In reply to G4OIG:
I’m not doing surgery on a couple of 2S packs to split them in two… for
obvious reasons!
Coward! 
I waiting for the latest update from Phil to see if he has found out anything more.
Andy
MM0FMF
In reply to:
As an alternative to using diodes to drop the voltage, you could also use a power mosfet type regulator.
There is an example circuit in the RSGB technical topics scrap book page 201. The circuit needs to be improved by picking a device with a much lower on resistance and increased current rating, but this is not difficult.
I did start experimenting with the above and it worked well, but I now just run my ft857d and Ic7000 directly from the 4S packs.
Regards,
Nigel. G6SFP.
In reply to G6SFP:
Hi Nigel,
I was hoping for a KISS solution. Basically to set up and operate, so the mosfet idea has a distinct advantage over shorting out diodes. There’s enough to do on a summit without checking voltages and moving power leads across.
It is interesting that you are using your 857 from the 4S packs direct - does this indicate that there is an issue with Phil’s 857 I wonder? Over to you Phil - we all wait with bated breath for the next instalment in this saga!
73, Gerald
In reply to G4OIG:
What we need is a nice simple circuit that monitors the voltage and when it falls to a certain value shorts out the diode!
73
Brian G8ADD
In reply to G8ADD:
… or switch to LiFePO4 cells. They’re almost as light as LiPo but don’t have such a high terminal voltage. I see the A123 2.3ah cells are now readily available in the UK. One of these 4S packs powers my FT-857 at 50W for a good 45 minutes on ssb.
Oh, and they’re also easier to charge. I charge mine on a current-limited bench PSU just like SLA - but at a different voltage.
73, Richard
In reply to G4ERP:
The technology is still expensive so I’m afraid I’ll have to continue to live dangerously! 4 summits worth would require the best part of £200, but then I recall a single 4AH LiPo was well in excess of £80 not so long ago. Let’s hope the technology catches on!
73, Gerald
In reply to G4OIG:
Afternoon.
Maybe you don’t need that many packs - but I see what you’re saying.
Some chargers (like my Kokam units) will do either type of Lithium technology so recharging from a 12V jump battery inbetween activations is a possibility - the cell spec allows for a fast charge at 10A.
73, Richard
In reply to G4ERP:
Maybe you don’t need that many packs - but I see what you’re saying.
With an appropriate charger I could charge LiFePO4 cells safely in the accommodation overnight, but would not want to do it with LiPos. I do now trust them on my slow charger (0.2C) at home sufficiently to leave them alone in the Utility, but I certainly would not sleep in a room with them on charge. Seems like I could probably get away with a pair of LiFePO4s, but that’s still a healthy defecit on my bank account! I guess it is all down what one expects to get for one’s finances.
73, Gerald
Dear All
IT’S NOT THE FAULT OF THE LiPo BATTERIES.
The overnight temperature fell to -6c in my garden and this allowed me to run some tests with the FT-857 and the 4S1P 14.8v-16.7v LiPo’s.
I now know that there is either intentional or accidental overvoltage protection built into the FT-857. This ONLY comes into play at lower temperatures when the voltage supply is high and the radio will not then turn on.
I had one 4S1P stored inside my shack at 16c and one outside with the radio at -6c temperatures in a fabric bag wrapped in plastic. Both LiPo’s at 7.00am this morning showed an identical 16.7v being previously fully charged. The FT-857 once again would not turn on. In fact after leaving the radio in room temperature until I went out walking at 1015am it would still not turn on at that voltage. It turned on without problem using the SLAB at 12.5v.
When I returned home at 3.30pm the radio turned on with the 4S1P LiPo after being at room temperature for several hours.
So, nothing wrong with the LiPo’s - it’s the radio. I either need to build a circuit using a zener diode to drop the voltage to 13-14v I guess or sell those LiPo’s and buy some 3S1P 11.1V jobs. I already have one of those on order from Hong Kong anyway.
