question

victronitnerd avatar image
victronitnerd asked

Battery charger on pv input side of MPPT (experimental)

So I tried to do some research on using a dc charger on the pv input side of an MPPT and didnt really find many people doing it (for good reasons and very few probably need this), I could find various people saying dont do it, bad things can happen, not the products intended use etc.... My reasoning is that I can make use of surplus A/C energy and in theory could trigger cheaper tarrif rates, increase charging currents beyond the mutiplus limits etc.. AND more importantly I want the batteries built in BMS to control charging rates through victron comms.

Anyway... as an experiment I wanted to test if this was possible and so far my small experiment seems fairly stable and useable.

Using a 150/35 MPPT with a regulated DC charger on the pv side seems to provide a nice steady charge current. The charger is 12-84v / 1-25a and I can fix both the voltage and current (claims to have all the usual protections). I set the MPPT to charge at a max of 20-21amps so that its pushing about 80% of the chargers rated max with a voltage of about 59v which seems to work well.


Have I overlooked anything obvious that could be a concern? I get this is a small scale limited experiment and not pushing massive a current to charge but it does have its other benefits that make this worthwhile (I feel).


mppt-dc-to-dc-3.png


MPPT ControllersMPPT SmartSolarPylontech
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1 Answer
chrigu avatar image
chrigu answered ·

At its core, an MPPT is a buck converter with additional voltage and current measurment, and fancy software.

So any energy source is fair game if you ask me. But of course apart from PV panels, nothing else is officially supported and very likely will void your waranty.


Apart from that, why not use a bluesmart charger?

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victronitnerd avatar image victronitnerd commented ·
Thanks, yeah I get that its not supported but cannot see a reason why it wont work without issue.


Regarding the bluesmart charger, afaik theres no 48v one and no charger that works alongside other mppt's, inverters etc.. and honours what the BMS wants.


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chrigu avatar image chrigu victronitnerd commented ·

Oh, of course, the only chargers at 48V are skylla TG. I should have known, not long ago i installed a Multiplus 48/2000 as a charger, because it was 60% the price compared to the skylla, at the same charge rating plus the possibility to use its ACout should it ever be necessary

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