WTB and/or FS: Battery pack spot welder in Auckland

Forums › Offers and Wanted › WTB and/or FS: Battery pack spot welder in Auckland

Niel

3267 posts

Uber Geek

Trusted

# 177052 20-Jul-2015 17:44

I've got a pile of 26650 lithium cells that I want to turn into a battery pack for an electric scooter, but so far none of the battery pack rebuilders I can find in Auckland offers a welding-only service. So I'm considering buying a welder for the job and also offering the service to enthusiasts.

But firstly I'm asking if perhaps a GeekZoner in Auckland has one and can offer me the service, or alternatively if I buy one would there be enough interest that I can offer the service to others to help recover the expense? Shipping batteries would be an issue, so this would be for Aucklanders only.

You can never have enough Volvos!

PeterReader

5702 posts

Uber Geek

Trusted

Geekzone

Lifetime subscriber

# 1347863 20-Jul-2015 17:44

Hey, have you listed a price, location and how much shipping would be to other parts of New Zealand? Also if you are asking for a PM make sure your Privacy settings allow your account to receive PM otherwise people can't contact you. Also note if you are selling something we ask you to offer to other members first. Links to private sales (including Trade Me posts) aren't accepted anymore and will be removed.

I am the Geekzone Robot and I am here to help. I am from the Internet. I do not interact. Do not expect other replies from me.

RUKI

1144 posts

Uber Geek

# 1348170 21-Jul-2015 08:51

You can build the spot welder yourself. It is not that hard. Modded transformer from the microvawe oven with the secondary wiring changed to get 2 v with high amperage.
You would need to build an electronic timer to regulate the pulse duration.

That is being duplicated by many enthusiasts around the world and known to be used for 18650 battery rebuilds in laptop batteries.
18650 in modern laptops have petals making them easy to solder instead of welding.

Niel

3267 posts

Uber Geek

Trusted

# 1349513 21-Jul-2015 20:45

Thanks for the thought. I was thinking of capacitive discharge, but 1F capacitors are also expensive. Given that a cheap Chinese welder with digital timer control costs about $250, it might find better things to do with my time than to build one. I'll see if I can convince my employer to buy one, or else I'll buy one myself.

Regarding soldering, definitely not recommended as there are all kinds of safety seals/vents/layers at the positive tip which will get damaged from soldering. Even when soldering to the tabs it is supposed to be at a low heat and for less than 10 seconds.

You can never have enough Volvos!

RUKI

1144 posts

Uber Geek

# 1349628 22-Jul-2015 08:37

.....

Regarding soldering, definitely not recommended as there are all kinds of safety seals/vents/layers at the positive tip which will get damaged from soldering. Even when soldering to the tabs it is supposed to be at a low heat and for less than 10 seconds.

10 seconds is way too long! I do it in a sec. All my pile of 18650 from Samsung has petals.
Soldering is good only to the petals which have already been spot welded to the cell.

On the other hand if you have cells without petals - why being bothered with spot-welding when you can put those inside enclosure with spring contacts?
By doing so - you'll be able to change cells if the need be quite quickly. Power banks from Jay Car have that design.

The other thought to share:

You may wish to consider buying low voltage cell alarm circuits to protect modules from discharge below 3V.

There are two types - with and without relay. One drains less current than another. One just switches the LED on when the voltage drops with optional buzzer and another does the same and switches the load off.

I am planning to DIY few of those for myself as I have all the components and aiming at making one extremely small for the portable mobile power bank.

Niel

3267 posts

Uber Geek

Trusted

# 1349996 22-Jul-2015 18:38

Thanks. My application is for a continuous current draw of 20A, not a good idea to use battery holders. These are A123 cells rated 120A for 10 seconds, or 70A until discharged. If you have not yet heard of Killacycle, then google it and be amazed what an electric drag bike could do ~10 years ago. I have about 25 of these cells and an application, just need a welder. Soldering for 10 seconds was at low temperature as mentioned. High (normal) temperature soldering directly to a cell is bad, but to a tab is okay for a couple of seconds.

You can never have enough Volvos!

RUKI

1144 posts

Uber Geek

# 1350170 23-Jul-2015 08:33

Niel: Thanks. My application is for a continuous current draw of 20A, not a good idea to use battery holders. ....

Agree. When we have built the e-byke the tested draw was 18 Amps.
For applications like yours (e-scooter) it is of course more convinient to use Li modules with poles in the form of bolts. e.g. from EV cars like Nissan Leaf. But I have not seen any wrecked yet to play with.
If you come accross any of those (e.g. Leaf) - please give me a buz.

Niel

3267 posts

Uber Geek

Trusted

# 1350615 23-Jul-2015 16:58

http://www.servovision.com/
These guys sell on eBay and ship via EMS direct to your door... following no battery labelling requirements! So not recommended for the (apparent) safety issue (with LiFePO4), but it is an option. There is a chance though that your parcel might get confiscated. A couple of years ago we received a box of about 10x 12Ah cells before we knew they ignore shipping regulations.

You can never have enough Volvos!

RUKI

1144 posts

Uber Geek

# 1358357 4-Aug-2015 09:22

Have you managed to get spot welding machine? How about to try practicing on Prius cylinder NiMH modules?

I have plenty of modules aka "bamboo sticks" where individual 1.2 cells failed but others are good.

http://www.hybrids.co.nz/nimh-batteries/specs/

Those cylinder modules made by EV Energy (Panasonic - Toyota venture) are also used in Honda hybrids but with different endpoint terminals.

The only concern is how would you control the quality of the spot weld - there are 4 double points around every cell and that connection has to withstand up to 100 Amp currents in Prius / Honda.

Before re-welding there is also a need to cut existing 6-cell module into individual and file off the excess of metal.

I can give you something to try if you want.

Right now there is a Honda Hybrid 2006 with failed modules brought to a garage in West Auckland. There are no donor modules from wrecks - their alternative is either brand new pack from the dealer or DIY modules by using Prius "sticks" as a donor but re-welding the end points.

I can test all those failed and rebuilt modules if someone is keen on dealing with cutting and welding.

Toyota / Lexus Hybrid and EV Battery Expert Battery Test & Repair

Niel

3267 posts

Uber Geek

Trusted

# 1359718 5-Aug-2015 22:23

Nope, made no progress and currently not a priority (yet). Got enough to keep me busy.

NiMH generates hydrogen during charging, and a catalytic recombiner in the cells convert it back to water. The converters generate heat, which is why they get hot during (fast) charging. So I'm not surprised they fail in electric cars. Add to that, their charging efficiency is 70% so there is significant waste to charge them. If only these guys would bite the bullet and go for reliable/safe LiFePO4.

Sorry, can;t help with the bamboo sticks.

You can never have enough Volvos!