# OnOff shim maximum current, stacked header, Pibow coupe?
**URL:** https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861
**Category:** Raspberry Pi
**Created:** [May 20, 2017, 4:59pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861 "2017-05-20T16:59:09Z")
**Posts on this page:** 7
**Page:** 1
### Author:  [@thediveo](https://forums.pimoroni.com/u/thediveo)
#### Post date: [May 20, 2017, 4:59pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/1 "2017-05-20T16:59:09Z")
Searching the product page for the OnOff shim, and this forum, I couldn’t find answers to my questions, so hopefully someone here can answer them:
1. What is the maximum current the OnOff shim can handle? Does it allow a Pi 3B with official 7" Touch LCD? Does it handle 2.5A?
2. When using a stacked GPIO header, but not the extra tall one, with 10/11mm headers, can I use the OnOff shim with such a header, place a pHAT or HAT on top with its own female block, and does this still fit with a Pibow coupé casing? (the pictures suggest that the Pibow coupé works, but I want to be sure with using an extension header…)
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### Author:  [@gadgetoid](https://forums.pimoroni.com/u/gadgetoid)
#### Post date: [May 21, 2017, 2:12pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/2 "2017-05-21T14:12:31Z")
The OnOff shim will handle 2.5A yes. It’s designed with the official Pi power supply in mind.
I’m not sure about the stacked GPIO header- my brain is mushy today and I’m having trouble visualising what you describe :D (and, of course, have none of the above to hand to test it :D)
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### Author:  [@knobtviker](https://forums.pimoroni.com/u/knobtviker)
#### Post date: [June 19, 2017, 11:34am UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/3 "2017-06-19T11:34:04Z")
What if I have a power supply of maximum 3A?
Can I expect to fry it or any other side effects?
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### Author:  [@pi2003](https://forums.pimoroni.com/u/pi2003)
#### Post date: [June 20, 2017, 5:03pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/4 "2017-06-20T17:03:51Z")
You aren’t advised to use 3A power supplies with a pi. I don’t know whether it would work. If you try it you may be subject to magic blue smoke though!
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### Author:  [@Paulcheffus](https://forums.pimoroni.com/u/Paulcheffus)
#### Post date: [June 20, 2017, 5:42pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/5 "2017-06-20T17:42:24Z")
Hi
Why?
The Pi will only draw what current it requires from the power supply. You could use a 5A supply so long as it’s only giving 5v.
Cheers
Paul
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### Author:  [@pi2003](https://forums.pimoroni.com/u/pi2003)
#### Post date: [June 21, 2017, 3:01pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/6 "2017-06-21T15:01:44Z")
supports up to 2.5A power supply
is what it says on the product page and to be honest I am more or less talking from that.
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### Author:  [@Paulcheffus](https://forums.pimoroni.com/u/Paulcheffus)
#### Post date: [June 21, 2017, 5:47pm UTC](https://forums.pimoroni.com/t/onoff-shim-maximum-current-stacked-header-pibow-coupe/4861/7 "2017-06-21T17:47:09Z")
Hi
Ah that’s different to what you put in your post which stated “you arn’t advised to use a 3A power supply with a Pi”.
You can use a 3A supply and there is no reason why you shouldn’t, however if you are powering the Pi via the on/off shim then it is only rated at 2.5A. Should the pi draw more than 2.5A due to any added peripherals then you could have an issue.
Cheers
Paul