Hi.
I own an ESS, based on a Multiplus II 3000, cerbo gx, smart mppt 100/20, Makeskyblue MPPT 60A and 4 Powerqueen 25,6V LiFePO4 (2S2P).
The battery was monitored by a SmartShunt 300A, and the current coming from the MSB was also monitored by a SmartShunt 300A.
This setup worked well for a couple of days. Then the contact to both shunts got lost without any obvious reason. A internet-research brought up the possibility, that one of the BMS switched off and the MPPT charger increases the voltage to a voltage which kills the SmarttShunt.
Today I installed a new SmMartshunt 500A as battery monitor (SOC 100%, good sunshine) and after a few minutes of propper working, this shunt died as well. I double checked if anything was not connected correct, so please don´t search the problem on my side.
Beside the money which just burnt down, I need a solution which works without these problems.
Is there a solution which works well without a shunt? Like using the Multiplus as Battery monitor and using only Victron MPPT-charger - or do I still need a SmartShunt as Batterymonitor, because the MPPTs communicate not the right way?
Or is there another compatible Shunt, I can use, which is not so -lets say- sensible for voltage peaks?
Or is there a way to protect a SmartShunt from such Voltage-peaks?
At the moment. I disabled the MMPTs and use only the Multiplus as batterymonitor, but of course I need to include the MPPTs again.
Does your BMS disconnect the + or - side?
Where and how is the shunt connected ⌠Photos or a little drawing by hand
There may have been too much current flowing briefly via the + connection because the BMS has disconnected âŚ
I can´t tell exactly what happened or if the BMS even did disconnected the battery, as the bms is included in the batteries and you can´t get any data aut of it. So I Also can´t tell you, if the BMS breaks + or -
All used cables, except the Cables to the MPPTs are 35mm²
The charging Voltage is set to 57.6V, which is exact what the manual of the batteries tells.
The maximum current is limited by the MMPTs specs and would be 80A at a max.
Today, when the 500A Smartshunt failed, the solar-load was about 1000W, which would be around 20A.
The only âloadâ connected to the system is the Multiplus II, there are no AC- or DC Loads behind the Multiplus II.
The Shunt is connected to the negative side by a ~50cm cable, the âsystemâ-side is connected to the distribution rail. The Batt-cable of the shunt is connected to the positive distribution rail.
The Aux cable is connected to a the cable in the middle of the 2 batteries.
Both MPPTs and the Multiplus II are connected direct to the distribution rail, with fuses on the positive side.
Between the positive pole of the batteries and the positive distribution rail is a main-Powerswitch.
If I only could be sure, what caused the fail of the Shunt, I´d change this part, but as I can´t realy knowâŚ
no, nothing.
The multimeter shows a shortcut (0,0whatever Ohm) between the batt-connector and the minus screws, while the resistance between aux and minus is ~250 Ohm.
The only âlightâ for ~0.5 seconds is the fuse burning down when I change to another fuse.
In other (german) forums, that problem seams not sooo unknown⌠there comes the thought with the voltage peake from.
My usual approach to problems would be trial and error, but it´s a âlittle bitâ expensive to burn down a Smartshunt every try
Could you post some pictures of your setup? If it is environmental it is most likely curent not voltage given you have mpptâs and 48v batteries. Donât see how you could go over 70V. If you have a clamp meter take some readings what throughput there is on the cable.
You dont need a shunt unless you have a DC system and its certainly not important for ESS. I have 3 ESS running without shunts I deleted them about a year ago. The multiplus is excellent at estimating the SOC and far better than the shunt especially when you have a large capacity.
If you think voltage is killing the system have a look at lowering the absorption voltage so you donât get BMS disconnect and also add a battery protect to disconnect when high voltage is seen. There are plenty of examples of people using a battery protect on their installs incase of MPPT failure and high voltage from the solar.
There is a setting where you can use the MPPT current for more accurate SOC. But that non victron MPPT will need a battery protect and a shunt the system will need has DC load enabled.
I already removed the shunts and just installed a temporary bridge by screwing the contacts together. The Makeskyblue is also disconnected at the moment (
So by replacing the Makeskyblue by a e.g. Victron SmartSolar 150/60 and activating (german) âPV-Ladestrom nutzen, um VE.Bus SOC zu verbessernâ I can setup the whole ESS without any Shunt and this works good? I´m asking, because I saw a lot of Setups (youtube) where shunts where used even in a victron-only environment,if the BMS can´t communicate with the cerbo gx.
