Can you see anything wrong with this pack build?

Batteries, Chargers, and Battery Management Systems.
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RootedSuperuser   10 W

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Can you see anything wrong with this pack build?

Post by RootedSuperuser » Dec 14 2020 3:03pm

Can you see anything wrong with this pack build?
Please, critique and make suggestions.

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eee291   100 kW

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Re: Can you see anything wrong with this pack build?

Post by eee291 » Dec 14 2020 3:45pm

is this your battery or is this a "design" you want to copy?
because if it's the former then what's the point of critiquing it?

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RootedSuperuser   10 W

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Re: Can you see anything wrong with this pack build?

Post by RootedSuperuser » Dec 14 2020 3:56pm

eee291 wrote:
Dec 14 2020 3:45pm
is this your battery or is this a "design" you want to copy?
because if it's the former then what's the point of critiquing it?
You have nothing to add, no technical critique or engineering suggestions? .... Your just doing a post count bump for yourself?

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neptronix   100 GW

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Re: Can you see anything wrong with this pack build?

Post by neptronix » Dec 14 2020 4:07pm

Wow, some people over here are having a monday huh.. :lol:

I cannot really tell the welding quality from the pic.. or what cells are used.. so i can only comment on mechanical matters..

If i had built this, i would add some insulating material between the cells so that they move very little under operation.. because you do not have cell holders to do this..

Also, where is the BMS?
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electric_nz   100 W

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Re: Can you see anything wrong with this pack build?

Post by electric_nz » Dec 14 2020 5:00pm

If you’re only using 3P for around 50A load they are going to be getting pretty warm. I would use a metal case rather than plywood (with appropriate insulation of course.) also wrap a layer of thick pvc insulation tape around each cell to give it some shock protection against a short circuit to the cell next to it, and a cell gasket for the same reason.

goatman   100 MW

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Re: Can you see anything wrong with this pack build?

Post by goatman » Dec 14 2020 5:00pm

if i use solid copper wire i wouldve went 16 gauge or less, thick copper is a heatsink so you probably overheated the cells, if you didnt and got a cold joint then flexing could crack the joint, depends on the soldering though. i switched to using 18 or 16 gauge stranded wire so its a quick 3 second solder joint. if i have recycled/used cells i solder them but im switching to using magnets for new battery builds.

you can spray it with plasti dip if you want to insulate and waterproof it. looks like a house electrician built it, you an electrician?

99t4   100 W

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Re: Can you see anything wrong with this pack build?

Post by 99t4 » Dec 14 2020 10:33pm

My critique: Your innovative mounting method of Liquid Nails seems like it would be very theft resistant :thumb: , and also offer some amount of shock absorption.

What is the V/Ah?

miro13car   1 MW

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Re: Can you see anything wrong with this pack build?

Post by miro13car » Dec 15 2020 11:57am

I cannot see any shock absorbing cushion , those cells will rattle inside
Eplus, Bionx

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eee291   100 kW

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Re: Can you see anything wrong with this pack build?

Post by eee291 » Dec 15 2020 2:36pm

RootedSuperuser wrote:
Dec 14 2020 3:56pm
eee291 wrote:
Dec 14 2020 3:45pm
is this your battery or is this a "design" you want to copy?
because if it's the former then what's the point of critiquing it?
You have nothing to add, no technical critique or engineering suggestions? .... Your just doing a post count bump for yourself?
I've got something useful to add most of the time, I'm not the one posting shoddy built fire hazards online and then asking people for their critique.
Seriously, it's like duct taping my bumper on to the car and then asking people for their "technical critique or engineering suggestions".

All I'm asking for is some context, is that too much to ask these days?
But, if you haven't made the battery yet then you're in luck because you've gotten some good answers already.

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serious_sam   10 kW

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Re: Can you see anything wrong with this pack build?

Post by serious_sam » Dec 15 2020 2:55pm

eee291 wrote:
Dec 15 2020 2:36pm
I'm not the one posting shoddy built fire hazards online and then asking people for their critique.
Seriously, it's like duct taping my bumper on to the car and then asking people for their "technical critique or engineering suggestions".
Apply cold water to the burned area :lol:

999zip999   100 GW

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Re: Can you see anything wrong with this pack build?

Post by 999zip999 » Dec 15 2020 10:19pm

More info on cells and S&P and what controller at what amps ? The important stuff.

goatman   100 MW

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Re: Can you see anything wrong with this pack build?

Post by goatman » Dec 15 2020 11:52pm

you gotta watch out for those Albertans

so its a house electrician, correct?

looks like 20s3p of lk 26650?

and did the builder ground the battery to the frame?

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RootedSuperuser   10 W

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Re: Can you see anything wrong with this pack build?

Post by RootedSuperuser » Dec 20 2020 1:45pm

goatman wrote:
Dec 15 2020 11:52pm
you gotta watch out for those Albertans
so its a house electrician, correct?
looks like 20s3p of lk 26650?
and did the builder ground the battery to the frame?
Image
Not my build or bike, I'm doing this and sending the link to the guy that built it as he thinks there is nothing wrong with his build. He really enjoys showing it off and is proud of his work, so much so he's helping people do their own builds the cost effective way.

1) No vulcanised fish paper insulator ring used on the top of the can. If the copper wire gets hot it will melt through, its a dead short, a thermal runaway will result and a pack fire/explosion will occur.

2) No insulation between the cells, or no gap. The 2 outside cans of 2 different P's, if the wrap tears or melts through, its a dead short, a thermal runaway will result and a pack fire/explosion will occur.

