Hi all, I have built two systems. I started out with a hard one (for my level of expertise). A multiplus II 12/5000/220, Cerbo GX, Lynx Shunt and Distributor. A Fogstardrift Pro battery, and a Smartsolar charge controller. AC and DC systems. It has been plugged into the grid permanently at the moment. This has been running smoothly for nearly a year. Battery charge remains at 100%
I then built a second system, actually as a battery backup for a machine at work. Multiplus II 12/3000/220, Cerbo GX-S, Smartshunt, Fogstar Eco battery. No DC system, just AC - since it functions simply as a backup. This is also plugged into the grid permanently.
So my confusion/problem is that for this system, the battery discharges down to about 90%, and then recharges back to 100, every seven days. I think this is because I’ve set to re-charge every seven days. But I can’t figure what I’ve done differently between the two systems where one discharges the battery, and the other keeps it topped up.
Thank you, and sorry for the really dumb question
As ever, without details it is hard to provide definitive answers.
The area I would look at in the Multiplus charger settings is storage charge. If this has been enabled the DC output voltage of the Multiplus is dropped to something quite low like 13.2V even if the battery is holding 13.5V so no charging occurs. Then there is a setting for repeat absorption interval, default setting 7 days so it gives a full recharge at this frequency.
There is another similar setting in the advanced settings called “Wind and Sun Priority” on older firmware and “Prefer Renewable Energy” on newer firmware. This holds the Multiplus to the lower voltage and if the renewable energy has not kept the battery charged it does the full charge on the repeat absorption interval.
Details in the manuals.
Thank you - I will check on these and revert once checked. Kind regards
Thank you for your suggestions. Storage charge was not enabled.
The default Victron float voltage is 13.8, but Fogstardrift recommended a lower voltage - 13.5, to which it was initially set.
I decided to set the float voltage back to its default of 13.8, and the battery now remains charged. Should I edge it back down again to e.g. 13.7 or 13.6 or will it be acceptable to leave at 13.8?
Anything around 13.6V or 13.7V will keep the battery close to full, the newest Victron lithium batteries are 13.7V float. However, I am not knowledgeable on the Fogstar batteries.