The shunt is for measuring DC loads. I think with an inverter load the problem is ripple. When I used shunts the SOC was 5-10% out. In the end voltage is king, 40V is empty and 56.5V is full. That works for me. Unless there is a storm coming I run them down 0%.
Just set the multiplus to battery monitor in the settings and plug the MPPT into the cerbo. If you get another victron MPPT plug that in as well and all the charge and discharge will be measured.
Looking at the photos you might also need a battery balancer. I have not seen one that will balance 2 x 24V batteries. That will be interesting.
A quick look, a balancer for 2x24V does not exist unless you make it yourself. The battery might perform better if you parallel the 2 24V banks. I think I have it correct. This will limit one series connection from going to a high voltage. If you can parallel all these first and charge to 28V and let them balance for a few hours first.
The temp-sensor comes belongs to the cerbo gx, and does not get the power through the clamp.
I could also clamp it to any other connection or just hang it in the air.
To use a shunt as batterymonitor is the recommended method by Victron, so this should work this way
As you already mentioned, there is no 2x24V balancer available - as far as I know.
I loaded all of the batteries complete full and paralled them for ~36 hours, before I set the 2s2p
As far as I know, the scema to parallel 2 batteries and then set them in serial so 2P2S instead of 2S2P like I did, would higher the risk of damage, if one Battery fails, as the 2nd Battery, in parallel would have a very high risk to fail as well. So it seems to be highly recommended to monitor the middle-voltage if the batteries are connected in the middle.
2P1S like I hope to have drawn correclty will work better for charging and discharging. You will need to fuse between the parallel connections. The problem with 2S2P, when one battery disables charging the voltage will increase significantly on that one battery and raise the system voltage to the charge voltage.
The idea that the voltage powering the Cerbo GX wasnât the same as the system voltage was a good one. Mike, I think youâre right that you have it correct, but itâs worth verifying.
Itâs a bit off topic, but I looked at your entire system, not just the Cerbo GX.
The crimps on your lugs arenât optimal. Those look like hammer crimps. Get a hydraulic crimper. I suspect that your crimps are creating resistance.
The negative cable from the Victron solar charge controller to the busbar needs help. There are multiple strands that arenât in the terminal. This too creates resistance. I donât think the busbars youâre using are ideal for your system. A six stud 5/16" busbar would work better for the big cables. Itâs overkill, but take a look at the [Blue Sea PowerBar 1000]. (https://www.bluesea.com/products/category/18/111/BusBars/PowerBar_1000). Lots of studs for big lugs and plenty of small screws for the smaller ring terminals.
The fuses youâre using between the solar charge controllers and the positive busbar are commonly associated with audio systems. On the DIYSolarForum.com site weâve seen quite a few failures of those fuses. The fuse holder itself melts. Are you sure that theyâre rated for a 48 volt system?
Replace the two negative wires between the MakeSkyBlue and the busbar. That additional connection is unnecessary and creates resistance. Replace it with a single cable. And donât connect a lug to the backing board. If the backing board gets wet it could create a connection between the positive and negative circuits.
On your positive busbar it looks like the bridge from the bottom stud to the rest of the busbar is on top of the lug. It looks like there might be a curve to the bridge but I have to wonder if the bridge is making a flat connection.
You donât have the Victron solar charge controller grounded. The MakeSkyBlue isnât either. Hard to tell with the inverter.
I have had 2 smart shunt IP65âs failâŚone lasted 10 months and then just died and the other lasted 4 months and just diedâŚThere is no BT LED on after failing. After the fuses have been checked, the + wiring connection checked, I have tried disconnecting the shunts and reconnecting again, but no change. I have 4 banks of 16x304ah Lifepo4 cells (48v each bank) - approx 60kw of batteries in total, with each bank having its own Daly BMS and Daly Active BalancerâŚeach of the 4 banks connects into 2 main Busbars (+ & -), from there the - goes via the smart shunt to a circuit breaker and the + goes straight to another circuit breaker. From the 2 circuit breakers the + & - go straight to a 10.2kw 48v Hybrid Inverter. Nothing else is connected to the smart shunt and all load is connected on the load side of the smart shunt. I have just ordered my 3rd smart shunt, if that one fails I will just do without a shunt as I canât keep wasting money on products that are not resilient. Apart from this repeatedly failing smartshunt issue, my system runs normallyâŚmy Inverter float charges at 54.4v and bulk charges at 57.6vâŚthe typical normal cycle goes between 100% SOC and 50%-60% SOC, it very rarely drops below 35% SOCâŚI would be grateful if anyone knows a way of âreactivatingâ the BT, but if not, this posting is just to let people know that these smartshunts do have problems !!
⌠ok