Has the k2 a future - not if you use Li-Po cells!

[Greg VK3VT]

Hi Guys
I have a mate, Ian VK3FFLY, who is into flying radio controlled models
using Li-Po cells and they are very careful about the way they charge
them - always in a metal box (not the radio cabinet!). Several of them
have had fires from charging these cells. Ian suggests you have a look
at http://www.rcgroups.com/forums/showthread.php?t=209187

Ian's son-in-law had a house fire in the last couple of months from a
charging Li-Po - luckily he was home and the smoke alarm worked so he
just had damage to the one room.

Greg VK3VT


Subject:
Re: [Elecraft] [K2] Re： has the k2 a future?
From:
"Leigh L. Klotz Jr WA5ZNU" <[hidden email]>
Date:
Fri, 16 Oct 2009 11:15:58 -0700 (PDT)

To:
[hidden email]


Johnny,
Do you have pictures posted?   I remember when you started this project and
I'd like to see how it worked out.

Presonally I lean more toward LiFePO4; although they have a lower energy
density than the Li-Po (though higher power density) they reportedly are
safer in conditions of over/under charge and mechanical stress.

Leigh/WA5ZNU

Johnny Siu wrote:

>
> Hello Wayne,
>
> Yes, K2 is still my favourite field day and QRP rig and no others can bit
> it.
>
> I now have 3 x 3.7v 3300mAH Li-Po cells in the KBT2 and they work very
> well.
>
> 73
>
> Johnny VR2XMC
>

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[AD6XY]

This is why I eventually decided to use AA NiMH cells instead when replacing the lead acid battery in my K2.

I use 10 AAs in a pack, this gives me 2.5AH vs ~3AH for a small LiPo pack of similar mass. The LiPOs are fine but I will keep them outside the case so I can throw them somewhere if a fault occurs. I am sure computer packs are fine but I am wary of the RC type packs. The advantage of NiMH is they are easy to charge. They may fail faster but they are very cheap to replace.

Mike

[Julian, G4ILO]

AD6XY wrote

This is why I eventually decided to use AA NiMH cells instead when replacing the lead acid battery in my K2.

I use 10 AAs in a pack, this gives me 2.5AH vs ~3AH for a small LiPo pack of similar mass. The LiPOs are fine but I will keep them outside the case so I can throw them somewhere if a fault occurs. I am sure computer packs are fine but I am wary of the RC type packs. The advantage of NiMH is they are easy to charge. They may fail faster but they are very cheap to replace.

Why didn't Elecraft choose NiMH cells for the KBT2 in the first place? There must have been a reason.

[Leigh L. Klotz Jr WA5ZNU]

Julian, G4ILO wrote

Why didn't Elecraft choose NiMH cells for the KBT2 in the first place? There must have been a reason.

One reason might be self discharge; SLA stay charged longer than NiMH.  There are new longer-life NiMH cells these days, though.  And the LiFePO4 and Lithium nano-phosphate cells as well.
Leigh/WA5ZNU