I have a boat that I am preparing to install DIY LFP batteries. I have 4 SmartSolar charges (2 75/15 and 2 100/50) and a Multiplus. On the Multi, I have the Bluetooth dongle (which is very good at linking battery info to the MPPTs) and I also have the USB dongle (but can’t use both at the same time…). I’ll be using a BMS that does not speak CAN but provides “dry contacts” that can be used to short an input, or provide power/ground.
I am intending to have the BMS force-disable all charge sources when needed. The easy way is to use the input contacts on the Multi, and a Non Inverting VE.Direct cable on the MPPTs. Unfortunately, this will prevent any future upgrade to a Cerbo if I want to, as the port can be used as charge disable or as VE.Direct, but not both.
A Cerbo is not on the plan right now, but I could possibly be convinced. Is there any way to link the MPPT and Multi into the Cerbo, and then have my BMS tell the Cerbo to initiate a “Cease charging” command? It would have to be a simple signal, similar to what is used on the Multi. It would be awesome if the charge-disable signal on the Multi would share that across the system via the Bluetooth Dongle.
A solution that doesn’t appeal to me would be to insert a 220A Battery Protect in the solar feed, and have the BMS trip that. I’m not sure I like controlling the solar by opening and closing the output --that defeats the graceful shutdown the MPPT includes
With a cerbo you can use a digital input and a node red flow to disable and enable charging.
The inverter connects to ve bus port.
The mppts to the ve direct ports and the usb ports.
All information on one screen.
You can still use the ve bus to Bluetooth dongle at the same time as the cerbo as well.
Ypu shouldn’t need to the force charge and discharge with all the correct voltages programmed in though?
If current control is what you need then also the cerbo can do that with DVCC
Thanks. That’s very good info.
I intend to have all charge sources except the MPPT set below any BMS threshold, so they should simply die off all on their own. I’m not sure about the MPPT. My thought is that if I set them too low, I may not get to fully 100%, and get the balancing to kick in. Ideally, I’ll still be able to have the MPPT shut down on their own, and the BMS will never trigger an override. I just don’t have any first hand experience in how the LFP charge (volt/current/time) profile plays out. If I can get the MPPT to die off before the BMS says “enough,” the Battery Protect would be a pretty decent solution, as it should never trigger anyway.
However, being able to send a digital input the the Cerbo, and have the Cerbo disable/enable charging, that would allow me to avoid the Battery Protect entirely (although it would then require me to buy a Cerbo… decisions, decisions…
The one concern is the reverse logic of the VE.Direct charge disable. If the wire gets loose, or whatever, the signal is lost and charge continues uninterrupted.