DIY battery for macbook air?

[cwah]

Hello there,

It's not related to EV this time, but I thought it may make sense to post it here.

I'm going to buy a new Macbook air and I want an additional battery to power it when I travel.

According to this seller, he manage to send the exact power rating thanks to micro chip in the plug here:
http://www.aliexpress.com/item/Morewer-31200mAh-External-Battery-Pack-Power-Bank-for-14-5V3-1A-45W-Interface-Type-13-5/622582611.html

So macbook air standard power rating is 14.5V 3.1A. But you can see this battery isn't set to any voltage or amperage. And seller told me micro chip inside the cable plug would adjust it? I don't really believe him??


I was wondering if that would make more sense to have a cheaper model:
http://www.aliexpress.com/item/2013-New-Arrival-20000Mah-Power-Bank-Mobile-Phone-USB-Charger-Battery-Pack-for-iphone-Laptop-Netbook/901024753.html

Then set voltage to 16.5V and plug it to my macbook air? Would that work even if the standard plug has 14.5V3.1A setting??

Thanks

 

[major]

According to this seller, he manage to send the exact power rating thanks to micro chip in the plug here:
http://www.aliexpress.com/item/Morewer-31200mAh-External-Battery-Pack-Power-Bank-for-14-5V3-1A-45W-Interface-Type-13-5/622582611.html

So macbook air standard power rating is 14.5V 3.1A. But you can see this battery isn't set to any voltage or amperage. And seller told me micro chip inside the cable plug would adjust it? I don't really believe him??


I was wondering if that would make more sense to have a cheaper model:
http://www.aliexpress.com/item/2013-New-Arrival-20000Mah-Power-Bank-Mobile-Phone-USB-Charger-Battery-Pack-for-iphone-Laptop-Netbook/901024753.html

Then set voltage to 16.5V and plug it to my macbook air? Would that work even if the standard plug has 14.5V3.1A setting??

These look similar to but smaller than some I had and tested here http://endless-sphere.com/forums/viewtopic.php?f=31&t=48364&p=712021#p712021

On mine, it had a fixed output voltage which was regulated at about 15.5 to 16V. There was no way to easily change although one customer did manage to disassemble the unit and modify a resistor (R30) on the regulator board to reset the voltage. Mine were 3.5A normal with a max of 4.5A. Current draw was load dependent. They worked fine on a variety of laptops. Many of those laptops were not too sensitive to voltage.

I can't say whether the units you're looking here could actually be voltage adjusted. And I couldn't say if a unit like mine at 15.5V would work work with your computer. But you can look at my referenced post you see what's inside mine and some tested results. Look for watt hours (Wh) for the rating. Ah or mAh are deceiving as they base that on different voltage cells. Wh is the true measure of how long it will run your device. And the stated Wh rating is likely actually overstated. The manual on mine said 300Wh but they tested to about 240 Wh. The first one you link is 100 Wh. The second one looks about half that size.

I and several others have used the units I have and been very pleased with performance.

edit: I forgot to mention. A friend uses one of my 16V units with a number of his devices (iphone, ipad, etc.) all of which required different voltage and different adapters. We found the all his devices had automotive 12V adapters available and the 12V adapters worked fine on the 16V power supply. The automotive 12V adapters were typically rated for 11 to 16V.

 

[cwah]

Do you mean you are selling battery pack for laptop use?

I purchased 2 battery from the seller as he has the Macbook air Magsafe connector. The battery however is not exact to the macbook air charger requirement (14.85V 3A). But apparently it does work.

But it should be easier to solder the Magsafe lead to the battery anyway.

I'm not sure the load has much impact to charge the macbook

 

[major]

Do you mean you are selling battery pack for laptop use?

I was. Pretty much all gone. One left on eBay. Works great on laptops. I use it a lot.

 

[cwah]

what is your ebay ID? Do you make more of them? What is your expected return pricing?

 

[major]

what is your ebay ID? Do you make more of them? What is your expected return pricing?

Item number: 171072171165

I was reselling a surplus lot, not making them.

 

[spinningmagnets]

When a car is running, the system voltage of the car is about 14V, and the resting voltage of a fully charged system (with the car/alternater off) is around 13V. This leads me to believe that the 12V charger for laptop computers will run on a 14V input without damage.

It may be a worthwhile experiment to use 4S LiFePO4, which I have read has an average voltage of 3.2V per cell, resulting in a pack of 12.8V, and if you charged them to 3.6V per cell, it would have an output of 14.4V

Individual cylindrical cells can be found in the garden department of the large hardware chains, as these cells have been used for solar-charged LED lights. You could make a pack about the size of a briefcase as a back-up supply for any component that can be charged from 12V (laptop, cell-phone, LED flashlight cells, etc).

Another more expensive (but higher quality) solution would be to make a bank of 12V lithium cordless drill batteries. Some inexpensive device like the cordless LED lights that use the drill packs can be harvested to create the row of sockets for the paralleled 12V packs.

 

[dnmun]

the rules have changed with respect to a lithium battery transported on planes. i think they only allow it if the battery is inside the device.

 

[cwah]

Hmm... If I can't make it through the plane there are no reason to bid on it lol :lol:

Anyway I hope the ones coming from china (80WH) will be good.

 

[Ykick]

Large battery TSA guidelines:

http://safetravel.dot.gov/larger_batt.html

 

[major]

Hmm... If I can't make it through the plane there are no reason to bid on it lol :lol:

Actually the one I have would conform to the larger lithium ion battery per http://safetravel.dot.gov/larger_batt.html and be allowed. It is rated by the manufacturer at 300Wh although it tested only to 240. But I can't ship it overseas (or at least don't know how to for a reasonable cost).