I am about to start building my first electric mountain board and want to make sure I understand what I’m doing before I spend a lot of money on battery cells and a battery welder. I have a pretty good grasp on the mechanical side of things but want to double check my electrical stuff before I start. Overall I’m running dual 6384 190kv motors, a Go-FOC DGV6s VESC, a JBD 60A 10s-17s Li-ion BMS (Wiring to be charge only), and building a 12s6p battery out of Ampace JP40 21700 cells. I plan on getting a AWithZ P20B 14.6 kW Spot Welder, and welding 0.2mm copper (both of which and cells I will get from DIY500amp). Any suggestions on things I should change before I go all in? rough wiring diagram drawn below.
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I hope you are getting Matrix III and Singularity bushings!!!
Fuse the charge port.
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Here is another diagram for reference
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right now I have the 91116 - MBS Atom 95X Mountainboard, base trucks and all that, plan on getting a brand new truck settup once all else is built. The mechanical mounting system I built should fit different trucks. Suggestions on what I should get?
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You don’t need a separate antispark switch. The DV6s has an antispark switch built in. It should have come with a power button and instructions where to plug that button in (and the proper vesc settings to enable that button).
Having the XT90 loop key is up to you. If you plan to use the DV6s power button, then the loop key would pretty much just be a safety/backup disconnect. Most people don’t bother with loop keys these days, but some people still advocate for them. Doesn’t really hurt to have it if you see a use.
If you want to use a fuse, that’s certainly a decision you can make. Use the search box on the forum if you want to read thousands of words of heated debate about the pros and cons of fusing your main battery connection. But all that aside, if you plan to use a 200A ANL fuse you might as well not bother. That’s never gonna blow, even if your ESC is violently combusting and melting itself into a puddle. Take a look at the fusing curve graph on the datasheet of the fuse you plan to use.
Personally I’d recommend getting 0.2mm pure nickel (NOT nickel plated steel) instead of copper. Welding copper properly is challenging. Particularly for your first battery build, nickel is much easier to get solid welds. And it’s going to be able to handle plenty of current for your battery and ESC specs.
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Why not get a 5ah cell?
Ampace JP40 21700 X 6p is 24ah. Get a 5ah cell for 30ah pack. Unless the JP40 is a great deal and you’re happy with that range I suppose?
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My first esk8 battery was made with a low$, low power welder, but with 0.1mm copper under 0.1mm nickel plated steel.
I certainly didn’t require 0.1mm copper for a low power build, and I had some issues with not using enough welder power, as I feared smoking the welder at higher power pulses. I used copper as I figure why add to the heating inside the enclosure.
Ultimately, that battery never had any issues, other than excessive sag, and would get too hot too easily, due to poor cell choice.
I assumed I would make a mistake and screw up the first esk8 battery So I used cheap cells, but that cell choice was the mistake, even though on paper they met the minimum specs for the ESC.
I do still occasionally use that battery as a top mount range extender. It did require some manual balancing after sitting at storage voltage for 8 months.
I do not regret using copper for it, even though its benefits were likely minimal at best.
…-.-
The Ampace JP40 is still a great cell, but once it gets to about 3.2 volts, it really drops off quickly which might cause a longer walk of shame than another cell would.
But from the 4.2 to 3.2v, at 20 amps continuous, it maintains a similar voltage curve to the best 5.0Ah power cells such as Tenpower 50XG and Reliance RS50, and only the Tenpower 50XG stays cooler than it.
The following link shows a Cell comparison at 20 amps continuous, and the very bottom shows the mah’s delivered to 3.0v.
The Nominal cell capacity spec would have one believe that a 5.0ah cell will deliver 20% more range than a 4.0AH , but the actual usable capacity gain is far less, as one would need to discharge all the way down to 2.5 volts, at a very low rate, for that extra nominal capacity to be realized.
This is not realistic for an esk8 application( and most applications), especially as the BMS is bypassed for discharge and a hard cut only at 2.5v risks bringing some cell groups below 2.5v, which is to be avoided, not only for cell longevity, but battery safety too.
For those not wanting to click the link, at 20 amps continuous:
Ampace JP40 delivered 3940mah down to 3.0v.
BAK45D delivered 4059mah,
The Reliance RS50 delivered 4352mah,
The Molicel P50b delivered 3835mah,
The Tenpower 50XG delivered 4362mah.
So down to 3.0v, at 20 amps continuous, the 5.0Ah rated Tenpower 50XG delivers 11.05% more capacity than the Ampace JP40 will.
