- Sep 29, 2007
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- Motorhoming since 2006, 30 years tent camping in Africa
Unfortunately you will get drift through time, both the BMS and the shunt. By tweaking and experimenting with the shunt settings you may eventually stumble across your particular (and exact) peukert and charge efficiency.Hi Roger, thanks for the reply. I set the XS to 14.2 as discussed with you and it seemed to cut off ok at 100%. The Shunt is a BMV702 which I set to the values you recommend in your video. The 702 is a pain as it has to be disconnected from the Cerbo to connect the Bluetooth dongle to see the settings which is not easy when installed in a panel and I am concerned about too much stress on the tiny wires. I am surprised it can’t be viewed and modified with the CerboGX on the Pi. I have just checked the software version on the XS and it is Firmware v1.03 so I will have to download v1.04 as suggested by AdrianChen.
I have checked the whole installation with my Infra Red camera and there are no “HotSpots” on the batteries or any of the terminals or cables. One of my bus-bars is slightly warm at 40C so I will have to check that when I get home.
I will be able to plug-in for about a day tomorrow so will do that but I am very surprised how far everything has drifted out. How can the BMS’s be so far different to the Shunt and show a difference in the cycles when firmly in parallel. It is hardly worth having the app if the BMS can show charge values of 52% & 67% when the shunt shows 20% that is a hell of a difference and which do I believe.
It is rather defeating the perceived benefits of Lithium if it is a requirement to go onto hook-up regularly.
The easier way is to charge fully to 100% so “everyone forgets their differences” (ie all your SOC indicators agree with each other) coz they’re all 100%
I mentioned the 14.3 because it removes a little margin for error, basically forces the BMS to definitely reach high cell volt disconnect.