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Old 04-14-2011, 09:28 PM
Howard Matos
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how exactly does the balancing in the FMA Cellpro PowerLab 8 charger work?
I want to use the FMA Cellpro PowerLab 8 for cycling tests of 8S1P chain to test 8 cells at the same time.

It is important for me to have each individual cell charged fully to 3.6V and less then C/20 current acceptance so the SoC is 100% and then also each individual cell to be discharged to exactly 2.8V.

You will require the Charge Control Software to adjust the balanced A123 preset you require, make sure per cell voltage is 3.6V (Charge tab), termination is C/20 is default, found in (Termination tab). Start with an accurate preset for the most precise balancing. Discharge voltage can be found on the discharge tab.

During charging: suppose one cell in the chain reaches full charge and doesn't accept any more charge, will the charger continue to feed current to the remaining cells in the chain through the balance leads? Yes, that't the way balance charging works.

And during discharge: suppose one cell in the chain reaches 2.8V and I don't want it to be discharged more? Will the charger stop sucking current out of the main leads, and discharge the remaining cells through the balance leads only (of course at max 3A) until every of them reaches 2.8V? This is not the default method that PL8 discharges, nor is it recommended. PL8 does not do balanced discharge by default. First, it does not give you an indication of the actual capacity of the pack. Actual capacity is based on the weakest cell in the pack. When you balance discharge, you are allowing the strongest cell in the pack to give you the measure of capacity. If you discharged this way in the real world, you'd end up with damaged cells in the pack if you did not balance discharge during operation. Nobody manages a battery this way during application. The better way to discharge is to monitor all cells in the pack, and, when the first cell reaches termination voltage, stop the discharge. This provides you a real indication of capacity, based on weakest cell in the pack. The balanced discharge method actually un-balances the battery during discharge, and then the PL8 will have to re-double the efforts to re-balance it during the charge cycle. Nevertheless, a new version of the CCS/firmware will be available shortly that provides balanced discharge option because other customers have requested it.
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