I second this, that strategy has let me get away with using XT90s connectors at 20s
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90 wh/mile no load freespin 
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Gets 8 miles of range ¯\(ツ)/¯
8 miles of range from 1450wh battery? Is that racing or just like going out for a street ride?
It’s closer to 1200Wh (8x 4s 9500mAh lipo), but pretty much yup.
I only ride on track, this board doesn’t quite have the ground clearance to casually ride on the street😂
Just checked my Metr logs from the San Diego zoo esk8con track we set on Tuesday night, I discharged to 3.6v/cell. In total I rode 14.42 km(8.96 miles). So 8 miles is a slight exaggeration
(I typically only charge up to 4.15 and try not to discharge below 3.7)
My Megan has a bunch of readouts, including efficiency; when low speed cruising/warming tires I get (at best) 95Wh/mile, track racing nets me ~110Wh/mile
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charge to 4.25
unless you feel spicy! 4.30 V per
I uh…definitely didn’t do this accidentally and definitely didn’t intentially cut this detail from the post
After adjusting the power supply’s voltage with the exposed potentiometers to ~66.4v (4.15v/cell), i charged my board
Two hours later I checked on it, and the power supply’s output had shifted to ~68.5v.
I guess the factory never burned it in?
I returned the potentiometer back down to 66.4v, and it’s been fine ever since. Hasn’t stopped me from neurotically checking the power supply voltage before and cell voltages after charging.
One of the pros of buying the cheapest 72v psu’s from Amazon, I guess
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I have the Jeti afc on v5#1. I think i also have an extra on hand.
you can also get QS8 with the bigger resistor (15Ω I think it is) that they use on the bikes.
EDIT: QS8 not AS150 … doh.
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Are least they’re easily replaceable….?
Of my 8x 4s packs, 2x of them now have a dead P-group and are shaped like pillows
The other 6x are slightly puffed.
The solution I’m rolling with right now is to take out the bad two, and fall back to running 12s on the remaining 6.
I could buy two replacements, but running brand new packs in series with obviously damaged ones makes me uneasy…
sigh
I’m just glad the 4.4v cells didn’t ignite, I’ve seen lipos in that range go off spontaneously
Were you able to discharge them?
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Dang… what do you think caused so many issues with them?
Aye, same. Gave me a heart attack when I noticed their voltages
Took a day and WFH to monitor their slow discharge.
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Not having a proper BMS and charging straight to the battery terminals with a “dumb” power supply
Oh dang sorry to hear it dude. I used 3 toolkit M6D chargers and a server PSU to make a 6 channel charger setup for relatively cheap. About $200-$250 to build it. Might be an option for you.
I can get all 6 9500mah lipos charging at 9.5amps individually for the most part. Sometimes it thermal throttles and shuts off at 9.5amps if the ambient temperature is higher. But 9amps has run consistently well for me per lipo. So 54 to 57 amps all at once.
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I was wondering what you did when you went from 12s and the icharger x12 to 16s.
oops. glad you had no fire.
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Cool setup! Super slick, I love pelican case projects. Especially ones as clean as that.
I want to a be able to charge my batteries without having to pull them out(like a normal board). Was able to do it for a couple months, and it was awesome. Don’t think I want to go back to needing to pull them out every time 
Thanks for the suggestion tho
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Yeah not the most fun process each time. Pros and cons of its design for sure.
Today’s issue: ESK8CON Prep
Wait, esk8con already happened! Like a month ago!
Yeahh… took me a minute to get to this writeup 
Front box revamp
As mentioned before, I avoid doing anything with the front box it if I don’t have to.
However, It reached the point where it basically needed all of it’s parts repaired or replaced, so my hand was forced into doing something.
Off they come!
First step, bend the metal back into shape
Return of the hodgepodge metal break
“But won’t it just get bent back out of shape again?”
Good question, metaphorical reader.
New footstop
In the current design, there’s nothing to take transverse (side to side) loads on the box.
When I first installed the 3D printed footstop, it was designed to be a barrier between my feet and the G300s, not a structural member. Because of this, it was only 1.2mm thick.
