Blocking diodes for paralleled panels?

[CatNewBee]

Originally Posted by skipgundlach

I don't have that setup, but modern controllers often have the ability to tandem to handle larger loads.

Perhaps one here who has such could post their info...

no tandem, just use each with separate panel strings. Tandem works only with few of them, than additional communication between the controllers must be set up (master/slave).
you can use as many controllers connected to the battery bank in parallel as you like. each of them must be configured properly of course for the battery chemistry.

[skipgundlach]

Originally Posted by Paul Elliott

With a "12V panel" (about 17V Vmp), a blocking diode will dissipate about 3% of the available power. If 3% is important to you, take out the diodes. Remember that we are overjoyed if we get an extra 10% by using an MPPT controller.

If you have higher-voltage panels, or a series-string of panels, then the blocking diode loss will be proportionally less.

Our panels are ~60V, 6A, if memory serves...

Not likely to cause great loss, and the controller is, indeed, MPPT...

[CatNewBee]

I do not want to repeat myself too often. The blocking- (or string-) diode protects a damaged panel / damaged string from the reverse polarity power of the other strings. In normal operation it does not do much meaningfull, so youll not experience any difference.

You'll learn to like it, when you have a dead cell / hotspot, that fryes your fiberglass below your flex panel and starts a bonfire on the roof.


https://www.photovoltaikbuero.de/en/...ltaic-systems/

[john61ct]

Originally Posted by skipgundlach

I don't have that setup, but modern controllers often have the ability to tandem to handle larger loads.

No, any collection of nominal 12V sources, no matter how disparate can be stacked concurrently charging. Wind, hydro, solar, alts, genny, whatever.

As long as none by itself are damagingly out of spec.

Nothing special is needed to "coordinate" their profiles.

[hzcruiser]

Originally Posted by Tikka

never ever use 2 controllers connected parallel to one bat. bank.

Can you support this statement with useful facts, as that would be news to me and quite a few others here? But, hey, what do we know...

[john61ct]

People are sometimes wrong, we all make mistakes.

[skipgundlach]

Originally Posted by john61ct

No, any collection of nominal 12V sources, no matter how disparate can be stacked concurrently charging. Wind, hydro, solar, alts, genny, whatever.

As long as none by itself are damagingly out of spec.

Nothing special is needed to "coordinate" their profiles.

This originated with a question of stacking controllers, not sources.

That said, are there any here who DO stack multiple incoming sources to an MPPT controller?

In our case, we have shore power (two - one strictly shore power, the other part of our inverter-charger) chargers, wind, alternator and MPPT controlled solar, all connected to the house bank positive. All have controllers on them, and they play well with each other.

I can't imagine stacking incoming on a MPPT controller, as the voltages would all be very different (our solar, e.g. is paralleled - the source of the discussion on blocking diodes - at ~59VDC/max~6A [each; together it's max ~12], but all the other are nominal 12V, varied by state of charge to more than that, but nothing like the solar voltage)...

So, multiple sources into the receiving end of charges, sure. Not at all sure about multiple sources into a single controller...

[john61ct]

Originally Posted by skipgundlach

This originated with a question of stacking controllers, not sources.

A solar controller **is** a charge source, as is an alt, mains charger whether shore powered or from a genset, wind power, hydro.

I was talking about stacking multiple such charge sources in parallel concurrently into a battery, being no problem.

I don't know what you mean about "charge source into a SC", IMO anything but panels is a science experiment, but in any case not what I meant.

[skipgundlach]

Originally Posted by john61ct

A solar controller **is** a charge source, as is an alt, mains charger whether shore powered or from a genset, wind power, hydro.

I was talking about stacking multiple such charge sources in parallel concurrently into a battery, being no problem.

I don't know what you mean about "charge source into a SC", IMO anything but panels is a science experiment, but in any case not what I meant.

SC=solar controller; sorry for the obfuscation.

And I agree about multiple sources into the battery, as I have 'em

[RaymondR]

Originally Posted by john61ct

No, any collection of nominal 12V sources, no matter how disparate can be stacked concurrently charging. Wind, hydro, solar, alts, genny, whatever.

As long as none by itself are damagingly out of spec.

Nothing special is needed to "coordinate" their profiles.

If it's DC within the voltage specs and each of the sources has blocking diodes the controller they are feeding doesn't give a damn where it's coming from.

[hzcruiser]

Originally Posted by RaymondR

If it's DC within the voltage specs and each of the sources has blocking diodes the controller they are feeding doesn't give a damn where it's coming from.

From the last few posts here I got the impression that some are talking about stacking panels onto one solar charge controller (SC or SCC) whereas others are discussing charging a battery bank from different chargers in parallel.


The original title suggest the former and the consensus seems to be that one can use blocking diodes but it's not absolutely required. If you put them in you loose some Watts, if you don't there is a small chance that a panel overheats if there is a fault.

[john61ct]

Originally Posted by RaymondR

If it's DC within the voltage specs and each of the sources has blocking diodes the controller they are feeding doesn't give a damn where it's coming from.

Again my statement has nothing to do with feeding a solar controller. And nothing to do with any theoretical need (or not) for any sort of diode.

My point considers any SC+its panels to be like a black box unit, acting as a generic charger attached directly or via a buss to a battery.

Only talking about stacking these various disparate charge sources, including multiple SCs, in parallel on a single storage battery bank.

wrt the inputs to a SC, most of them are designed to only accept input from panels.

To further clarify, I was pointing out simply that this

Originally Posted by Tikka

never ever use 2 controllers connected parallel to one bat. bank.

is dead wrong

And that this

Originally Posted by skipgundlach

I don't have that setup, but modern controllers often have the ability to tandem to handle larger loads.

Perhaps one here who has such could post their info...

is also wrong, to the extent that it implies coordination is required to do such stacking.

[roland stockham]

On a slight thread drift. I have 2 100w panels rigged in series either side of the boat to a single MPPT controller. often one has indirect sun when the other has full sun. One of the bypass diodes (2 per panel) has blown and had to be removes as it was shorting the panel section.
Can someone clarify if there is ant danger of burning out cells on the panel with less light. Very hard to get blocking diodes here!

[john61ct]

Best in that scenario to go 1:1, separate MPPT controllers per side of the boat.

The smaller Victrons go for ~$120

[roland stockham]

Originally Posted by john61ct

Best in that scenario to go 1:1, separate MPPT controllers per side of the boat.

The smaller Victrons go for ~$120

Plus 3 days on a bus to the nearest chandlers and back or wait 1 month for delivery, neither of which are practical. here if the local hardware store does not stock it then tough! But am i likely to blow the panel if I leave it like that for a couple of months?