Search found 435 matches

by garolittle
Sep 28 2020 12:41pm
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about

A howto thread aimed at beginners, with links on your cell-level fusing and the other pack building details would I think be a great resource for the community. Yes Sir. It has been a long process and trial and error. Lacking high end equipment, I have performed fairly simple tests involving intent...
by garolittle
Sep 28 2020 10:52am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

Great garolittle Lot of learning here. I would love to see that. Cart live. Yes Sir and thanks. I really like ES. This forum is a great resource for learning and for sharing ideas. Building a second prototype kart now. The first one was a blast. Check it out ... https://youtu.be/b_kEQsOaJGc
by garolittle
Sep 28 2020 7:51am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

It is always a good approach to do a simple math with DCIR. From the presentation sheet it should be about 20mR for Samsung 25R. This DCIR value gives an instantaneous voltage drop of 2.2V at 100A load. If you use simple BMS with instantaneous 3V cut-off voltage, you can get only up to 60A from ful...
by garolittle
Sep 28 2020 7:45am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

It is always a good approach to do a simple math with DCIR. From the presentation sheet it should be about 20mR for Samsung 25R. This DCIR value gives an instantaneous voltage drop of 2.2V at 100A load. If you use simple BMS with instantaneous 3V cut-off voltage, you can get only up to 60A from ful...
by garolittle
Sep 28 2020 7:36am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

This may be a dumb question but would 100A be the "moment of death" for this cell? In other words, would hitting 100A kill the cell completely? No. It'll be fine. That 100A spec is for 1 second bursts. Remember, it's mostly about heat. If the duty cycle is low enough to minimise heat production, th...
by garolittle
Sep 28 2020 7:33am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about

LG M36 aka MJ1 would be a better choice for longevity 1C continuous, 3C peak Samsung 35E, SONY VC7 pretty close if you find them cheaper Do not use Sanyo GA, too inconsistent Really like the MJ1 cells. Have not used them recently but may do so in the future. Thanks for the idea. May also try a 2170...
by garolittle
Sep 28 2020 7:31am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about

Current / power output (or input) rating, peak or continuous, 0.01sec vs 10sec needs to be converted to C-rate up front in any such discussion, in proportion to Ah / mAh energy capacity whether on a per cell basis, or a 10P pack, whatever Roger that and thanks. The C-rate for the INR Samsung 25R ce...
by garolittle
Sep 28 2020 7:29am
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

What buss bar ? Most would melt So a pack of 10p for a cart would be 1,000 amps. What controller do you have ? Kart what kart no pics ??? 1,000a 72v 72,000 watts what kind of rubber you use ? On 10in tires. Ok enough. Sorry about that. Pictures attached. The busbar for the prototype battery pack is...
by garolittle
Sep 27 2020 11:25pm
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Re: Question about "Maximum Momentary Pulse" for an 18650 cell

It will probably just put out 100A for an instant before the voltage collapses and current drops accordingly. No way I'm aware of that you can connect to an 18650 will tolerate that kind of current for more than an eyeblink anyway. I wouldn't trouble myself about it. If you want big currents, you'r...
by garolittle
Sep 27 2020 9:06pm
Forum: Battery Technology
Topic: Question about "Maximum Momentary Pulse" for an 18650 cell
Replies: 19
Views: 205

Question about "Maximum Momentary Pulse" for an 18650 cell

The spec sheet for the INR Samsung 25R cell (rated at 20A continuous) shows a "Maximum Momentary Pulse" of 100A. This may be a dumb question but would 100A be the "moment of death" for this cell? In other words, would hitting 100A kill the cell completely? Just curious. In practice I would never exc...
by garolittle
Sep 22 2020 1:01pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

ridethelightning wrote:
Sep 22 2020 7:05am

i couldn't get diy plated copper to work, the nickel would just vaporise off and get bad welds.
Correct. We even electroplated the copper with nickel ourselves. Tried several times. Never could get consistent welds
by garolittle
Sep 20 2020 7:23pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

john61ct wrote:
Sep 19 2020 7:27am
How about just getting the copper nickel-plated?
Tried that with our Kweld but could not get consistent welds. Maybe others have been successful.
by garolittle
Sep 07 2020 2:45am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

