Hoang, without knowing more about the internals, I can only make some guesses, but if you have access to a multimeter we can figure this out.
Im guessing that those adapter tips work like the adapter tips that come with universal laptop AC adaptors, like from Targus, Kensington, and others, where you select the voltage range on the battery, and the tip reduces the voltage, by means of a built-in resistor, to whats required for the particular laptop. To check this: with the battery charged, and the battery voltage set to 16 to 20 volts, read the voltage at the output cable with the meter, and note that voltage. Then, install a tip, read that voltage and note it. Do that with several tips; if the voltages vary, then my guess is correct.
If one of the tips with a standard barrel connector outputs 15.5 to 16 volts, mark it.
Do that much, and post your results here, then well proceed, okay?
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Any idea if I should go 14.5 volt (4S) for a 2012 Retina (I believe 16 volts) or 5S 18.5 volt which could be risky? I wanna get a 5S 8000mah which should have a whole lot of power?
I'm doing a lot of reading on lipoly safety etc. Lions seem a lot more safer and rugged compared to these, so much care is needed
First, something that I think should have been said much earlieryou can skip the next three paragraphs, if you like.
A genuine Apple power adapter, or charger, varies its output voltage depending on its load, because Apple uses switching voltage regulators (and a switching power supply, but dont confuse the regulator with the power supply; a switching power supply might still output its voltage through a linear voltage regulator.) This makes it safe to use any GENUINE Apple MagSafe adapter with any model of MacBook; you wont be happy with a 45 watt MBA charger on a larger MacBook, but it wont do any harm.
As for the counterfeit, or clone, non-Apple power adapters; there are none that Ive heard of that use either switching power supplys or switching voltage regulators, and thats why the charge indicator LEDs dont work properly, even if the charger works otherwise, but, more importantly, I believe that this is the main cause of the problems, including damaged MacBooks, that is associated with the clones, although some of those clonesthe worst onesare pure junk to begin with.
The different Apple adapters (45 watt, 60 watt, and 85 watt) output different voltages, and you want an external batterywhich outputs a raw voltage instead of a voltage regulated through a switching regulatorto match the input needs of your MacBook. This thread has been about making an external battery for the MBA, which should use a 4 cell LiPo to function properly.
I believe that your Retina MBP uses an 85 watt chargeram I correct?
At maximum load, like when charging a MacBook with a discharged battery, the 85 watt charger supplies up to 18.5*volts, and at minimum load it supplies something around 16 to 16.5*volts. Those requirements are perfectly suited to a 5 cell (5s) LiPo battery.
The Micro-Amp-Hours (mah) only affects the batterys runtime; an 8000mah battery will run your MacBook about 10 times longer than an 800mah battery would, and an 800000mah battery wont hurt your Book, it would just be hard to lug around.
LiPos are quite safe, I think, and most of the horror stories about them arose from problems that have been addressed by the industry. There is always a potential for dangerjust as with the fuel for your car, or the gas stove in your kitchen, or even driving to the storebut if your equipment is in good condition, and you use reasonable caution, you shouldnt have any problems. Do use a balanced charger; your battery will be much safer, and it will last 2 to 3 times longer, too.
For the difference in weight, and weight alone, I want LiPos for everything portable. If weight doesnt matter, but just power and amp-hours, an SLA cant be beat.
