MPPT question using different voltage panels

[CatNewBee]

Well, you need the BT dongle or serial cable too to get access to the settings...
99$ is a good price for a 200Wp controller (15A * 14.4V), I think you need something bigger around 30A or two of them if you run a 12V battery system.

(380Wp / 12.8V = 29,7A) 190$ for the Victron BlueSolar 100/30 is also OK, so you can chose to have two separate controller or one large.

[travellerw]

Originally Posted by chouliha

I'm looking at Victron BlueSolar 100/30 MPPT Charge Controller - 30 Amps / 100 Volts

I have the following

1ea Kyocera 12V 70W 17.9vmpp
2ea Shell 12V 80W 16.9vmpp
1ea Solosol 12V 150W 18.36vmpp

Total watts = 380

These panels are run parallel joining into a Blue Sea 12V breaker and then onto the ships buss. Currently not using a MPPT controller

I understand the unit would see all panels as 16.9V.

Would I see much improvement with a MPPT versus without?

Thanks

Chuck
Jacaranda
Mo'orea

If it was me I would install 3 Victron BlueSolar 75/15 MPPT controllers (they are cheap enough). I would put the Kyocera and Solosol on their own controllers.

As to the Shell panels (which our boat has 4 of those exact panels). I would look very closely at the installation and assess shading. IF there is limited to NO shading I would consider rewiring those panels in series. However, if there is shade (i.e. boom, backstay, ect), then leave them in parallel. Ours are installed in series and routinely exceed their rated wattage (pretty good for 15 year old panels).

This config should give you a performance boost, but also provide a nice amount of redundancy. If any one of the strings fails for some reason, you still have 2 providing power.

You could also buy the Bluetooth dongle that would allow you to adjust settings, or you could simply make your own USB cable. There are a few examples on the net for making up your own cable. Of course you could just use one of the built in settings which are pretty good.

[john61ct]

The newer Victron series includes the BT dongle functionality for $20 more per SC.

So $120 for the 15A one.

I would not put unmatched panels on the same MPPT controller, might as well stick to a $30 PWM if you're doing that.

[senormechanico]

Look at the power curves for each type of panel, do the math and I think you won't find that it's all that much inefficiency to bundle them.

[donradcliffe]

First, I don't think that the difference in the MPP will have much affect on your efficiency--its definitely not worth buying three controllers which cost as much as panels do.

Second, I have discovered that there are huge differences between PWM controllers. I replaced the one which came with the Renoigy 100 watt panels with another brand, and was getting twice the current into the batteries, while still offering protection against overcharging.

Third, if you have a good $25 PWM controller, you will not see a big difference by going to MPPT--maybe 15% at most.

[Mike OReilly]

Originally Posted by john61ct

The newer Victron series includes the BT dongle functionality for $20 more per SC.

So $120 for the 15A one.

I would not put unmatched panels on the same MPPT controller, might as well stick to a $30 PWM if you're doing that.

John, is there a negative to running a MPPT vs PWM in the OP’s (or my) circumstance? When I was looking at the whole controller question I was struck how little difference in price these two types were. Given that, I went with the MPPT since all the techie say it is better.

I realize my (and his) set up does not produce the maximal output, but I sure get more than enough out of my system.

[hellosailor]

Depending on who you ask, on how close to capacity you are (because MPPT controllers are most efficient at full rated capacity), and what brand you choose?

MPPT controllers are *always* going to give you a 10-15% gain over a system using anything else.

This is not magic, it is physics.

To OVERSIMPLIFY:
Your batteries can only accept a charge up to ~14.4 volts, then any excess voltage just boils off electrolyte, damaging the battery and being wasted as heat. What an MPPT controller does, is convert the excess voltage into a proper low voltage at a higher AMPERAGE, which the batteries can then absorb. Exactly how they decide to do that varies with the maker. But, for instance, I've seen one that seemed broken, because instead of bulk charging at 13.8 volts, it was charging at only 0.4V over the battery voltage. And every half hour or so, I'd notice it was still just 0.4V over the slightly increased battery voltage. Well, it turns out that charging at fixed voltage is not the most efficient way to do it. And this scheme of constantly measuring and leading the voltage, while pushing all the amperage you can, is more efficient.
MPPT controllers do things like that. They use logic tables and proprietary programming, and charge more efficiently. ALL THE TIME.
So while folks can argue about just how much efficiency each different installation gains, the general range is 10-15%, with some few even claiming more versus older inefficient systems.

