Best small MPPT?

[Jon Hacking]

We're about to install 3 new 400W 72-cell rigid panels (only US$200 each here in the Philippines, with a 30-year performance & workmanship guarantee). We'll probably connect each to it's own MPPT, so I'd like to know the best small MPPT. Requirements include:

• Able to handle 400W at 12v output
• Able to handle 50v open circuit input
• Ideally, can connect to a shunt to measure current into the battery
• At least 1 fully programmable charge profile, as we're charging 300Ah of LiFePO4 (12v)
• Good efficiency, & good MPP Tracking
• Remote display of current & voltage, as the controllers will be mounted near the batteries & difficult to get to

Also, please indicate WHY you think it's the best. I'm an EE & interested in details. I'm not interested in "this is what we've used & we like it..."

History: We've been running 4x120W 36-cell panels (in 2 series strings, wired in parallel, so 36vMPP) through a Blue Sky Energy SB50 since 2001. It's one of the very few MPPTs that monitors current into the battery, but I'm not sure that their new models still do. Panels will be mounted above the davits, so minimal shading issues. This may have been discussed before, & my apologies if I've missed it. TIA!

[john61ct]

The shunt based measurement of bank acceptance does not need to be performed by the SC itself.

A Battery Monitor that is more accurate at guesstimating bank SoC is IMO the better tool.

The latter can cut off the former's connection if there isn't a more elegant signaling scheme in common.

Or you just calibrate AHT on the SC so that "most cycles" your endAmps goal is reached before dropping to Float,

getting there every cycle is not required for great longevity.

I would start out looking at Victron's systems, SmartSolar 100/30 per panel, BMV-712 per bank, perhaps making use of its relay, as a failsafe to prevent too long AHT

what chemistry is the bank?

And Color Control GX, Venus or your own MCU based system using their (basically) open protocols as a central system logger / controller.

The Victron user forums are well supported, sometimes their founding engineer stepping in to participate when needed.

[john61ct]

Bogart Trimetric is a great BM, and each can control 2x SCs directly

but being PWM based, maybe not the best choice for higher-voltage panels

Well worth investigating though

[john61ct]

MidNite's Whizbang Jr, coupled with their Classic or KID controllers, also does endAmps charge termination

[john61ct]

You already know about BlueSky when used with their IPN-Remote / BMS.

[john61ct]

The FOSS based Electrodacus "Solar BMS" from Dacian Todea
electrodacus@gmail.com

is really worth checking out, for design ideas on your own central controller system if nothing else.

Pretty rigid about overall system configuration and panels used though.

AFAIK that's pretty much it on the market these days.

But as stated many ways to skin the cat if you're willing to get creative.

Please do keep us apprised as to how you proceed, few members are interested in impkementing such a fine level of charge control.

[smac999]

400w is not a small controller...

the victron smart 100/30 would just be on the edge. all data via bluetooth
solar amps, etc. . including hisotry tracking

[Dsanduril]

Posting mostly so I see what responses you get, as I think you’re after the same unicorn I’d like to find.

Since every thread here and elsewhere recommends a single MPPT controller per panel I think the market is ripe for a “dumb” MPPT module that handles the solar tracking and DC-DC conversion but knows nothing about the batteries. Multiple modules would be combined with a single battery monitor/charge controller that tells the MPPT modules what to do, tracks Amps/Volts in/out and provides a single place to program charging profiles, etc.

Any patent attorneys out there?

[Jon Hacking]

Thanks for all this. The Victron certainly gets a lot of airtime & kudos, but ... I look at my current MPPT display daily, so it's nice to have a dedicated display on the wall, even if it only has a blinking LED (indicating state) & a number next to it for amps. I can see that an app on a phone could be cheaper & more flexible, but is it as easy to use? It's hard to beat glancing up at the wall... The integration of the Victrons would be more compelling if I had any of their other stuff.

[Jon Hacking]

Originally Posted by Dsanduril

Posting mostly so I see what responses you get, as I think you’re after the same unicorn I’d like to find.

Since every thread here and elsewhere recommends a single MPPT controller per panel I think the market is ripe for a “dumb” MPPT module that handles the solar tracking and DC-DC conversion but knows nothing about the batteries. Multiple modules would be combined with a single battery monitor/charge controller that tells the MPPT modules what to do, tracks Amps/Volts in/out and provides a single place to program charging profiles, etc.

