question

raven avatar image

DC/DC converter on MPPT load output. not possible ?

Hello !

I have an orion 24/12 20 Amps DC/DC Conveter on the load output of an mppt 75/15 (victron) on a 24V system. Both devices are well functionning separetely but not together. Is that a normal thing ?

In the above mentionned setting i get an output voltage varying between 3 to 4 volts instead of 12.3V if i plug the Orion straight on the batteries.

Cheers,

R.

MPPT ControllersOrion DC-DC Converters not smart
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3 Answers
wkirby avatar image
wkirby answered ·

I would not expect a DC-DC converter to work very well on the MPPT load output.
The MPPT load output circuitry would reject the high inrush current of a DC-DC converter.

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Thanks. I was trying to use the low battery voltage disconnect of the mppt load output for my 12V consumers. Any good way to have that load disconnect on the output of my Orion DC/DC converter to protect the battteries from deep discharging ?


Cheers,


R.


joanspark avatar image
joanspark answered ·

As per wkirby the DCDC converter (240W) probably overloads the output of the MPPT (12V/15A ~ 180W) with the inrush current (charging up capacitors and what not).

The manual of that MPPT series (pdf, page 6) tells the following story:
".. Some loads (especially inverters) have a higher current rating or start-up current rating. The current is higher than the load output can support. These loads should be connected directly to the battery. It is possible to control these loads by the solar charger so that a deep battery discharge is prevented. This can be done by connecting the load remote on/off terminals to the solar charger load output. Depending on the type of load, a special interface cable might be needed like an Inverting remote on/off cable

..

Alternatively a BatteryProtect can be used to control the load."

If you use LiFePO4 batteries they ususally come with a BMS that will disconnect itself if the battery voltage goes below a set value to protect the battieres. In that case you don't need the load switch and can connect the DCDC converter directly (via fuse) to the batteries.

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Mark avatar image
Mark answered ·
I’ve got my dc/dc charger(12/12-9) switched by the bmv on Soc and connected to the load output of my 75/15 to trickle charge my starter battery. It works flawlessly,because the dc/dc only pulls 11.5A on start up!
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Hi Mark,

Can I ask a question. This is the set up I'd like to have on my van. I have a 75/15 charging the leisure battery and I'd like it to trickle charge the starter battery.

I think I can figure out connecting the dc/dc charger to the load output.

I'm not familiar with what 'switched by the bmv on Soc' means? Would you be willing to explain or point me in the right direction.


Thank you.