[travellerw]

Originally Posted by donradcliffe

First, I don't think that the difference in the MPP will have much affect on your efficiency--its definitely not worth buying three controllers which cost as much as panels do.

Second, I have discovered that there are huge differences between PWM controllers. I replaced the one which came with the Renoigy 100 watt panels with another brand, and was getting twice the current into the batteries, while still offering protection against overcharging.

Third, if you have a good $25 PWM controller, you will not see a big difference by going to MPPT--maybe 15% at most.

The difference will be between %10-%15 in theory from a PWM to MPPT.. Yes that alone isn't enough.. However, the OP mentioned he is a full time liveaboard (like us), so there are other advantages. For me, the rundancy alone is worth the cost of 3 controllers. Of course you could go with 3 cheaper PWM controllers, but I much more comfortable with Victron MPPT. Not only do they have 5 years warranty, but down here in the Caribbean there is a dealer on every island.

You also pointed out the problem with "off brand" chinese PWM controllers. Some are excellent, and others are not. Its really a crap shoot unless you buy a known quality brand (yes Victron makes PWM controllers but the price is much closer then).

Each to their own, but the one purchase I have never regretted in the last 2 years of full time cruising is my Victron MPPT solar controllers. It was a very small price to pay for peace of mind for redundancy and performance!

[john61ct]

Originally Posted by donradcliffe

I replaced the one which came with the Renoigy 100 watt panels with another brand, and was getting twice the current into the batteries, while still offering protection against overcharging.

Please name, ideally link to that controller.

I believe the ones Renogy includes in its "kits" is old-school tracer/epever

[donradcliffe]

Originally Posted by john61ct

Please name, ideally link to that controller.

I believe the ones Renogy includes in its "kits" is old-school tracer/epever

I knew you were going to ask, but the boat and controller got loaded yesterday bound for Florida, and I can't find the records of where I ordered it.

I think it was this one

https://www.amazon.com/PowerEZ-Contr...lar+controller

[john61ct]

I'd be amazed if that is more efficient better than the epever ones.

I'd certainly advise anyone using something like that to take advantage of the crazy cheap price and keep spares on hand.

Personally the ability to customize the charge profile, voltage setpoints Absorb hold times etc are at least as important as a maker with a rep for excellent build quality.

I was assuming $100 per SC was on the very cheap side of possibilities to be considered.

But I completely agree for that budget range, just go for it, bung all the mismatched panels together and be happy with what you get.

[hellosailor]

Something to consider when you are measuring and comparing solar charger outputs, whether they are MPPT or PWM they are still putting out a pulsed DC charge. And pulsed DC (PWM) is actually more like an AC charge.
So what your meter has to say about the average voltage it sees, may vary quite a bit depending on the quality and response time of the meter. This is where obsolete old analog meters still shine, as they only know how to average everything.
Pulsed DC chargers may actually just put out one pulse per second, i.e. when they are trying to suck up weak light. Or, they can be pulsing 100,000 times per second, as the old Delcotron alternators used to do. That's a big frequency range for a "DC" meter to be trying to interpret. So do, some don't.

[john61ct]

If you're trying to measure battery voltage, can't get an accuracy while charges or loads are active anyway.

For judging SoC even somewhat accurately, need to let the bank "rest" isolated for 24-72 hours.

[hzcruiser]

Originally Posted by CatNewBee

It is a good practice anyway to add string protection diodes when having more than two strings in parallel. They are cheap and reduce the voltage of the panel only by 0.2..0.3V, look at the spec for the Voltage / Amps of the diodes before buying,

That would be good, only I can't find a 'simple' Schottky diode with a forward voltage of less than 0.5V at >1A on Mouser, RS, nor Digikey.. They average more like 0.7 to 1.0V. At 16V input that's about 6% loss. Difficult to avoid, though, unless you use a latching relay (or some rare SPV1512 'cool switch').

[CatNewBee]

Originally Posted by hzcruiser

That would be good, only I can't find a 'simple' Schottky diode with a forward voltage of less than 0.5V at >1A on Mouser, RS, nor Digikey.. They average more like 0.7 to 1.0V. At 16V input that's about 6% loss. Difficult to avoid, though, unless you use a latching relay (or some rare SPV1512 'cool switch').

SB1540 :

http://www.produktinfo.conrad.com/da..._DIO_de_en.pdf

The String Diodes are added in the primary circuit, they need higher voltages (string voltage Uoc), and must stand the Isc current of the string. You can parallel them to lower the through-current and the forward voltage to a better value. The loss is much less if you use higher voltage panels with an MPPT regulator too, it is the relation between the Ump and the forward voltage at Imp.