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I'm trying to connect 2 batteries from 2 different suppliers
Can I connect these 2 batteries (through their individual BMSes) at the same time to the Venus GX?
How does the Venus GX manage 2 BMS inputs?
Hi, sorry, but it doesnt manage it: the code is written to expect one battery - not multiple.
it wouldnt know which inverters or mppts to control based on which of the two bms-eses parameters.
our philosophy here is been that this is too much of an edge case to make code for; and one options is to take two GX devices.
Hm I should nuance that a bit probably: it can monitor multiple batteries; ie log it to vrm and show on screen.
But it can use only one for controlling the inverters, chargers, and so forth.
from all available BMS-es, it will use the one with the lowest device instance
Ps2: I’ve updated my above comment a bit; and thought of something else: you can’t have both those BMS-es on a single can us port. The BMS-Can protocol doesnt use addressing: the Cerbo won’t be able to distinguish one from the other.
so to do this, wire each to a a different port. Configure the VE.Can port to the right profile as well (I suppose BMS-Can 500 kbps).
And then see what happens. Do both show up individually in vrm and do they have a different device instance number there?
and in the device list on the UI?
It might work, or might not work. It needs testing to find out.
If it works, its “by accident”: we dont design for this.
Ps3: Another update: it wont work, not even when connected to different canbus ports on the cerbo. Sorry.
You could use a BMV to monitor the second bank.
@mvader (Victron Energy) A few follow ups:
Hi Btank, sorry, myself and from Victron side we can't help any further than what I said above.
Also I didn't understand earlier that you wanted to sync multiple GX devices: you can do that a little bit with all sorts of limitations and only in v2.60 and later; but then only for readout on a "slave" unit. Not for making one comprehensive system.
Having three 10kVA Inverters in 3 phase needs by design and definition one battery bank, see here: https://www.victronenergy.com/live/ve.bus:manual_parallel_and_three_phase_systems. there is no way around that.
I hope someone else can help you; if not then sorry - too far away from normal & supported use cases.
@ea7777777 you're confusing two different things here:
- multiple similar, daisy-chained BMSs that appear as one single battery in CAN-port
- multiple different BMSs that cannot be daisy-chained and hence cannot appear as one single battery
You are right Juha Tuomala
, the question is about two different battery banks on the same dc busbars.
And like @mvader (Victron Energy) mentioned, it's tightly coupled to the controlled charging. And it can be done, but then only one battery is monitored during the charging regardless what happens in others?
In this particular case, it wont be possible as @ea7777777 mentioned "people want 16s" and Pylontech is imo 15s, so those two cannot be hooked into same busbar. This is exactly the reason why I don't plan to buy more pylontech but switch over to some other competitively priced daisychainable-canbus-lifepo-bms. @RotEvery
As with other posts, batteries with built in bms are now common - I have a pair of Fogstar Drift Pro’s.
So why is it that I need to use both can bus ports and a battery aggregator patch developed by a hobbyist?
In 2020 it may well have been edge case to have multiple bms, but in 2024 it is not.
If I understand you well, no one is suggesting you connect your batteries via different CAN buses if you have one type of battery or fully compatible types. The OP asked how to connect different BMS' of different types. If it's one type of BMS, you only connect one CAN bus to Victron and interconnect all the other battery modules and therefore their BMS' typically with a patch cable as directed by your battery manufacturer. It's all in the manuals.
F.
Hello all,
My 2 cents...
If I would want to have grouped in a single bank two or more different batteries with the same or different BMS types, then I will do the following.
1. Make sure the batteries have the same chemistry and the same voltage or number of elements. eg: 15s or 16s. Ideally the same current rating or close.
2. Set inside chargers/inverters the proper voltage limit for that battery type (15s or 16s)
3. Set inside chargers/inverters a current limit that is about C/2 of the smallest battery capacity. In this way you wont "torture" any of the batteries when charging.
4. Let the BMS'es do their job without connecting any of the batteries' BMS to the BMS CAN port of the Venus
5. If I really want to monitor the state of the batteries, use a current shunt for each battery. They will appear separately on VRM and Venus.