Any patent attorneys out there?

You're not the first to propose this, & I agree that the time is ripe. The guy who designed the Very Smart (alternator) Regulator (VSR) & the WakeSpeed WS500 was thinking along these lines, connecting everything up by CAN-bus, since the VSR (& WS500) already know much of what the MPPT would need (although he was proposing a dedicated BMS as well, as you propose). I'd be up for it. Are you an EE/designer? He'd love some help, as he's pretty tied up with other projects, & his previous partner has gone off on another tangent.

[Dsanduril]

Yes, in my head I see the same “controller” also managing the alternator (through a “dumb” regulator module) and pretty much any other charging source. You need a new module for each charge source (fuel cell, hydro generator...) but only have to set up one charge profile and only have one device having to evaluate endAmps, endVolts, whatever other charging criteria you have. That device then distributes the charge needs to the available modules. I even see it being able to manage dump loads being discussed in another thread here, although that is not a requirement for me, more a nice to have.

I’m an automation/controls guy - I could program this in my sleep in a PLC or similar (or a Pi or Arduino), but the cost would be too high and I couldn’t deal with the hardware/circuit design. Getting it down to a custom hardware board is the only way I see it being market viable and I don’t have those skills.

[john61ct]

Intelligent chips are cheap, eliminating redundancy won't save much money.

Self-contained SCs that get successively dumber as they get aggregated, centrally coordinated simplifies and streamlines the product line.

I can only think of small incremental changes to Victron's design strategy.

Without their making the SC price proportiinal to V/A capacity the 1:1 idea would never have gotten practical.

Look at Bogart Trimetric + 2x SC-2030 for a solid design too, just not as flexible and PWM so low volt panels only.

[mikedefieslife]

Originally Posted by Jon Hacking

Thanks for all this. The Victron certainly gets a lot of airtime & kudos, but ... I look at my current MPPT display daily, so it's nice to have a dedicated display on the wall, even if it only has a blinking LED (indicating state) & a number next to it for amps. I can see that an app on a phone could be cheaper & more flexible, but is it as easy to use? It's hard to beat glancing up at the wall... The integration of the Victrons would be more compelling if I had any of their other stuff.

The Victron MPPTs do a job but there are far from the best IMO.

Some of the drawbacks are, if you use one controller per panel you have to bluetooth into each controller individually to see the data. Since they are networked why can't Victron just make all the data available at once?

The screws that hold the wires into the controllers are only zinc coated so you need to be super careful of any humidity.

The controllers will only start with input voltages 5v higher than the battery, but will continue to run if the voltage is 1v higher. That can be a pain for people running smaller panels in parallel, or even in series when one panel isn't shaded, but isn't facing the sun.

My pet hate is the position of the fuses. Very difficult to get to and to re-insert as there is no guidance there to help you ease it in. The fuse goes directly into two prongs on the PCB.

[noelex 77]

Originally Posted by mikedefieslife

The controllers will only start with input voltages 5v higher than the battery, but will continue to run if the voltage is 1v higher. That can be a pain for people running smaller panels in parallel, or even in series when one panel isn't shaded, but isn't facing the sun.

Mike, what you are saying is accurate. I thought this may prove to be a problem for people running “12v” panels in parallel (I cannot see it happening with any other configuration), at least for those boats with wind charging (raising the battery voltage overnight) and in hotter climates. However, I have never seen a report of a Victron controller starting late. Have you seen any examples, and if so can you give any more details?

[a64pilot]

Originally Posted by noelex 77

Mike, what you are saying is accurate. I thought this may prove to be a problem for people running “12v” panels in parallel (I cannot see it happening with any other configuration), at least for those boats with wind charging (raising the battery voltage overnight) and in hotter climates. However, I have never seen a report of a Victron controller starting late. Have you seen any examples, and if so can you give any more details?

Unless people had other controllers also on board to compare with, and were the type to watch closely, odds are they wouldn’t notice.
Cause they have to be starting late.
However was much power actually available earlier than when they started? I’d think not, so even if they are late, you didn’t miss much