F750 Voltage Cutoff (and LK-570 capacity]

Sean Nugent

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So,

I had an F750 fitted to my Accord about 3 years ago and have never been happy with its parking mode operation.
I have a LK-570 (I think) 6ah LiFePO4 battery that charges from the car when its turned on, and powers the dashcam when the car is switched off.
The parking mode never lasted long, with the dash cam shutting down due to "low battery" - and I never got around to looking at the issue.

Well the accord got swapped for another vehicle with the F750 being removed and its not been put onto the new vehicle yet (waiting a month or so for any car gremlins to turn up first)

So I built a car, in my living room
OK - so the "car" in this case is a car battery, a trickle charger, a mobile phone charger (cos I am testing one of those as well - its not on the LK-570) and the LK-570 and F750 along with appropriate connectivity to the battery

I use the trickle charger to simulate the car running and I unplug the LK-570 from the main battery to simulate parking up.
The F750 is set to shutdown at 11v (absolute minimum) and set to run for 12 hours (possibly 24)
The voltage on the LK-570 starts at 14.49V Under Charge
Dropping immediately to 13.5 at 0:00 with the charger removed from the circuit
10:00 12.47
15:00 12.24
20:00 12.10
30:00 11.84
35:00 11.72
40:00 11.58
at 41:00 The Unit shutdown due to low battery - I was on the other side of the room so didn't get a voltage reading just before other than the 40:00
42:00 12.04 with no load

This all implies that the LK-570 is flat or close to it

Further testing indicates that the camera pulls 0.2A, with 0.19 in parking mode - lets assume 0.2

in 41 minutes I should have pulled 0.2*41/60=0.136 ah from the battery - a lot less than the nominal 6ah. In fact, assuming 4ah useable I should get 20 hours use out of the battery as from memory the discharge characteristics of the LiFePo4 is fairly straight till it falls off the edge.

I think its knackered - the LK-570 that is - and probably was early on. It doesn't matter why or how

Does this make sense - have I missed anything obvious?

Sean
 
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Sean Nugent

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I am going to post this in the battery forum where its probably better situated

Sean
 
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