I recently installed Wattcycle 314AH Mini “Smart” Lithiums with Bluetooth. When they reach 14.0v, the BMS shuts off further charging and the Multiplus goes into Absorption. At this point, the BMV-712 is reporting voltage swings of 13.8v to over 15v. I have played with changing the Absorption and float voltages to no avail. The voltage swings do not occur in bulk, just absorption and float. Is there any way to completely disable absorption and float? I tried to lower voltage to zero but it will only allow me to go down to 12v and that doesn’t seem to stop the voltage swings. I also tried to reduce the absorption time and it won’t allow anything less than 1 hour.
My SmartSolar 250/100 controller does not exhibit this behavior. It is an MPPT type charger. Does anyone know whether the Multiplus charger is also MPPT or is it possibly PWM?
I am running firmware version V430. It says I can update it to v556 but IIRC, they told me that if it’s working, don’t update. Does anyone know whether updating to V556 would allow me to disable absorption and float? Since the battery shuts off charging at 14.0v, I see no reason to even bother with absorption and float.
I’m including a screenshot from the BMV-712 showing the voltage swings.
The MultiPlus charger is not MPPT nor a PWM it’s a programmable PFC AC-DC charger. The voltage swings are caused by the BMS cutting out in absorption/float. Best fix: either integrate the battery BMS with GX (DVCC), or set absorption very short and float low so the MultiPlus doesn’t push the pack into cutoff. If you don’t really need AC-charging just disable MultiPlus charging and let your SmartSolar handle it.
If Wattcycle has a CANBus/VE.Direct/RS485 interface that Victron GX can understand → the GX device takes over voltage control. MultiPlus then stops charging before the BMS slams shut, eliminating the overshoot.
If you have a GX device, you can use node red like I have done in here, to throttle the charge current when the voltage rises. I have a bunch of different 12V batteries in parallel and this helps them all balance out without tripping a BMS.
I am having the same exact experience with (4) Litime batteries. Among other anomalies that I have come to associate with the LiTime BMS I have had this problem as well. Voltage during absorption fluctuates continually from 12.8-15.8 volts and never seems to stop even though I have the Multiplus set to a fixed absorption time. Unfortunately it appears to be the fault of cheap, generically designed BMSes used in these cheap “Amazonesque” batteries. I know it is tempting, and many people have seemingly good results but the problems and inconsistencies just aren’t worth it.
My customer has 4 of these batteries installed and the BMSes will not discharge and recharge evenly. No matter what I do at the end of any disharge cycle the batteries are sitting at significanly different states of charge. And, no, they do not balance each other out as they sit. The BMSes usually just put the batteries each into standby until charged or discharged again. This happens perpetually until, in my customers case, some batteries get deeply discharged enough to go into sleep mode and the others supply all the load. All the while the voltage the Smartshunt is measuring is registering as a much higher SOC giving the impression everything is fine. Next step after this is the other two batteries go into sleep mode and the customer’s rig is now out of service. Meanwhile the voltage the Smartshunt is measuring is registering as a much higher SOC.
@AJM1 ‘s info is very enlightening. Unfortunately these cheap batteries don’t have Victron comms. And if they did I would doubt the authenticity and reliability of the firmware anyway. Apparently there was a “leak” of the Victron firmware in China at one point(surprise) and some of these batteries offering Victron comms are using hacked and half baked versions.
