280A 24V - 3x 340W solar - victron 3KVA inverter/charger complete design check

[alvise]

Hello and thanks in advance for your advance.
Building a overlader on a unicel cube van on Chev 1 ton
The objective is to be able to run some power tools for this reason the choice of that size of charger inverter.
Also, no propane on board and cooking is using an induction cooktop, gasoline stove and heating with gasoline (similar to webasto diesel heater).
Also, focus on operating in low temperature, and need to explore more control and automatization to keep the battery pack over freezing temp
I like Blu boxes but if any alternative with quality components I consider it. (plan to be in remote areas so readability is prime)
Here my project:


questions:
A - how to control the charger side of the inverter when the temp is below freezing and you wan to use the inverter, with my current schematic the idea is the BMS low temperature will shut down the inverter via start relay port so is ok for not damaging in charging but you can not use the inverter
B - does make sense to have a pre-main fuse if you use a distribution center with separate fuses if the distance between batteries and the distribution center is minimal?
C - I plan to use a thermal circuit breaker to isolate the MPPT , i have already a fuse before I was thinking to use it so i can disconnect the MPP without the need of taking off a fuse does make any sense or there is no really need to disconnect the MPPT so often.
D -
E - I left out the possibility to charge the battery bank with the alternator because the cost I was calculating is to elevated to do a proper job (24 to 12 converter, thermal circuit breaker, low temp disconnect extra long wiring ) 600+ $ for extra 300W anyone agree?
F- does make sense to have a BIG disconnector just after the battery so when you park for a while you do not have any phantom loads ? or because you have your solar panel on the roof is better to leave always all connected
G- make any sense to have fuses before your 24V fusebox and before the 24-12 Orion converter?
H- to communicate with the Victron inverter you can go with a dongle and Bluetooth (but you can not change settings) or with the MK3 to USB adapter (but you need a pc to see and control the parameters) if you do not want have both what is your advice on that?
I - looks like lots of the controls from BMS to low temp to heating your battery to data log, to monitoring performance etc could be done with Arduino or Rasbery PI for cheaper, anyone has played with that?
J - I put a switch to isolate the 12 and 24 V loads, i am not sure if the same thing (without phantom loads or possible failure could be done by working on the low voltage disconnector Victron BatteryProtect 12/24V-100A.

I understand that every time you put a switch, a connection a fuse you introduce small resistance because of the nature of your connection and on low voltage that could add up, so try to prune everything is not really needed.

Lots of questions, if you have a question for me I will be happy to explain my choices if you have any advice I will be happy to listen
Thanks in advance, and thank you for our host, such a smart guy!

 

[HaldorEE]

The text in your drawing is hard to read. You might want to attach the image as a file so we can zoom in with clearer text.

I never saw a Victron Battery Protect being used as a Solid State Relay. Interesting way to solve the problem. High current DC output SSRs are expensive.

Your Overkill BMS is not actually in the battery circuit? Thinking out loud now, you have two situations the BMS is there to protect against:

• Cutting off charging for cell over voltage, freezing cell temperature or over charging current.
• Cutting off discharging for cell under voltage or over discharge current.

I understand how you do this for the solar charger, but how do manage these two different functions with a single relay input to the Multiplus? It is both a load and a charger.

• If the BMS cuts off discharge for low cell voltage, is the Multiplus allowed to recharge the battery?
• If the BMS cuts off charging for high cell voltage, is the Multiplus allowed to discharge the battery?

Or is the relay input to the Multiplus only stopping on one of these two conditions? That is not good, you need to protect against both conditions.

 

[HaldorEE]

Actually if the BMS cuts off for low cell voltage discharge, both the Multiplus AND the Solar charger are prevented from recharging.

 

[alvise]

Actually if the BMS cuts off for low cell voltage discharge, both the Multiplus AND the Solar charger are prevented from recharging.

you are right, need to come up with something else ..... maybe i can use some of the relay function of the multiplus to do something... any suggestions ?

 

[alvise]

more readable attach... ( i put a pdf... when you attach a jpeg the system looks like resize the image? )

 

[HRTKD]

A - how to control the charger side of the inverter when the temp is below freezing and you wan to use the inverter, with my current schematic the idea is the BMS low temperature will shut down the inverter via start relay port so is ok for not damaging in charging but you can not use the inverter

When the temperature is below ~32° F the LiFePO4 cells should not be charged. However, they can still be discharged. The BMS will disable the charge circuit. The inverter/charger likely has similar smarts and settings such that you can stop sending a charge at X° F. This doesn't have to be the same temperature that the BMS is using.

