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#1 2014-05-27 00:41:50

techknight
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Registered: 2014-05-22
Posts: 449

Mac Portable battery eliminator

Well, Since I dont use my portable enough to justify rebuilding the battery, and since the logic board really isnt safe running on a high current charger, I decided to fabricate a battery eliminator.

I will get one of these:
http://www.ebay.com/itm/DC-DC-Power-Con … 4d1ae1f46a

This will allow me to have a variable input voltage of 9v to roughly 32v or so, and give me 6V at 5Amps. This will fit perfectly inside the battery bay. I then can pull out the MOSFET on the logic board, and redirect it into the battery bay into that regulator. This will allow me to plug in a 9V or 12V brick and produce the proper power into the unit.

For a less "hackish" approach, you could probably use the modem cover/slot and make a plate to hold a DC jack there instead. Anyway.....

Of course I am not stupid, I wont plug that regulator directly into the battery circuit willy nilly, as I know how cheap chinese stuff is. So, ill likely pass it through a small fuse first, and a 6.3V Zener diode and filter capacitor circuit. This will protect the portable in the event of failure of the regulator.

With that little guy in the battery bay, it will still leave me with enough room to stuff my farallon etherwave/PB adapter in there as well, and route that into the logic board. Using the modem port plate for a RJ45 jack. So that leaves me with a source of power, AND with ethernet!

Cant beat that ;-)

Last edited by techknight (2014-05-27 00:43:06)

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#2 2014-05-27 01:53:06

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
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Re: Mac Portable battery eliminator

Sounds good man… can't wait for some pictures…   dial your dc to dc to 6.8vdc…   the 12v buck converter likes a little extra, makes it not work as hard… and if you took a vom to a mostly charged battery pack you would read 6.6 to 6.8 anyways.   heck 7.5v would probably be fine.   i'm sure there is a sweet spot.
the base voltage is 7.5 when the battery is charging...


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#3 2014-05-27 02:56:26

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

Thats why the original charger is limited to 1.5 amps, basically to regulate the charge current going into the battery. Raising the current on the power supply while the battery is in place, will cause a charge-current increase in the battery, and could overtax the switching MOSFETS that are on the PCB.

I figured this out after a while of studying.

Last edited by techknight (2014-05-27 02:56:41)

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#4 2014-05-27 04:06:09

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
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Re: Mac Portable battery eliminator

the only thing… i think the lead acid battery does more then just provide power…  i think it acts as a pretty massive filter as well..   what do you think...


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#5 2014-05-27 17:02:17

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

Batteries really dont make very good filters, their internal resistance is too high.

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#6 2014-05-27 18:54:36

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
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Re: Mac Portable battery eliminator

are we talking lead-acid here?   Thought lead-acid worked as a pretty good filter of noise.


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#7 2014-05-27 23:56:42

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

Not really. For example, we have an old analog charger at work where we charge up dead batteries in cars. Well, soon as you connect up the charger and hit the power, you can hear that "hum" coming through speakers and everything in the car.

Batteries are not good filters. Especially if the incoming voltage supply tops over the current battery voltage.

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#8 2014-05-28 01:47:15

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
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Re: Mac Portable battery eliminator

but does the lead acid in the portable filter noise from the Buck converter etc?


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#9 2014-05-28 22:51:51

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

Nope. The capacitors do this. The battery will only filter any noise thats below its ceiling voltage.

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#10 2014-06-19 02:31:27

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

That took 6000 years to get here. But the first part of my endeavor finally arrived:

20140618_222746%5B1%5D.jpg

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#11 2014-06-19 03:10:25

macdrone
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From: Rainier, Or
Registered: 2014-05-25
Posts: 237

Re: Mac Portable battery eliminator

Why would you want a portable axe into a desktop?

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#12 2014-06-19 04:29:37

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
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Re: Mac Portable battery eliminator

what is that first part?


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#13 2014-06-19 05:05:59

macdrone
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From: Rainier, Or
Registered: 2014-05-25
Posts: 237

Re: Mac Portable battery eliminator

Mac dog gone auto correct.

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#14 2014-06-19 17:42:01

mcdermd
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From: Corvallis, OR
Registered: 2014-05-12
Posts: 972
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Re: Mac Portable battery eliminator

uniserver wrote:

what is that first part?


Looks like a regulator/rectifier from a motorcycle.


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#15 2014-06-20 00:47:09

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

macdrone wrote:

Why would you want a portable axe into a desktop?

Wow, Thanks for the confidence vote! Ill be sure i dont bring up any more projects.

