is exceeded it will result in a total write off of the radio. It is probably ok to run the radio at Vin = 16V, which puts 5.9 volts on the CPU, but I am happier limiting Vin to @15V. Hope this makes sense.
Most interesting Phil. The very rapid dropoff in voltage near exhaustion is clearly demonstrated. Based on the average consumption in your test regime, it would appear you got around 4.3Ah out of the battery, but it wasn’t quite fully charged at the start based on the initial voltage so perhaps not too bad. Further results eagerly anticipated!
A survey of manufacturer’s spec sheets failed to turn up any curves of capacity vs. temperature, only generalisations - “reduced capacity may be experienced at low temperatures”. They are however unanimous in stating usable discharge temperature range is -20C to +60C with dire warnings about higher temperatures which cause irreversible damage. All also say that charging must not be done below 0C or above 45C.
I’m sure a while ago I saw on the reflector a reference to problems with LiPo’s if fully charged being damaged by subjection to low temperatures. I could find no reference to this in the (internet published) literature, if the original poster recalls this and has any more info on this aspect I’d be most interested.
Very interesting figures Phil, though I don’t understand the difference between the above figures extracted from your data. Also I’m somewhat bemused by the fact that 50W out on 2m FM pulls 7.75A which is below the figure for 40m if the 10.4A figure is correct - I suspect you may have a typo. The figure of 5.5A for 25W on 2m certainly tallies with my own findings.
It would appear that cell collapse starts around 3.2V. Paul may correct me, but I seem to recall the readily available alarms that can be plugged into the battery activate at 3.3V, so they are certainly worth having to avoid the voltage dropping over the abyss. I always forget to plug mine in though!
Your tests have got me wondering whether I should invest in some 4 cell batteries for use with the 857. I look forward to the low temperature results when we get the next big chill.
The figures are correct and I didn’t typo. It’s simply that the rig is more hungry on 40m CW key down than it is on 2m FM. I’ll check the readings again though when I put the SLAB on to confirm I get a similar result. The SLAB will of course be lower voltage.
Incidentally the power quoted is what the rig’s display stated. Measurement on my Daiwa Cross pointer (Yorkshire with deep pockets) meter shows less output than the FT857 but for simplicity I just quoted the displayed value.
Hi, Paul. It was probably me. I think I mentioned it here and also in the Handbook. This is also why the FT80 manual refers to leaving the batteries at a 50% SOC which is the safe state.
When we ship Li packs around the world we have discharge them to a known state to avoid damage at the reduced temperatures they might encounter in transit.
So, I guess charging to only 80% (say) would potentially solve two problems:
a) the effective over-charge with reduced temperature and
b) provide a lower voltage for the transceiver operating on 4S packs.
My IC80AD manual says the pack should be discharged until the battery indicator shows 50% and the pack disconnected if the radio is not going to be used for some time.
In reply to G4OBK:
Hi Phil.I to am running my Icon IC 706Mk2g at the same voltage and up to now seems fine.Also tried the 817 at the higher voltage and that also seems to cope ATB Geoff G6MZX
… the rig is more hungry on 40m CW key down than it is on 2m FM.
Hi Phil,
That I find strange, but having checked my 857, I can confirm it is a “weird, but true” fact. It is not logical for current drawn on an HF band to exceed that on a VHF one for a given power output since efficiencies usually drop off with frequency. It seems to point to an inaccuracy in the power control in the rig - a reading of 40W out on 40m pulled the about the same current as a 50W reading on 2m.
FT-857 with 7 Ah SLAB on test 26/02/10. SLAB purchased 2008 - efficiency not known.
Cycling on TX/RX 15s each 7032 KHz CW. Power control set at 50w throughout.
Shack temperature 15c
Time Voltage Power Out
Start 12.3v 50w
30 mins 12v 50w
45 mins 11.6v 50w
60 mins 11.3v 50w
75 mins 10.7v 50w
87 mins 9.9v 25w (note unstable but readable)
90 mins 9.6v 10w (ditto)
100 mins 9.2v 2w (ditto) testing discontinued.
RX still working fine at 9.2v.
Current drain on 7 AH SLAB:
RX 600-700mA (varies by mode)
TX CW on 7025 MHz into dummy load
Power Current Drain
5 Watts 3.85A
10 Watts 5A
25 Watts 7A
50 Watts 10.2A
75 Watts 11.8A
100 Watts (Max) 12A
TX SSB on 144.300 MHz into dummy load
50 Watts (Max) 7.5A on whistle
TX FM on 145.500 MHz into dummy load:
Power Current Drain
5 Watts 2.8A
10 Watts 3A
25 Watts 5.6A
50 Watts (Max) 7.75A
The figures give an indication on how long these batteries are likely to last during an activation based on running 50 watts CW.
More cold weather awaited so I can test out those LiPo’s - I may end up sending one down to Richard’s (G4ERP) environmental chamber if it stays warm!
