Computers & Electronics

3 prong grounded vs 2 prong AC Adapter/laptop charger

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May 11, 2009
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Debtario

3 prong grounded vs 2 prong AC Adapter/laptop charger

My lenovo AC adapter died (square tip type), I was looking at a replacement and noticed the cord on the input side of the adapter has no grounding prong. My old 65W adapter did have a ground plug, yet this 90W OEM unit has only 2 prongs. I figured I'd upgrade to a 90W adapter just so it doesn't have to work as hard, my old one would get very hot.

I know the tiny/AIO desktop adapters and Thinkpad chargers are interchangeable, same voltage, same connector. That said, the lenovo product page boasts about better reliability (something like 30000 power-on hours vs 8760 for thinkpad chargers), which sounds like upsell baloney to get people away from cheap/available thinkpad chargers.

I started scouring ebay and noticed that some OEM lenovo chargers have a ground plug, some do not, though interestingly most of the cheap "compatible" generic adapters do seem to show a grounded plug.

Does the ground matter on a laptop adapter? From what I can tell the output is just 2 wire DC so it's not as if the ground does anything, at least not for the machine. The chargers are also encased in plastic, yet there must be some EMI or other design consideration that factors in. I still find it odd one adapter would have a ground but a higher amperage one would not.
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Nov 25, 2004
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most of what u find on ebay will be knock offs for ac adapters.
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Nov 6, 2014
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Lenovo makes adaptors with and without ground. As long as it OEM lenovo you should be fine with the same or higher wattage...don't worry about it.
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fordmaple wrote: Lenovo makes adaptors with and without ground. As long as it OEM lenovo you should be fine with the same or higher wattage...don't worry about it.
Thanks, I figured I was over-thinking it. I had a chance to buy a new adapter off ebay (which sounded suspect - seller plastered their logos over the lenovo branding and the description was inconsistent, plus wait for the slow boat from china) or a used OEM one for around the same price. Went with used OEM for $25, the retail price for brand new from lenovo is almost what this machine is worth, lol.

Got reading about it and how there could be a voltage float above ground etc etc. but then if ground were so important they wouldn't let thinkcenters and thinkpads have interchangeable power bricks!
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Jun 27, 2004
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I've always wondered why they changed from 3-pin to 2-pin here. In Europe, they still had 3-pin for the round, 20V chargers.

I would have stuck with a 65W charger, since they are smaller. The dude I bought my ThinkPad from gave me a 90W brick, so I'm on the lookout for a 45W one.

BTW, you can get adapters so you can use the old, round pin chargers with the rectangle plugs. I've seen dudes selling used round tip chargers for as low as $10. One time, I bought a couple 90W ones at Salvation Army for $5 each :D .
https://www.aliexpress.com/item/32972104305.html
https://www.aliexpress.com/item/10000045220475.html
I like the cable one because it takes the stress point away from the charger cable and places it on the adapter, instead.
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Oct 13, 2008
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Realistically it makes no difference.

My personal Asus laptop is a two prong. My Lenovo work laptop is a three prong.

My battery charger for Dewalt and Ryobi is two prong.

Toaster is two prong.

Microwave is three prong.

Coffee maker is two prong.

TV is two prong but the receiver is three prong.

Corded impact drill is two prong.
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rabbit wrote: I've always wondered why they changed from 3-pin to 2-pin here. In Europe, they still had 3-pin for the round, 20V chargers.

I would have stuck with a 65W charger, since they are smaller. The dude I bought my ThinkPad from gave me a 90W brick, so I'm on the lookout for a 45W one.

BTW, you can get adapters so you can use the old, round pin chargers with the rectangle plugs. I've seen dudes selling used round tip chargers for as low as $10. One time, I bought a couple 90W ones at Salvation Army for $5 each :D .
https://www.aliexpress.com/item/32972104305.html
https://www.aliexpress.com/item/10000045220475.html
I like the cable one because it takes the stress point away from the charger cable and places it on the adapter, instead.
I don't mind the size as it will be connected to a AIO desktop, that's what got me thinking if the grounding matters.

I heard good things about those round to square adapters, that was my original plan for getting a cheap replacement power brick. Unfortunately my local used market is dry right now (someone wanted to sell me one for $15 AND a carton of cigarettes...) and the old round connector adapters don't sell for much of a bargain on fleabay after shipping.
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Nov 21, 2011
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Grounds are used where there is a risk of shock on the outside and mandated for appliances which pose such a shock made after a certain date. Plastic power adatapters don't need it. Some manufacturers use 3 prongs to ensure live and neutral connect to the correct lines, others simple use larger neutral prongs to get the same result. Some designs don't care which way they are plugged in.

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