Also, because I dont use it enough to justify the cost of rebuilding a battery that will likely go dead and be killed. No point... Lead acid batteries are very easily killed if your not careful enough.

Last edited by techknight (2014-06-20 00:55:11)

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#16 2014-06-20 00:52:36

techknight
Member
Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

mcdermd wrote:
uniserver wrote:

what is that first part?


Looks like a regulator/rectifier from a motorcycle.

Well ive never worked on any motorcylces so i wouldn't know. Its a buck converter that will work from 24V on down, and gives me 6V at 5 amps. The whole idea behind this is so I can use a 7.5V or a 9V/12V brick SAFELY without blowing anything up ;-)

Last edited by techknight (2014-06-20 01:01:42)

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#17 2014-06-20 03:32:14

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
Website

Re: Mac Portable battery eliminator

techknight wrote:

Wow, Thanks for the confidence vote!

I have 100% complete confidence in you.

Ill be sure i dont bring up any more projects.

The issue is you don't know macdrone and he doesn't know you.

- if you knew macdrone... you would know that he is one of the coolest most generous guys around...
and that he was probably just being a bit of a smart alic with ya...

- if macdrone knew you a little more about you, he would know that you are a serious electronics elite
that goes where most men won't go... and most of the time fixes things that most people around the world have given up on.

So please post post post... your projects might not even be fully understood at this point.
If so, they would know that you are just making a battery eliminator,  and will not axe anything.

buck converter that will work from 24V on down, and gives me 6V at 5 amps.

AWESOME!   wonder how many amps it will put out at 24v...  not that it matters just curious!

can use a 7.5V or a 9V/12V brick SAFELY without blowing anything up ;-)

Yes this sounds great... I agree that 5 amps...,  30 watts should be enough output.
lol i mean the battery you are eliminating is only capable of 5ah,  so we know that 5amps will be plenty,
( for a main power source ), eliminating the battery.   

i see where you are going with this... and i think JDW...   would be quite pleased with your project...!
maybe some one should msg him at the other forum and let him know what is going on!?!??!


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#18 2014-06-21 00:31:02

techknight
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Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

Yea, i may not know macdrone, and i am sure he is a decent guy. I just read it wrong I guess.

Anyway, Assuming 100% efficiency (never possible, but just theoretically speaking here). using 6V at a full 5 amps, a 12V brick as a supply would pull 2.5A max current. now of course most buck converters are anywhere between 70 to 92% efficient. So i average around 85%. Use that when judging what brick to use.

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#19 2014-06-21 02:39:53

uniserver
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From: Sf, Mi
Registered: 2014-05-15
Posts: 956
Website

Re: Mac Portable battery eliminator

well update us as to the next step :-) i messaged JDW...   i know he has been raring to see something of this sorts for quite some time!


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#20 2014-06-21 05:24:53

macdrone
Member
From: Rainier, Or
Registered: 2014-05-25
Posts: 237

Re: Mac Portable battery eliminator

Yes I didn't mean anything by it, and it was not sarcasm.  I guess I am had a purest moment, doesn't happen often.  My thing was is a battery work why install it , but I get your point.  My meaning was is that is what made the portable the portable desktop rather than a plug in Mac.  I redid a battery between the 5120 and 5126 I have and just leave it plugged in.  It may conk out on me but I'll re do it then, and your right once you do your mod you won't ever have to again.

Good work on your part and I'm sorry if I came off wrong.

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#21 2014-08-09 01:18:23

JDW
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From: JAPAN
Registered: 2014-08-09
Posts: 2
Website

Re: Mac Portable battery eliminator

Thanks for the 68kMLA PM, Uniserver.  Sorry for my delay, but I did not see it until today.

TechKnight, you get 5A @ 6V, but what is the max output amperage from that buck converter at the Mac Portable's required voltage of 9.0V?  And is that 9V output enough to run the Portable?

You must also (obviously) connect a 12V brick that can supply the required amperage.

Can you please post some photos of everything wired together and running?  (Photo showing us the exact Power Brick you have attached to the Buck Converter, showing all connections.)

Thanks.

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#22 2014-08-09 03:24:58

techknight
Member
Registered: 2014-05-22
Posts: 449

Re: Mac Portable battery eliminator

I will soon as I get the thing built up.

Right now, ive been busy at work troubleshooting and rebuilding motherboards that would otherwise be dead until I Came along.

The one thing that is bothering me is the buck regulator is 6V, that regulator is nearing the limit of the window-comparator on the PMU system. but we will see.

Last edited by techknight (2014-08-09 03:25:42)

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