[time-nuts] HP-105B Battery Replacement?

Jeremy Nichols jn6wfo at gmail.com
Thu Sep 15 14:04:09 EDT 2016

Brooke, I priced Ni-Cds and was not happy with the numbers: a set of 20 
D-size cells will cost me ~US$100 by the time I get them delivered. That 
plus the 8-pound weight penalty makes replacement Ni-Cd cells 
unattractive. (105A = 16 pounds, 105B = 24 pounds including the battery 
box and charging circuitry) There is no question that Ni-Cds are the 
answer for anyone attempting to restore a 105B for competition in the 
neighborhood Concours d'Elegance.

I do appreciate your work on the relative merits of the various Lithium 
types. I was afraid the existing charge circuitry in the 105B would not 
mate well with Lithium-anything batteries. Having twice set the house 
afire through assorted misadventures (thank goodness for smoke alarms 
and fire extinguishers),  I don't want to try for "Number 3".


On 9/15/2016 9:59 AM, Brooke Clarke wrote:
> Hi Jeremy:
> I'm currently having fun playing with various rechargeable battery 
> related stuff  which includes Li-Ion cells.
> http://www.prc68.com/I/BatTst.shtml#Resistor
> The cells come in three configurations:
> 1. the raw flat top cell with optional tabs to allow easy soldering 
> into a pack,
> 2. cell plus positive button cap which includes a Positive Temperature 
> Coefficient (PTC) fuse and an over pressure vent,
> 3. fully protected, like 2, plus circuit that turns off the battery if 
> charging and over voltage or loaded and under voltage. On these you 
> can feel a wire/ribbon running from positive to negative under the 
> shrink wrap and they are slightly longer.
> These configurations are independent of the flavor of Li chemistry.
> To go with any of the above you need a charger specific to the 
> particular Li chemistry (the charging voltage is not the same) and if 
> a pack you also need a either cells like 3 above or a protection 
> circuit for the pack.  For optimum performance in addition a tap 
> between each virtual cell (made of of parallel cells) so that the 
> charge can be balanced and a charger that can do that.  This is not 
> easy, witness the current recall of the Galaxy Note 7s phones.
> I would just use modern Ni-Cad cells mainly because of the ease of 
> charging and maintaining them and use the existing charging circuitry.
> Li chemistry has advantages for portable equipment, but not so much 
> for rack mounted equipment.

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