question

siletzspey avatar image
siletzspey asked

Load-side Switches on Charge Controllers

Is it true, as many claim, that an MPPT charge controller (CC) will burn out if the battery side is disconnected while the PV side is connected and powered? Victron's CC manual stresses connecting the battery side prior to the PV side.

I see many commercial and DIY wiring diagrams with a switch (or breaker) on the CC battery side, in addition to a master battery switch. It would seem that using either switch could burn out the CC. Thoughts?

Does this concern mentioned with "solar" or "MPPT" CCs also apply to DC-to-DC (alternator to battery) CCs?

As my rookie mind considers CC burnout, and CC needs for standby power from the battery side, it would seem wiring approach #1 would be best. The Master Batt Switch really acts as a LOAD disconnect. The downside is CC parasitic draw on the battery.

(1) PV > Switch/Breaker > CC > Fuse > BATTERY > T-Fuse > Master Batt Switch > LOADS

A tempting alternative is #2 so that the Master Batt Switch acts as a BATTERY (vs just load) disconnect, but I've heard concerns that loads could be confused/harmed by the fluctuating PV/CC output without a battery in the mix to normalize things. Another downside is the CC loosing standby power and loosing its settings.

(2) PV > Switch/Breaker > CC > Fuse > LOADS <> Master Batt Switch <> T-Fuse <> BATTERY

I appreciate there are trade-offs, but am looking for something reasonable in my truck camper, which will have PV, Alternator and Shore sources into 200Ah of batteries, and then just DC devices aside from a ~250W inverter downstream.

Thanks

MPPT Controllerswiringswitch
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2 Answers
Guy Stewart (Victron Community Manager) avatar image
Guy Stewart (Victron Community Manager) answered ·

Hi @siletzspey,

Please see my answers to this other community question - https://community.victronenergy.com/questions/38304/using-a-smartsolar-mppt-10030-with-a-common-port-b-1.html

It addresses some of the main issues you raise in your question.

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siletzspey avatar image
siletzspey answered ·

Thanks Guy!

Does this discussion for a SmartSolar controller apply equally to the Orion-Tr Smart controller?

Thomas Gilg

2015 F350 + 2018 NorthernLite 9'6" TC


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