replacement bettery for T400

[KG789]

Hi. i'm a newbie here. I need to find replacement batteries for both my T400 and my R400. I am thinking that what I learn about how to do this for my T400 will apply to the R400. When I have looked at websites that say they can help me find what battery I need for my T400, they want to know what model I have. They list numbers that I don't see on my laptop or on the battery. The battery says TIS2217-2548, R1122J-733,NOM 10.8V, 7.8 AH, 85 WH. The type (as shown on the back of the laptop on a label) is listed as 7417TPU. I ordered a battery from en ebay seller that said it would fit a T400 (and an R400) but I didn't look at the specifics for the battery. For the one I purchased: it says 11.1 V Battery Capacity: 5200mAh.

What numbers are important in determining if a battery is the right one? Is it the Volts? the Amp Hours? The Watt Hours? Or all 3? I am assuming that just because a battery claims to be the right one for a T400, doesn't mean it's right. And clearly I don't want to damage my computer by using the wrong battery or at the very least have it not work. And, does it matter what "type" of battery I get, as in original (OEM?) vs. some other? Thanks.

[KG789]

Sorry about the typo in the title Bettery - should be Battery!

[TonyJZX]

I think only mAh is important. More mAh is more time but more cells which means more cost more size.

Also are batteries of any sort, genuine or fake easily available for the t400? This laptop is coming onto 12yrs old or more?

I think however T61 and 400 batteries are the same, widescreen ones at least.

[KG789]

OK, thanks. I appreciate the input. I had heard that it was the volts that mattered but wasn't sure. You said the maH. OK. I was wondering about the cells. I've seen 4, 6 and 9 listed. I figured more cells, more $. Does it also mean it's more powerful, as in faster?

As amazing as it seems, there are quite a few batteries out there listed for the T400 - some are listed as T61, some have other descriptors. Yup, it's an old laptop but still running strong so I figured if I could replace the battery, then why not keep on using it.