Soldered up a new spare connector to the bullet-style connectors on these batts.

I'm taking this and nothing else power feed-wise into the woods next time.

I would put a fuse on that.

Awesome! I think the new batteries are really opening up the possibilities for manpack radios.

I've thought about doing the same with a FT-1900 for the ultimate HT, though
haven't completely thought out how to do an antenna that's within safety limits.

Is that a LiPo or LiFePo4? I'm guessing LiPo as the other has way to low a voltage rating.


Let us know how far down you can run the bat and still get good operations.


.....

LiPo 3S  I have run these several times now in the field and I run them from max charge of 12.6 V or so down to where they drop just below 11V on TX at 100W.  They last an hour or so.




RIF!

I said "power feed wise"

I made you a deal and now you're being mean.        



Oh and Mancow, I am not sure of the usefulness of fuse(s) here.  The factory spec wants (2) 25 A fuse (fast blow) and I suspect, based on the location in the wiring (near the radio), those are really intended to provide protection for the easily shorted wiring from the battery to the radio in a typical vehicle installation and not to 'protect' the radio.

That fuse is going to have little chance to protect the radio IMO, as the typical draw for the radio is only about 12 A.  Anything going wrong internally will have already smoked before that fuse blows.  My experience has been using fuses for component protection is impractical, if they are fast enough and sized closely enough to typical expected load to actually protect from high current, they are generally too sensitive and prone to frequent openings.

My experience with industrial components is that in almost all failures, internal to the device, the components internal fuse, or whatever component they have designed to prevent the device burning down, opened long before the fuse inline to the component tripped, if it even did.

This is not to say I am opposed to fusing, I am not, but in general the purpose of the fuse is to protect the upstream wiring, and not the component.  

As I am always going to be staring at the equipment during operation, there really isn't a likelihood of an unnoticed overcurrent situation.  If the radio smokes, I'll see it.  If the wiring shorts (unlikely as it is all connectorized and can't be misconnected), then I will notice.  If the wiring does short, I lose the battery, not the radio.

Honestly I think it is much more likely I will lose the radio because I am operating it outside the spec on the low end (spec is as low as 11.73V, and I run the radio until the display shows 11V on TX) than that I will lose it and have a catastrophic burn-down internally that a fuse would have maybe prevented.  And I think that scenario is pretty unlikely.

How many mAh is that battery? Like the other commenter I've considering doing this with a 2 meter mobile but didn't know about these batteries. That's pretty cool.

Each battery is 5000mAh.

 
My Appologies Good Sir. With the addition of Sleep, I am now a mostly-semi-functioning member of Polite Society.




I was looking at a 4s LiFePo4 for this purpose, as it has a working range of 11.2-14.4V. Yes, a little bigger, heavier, and probably a little more spendy, but I like the voltage range and robustness of that chemistry.




In a nice coincidence, I think the 2s LiPo cells you used to have are about perfect for running a Yaesu vx-150. What an interesting coincidence that I just happen to have a Yaesu vx-150 power brick that had a damaged section of DC cord replaced with PowerPoles.


 

There are no coincidences.

Fusing for a car, yes, fuse in both the + and - wires.

Fusing for anything else, as a base station, portable, etc, just a fuse
in the + wire only.  The - side fuse is not needed.

So based on your explanation you are only getting 30-40% of the actual battery life from that cell, assuming a 2C draw curve, and its actually more like 4C on TX.

11V/3 = 3.6V, which is actually the nominal voltage of the battery. Will going below 11V damage the radio?  



I like the 3S batteries for my FT817, but I run them down to about 9V which is fine for the FT817. That or I use a 4S LiFePO4 to run the amp which requires are more stable 13.8V, but the 4S LiFePO4 batteries are far better matched for ham radio use, even though they are heavier.

When comparing the LiFePO4 cells to LiPo for ham radio, you really don't care about the current you can pull, which is the main advantage of the LiPo vs the LiFePO4 cells. Weight wise the LiPo is a bit lighter but not dramatically so. Consider a 4S 4.2Ah LiFe PO4 at 558g vs a 4S LiPo (517g at 4.5Ah) Yeah its ~7% heavier than the LiPo, but it is a far better voltage match for a radio that needs ~13.8V +/- 15% across the whole discharge range. Anyhow, just some food for thought.

I dunno.

I chose 11V on TX somewhat arbitrarily.

I am sure the batteries have plenty of life left at that point, but honestly I cannot picture an activation where I need more than 2 hours of talk time at 100W.

So the batteries should last forever and are giving me what I need, it's all good.

I will try running them down a bit further next time, and see if power falls off or not.

I'm fairly interested with what voltage will damage the 857/897 series. Specs list 13.8+/- 15% voltage wise. So 11 is starting to get out of that range.

Quite so.

I take the spec to allow 11.73V on the bottom end.

IIRC, I selected the 11V TX threshold by watching the RX voltage and checking for when it crossed 11.7 or so.

I'll run a battery down that far and hook it up to the dummy load with the watt-meter inline and see what's happening.

I do like the idea of only discharging to what is essentially storage voltage.

 
That is definitely a recipe for long battery life and fast recharges.

Yeah but he's getting maybe half the runtime he could if he used a better matched battery voltage. And risking radio damage. Some folks are using a voltage regulator and 4s lipos for these purposes.

Looking at the FT817 specs I suspect the 857D is the same, as they both list the same 13.8 VDC +/-15%.  The 817 goes on to note "Operating: 8.0-16.0 V, Negative Ground" which is clearly NOT the same as 13.8V +/-15%.

I will check the charger I have though, if it can do LifePO4 I may get one and try it.

Thanks for the info Harlikwin!

The 817 will work down to 9v and 16v will kill it (yay ask me how I know not to use a 4s lipo with it)
The 897 I have wont work at all at 9-10v (no power on). And I'm not gonna tempt fate with it. Compared to my mil packs the yeasus are fragile and finicky beasts.

The 857D and a 3S at just over 11V are still outputting 90W into the dummy.

I will continue a drain down test and check output power key down from time to time.

If we get to key down function at 9V I will stop the test.

Still good at 10.4 V key-down.

Cool. Keep going!

10.4V?


I like the sound of this.




Maybe the only practical difference between the 817 and 857 is the final amp section?




What happens if you drop the power setting down? Does the output vary by a stable percentage across power settings, or does the power output match the setting until you hit a certain power level?


 

OK, here's the end results.

At 9V the battery simply dies.  You can key the CW and watch it fall from 70W or so.

Changing to 20W output power it just changes the rate of depletion as you watch the needle drop.

SO...important test facts.

-the radio doesn't explode even down to 9V
-the power doesn't fall off until you approach 9V on the battery...which matches Harlikwin's charts above.
- I had to periodically stop TX just to let the dummy load (a fruit-jar filled with resistors) cool down

The takeaway is I will now plan to run these batteries down much closer to their discharge levels in the field...probably switching to 10V on TX as a threshold.

In other news I am now testing a magnetic mounting method for my bulldog keyer to the 857D chassis.

Hm.. I'm gonna have to try this again with my 897. I did my original tests with a different battery chemistry.