Powering the Redflow BMS (and other key control electronics)

The ZCell BMS is powered from a DC power source that should be wired to the marked + and - terminals on the unit.

The current BMS hardware model is able to be powered from DC between 9-65 volts, which means it can be directly powered from the same 48V DC bus that the batteries are connected to. This is typically the simplest approach (via a suitable small fuse or circuit breaker). 

Alternatively the BMS can be powered indirectly from an AC power source (i.e. using a small AC->DC power supply).

In an off-grid scenario, it is a great idea to consider:

• Using direct DC power to drive all key system control components if possible (BMS, energy system controller, Internet access modules etc).
• Designing to have at least some (if not all) on-site solar being supplied via DC MPPT solar charger units instead of using AC solar inverters. This results in the DC bus being capable of self-booting from solar alone in a black-start scenario even if an on-site generator fails or is not set up to automatically run when needed.
• Using a small DC/DC UPS module supplying power to key components for at least a few minutes after the DC bus in general runs out of power (or after a fault that shuts down AC output), such that valuable diagnostic data is not lost in such situations.

In in on-grid scenario, where AC power may routinely be present and may wind up being used to power the primary system control devices via AC->DC adaptor units (BMS, Energy system controller, Internet access router etc), considerations are:

• The use of a small DC UPS (as for the off-grid scenario) is still a good option
• Alternatively a small AC UPS unit (especially as a quick approach if continuous power is needed to BMS and system controllers to assist with diagnostics around events that cause a system to power itself down).
• The use of an Automatic Transfer Switch such as the Victron Energy Filax 2 is suggested to power all critical AC powered control components, to ensure uninterrupted energy supply to the BMS (and to other related system control components) across various combinations of AC source interruption and inverter faults and failure modes. 

Examples of DC UPS units that have been deployed in Redflow systems:

• Ubiquiti EdgePower 24 or 54: a 24V or 54V UPS with web management backed up by a 12V battery: https://www.ubnt.com.au/edgepower-54v-72w-dc-psu-with-ups
• Mean Well DRC series: 12 or 24V UPS backed up with a matching battery
• Powershield DC mini-UPS: https://powershield.com.au/product/powershield-dc-mini-ups-12v-18w/

Data sheets for some of these products are attached to this article.

Other Notes:

• The original BMS hardware could only handle 9-28 volts DC and hence required a DC/DC converter or an AC plug pack to power it - it couldn't be directly connected to the 48V DC Bus. However, the current version can handle 48V DC bus power directly. 
• Do not plug a USB power cable into the Micro-USB socket on the side of the BMS unit. That Micro-USB socket should not be used at all - it won't work properly - including that using it will disable the operation of ZCell's built in 'hardware watchdog' function.