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sven-nurber avatar image
sven-nurber asked

Multiple battery strings with DC-DC converters and example component diagrams and converter configurations ?

Hi Forum. I'm in communication with BMS manufacturers about how best to configure 32 prismatic cells for a marine application. System voltage of 48 although the vast majority of loads are 12. Redundancy is important so we are thinking about qty. 2 16S1P strings with DC-DC converters isolating each string. Are there any examples of such Victron configurations in the wild that I can study ?

BMSOrion DC-DC Converters not smart
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sven-nurber avatar image
sven-nurber answered ·

I found an Orion BMS ( this is confusing given Victron DC-DC converters also called Orion ) document with some mention of such a configuration, but relatively few details. Within document the following diagram which I find an elegant solution.I was hoping for the integration of BMS data on Victron monitoring solution with a vendor like REC BMS, but they responded to parallel strings with a master-slave solution as shown below.

Still looking for examples or more specifics on the DC-DC converter solution if somebody knows of resources. Thank you.


screenshot-from-2020-05-16-13-54-13.png (38.3 KiB)
screenshot-from-2020-05-16-13-52-19.png (267.0 KiB)
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shaneyake avatar image shaneyake commented ·

Orion BMS can also run in a master-slave config.
The reason you don't need a DC-DC battery strings is because once the are joined both strings should be at identical voltages. You still have redundancy if you have a failure in 1 string but you should get them back to the same voltage before rejoining the strings, else you will see huge currents as the equal out.

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Daniël Boekel (Victron Energy Staff) avatar image
Daniël Boekel (Victron Energy Staff) answered ·

Hi @Sven Nurber

Best to make one string at 48 volt, and a separate 12V battery for the 12V DC users. you can charge the 12V battery from the 48V battery.

do not use dc-dc converter per string, that won't work and is not needed.

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sven-nurber answered ·

Thanks for answering Daniël. Be nice if somebody can elaborate on what is involved with such a solution. DC-DC converters seem the most elegant solution for parallel strings to me, but I don't really know what is involved.


Sven

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Daniël Boekel (Victron Energy Staff) avatar image Daniël Boekel (Victron Energy Staff) ♦♦ commented ·

Hi Sven, it is not, the image you showed if typically for high voltage battery systems, for low voltage you'd need very big and expensive dc-dc converters, and a system that can work with them / control them.

Ask yourself: -why would you want multiple strings?

This forum is not the place to explain how to build your own batteries, please consult an expert on that.

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