Did anyone else notice the problem with a power meter reading or an output power configured of the FT-817 in severe cold? It seemed to me as if the transceiver decreased power. The near-ground temperature without any turbulent mixing was about minus 15 degrees Celsius and the displayed output power was lower and lower while battery ok.
73
Karel OK2BWB
In reply to OK2BWB:
My FT-817ND was operating fine 2.5 hours today in OK RTTY contest at a hunters seat in a field near Prague. It even produced some heat to warm my fingers 
On digimodes I switch meter to ALC so I didn’t watch the PWR meter. The voltage display seemed normal to me.
The LCD display of NUE-PSK modem was quite lazy to redraw but also worked ok, total 20 QSOs on 80 and 15m and packed at sunset, it was getting really cold even here. The biggest trouble was disassembling the fiberglass mast, the joints froze together and I had to rub them and breathe at them to pull them apart
73, Marek OK9HAG
In reply to OK2BWB:
Hi Karel
I’ve noticed this - when operating at sub-zero temperatures at first the power reading is low, but after a few minutes operating full power is once again indicated. I’ve never checked whether it is just the meter reading low or whether the power output is actually reduced. Might venture outside and give it a go tomorrow to see, it’s currently -9 C and dropping here.
The 817 does generate a lot of heat. I place my LiPo batteries on top of the radio inside the waterproof container I use, to keep them warm. (although I’ve tested them down to -10 and there doesn’t seem to be any problem with them)
73 de Paul G4MD
In reply to G4MD:
I would suspect the batteries. I have no idea what the effect of cold is on NiMH cells, but cold definately reduces the output of NiCd batteries quite significantly.
73
Brian G8ADD
In reply to G8ADD:
Cold defiantly reduces the protuberance of NiMh Batteries.
various manufactures quote various figures and charts but NiMH lose at least 20% of their deliverable capacity at freezing (32°F, 0°C) without a significant loss of voltage. At -20°C, they can lose 80%.
http://dpfwiw.com/batteries.htm#cold
Darius OK7OK
The cold can significantly effect the output of NiCd, NiMH and lead acid batteries. The cold is one reason so many car batteries fail in winter and they are designed to be used outside. The seal lead acids we use are really designed to be used in doors. I have not used LiPos so I don’t now how badly they are effected. There should be working temperatures around on the manufactures web sites though.
I have seen the problem with the 817 (although never down to as far as -15) and the power seems to come back up as the rig and the cells gets warm. I have an Olympus compact digital camera and have had brand new both Zinc Carbon and alkaline batteries fail after two shots at temperatures approaching zero. Sub and zero the batteries fail completely.
When I packed up the night before for an early start on some RAYNET exercise or other I have had hand held rigs with fully charged NiCD and NiMH fail after a couple of transmissions after being left in the car over night at sub zero temperatures. Placing them on the dashboard of the car with the screen heater blowing brought them back to life and they worked all day after that.
I suggest you keep the 817 well wrapped up with one or two of those gel hand warmers on the walk to the summit in cold weather. That way it should work straight off and the heat generated will keep it going.
Regards Steve GW7AAV
Hyperion says operating temperature for their LiPos should be above 10°C and they tell you to store them at between 2 to 20°C. Temperatures bellow zero or above 50°C can apparently “seriously damage” LiPos. Above 50°C they can burst in to flames, but I can’t find out what happens when they are damaged by sub-zero temperatures. I would suspect however that the damage might lead to a failure later when you come to charge them with the possibility of dramatic consequences.
Hyperion also mentions colder temperatures could cause an over voltage condition, which is something that may be of concern particularly to those who have gone down route of using two 7.4v packs to give 14.8v rather than the single 11.1v cell that 817 users might be inclined to use.
Steve GW7AAV
In reply to GW7AAV:
G’day Steve
Most LiPo manufacturers specify their cells for use down to -20. De-rating charts can be found on their data sheets. I’ve tested mine at -10 and not had significant reduction in voltage or output, but only tested them at the fairly sedate rate of discharge required for the '817.
Important not to charge them at low temperatures though (most state below 0 C) - the reduced ion mobility in the polymer-bound electrode can lead to localised catastrophic overcharge and consequent damage.
73 de Paul G4MD
In reply to G4MD:
From what I just read the problem at sub-zero temperatures in LiPOs is not a reduction in voltage but a over voltage. In fact some radio control operators store their LiPos in the freezer over night prior to use because they think they get more power out of them, which seems to suggest there is something to it.
I think the issue is not that they do not work at -10 but that you may be doing gradual permanent damage that might later lead to localised catastrophic overcharge. This may not be a significant problem for SOTA operations where we operate from time to time in these conditions, but from what I read storing the cells in the freezer like the RC guys are doing may well be plain dumb.
One manufactures sheet I just saw says the operating range is 20-25°C, which suggests either they are airing on the side of caution or even the makers don’t really know.
Steve GW7AAV
In reply to GW7AAV:
Hi Steve
Sorry if this reply goes on a bit, but I feel very strongly about debunking the myriad myths that have grown up around LiPos…
From what I just read
Sadly there must have been more misinformation written about LiPo batteries than almost any other technical subject we encounter. Even crossed-field antennas 
the problem at sub-zero temperatures in LiPOs is not a reduction in voltage but a over voltage.
Not true. As the cell temperature reduces the terminal voltage drops. To about 3.4V for a fully charged cell at -20 deg C, actual figure quoted seems to vary a bit with manufacturer. Realisable capacity also drops, to around 60% of the cell’s capacity at +20 deg. C, again varying a bit betwen manufacturers.
In fact some radio control operators store their LiPos in the freezer over night prior to use
Won’t hurt them, storage at down to -20 deg C is OK and freezers generally maintain -18 deg C
because they think they get more power out of them, which seems to suggest there is something to it.
Well they don’t, which seems to suggest they don’t know what they’re talking about
I think the issue is not that they do not work at -10 but that you may
be doing gradual permanent damage
No you’re not, you’re operating them within the manufacturer’s stated safe conditions
but from what I read storing the cells in the freezer like the RC guys are doing may well be plain dumb.
That’s true! Presumably they warm them up before use so what’s the point?
One manufactures sheet I just saw says the operating range is 20-25°C,
which suggests either they are airing on the side of caution or even
the makers don’t really know.
Don’t know where you found that, but it’s so ridiculous I’d suggest it’s not on a bona fide manufacturer’s data sheet. The makers do really know, and they publish the information.
To summarise (and this information is on every manufacturer’s data sheet I have ever found, so probably applies to the vast majority of cells available)
LiPo’s can be safely discharged at temperatures over a range of -20 C to +60C, although terminal voltage and capacity are reduced at lower temperatures, particularly below freezing.
LiPo’s should be charged at temperatures above 0 C and below 45 C
LiPo’s should be stored at temperatures between -20 deg C and +45 deg C. If being stored for any length of time, storing at a terminal voltage of about 3.75V per cell is optimal to minimise degradation.
LiPo’s should never be allowed to reach a temperature greater than 80 deg. C
Having said that, if anyone has definitive information to the contrary I would be most grateful to be made aware of it.
73 de Paul G4MD
In reply to G4MD:
Well you will not get me using LiPo’s ever again since the day one spontaneously exploded and burst into flames in my car on the road down from Long Mynd to Church Stretton. It could have resulted in a very serious accident.
73,
Walt (G3NYY)