amberwolf said:
If the pack gets hot enough to need that kind of cooling, it's either using the wrong kind of cells, or not enough of them.
You're right LOL... I don't plan to use my Sony VTC4 anything higher than 40°Celcius anyways :wink:
I'm currently (and slowly) building a 14S10P pack out of VTC4 for my 30 amp controller BBSHD so the battery will handle it with good very confortable margin (GOAL : Long lifetime of the battery). Just one VTC4 cell is rated : 2.1Ah, Max 30A/cell , BUT AT 100°C when reaching 0%SoC @ 30A, compared to 80°C @ 20A or 50-55°C @ 10A/cell...
It's just that I'm having lot of fun building an overspecd battery.... Fantisizing about cooling solution.... The wind tunnel (with double fans and venturi effect in the middle ) solution is just plain cool.... but it takes more space and I think It's a bit impractical...
For the cells, Il will parrallel cells with copper bussbars (1.7 mm thick, 9 mm wide) by soldering the 18650's original spot-welded tabs (0.15mm x 7 mm nickel-plated COPPER tabs... One tab leg = around 16-18 A ampacity ... here I'd have two tab legs per cell soldered to bussbar .... so it'd be good for more than the cell's max 30A rating.) directly to the bussbars. A bit like that :
View attachment 2
Yes, overkill, but the cell have such low DC-resistance/AC-impedance (see graphs)... I think they deserve good connections !
And as you can see on second graph... controlling Temperature (as with fans for example) can mean tweeking for the best compromise between Lowest possible internal resistance from high enough temps but not so high that it will cause cell damage/premature death from overheating.
For wire, il will use real copper 4AWG welding cable (not the CCA crap 4AWG you saw in this image... Copper Clad Aluminium is the biggest scam ever).
For andersons connectors, I will be using Anderson powerpole PP75 (max 120A continuous) with 6AWG silver plated connectors (they fit very snug on 4AWG cable).
One day, i will have to upgrade my BBSHD controller
Maybe something like that... https://endless-sphere.com/forums/viewtopic.php?f=28&t=83450&start=150
BTW : Thanks to all the people who published these graphs on ES forum about then VTC4 cells (and all other cells)... They are not from me, I just reposted them. I think they are very usefull to predict how battery pack can behave in practice. Many come from this specific thread post : https://endless-sphere.com/forums/viewtopic.php?f=14&t=73701