Batteries for FT-817

Has anyone found a good battery for the 817? Some people have posted that they had problems with interference with the Tekkeon MyPower. I’ve considered using SLABs but would like something lighter. Any suggestions?

73 Timothy 2E0KEA

In reply to 2E0KEA:

hi timothy

im looking at buying a 857 for my portable SOTA work and it has been suggested to me to use a golf trolley battery they dont seem that big and not too heavy but might be too big and heavy for what you are looking for

thinking of getting one of these myself

73 Matt M3WDS

In reply to 2E0KEA:


I use a 2AH SLAB with an 817, its light enough to carry and runs it fine for a few hours at 5w. Goes in my backpack whilst cycling. I would think that the 857 wouldnt last so long though, but just a thought :slight_smile:

Good luck, John.

In reply to 2E0KEA:

If you use the search facility on the reflector you can read the many hundreds of replies there have been about batteries over the years. You may find the answers you need already exist. You are correct about the MyPower and reports of RF interference from it.


In reply to 2E0KEA:

Hi Timothy,

My favorite battery for powering the FT817 is a
Powersonic PS1220 2Ah SLAB I was given a while ago.
I believe these are designed for use in intruder
alarms and are thus not deep discharge batteries
as some would recommend. It does however always
seem to do the trick, providing me with ample current
to run a FT817 and/or my Kenwood TH-79E handheld at
full output. I’ve yet to fully exhaust it during an
activation (which are typically of an hour
or more in duration.) I’d estimate that at most it’s
been discharged to 70% of its capacity (1 hour at 5 Watts
on FM, assuming 60% PA efficiency, 50% duty cycle) It
weights in at about 1Kg which is not too bad and in
any case provides a convenient counterbalance to my
water bottle.

The only problem with SLABs other than the weight issue
(and the safety issue of course - you definitely don’t
want to drop a tent peg across the terminals of a SLAB
or NiMH battery for that matter) is that you need to
prevent them getting too cold i.e. keep them above
about 0 degrees centigrade and you should be ok.
My experience is however that NiMH and NiCd batteries also
perform poorly at low temperatures, despite claims to
the contrary by some authorities. I keep my handheld
with its NiMH battery pack in an inside pocket in my
coat for this reason.

NiMH/NiCd calls are of course also prone to the memory
effect if the appropriate charging and discharging
regime is not kept to - making it hard to be sure how
much capacity they actually have.

By the way, over the last summer, I managed generally
to recharge the SLAB each week using one of the solar
battery chargers that where on offer recently at Maplin -
an approach that failed only when there was insufficient
direct sunlight - or insufficient time between activations.
The same charger can be used to float charge the battery
keeping it fully charged at all times - a state SLABs
prefer. A further advantage of SLABs is that - provided
you take care - you can recharge then from a car battery
via the accessory socket which is useful when on holiday

Anyway, those are my thoughts on the subject. I can’t
comment on lithium ion batteries - I’ve heard good things
about them but I understand they are expensive. In
summary I’d suggest you go for a small 2Ah SLAB as your
primary power source, and stick some large capacity NiMH
cells in the FT817 as insurance.

Hope that gives you some ideas.


Rick M0RCP

In reply to M0RCP:
Hi, Timothy. I had an 817 until recently (I use an 857 now) and I performed the “green wire mod” and used a set of 2800 mAh NiMHs in the battery box. In case you don’t know this already, the battery box is intended for 8 dry cells and is wired so that you can’t try and charge the dry cells, cutting the green wire from the battery box and insulating the end allows you to charge the batteries inside it in the same way as the provided battery pack. A set of 2800 mAh NiMHs gives about two hours of operation, and you can carry a spare set of fully charged NiMHs to refill the box with if you are doing multiple activations. Even with a spare set the total weight is less than the rig and a slab.

It is worth bearing in mind that the 817 runs on 9.8 volts and running it from a 12.6 volt slab (or a 13.8 volt mains supply) just means that an internal regulator drops the surplus voltage and generates unnecessary heat…although in winter activations it might be useful to have the rig double as a handwarmer!


Brian G8ADD

In reply to 2E0KEA:

Hi Timothy

Despite the weight, I can heartily recommend a SLAB of appropriate size for running your '817. I currently use 4AH units weighing in at 1400g and get 4 good activations out of one without problems. Note that the capacity is to a degree dependant on the discharge rate relative to the total capacity, hence my preference for a perhaps slightly oversized battery - you get more out in the end. For cyclic use, charging to 14.5 volts or so rather than the 13.8 you get from the normal float chargers is of advantage.

