BMS in my LiFePo4 battery
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Oops!
I stopped using the monitor. Using the smaller battery with the KX2 and the larger one with the ft-857d, Iāve always got cold, bored or run out of time before there was any risk to the battery!
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yeah me too. I had a switch inline with the LifePo4 in a case containing the IC-705 but forgot to flip it once. Now I physically pull the plug so there is no chance of that switch being accidentally flipped. I still have two of the 4200s remaining.
Mark
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The 270 /P dream:
Reality when calling CQ on 270:
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I had a dig about on AliExpress and could not find any 4S LiFePo packs there were plenty of 3S LiPo packs. Iām trying hard to remove LiPo technology from my gear as itās more of a fire risk than LiFePo so I donāt intend to buy any more 3S LiPo packs.
The old FT817/818 is a bit of a babe when it comes to voltage, it happily gives its all from a power supply of about 10.5V up. This makes it ideal on a 3S LiPo.
KX2 will give 10W from a fully charged 3S LiPo but as the voltage drops (LiPo does not have a flat discharge curve) the power on 10m/12m drops. Typically you see 10W on 80-15m and 7-8W on 12-10m. I assume KX3 is similar.
The IC705 is annoying. 5W is no problem from the built-in LiPo but you need a good 12V or more to get 10W. If the voltage drops below 12V (maybe 11.5 or 12.5) then it switches back to 5W. This is annoying, as it should be able to give a power that is a function of voltage. i.e. starting at 10W and dropping off as the voltage drops. But it switches back to 5W when it could do more. Grrr!
IC706/FT-857 like to see a higher voltage. Doesnāt like lower voltages from 3S LiPo.
There are a plethora of QRP radios that work well on 8-13.8V like QCX and Altoids radios and Mountain Hoppers. The QMX and QDX want 12V not 13.8V.
I donāt know how well the various Xiegu radios or the TX-500 work on varying voltages.
The result of this is when using my KX2 / QCXs I can use a variety of packs with no worries. But for the 705 I do want to have a LiFePo4 pack.
For people in mainland Europe there are the packs from Eremit. These are a range of LiFePo4 packs from 2Ah to 6Ah. Mine is a 4Ah made as 4S2P with BMS. The problem is Eremit only ship to Germany but there are some companies in Switzerland, Germany and Austria carrying the product. I donāt know how easy it is to get them in other mainland countries but UK is not an option.
I try to keep on top of what is available. Iāve made packs out of 3x 18650 LiPos, these cells are easy to obtain. Remember the very high capacity cells are probably āoptimisticā regarding capacity. i.e. itās a lie! I think more than 2500mAh per cell is probably not happening no matter what it claims.
I did buy a number of surplus 26650 LiFePo4 cells. They were nominally 2500mAh but these were older and running around 2300mAh. They were ex e-bike packs so can provide 50A (but not for that long) so they are heavy but a number of activators in the Edinburgh area have them working. A 26650 battery holder and BMS lead was a few pounds.
Hereās the prototype. I used it recently on GM/NS-117
There are a zillion suppliers of 26650 3500/4000mAh cells on AliExpress Using new 26650 cells you can make a pack up for not too much. Not sure how they ship them to you 
So there is a way forward if the RC LiFePo4 packs remain unobtainium.
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Reliable on 9-15v with power dropping to <6w as you go down in voltage. Powers off at 9v but Iāve generally started to miss my other 3dB by then & swapped batteries.
So not recommended for fully charged 4x Li but good for most of discharge range of 3x
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