NiZn Support

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Mark
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Posts: 417
Joined: Sun Jul 28, 2013 6:47 am
Location: Brisbane, Australia

NiZn Support

Post by Mark » Thu Oct 24, 2013 12:52 am

NiZn support was added with version 0.514 of the firmware and I've made a heap of improvements to their support with 0.516

A few notes for those wanting to charge/test NiZn cells:
  • I think it's better to charge NiZn cells at the fastest rate possible - I suspect that charging them at the lower rate (where the charger is only charging 50% of the time) is likely to cause them to be overcharged. NiZn cells can't tolerate overcharge like NiMh cells do.
  • If a NiZn cell is discharged (resting voltage is under 1.70 V) and the internal resistance is higher than normal (over 90 milliohms) the charger won't detect it as a NiZn cell. If the voltage is above 1.44 V, it will reject the cell as being fully charged. You can still force charging of the cell by setting the mode position to charge and hold the push button for at least 3 seconds. Once the cell has been charged enough for the resting voltage to sit above 1.70 V, you can then stop the charge and put it into a different mode if you wish to do so.
  • It's possible to adjust the above voltages so that NiZn cells are detected correctly even if their voltage is low and resistance is high, but this then runs the risk of not rejecting alkaline cells.
  • If the starting voltage of a cell is above 1.70 V it will be assumed to be a NiZn cell and the discharge cutoff will be adjusted to 1.30V This will prevent you from being able to do a full discharge on lithium primary cells, although I think they're also mostly empty by 1.30 V as well.
  • There is a risk with these changes that lithium primary cells may not be rejected and instead charged as NiZn cells. Lithium primaries are relatively rare compared to alkalines so I don't think this is too much of a problem, but it's something to be aware of if you do use them. Lithium primaries are definitely not rechargeable - they could well explode if recharged!

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