Whatever type of battery you use I recommend researching their properties and the way to treat them on battery manufacturer’s sites - myth and misunderstanding abounds, but when you read authoratitive texts it all makes sense, and treating them properly really does pay dividends in terms of useful life and reliability.

Whichever way you go good luck, and I look forward to working you from the hills!

73 de Paul G4MD

In reply to G8ADD:

It is worth bearing in mind that the 817 runs on 9.8 volts

Hi Brian

I have seen this quoted in a couple of places, but can’t find any definitive substantiation for it. As far as I can make out although the rig does have a regulated 9v line for running various parts of the circuitry, the main current users (ie transmit driver and PA) run from the full applied voltage (less the drop in a schottky reverse polarity protection diode and a filter choke). The rig’s spec. is also quoted at a supply voltage of 13.8, and it automatically restricts power output to 2.5W when used with the internal battery pack. (This restriction is over-ridable and the rig will (just) provide it’s full rated output at the lower voltage, but I have seen American reports that say it barely meets FCC requirements for spectral purity when operated this way)

I’d be very interested if any technical whiz out there has the full story…

73 de Paul G4MD

In reply to G4MD:

myth and misunderstanding abounds

It most certainly does. I cannot agree strongly enough with Paul’s advice to read the manufacturer’s info. Yuasa produce excellent information on their SLA ranges and this can be had for free from their website.


Hi Timothy

When I use my 817 for activations, I use 3ah SLAB’s and find them to be good for 2 decent length activations, typically up to 40+ contacts, bearing in mind that I activate mainly on 60m-ssb and 40/30m-cw, both modes being more current economical than fm.
I find that the 3ah SLAB is a good compromise ie, cheap, quite light to carry, but supplying the required current for the 817. The 817’s internal NiMah pack acts as a reliable back up power source should it be required.
There are other alternatives such as home-brewed AA NiMah packs, it’s a matter of personal choice.

73 Mike GW0DSP

In reply to G4MD:
You might be right, Paul, I no longer have the circuit diagram - and always found it quite confusing because my mind still runs on valves (hollow state!) but it is noticable that even on receive the rig runs a little warmer on 13.8V than on the internal battery pack. That may just be the regulation for the 9V line.

One possible way of checking would be to measure the output on 12V and 13.8V, if it is the same for both voltages then there is regulation, if 13.8 gives a slightly higher output then there is none.


Brian G8ADD

In reply to 2E0KEA:

I use a SLAB, Yucel 12v 2.1Ah (£9 from a local alarm distributor) and I also made a new battery pack for the 817 using 2500MAh batteries (£1 for 4 Aldi) and with that it all fits in a world pouch ( world pouch) then this lot sits in a Tupperware box (waterproof) inside my rucksack.

I get more than enough power for a long day of activations (6 summits) and that suits me just fine. I never go out the next day with charging the whole lot up first, I just wont take the risk.

Yes I could get lighter, yes I could get better, but it’s cheap and does the job just fine. I replace the batteries at the start of ever year.

So far I have no complaint about the way I have my 817 setup, I could improve on the weight but at a cost. I never run out on a days activation.

Another option is, or (12V 4200mAh Nickel Metal Hydride (NIMH) Battery Pack for $48 and a charger for $9)

Thanks for all these replies.
Because I live a long way from any hills, doing SOTA activations is always part of a bigger trip. Sometimes we have the car but when we went to the Lake District we were walking from one place to the next so had to carry a charger as well as batteries. I think that a Li-ion battery like the Trekkeon would be better, even though it’s more expensive to start with, so I was wondering if anyone had found a better alternative to the Trekkeon.

73 Timothy 2E0KEA

In reply to 2E0KEA:

The problem with Li-Ion cells is that they don’t fit the voltage range we as hams want. We want a nominal 13.8V but Li-Ion packs are either 11.1 or 14.8V. Except they’re not and unlike SLA,NiMH and NiCd cells, Li-Ion don’t have nice flat voltage characterisitics. The 14.8V cells are something like 16.2V when fully charged which is too much for most ham gear. Without a regulator you would not be able to fully charge such cells, you could partly charge them instead. The 11.1V are nearer 13V when charged but you can’t run them as flat before the voltage is too low to get full output. This means that without a regulator any Li-Ion cells cannot be used to their full capacity. I don’t have any hard figures but you would be paying for a 4000maHr pack which may have only 2750maHr usable capacity. Such a pack is much lighter than a 2800maHr SLAB but at considerably greater cost.

