I have set Float 27.6 and Boost 28.6 voltages, and a 4 hour Equalize with dip-switches & potentiometers as specified in the manual. However when charging my LiPo4 batteries- the charger does not follow the charge cycle stated in the manual ie: It should should start charging (from 26v range) in Boost up to 28.6v, Equalize for a time, and then float down to 27.6v. But instead it starts charging in the Float up to 27.6 volts instead. When it reaches 27.6v the charge current decreases without the batteries ever getting fully charged as they should with in the Boost, Equalise, Float cycle. To fully charge them I have to permanently enable the Boost charge with the 1st dip-switch, and then switch off the charging manually. Why is this? Why in normal operation does my charger never start charging in the Boost phase? How do I fix it?
The Skylla “Equalise” function is for lead Acid, not for lithium. The equalisation phase normally occurs after Absorption, once the tail current has dropped to a low value - 100% charge.
For lithium, the best option is to set the float voltage at 0.1V to 0.2V less than the Abs voltage, then the cells will fully charge and equalise. However, you do need to be careful doing this, as there is no feedback from the battery to the charger to limit the current as one cell gets to max voltage first. This may cause the battery BMS to disconnect periodically as the calls balance.
I fixed the problem, noticed at the end of the manual a section about “intelligent startup”. Enabled by default- it checks the battery voltage on startup and if it is “sufficiently high” it starts charging in float mode. Sufficiently high on my LiPo4 batteries appears to include the 25.5 to 26v range they sit at when semi discharged and I start charging. I have now disabled this “feature” with a dip-switch and it now it starts charging in Boost (like my EPEVER solar controller).
I may have confused Equalisation with Absorption. There is no “Absorption” phase on the Skylla or EPEVER. Instead a so called Equalize phase which holds the voltage constant to the peak of the Boost for a set about of time, while the charge current decreases, before dropping it into Float. I have watched it do this many times when charging from my solar via the EPEVER.
After disabling the “intelligent start”- yesterday was the first time I saw it happen when charging with my generator via the Skylla. I also have a JK BMS battery balancer- which kicks in at 28v- to balance my cells at the top of the charge.
The Equalise (Absorb) time on the EPEVER is set to 40 minutes (before dropping to float)- during which the charge current drops off, and the BMS balancer does its thing. However the minimum Equalise time set-able on the Skylla is 4 hours- so I just watch the charge current decrease over the half hour or so, and then shut down the generator. But at least its getting up 28.6v and holding there now.
Currently the region of Tasman, New Zealand is under a State of Emergency with Heavy Rain, and only a week of mostly cloudy weather since the last deluge which brought 600mm, and the previous State of Emergency. Areas have been flooded, livelyhoods destroyed, but no-one killed (yet). Keeping my off grid solar power system alive via the Skylla & generator over the last 3 weeks has been a godsend, and nice to finally have working properly.