Engineering Forces Tangent
It’s basically a 4-bar mechanism(where the pivots are at the corners of the sheet metal), so it’s not surprising that it gets bent out of shape. (This is why we use diagonal pieces and triangles when designing buildings and whatnot)
This is reflected in how the part breaks. It broke at the layer lines of the 3D print, but only between where it connects to the box
What happens is it takes up a transverse load, but it’s not strong enough to resist it. This shear load breaks the middle of it into a bunch of little bars, which “slide” relative to eachother, letting it part flex and deform, reliving the stress. (This is represented really well by the permeant deformation in the picture)
I printed a new beefy version that’s 4mm thick and solid plastic. It should definitely be able to take the transverse loads now.
I have the slots for the sides extending into the 4mm front so I don’t give up any more valuable deck space, and there shouldn’t be much force going through that section of the part. Most of the stress should flow through/around the interior fillet.
New Spine clamp
This part clamps the box to the frame of the board, transferring all the forces directly to the frame instead of going through the sheet metal deck.
Fixed it.
New nut retention
While I was re-assembling, I took @BenjaminF’s suggestion of a captive nut plate. This made reassembly massively easier, thanks for the suggestion dude!
If you were eagle-eyed, you migh’tve spotted them it in a earlier photo.
All of these improvements means the box is much stronger then it was before. 
Tires
I wore through my front BRPs, but I didn’t have any replacements on-hand (until receiving new set from @MoeStooge at esk8con).
@HAIRYMANJACK had a spare pair of wides that he let me use. Ended up having enough tread to race on them at esk8con, even! Thanks dude.
^Artwork curtesy of @Lyfe_Of_Jimmy, feat. Reggie Thomas
Busted Batteries
Woke up for work one morning, and felt the need to check the battery in my stooge.
that’s… suboptimal
guess I’m WFH today. I started discharging the packs 4 at a time using my iCharger x12 at 50W. Took all day to bring them all down below 4.2.
I definitely did some damage overcharging them like this. They’re all slightly puffed now, and their internal resistances shot up. (When they were new IR was 0.1~0.2mOhm)
I removed the two packs that now had the dead p-group, labeled 'em appropriately.
I then drove to San Diego for our weekly track night and did 8 miles on track 
So I’m back to running on 12s for the time being, unfortunately. I could buy two replacements for the dead p-group packs, but I’d be warry of running new packs in series with damaged ones.
Fortunately, I still had the old balance harness and hardware from before I upgraded to 16s… Popped that back in how it was, and I’m still able to charge without opening up my bellypan, but I’m back to charging with my iCharger x12. I’m waiting to receive a zBMS in the mail, the only BMS that can fit in the restrictive space.
Once I get it installed, it’ll let me go back to charging with a single plug. Can’t wait.
Brake light
(go to the quote to see the video I previously posted, pretty happy with the aesthetics)
Aspiring to make these code updates before eks8con, I plugged in the Arduino to my computer. I proceeded to corrupt it, or something, idek, it didn’t even register in device manager after I tried to upload code.
These things can happen with arduinos. Though the magic of buying two of them, I had a spare microcontroller. While I was swapping it out, I figured I could make things better. The first one was just a quick prototype- it was little more then a microcontroller with some wires soldered to it(and covered in heatshrink).
So I spent a few hours making a more proper breakout using perfboard, connectors, and crimping matching connectors onto the harness inside the board. Much neater.
Unfortunately, even though the pinout was the same, it’s unable to register the PWM signal from the receiver. 
Esk8con was growing closer, so I cut my losses and figure it out later. I put kapton tape over the newly crimped connectors on the board and moved on.
It’s more of a break light, amiright?
Stickers
Honestly, I’ve unexpectantly grown attached to my silver bellypan.
However, it was a bit plain, so I covered it in stickers at 2am before leaving for esk8con
Shoutout to all of the incredible, awesome people that makes this sport fun, both on and off the track
Photos from @Lyfe_Of_Jimmy and @MarioChacon
Packed and ready for esk8con
And to think I thought I could fit a second person and stuff in here
To be continued in a future edition…
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