My Victron 100/50 solar charge controller has low temp settings. I currently have it set to use the same low temperature threshold that the BMS does. I am considering changing the solar charge controller to use a lower threshold so that some power can be dumped into the system, even though the battery's low temperature threshold has been hit and the charge circuit is disabled. I have warming pads on the batteries. The power from the charge controller would provide enough watts to power the warming pads.

 

[HRTKD]

As long as you're using a Victron Multiplus, I don't understand why you aren't using Victron for your other components such as the monitor and the solar charge controller. Victron does a really nice job of making everything work together.

 

[HaldorEE]

The 3000W Multiplus has two inputs, one can be used to stop charging and the second can be used to stop discharging. If you have a separate port BMS then you could use the two outputs to control charging and discharging individually.

https://www.victronenergy.nl/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf

 

[alvise]

As long as you're using a Victron Multiplus, I don't understand why you aren't using Victron for your other components such as the monitor and the solar charge controller. Victron does a really nice job of making everything work together.

I totally agree, just try to save some money, and some of the functionality are nice but not totally necessary. Dumping energy production from solar to a heating pad when temperature does not allow for battery charging is a great idea, I guess you have a switch to prevent excess production heat battery in summer :D

 

[HRTKD]

I totally agree, just try to save some money, and some of the functionality are nice but not totally necessary. Dumping energy production from solar to a heating pad when temperature does not allow for battery charging is a great idea, I guess you have a switch to prevent excess production heat battery in summer :D

I turn off the battery warmer system in the summer. I'll switch to cooling fans in the summer.

 

[alvise]

The 3000W Multiplus has two inputs, one can be used to stop charging and the second can be used to stop discharging. If you have a separate port BMS then you could use the two outputs to control charging and discharging individually.

https://www.victronenergy.nl/upload/documents/Manual-Connecting-other-lithium-battery-systems-to-Multis-and-Quattros-EN.pdf

Thank you for the information, that sound great, maybe I have to look around for a 24V 8s BMS with that specs (open to suggestions) Otherwise what about using a temperature relay control like this

Inkbird Temperature Controller ITC-1000F 12V Digital Thermostat Heating Cooling Dual Relays Sensor​

to control the "charger disconnect" and use the BMS for the "load disconnect" ?

 

[HaldorEE]

Thank you for the information, that sound great, maybe I have to look around for a 24V 8s BMS with that specs (open to suggestions) Otherwise what about using a temperature relay control like this

Inkbird Temperature Controller ITC-1000F 12V Digital Thermostat Heating Cooling Dual Relays Sensor​

to control the "charger disconnect" and use the BMS for the "load disconnect" ?

The BMS needs to be able to stop both charge and discharge. It is the only thing looking at individual cell voltages.

 

[HRTKD]

Thank you for the information, that sound great, maybe I have to look around for a 24V 8s BMS with that specs (open to suggestions) Otherwise what about using a temperature relay control like this

Inkbird Temperature Controller ITC-1000F 12V Digital Thermostat Heating Cooling Dual Relays Sensor​

to control the "charger disconnect" and use the BMS for the "load disconnect" ?

I think you're making it more complicated than it needs to be. The Multiplus will have the ability to stop charging on low temperature as well as stop charging when the voltage reaches the threshold appropriate for the battery chemistry. The BMS is the last line of defense.

The Overkill Solar 24v 8s BMS has a good set of features. I use the 4s 12v version.

 

[HaldorEE]

I am using a 250A Heltec 8S BMS in my battery pack. It has freezing charge protection and is directly controlling current in or out of the battery.

I am using Victron BMV-712 to monitor and control charging. The BMS-712 has a temperature sensor to protect against charging when freezing.

I am using the relay output of the BMV-712 to control charging from the Multiplus and the Orion alternator charger. The smart solar controller is controlled wirelessly by the BMV-712 (Bluetooth).

The loads are managed using low voltage disconnects. The Multiplus has its own and I have stand alone battery protects. One feeding 24V loads and a second feeding the 24V to 12V converter.

 

[HaldorEE]

The point of my wall of words is that the BMS should never kick in unless the cells get unbalanced. It is also a fail-safe backup to the BMV-712 and the 3 low voltage disconnects.

My plan is to never discharge below 10% SOC. I haven't decided on the max charge level. I need to better understand how cell balancing works to make that decision. I am using the 280AH cells everyone else is and I understand these are not matched.

 

[Rocketman]

I know these ideas cost more - but they bring a lot of options.
Add a Victron monitor CCGX- also add the Victron Mppt’s charge controllers,
Look at the Batrium Bms and then connect it to the CCGX over Can- Bus. (You then eliminate the Battery protect as a cold cutoff and shunt( included in Batrium))

this will enable the bms to completely control the charging and discharging plus give you a great monitor to see exactly what the status of your system.

