3 cell v 4 cell?

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Thinkpad4by3
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3 cell v 4 cell?

#1 Post by Thinkpad4by3 » Fri Aug 04, 2017 7:11 pm

Any particular reason when the switch from IBM to Lenovo, the batteries went from 3s 10.8/11.1V to 4s 14.4V batteries?
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automobus
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Fallacy.

#2 Post by automobus » Fri Aug 04, 2017 8:41 pm

They did not. IBM's ThinkPad Li-Ion batteries had three–serial XOR four–serial cell configuration.

IIUC: Lenovo's ThinkPad's (since 2005/2006 α60 line) feature an "advanced" power system, which enables compound batteries. Compared to the "ThinkPad 2000" (α20–α50) battery connector, ThinkPad "advanced" battery connector has additional two electrical contact positions. In practice, this capability was utilised in only Z60t/Z61t and its 7-cell battery (which contains two strings of series-connected cells, 3s + 4s).

edit: I did not know which ThinkPad had a 7-cell battery, so I wrote only first model which I found in WWW search. Thank you dr_st for correcting me.
Last edited by automobus on Sat Aug 05, 2017 9:18 am, edited 1 time in total.

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Re: Fallacy.

#3 Post by dr_st » Sat Aug 05, 2017 3:58 am

automobus wrote:
Fri Aug 04, 2017 8:41 pm
In practice, this capability was utilised in only Z60t/Z61t and its 7-cell battery (which contains two strings of series-connected cells, 3s + 4s).
Probably in the short-lived T/R61 14" wide 7-cell batteries as well.

How are the 6-cell, 8-cell and 9-cell batteries configured?
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Re: Fallacy.

#4 Post by automobus » Sat Aug 05, 2017 9:58 am

Those (6, 8, 9) are not compound battery configurations. Those battery packs contain a single string of series-connected (3s or 4s) groupings (2p or 3p) of cells. Their battery connects to a circuit board, through protection devices, to both sets of contacts in "advanced" battery connector. Both contact pairs are used: two positive and two negative. (As opposed to one positive, one negative, two not connected.)

I guess Lenovo could choose to create a battery of parallel-connected series of single-in-line cells, but it would add complexity and cost. In such smart, protected, battery packs, its embedded controller is wired to every group of cells, for sensing and for balancing. In common 4- and 8-cell batteries, that is five connections: positive pole, negative pole, and three midway balance/sense connections. In an 8-cell (smart, protected, Li-Ion) battery which consists of two parallel strings (each of four cells), its embedded controller would have eight (possibly nine or ten) internal connections.

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