Roper ZAP PK Xero Existence Log for 2010

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lithium batteries,

1 January 2010

Before Christmas last year we had about two weeks of below 20-degrees weather. I had the 12-volts auxillary battery on a trickle charger. One warmer day I decided to check the LiFePO4 batteries for voltages. One of the puffed batteries (#25) had only 0.25 volts! Also, one of the non-puffed batteries (#24) had only 0.18 volts! All others, including the other two puffed batteries (#3 & #26) had between 2.95 and 3.2 volts. The question is: Is there a current-leakage path from the traction batteries through the vehicle frame? I have not been pushing the red-button cutoff switch when the vehicle was not being used. From now on I shall.


I bought a Velleman HPS10 hand-held oscilloscope to use to try to find if the traction system is sending voltage spikes through the battery pack. There is some suggestion that such a spike could be amplified through the long lead from the controller to the most negative battery (battery #26).

15 January 2010

It got warm enough this afternoon for Chris Roberts, my electrician friend, to help me do some testing on Sun Roper. We put it on stands so that the traction system could be run. The bad news: When the cutoff switch is on, a wave form was measured across each battery:



It was about 0.4 mV trough to peak and about 21 microsec from peak to peak.

The good news: It went away when the cutoff switch was turned off! Also, we saw no change in it when the traction system was running.


My conclusion is that there is current leakage through the different paths of the chassis, whose capacitance and inductance is creating the wave form, but only when the cutoff switch is on. I interpret the wave form as a superposition of several oscillations.

27 January 2010

Over the last two weeks several of the LiFePO4 batteries have run all the way down. Apparently there has been current leakage in Sun Roper for all the time I have had it.


Therefore, I have decided to get rid of Sun Roper. I am transferring Sun Roper to another person who has the knowledge and materials to make it run again.

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L. David Roper,, 06-Apr-2016