I have 5 Batteries and all are 16S and connected in parallel but with different capacities:
All batteries have the same BMS each – JK-B2A24S20P which is a non inverter type without any current limiting. Only the ability to disconnect from charging/discharging when a set current value is exeeded.
Each BMS has its own JIKONG BT RS485 Adaptor module.
Each of these Adaptors are connected to an Isolated RS485 to USB Adaptor.
These individual adaptors are connected to the GX device each on its own USB port.
DVCC is ON in GX and the 8 Victron 250/85 MPPTs are all in External Control – therefore listening to the serial battery BMS.
So… it is a simple and clean setup with no risk of unwanted current leaking onto the communication cables.
I would like to get clarification on how the mr-manuel-venusos_dbus-serialbattery driver/software (Link: GitHub - mr-manuel/venus-os_dbus-serialbattery: Battery Monitor driver for serial battery in VenusOS GX systems ) together with the GX device will operate:
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What happens during charging when the battery with the lowest capacity reached 100% before the larger capacity batteries? Will the serial battery driver allow charging to continue or will the system go into float?
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Will balancing be effected by the different capacities?
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In mr-manuel’s notes he recommends the use of Dr-Gigavolt dbus-aggregate software/driver is recommended but do you always need the battery aggravator software when more than one battery is connected? (Link: GitHub - Dr-Gigavolt/dbus-aggregate-batteries: Virtual service to merge multiple serial batteries)
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Other than the calculation of SOC, what is the Dr-Gigavolt dbus-aggregate software/driver actually doing to deal with for example the capacity difference in parallel batteries?
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I had a look at the Dr-Gigavolt dbus-aggregate settings.py file (Link: dbus-aggregate-batteries/settings.py at main · Dr-Gigavolt/dbus-aggregate-batteries · GitHub ) but it is very hard to understand what is going on as the notes are very strange. Nearly as if written by a non english speaking person. Strange word choices like “Key world” everywhere. If there is someone out there who has this already working on a multi battery and multi mppt system, can you please share the settings.py file to that the rest of us can learn from it.
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Is there a way to configure the Cerbo directly via a Script to monitor and adjust charge current based on the current needs when batteries of different capacities are used in this way. It is just not as simple as set the charge current limit, it requires looking at each battery SOC and when needed reduce charge current to match the batteries in need of charge.
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- GX device only uses one battery for data ( all batteries data are visible in vrm if connected), so if battery which is selected gets to set voltage system will go into float if float is set as parameter.
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- Balancing is down to individual battery BMS, or if you mean battery to battery balance then all batteries should be at same voltage dependant of connection.
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- If you want to have an average of all batteries then a combiner / aggregate is required, GX only uses one battery data and aggregate simply combines all individual batteries.
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- Capacity difference is something software can not address without additional hardware, you have to find suitable settings that suit all batteries, basically a middle ground to suit the different capacities, but given there is very little difference, I wouldn’t worry.
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- Agreed some wording is hard to follow, I have two jkbms with software running nicely, took a bit of trial & error. Example of this was I loved the float setting in aggregate software, but this override “no export” setting and export for me is not allowed, so I now don’t use float at all. Read Mr manual & gigavolt guidance a few times to grasp settings, ping on here if you need clarification on any individual setting. PS I had parallel batteries running for a long time without issue before I finally installed aggregate software.
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- Not possible, given all batteries presumably share the same source, to achieve this all batteries would require their own charging system or additional hardware to limit current to / from individual battery.
Pps my system has 2x jkbms( older non inverter type), mp2gx, 4x mppt, 1x shunt and separate SMA ac parallel inverter.
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Thanks for your great reply. I really appreciate it.
I have the serialbattery software going in the Cerbo GX and will now select one of the smaller EVE LF304 batteries as the “main” battery and hope the rest will play together nicely. This is a 100% off-grid battery system powering 5 MultiPlus II 5000VA inverters and 5 Orion 240W DC to DC converters 24hr a day. As it is with solar power, when the sun comes out I need to make the most of the 4-5 hours per day when production is good. Overcast days is when the panic sets in. With 84 Jinko 270W solar panels connected the charge current can be very high so I am want to put every possible measure in place to ensure nothing goes wrong during charging.
In relation to the Dr-Gigavolt dbus-aggregate software/driver, I am at a toral loss. I will be able make a start one I can have a look at a settings.py file of a working system and I can then ammend it to match my system. The example given by Dr-Gagavolt has a huge amount of clutter which I guess has no real need to be there. I guess the main settings will be a line for each battery, a line for each MPPT (cannot really see why) and some charge parameters.
So a clutter free example (even without any notes in the file) will be a huge help. Can you please copy your settings here into the chat?
If you feel you need to change the device names or other identifiers to protect your privacy it is perfectly fine with me.
Thanks for your assistance.
Note : when you don’t use aggregate, GX will be given info from whichever battery you choose. Eg if you have 5 x 280ah batteries and you choose one of these as main , system will take data from that BMS and if you have this battery as 289ah in jkbms settings, the GX will charge according to info received - namely 280ah capacity, when in fact you have 1400ah.
I’ll see what I can do in regards aggregate settings file.
Solarinstaller, have you also posted the same post on diysolarforum.comcom ?