Joule Smasher Led Flasher - Update at 6 Months into 10 year Life on AA

 It's been 6 months since I installed a fresh AA battery into an early Joule Smasher Led Flasher. The battery voltage over that time has been on track to last 10 years. 

The graph below has two curves. One is the best AG3 cell result which lasted some 19 days. If a AA battery was to last 10 years then the 3650 days could be scaled to 19 days. One day for the AG3 cell would represent 193 days for the AA battery. As long as the AA voltage on the scaled axis is above the AG3 cell voltage then I consider the AA is on track to meet the 10 year lifespan.

So far, everything is on track to meet the expected 10 years of life. While I changed the timing in the early stages (~1ms till Day 89, 10ms till Day 113, 3ms thereafter) I don't believe this will seriously detract from the test results. The AA battery voltage after 184 elapsed days, or 0.95 days after scaling,  is 1.460 volts. While comfortably above the AG3 curve I note that in the last 60 days or so the AA cell has been dropping an average of 0.27mV per day. If the discharge curve does not flatten out like all the previous test results the AA battery will still last 10 years.

LiFePO4 replacement for Ride On Mower Lead Acid Battery - Update

I fitted the silicon diode in parallel with the mosfets and ran into trouble. Once the mosfets turned off the alternator had trouble regulating with the reduced load. The alternator voltage rose and the mower shut down. I found that a resistor to ground before the diode eliminated the issue. With some of the proof of concept stuff behind me I'm going to build version 1. It will have the following characteristics:

1. A number of parallel mosfets which when turned on allow the mower to be started and the alternator to directly charge the batteries.
2. Once the battery voltage rises above the first set point the resistor bank will be switched across the alternator to help stabilize the alternator output
3. As the battery voltage rises to the second set point the mosfets will be turned off and the battery will continue to be charge through a series diode with perhaps 0.6V of loss.

At this point the maximum charging voltage should be around 13.4volts. Combined with a charge balancer it should ensure no damage is ever done by overcharging the LiFePO4 cells. The state of charge should approach 90% at most.

I'm leaning towards using a micro controller instead of all analogue circuitry because it offers flexibility to alter parameters or add additional control mechanisms should I need them.

Results with Flat AA and AAA cells - Further Update.

Finally, the exhausted AA cell stopped working after 120 days. It would have run longer but I changed the on time to 10ms to accelerate it's demise back on day 51. The trials with exhausted cells has led to the following conclusions:

1. The larger the battery physical size the longer it can run below 0.8volts. 
2. The "on" time is critical with regard to energy consumption but is also important in relation to the electrolyte migrating/refreshing between flashes.

More support for the estimated 10 years life from a fresh AA cell.