It is not the 20% more the nominal rating would have one believe.
If comparing Ampace JP40 to the venerable well respected Molicel p50B, at 20 amps continuous, the JP40 delivers 1.11% more mah, and also stays far cooler discharging to 3.0v.
In the link above one can change the amperage and watch the usable mah to 3.0v change.
I just chose 20 amps as 120 amps seems like it would be about the max battery amps in a powerful Vesc’d esk8, employing 6P battery.
But the JP40 delivering 3940 mah of its rated 4000 mah capacity, down to 3.0v at 20 amps and staying very cool doing so, makes it a pretty impressive cell, in my opinion.
The Molicel P50B delivers 3835mah of its rated 5000mah capacity at 20 amps continuous, down to 3.0v.
Now if one were seeking ultimate range, down to 3.0v per cell group, at 20 amps continuous, and could get their hands on the following cells, and pay their premium price, and take a risk on preproduction unproven 21700 cells:
Linkdata 65P delivers 5073mah
BAK 65E delivers 5063mah
Tenpower 60Xg delivers 5008 mah
Reliance RS60 delivers 4962 mah
Trydan Tech 6000T delivers 4862mah
LinkData 55p delivers 4558 mah,
These top teaser cells, on paper, do deliver the 20% extra usable capacity over the JP40, at 20 amps continuous, down to 3.0v.
It will depend on where you set your Vesc hard and soft cuts as to how much range you will get with cell A compared to cell B, and capacity retention over the cycle life is another factor not accounted for in these comparisons.
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Assuming you are using the SP17S005 bms model, here is the exact wiring diagram for 12s:
Link for reference: Jiabaida SP17S005 Smart BMS 10S-17S Wiring Diagram – Jiabaida BMS
I bypass all my bms’s, and use a project I created to get individual cell voltage telemetry to VESC for HV/LV cutoff: Making bms's VESC compatible
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If I’m using a Do-FOC DV6S which pulls 160A with 2 motors, what gauge of wire should I be using, is there any easy way for me to figure this out?
This may sound dumb but I asked Claude because I was super lost and it said 2AWG but that seems way too large?
10awg wires for the battery leads and 12awg for motor wires will do fine as long as the soldering and connectors are half decent. For connections that don’t have to be used frequently like a charge port, large bullet connectors (5.5mm and 8mm) are very easy to wire and powerful.
I saw it described well by someone else here. Racing/other vehicle vs stump pulling. If you wanted to run 160A per motor and 200 battery amps for 2 minutes straight it would need vastly more powerful wiring, and you would also be going 4000 kph.
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This is a great resource
Keep in mind that not all wires are equal, the sheath of the wire plays a pretty big part in what kind of current it can handle. I wouldn’t consider using anything other than silicone wire for power delivery.
It’s also pretty important to consider your wire length (longer wires produce more resistance/heat) and that there is pretty much no such thing as a ‘continuous’ current level in esk8. You may see peaks of 160A, but they will be extremely short lived.
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I mostly agree with this, but in some rare cases silicone can be worse than PVC. Silicone insulation rips easily. For example, if you have wires held down by a clamp or cable tie and they are being flexed and tugged on, especially if the clamp is tight, the silicone insulation can rip right at the fastener and cause a short circuit. PVC avoids this failure mechanism. However, PVC has a VERY low melting point, which can cause its own problems. Generally I would advise to use silicone and just avoid this way of mounting the wires.
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PTFE jacketed wire is better than PVC in just about every way besides price, in my experience. If someone is in a situation where Silicone hobby wire doesn’t make sense, I’d recommend they look at PTFE wire next, not PVC.
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PTFE wire is very difficult to strip though.
True, i used a lot of ptfe wire in my battery building days, mainly to keep wire height to a minimum. But as Brian says, it IS difficult to strip, and the stiffness of it makes it somewhat difficult to work with as well
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In my experience it’s not enough of an issue to turn me off from using/recommending it. Yeah it’s a bit annoying, but imo for hobby uses it doesn’t matter if stripping your wire takes 5sec vs 10sec, because we’re only doing, at most, a few dozen in a project. For commercial uses those extra seconds matter because they add up.
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It’s not really about the amount of time it takes. It’s about the frustration level and because sometimes when it’s really difficult to strip, people can accidentally cut strands while attempting to remove insulation, or cut themselves in extreme situations. I couldn’t recommend PTFE wire any less unless you’re building spacecraft or warplanes.