Kenpro KT-22EE 2M Handheld Battery Query

[Damo666]

I've just found a box of 5 x Kenpro KT-22EE HT's in my Mother's loft that I'd completely forgotten about from the many years ago.

In the box are several Batteries that all fit onto the rigs - some unmarked & short, some longer marked "CTE CT1600" - all Batteries have a 13.8V charging jack socket on them, however, there's no indication of Battery capacities (mAH) making it difficult to know what rate to charge the packs at.

A bit of a long shot - but can anybody shed any light on what capacity/Voltage these packs are, or has anybody got the instruction manual laying around with the relevant details, please?

[SiriusHardware]

Hello Damo, are these ultrasonically welded together (as they typically are) or are they screwed together (as some Icom packs were, early on)?

If you can easily get one apart have a look to see if there is any sort of current limiter built into the pack.

This could take the form of-
-A large resistor
-A little PCB with a proper constant current circuit built on it.

If you find that the wires from the charging socket on the pack go straight to the + and - terminals on the battery array, you will need to arrange some kind of external current limiting circuit. You'll also usually see some kind of metallic 'thing' in series with the cells and either buried inside the pack or stuck to the pack. This is not a current limiter, but a thermal fuse, designed to go open circuit if the pack gets too hot for any reason..

The fact that these packs are designed to run from 13.8V (ie, typical in-vehicle voltage) makes me almost sure the current limiting is built in to the packs, and you can just charge them from 'direct', unlimited 13.8V. However, it will probably still be up to you to decide how LONG to leave them on charge for. The original instructions probably advised charging them for up to, but no longer than, 'x' hours.

The age they are, the Nicad(?) cells will all be fairly dud by now so you'll probably have to consider taking a couple apart to re-cell them in any case.

[Damo666]

Hello, Sirius, long time no speak - & hope you're well.

I'm in bed just now, but I'll have a ganders at the Battery construction sometime later today.

I'm pretty sure I've seen little Philips screws on both the top & bottom on the packs, so they maybe open to be re-celled. We'll see.

I'll return later with my findings, but in the meantime, many thanks for the reply.

[Martin G7MRV]

My first radio was a KT-22! As I remember it, the current limiter was a resistor inside the DC plug!

The packs were not very highly rated, somewhere in the 500-700mAh region.

If you decide to dispose of these radios, you could send one my way! ;-)

(mine was stolen off my belt in Doncaster market place :-( security wasnt a high priority for me aged 14!)

[G6Tanuki]

The batteries will almost certainly be "AA" and if they've been left unused for long they'll almost certainly have died.

My experience is that it's relatively easy to re-cell the older handie-talkie battery packs: in the 1970s/1980s they hadn't yet got into the annoying habit of laser-welding the housings on the things together - if you find getting into the pack difficult it's ikely they've used hot-melt glue to hold the halves together: a good blast with a hairdryer can often help getting them open!

NiCd is really obsolete technology these days: for near enough the same price you can get NiMH cells which pack a lot more 'oomph' into the same space.

[I'm in the process of re-celling a Yaesu pack right now: a sharp knife split the laser-welded halves and the old 700mAh nicads are to be replaced with 2000mAh NiMH just ordered from RS. £20 or so - which is good value compared with an 'official' 700mAh one from a Yaesu dealer at £33 +VAT! ]

[Damo666]

So, I got around to opening one of the Battery packs and I managed to establish that the pack is 8.4V at 250mAH.

The pack was was completely sealed, and the only way of getting into it was with brute force, a cigarette lighter and Stanley knife as I didn't have access to a hacksaw or dremel cutting disk, etc.

As soon as I cracked the pack open - wires fell off the charging circuit, but from what I can establish with my limited knowledge, it looks like current limiting is done via 2 x 180R Resistor's in Parallel with the Diodes either end preventing the pack discharging into the charger source.

[G6Tanuki]

8.4V would correlate with seven 1.2 V NiCd cells, I;m guessing that each of the cells shown in your photo is actually two half-sized ones end-to-end in series, which would give eight cells. Perhaps they're assuming a bit of voltage-drop in one of the diodes?

The 'charge circuit' looks pretty simple: as well as a diode to stop the cells discharging back into the charging source you may find a diode to prevent connection of a reverse-polarity supply.

Is the red thing next to the 100uF capacitor a LED to indicate that it's being charged?

[Damo666]

G6Tanuki,

Yes, that's a Red LED in the middle of the PCB next to the Capacitor that lights when a 13.8VDC charger is connected.

I've managed to find a small adaptor that outputs 13.8VDC at 60mA - so am I right in thinking that I should charge one of these packs at say 5 to 6 hours taking into consideration charging inefficiencies?

This would offer the 250mAH pack 300 > 360mA.

[Damo666]

Originally Posted by Martin G7MRV

If you decide to dispose of these radios, you could send one my way! ;-)

(mine was stolen off my belt in Doncaster market place :-( security wasnt a high priority for me aged 14!)

Martin,

I'm probably going to hold on to them for a little while, but when I decide to get rid of a couple I'll keep you in mind & give you first refusal.

