The Schaudt WA121525 B2B charger (booster in Schaudt language) has, as reported many times on this forum, some shortcomings when used with its Lithium charge profile. As a charger it works well putting in a pretty consistent 25A at the start of the charge cycle in contant current mode. However, there are 2 main issues:
1. Probably the most serious is that it allows charging at low temperatures. This then relies on the batteries BMS to prevent damage. The BMS should not be the primary method of protection.
2. It charges at a fixed 14.4V when in constant voltage mode at the end of the charge cycle. The charger only has bulk and absorption charging stages and will hold at 14.4V until it switches off.
Number 2 in practice with real life driving between stops may not provide too many issues. The worst case is when you have just come off mains hook up or a solar panel has already brought the battery to 100% and then you drive off for 6 hours.
I didn't particularly want to ditch the Schaudt charger. We already added a Victron Smart Shunt, Victron MPPT solar charger and Victron mains hook up charger. I was already interested in playing with Victron OS on a Raspberry Pi and overcoming these issues was another good reason to add the Pi into the build.
The larger image version of the Pi Victron OS includes NodeRED. This graphical programming system allows some simple ways to add extra functionality as well as creating your own Dashboards for monitoring. A Pi Relay HAT was also added on the Pi4 to provide control of the D+ enable signal to the B2B.
NodeRED
The nodeRED routines I have created provide the following functions:
A. Prevents charging at low temperatures by monitoring the Smart Shunt alarm status. When the alarm is activated the charger is disabled. I could have coded the temperature value in but, by using the alarm status, the value can easily be changed if required in the Victron app.
B. Prevents continuous charging of the battery once 100% SOC is reached. At 100% SOC a 30 minute timer is started. This allows time for the battery BMS to top balance at 14.4V. At the end of 30 minutes at 100% SOC, the charger is disabled. It is re-enabled at 95% SOC and the cycle would repeat if applicable.
C. Provides a Storage Mode for maintaining the Lithium battery between 60% to 70% SOC from solar charge when not in use. This is not an issue in winter but is useful in the summer months when PV yield is higher. The system disables and enables the MPPT.
C. Displays a Dashboard on a web browser that provides easy monitoring of the system status. It is nothing fancy and was originally created as a test environment. In practice this Dashboard is quicker to load via the van local WiFi network than opening the Victron app or VRM.
D. The Dashboard also includes switches to enable/disable functions and provide overrides if required.
The system has been in use for 12 months now and, apart from a few tweaks, it is working well.
(Before anyone says, I know there are easier and cheaper solutions to some of these issues but I did it this way because I can and wanted to!)
Screenshot of the Dashboard during current trip (end of day so no PV charging):
1. Probably the most serious is that it allows charging at low temperatures. This then relies on the batteries BMS to prevent damage. The BMS should not be the primary method of protection.
2. It charges at a fixed 14.4V when in constant voltage mode at the end of the charge cycle. The charger only has bulk and absorption charging stages and will hold at 14.4V until it switches off.
Number 2 in practice with real life driving between stops may not provide too many issues. The worst case is when you have just come off mains hook up or a solar panel has already brought the battery to 100% and then you drive off for 6 hours.
I didn't particularly want to ditch the Schaudt charger. We already added a Victron Smart Shunt, Victron MPPT solar charger and Victron mains hook up charger. I was already interested in playing with Victron OS on a Raspberry Pi and overcoming these issues was another good reason to add the Pi into the build.
The larger image version of the Pi Victron OS includes NodeRED. This graphical programming system allows some simple ways to add extra functionality as well as creating your own Dashboards for monitoring. A Pi Relay HAT was also added on the Pi4 to provide control of the D+ enable signal to the B2B.
NodeRED
The nodeRED routines I have created provide the following functions:
A. Prevents charging at low temperatures by monitoring the Smart Shunt alarm status. When the alarm is activated the charger is disabled. I could have coded the temperature value in but, by using the alarm status, the value can easily be changed if required in the Victron app.
B. Prevents continuous charging of the battery once 100% SOC is reached. At 100% SOC a 30 minute timer is started. This allows time for the battery BMS to top balance at 14.4V. At the end of 30 minutes at 100% SOC, the charger is disabled. It is re-enabled at 95% SOC and the cycle would repeat if applicable.
C. Provides a Storage Mode for maintaining the Lithium battery between 60% to 70% SOC from solar charge when not in use. This is not an issue in winter but is useful in the summer months when PV yield is higher. The system disables and enables the MPPT.
C. Displays a Dashboard on a web browser that provides easy monitoring of the system status. It is nothing fancy and was originally created as a test environment. In practice this Dashboard is quicker to load via the van local WiFi network than opening the Victron app or VRM.
D. The Dashboard also includes switches to enable/disable functions and provide overrides if required.
The system has been in use for 12 months now and, apart from a few tweaks, it is working well.
(Before anyone says, I know there are easier and cheaper solutions to some of these issues but I did it this way because I can and wanted to!)
Screenshot of the Dashboard during current trip (end of day so no PV charging):
