Help on how too keep a radio, battery warm

When I was up cadair last My radio got a bit too cold and would not turn on ish this could be the radio or battery what would you do to keep it warm.

This is about my HF I-com 703 radio and HF battery

In reply to MW6GWR:

The problem is most likely the battery. All battery chemistries are temperature dependent though the effects are generally only noticable below about 5 degrees C. Not sure which type you are using. I use SLABs as I’ve found them more reliable than NiMH and NiCd cells at low temperatures.

I try to keep the battery off the ground, either in the rucksack, if I’m using it with the FT817 or in a pocket if I’m using it with a handheld. I have also experimented with using various forms of insulation such as bubble-wrap bags to help keep the wind off. It also helps to carry your battery in the middle of your rucksack rather than in an outside pocket to prevent it chilling down too much during the walk in. I try to keep mobile phones in an inside coat pocket for similar reasons.

I guess the thing to do is to experiment at home by putting your battery in the fridge/leaving it outside and then checking the load/no load voltages and comparing against the specs for the 703. Many modern radios etc have a minimum voltage below which they cannot turn on.


Rick M0RCP

In reply to M0RCP:
Hello Rick

Thanks for that bit the battery code is Bp-228 I don’t know the name It give 9.6v.
I have the battery in the bag all the time.


In reply to MW6GWR:
If the battery really only gives 9.6 V then either one cell is dead or the battery is the wrong type for the job. I suggest you check carefully and consider replacing it.
12.5 V actual measured volts is pretty well a minimum for satisfactory use. I am told that the 703 is rather fussy, so maybe more. Radios are generally designed for 13.8V which is what a car battery gives when fully charged.


PS. I have looked it up and evidently misunderstood the rig. More shortly.

In reply to M0JLA:
Hello Rod

Well I looked up the battery to find out its code and as its says 9.6v that is what I put. when I did tests with the radio first it had a happy 5w power what my dad said it ment to be doing. so maybe the website I got it off Is wrong.


In reply to M0JLA:

You have the light weight, low power battery pack.

The power specified in the manual is 9 - 15.87V. The nearer you are to 15.87V at room temperature the less trouble you will have in cold weather. I think you will need a slab (12V nominal 13.8 at room temp) or LiPo (I use a 3 Cell , 11.1 V minimum output) as an external supply. Either will also give you the full 10W (if you wish) and not limit you to 5W.

If you go for the LiPo you MUST use a proper charger which will cost you more than one battery although less than two.

Hope this is some help.


PS I use eleven 2900mAh AA batteries in a pair of holders with the 12th space taken by a dummy cell fuse to protect against fire. These are easy to charge singly, (and easy to replace singly if one fails) which is better for them but cost just as much as a LiPo.

In reply to M0JLA:

Ricky, battery performance drops rapidly when the temp gets to near 0C and especially when below.

I have an Icom handy with a LiPO battery pack as standard. When the temp is below 0C you cannot get the handy to TX at high power, it limits itself to 0.5W to protect the LiPO pack.

ISTR the capacity of a SLAB is down to 50% of rated capacity at -20C. So a 7Ahr SLAB would be a 3.5Ahr SLAB at that temperature.

If you are only planning short activations then a single pack should be OK but if you plan a longer session when it is cold you probably will need more than one battery pack to make up for the drop in capacity. You can help by trying to keep the packs warm with some insulation around them when you are carrying them up the summit. Try not to leave them in a cold car overnight but keep the packs warm and have them in the car interior with you.

Bubblewrap makes a good insulator and it’s very light. As someone else said, try to keep the packs out of snow / off the cold ground. You can also use a handwarmer (the type you boil to recharge) inside the bubblewrap to provide warmth. You’re best not letting the pack/radio get too cold to start with.

Remember though all battery packs can be a fire risk. So make sure you can get them out of your car or your backpack with the minimum of effort just in case.


In reply to MW6GWR:

After wrestling with the same problem with my FT-817, I changed from running NiMH cells to this lithium pack:

It fits nicely within the area of the 817 reserved for AA cells, and it is happy in extremely cold temperatures. The pack is 3AH, 11.1V and inexpensive, only about $30 USD.

When I was still working with other chemistries, I would operate the rig with internal batteries all in a case…eventually the radio’s warmth would make the NiMH cells happy.

Tom, N2YTF

In reply to MM0FMF:
Hi all!

Small pouches of 8 or 10 AA’s (~1500 & 2500 mAH)NiMH. Middle of series configuration fused for safety. Keep in pocket when activating in the cold. Simples to charge and replace. Simples simples. See my page QRZ for examples.


Jack (;>J