You could use a linear regulator to drop the voltage to 13.8V and use the 14.8V packs but then you convert the excess volts to heat. So you need a heatsink which is more weight and you waste energy. An 817 wants 2A and if you are trying to loose 2V says, then that’s 4W to get rid of as heat. Hell I only get 3.9W of RF from my 817 on 5MHz.

The Li-Ion packs have switching regulators to be more efficient and these are the source of the RFI you have read about. It’s possible to design RF quiet switching supplies but more expensive. So unless you are lucky, any commercial Li-Ion pack is likely to have an RF noisy regulator, especially if you buy a cheap BV-land model!

So you need to check any Li-Ion pack is RF benign before handing over coin of the realm. What’s needed is a ham-friendly buck-boost 13.8V regulator for about 3A that runs from either 11.1 or 14.8V RC Li-Ion packs. I’m surprised such a design doesn’t already exist.

Unless you hit pay-dirt and find such a Li-Ion pack, NiMHs/SLABs plus a small charger will have to do. For upto 3000maHr cells, you should be able to find a small wall-wart charger that is not too big and heavy to carry with you that can charge a pack in a reasonable overnight time frame.


In reply to MM0FMF:

The problem with Li-Ion cells is that they don’t fit the voltage range
we as hams want.

That is generally true, for stuff that wants 12V (really 13.8V) to work properly. But for the FT817, which really doesn’t need more than 11V and works very well at 9V, a three cell Li-Ion battery is absolutely perfect. The radio will run cooler and last longer, plus ampere hour for ampere hour a Li-Ion battery is much smaller and a fraction of the weight of any other current battery technology. Li-Ion really is the perfect solution for the FT817. Unfortunately, they ain’t cheap and they need a purpose-made charger too.

In reply to 2E0KEA:

I would beg to differ from MM0FMF and G3WGV concerning Lithium Ion batteries.

I have used a Li-ion pack (4 cells) for the last 2 1/2 years, it incorporates its own (RF silent) regulator, can be recharged from a car battery as the charger is integrated into the regulator circuitry (plus has a wall wart type of unregulated charger) and provides the 12 volts asked of it. Capacity is about 4AHr and it weighs 400gms in its carry pouch. I know that both GM4COX and GW4BVE use exactly the same pack as myself - unfortunately it is no longer available! The only thing I do agree with from many of the posters - the cost can be eye watering compared to a SLAB, although these days some think £50 - £60 is petty cash (not me I hasten to add!!)

There was a thread on this reflector about a year or so ago and I know BVE found an alternative source of Li-Ion packs. There is absolutely no way I would contemplate hulking a SLAB up a hill - my pack weighs enough as it is. The replacement battery for the 817 from W4RT does provide a day’s operation on SSB, though I have no experience of its capacity if operating FM, and it fits internally to the set.

Then, of course, you could consider Lithium Polymer; but remember the fire extinguisher!

There you are, my two penn’orth!!


Barry GM4TOE

In reply to 2E0KEA:
I bought a higher power internal Li-Ion pack from W&S which has served reasonably well (it’s made by Strikalite). When the original Ni-CD battery pack died I sent it to Strikalite. I did have to trim the sleeving on the remanufactured pack slightly, but it wasn’t a major problem. Both packs are around the 2.2Ah capacity mark.

Per usual - no connection with the company except as a happy customer - their prices are reasonable and they have a quick turn around service. I’ve had packs for various radios rebuilt by them, too.

Graham G4FUJ

In reply to GM4TOE:

Actually Barry, you seem to be agreeing with me rather than differing! Yes, of course you can get Li-Ion battery packs with a built in regulator system to permit charging from a standard charger, but the battery itself (i.e. just the cells) needs a special charging system unlike other types of primary cell. Just means that you are carting the charging circuit up the hill as well.

The key point is that (unusually) the FT817 is not designed for 12V (13.8V) operation and if you use that sort of voltage then you are wasting a lot of the power you carted up the hill just heating up the FT817 case and potentially shortening its life. Much better to use a three cell Li-Ion or Li-Po battery which produces just about the perfect voltage and offers excellent discharge characteristics that the FT817 works with very nicely. Certainly that’s been my experience with my FT817 and the diminutive, featherweight three cell 2.5Ah Li-Po battery that I use.

