Creating a home lab DC UPS using Victron parts

DIY
1

Hi!

I am looking at making a DC UPS type system for low voltage DC devices in my home.
I would like to be able to use the DC power supply to both charge a LiFePo battery and/or power the devices - so I am looking at separating the mains power supply from the battery charger.

It looks like the Orion-Tr DC-DC Charger can be used for this purpose:

However SmartSolar Charge Controller seems to be significantly cheaper - and have VE.bus connection for monitoring:

I don’t need MPPT (it will be a constant voltage), but is there any disadvantage to using a SmartSolar Charge Controller for this purpose?

Thanks!

nick.

2

A couple of things to consider. The Orion boosts voltage if required from say 12V to 14.4V, the MPPT does not. The MPPT needs an input voltage 5V higher than the output battery voltage to start working.

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Thank you! That is really helpful. Hopefully I can cope with the power supply being 5v higher than the battery voltage. I am going to have some additional DC-DC converters after the battery.

4

Note too that the mppts also have an Input Current (short circuit) Limit specified. Take care…

5

Thanks JohnC.

In the MPPT manual it refers to Error 38 and/or 39 - PV Input shutdown.

To protect the battery from over-charging the PV input is shorted.

Does this mean that the charger will short the input pins, in order to protect the battery?
I don’t want this to happen to my power supply!

6

Using a solar charger as anything other than a solar charger is not supported, and in most cases not a very good idea.
What is your end goal? I see reference to putting a power supply on the input, but what’s powering the power supply, exactly? If it’s an AC-to-DC power supply, then there’s no benefit to not just using a proper AC-to-DC charger to keep your batteries charged. If it’s a DC-DC power supply, then assuming there’s a battery on each side, a DC-DC charger would be the appropriate component to use, with the DC-DC charger connected directly to each battery (not connected to a battery on one side and a power supply on the other).

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7

Thanks for your replies in November! Just been spending some more time thinking about this and created a diagram of my new design.

My goals are:

  1. Creating a DC UPS: my DC equipment will keep running, even if there is no mains power
  2. Powering DC devices in my house using cheap electricity, stored in the LiFePo4 batteries overnight.

Here is my design:

DC Power Distribution - pictures
DC Power Distribution - pictures1920×949 85.7 KB

My load will be around 80W and the Victron charger is 384W - so there should be enough to power the load and charge the battery at the same time.

The Sonoff switch will be used to switch the mains to charger on and off at different times of day.
A future enhancement will be to use a Smart Shunt to monitor the batteries and switch on the charger if the batteries get low - although based on a fixed load and schedule, hopefully this won’t happen.

A couple of things I am not certain about:

  1. Can I really just connect the load, charger and battery all together on a fused bus bar?
  2. If the charger is both charging the batteries and powering the load at the same time, is it able to detect the battery voltage and set the correct voltage for the state of charge?
  3. Can I connect two batteries together in series, with separate BMSs and all the cells remain balanced? Presumably the two BMS are unaware of each other?