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The "BIG ONE", battery trailer build

This one is gonna be probably the biggest pack ever seen connected to an esk8 on this forum, but I finally got it.

a 5,3kWh battery module from a BMW i3.

There’s 8 modules in the i3, each 12S, connected in series for 96S pack.

A healthy 32,4kg in the packaging

There it is.

I’m gonna be using it for my 2000km+ adventure journey into the arctic circle.

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Fuck yeah. Following this one closely. Can’t wait to see how this turns out

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@glyphiks
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But also,
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Here’s a closer look at the module and what the next moves are.

I also remeasured the weight for the plain module and it came to 29.8kg, so 30kg roughly.


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Good lord… Insanity.

You’re gonna need some serious heatsinks on your ESC and good motors

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For scale, could you take a photograph just with it on top of a skate?

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You assume i’m gonna go hard and fast, but I’m going long distance, so the two VESC 6.4 and the APS motors are gonna do fine.

So here’s my 10S6P pack versus the i3 module.



I also stood on the board with i3 module and the first thing immediately that I noticed is how much pendulum effect it added, being a very heavy mass high up.

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Dear lord. I want it.

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THE MADNESS RETURNS…

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:open_mouth:

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I also bought it as an investment, as it can be a good energy storage system for possible solar systems, UPS and works/mates well with 48V solar inverters.

The reason why I also decided to go with the trailer route, is that I foresaw that adding too much weight on top of the board was gonna cause stability issues. I can optimize the height of the battery in the trailer to be low, so it’s not top heavy.

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Oh, sure, an investment :wink:.

A pack like this strapped between my legs makes me feel like
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Yeah fuck having that on the board. Keep it low in a trailer and you can keep your supplies/camping shit on top. Trailer is perfect for this and exactly what i will do when the time comes

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yep been thinking about battery trailer design for a little while. I am sure anything too wide would be a disaster once things got tight.

Now on to putting two motors on the skate for throttle and two motors on the trailer for braking. :smirk:

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I’d like to offer my design services.

Nope, kinda smol, here:

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Does it come loaded with ice and drinks?

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The big pelican was intended to fit a 60lbs 3d printer, but we were short 5cm.

I drank all the drinks. But, I’m envious of ur goals.

My biggest pack (12s10p of 40t cells) was too heavy. 3 sets of lipos totaling similar w/hr was also not fun.

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HOLY COW. Your battery pack is gigantic. GIGANTIC. Your battery pack is literally the biggest thing within the tri-state area. Your battery pack is bigger than a small elephant. It is bigger than, like, a tree. A big ol’ tree. Probably a coniferous. Lots of branches on your battery pack. You must wake up every morning and thank the good lord above. You are truly blessed. Congrats.

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Here’s an early concept design for the aluminium frame for the trailer with the roughly correct size of the module in the bottom.

I disassembled the positive terminal plastic housing, as I need to get to both B- and B+ to charge and discharge, as I want to do a capacity test, which is gonna take quite a while with a 150W load :smiley:



I also broke into the enclosure where the balance lead connected to, it was the BMS.


Linear/Analog battery stack monitor ICs LTC6801 and LTC6802-2. These are older generation than the LTC6803-3 that I’m using on the FlexiBMS.

Also, when people complain about slow balance currents. This sucker has 56Ohm bleed resistors, where the FlexiBMS is using 47Ohms, so technically this is a slower balancer than the FlexiBMS, but it doesn’t have the same size constraints as the Lite does.

I’ll 3d-print a custom holder for the balance breakout board and probably integrate the FlexiBMS on top of it as well into the same enclosure. It’ll be a nice contained package then.

EDIT: Still need to get to that negative terminal, but I don’t see any easy way to get rid of the enclosure around it… might have to go a bit more destructive on it.

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