That's all...
LE.
OP has thrown the question and then left. Last visit was 4 years ago....
Thanks for the reply - I will think about your suggestion.
These (identical) Fogstar batteries are being used in a Motorhome (I needed two due to space constraints - they fit under the driver and passenger seats).
Having been in touch with Fogstar (who explicitly state the batteries can be connected to the Cerbo CAN bus on their website), they confirm as above that you have to connect one to each CAN bus, which as a software developer myself feels like a hack at best.
Given that 'gas free' motorhomes are being actively promoted by mainstream manufacturers now (rather than just hobbyists bolting parts into DIY campervans), it feels reasonable to return to thie original question of why, given CAN busses are intended to have multiple nodes, can we not connect two BMS modules for identical (or indeed different) batteries directly to the BMS specific CAN bus on the Cerbo and have them aggregated.
For myself, I was asking because I wish to connect the other CAN bus to an NMEA2000 network, which will be a challenge if there is a BMS operating at a different speed already hooked up to it.
The question should really be posed the other way for your Fogstar situation. Why are the battery manufacturers not designing their BMS systems properly to daisy chain their batteries together and report the aggregated values to the external equipment. This is a failing on the battery manufacturers part, just trying to make down to a cost. Look at the Pylontevh RV batteries, RT12100G31, put several in parallel and connect the data cables together and link one to the Cerbo, with this battery acting as a master reporting the whole bank. This is the battery manufacturer doing it right.
The Fogstar Drift Pro use a JBD BMS, which I've not seen anyone really using for their CAN communications in parallel, whereas Fogstar also sells their server rack batteries and Seplos Mason kits which use the Seplos BMS's which can be linked on the same CANbus, or even better, buy the JK PB series BMS for use on the same CANbus. It's not Victron's fault the JBD don't work on the same CANbus.
I also use SerialBattery and an aggregator for my UART JK BMS's which works well on a Cerbo, but is at the limits of its processing power.
Your answer is (correct and) very relevant to the original question which is about two different battery banks (and therefore two different BMS) on the same dc busbars being connected to the GX device.
I think GX devices design should be improved such that they can handle this scenario, automating the solution you've described and showing the SoC of each battery bank in GX Touch and VRM. They should be able to intelligently handle the concerns raised by @mvader (Victron Energy) in his first answer (deciding which parameters to use, et cetera). They should be able to integrate and aggregate all connected devices intelligently.
Hi @RotEvery & co,
Ok I’ll bite now ;o)
We’re leaving this up to the battery and BMS makers.
There is nothing that makes it impossible for BMSes to inbetween them exchange data and form an aggregrated overview towards the GX, including DVCC parameters.
And there are various battery makers already doing that; such as MG Electronics, or various of the 19” battery makers.
And since a short while also our own Lynx Smart BMSes can be used together as one.
During that project it became very clear that, for an optimal solution, the aggregratoon needs be done by the BMS, not by the GX. A generic solution, which is what we could develop, will never be as good as what a BMS maker can develop by developing a synchronisation and aggregration mechanism in and between their BMSes.
All the best, Matthijs
Ps. Lynx Smart BMS announcement, will come soon as part of Venus OS v3.40 release:
—
Add parallel redundancy for Lynx Smart BMS and Lynx Smart BMS NG. Multiple Lynx BMSes, each with their own battery bank, can now be installed together to form a single system. This adds (a) redundancy, (b) increases the maximum installable capacity and (c) increases the maximum allowed high charge and discharge currents. Requires Lynx BMS firmware v1.10 or later.
—
;o). Thanks @mvader (Victron Energy) for the info on multiple Lynx BMSes. I think more and more battery/BMS makers will do similar. It's in their interest. I guess third party boxes (not DIY) may also be developed to do the synchronization/aggregation, et cetera. There will still be need for GX devices to be able to accept multiple battery banks info and display the SoCs separately while using only one for the GXes' functions. I guess Venus OS v3.40 already addresses that.
Victron's position on this (what I proposed in my above previous post) is noted. It will be interesting to know the position of other high-end inverter/charger manufacturers as well. Regards.
