MPPT with voltage boost

vtmaps · June 2013

The question of whether one can charge a 24 volt system with a grid tie (Vmp≈ 30) panel comes up frequently on this forum. The answer given here is usually "no".

I have stumbled upon the web site of Genasun.com. They appear to make MPPT chargers with a voltage boost ability. I know nothing about them except what I see on their web site. I mention it here because it might be of interest to the members here. Has anyone here seen or heard of these controllers?

see: http://genasun.com/products-store/mppt-solar-charge-controllers

from their web site:

Most solar charge controllers move power from a higher voltage panel to a lower voltage battery bank. The GVB-series controllers, in contrast, pump electricity up hill. These controllers will take a standard 12V panel and boost the voltage to charge a 24V, 36V or 48V battery pack. In fact, the GVB's will work with almost any panel that's below your battery voltage. This makes finding a good panel easy: just make sure to stay below 8A panel current and 63 Volts (open circuit). Larger panels are cheaper per Watt than smaller panels, so using one large panel and a boost controller results in a significantly lower system cost than smaller panels in series with a conventional charge controller.

--vtMaps

BB. · June 2013

Re: MPPT with voltage boost

Genasun has posted here a few days ago:

genasun wrote: »

Cariboocoot,

Thanks for your comments. We are also disturbed by the number of fake "MPPT" controllers out there, and I don't blame your skepticism. Our controllers are designed and assembled in the US, and we set high standards for our products.

The GV-10 (along with the GV-4 and GV-5) is designed for 12V panel to 12V battery systems. These controllers were designed before GT panels became prevalent, and we don't recommend using GT panels with the GV-10. You're definitely right when you say that a larger MPPT controller that can handle GT panels (like the one you've described) will have much broader applications and will reach much, much larger markets.

Small MPPT controllers make sense in off-grid applications where size, weight, and performance matter: remote sensing, parking pay stations, street lights/signs, sail boats, RV's, military, golf carts, etc. In many cases, the extra power gained from using an MPPT controller in a 12V panel/12V battery configuration offsets the cost premium over a PWM controller.

Cheers,
Alexander

I have not seen anyone use them--But perhaps they can give provide some details to anyone that asks.

-Bill

Cariboocoot · June 2013

Re: MPPT with voltage boost

Genasun controllers have recently come up on the forum. In fact a representative of the company has joined as a member. So far no one here has used any of their products.

It has always been possible for a buck converter to function as a booster, and MidNite was going to implement this function. The limited market for this function typically has been sited as the reason why it wasn't done. After all, most installs will not use only one panel and if you've got two (or more) panels + a good MPPT charge controller the Voltage difference problem is solved.

When the Voltage goes up the current goes down, so the easiest thing to do is solve the low Voltage problem at the panel side and let the MPPT handle the current.

vtmaps · June 2013

Re: MPPT with voltage boost

BB. wrote: »

Genasun has posted here a few days ago

Oh, I forgot.... that was eight days ago! <sigh>

I can still remember being able to remember things for more than a week..:p
--vtMaps

BB. · June 2013

Re: MPPT with voltage boost

vtmaps wrote: »

Oh, I forgot.... that was eight days ago! <sigh> I can still remember being able to remember things for more than a week..:p
--vtMaps

Sounds like we have softened you up--About ready to be a moderator.

-Bill "been there, done that" B.

genasun · June 2013

Re: MPPT with voltage boost

The GV-Boost controller is a boost converter (step-up converter). It will allow you to charge a 24V battery with a grid tie panel (Vmp~30V), but be aware that it will probably not operate your panel at the maximum power point, since the specified Vmp is above the battery voltage. A 12V panel would be a better match in this case.

Boost controllers make the most sense in applications where you only want to use one panel to charge a higher voltage battery. The prime example of this is a golf cart, which typically has a 36V or 48V battery, and has room for only one panel on the roof. There aren't many panels out there with a high enough voltage to charge a 36V or 48V battery. The boost controller gives solar golf cart kit manufacturers flexibility to choose more commonly available, cost effective panels.

YehoshuaAgapao · June 2013

Re: MPPT with voltage boost

The Kyocera 315-320W 80-cell panels (NAWS sells these) may be able to charge a 24V battery bank with a single panel. Vmp is 39.8/40.1V (315W/320W) @ STC. 72-cell panels (Vmp 36V @ STC) may work if they are not used in hot desert AZ.

My solar panels run around 72V in the 110+ degree heat here in Phoenix AZ. 3 to a string, 60-cell (Vmp ~90V), a 20% voltage loss due to the heat. I am using #6 wire pre-combiner (most of wire length, through attic) and #2 post-combiner, running 2-4% voltage drop from solar panel to charge controller (combiner boxes in shady east side gable during hot part of day, 110-120 degrees; west gable vent frame gets to 150 degrees / 65.5C; roof 140 degrees / 60C during day; solar panels get to 150 degrees also).

96-Cell panels can be purchase directly from chinese dealers (48Vmp assummed). Probably can charge a 36-volt bank with a single panel in non-desert climates. Fits 150V MPPT controllers in strings of 2 (80-cell has too much voltage loss in the heat for strings of 2 and voltage is too high in strings of 3).

MPPT with voltage boost

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