Thanks for the advice I will consider posting a question on the forum when the package arrive. Will's opinion was a comment on this video btw, I can see now it's not totally negative though [1]
For the problem #1 I think the BMS can solve the issue as I already ordered a JBD BMS so it can cut off whenever it reaches the critical voltage.
For #2 you're right I think I should check, my MPPT is good one (Epever) but not sure it could lift the voltage properly from such a narrow difference, unless maybe I use higher voltage (such as 48) than my pack 's voltage (24v) so it will be guaranteed to only reduce the voltage to the lead acid levels.
Thanks so much!
Yes - I have watched this video. Emily & Clark have a different setup, as he uses a different device (or even, no device) to connect the two different banks (lithium and lead acid).
I didn't see Will's comment tho, thank you for sending that, very thought provoking! The comment by him "Trickle charging lead acid all night with lithium seems very inefficient" is 100% true, but in my case I consider this effect a bonus b/c the lithium acts like a capacitor for the solar array (quickly charges, then slowly charges the lead!)
You're right, I think my situation is similar to yours. My solar array is not so big (for now at least) so I have lot of power in the noon but less in other times, so it will be very helpful to have a lithium pack that absorb all that power quickly and then feed it to the lazy lead pack over the next few hours.
I have 1540W and it's enough to cover more than 16hrs of power outages (light fridge, fans etc...), but I'm planning to expand as things are going wild in the near future probably. I'm afraid at the current rate of wars and energy insecurity even some rich countries will face the issues we're facing and we will be even worse!
I used to have an Epever MPPT. Really nice unit. However, as I recall, the manual emphasized that you should only use solar panels for the input. This is because when the battery is full the MPPT will stop charging by shorting the input. This is fine when the input is solar. But if you are doing LiFePO4 -> MPPT -> lead, it's going to short out your LiFePO4 battery when the lead battery is full, which would be very very bad.
-- 1: https://youtu.be/tAuPfgZgXec