I would envision a replacement top plate with a battery door.The inside connector could be power pole, or deans or XT60.Leave enough room in the inside plastic/padded tray for the battery, cable and possibly a dongle to convert from one plug style to the other.That's also plenty of room for an 8AA cell holder too.
The toggle switch would switch between internal / external battery power. External power would NOT be used for charging.
This approach should be both lighter and have higher capacity than current SLAB option.
What do y'all think?
72 de Bryan, k0emt
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Specs say the K2 operates on 10-15V, page 2 of the K2 manual online.
Here are my notes for 3S LiPO and 8AA NiMH packs:
Type Vmin Warn Vnom Vmax Vstorage 3S LiPO 9.0 9.6 11.1 12.6 11.55 4S LiPO 12.0 12.8 14.8 16.8 15.4 8AA NiMH 6.4 7.2 9.6 12.010AA NiMH 8.0 9.0 12.0 15.0
So, a 3S LiPO should be just fine. A 4S LiPO with a Vmax of 16.8V would be too much.However, using a smart battery charger, you could cut off charging at 15V.
The 8AA NiMH may not have much operating time before falling below the 10V spec.However, a 10AA NiMH with a peak of 15V should be okay.
On Tuesday, November 27, 2018 8:15 PM, James Doty <[hidden email]> wrote:
I like the idea.
You'd have to add a low voltage sensor though to protect the battery and
radio from over discharge. It would be pretty light too.
That said, the battery only puts out 11.1volts. Will a K2 run on that?
I honestly haven't checked.
For many years I used 3S1 combination using flat cells inside my K2. It was
charged at 12.8V with 1 A limit and the connection to K2 was by a resettable
fuse. Keeps > 11V for about half the charge. Never a problem despite
travelling across all continents. Very light. But I was always afraid that
something would short causing trouble. With batteries with PCB for limits,
the risk is far lower.
I think you would be much better off with a 4S LiFePO4 instead of a 3S
LiPO. Your fully charged voltage would be just under 14 volts, and fully
discharged around 12 volts.
I once found a 4S LiFePO4 battery on Ebay that was almost exactly the same
size as the SLAB that the K2 battery kit included, and fit inside the K2
using the existing battery strap. It worked very well, even using the
original charging circuit. Although it had a balance connector, I found
that the cells were never significantly out of balance using the K2
charging circuit. I made a point not to leave it plugged in to the mains
power supply once the battery was fully charged, but LiFePO4 in my
experience tolerates overcharging time at low currents rather well, unlike
regular LiPO. Having said all that, YMMV and it is always best to balance
charge any Li rechargeable battery with an appropriate balancing charger
and away from the radio or potentially flammable materials, etc. etc. etc.