Ft857 and Batteries - give it to me straight

I have looked online.

I have scoured the forums.

I still don’t have a straight answer to my issue:

I am getting my hands on an FT857 in the near future. I would like to take it portable. How do I power it? I’m not too fussed about weight, I like to use as much power as possible when I need to.

I know there are hundreds of topics like this on the forum, as well as several blogs on the subject…

But, every response ends up descending into debates about the rights and wrongs and ins and outs. Numbers and calculations get thrown around and my head swims to the pont of me getting completely lost.

Trying to search places like Hobbyking for what people mention they use seems to stump me too. I can’t seem to find anyone that carries a 12.3v battery?

I guess a better way of asking would be:

FT857 users: what do you have to power your gear when going portable? Give me a shopping list.

I’m based in the UK so I would really appreciate UK users input as I know I can get my hands on the goods.

Thanks for your help!



Edit: thanks everyone. These are nice, clear answers. I think I will start with a 7ah slab. Cheap and cheerful and although heavy, not a problem for me. :slight_smile: however, once I get the hang of it a bit more, I might upgrade to some lifepo batteries… But that’s a headache for another day…

1 Like

I am old school, so the old school answer is a SLAB, I use an NP7-12 sealed lead acid battery, which delivers 12.6 volts with a capacity of 7 ampere hours. I use this for short walk activations because it weighs about the same as my FT-857D. Its good for a day out at medium power, say 50 watts, and it can be charged from the car cigarette lighter socket after use. There are other options but this is cheap and cheerfull. A smaller (and lighter) one is 4 aH, this will be good for a couple of activations if you keep the power down to 20 - 30 watts. Check with www.yuasaeurope.com for more details.


I don’t have an FT857 but I can see that it requires 13.8V±15% i.e. 11.7V to 15.87V. So LiPo batteries aren’t suitable as 3S are 11.2V but 4S are 16.8V when fully charged. LiFEPO4 batteries are ideal as 4S are nominally 12.8V and 14.6V when fully charged. If you look on Amazon you will see there are plenty of options.


I use the above batteries. All LifePo4. The zippy ones are 4.2 & 8.4Ah. I usually use them for my xiegu g90 at 20w although they will power an ft857. The other 2 are 16Ah & 24Ah and will power an ft857 quite comfortably. They are marketed as golf buggy batteries. They are sold under various brands but are basically the same battery. They seemed expensive when I bought them but the prices are falling all the time. They are far more durable and lighter than lead acid. The 24Ah tracer battery is at least 10 years old and I have not noticed any drop off in its performance.


LiFePO4 batteries are the chemistry of choice these days. Much higher power density and longer life than lead acid batteries. Tracer batteries are expensive but well regarded. I use one.



Hi Alex

You haven’t told us how far you intend to carry the FT857 which will have an impact on your size of battery. Great advice above so here is my take on it as someone who has used the FT857 on limited activations. KX2 now my main SOTA rig as I can use a light battery for all my activations…FT817 was and is a great SOTA rig and lighter.

Here is a battery that I use if I’m going on a long activation but very short and easy walk to summit

cost circa £140 and 22Ah … top of my head will happily run 30watts with bursts of higher wattage when necessary. There is a cheaper battery of the same type but only 18Ah. circa 2Kg.

Hobby King do a range of Turnigy batteries 4S 14.4v 6200mAH (6.3Ah) which will drive the FT857 for a limited amount of time with careful management of watts but nice and light for a long trek… …available in the UK.

Other suppliers in the UK but more expensive but quality products are:-

I’ve used their smaller LiPo 4Ah batteries with 817 and KX2 for many years…batteries are still going strong on other projects so good quality but expensive.

Expensive but quality power packs

Based in North Wales …I’ve bought from them so genuine company…

Hope this helps

73 Allan GW4VPX


6.5 Ah LiFePo4 (~ 800 g) will power your radio for a good 3 hrs @ 50 W SSB.


PS: I have no idea how Brian powers his 857 with an old 7 Ah SLAB for a day. My SLAB (9 Ah) was flat after 3 hrs. Must be the good old days when batteries were of a different quality. :wink:


The 857D works fine from U > 9.5 V, however not at full power. Below ca. 9.5 V, SSB TX audio gets distorted.



We use a Ultamax 16ah golf trolley battery to power a yeasu ft-891 (similar to 857) or the ft-8900 50w quad band vhf/uhf mobile. Handy size and weight for the not so hard ascents and lasts a long activation (have run 6 hours easily).

The ones myself and M1BZJ have also have a t-bar connector with very handy powerpole connectors on the end.




SLAB batteries seem to have become more expensive here.

As others have said the smart money is on the LiFe batteries with built in Battery Management Systems. The prices have dropped and its worth while shopping around for the best deal. If you look at the ownership cost over the life of these batteries they come out well in front of the SLAB. The debate is over.

But cheap, repent at leisure.



When I ran a FT-857D I used up to four LiFePO4 4S 4.2AH in parallel. Having the ability to use 16.8AH allowed me to stay on summits longer, for example during S2S events. For average activations I used to take two, but often only needed one 4.2AH battery. These batteries were sourced from Hobbyking, but are pretty much unobtainable now. Tracer batteries are the choice of many activators, but they tend to be very expensive for the smaller capacities.

