First experience with lifepo4 AAA cells

First experience with lifepo4 AAA cells These cells give abut 3.47 V when full, so if you have a device that uses 2 normal AAA, then you can use one of these and a dummy (read shorted) battery for the other. You will have more voltage, but less capacity, but a lot more recharges (about 2000). I have got these small AAA lifepo4 and they state 200 mAh, a lot less then the 750 or so on a normal AAA eneloop.

Charge voltage with current limit at 3.5V set to 1/2 C. Discharge low voltage cutoff should be set higher, equipment must be able to handle the 3.45 V versus 2 x 1.2.. Full 200 mAh AAA on 180 mA load drops to 3.05 V here. Same at 120 mA load, strange Ri. Anyways Once of these runs my gamma spectrometer for an hour, versus 2 AA nimh for 8 hours...

So where should I use these batteries... if space and safety constraints perhaps.

Reply to
Jan Panteltje
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First experience with lifepo4 AAA cells These cells give abut 3.47 V when full, so if you have a device that uses 2 normal AAA, then you can use one of these and a dummy (read shorted) battery for the other. You will have more voltage, but less capacity, but a lot more recharges (about 2000). I have got these small AAA lifepo4 and they state 200 mAh, a lot less then the 750 or so on a normal AAA eneloop.

Charge voltage with current limit at 3.5V set to 1/2 C. Discharge low voltage cutoff should be set higher, equipment must be able to handle the 3.45 V versus 2 x 1.2.. Full 200 mAh AAA on 180 mA load drops to 3.05 V here. Same at 120 mA load, strange Ri. Anyways Once of these runs my gamma spectrometer for an hour, versus 2 AA nimh for 8 hours...

So where should I use these batteries... if space and safety constraints perhaps.

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Change the battery holder wiring to parallel instead of series and put a second lifepo4 cell in there to get double the capacity, instead of just wasting that space with your dummy cell. I know that charging and discharging in parallel isn't optimal, but it's not that bad, is it?

----- Regards, Carl Ijames

Reply to
Carl Ijames

On a sunny day (Wed, 6 Aug 2014 15:27:57 -0400) it happened "Carl Ijames" wrote in :

lifepo4 has very low internal resistance, some form of current limiting would be required, also protection for putting one in the wrong way around!

Reply to
Jan Panteltje

On a sunny day (Wed, 06 Aug 2014 20:05:26 GMT) it happened Jan Panteltje wrote in :

PS, but you could add 2 Schottky diodes to get the voltage to normal level, prevent disaster if one battery wrong way around, and cause current equalisation.

Reply to
Jan Panteltje

I use the AA ones in my Apple Bluetooth Magic Mouse. Apple BT keyboard doesn't seem to like them. The capacity even at AA is pretty poor, but at these very low drain currents I'm not entirely unsatisfied. I can't imagine wanting to use AAA though.

Clifford Heath.

Reply to
Clifford Heath

For Li based cells, parallel operation is not a problem at all.

The voltage on these cells changes considerably with charge state, so they will remain nicely balanced.

Also, the full charge determination is a simple voltage limit, so there is no risk of over charging one cell.

Of course, the cells must be equally charged before you connect them. If you connect one fully charged cell and one discharged together, there will be an uncontrolled and possibly destructive current flowing.

--
RoRo
Reply to
Robert Roland

On a sunny day (Thu, 07 Aug 2014 12:36:29 +1000) it happened Clifford Heath wrote in :

Yes, would that mean the bigger physical the battery is, the more the advantage? Self discharge is pretty good too, but so it that for eneloop. These lifepo4 seem better at higher temps.

Reply to
Jan Panteltje

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