Feed MPPT75/15 with a 48V/7.3A (350W) dc power supply and use 24V battery bank

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tkmbe asked Dec 23, '19

Feed MPPT75/15 with a 48V/7.3A (350W) dc power supply and use 24V battery bank

I read several threads in this forum about using MPPT with a dc power supply.

I want to do this, but have a doubt.

If I put at PV input a switchable dc power supply for example 48V/7.3A (350W) and use 24V battery bank I can get a current of about 14A (calculation without loss)

So I guess limit output current to battery to 10A will be fine and not burn up dc power supply nor the PV input which has a max input of 15A (I have 7.3A input)?

With this constelation I have a efficent UPS for 24V devices, battery low discharge protection and a data logger. Is this not nice?

dc system ups

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Answer 1 · 2019-12-24T02:12:01Z

Guy Stewart (Victron Community Manager) answered · Dec 24, 2019 at 02:12 AM

Aside from the data logging, is there any reason not to use the intended product for this application, the 48V to 24V Orion DC to DC instead?

https://www.victronenergy.com/dc-dc-converters/orion-tr-dc-dc-converters-isolated

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Answer 2 · 2019-12-26T16:14:54Z

tkmbe answered · Dec 26, 2019 at 04:14 PM

As I see the orin son dc dc converters

I have 220V input, need a power supply and a orin dc dc converter which has a higher price as the solar charger. A part with my solution I can change the power supply with a solar panel and that's it...

So what is the pro to use this dc-dc converter?

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Warwick Bruce Chapman commented · Dec 26, 2019 at 09:24 PM

The pro is it is the right tool for the job. It was designed to do that job you need done (converting 48 to 24v) whereas the MPPT is designed to convert a variable voltage and fluctuating current to something usable.

If you need to sometimes swap out the 48v source (as I understand this is a 220 AC to 48v DC power supply) with solar panels then the Orion will likely not work as the input voltage will be out of the expected range.

But read the data sheets on each.

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