Having sold my 857 and gone down the 817 + linear route, I now only need one LiFePO4 battery for the linear and run the 817 off a 3S LiPO.


The NP7-12 SLAB can still be bought here for less than £20. The advantages of LiFePO4 batteries are obvious, but the good old SLAB has its points, too. Its cheap, it does not need expensive chargers, can be charged in the car, and it delivers a constant voltage. Claims that it has a shorter working life may be true, BUT…Twenty years ago I bought two. I was disappointed when one died after only ten years, the other one is still good today, and in regular use running my FT817 in the shack and my 857 in the garden and portable. The trick is to never run them flat and top up the charge after every use. That said, when mine dies I will replace it with Li, I’m getting old and feel the weight more than I used to.


I’ve had my 857 since 2015 and have done many an activation with it.
I only ever use a 4200mAh 4S LifePO4 with it when portable. This weighs in at around 500g. No BMS so you have to be mindful of not running it too low.
On 25W FM this will typically last at least an hour and on SSB a little longer.
If I wasn’t bothered about carrying another 2kg and wanted to regularly camp out somewhere then I’d go for something like a 24Ah Tracer that has built in BMS.


Exactly the same as @G1INK Steve. The 857 is a heavy radio, so carrying anything larger is going to hurt! The 4.2Ah does for most of my activations with the 857. For longer ones, I take the bigger one or both of them.



Hi Alex,

You probably need to consider what your plan is for SOTA and other portable operating. Are you intending to hike up to a summit, set up a tent and sit there all day and chat to people on HF or digital modes (FTx, SSTV etc), or are you going to want to activate a summit as part of a longer walk? Perhaps you will want to go on a crazy multi-summit hike, which includes multiple SOTA activations (see Fraser’s YouTube channel for some great examples). You may want to combine SOTA with other schemes (WAB, POTA, WWFF, GMA etc).

Answering these questions will help you answer your battery question. And longer term it will probably help you determine whether the 857 is an appropriate radio for the activations you like to do.

I started with an Icom IC-706, which was replaced with an 857D. Fed up with the 2kg+ weight, I got rid of the 857 and bought an 818. I’ve only really used that radio since 2020, apart from the odd experiment with a handheld or my FT-891. All of Nic’s activations (M7NDC/2E0NYQ) have been using the 818, so a quick look at the database will show what can be achieved using a lightweight, QRP radio. We’re both targeting ‘mountain goat’ by the end of the 2024 winter season.

It’s worth noting that I intend to get rid of the 818 soon, replacing it with something even lighter. This is because almost all of our activations are completed whilst on day hikes of 16 - 20 miles. SOTA is just one element of our hikes, it is not the be all & end all of the day, as such I need to balance the radio kit weight alongside first aid/shelter, food, water, extra coats etc etc. As I’ve learnt from my activations and watching other activators (Fraser, Tom @M1EYP etc spring to mind), I’ve been able to limit what kit I take but still have enough to qualify summits. My early attempts using a 2m handie were deeply frustrating, whereas now virtually every activation is successful (although I’ll admit yesterday on G/NP-018 we only just qualified - HF was not working well at all!).

Whatever you choose to do, it’ll be valuable experience. Just don’t spend too much money on stuff while you’re experimenting :grinning: If you find some local amateurs, you may be able to borrow some kit and trial things out, before you commit to buying.

73, Simon


This matches my experiences with my 4500mAh LiFePo. With 50W SSB and short overs, the battery is empty after 1 hour. You have to keep in mind the drain of 1A at RX.
73 Chris

1 Like

I have run an FT857D on hundreds of summits.
I run at 50W on ssb/cw and 25W on FM
It runs happily down to 10.8V so I use 3 cell Lipos
I have 2 X 5Ah batteries in parallel, individually fused at 25A
This combination means I NEVER leave the pilup

Have fun


Some info on prices… I could have held out for more but I wanted to downsize my ever growing HF radio collection. All sold since mid-Mar 2024.

2001 vintage 817, perfect, complete with all original accs, boxed, sold for £315
2006 vintage 817nd, perfect apart from paint chips, all accs except strap, boxed, sold for £325
2000 vintage 706MKII, used but working, mic, power filter, manual, sold for £350
500Hz 817 CW filter, sold for £155

818’s obviously go for higher prices being newer but I was happy that I could get good prices for 18,23 and 24 year old radios. People often ask what I consider quite stupid prices for old ham radios. But well priced items are available with some looking.

EDIT: I see someone is asking £900 for an 817nd on eBay.
shakes head and sighs


@MM0FMF I was hoping the 818 would fetch about £1k to pay for the KX-2 Andy…I’m perhaps being about as optimistic as that eBay person there…!! :grin::rofl:


This is what I use with the 857D (if it’s a small/easy summit):

I also have a 10000mAh which is considerably lighter - this one is definitely not light.

As other have said, the FT857 requires 13.8V±15% so that’s 11.7V to 15.87V. A fully charged 4 cell Li-Po delivers almost 16.5V, so I use a crude dropped diode (aka BFO rectifier diode) for the first 10 minutes to drop the voltage to under 15.87V:

After 10 minutes, the 4 cell Li-Po output voltage drops and so I whip the diode out. The diode can get a bit warm if you’re transmitting on full beans …