Using MPPT 75/10 as 24V/12V DCDC

Q&A and troubleshooting
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1

Hello,
I would like to charge a 12V lead acid battery from a 24V supply net. Victron has Chargers design for this purpose. However, they all have the problem that there is no current limit configurable.

In my use case, I need to limit the input current to about 1.5A. This is not possible with the Orion TR and others.

However, it is possible with the smart solar chargers by limiting the output current, which is configurable.

But there is the following note in the data sheet:
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My 24V source is able to deliver more than 20A of current for a few seconds.

In another version of the data sheet I found that:
datenblatt-1924460-victron-energy-scc075015060r-laderegler-mppt-12-v-24-v-15-a.pdf
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In english: A higher short circuit current can damage the controller in case of reverse polarity of the solar modules.

Reverse polarity is not problem in my use case.

What are your thougths? Can I do this or do you have better ideas?

2

No, you can’t limit the input power of an mppt charger, as it will always search for the sweet-spot on the incoming line.

But you’ll find dozens of small chargers fi on Amazon.

3

Dc/dc converter with cc and cv on amazon for 20 bucks

4

I don’t like to use a noname product from china with unknown quality. Or do you have a specific suggestion for a good quality product?

In my case I would limit the output current per configuration, so the input current should be limited automaticaly. If the output current is limited, the MPPT cannot search a sweet spot. It then works as normal DCDC.

I like to understand the restriction about the input current limit of the modules and why there are different formulations in different data sheet versions.

5

You think…

6

Please do not use a solar controller as a DC-DC charger. It is not supported, and is likely to cause damage to the solar controller and/or the surrounding components. PV input is for PV panels only.

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