[time-nuts] HP 105B: Modern replacement for NiCad battery pack?

[Van Horn, David]

Memory... :)

I've induced the "memory effect" in NIMH cells and Nicad, and lead acid.  Simply charge to the same point, then discharge to the same depth of discharge about 10x.
In the next cycle, discharge completely and you'll see the bump in pack voltage where you had discharged to previously.
Now charge and discharge again and note that the vaunted memory effect is gone.

In real use, you are highly unlikely to charge and discharge precisely to the same point that many times.
NASA uncovered this in testing batteries for satellites (very special NICAD batteries) where due to solar cells and orbital mechanics, plus very consistent loads, they were seeing the problem.

Normal use, where the pack is discharged to different points (a few percent different) is all you need to prevent this.



-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Brooke Clarke
Sent: Friday, January 5, 2018 11:48 AM
To: Ulf Kylenfall via time-nuts
Subject: Re: [time-nuts] HP 105B: Modern replacement for NiCad battery pack?

Hi Ulf:

There's another problem with switching to Ni-MH and that's related to the heat generated when charging them.  You can charge Ni-Cad batteries without monitoring the pack temperature, but with Ni-MH cells you must monitor the pack temperature.  I would suggest avoiding the Ni-MH option.  Either:
1. Just use modern Ni-Cad cells, no memory and much higher capacity, no change to the charger, or . .
2. Update to one of the Li-xxx chemistries with a totally new charger.  These batteries have much lower self discharge rates and higher energy density.

--
Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html

-------- Original Message --------
>   
> Gentlemen,
> I may have asked this question before...
> I am looking for a modern replacement for the NiCadbattery pack used in the HP 105B. One such 105that I salvaged have been standing on a shelf with thebatteries "happily boiling away".
> So, what kind of chemistry would be possible to usewithout to much re-design of the charging circuitry?
> Ulf Kylenfall
> SM6GXV
>
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