Why Would Phase 3 of CTEK Charging Go Quickly but Phase 4 Go Slow

Question:

I just got the CTEK US 4.3 and hooked it up to 2010 BMW 528. Stages 1,2 and 3 went by fairly quickly, but its now on stage 4 for 3 hours. According to the manual max times for Stages 3 and 4 are 20 hours and 10 hours respectively. My concern is if max time for Stage 3 is 20 hours and it actually took approx. 1 hour, why would Stage 4 take twice as long still going even though max time is 10 hours? Any advice on this? Thanks

asked by: Latch

Expert Reply:

Stage three is the bulk stage of the charging cycle for the CTEK battery charger part # CTEK56353. If this phase went by quickly it is most likely due to your battery being nearly fully charged as it sat.

Stage 4 is the absorption phase, this is a slow process on purpose so that the battery gets a diminished charge to top the battery off in the best way possible. This phase helps the battery hold the charge that it has by not overcharging. The two phases aren't totally dependent on each other. The fact that your phase 3 went quickly but phase 4 is going slower is perfectly fine.

expert reply by: Jameson C