Can I charge a 10.8V, 8.7Ah, 94Wh battery with another laptop that uses 10.8V, 5.2Ah and 57Wh.

[Lenguen]

Long story short, I need to charge the first battery, from a W520, with a T430 laptop.

Can I do it safely or will it burn everything down?

[RealBlackStuff]

You cannot charge a W520/T520/T420 battery in a W530/T530/T430, but v.v. is OK.
See if this helps: http://forum.thinkpads.com/viewtopic.php?f=45&t=118634

[Lenguen]

You cannot charge a W520/T520/T420 battery in a W530/T530/T430, but v.v. is OK.
See if this helps: http://forum.thinkpads.com/viewtopic.php?f=45&t=118634

Oh yes, thanks.

And the other way around? I just tried the battery from the T430 on the W520 and it worked. Can I use it safely?

[RealBlackStuff]

You cannot charge a W520/T520/T420 battery in a W530/T530/T430, but v.v. is OK.

[hhhd1]

Long story short, I need to charge the first battery, from a W520, with a T430 laptop.

Can I do it safely or will it burn everything down?

both batteries are electrically compataible, just in the T430 Lenovo have added a security chip to require new batteries only.

so this will work only if your battery in the w520 is a relatively new replacement battery.

otherwise, ..

try to hot plug it, .. while the t430 is turned-on with it's original battery connected, remove the battery and connect the one you want to charge.