[G6Tanuki]

Traditionally for NiCd battery-packs you charge at 1/10 of the pack's rated amp-hourage, so for a 250mAh pack you would charge at 25mA.

But you charge for 1.4 times the pack's capacity - so if you're charging at 1/10 of the amp-hourage you charge for 14 hours.

From the look of it - and from your own admission that it's not been used for years - your battery is well-and-truly-dead so don't bother trying to charge it until you've re-celled it!

[SiriusHardware]

Damo, can you confirm these are half-length or 2/3 length AA cells? They do look it.

If they are full length AA I can probably harvest some flat rows of three and flat rows of four from some five-cell NiMH packs which we use at work - that's how I re-celled the seven-cell packs for my Icom IC-H10s - but they won't do you any good if the cells in your pack are less than full AA length.

I think your analysis of the limiting circuit is correct, so, once you have a pack reassembled with new cells inside you should be able to charge them from a current-unlimited 12V or 13.8V supply. The little circuit inside the pack will do the current limiting.

[Damo666]

Sirius,

The dismantled pack is now downstairs & ready to be disposed of, but if I remember right, they look like 1/2AA size. I'll compare them to my AA Eneloops later today - but I'm very grateful for your kind offer.

I went against your advice, G6Tanuki; I put one of the packs I have on charge (in a LiPo bag) using the 13.8VDC 60mA charger I have, and by using another Jack terminated with wires plugged into the pack charger port & using my multimeter in series - I measured just short of 50mA being drawn. I placed the pack on charge for just over 6 hours & when I disconnected the pack, it measured a respectable 10.15V so maybe I've got lucky and all cells are OK as this suggests about 1.45V per cell.

I've left the pack resting overnight, so hopefully it'll retain good voltage, We'll see.

Hopefully one or two more packs will be good to go.

I'll report back later today.

[Damo666]

Unfortunately, I'm a bit too late to edit my previous post - but a voltage check on the pack this morning reads 9.58V.

I'm going to attach the pack to the rig & see how it goes.

[Martin G7MRV]

All looks familiar now ive seen your photo! Not sure where I remembered the resistor in the DC plug from! (but it was 28 years ago!)

[Damo666]

Martin,

I know it was a long time ago now, but can you remember what the Battery life was like on yours using the supplied pack.

I just tested the pack I charged last night and got just 4 hours on RX. Two of those hours were mainly squelched with occasional activity, the remaining 2 listening to a contest. The set was mid volume.

[SiriusHardware]

That sounds quite short, although 200-300mAH is very low capacity even by the standards of older radios. I think my first amateur handheld (1994) had 600mAH packs, and even that is dwarfed by the capacity of more modern cells.

Old Nicad batteries do eventually stop working altogether, but before they get to that stage they lose their capacity, the maximum amount of charge they can hold.

In addition they may go high impedance so they seem to rise to a high voltage very quickly when charged, but the voltage will decrease rapidly again when they are subjected to any meaningful sort of load.

Another thing which often happens (although not in your case) is that one cell in a pack goes short-circuit, permanently reducing the available voltage from the pack.
.

[G4YVM David]

I used to work for ray withers and we flogged these sets. We used to also sell a suitable empty battery case...the exact same one as we sold with Nicads, just empty. We called it the MT1. Ho Ho. Anyway it was thennup to the owner to pop in drycells which have a higher voltage, so I imagine your radio will handle 10.5 v okay. It was a long time ago. I loved mine. Is this model the decade rotary switches for frequency?

David

[Martin G7MRV]

Originally Posted by Damo666

I know it was a long time ago now, but can you remember what the Battery life was like on yours using the supplied pack.

I just tested the pack I charged last night and got just 4 hours on RX. Two of those hours were mainly squelched with occasional activity, the remaining 2 listening to a contest. The set was mid volume.

That is short, but it might improve with a few discharge/charge cycles to bring the battery back to condition.

If just monitoring S20, i would get at least a day out of it. Although im sure my battery was a bit higher capacity

[Damo666]

Sirius,

A bit of research on Google found a spec' for this rig, albeit in Italian, and it states that it draws 18mA on RX squelched, and 130mA full volume RX - so all things considered, I think my 250mAH pack is doing about right since the final 2 hours were mid volume and with virtually constant chat.

I have a few higher voltage packs here that are nearly twice as long as these smaller packs, so hopefully they'll be higher capacity like the 600mAH packs you refer too.

David,

One of those empty packs that accept AA cells would be ideal, and I'm in the process of messaging an eBay member about one that looks like it may be compatible with mine by the couple of images he's hosted.

It'd save a lot of hassle, and that way I could use my trusty Panasonic Eneloops and have a good couple of days use in between charges.

Yes, it's the unit with rotary dial switches on top that covers 140 > 150 Mhz with a few switches recessed on the rear.

Martin,

I've got some larger packs here, so hopefully I'll see some more longevity on the standby time on the proviso they take a charge.

[ex seismic]

it states that it draws 18mA on RX

Ah, the good old days before power hungry microprocessors etc.

Gordon
G7KNS