Li-Po and fire extinguishers? Well actually any lithium battery can catch fire if it is seriously abused. But we live with them day in day out in our mobile phones, laptops, etc. so it’s a low enough risk provided you’re not being foolhardy.

73, John.

In reply to 2E0KEA:

Hi Timothy, I have been reading these post’s with interest, as I have just got myself an 817 and have done a few activations last week on HF after several years of activating on 2m FM.

I have a 5Ah SLA (I have had it a while) which I used to power my 817, however there is a fair bit of weight in it, and like you, I am trying to decide on the best external battery to use with 817.

There are so many different factors to take into account, with differnt batteries, however my thoughts so far are something along the following:

As different days out activating can vary quite a bit in terms of time spent on radio, I need a solution that will cope with short activations, and long activations.
Ni-Cd, and Ni-Mh batteries seem to operate best when they are regularly cycled, therefore the Ni-Mh battery pack that came with 817 will be used as the primary supply for my activations.
Once the Mi-Mh has been discharged, I will then switch over to a secondary battery.
As some activations will require little or no power from this battery, and others will require a fair bit, I am looking for a battery that ‘likes’ to remain charged or be partially discharged, but is also capable of being fairly discharged for longer days out. The SLA seems to offer these properties, however the big downside is the weight of them.
Lithium-Ion offers the best power to weight ratio and is much lighter than the SLA, and from what I understand they do not need to be cycled often.
The downside seems to be storing them when not in use (see Lithium-ion battery - Wikipedia). It seems to be you want to keep them stored cool, and ideally 40-60% charged as the higher the charge when they are stored the more capacity the loose per year. Not sure on the easiest way to discharge them to this level when not in use.

I am looking at a 4 Ah Li-Ion pack at I am waiting to hear back from them if the charger they sell is 230v.

Other option I am considering is just buying a 3 Ah SLA which will be lighter than my current 5Ah, but will have considerable more weight than Li-Ion.


In reply to GM4TOE:

In reply to 2E0KEA:

I would beg to differ from MM0FMF and G3WGV concerning Lithium Ion

I have used a Li-ion pack (4 cells) for the last 2 1/2 years, it
incorporates its own (RF silent) regulator,

You have exactly what is needed… something to provide a constant output voltage as the cell voltage varies with the advantage it is RF quiet. And yes you can’t get that one anymore. The reports are the current packs have very noisy regulators. So you are fully agreeing with what I was saying Barry.

There was a thread on this reflector about a year or so ago and I know
BVE found an alternative source of Li-Ion packs.

I believe John had a Tekkeon pack. John’s was quiet but someone else reported the same pack as being terribly noisy. A replacement was just as bad which suggests the internal regulator design having changed.

I find John’s (WGV) comments interesting as my own FT817 reports it is not producing 5W when the voltage is reported to be 11.5V. But that is relying on the front panel power indicator flashing. I’m going to monitor the output power as I vary the supply tonight and see what my 817 actually does. The fact remains true that an 11.1V Li pack terminal voltage will drop below the minimum voltage needed by the 817 before the pack is fully discharged. The curves suggest that the pack is only around 65% discharged at this point and the voltage is such that 5W is not obtainable. Of course a 4Ahr pack is a quarter of the weight of a 2.8Ahr SLA and about 3 times the price excluding charger. Even with those limitations, the weight saving may be worthwhile.

Without some kind of regulator in the pack, an 11.1V 4Ahr pack has a usable capacity of about 2.6Ahr and you wont get 5W all the time. But that is based on the published curves and data and in practice things may be very different. Of course we all know the difference between theory and practice is much greater in practice that the difference between theory and practice in theory! :wink:

I did find a circuit for a buck-boost converter on the web last night that is specifically designed for the 817. It runs the 817 at about 8.6V on receive and thus maximises battery life. On transmit the voltage is raised to enable the full rated output to be achieved. As I intend to do ‘some’ 70cms operations this year and will be carrying a 20W PA and 70cms antenna in addition to everything else, a lightweight supply with more capacity is very appealing. Experience suggests a 14.8V 4Ahr pack and regulator should still weight less than a 2.8Ahr SLA with the advantage of considerable more ‘ergs / gramme’.

Interesting stuff. Well I think so!