 

[alvise]

I am using a 250A Heltec 8S BMS in my battery pack. It has freezing charge protection and is directly controlling current in or out of the battery.

what size of the inverter/charger are you using?
the price on the Heltec is suspiciously low .... can you change any setting on that unit? what model, in particular, you are using?

I am using Victron BMV-712 to monitor and control charging. The BMS-712 has a temperature sensor to protect against charging when freezing.

You sad that the 250A Heltec 8S BMS has freezing charge protection so not real need to BMV protecting for freezing charge (you wrote BMS-712 but i guess you meant BMV-712)

I am using the relay output of the BMV-712 to control charging from the Multiplus and the Orion alternator charger. The smart solar controller is controlled wirelessly by the BMV-712 (Bluetooth).

If you use the BMS to cut out the connection to the battery to the multiplus without using the relay port could be a problem?
Looks like a Victron shunt + BMV-712 monitor is a really nice integration but because I have already a shunt to monitor battery status I was wondering if I can get away without it.

The loads are managed using low voltage disconnects. The Multiplus has its own and I have stand alone battery protects. One feeding 24V loads and a second feeding the 24V to 12V converter.

thnaks

 

[alvise]

The point of my wall of words is that the BMS should never kick in unless the cells get unbalanced. It is also a fail-safe backup to the BMV-712 and the 3 low voltage disconnects.

My plan is to never discharge below 10% SOC. I haven't decided on the max charge level. I need to better understand how cell balancing works to make that decision. I am using the 280AH cells everyone else is and I understand these are not matched.

maybe i just ship back my shunt and get the victron 712

 

[Rocketman]

One other item to consider- the main fuse for your pack 400a ANL FUSE. My understanding is Class T fuses are better in the worst case scenario when a cable is shorting. They have a much higher cutout amperage.

 

[alvise]

....

I am using Victron BMV-712 to monitor and control charging. The BMS-712 has a temperature sensor to protect against charging when freezing.

....

Instead of the BMV-712 can you use the Victron SmartShunt 500A? it has a temperature sensor and Bluetooth , not sure if he can talk with the multiplus ...​

 

[Rocketman]

I believe the Victron SmartShunt has the same communication ports as the BMV-712. Except maybe no relay(?).

In my rig, I run everything through a CCGX. The Bmv-712 and Smart Solar 100/50 Mppt connect with the VE-direct ports/cables. The Multiplus12/3000 uses VE-bus. And shortly (springtime) I will connect the Batrium BMS to the CAN-bus.

The BMV-712 and Smart Mppt’s can communicate via Bluetooth (the 712 passes temp and voltage to the mppt). I think the Bluetooth module for the multiplus allows the same (if not there is a temp sensor for the multiplus)

I have not worried about low temp charging because currently I have AGM’s.
After I install the LiFePo4 ‘s and Batrium BMS, the Batrium will use ESS and tell the CCGX if it want full charge, limited charge or no charging and if the Multiplus has full discharge or no discharge. The CCGX passes that info to all the other devices it communicates with.

 

[Pnw_steve]

Your wiring diagrams are beautiful

What app did you use?

Thanks.

 

[HaldorEE]

Instead of the BMV-712 can you use the Victron SmartShunt 500A? it has a temperature sensor and Bluetooth , not sure if he can talk with the multiplus ...​

I have no idea. Probably, but I wanted a display so I never considered the SmartShunt.

 

[HaldorEE]

I believe the Victron SmartShunt has the same communication ports as the BMV-712. Except maybe no relay(?).

In my rig, I run everything through a CCGX. The Bmv-712 and Smart Solar 100/50 Mppt connect with the VE-direct ports/cables. The Multiplus12/3000 uses VE-bus. And shortly (springtime) I will connect the Batrium BMS to the CAN-bus.

The BMV-712 and Smart Mppt’s can communicate via Bluetooth (the 712 passes temp and voltage to the mppt). I think the Bluetooth module for the multiplus allows the same (if not there is a temp sensor for the multiplus)

I have not worried about low temp charging because currently I have AGM’s.
After I install the LiFePo4 ‘s and Batrium BMS, the Batrium will use ESS and tell the CCGX if it want full charge, limited charge or no charging and if the Multiplus has full discharge or no discharge. The CCGX passes that info to all the other devices it communicates with.

The relay is important to me. That is how I control the Orion-TR Smart Charger (alternator) from my BMV-712.

 

[Rocketman]

I just checked and I remember correctly- the smart shunt does not have a relay - for a relay you will need a BMV-712(or others in that lineup)