Battery "Re-calibration" Routine on Lithium Ion batteries? - Page 1
Forum section: electronics / general

author: Halcyon
author_rank: Unknown
timestamp: July 19, 2016, 01:04:04 am
content: I have a bunch of Panasonic Toughbooks at work. There is a built-in mode which can be invoked before the OS boots to perform a battery "re-calibration". It basically runs the battery through a single charge-discharge cycle before switching off.I thought it was a bit odd since the batteries were Lithium Ion packs (the older models had Nickel-Metal Hydride's). As far as I knew, Li-ion batteries prefer shorter, more frequent charges as opposed to full discharges and long recharge cycles.I know these sort of re-cal cycles were sometimes useful for NiCad and NiMH batteries, but in the case of Li-ion, does anyone know what this particular mode actually does? Is it the case that the power management controller "learns" some characteristic about the particular battery or is it just redundant?

author: ConKbot
author_rank: Super Contributor
timestamp: July 19, 2016, 01:57:48 am
content: Quote from: Halcyon on July 19, 2016, 01:04:04 amYou got it. Some battery 'fuel gauges' integrate the current in and out of the pack. ( 'coulomb counting' ) to keep track of the state of charge. By letting it discharge the battery to the low voltage cut off point and charge continuously, (or vice versa) it can track how many amp hours of charge went into the pack. For an accurate estimation of state of charge coulomb counting beats voltage monitoring. The terminal voltage depends on the state of charge, load current on the battery, temperature, age of the cell, and the manufacturers blend of ingredients (a samsung laptop 18650 will have a different discharge curve then a an LG laptop 18650). So voltage is a rough guess, coulomb counting is a more refined monitor.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: July 19, 2016, 02:22:48 am
content: Hi,Here are a couple of pictures to add to the comments made by ConKbot.The first picture shows how a Coulomb counter can drift, if the State of Charge, is rippling without hitting the end stops, fully-charged and fully-discharged. The calibration routine determines the end stops.The second picture shows how the capacity of a typical Li-ion battery diminishes with the number of charge /discharge cycles. The calibration will adjust for the reduction in capacity.Note:That the Coulomb counter is normally attached to the cells. If the Coulomb counter is not attached to the cells, but in the equipment, it must be calibrated if the cells are changed.I hope that this helps.Regards,Jay_Diddy_B

author: Halcyon
author_rank: Unknown
timestamp: July 19, 2016, 02:30:39 am
content: Right, that makes sense. Thanks guys!

author: djQUAN
author_rank: Frequent Contributor
timestamp: July 19, 2016, 11:13:58 am
content: My Lenovo laptop's coulomb counter is crap heheheI recelled the battery pack with new 3400mAh Panasonics and it still registers as an old pack with limited capacity. The OS recommends resetting the gauge by automatically fully discharging and recharging the cells and results to an even lower capacity estimation.It still chimes that the battery is about to run out but can still run for hours well past the 0% battery level.