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MCM4 HS custom battery with Spot Welder


Battling
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Thanks.
It's cheaper but the most important for me was the ability to make my own batteries when I want ( I'm posting the third episode with the second battery), with my own security criteria as I had a bad experience with my previous EUC battery whose cells died after 2 months and the seller (Gearbest) refused to apply the warranty.

As for the costs :

- MCM4 HS with no battery : 460€ from Ali
- Spot Welder : I had all the stuffs and bought only the SSR, the foot pedal switch and, for the second battery, the copper needle : about 14€
- Panasonic 340Wh Battery : 132€ for the cells and about 30€ for the other components ~ 160€
- LG 420Wh Battery : 171€ for the cells and about 30€ for the other components ~ 200€

For 840€ I had an MCM4 HS with 760Wh battery, so Yes, it was cheaper. Now, this wheel is cheaper : when I bought it, the 132Wh model was about 550€ and now it's about 500€, so the 760Wh DIY version would cost 790€.

 

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I think your cat was an electronics technician in a prior life.  ;)  He likes to supervise your work.

Have you done a test pull on the double upped nickel tabs from a cell with a pair of pliers to verify the contacts?  Do you have an old, dead cell to experiment on?  Looking at the photos your spot welds look very nice, but I'd be curious especially with two layers of tabs how well they are spot welded to the battery terminal metal.  Are you able to apply some pressure to the tab as you are welding or do you think that isn't necessary as long as the tab is fairly flush with the terminal end?

Edited by HunkaHunkaBurningLove
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:) I think too, he also participates sometimes.

Yes, I did several tests with my fingers, with pliers and even with another battery like here

iXWWjCM.jpg

You can see the the marks on the strip and batteries.
These tests allowed me to fix the durations of the SSR commutation at what I think was the optimal values for my configuration.

At the end, my strips were more hardly fixed that the laptop ones I used for my tests.

Edited by Battling
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Very nice job! :)

Does the microwave-oven transformer drop the voltage? Ie. is the idea to use (very?) small voltage with high amps? How much amps does that put out during welding, hundreds?

I'd be interested in building one, but don't have a scrap microwave oven, plus I'm not very confident when it comes to working with mains voltages (230V RMS)  :P

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10 hours ago, Battling said:

Thanks.
It's cheaper but the most important for me was the ability to make my own batteries when I want ( I'm posting the third episode with the second battery), with my own security criteria as I had a bad experience with my previous EUC battery whose cells died after 2 months and the seller (Gearbest) refused to apply the warranty.

As for the costs :

- MCM4 HS with no battery : 460€ from Ali
- Spot Welder : I had all the stuffs and bought only the SSR, the foot pedal switch and, for the second battery, the copper needle : about 14€
- Panasonic 340Wh Battery : 132€ for the cells and about 30€ for the other components ~ 160€
- LG 420Wh Battery : 171€ for the cells and about 30€ for the other components ~ 200€

For 840€ I had an MCM4 HS with 760Wh battery, so Yes, it was cheaper. Now, this wheel is cheaper : when I bought it, the 132Wh model was about 550€ and now it's about 500€, so the 760Wh DIY version would cost 790€.

 

Again: Respect!

And this is also much Money safed, as i can see now...

I didn't exspect the cells and BMS to be under 240-260 Bucks!

10 hours ago, Jason McNeil said:

@KingSong69 not everything is life can be reduced to cost ;) What about the innate sense of joy that every man secretly has in completing some DIY project, or just the challenge?  

Didn't you read the first 2 words ....Wow and Respect ;-) ???

As an EUC Enthusiast with 3 wheels just  in a half year i know some things are not "only costs" :-)

Was more interested if i can do this, too.....AND saving some Money B) aaaah: I have to take some Pictures of my KS18 fan modding....showing my DIY Projects....

 

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@Battling: Great Work documented by you!

Just in case you plan once to parallel some of your packs :  http://forum.electricunicycle.org/topic/4870-ks-16-680wh-jittery-ride/?do=findComment&comment=54542

So then you should "cascade" your packs, shorten the reverse voltage protection diodes on the second (following) packs and as a safety measure choose a BMS with more than one Mosfet for "overvoltage/charge" protection. (Or just the space to solder some more mosfets in...)

Also as posted here  http://forum.electricunicycle.org/topic/2247-decrease-charging-time-5a-high-current-charger-mod/?do=findComment&comment=29975 and in the following posts there are many parameters for shutoff/safety conditions controlled by the BMS. Maybe it would be worth to find a BMS which can be programmed?

 

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Thanks @esaj.

In deed, this transformer is modified for dropping the voltage. With 3 coils, I'm at 2.31V

nwzEZuu.jpg

Regarding the current, I really don't know its value as my Ampere-meter doesn't exceed 20A!

