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Power supply unit...out of old p/c

Bit of DIY

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john stones 131/08/2015 18:50:26
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10577 forum posts
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This suitable for making a power supply unit for charging lipo's, biggest I use is 4s 3300mah, but am fed up charging one at a time so will be buying a charger to do four at once.

John

psu 003.jpg

Hugo Strugstad31/08/2015 19:07:21
1 forum posts

It is possible to use this, but it cold have has more Ampere. Chargin 4s 3300mAh batteries at 1c will require 49watts. Charging 4 of those, almost 200W. Your PSU can deliver max 14 Amps (168W at 12 v). If this is constant max current you may be Abel to charge 3 of your batteries at 1c simultaneosly.

John Privett31/08/2015 19:27:12
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I think that PSU will struggle to charge 4 x 4S, 3300 batteries at the same time. It's slightly worse than Hugo suggests, as at the end of the constant current phase of the charge, the charger has to supply 3.3A at 16.8v which is a little over 55W. Of course no charger is anything like 100% efficient, so the input poser to the charger will need to be more. How much more? I don't know! I'd be surprised if it was as little as 60W input per battery - which means 5A, or if all 4 reach that stage at the same time 20A. The PC PSU pictured is only rated at 14A at 12v.

I use an old Microsoft Xbox PSU (a tenner off ebay), but it too would struggle with your requirement. It is rated at 16.5A at12v - a touch under 200W. It copes fine with the biggest batteries I charge - 2 x 3S 2700 mAh plus 2x 3S 3000mAh together.

john stones 131/08/2015 20:14:44
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10577 forum posts
1480 photos

Cheers, I think I follow you...this one should be o.k then, scroll down it has all bumf.

John

John Privett31/08/2015 20:55:22
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5959 forum posts
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That one's good for 36A on the 12v rail, according to the spec, so much more like what you'll want.

I assume you've already checked the numerous articles online specifying what you need to do to make a PC PSU function as a charger supply?

Essentially (apart from modifying the connectors) you'll need to bridge two of the terminals (could do it with a switch if you wanted) that signals the PSU to actually turn on the outputs.

Secondly - and this might not be needed on recent PSUs - you may need to put a load on the 5v line. Without this the 12v supply may not run at the correct voltage - as I said though, this might not be a problem these days. On the one I previously used, I put a 12v car bulb across the 5v line. It glows orange and as well as providing a load, reminds me that it's switched on - as if the fan whirring away isn't already enough of a clue!

john stones 131/08/2015 21:04:20
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10577 forum posts
1480 photos

Thanks John, this one has an on/off switch at the back, yes I've been viewing the tutorials on converting one and i'll be asking questions when i'm unsure.

John

John Privett31/08/2015 21:57:35
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5959 forum posts
236 photos

The on/off switch at the back just "powers up" the power supply. Even when switched on at the back, it doesn't actually do anything useful until the two connections mentioned earlier are bridged.

This is mimicking how it functions on a PC. Many PCs have that little switch on the back of the PSU, and I'd say that 99.99% of them are never turned off at that switch. So the PSU is 'live' at all times the PC is plugged in to the mains. But only when you press the "power" button" (which bridges those two connections mentioned earlier) does the PSU, and consequently the PC, burst into life.

john stones 131/08/2015 22:12:10
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10577 forum posts
1480 photos

Cheers John, i'll ask questions when it turns up.

John

Gavin Mack01/09/2015 10:02:29
83 forum posts
15 photos

see link below on how to use ex server power supplies which are higher power than pc power supplies and easier to convert

**LINK**

Brian Pearson01/09/2015 10:11:45
12 forum posts
I used two dps 600b power supplies I got 9ff ebay for twenty quid. Then wired them in series to give 24v. I can charge whatever I want....obviously limited to your charger. The details on how to do it are on the Web. You MUST isolate one unit. But it's fairly straightforward.
Masher01/09/2015 10:54:58
1103 forum posts
79 photos
Posted by Gavin Mack on 01/09/2015 10:02:29:

see link below on how to use ex server power supplies which are higher power than pc power supplies and easier to convert

**LINK**

That's what I have done - good quality and cheap

Andy Meade01/09/2015 11:04:17
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2605 forum posts
679 photos

Thanks for the link - I have 4 of those supplies in the loft I can use. I remember they were very noisy though!

FlyinBrian01/09/2015 12:21:32
518 forum posts
Posted by Masher on 01/09/2015 10:54:58:
Posted by Gavin Mack on 01/09/2015 10:02:29:

see link below on how to use ex server power supplies which are higher power than pc power supplies and easier to convert

**LINK**

That's what I have done - good quality and cheap

Me too, very easy mod and works very well.

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