Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss

MIG welding batteries?

256 views
Skip to first unread message

HeyBub

unread,
Mar 20, 2013, 8:35:52 AM3/20/13
to
I was on the verge of building a capacitive-discharge spot welder to join a
mess of NiCad batteries for cordless tools.

Then I got to wondering. And wondering. Whether a 90-amp MIG welder would
substitute? Seems like 0.030" wire is pretty close to a spot weld...

Anyone ever try this or something similar?

I guess I could experiment, but preliminary cautions and advice would be
appreciated.

Thanks.


bud--

unread,
Mar 20, 2013, 10:34:45 AM3/20/13
to
Capacitive-discharge gives you a limited and controlled energy to the
weld. How are you going to do that with MIG? Maybe put a 5A fuse in the
welding lead to control the time?


HeyBub

unread,
Mar 20, 2013, 12:38:06 PM3/20/13
to
I guess I'll stop the weld when it seems done.

I don't think a 5A fuse would hold up long against a 90A current...


Oren

unread,
Mar 20, 2013, 5:09:49 PM3/20/13
to
On Wed, 20 Mar 2013 11:38:06 -0500, "HeyBub" <hey...@NOSPAMgmail.com>
wrote:

>
>I guess I'll stop the weld when it seems done.

I dunno. With to much heat there is risk of damaging the battery cell?

The spot welder is a better choice -- I think. I have a link to build
one from a (free) 1500W Microwave. I can post them.

HeyBub

unread,
Mar 20, 2013, 6:33:50 PM3/20/13
to
No need. There must be 100 plans on the net.

The simplest seems to be the capacitive-discharge model. You charge up one
or more capacitors whose combined capacity is in the neighborhood of 1 Farad
(with a 12-24V battery charger) and discharge the pack through the substance
to be welded.

There's more to it, of course. The switch is a Thyistron that can handle
2400Amps, and it, in turn is driven by a 12v wall-wart and a doorbell
switch. The electrodes are copper rods, and so on. Parts, however, should be
less than $100.


bob haller

unread,
Mar 20, 2013, 9:42:01 PM3/20/13
to
I have a friend who welds with 2 car batteries in series. Affordable,
works great, and requires no real equiptement other than 2 or 3 car
batteries, some connecting wires and clamps and welding rods

Bob F

unread,
Mar 21, 2013, 1:26:11 AM3/21/13
to
When a teen, I welded using 3 old car batteries, and it worked pretty well. It
would not work well with 2.



bud--

unread,
Mar 21, 2013, 11:08:14 AM3/21/13
to
Lots of luck doing that welding on a NiCd.

>
> I don't think a 5A fuse would hold up long against a 90A current...
>

That is the point. The 5A fuse can pass a much larger current but will
open fast to limit the energy at the weld. It is a kludge to make a spot
welder.



HeyBub

unread,
Mar 21, 2013, 3:09:21 PM3/21/13
to
bud-- wrote:
>>>
>>> Capacitive-discharge gives you a limited and controlled energy to
>>> the weld. How are you going to do that with MIG? Maybe put a 5A
>>> fuse in the welding lead to control the time?
>>
>> I guess I'll stop the weld when it seems done.
>
> Lots of luck doing that welding on a NiCd.

??? What's the problem. The terminal on the battery is, I think, nickle. Why
would there be any unusual difficulty?

>
>>
>> I don't think a 5A fuse would hold up long against a 90A current...
>>
>
> That is the point. The 5A fuse can pass a much larger current but will
> open fast to limit the energy at the weld. It is a kludge to make a
> spot welder.

Ah! I see. How about a 5A circuit breaker? Surely something dramatic would
happen when it sees 2,000A.


bud--

unread,
Mar 22, 2013, 12:19:14 PM3/22/13
to
On 3/21/2013 1:09 PM, HeyBub wrote:
> bud-- wrote:
>>>>
>>>> Capacitive-discharge gives you a limited and controlled energy to
>>>> the weld. How are you going to do that with MIG? Maybe put a 5A
>>>> fuse in the welding lead to control the time?
>>>
>>> I guess I'll stop the weld when it seems done.
>>
>> Lots of luck doing that welding on a NiCd.
>
> ??? What's the problem. The terminal on the battery is, I think, nickle. Why
> would there be any unusual difficulty?

Send a picture of your weld with a 90A MIG welder on a NiCd. Or better,
a video.

>
>>
>>>
>>> I don't think a 5A fuse would hold up long against a 90A current...
>>>
>>
>> That is the point. The 5A fuse can pass a much larger current but will
>> open fast to limit the energy at the weld. It is a kludge to make a
>> spot welder.
>
> Ah! I see. How about a 5A circuit breaker? Surely something dramatic would
> happen when it sees 2,000A.
>

2,000A from a 90A welder?
And when using fuses (and circuit breakers) their "fault current" rating
should be appropriate to the circuit they are used on.

HeyBub

unread,
Mar 22, 2013, 6:21:31 PM3/22/13
to
bud-- wrote:
> On 3/21/2013 1:09 PM, HeyBub wrote:
>> bud-- wrote:
>>>>>
>>>>> Capacitive-discharge gives you a limited and controlled energy to
>>>>> the weld. How are you going to do that with MIG? Maybe put a 5A
>>>>> fuse in the welding lead to control the time?
>>>>
>>>> I guess I'll stop the weld when it seems done.
>>>
>>> Lots of luck doing that welding on a NiCd.
>>
>> ??? What's the problem. The terminal on the battery is, I think,
>> nickle. Why would there be any unusual difficulty?
>
> Send a picture of your weld with a 90A MIG welder on a NiCd. Or
> better, a video.
>

Good idea. I will.

>>
>> Ah! I see. How about a 5A circuit breaker? Surely something dramatic
>> would happen when it sees 2,000A.
>>
>
> 2,000A from a 90A welder?

90A x 120V = 10,800 (momentary) Watts

10,800W / 5V = 2,160 (momentary) Amps

It could happen.


bud--

unread,
Mar 23, 2013, 1:39:14 PM3/23/13
to
90A is the secondary side amps.


0 new messages