Mystery solved…
73 Phil
In reply to G4OBK:
Big series diode Phil. That will drop the voltage by 0.9V.
Andy
MM0FMF
In reply to G4OBK:
…and buy some 3S1P 11.1V jobs. I already have one of those on order from Hong Kong anyway.
Beware the low voltage syndrome Phil: distorted mod and fuzzy CW (as you have witnessed yourself). I will be interested to see whether your 857 suffers like mine does as the 3S battery levels out at 11.1V.
Thanks for solving the main issue. I’ll bear that in mind if I ever go to 4S batteries. In the meantime I await delivery of some 10AH NiMH D cells to boost my existing 3S LiPos. Hopefully next time out I’ll remain intelligeable… what did I hear someone say? - “That would be a first!”
73, Gerald
In reply to G4OIG & MM0FMF
A further test completed.
I dropped the voltage of the 4S1P LiPo to 15.4v by using it. Temp overnight was again -6.5c. Tested this morning with the stone cold radio and battery and no problem - the rig will turn on. I guess I need to drop the voltage of the LiPo’s to 15v on full charge to be sure the 4S1P batteries are compatible with the FT-857. Andy’s suggestion of a drop of .9v by using a diode may not be enough.
I note your comments Gerald regarding the 3S1P types - I’ll give the one that is on it’s way a try and see what reports I get. Probably trying it on one of the nearby TW summits. Some op’s I know (G4YSS for one) uses two of those in parallel.
73 Phil
In reply to G4OIG & MM0FMF
A further test completed.
I dropped the voltage of the 4S1P LiPo to 15.4v by using it. Temp overnight was again -6.5c. Tested this morning with the stone cold radio and battery and no problem - the rig will turn on. I guess I need to drop the voltage of the LiPo’s to 15v on full charge to be sure the 4S1P batteries are fully compatible for use with the FT-857. Andy’s suggestion of a drop of .9v by using a diode may not be enough.
I note your comments Gerald regarding the 3S1P types - I’ll give the one that is on it’s way a try and see what reports I get. Probably trying it on one of the nearby TW summits. Some op’s I know (G4YSS for one) uses two of those in parallel.
73 Phil
In reply to G4OBK:
Hi Phil,
Thanks for all you battery tests. Very interesting. I have been using an encapsulated (old) bridge rectifier block, with it’s diodes configured in a series parallel arrangement, and have had no problems with the 857 running from my 4SP packs, under winter hill conditions (yet!). I do remove the Diodes, usually on my second activation of the day from the same battery pack.
I believe John (YSS) uses an Icom IC-756 on activations, so may have a more voltage tolerant rig.
Good to know your batteries are ok.
73,
Frank
In reply to G4OBK:
I too am using a bridge rectifier block (40A rating) in a series/parallel arrangement for use with my FT-857. Under load there is approx a 1.5 volt drop.
73
Robert
G0PEB
In reply to G4OBK:
Hi again Phil,
I have a spare, wired up, diode block which I have no use for. If you have a use for it, I will post it to you.
73,
Frank
In reply to G3RMD:
Hi Robert / Frank
That diode block sounds man enough - super. If you can send me your spare one Frank I will reimburse you by buying you a drink whenever we meet up. The volt drop given by Robert’s diode is perfect. I am QTHR in QRZ.COM and callbook.
73 Phil
In reply to G4OBK:
Hi Phil,
I’ve recently posted a photo of the diode block on flickr.
73
Robert
G0PEB
In reply to G0PEB:
Thank’s Robert - I’ve checked out the photo. I’ll probably use 4mm plugs/sockets on my set up as that is what I have now. Red to Red Black to Black hi hi!
73 Phil
In reply to G4OBK:
Red to red and black to black is not quite enough if you have sweat running in your eyes, as I found out. Now I use a non-reversible plug and socket!
73
Brian G8ADD