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yuri avatar image
yuri asked

Victron MPPT 100/30 input over-current protection?

Is it safe for controller to connect it to solar array much bigger then controller rated output power? Let's say, would it be safe to connect it to 75V 3000W solar panels? I understand that max output MPPT controller would be up to 420W for 12v battery, but would like to know if it's safe for controller input?

Also would it be safe for MPPT 100/30 if I connect charged 24V battery to its input instead of solar panel to charge my 12v battery bank? May I assume controller will not fry itself, but will take 420W from input battery?

MPPT Controllersinput current
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1 Answer
Justin Cook avatar image
Justin Cook answered ·

@Yuri, the MPPT input is overcurrent protected and NOT overvolt protected, but no... no, this is absolutely not a good idea. You're looking at trying to overfeed your controller by almost ten times its rated capacity; no matter its own current limitation, you're either going to melt your panels or in the best possible case you're going to melt your controller. All other options are worse than that.

As for your second question... sort of, but not really. Yes, you can hook a 12v battery up to the batt terminals and a 24v battery up to the PV terminals, but you're not going to get any significant current flow between them unless you have something else charging the 24v battery at the same time.

Please consult an electrician or an experienced installer before you destroy your equipment or yourself!

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yuri avatar image yuri commented ·

Thank you for the answer. I have one more question :)

I have DC-DC converter connected to my van 14V alternator, so I have 35V output at about 20A max. Would it be safe to connect that 35V source to MPPT 100/30 to let it charge my battery bank? The main concern is MPPT input overcurrent protection, as that 35V internal impendance is low. May I assume MPPT controller will not try to short input to determine max current and will not fry itself?

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Justin Cook avatar image Justin Cook ♦♦ yuri commented ·

That should actually work fine, yes. I've seen similar setups using a Victron Buck-Boost from 12v nominal to 24v nominal, into the PV side of an MPPT connected to a 12v nominal bank, using the MPPT as an intelligent 3-stage charger, and they worked well... can't speak as to their longevity, really, as it's not a manufacturer-supported use of the devices, but at least two of the systems I've seen hooked up that way had been in successful operation for over 6 months without any problems.

Just make sure that all your cables are fused properly at the batteries and between devices, and if you fry something hooked up that way... well, good luck with any warranty claims :-/ The safest thing to do would be to wait another few months until Victron releases their smart B2B charger, or just go buy a Sterling B2B charger right now. Do it right once and be done.

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