webosplash
10 mW
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Running parallel battery pack. I need help please.
- Thread starter webosplash
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webosplash
10 mW
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probably 0.oflippy said:
I’d run two separate bms a good bms is hard to come by that would handle cutting off a pack if and when it is unevenly discharging. I recommend using two Ryobi 40v battery bms boards which is wired as 10s 2p because battery 1 and 10 are connected through the board so when it fails it will fail safely. Cutting off just that 10s string
batteryGOLD
100 W
U should(must) do it parallel.
Final battery will be equivalent to 20P 20S system
more than double range, more acceleration bcause more instantaneous available current,
and more cycles. current is going to half at each cell, means more life for total system.
80A motor peak divided by 20P cells means 4A peak per cell
Using individual pack 80A dived by 10P equals 8A per cell peak. more hardwork for cells..
Remember to charge both batteries at same voltage than establish parallel link. Can do full charge than do parallel link
Final battery will be equivalent to 20P 20S system
more than double range, more acceleration bcause more instantaneous available current,
and more cycles. current is going to half at each cell, means more life for total system.
80A motor peak divided by 20P cells means 4A peak per cell
Using individual pack 80A dived by 10P equals 8A per cell peak. more hardwork for cells..
Remember to charge both batteries at same voltage than establish parallel link. Can do full charge than do parallel link
Worst cases Scenario your weakest link In chain fails... Bring a fire extinguisher around just incase shit goes thermal. I doubt that it a bms even matters the controller has fail safes unless programmed to ignore. battery sag will fault controller eventfully
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webosplash
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They both have a separate BMS
goatman
10 MW
80 amp controller
20s10p 80 amp bms
20s10p 100 amp bms
full out 80amps from 20p is only 4amps/cel
unless youre running recycled laptop cells, who cares, just parallel the batteries together
what cells do you have?
20s10p 80 amp bms
20s10p 100 amp bms
full out 80amps from 20p is only 4amps/cel
unless youre running recycled laptop cells, who cares, just parallel the batteries together
what cells do you have?
webosplash
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goatman said:
the 100 amp pack is Panasonic NCR18650GA 10A 3.5AH
and
the 80 amp pack is samsung 35E 8A 3.5AH
think this would be all good
goatman
10 MW
i would, theyre both "10amp" cells with the same rated capacity being discharged at 4amps max
unles youre hopping on the highway and going full throttle til the lvc is tripped, dont see a problem
go to the lygte comparator here
http://lygte-info.dk/review/batteries2012/Common18650comparator.php
put in the cells with 2amp discharge and 5amp discharge, they both hit what would be the lvc at about the same time with very similar discharge curves
unles youre hopping on the highway and going full throttle til the lvc is tripped, dont see a problem
go to the lygte comparator here
http://lygte-info.dk/review/batteries2012/Common18650comparator.php
put in the cells with 2amp discharge and 5amp discharge, they both hit what would be the lvc at about the same time with very similar discharge curves
webosplash
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goatman said:
I like getting on the highway
goatman
10 MW
so do i 
its just if your full throttle and 1 bms trips its lvc the other will go from 40amps discharge to 80amps discharge at the same moment, could be a problem for a crappy bms
its just if your full throttle and 1 bms trips its lvc the other will go from 40amps discharge to 80amps discharge at the same moment, could be a problem for a crappy bms
webosplash
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goatman said:so do i
its just if your full throttle and 1 bms trips its lvc the other will go from 40amps discharge to 80amps discharge at the same moment, could be a problem for a crappy bms
Do you know anything about Daly?
I use that bms on both.
goatman
10 MW
no, i dont use a bms
thinking of buying an ANT bms and an active balancer when i want to do some pack maintenance
thinking of buying an ANT bms and an active balancer when i want to do some pack maintenance
Ideally you should use same cells with same amp hour capacities throughout a battery pack. they should all be balanced to +\- .02 volts per cell prior to a series and or parallel connection. Any discrepancy in voltage can set a battery into a thermal run away in some cases the heat will trigger the next cell to start thermal sprinting. Batteries don t like being used unbalanced. Or with other batteries that have less capacity. Especially batteries that get super hot. Worst case scenario the weakest link in the chain will give. Lmk how it goes. If it goes up in flames [emoji91] try and put it out fast needless to say don’t kill anyone including yourself. Last thing we need is more legislations for dangerous batteries builders
[emoji367].
[emoji367].
0.1V difference per S-count is plenty safe enough for connecting in parallel
so 20S packs can have a 2V delta no worries
and they will self-balance at the pack level, or ideally connected at each balance lead as well.
In series, where there is no self balancing flows at all, then yes using a balancer at your selected voltage (top balance vs bottom) is required to get full capacity
but that is off topic here.
so 20S packs can have a 2V delta no worries
and they will self-balance at the pack level, or ideally connected at each balance lead as well.
In series, where there is no self balancing flows at all, then yes using a balancer at your selected voltage (top balance vs bottom) is required to get full capacity
but that is off topic here.
webosplash
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Both batteries are 35AH 72V the only difference is one is capable of 100A and the other is capable of 80ARobinev said:
If the parallel connection is trying to draw 80A would that demand 40A from each pack or would the controller try to draw more from the 100A pack.
This is the answer I need.
Paralleled connections will never flow perfectly evenlywebosplash said:
there is always a difference in resistance.
But with only 2-3 units in parallel, that's OK.
Once peak discharge subsides, any voltage difference causes flow between units to "self-balance"
Not quite as ideal as all in one pack, paralleled cell groups at the 1S level only
but no problem in practice.
webosplash
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but will the controller demand 40 from each battery or will the controller recognize that one can drain faster and do so?
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