Split this off from the Satiator-specific thread, rather than perpetuating a derail there.
(back-link for context https://endless-sphere.com/forums/viewtopic.php?p=1537630#p1537630)
I've never come across a 48V pack IRL for which 6A would be considered a high charging rate, is that high a voltage used for say short-usage flashlights?
Plenty of hobby "node chargers" routinely put that much through the tiny-thin gauge (#16?) balance leads terminated with JST connectors but then they may use pulsing algorithms, I dunno.
For reference, my apparently controversial guideline for paralleling cells, packs, battery banks of whatever size:
Just talking about bare cells.
I agree that some chemistries may draw current much faster than others, but my guideline is intended to include RC LiPo with real-life continuous usage at 20+ C-rates, which is indeed the context where it evolved.
It actually is not hard to just measure the current amps flowing between cells and sub-packs, put a breaker in between if you think things might get hot. When I get some LTO banks going, I will definitely do that without ASSuming anything, since they apparently can draw at 10C no problem?
There also are pretty basic and very inexpensive current-limiting circuits I've seen that use a resistor or light bulb, and also OTS combiner / VSR gadgets to do the same, I've got one for 15A, another at 65. . .
Common sense says to watch the temperature of your wiring and connector housings and cut off current long before anything starts melting.
I also completely agree that a lower delta would be better, and that the ideal would be 10mV or lower, so if it is not **too** burdensome for the owner to "pre balance charge" the sub-packs before paralleling, then yes, she should do that.
In any case, whatever voltage delta the owner deems acceptable, tossing **pack-level** specs around when widely different pack voltages are being discussed - 7S vs 10S vs 17S - just muddies the waters.
Your "acceptably safe" voltage delta should be spec'd on a per-cell basis for that given chemistry.
What would you recommend as such @amberwolf , for the chemistries commonly used in this forum's contexts?
(back-link for context https://endless-sphere.com/forums/viewtopic.php?p=1537630#p1537630)
I've never come across a 48V pack IRL for which 6A would be considered a high charging rate, is that high a voltage used for say short-usage flashlights?
Plenty of hobby "node chargers" routinely put that much through the tiny-thin gauge (#16?) balance leads terminated with JST connectors but then they may use pulsing algorithms, I dunno.
For reference, my apparently controversial guideline for paralleling cells, packs, battery banks of whatever size:
Yes this is not taking into account intervening circuitry that may also be involved, the many permutations of which - FETs diodes, BMS etc - could complicate the picture.john61ct said:
Just talking about bare cells.
I agree that some chemistries may draw current much faster than others, but my guideline is intended to include RC LiPo with real-life continuous usage at 20+ C-rates, which is indeed the context where it evolved.
It actually is not hard to just measure the current amps flowing between cells and sub-packs, put a breaker in between if you think things might get hot. When I get some LTO banks going, I will definitely do that without ASSuming anything, since they apparently can draw at 10C no problem?
There also are pretty basic and very inexpensive current-limiting circuits I've seen that use a resistor or light bulb, and also OTS combiner / VSR gadgets to do the same, I've got one for 15A, another at 65. . .
Common sense says to watch the temperature of your wiring and connector housings and cut off current long before anything starts melting.
I also completely agree that a lower delta would be better, and that the ideal would be 10mV or lower, so if it is not **too** burdensome for the owner to "pre balance charge" the sub-packs before paralleling, then yes, she should do that.
In any case, whatever voltage delta the owner deems acceptable, tossing **pack-level** specs around when widely different pack voltages are being discussed - 7S vs 10S vs 17S - just muddies the waters.
Your "acceptably safe" voltage delta should be spec'd on a per-cell basis for that given chemistry.
What would you recommend as such @amberwolf , for the chemistries commonly used in this forum's contexts?