Why no step up charge controllers? Any reason not to use step up into a charge controller?

[dtawom]

So I'll try to keep this as short as I can. I have an 900w 1500va 36v (internal battery config) that I have turned into a LiOn portable power station using 4 recycled 36v hoverboard batteries. I've tied in a charge controller https://www.amazon.com/gp/product/B073PR56R9/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1 with two 12v solar panels for a friend that was off grid and it seemed to work fine. She could charge the batteries from here generator through the UPS ac power or the solar panels using this step up charge controller.

Well now I'm trying to do something similar for myself using a 12v portable solar panel setup to do a booth at the fair, but I'm unable to find any step up charge controllers like the one previously linked. So I'm wondering if there is any harm in using these panels:

https://www.amazon.com/gp/product/B08LKXQTC9/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

With this step up converter:

https://www.amazon.com/gp/product/B07N6BJWXH/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Which then ties into a standard charge controller like this:

https://www.amazon.com/Controller-Lithium-Lead-Acid-Battery-Regulator/dp/B087BC9X4S/ref=sr_1_3?crid=3X3S6J93UAPG&keywords=48v%2Bcharge%2Bcontroller&qid=1652493804&sprefix=48v%2Bcharge%2Bcontrolle%2Caps%2C210&sr=8-3&th=1

Which then ties into my 36v hoverboard batteries.
So basically I'd be going from 18v on the panels, through the step up controller to 48v, then into the charge controller to step down charge the 36v hoverboard packs.

Thoughts or any reason this won't work?

 

[rmaddy]

Why not use a "normal" MPPT solar charge controller that works with a 36V battery bank? Most SCCs that can do 24V and 48V also do 36V (though some my require manual setting for 36V versus autodetect).

I must be missing something since I see no reason for anything other than a regular MPPT SCC with sufficient panels in series to get the panel voltage over 40V.

 

[Don B. Cilly]

Well, 12V panels, one would need at least three to get a decent charge on 36V.
Apparently this controller has a built-in step-up, so It might be a good solution... but it would also probably work with a separate one.
.

 

[Rednecktek]

In a similar vein, if a MPPT controller is just a DC-DC converter to go from high incoming DC to low outgoing DC, is there any reason (besides just not being programmed to do it) that a controller couldn't do the other direction and take lower DC and convert it to higher DC output with lower amps? Like taking a 20v panel at 5a and kicking it up to 28v at 3.5a?

 

[time2roll]

Voltage is stepped up by connecting the solar panels in series. Many MPPT can take in 100 to 150 volts and convert down to the 36 volts needed.

 

[Don B. Cilly]

Well, the one I linked supposedly does just that. It has a step-up converter.
Charge controllers usually don't need those, so they don't have them. They're just meant to have higher input voltage than output.
In the OP's case, he wants to use a single 12V panel, which will give 18V at best, to charge a 36V battery, so he needs one.

An MPPT controller is a PWM controller, it just has an added algorithm to "track" the best voltage/current combination to charge.
It still needs a bit of "headroom" (higher voltage at input than at output) - usually more than a simple PWM one to work efficiently.

[EDIT] Here is a funny story to explain the concept :·)
-

 

[Rednecktek]

So it's not so much a DC-DC converter as a smarter, faster, stronger switch. Gotcha! Thank you Don!

 

[rin67630]

With this step up converter:
https://www.amazon.com/gp/product/B07N6BJWXH/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

This will NOT work.
This step-up converter has an own control loop trying to maintain a constant output voltage, and that lopp will jeopardize the MPPT function of the SCC.
The green step up converter is the only viable solution.

 

[rin67630]

In a similar vein, if a MPPT controller is just a DC-DC converter to go from high incoming DC to low outgoing DC, is there any reason (besides just not being programmed to do it) that a controller couldn't do the other direction and take lower DC and convert it to higher DC output with lower amps? Like taking a 20v panel at 5a and kicking it up to 28v at 3.5a?

No the green step-up MPPT Converter is perfect for that job.
I just am no very fond of the allegated 100W 18V foldable panel.
It has only 32 cells. That will produce real 18V OC and 15V MPPT under optimum conditions only. IMHO the 100W are VERY optimistic.

 

[pullin_gs]

I use this "step-up" (Boosting is the actual term) MPPT charge controller for my ebikes .
I have it hooked to a pair of $75 100w panels. Output charge voltage is indeed more than panel voltage.
It has worked flawlessly for over two years.
Here is my solar charge station build report (only one panel at the time):

Build Report: MPPT Solar Charging Station for Etrike

Works great. Charges 10S6P 18AH pack at rate of 2.5amps in full sun. I use it for both my Etrikes. Anchored 100W panel to south-facing side of garage. Grounded panel to steel pipe on gas meter using 12awg solid copper. Drilled 1/2" hole through wall for 12awg solid copper wire to charge...

endless-sphere.com

https://www.amazon.com/Charge-Controller-Battery-Regulator-24V-72V/dp/B08K3FVCKG/ref=sr_1_16?crid=2VVWTKWWRR2UT&keywords=mppt+boosting&qid=1653347420&sprefix=mppt+bosting%2Caps%2C102&sr=8-16

 

[squowse]

There are step up MPPT. You can find them on Aliexpress, eBay etc

 

[Phineas]

Well, 12V panels, one would need at least three to get a decent charge on 36V.
Apparently this controller has a built-in step-up, so It might be a good solution... but it would also probably work with a separate one.
.

That one is quite overpriced for a 10A capacity.

 

[Phineas]

I use this "step-up" (Boosting is the actual term) MPPT charge controller for my ebikes .
I have it hooked to a pair of $75 100w panels. Output charge voltage is indeed more than panel voltage.
It has worked flawlessly for over two years.
Here is my solar charge station build report (only one panel at the time):

Build Report: MPPT Solar Charging Station for Etrike

Works great. Charges 10S6P 18AH pack at rate of 2.5amps in full sun. I use it for both my Etrikes. Anchored 100W panel to south-facing side of garage. Grounded panel to steel pipe on gas meter using 12awg solid copper. Drilled 1/2" hole through wall for 12awg solid copper wire to charge...

endless-sphere.com

https://www.amazon.com/Charge-Controller-Battery-Regulator-24V-72V/dp/B08K3FVCKG/ref=sr_1_16?crid=2VVWTKWWRR2UT&keywords=mppt+boosting&qid=1653347420&sprefix=mppt+bosting%2Caps%2C102&sr=8-16

I bought two of that step-up MPPT from ebay. Under $40 ea.

 

[pullin_gs]

I bought two of that step-up MPPT from ebay. Under $40 ea.

Better deals to be had?......I paid $33 in 2019. There is a 600 watt version also?

 

[dtawom]

Thanks for all the feedback. My whole problem was terminology. I've used step-up controllers before and I assumed solar charge controllers would use the same terminology, but as soon as I started searching for boost solar charge controllers tons of options came up.