Victron Integration - feedback

Hardware diyBMS
1

Hi All,

I’ve got a Victron multiplus 2 connected to a Rpi running Venus OS with a PiCan3 hat. Everything is communicating via canbus fine and dandy to the diybms controller.

I’ve found an issue with the DVCC and wondering if anyone else has had the same issue.

My CVL is 28V (7S @ 4V per cell). My DCL and CCL are both set to 20A.

With everything nicely balanced it’s charging and nicely tapers off the current and switches from CC to CV at end of charge. But I have noticed the the CCL does not drop to 0A to tell the multiplus its at end of charge?

In theory it should never go above 28V as the multiplus should always charge to 28V and stop. However we all know lithium iron batteries do or can go out of balance over time and the passive balancing should keep everything in balance. But sometimes they can go very out of balance and passive balancing isnt enough.

I did some experiments over the weekend.

First test. When my pack was fully charged (28V) I set the CVL to 27V. The multiplus started to discharge which was great but the CCL was still at 20A. This should drop to 0A.

Second test I did with the pack fully charged at 28V was set one of the cell monitors to think it was at 4.1V and others at 3.8V as a pack voltage of 26.9V. To simulate a poorly balanced battery. The BMS allowed the multiplus to charge because it was below 28V. NOT GOOD. Again the CCL should have dropped to 0A. It should work with both pack voltage and cell voltage.

The only other level of protection above this is my shunt trip.

I have another ESS with a MP2 but the BMS is a batrium.

The way this works is both pack and cell voltage. It means you have 3 levels of protection which I really like for both upper and lower limits.

High Limit (fully charged) - BmS and Charger control - normal operation - safe limits
High High Limit ( Overcharged) - BMS control- Abnormal operation- CCL 0A
High High Limits (Dangerous) - BMS control- Unknown condition/WTF is going on - operate shunt trip immediately!

At the moment I have 2 levels normal and Dangerous. And balancing if you class that a form of control?

Be great if the software/code could be amended to reduce CCL to 0A in an overcharged state. This is obviously needs to be done over CANbus.

Let me know your thoughts.

Cheers

Gareth

1 Like
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Hello @gjones84

Thanks for the valuable feedback. The Victron integration of diybms was/is fairly rudimentary and in more of a beta test phase waiting for great feedback like you have given.

Ultimately, I (we!) can write code to communicate with the Victron and tell it exactly what to do and in what state to respond to.

What I could do with getting is a crowd of people who are using Victron (I don’t have a set up so have to rely on others) together to design and vote for the way it should work.

Do you have any suggestions on how to discuss this? GITHUB issue for example?

Additionally, the Victron documentation on BMS CAN BUS protocol, recommends changing the voltage to control the chargers rather than the current!

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Heres the relevant text from the Victron specification.

image
image723×919 74.6 KB

3 Likes
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Hi Stuart,

Thanks for your reply.

I really appreciate all the hard word that you have put into developing the diybms. The new v4 controller and cell monitors are great, low cost and provide a high amount of functionality.

I did not stumble across that peice of information regarding the CCL =0 will not work on victron systems. Although find that very interesting as my Batrium does control the CCL in an overcharged state.

I would like to be involved in the development of the diybms victron integration. I will raise an issue for debate on github.

I have been running your diybms on my Victron Multiplus 2 now for a couple of months and works great.

I think for me I would like to see a minor change in the software that stops charging if one of the cells are getting to high instead of operating my shunt trip.

I know some people are not a fan of active balancers but I am. It would be a great feature if you could Implement another rule under the settings that can switch one of the relays when one of the cell monitors reaches a certain threshold. On my system I charge to 4v/cell. Be great to be able to switch my active balancer on when above 3.95V. Do you think this could also be added easily?

Cheers

Gareth

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Hi, there are already rules available on a per-cell basis, are these no good to drive the relays?

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Yes just be great to have one more rule on the list :slight_smile: . Atm I’m using.

R1: Individual cell under and over voltage and Pack overvoltage connected to a shunt trip.
R2: Fan
R3: Spare
R4: Spare

I really like active balancers. I know theyre abit like marmite. You either love or hate them. Theyre are becoming more and more popular and agree they shouldn’t be switch on all the time as they can hide issues if you have defects in your cells. However for ultimate top balancing I want to be able to switch my active balancer on when the maxcell volt of 3.9 or 3.95 Volts for top balance/ equalisation. Then switch of when below 3.9.

So do you think an an extra rule for “individual per cell mid switch point” could be added?

I think alot of other people would use that feature.

I could assign that the R3.

Cheers

Gareth

7

Hello,
I have an issue with the CAN-Bus interface to a Cerbo GX.
I get “Can Errors” as soon as i switch on the Victron Can interface in the controllers menu.
Here is a picture of the controller:

IMG_20220507_081939
IMG_20220507_0819391920×1080 231 KB

The only things soldered by hand is the D8, JP1 and the two condesators C7/8

History, on another controller (Same Software, Cell Boards, Cerbo) it worked now for 1 month flawlessly!

What i have tried:

  • I tried the Controller which worked 1 month, did not work either
  • tried the following constellations:
    • new cable
    • with/without 120ohm resistor on Cerbo side
    • both ways of connecting the can wire
    • different firmwares on the Cerbo

It seems like the Cerbo tries to communicate, as the TX counter increases. The Controller counter stops at 6, the in starts to count fault.

@stuart, any suggestion for further investigations?

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You could SSH into the cerbo using putty and use the candump Can0 command and see if you have data coming through.

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Measurements:
GND - CANL ~2.5V
GND - CANH ~2.5V
CANL - CANH 0V

60Ohm resistance between CANH/CANL

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Can0 = “Network is down”
Can1 = traffic with or without diybms connected. Seems like to be the cerbos tx signal.
I have no other bus devices connected. For the test, i have disconnected the multiplus.

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Maybe your canbus is down. Try bringing it back up.

ip link set can0 up type can bitrate 500000

then try

candump can0

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Going to try that. But is the can0 the BMS-Can and can1 the VE-Can port?

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Im running mine on a Rpi and I use can0. Give it ago and see if that fixes it :slight_smile:

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No, does not work.
No the candump does not return anything.
Guess my can1 it the BMS-Can port.

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Sounds like you might have a duff canbus chip. Providing all the connections are sound!

image

Check you have voltage voltage between Vio and GND.

Are the solder connections sound? Have you got contenuity between the terminals the pins?

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Going to try that.
For info: these chips have been soldered by JLC and i have tried three boards!

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How many did you order? do all the boards from JLC not play ball?

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Two batches.

  1. batch self soldered, old design: did not work on the test bench
  2. batch jlc soldered, newest design: did work on the test bench

I got 3 soldered of the 2. batch, where on was working on the bench seamlessly. But no in the motorhome not anymore, aswell as the other two…

Does not make any sence

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I got 3.3V

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Can you post a picture of the writing on the Canbus chip? These are very scarce at the moment. I wonder if you have the correct chip on your board … maybe?