The transformers have a good efficiency so Power in the primary almost equals Power in the secondary. So Pin ~ Pout

I've just measured the current in the primary : 1.68A

xMbRAqX.jpg

So Pin = 230 x 1.68 ~ 386VA
Iout = 386/2.31 ~ 167A

The needles are safe, I used to manipulate them by hands while welding, so, if you make a case, there's no risks.

On the other hand, when opening the oven, you have to take care at the big capacitor which could stock energy for a while. You had to discharge it or disconnect it with protected pliers for example.

122802-z.jpg

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1 minute ago, Battling said:

...Over-voltage/charge protection is less impacting for me, that's why I shunted one of the 2 BMS...

That only gets important once the cells age and start to fail - then theoretically one/some cells could get overcharged...

1 minute ago, Battling said:

...I agree with you, the best BMS would be a DIY one.

Or at least self configured - so one knows the limits and can set them oneself.

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A recent add concerning the charger : Initially, the charging time was about 5H.
Thanks to @esaj's links http://www.aliexpress.com/item/1set-GX16-3-Pin-Male-Female-Diameter-16mm-Wire-Panel-Connector-L71-GX16-Circular-Connector-Socket/32658447630.html, I could now use my old TG F3 charger in parallel. The charging time is now about half

KoHl2Tk.jpg

uxyRltH.jpg

9WpZExz.jpg

UYUfxAX.jpg

I'm thinking about putting the Y in a box with a relay controlled by an attiny85 with a voltage or current detection (voltage divider or ACS712)

 

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  • 7 months later...
  • 3 months later...

Hey. Made a spotwelder and finished my new batterypack. I forgot the cardboard insulators underneath the very last row though! How important is that? Do I need to tear off the nickelstrips and put insulation underneath and re-attach? Won't the batteries get weaker if I do another spotweld on them? Also there was a spark when I plugged in the charger and it looks like the light on the charger glows brighter than when I charged the old batterypack. Everything seems to work but haven't had a testdrive yet.

image.jpeg

Edited by Cryptonitor
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@KingSong69 Cells are 18650, 3,4Ah 3,7V. Max discharge just 8A but they were so much cheaper than 40A discharge cells that I can replace the pack 4times before it costs as much as a 40A max discharge pack. Wheel is Esway E3 MarsRover. Batterypack fully charged and now there is no spark or sound when i plug in the charger. Sealed up the pack with glue and thinking about just heatshrinkwrapping it and do a testride. So strange that there would be spark when I plugged the charger in first time though! Afraid I'll damage the motor/electronics/charger.

EDIT: Tried connecting everything and tilting the wheel (driving forward) and there seemed to be alot more torque and more rapid acceleration. May be that I've gotten used to the old worn out batteries

image.jpg

Edited by Cryptonitor
Decimalpoint error corrected
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Really important question:

Is this "Soshine 3400mah" cell the "protected" Version with a small pcb upside? is one of this cells a liiiitlebit longer than the normal or old 18650 version?

And: Did your Esway E3 run on only one of this 16series packs?

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@KingSong69 yes they are the protected version that are slightly bigger. The wheel ran on just one 16-pack. Assembled and tried to testride but I couldn't even get on before it died! Had to plug in charger to be able to turn it on again. Same problem second time. Have I blown my BMS or something? Thinking about that spark when I plugged in charger first time... Or maybe the safetykajigger built-in to the new cells have blown?

EDIT: tried just tilting the wheel again after plugging in the charger so I could turn it on. I could run it along wih my hand but immediatly after I stepped on it cut off and died again.

EDIT: Starting to take it apart again to hack off those protection circuits. Crossing fingers!

Edited by Cryptonitor
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Ok,

 i can only WARN you very heavily to use this -sorry please- selfmade crap combo!

Reasons: Behind this Soshine cell is a panasonic cell that is only capable of max 6 Amps! 

Because of this Soshine protects this cell with a PCB....

But Pcb protected cells have NOT to be in seriell config with BMS, where the BMS overtakes all protections...

Think about just one or two cells shuttiing down....then the BMS shuts down! And you fall!

 

You HAVE to use minimum 10 AMP capable cells in a an EUC wheel, and in an EUC wheel only running on one 16pack...i would go for MINIMUM 15, better 20 Amp cells.....and these have to be unprotected!!

 

You have to tried to save money on the wrong end.....that could have as worst case make you faceplant very bad!

Sorry, strong words, but it was dangerous what you have done!

By rolling by hand no amps are reached, but with your weight this all dont work as 7-8amps are reached easilly!

Edited by KingSong69
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