Thread: Doable or dumb?
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Old 21st Jan 2019, 12:21 am   #3
Herald1360's Avatar
Join Date: Feb 2007
Location: Leominster, Herefordshire, UK.
Posts: 14,755
Default Re: Doable or dumb?

I don't understand how a shunt regulator to limit battery voltage to 13.8V can cause the battery it's across to be undercharging. Surely if the Varta isn't reaching 13.8V at full capacity it would be overcharging. Could it simply be that the Varta battery has more actual capacity than tired Powerline ones so it's just taking longer to charge?

It also seems very odd that it won't reach that voltage- for a one shot charge you would normally run constant current at about 14.4V limit until the charge current falls to around 10% of its initial value after the battery hits 14.4V then drop back to 13.8V to float the battery. No problem with exceeding 13.8V on the way up.

What does the Varta battery datasheet have to say about recommended charge routines?
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