# Thread: Can You Parallel These?

1. ## Can You Parallel These?

http://www.fusioncontrolcentre.com/F...products_id=45

I was planning on running a shunt and millivolt meter, but this is pretty cool. In conjunction w/ a Fusion Brain, I can see the draw on my amps. Problem is, I'll be pulling more than 50A. Can I parallel them for more amperage?

2. Anyone?

3. Help me out here guys

4. Running them in parallel would increase the maximum current, but would halve the reported value. But if they aren't exactly the same the current would take the path of the least resistance. Just split the power and monitor them seperately. Even more info!

5. I agree.
The worry is if not matched, there is unequal current sharing and kapow! Maybe. (ie 80A with 60 thru one, 20 thru the other).

BUT, these are "current shunts" which are calibated as mV/A.
IE - typically 50mV for 50A or 1mv/A which means the shunt is 1mOhm.

So if two shunts are the same amperage rating and the same mV/A, they must therefore be the same resistance, and therefore matched so they are ok to parallel.
(Help me out here Curiosity - am I sane?)

And the mV/A will be HALF of what each is as Curiosity said (ie, if 1mV/A, it will become 0.5mV/A).

Otherwise, Jaycar have 100A and 200A shunts for (AUD) \$24.95 & \$39.95 each.
(I use their \$13 50A shunt to measure starter motor currents etc up to about 250A - but that's okay 'cos it isn't full-time 250A!)

6. Originally Posted by OldSpark
I agree.
The worry is if not matched, there is unequal current sharing and kapow! Maybe. (ie 80A with 60 thru one, 20 thru the other).

BUT, these are "current shunts" which are calibated as mV/A.
IE - typically 50mV for 50A or 1mv/A which means the shunt is 1mOhm.

So if two shunts are the same amperage rating and the same mV/A, they must therefore be the same resistance, and therefore matched so they are ok to parallel.
(Help me out here Curiosity - am I sane?)

And the mV/A will be HALF of what each is as Curiosity said (ie, if 1mV/A, it will become 0.5mV/A).

Otherwise, Jaycar have 100A and 200A shunts for (AUD) \$24.95 & \$39.95 each.
(I use their \$13 50A shunt to measure starter motor currents etc up to about 250A - but that's okay 'cos it isn't full-time 250A!)
Just do it the right way....
Heres the exact same chip but rated to 130Amps:
http://search.digikey.com/scripts/Dk...me=620-1270-ND
<\$10 shipped

7. I'd just buy two, read both and add their values together.

I'm no electronics guru but I'm 99% sure you're not going to see 100A go through one and 10A through the other.. for the same reason I don't believe in symmetrical gold-plated and pope-blessed "power distribution blocks".

And even if you were to.. it's not going to go pop - its datasheet has its max current at 200A.

But that's just me.

It may well be easier to get the 200A of the same device.

EDIT: Never mind, if you can get it easily from JayCar as above, and don't mind not having a circuit board, definitely do that

8. If they are the same device, they will current share equally. (I said that above and "proved" why. but that may not be obvious).

If 2 in parallel, the reading will be HALF of the real current - ie, 2V for 50A.

Although the peak current may be 200A, as I read it, it won't handle much more than 50A long term.

But I agree with JustChat et al - get a single unit - ie, the ACS754xCB-130 (1.5V @ 100A).

And now having seen the other units at their price, I suggest ignoring my Jaycar comment.

Now why the heck aren't Audio products using these? The impression I get is that many are still using shunt ammeters and (thermal) breakers - not Halls! (Lets not mention caps with shunt ammeters please! Oops.)

9. Originally Posted by OldSpark
If they are the same device, they will current share equally. (I said that above and "proved" why. but that may not be obvious).

If 2 in parallel, the reading will be HALF of the real current - ie, 2V for 50A.

Although the peak current may be 200A, as I read it, it won't handle much more than 50A long term.

But I agree with JustChat et al - get a single unit - ie, the ACS754xCB-130 (1.5V @ 100A).

And now having seen the other units at their price, I suggest ignoring my Jaycar comment.

Now why the heck aren't Audio products using these? The impression I get is that many are still using shunt ammeters and (thermal) breakers - not Halls! (Lets not mention caps with shunt ammeters please! Oops.)

Well, I plan on pulling a couple hundred (maybe 400 or maybe more eventually) amperes through them, and would like to measure it. I planned, originally, to use a few big shunts in parallel, and use an analog meter. But using the Fusion Brain and this, it would be pretty easy to meter it digitally on my computer, no?

How exactly does the Fusion Brain thing work? What software do I need for this to show up on my front end as millivolts (or does it automatically convert it to DC amperes?)? Thanks for the help guys.

10. You're right OldSpark. I was thinking old shunt type as well. An easy way to tell if they balance is to hook them up and read them. They'll tell you what's going through each one. Easy huh? Yeah, with such low resistance it's like taking 0 AWG wire and doubling it. But I still wonder why, with more than 1 amplifier, would you want to measure all of them together when you could see each one individually and also add them up?

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