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bluejeans avatar image
bluejeans asked

Would this circular reference tear the fabric of the space time continuum? - Powering USB hub direct from battery

I just got my RasPi in the mail. I am going to try to set up the Venus OS on the bench with a DIY solar gen, to make sure I can make it work with the SCC and smart shunt before an RV install.

Thinking ahead to the installation, can I get this 12v powered USB hub and just cut the 12v wall wart and connect to the battery?

https://www.amazon.com/dp/B0797NWDCB/?coliid=I2TW9QUKHNBBQY&colid=VZLJUIYLOXA8&psc=1&ref_=lv_ov_lig_dp_it

Then... the tearing the fabric part....can I power the RasPi through a Charge only USB, while connecting the output cable of the hub to the RasPi, to feed the Victron devices at the data ports on the hub?

Raspberry Pi
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Peter Buijs - NL avatar image
Peter Buijs - NL answered ·

Some of the smaller MPPT chargers from Victron have a Load output, maybe you can power the USB hub from there.

Otherwise you have to be sure the hub will survive the higher charge voltages from the battery, personally I would install a DC-DC (IN 8-20V OUT 12V) converter to power the hub.

Raspi's are very sensitive for a clean and sufficient powersupply, minimal 2,5-3A

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bluejeans avatar image bluejeans commented ·
What happens to the MPPT load output when the sun goes down?


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chris-hartmann avatar image chris-hartmann bluejeans commented ·
I've got my rpi powered through the usb port on the MPPT. It pulls its power from the battery so its not affected by the absence of solar.
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Kevin Windrem avatar image
Kevin Windrem answered ·

Some USB hubs interrupt outputs when the controlling device (the PI in this case) reset. That would interrupt power to the PI causing it to reset again. You'd be better off with a dedicated 5 volt DC to DC power supply. You can find these with USB or USB-C connectors that will plug directly into the PI.

Also, watch out for USB hubs with switches. Some reset to off when power is interrupted which could happen during PI reboot.

This is the one I picked out:

https://www.amazon.com/Anker-7-Port-Adapter-Charging-iPhone/dp/B014ZQ07NE

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bluejeans avatar image bluejeans commented ·
how do you power the hub?
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bluejeans answered ·

Boooooooooya!

I got the Pi set up and connected to VRM. I can see everything directly though my wifi network and through VRM. Only there is nothing to see.

I am waiting on pieces to build my VE direct cables. I can build 3 cables for half the price of one from Victron, and of course make them custom lengths. So building cables is next, along with some form of direct view screen. Not sure which route I will go. I may try 2 different routes as I already have most of the stuff to build for one route

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Kevin Windrem avatar image Kevin Windrem commented ·
Make sure your USB to VE.Direct cables are ISOLATED. This is extremely important to prevent ground loops that can throw off measurements, resulting in incorrect system behavior.
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mvader (Victron Energy) avatar image mvader (Victron Energy) ♦♦ Kevin Windrem commented ·

Hi I can second that. And since this is such a recurring discussion, I added some words about it to the Rpi manual just now


https://github.com/victronenergy/venus/wiki/raspberrypi-install-venus-image#connection-to-a-vedirect-product

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Mike Dorsett avatar image Mike Dorsett commented ·
I'll add to that: you MUST use isolated cables for VE direct: I've blown up a couple of pi's by not doing this. Not only is there a ground loop problem, some VE direct run at 5V, some at 3.3. The 5V signals will blow the pi. Leaving volts on the VE direct cable (Tx data to the pi) will blow the pi. I have added this isolation to a BMS interface board for a PI, but there is a world shortage of the isolation chips. Any one know where I can get some?
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