I just want to clarify something I’m thinking about doing. I have a 10s4p battery on my DIY and I want some more kick or rather range. The pack is made by me out of Samsung 18650 30Q cells and with a discharge bypassed 10s BMS. My idea is to top mount on the deck a 10s2p out of 30q cells to combine the two in a 10s6p. I asked the same question on the esk8 discord and we argued a little while and I don’t think it came to a conclusion. Some say it’s possible with no problems and others say it’s not possible. I will probably be connecting the two with a XT90 Y splitter to a ESC and I will have to add another BMS to charge the pack on top(?). What do you think? Is it possible to do? Or do both packs have to be 10s4p?
This is purely for range. I want to make a 10s6p to go from 80A max to 120A for more kick and also range. I fear the charge and ride will heat up the cells too much and cause them to loose capacity faster than they should.
Yes, you can add another pack with same S count in parallel with your old pack. Just take care that they are on same voltage when connecting them in parallel. And use bms in each pack.
They will also discharge at the same rate? One is bigger in capacity and if they don’t discharge evenly there will be voltage difference and the BMS may shut it off no?
Bigger pack will give 2/3 of current and smaller pack will give 1/3, but they are in parallel so they will always be on same voltage level = they will discharge at equal rate
I don’t want to add too much weight to the board. and going from 40A a motor to 60A a motor is quite a difference. I don’t want to add more batteries just to carry the weight of other batteries lol. 648WH compared to 432WH is already an upgrade. with my economy that I had with 10s4p just chilling I was getting 9WH/Km =48 KM. When chilling with 10s6p and lets say 11WH/km = 68KM so + 20KM anyways . Also price is a factor I need to consider. going 2p is saving me 1/2 if I went 4p.
If you are talking about max motor amps in vesc settings, you can up that even to 100A on each motor, even on 10s4p. Those settings will affect only your low speed acceleration. If you are saying that you can draw 60A with 10s6p instead of 40A on each vesc from battery, I don’t think you will feel any difference. You have PU wheels, right? You will hardly ever reach 80A from battery, if ever, so there is really no difference if you could pull 100A. But smaller battery = lower weight is valid point
Hold up!
It is very important to remember that once you get to lower capacity, the smaller pack will be “stressed” by the load. its important to not build a huge external and proceed to ride it hard at or below 3v.
That’s what I was talking about above. I’m not sure what to think about it as it’s really controversial. You’re saying to start cut off earlier to avoid stressing the smaller bat correct?
I mean battery discharge max. from 40A as the amperage has to be split if 2 ESC I can go as high as 60A if I upgrade. + my brakes will be stronger as I can push more current back correct?
Why do you think that? Bigger P count -> each cell has less stress. Also, each pack has bms, so there is no chance that any pack will go lower than bms allows.
@IVoxuI thats what I am trying to say! You can increase/decrease acceleration and brakes strenght with motor max/min. You can put for example 80/-60A on motor side even if your battery can give only 40A to that motor.
Yeah when the battery is in parallel they don’t work independently anymore. Individual cells in the smaller pack will see the exact same load as individual cells in the larger pack. Hence parallel.
My biggest fear would be attaching packs at different voltages would want to charge the lower pack very quickly (possibly to fast) simultainysly the higher voltage pack would take all the load from the motor until the packs self balance out.
This is only a problem at low voltages. And i read this in one of the other threads by I think @RyEnd ? Ill see if I can find it.
But the way I understood it is if both packs are below 3.2 v (ish) and you draw lots of amps, the smaller P pack will suffer damage. Basically the bigger pack will charge the smaller pack (which is good) But if the difference in capacity is large and you ride around a lot on an empty small pack and only the large pack having juice left, you will drain the system faster than it can redistribute the charge. This is the same reason you don’t build p groups with cells of different capacities.
The fix would be to remove the empty pack once its done, and would therefore require the smaller pack being external
No, they both drain together. No one is charging the other one.
This literally cannot happen in a parallel connection
You can.
The only scenario in which this is remotely true, is if the smaller pack is attached to the board close to the esc, and the bigger pack is very far away tethered in a backpack, AND the ESC is drawing MAX power exceeding the capabilities of the smaller pack continuously with no break at all inbetween.
. Also price is a factor I need to consider. going 2p is saving me 1/2 if I went 4p.
You can increase/decrease acceleration and brakes strenght with motor max/min. You can put for example 80/-60A on motor side even if your battery can give only 40A to that motor.