We currently have a Rentech BTESF48V100-R battery with a Sunsynk 5kw inverter, I am not sure if comms work between the two but it seems like it does according to Rentech.

The manual states batteries with the CAN bus communications option are compatible with the pylontech protocol, I set the battery type to lithium with protocol 0 and the battery shows comms under libms but only when I put up the first dip switch and if I I put the first dip switch down then there are no more comms.

Weird thing though is it seems like the battery voltage gradually drops from 55.1 and it doesn't seem to stop dropping, I let it drop to see what happens and when I switch to a different battery type like agm the voltage goes straight back to 55.1 so I am not sure if the voltage is actually dropping or not.

I am starting to think that comms are not supported through CAN on the battery, they have two battery types one R series and one R-CAN series which is new and I suspect my series does not support comms through the CAN port.

I know probably not the best batteries to use but due to family falling for fly by night electricians we are stuck with it after already having to get a new inverter after they installed a nonsense inverter.

Any input here would be appreciated.

On 2023/11/08 at 7:28 PM, Ronnie1102 said:

 

Weird thing though is it seems like the battery voltage gradually drops from 55.1 and it doesn't seem to stop dropping, I let it drop to see what happens and when I switch to a different battery type like agm the voltage goes straight back to 55.1 so I am not sure if the voltage is actually dropping or not.

Where are you getting the volt readings from?

With coms enabled, the battery will be fully charged at around 55.2v. It willl then settle to around 53.5v as the cells balance and they reach resting voltage. Seeing that communication is enabled, the BMS will adjust the inverter voltage to match the gradual reduction in the cell voltage.

The same happens in AGM mode, the only difference is the inverter will keep on supplying 55.2v (or whatever the max charge voltage is set at). The actual battery viltage will still drop 53.2 as the cells balance, but when you measure the voltage at the poles you will get a reading of 55.2v (since the inverter will keep on supplying 55.2v). The charge voltage or float voltage supplied by the inverter at this stage is irrelevant as the BMS have disconnected the cells from the inverter supply.

In other words, when you change from Lithium to AGM that sudden chage in voltage as displayed by the inverter does not actually trnaslate into a similar change in the voltage of the actual cells.

Both scenarios above are normal behavior and does not indictate that the comm are not working.

Edited November 9, 20232 yr by I84RiS

6 hours ago, I84RiS said:

Where are you getting the volt readings from?

With coms enabled, the battery will be fully charged at around 55.2v. It willl then settle to around 53.5v as the cells balance and they reach resting voltage. Seeing that communication is enabled, the BMS will adjust the inverter voltage to match the gradual reduction in the cell voltage.

The same happens in AGM mode, the only difference is the inverter will keep on supplying 55.2v (or whatever the max charge voltage is set at). The actual battery viltage will still drop 35.2 as the cells balance, but when you measure the voltage at the poles you will get a reading of 55.2v (since the inverter will keep on supplying 55.2v). The charge voltage or float voltage supplied by the inverter at this stage is irrelevant as the BMS have disconnected the cells from the inverter supply.

In other words, when you change from Lithium to AGM that sudden chage in voltage as displayed by the inverter does not actually trnaslate into a similar charge in the voltage of the actual cells.

Both scenarios above are normal behavior and does not indictate that the comm are not working.

I get the reading from the inverter.

Thank you for the explanation, I guess I will try with comms and see what happens I was just not sure if this was normal behaviour or not.

Thanks @I84RiS kept the comms connected last night without any issues, voltage dropped and settled at around 52.30 on the inverter.