Author Topic: Lithium Solar-BMS & Power Point Tracking Thermal Controller Kickstarter...  (Read 2043 times)

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DanG

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 This gentleman has completed two successful Kickstarter releases before & and his next batch has just been offeredÖ

Iím sharing them here for your thoughts or comments (I'm pledging for a couple of the BMS modules).

His latest project introduces a Power Point Tracking Thermal Controller for thermal mass storage, logic control of a matrix of fixed resistance loads to best match whatever the PV output happens to be at any given time.  Oh yeah, 450 Amps worth of solar into resistance heat! --- "DMPPT450 as the name implies will support a max of 450A STC current so a total of 14kW of PV panels can be connected.  Panels need to be the 60 cell type."  -- WOW.  It's kind of dense reading his info sheets, a marketing presentation with light technical stuff...

Anyhow, Iíve been waiting for half of forever for his latest solar charger-BMS modules to become available with Wi-Fi & phone aps & logging & alarms etc. built in that are just pure neatness, he is offering them in 40A and 120A flavors this time.

I see a few limitations on his charger/SBMS stuff, one is a mandatory 6~ meter total length on input leads of 16mm≤ copper conductor to eliminate possibility of LiFePo inrush surge burning out his circuit, so having a 48V system to reduce losses would be best.  So yes, he is warning that cable length is a normal required resistance, do not heavy up on those cables.  Also he wants no fuse or circuit breaker before his device to keep chances of spike/surge at a minimum which is different approach too if* Iíve read his notes correctly.

https://www.kickstarter.com/projects/electrodacus/digital-mppt-and-solar-bms-for-a-net-zero-energy-h
 

OperaHouse

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It's how every engineer would like to design things, in a carefully controlled environment. You pretty much need to start with a virgin system and design the house around it. Funny how he wants to heat with MPPT, but regards it as useless when charging batteries.  If you can't get through the lit, MPPT is achieved switching in and out resistive elements of a central heated core.  The old 1, 2, 4, 8, 16 binary way.  In this example you get 32 possible currents.  The heating elements need to be pretty close tolerance to do that.  Suspect that 16 is really the practical upper limit and that is probably sufficient anyway.  Not sure what mixing the MPPT and PWM do to the overall efficiency.

The nice thing about this is the heaters are on or off and no storage in capacitors are needed to store energy like in a typical MPPT controller.  I'll be the first to admit that can be a long term problem if not well designed.  Those of you that have followed my posts know I like to PWM heaters.  The reason is many things only have a single element, like a water tank, and the only way to control current is with PWM.  That also allows you to do zone heating quite easily if you wish to concentrate heat in just a few areas.  Want everyone to be aware that if you have a mish mash of heating elements it will be difficult to configure without using multiple boards.

Hey, it's all in the software.  This new product is nothing more than a relay board.  If you buy a few SSR and a NANO, you can have the same system short of fancy screens, data logging and wifi.  I think a lot of PV energy is wasted and all for improvements.  I haven't seen much interest here in PV heating.  He has some interesting ideas and a lot of energy. What he has is only a part of a heating system from what I can tell.  I don't think he has a full understanding of the industry.  I wish him luck.  It is going to be a hard sell.  He has trouble getting across the main talking points.

joestue

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I believe i suggested the 1,2,4,8,16 resistor method several years ago.

you can use software to adjust for the non ideal resistors and pwm the lowest resistor, or you can add hysteresis and just ignore the error.

its unclear to me if his mention of mppt refers to pwm or a legit mppt involving a buck, boost, or some other voltage transformation.

Funny how he wants to heat with MPPT, but regards it as useless when charging batteries.

DanG

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I see weather induced solar output variations being matched against proportional resistance load chunks so technically isn't it multiple power point tracking? Heh.

Anyway - its the SMBS that is the draw for me, I missed the 60 & 100A versions and now he's only offering 40A and 120A.

OperaHouse

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He is matching panel to resistance.  I'm not going to quibble over technicalities.  I see youtube people directly connecting panels directly to heaters and think that is fine.  It is terrible performance.  Having some simple software that switches in just three resistors, not even in a binary fashion gets you a lot of performance improvement.  It is just not a complete heating system and it will take a lot to make it one. I think it is just very limited in how it can be implemented and he is skating over issues.  Looking over comments of people who bought the BMS it seems like some didn't have a clear idea of what they were buying. Read carefully.

I'll be first to admit I don't know anything about lithium. If I had any interest I would learn.  I have learned from Chinese designs that you can get away with almost anything a lot of the time and for quite a while.  There are people that have serious issues with how he is charging the batteries. I don't know, but think it merits further investigation. 

He is always saying panels are so cheap it doesn't matter.  Interesting stuff, but he gives me an uncomfortable feeling and don't see that maturity of design. Can't really comment further.

OperaHouse

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electrodacus provided a link to his temporary heating system. Interesting photos.

https://plus.google.com/+DacianTodea/posts/VXbijJHXYmT

That's the way I built my system too.  Now I don't feel bad.