Using external battery to charge a T61?

[1kgcoffee]

So, I have a T61 and this anker power supply
http://www.ianker.com/product/79AN7906-BA
which outputs 12v at 1.5 amps.

My understanding is that the battery operates at 10.4v and the ac adapter puts out 20v at 4.5amps, with the machine operating somewhere around 16v. I'm wondering if would be possible to slow charge from the anker dc power supply at 12v, or if this would over time confuse and damage the circuits in the T61? Since the DC input is rated to take much higher voltage.

20000 mAh + a charged battery is enough to last the needed 12 hours

There is another anker that outputs at 16v but that is outside of my budget at this time.

Thanks in advance,
1kgcoffee

[precip9]

No, don't do this. You won't hurt anything, but the machine won't turn on. There is a DC-DC converter circuit that has a low voltage cutoff. It actually will work at 19V, but at some lower voltage, it will refuse to turn on.

But your post has a few other misapprehensions:

1. The machine does not "operate around 16V". There are multiple voltage buses in the machine: 3.3, 5, 12, and the battery bus.

2. The capacity of a battery is not properly expressed by mah. Anker's representation of this battery is misleading, because, from the weight of the thing, it's 20AH at 5 volts, not the higher voltages. So your assumption that it would actually, in combination with the built-in, run the laptop for 20 hours, is incorrect. The meaningful figure for run time is watt-hours, which is given by

Watt-hours = amp hours X voltage. In the case of the external battery you're looking at, the formula evaluates to:
WH = 20 amp-hours X 5V = 100 watt-hours. This is a little more energy storage than the typical laptop battery, which for a T61 factory unit is about 85 watt hours, but not much. And the maximum current the battery can provide at 12V, specced at 1.5 amps, is woefully inadequate for a T61.

So don't do this. It's a minefield of problems.

[1kgcoffee]

Thanks kindly for the detailed response.

Trying to think of another solution. There are cigarette socket travel chargers like this
http://www.ebay.ca/itm/IBM-Lenovo-Think ... 3f0380140e
on ebay... but 16v output, would they work?

[rkawakami]

Yes that would work as it is designed to output the 20VDC that a T61 requires. You could also get something like this: http://support.lenovo.com/us/en/documents/pd011138 It can operate/charge both 20V and 16V Thinkpads (with suitable adapter plug), as well as USB equipment like cell phones or tablets (using their own USB cables).

[precip9]

The specs are correct. But personally, I avoid equipment sourced directly from China without a U.S. importer. The eBay item could come out of the same kind of operation that produces lethal AC chargers, many of which have shown up on eBay (I bought a few.) Because a car charger does not handle lethal voltages, safety is not an issue, but there is still the possibility of laptop damage. Many cars, at least in the past, produced voltage surges upon starting the engine. A good converter handles it. A bad one might not.

For this reason, I suggest you purchase the equivalent off Amazon, in either PWR+ or Anker brands. These are recognized companies with good track records.

There is nothing wrong with a Lenovo product, but it's not a good idea to buy a Lenovo charger off Amazon. The brand is the target of forgers. PWR+ and Anker are not.