BobBob wrote:
Sep 06 2020 5:57pm
It will, but the current can flow in both directions from the Nickel to the copper, so the distance it travells through Nickel is much lower and the cross section of Nickel effectively doubled.
Did not think of that. Interesting information. Really appreciate the response.
by garolittle
Sep 06 2020 5:48pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

Love the copper. This may be a dumb question but would not the current be limited by the resistance of the nickel which connects to the copper? It is true that the copper can carry tremendous amounts of current but it has to get to the Copper first. That’s where the resistance of the nickel would li...
by garolittle
Aug 27 2020 10:03pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

Here is how we power it.
by garolittle
Aug 13 2020 12:45pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

Or... this approach looks very robust and easily made to carry the 350A surge current I'm designing for (borrowed from spiningmagnet's ebike site :D ) Spot weld the strips to the buss bar, then attach the strips to the cells. https://i0.wp.com/www.electricbike.com/wp-content/uploads/2019/03/Battery...
by garolittle
Aug 11 2020 5:00pm
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

Kweld is your best bet. About $200 USD
by garolittle
Aug 09 2020 11:28am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

kdog wrote:
Aug 09 2020 2:00am
Hey garolittle
Whats the conductivity? IACS?
Cost? And where did you get it.
Cheers for info.
Hey Sir. I apologize for not updating my post. I found out later that “Nickel Silver” does have a higher resistance so it would NOT be a good option for high current applications.
by garolittle
Aug 09 2020 11:27am
Forum: Battery Technology
Topic: Spot Welding Copper Strips to 18650 Battery Cells
Replies: 363
Views: 62690

Re: Spot Welding Copper Strips to 18650 Battery Cells

Those welds look really nice. I just looked into this material, but it appears to have a significantly higher resistance than all the other alternatives. COPPER 1.7 x10^-6 Ω.cm ALUMINIUM 2.6 x10^-6 Ω.cm ZINC 6 x10^-6 Ω.cm NICKEL 6.9 x10^-6 Ω.cm IRON 9.7 x10^-6 Ω.cm NICKEL-SILVER 28 x10^-6 Ω.cm http...
by garolittle
Aug 04 2020 5:15pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

flippy wrote:
Aug 04 2020 3:00pm
use a few taps of 80+ grit on the tips every 100 welds or so. just clean the cells with IPA before putting the nickel on.
Excellent. Thanks!
by garolittle
Aug 04 2020 2:37pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

So I am about to start spot welding a 22S/20P pack. I have read the discussion threads regarding cleaning the electrodes and battery cell surfaces and I think I am all set. Most people recommend fine grade sand paper to keep the electrodes clean but what is the best cleaning method for the cells? I ...
by garolittle
Jul 17 2020 9:19am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

agniusm wrote:
Jul 17 2020 8:10am
Received mine:

Image

Image

Thanks
Looks good. Get ready for the best spot welder you have ever used:-)
by garolittle
Jul 03 2020 11:58pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

I would like to ask users of kWeld, how is the status of heat, working temperature? I do not see any sink heaters, or fan? Thanks for answers... Wear a good pair of gloves and point a fan at the pack and the cable holders while welding. Take short breaks to let things cool off. Also, some people us...
by garolittle
Jun 29 2020 6:40am
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

Yes sir. That’s the difference. Excellent engineering of the Kweld
by garolittle
Jun 28 2020 4:36pm
Forum: Battery Technology
Topic: kWeld - "Next level" DIY battery spot welder
Replies: 1193
Views: 170448

Re: kWeld - "Next level" DIY battery spot welder

It is an amazing product isn't it? Welcome to the Kweld World. :)