question

Hi @Christian Br., thats explained here:

https://www.victronenergy.com/upload/documents/Adaptive_charging_how_it_works.pdf

(ps sorry that no one was able to answer your question sooner!)

If the discharge is quite small, like 5% DOD, the multipluss starts with absorption, and goes relatively quickly to float. That is well done I think, now it can floatcharge for 24 hours, but then after less than 1 hour the storage mode kicks in again, at 98-99% SOC. As we speak the SOC onboard is 99% after a couple of days charging. The other identical twin AGM bank charged with 3 step charger is now 100%. When the multipluss was bought, the plan was to floatcharge for 24 hours, and then let the batteries rest in the storage mode. The plan was not to use storage mode as a charging mode.

What conditions makes storage kick inn after small discharges? Is it only after bulk charging that 24 hours of float will be done? The multipluss lost the shore power for 15 hours this week, and when it started it went straight to storage mode 13,25V/5A. I would have preferred 24 hours of float voltage, but maybe there is something that I have missed in the manual. As the multipluss charges now, the mastervolt 3 step chargemaster charges identical batteries 1-2% more (VRM with 2x BMV712).

I still have the same problem, and today after a weekend in the sailboat, the shore power was connected at approx. 80% SOC. The multipluss charged the 380Ah AGM batteries with 14,25V and approx. 45A absorprion for about 10 minutes, and then switched down to float 13,8V. A little bit to early I think. The multipluss charger is hard to understand. After another hour the storage mode kicks in during 13,8V with 21A charging current. The batteries will not top charge at 13,2V. I do understand that absorption time is calculated from the bulk time, but what happens with the 24 hours of float charge before the storage? What makes the storage kick in when SOC is 88% and current on float is 21A? To fully charge I have to force absorption charge, and that is not the best solution.... (system is on VRM).

The absorption calculation is ok, but how does multipluss calculate the float time? Do I really have to switch off the storage mode to fully charge my batteries?

Am I the only one having this problem? Is the way my multiplus charges the normal way of victron to charge AGM batteries? I am no longer using storage mode, as the multiplus is unable to top charge the batteries with storage mode activated. It has taken med 3 years to not find any answear on this question.

When should storage mode be activated? In my opinion it should never be activated before 24 hours after the multiplus is powered up. Multiplus should be able to fully charge the batteries before the storage mode. This question is still not answered after all these years.

Good day. I think we have to go back and think about the definition of what is 100% full battery. Hence it was noted that the SOC is a calculated value (more like a assumption). The clever guys at Victron must re think this point at what time the battery must be reset to 100% SOC! Think about this. "If a battery pulls no more charge current at the float voltage for an Hour then battery is considdered as full, then system must reset SOC to 100% and switch to Storage mode. Because all of electrons already moved over to the plates. (We can also dive deeper in the chemical reaction if needed.)

Thus there is nothing wrong with the charging of the multiplus, it is just at which point the multiplus must say when the battery is really at 100% and switch over to storage mode. I hope this helps all engineers at Victron and users to better understand and interpret what is really a full 100% SOC battery.

My temporarily solution to the Multiplus charging problem is to use A Mastervolt chargemaster 70A to charge the batteries with. This Mastervolt charger is perfectly topping up the SOC, and the Multiplus is actually more in use as an inverter than A charger for us. Mastervolt has better advanced options for those of us that knows when batteries are ready for the next step / 100% SOC. When my multiplus is going down to 13.2V storage at 80% SOC it just does not work. To see that Mastervolt disagrees with the multiplus and charges 20% more is all I need to see. Our Multiplus is not doing the job. The Victron system have all the information about SOC, current, voltage, etc, but still it switches to Storage A few hours after the boat is connected to shore power, at 80% SOC. My batteries are in very good condition, so that is not the problem. BMV is also calibratet to fit the 100% and 0% SOC during real capasity tests within 1-2% from 100% to empty and back to 100%. The multiplus charges the batteries in correct way with really deep discharges, but if we run the the boats engine until approximately 75% SOC, multiplus goes to storage in less than a couple hours with SOC approx. 80%. At that point the Mastervolt chargemaster normally is started up to take over the charging job. If only the storage could have waited for 24 hours, it should have been possible to charge the batteries. 13,2V storage is not enough. The chargemaster has more adjustments, so you can set both timers and currents when charging should go to the next step. In my opinion float should be the last 2-3% of the charging with a 3 step charger. I really like all of my victron products, but if this problem has no solution, Then multiplus can’t be a smart charger. I need to know if victron says that my multiplus seems to work way they want.

I have the same problem with my multiplus compact 12/1600/230 with a 360Ah AGM battery bank on my boat. After some email correspondence with a victron energy service provider who had to ask victron energy themselves. I got the reply: If the battery bank is already charged it can happen earlier.......

After asking for more detail about why this is happening no more information has been provided to date. And would very much like to understand.

I have used two years on this problem, and the multiplus is no longer in use as the main charger. This is very spesial as the 70A Mastervolt chargemaster now works as the main charger in a complete and advanced 12V / 120A / 760Ah AGM victron multipluss system. The plan was to go from mastervolt to victron because of the 4 step multiplus with the storage mode, but that just didn’t work as we expected.