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Hi Mike,
i think Al's point to protect this battery is suites more for what i am looking for with his suggested LM317 circuite than a zener diode, ...
Hi Mr Al,
Well, thanks for your detailed infightings notes.
I think I might use a pwm ready circuit I found in the net that principally works like that: it charges the battery freely up to 14.4v and than stays there for a while and then starts to modulate until it gates down to 13.5v level and then stays there until charge is stops=dusk or with no time limit. That’s covers points 1-2 as you noted.
As for point 4 timer, I am not sure this circuit has internal clock even it looks a neat solution and I don’t know how to add one i'l be glad to learn from you… basically I am looking for a simple addition if you know any?
As for temp sensing, I will check this option whether it is within the second bttr ptc. and for balancing, I prefer pack instead of balancing, great that you floated this option also.
As for point 3, low current cutoff point, please advice how it can simply done? Can you show any relevant scheme for this one?
As your lm317 solution, my concern is not to waste a power in linear charging but to use switch pwm as I noted, do you think it is a right point in a matter of efficiency with my spec as above?
No power is lost with the scheme I showed in post #17. Only after the battery reaches its maximum-allowed-during-charge-Voltage is any available current diverted away from charging the battery. Prior to the battery reaching that voltage, 100% of the available solar current goes into the battery.
Hello there Mike,
Are you sure about that? ....
I though I had already covered the MPPT issue in post #6. If I understand the OP, his panel has an open-circuit voltage of 18V, so its MPPT voltage will be about 15V, which is getting close to the voltage at the end-of-charge for his battery.
The additional amount of panel power you could harvest by putting a MPPT controller between the panel and the battery would accrue only at the beginning-of-charge when the battery voltage starts out at 10V. By the time you factor in the 85% efficiency of the MPPT controller, I don't think you will get any net reduction in charging time, maybe 5% at best, so not enough to make it worth dicking around with the MPPT controller.
Just connect the panel to battery, and be done with it.
Hi,
The low cutout point would be to disconnect the battery from the load in the event that the load drew the battery voltage down too low.
Either way, a comparator circuit would detect each condition and take the appropriate action: either turn on the charger or turn off the load.
Barg:
I dont know much about the specifics of charging LiFePo batteries, but I do know how to make a current sensor.
R1 is the shunt. It will go in the minus lead of the battery.
Circuit is powered from the 14V shunt regulator I showed earlier.
Circuit has a moderate amount of hysteresis.
Output is high while battery current >30mA
Output is low as current drops below 15mA
Circuit will work with the LM33x comparators, or a LM358 opamp...
View attachment 96386