3) Sharp screws and other items rubbing against the cans.

4) Is using a separate port BMS but charging through the discharge port.

No vibration insulation.
No fuse.
No off switch

mxlemming   100 W

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Re: Can you see anything wrong with this pack build?

Post by mxlemming » Dec 22 2020 3:32pm

I think the fact that this hasn't blown up already is testament to the fact that these cells are a lot more robust than we credit them being. Resilience to exploding seems to have improved.

That said, I'm not sure I'd want to be in a car with that in the boot. And it certainly wouldn't be allowed in my house.

There are positives...
1) the braided wire will stop cell detachment on spot welds which can be an issue with nickel strip.
2) good packing ratio.
3) ummm

Negatives
1) any loose write could short
2) 100 amps plus wood? Nope.
3) BMS seems to be supporting the pack weight... Let's try no... To make it worse, the cells seem to be resting on a metal sheet that's probably connected to the lowest cell, seemingly with only the cell wrap to insulate. I'd day this is the most likely point of ugly failure.
4) it's pretty ugly. In a permanently ugly kind of way, not the cover up a few wires and do the tape neater kind of way.

Overall, I'd put a beer on it not exploding, but I'd limit my liability to one not especially expensive beer.

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Solarsail   1 W

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Re: Can you see anything wrong with this pack build?

Post by Solarsail » Dec 22 2020 5:03pm

Cells appear to be LiFePO4 32650, for a total of about 750Wh -- which is too little for a trail/mountain bike. At 115 Wh/kg, they are 2.3x heavier than 21700 NMC, and 3.1x larger.

The thing weighs 6.5kg :o and takes up 3.5L in volume.

By choosing 21700 NMC, he could have saved 3.7kg (8.1 lb) and 2.4L.

LiFePO4 is safer than NMC, but it's very easy to abandon a flaming bike. :lol:

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spinningmagnets   100 GW

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Re: Can you see anything wrong with this pack build?

Post by spinningmagnets » Dec 22 2020 6:01pm

It is very bad form to solder onto the negative ends of the cells. The heat will damage some of the electrolyte inside. The positive ends can take quite a bit of heat, so soldering is an option with the right tools and techniques. Use a 100W iron with a fat tip to be able to provide a lot of heat (instead of cooling off as soon as it touches the room-temp cell tips). Solder fast before the heat has time to creep down into the cell material.

I don't like soldring onto any part of a cell, but it's not horrible on the positive end if you ccomplish it fast.

eMark   1 kW

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Re: Can you see anything wrong with this pack build?

Post by eMark » Dec 23 2020 12:12pm

spinningmagnets wrote:
Dec 22 2020 6:01pm
It is very bad form to solder onto the negative ends of the cells.
Even more so in the center of the can end instead of closer to the side.

Seems like 14S3P (42 cells) would have been a better solution allowing more room for extra wrap around cells, cushioning around pack, and room for a smart BMS.

This design seems more like what NOT to do: "Lets see how many cells i can fit in the available space."

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Chalo   100 GW

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Re: Can you see anything wrong with this pack build?

Post by Chalo » Dec 23 2020 12:28pm

Solarsail wrote:
Dec 22 2020 5:03pm
Cells appear to be LiFePO4 32650, for a total of about 750Wh -- which is too little for a trail/mountain bike.
If they're the Battery Hookup 6Ah cells, then he has about 1150 Wh (but also about 8.5kg of cells).

A cell welder and some nickel strip are cheaper than the lifetime capacity that was taken from these cells by soldering them.
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

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spinningmagnets   100 GW

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Re: Can you see anything wrong with this pack build?

Post by spinningmagnets » Dec 23 2020 5:59pm

Nice avatar, Chalo. Looks good, brother!

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Solarsail   1 W

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Re: Can you see anything wrong with this pack build?

Post by Solarsail » Dec 31 2020 5:27am

Chalo wrote:
Dec 23 2020 12:28pm
If they're the Battery Hookup 6Ah cells, then he has about 1150 Wh (but also about 8.5kg of cells).
I don't think a 32650 LiFePO4 cell can deliver 6Ah. If it does, it probably is one of those mislabeled Chinese cells. I have assumed 4Ah per cell. Is the 6Ah cell a brand name like A123? Or one of those Chinese re-labeled ones?

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Chalo   100 GW

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Re: Can you see anything wrong with this pack build?

Post by Chalo » Dec 31 2020 4:07pm

Solarsail wrote:
Dec 31 2020 5:27am
Chalo wrote:
Dec 23 2020 12:28pm
If they're the Battery Hookup 6Ah cells, then he has about 1150 Wh (but also about 8.5kg of cells).
I don't think a 32650 LiFePO4 cell can deliver 6Ah. If it does, it probably is one of those mislabeled Chinese cells. I have assumed 4Ah per cell. Is the 6Ah cell a brand name like A123? Or one of those Chinese re-labeled ones?
House branded from Batteryhookup. They’re a reputable US supplier that often posts discharge curves or tested capacities for the stuff they sell. I will note they didn’t do that in this case.

https://batteryhookup.com/products/100- ... 0mah-cells

They also sell a 5Ah cell that costs less but weighs the same.

https://batteryhookup.com/products/new- ... 0mah-cells
This is to express my gratitude to Justin of Grin Technologies for his extraordinary measures to save this forum for the benefit of all.

markz   100 GW

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Re: Can you see anything wrong with this pack build?

Post by markz » Dec 31 2020 5:06pm

1375B Adams Road, Bensalem PA 19020

$50 for 48V 5Ah aint bad, but no name generics.

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