I use a Hyperion DUO charger and charge 2 5S packs in synch mode which balances the 2 packs as if they were a single 10S pack. 5S packs can only be charged at about 8 amps since the DUOs are limited to 180 watts per side. So I charge at 1C. Usually takes 45 minutes to recharge the 2 5S packs. The DUO will show total pack internal resistance, but not the individual cells. You can monitor the individual cell voltage during charge however.

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