MikeGyver: The Mac Solution
You use a Mac, then you know that everything got a little more complicated with the MagSafe connector. There are very few ways to get an external battery to work with your MacBook. One roundabout way is to output 12 V to a cigarette adapter and use Apple’s Airline MagSafe adapter. Only the PowerGorilla and XP18000 support that option, but the cigarette adapter is separate purchase in the case of the XP18000.
There is a big problem with this suggestion, though. The current Airline MagSafe connector doesn’t actually step up the voltage. It just delivers 12 V to the computer, which is enough to keep the notebook alive. Unfortunately, it isn't enough to charge the battery. In fact, it doesn’t even really fully power the larger 15.6" and 17.3" MacBook Pros. The larger systems switch from 16 V to 19 V during heavier workloads, so you'd only really slow down the rate of discharge.
Apple is the only major notebook vendor that supplies a branded non-charging auto option, which makes this somewhat of an anomaly. Some people have resorted to modifying the Airline MagSafe adapter, but it doesn't come with a charging circuit. No amount of modification is going to solve your charging problem.
There are options coming from HyperMac (HyperJuice looks interesting) and QuickerTek. Trouble started a few months back when Apple claimed that HyperMac was manufacturing cables with MagSafe connectors, violating the Cupertino-based company's patent.
Meanwhile, there was Mike Lee of MikeGyver, plugging along. Before MagSafe was even a blip on the radar, Mike made mods for PowerBooks. Apples employees even use his kits because he warranties his work. Mike actually cuts a MagSafe cable off of a retail Apple power adapter and modifies the input end to accept the 16 V plug used by the last generation of IBM ThinkPads. This simple adjustment allows you to charge your MBP, provided you have his modified cable and an adapter that can output to the old 16 V ThinkPad tip. This is completely legal because it's not a counterfeit Apple product. It is simply a mod, and selling a mod is legal under the principle of first use.
There is a downside to this, though. You must use either use a modified Apple power adapter from MikeGyver or switch over to a third-party power adapter.
You can attempt to do this yourself, as others have, but it's an involved process. The elastic sheath on the cable makes it hard to modify, since you need to always keep it taut and straightened out. If you are willing to supply your own adapter, or if you have a custom setup requirement, Mike usually just charges the labor fee for modifying the plug.
There are a number of quirks associated with this approach, but the point is that it works. In fact, we have tried it on new 13.3" MacBook Pro using all of the batteries in our roundup. It works without flaw.
If you are going to attempt to do this yourself, you need to be careful. One of the criticisms of the MagSafe design is that the contacts are too small for the the charging current. Furthermore, the magnet used in the connector attracts iron filings and other ferromagnetic materials. Just Google "MagSafe fire." After creating your own cable, your MagSafe plug may be dirty from its time in the lab. Play it safe and clean up the plug. You can do this with candle wax.
- Drip candle wax onto a surface.
- Knead it until it is just slightly warm and malleable.
- Press it against the MagSafe connector. The wax will pick up any filings or ferromagnetic dust.
- Wipe down the MagSafe connector with a soft cloth to get rid of the wax.
Do not put the MagSafe connector in contact with hot wax. Only do this after it has cooled. A magnet will lose part of its magnetic force when it comes into contact with heat (100 °C). You can also use masking tape, but warm wax is the surest way to get rid of even the smallest filings.