MPPT Charge Controller for LifePO4 Batteries

[Maine Sail]

Originally Posted by dennisail

I have been looking at controllers to charge a proposed lithium bank. Seems the good MPPT controllers are very expensive, huge, heavy and possibly not all that much better than PWM (well not as good as spending that extra money on one more panel).

Here is a $41 adjustable 30A PWM controller which is small and light. So you could easily buy 2 or 3 to power your panels, and having multiple controllers has its benefits anyway. The fact you can adjust it should mean it will work fine with lithium. It has a separate temp sensor which you could easily rig up to a variable resistor to disable it.

30A LCD Solar Battery Regulator Charge Discharge Controller 12V 24V CE Certify | eBay

I see a many cheap supposed MPPT controllers but I am not convinced they will work as desired.

Thoughts?

Please be VERY careful with any of the Chinese controllers on eBay. Many of them temp compensate inside the controller with no way to turn them off and some don't even declare they do this in the documentation.

My MPPT choices for Li:

Rogue MPPT 2024 or MPPT 3048
Genasun custom programmed - for small arrays or one controller per panel
MidNite KID - Due out this spring

Above 30A the MidNite 150 or Outbacks I like a lot.....

For PWM:

Morningstar ProStar45

The Rogue has some great tweaking ability for Li some of the best I have seen including the ability to completely turn off stages such as float etc. and also has an external programmable relay port to drive a myriad of items.......

[Matt Johnson]

We currently have a Bluesky 3024i, so with the $175 ipn-pro remote, we can set everything we need. The Rogue looks like a great system if starting from scratch.

Matt

[noelex 77]

Originally Posted by dennisail

Also, is a panel with a max power output of 12V and max panel voltage of 15V to low? The other option is max power output of 18V and max voltage of 22V. What will work better?

To work effectively the Vmp has to above the battery voltage. When charging the battery voltage will be well above 12v. The Vmp is quoted at a cell temperature of 25c. In practice the cell temp will be higher and the Vmp will be lower still.
The 12/15v would only be ok if you connected at least two in series to produce an effective 24/30v panel. This will need a a MPPT controller.


The 18/22v panel is the standard voltage for a panel suitable for a 12v battery. It can be used with or without an MPPT controller.

[dennisail]

Please be VERY careful with any of the Chinese controllers on eBay. Many of them temp compensate inside the controller with no way to turn them off and some don't even declare they do this in the documentation.

I looked for ages. The one I linked seem to tick all the boxes in that it is programmable and the temp compensation probe is remote, which would appear to lend itself to be disabled by a resistor.

[dennisail]

To work effectively the Vmp has to above the battery voltage. When charging the battery voltage will be well above 12v.

Yeah, figured that. Just wondered if the 12/15V panel would actually produce 13.5 volts more efficiently than a 18-22V panel. Lithium needs less voltage and I thought it might be closer to Vmp. But I guess with shade and heat etc, it might be too low in practice.

[noelex 77]

Yes as you say the charge voltages for lithium are lower, but not low enough for a 12/15v panel.

The charge current drops off very rapidly once the Vmp is exceeded as this typical I/V graph shows.

Vmp is at the peak of the knee where the kneecap would be. (For the panels you were considering this point would be 12v. Where the graph crosses the horizontal axis would be 15v (all at 25c) Also note how the voltages drop off with temperature (50c is not an unusual cell temp during the middle of the day in summer)

[dennisail]

Thanks. Do you have a graph like that for a 12-15V panel?

[noelex 77]

No sorry, but the shape will be very much the same, just scaled for the different voltage.
The graph I posted is for a typical 12v nominal panel ie close to the 18/22v panel you are considering (the amp scale will depend on the wattage)

[Hkalan]

Hello,

I have picked up a Morningstar TS-60 MPPT to test its settings for a lifePO4 bank in April.

With four 300w panels (1,200w) on the flybridge hardtop, the TS-60 so far has more adjustments then I thought.

I can customize every setting to fit any lithium bank as well as my current a Bank. I can connect it to my router and adjust as monitor on my computer.

As I will be spending thousands on a LifePO4 25.6v 400Ah bank, I would not nickel and dime about a controller or monitoring system.

If a person sells you a diamond ring for 10 cents, chances are you have a ring that is not worth a dime. Spend the money and get what you need.

A solar controller that can adjust and set everything to meet your needs, works better then one that is said to be designed for one type of battery. I live on my vessel, and need flexibility and amp handling to charge !

Alan

[dennisail]

Originally Posted by noelex 77

No sorry, but the shape will be very much the same, just scaled for the different voltage.
The graph I posted is for a typical 12v nominal panel ie close to the 18/22v panel you are considering (the amp scale will depend on the wattage)

That was what I am interested in seeing for the 12/15V. The scale of the 18/22V looks way too high until the panel hits 75deg. But I guess when the 12/15V panel hits 75deg voltage would be too low for charging, but without a graph its a guess.

[campr]

I've been following this thread with some interest.

I intend to use 4x250Wp panels to charge my 200-400Ah 12V Lipo bank (have still not decided on the size, partially due to the cost). So at peak times I am charging ~100A of power (absolute max).

I found this controller on the Australian Ebay site: Powertech 12V 24V 30A MPPT Solar Regulator Charge Controller Latest Model | eBay

You can download the manual from the site, and it seems that you can freely choose the bulk charge voltage and the float voltage, and even switch off the temperature compensation for the float voltage. Oh, and it's MPPT too.

I'm thinking of mounting 4 of these, that way I have one for each panel, which should increase efficiency and also provide some failure tolerance.

Bad idea, good idea?

[s/v Holiday]

Hi All,

Just an update from my original post.

I have since installed 800ah of LifePO4 batteries and have been running them for more than a year so far with very positive results.

I am about to add the solar and I have purchased 2760 watts, (8 Sunpower X21 345w panels)

I will be running them with 2 Midnite Solar Classic 150 MPPT controllers. The panels will be wired and fused using a Midnite Solar combiner box with 20A Breakers.

I am waiting on a welder to construct my new davits/Arch for the back of my catamaran to mount the panels. 6 of them will be on the arch and have the ability to tilt backwards and the other 2 will be on the hardtop.

I will post some pics and the results when I get it done. Hopefully in a month or so.

Anyone have any advise?

Wish me luck!

Cheers,
CJ

[s/v Holiday]

Originally Posted by campr

I've been following this thread with some interest.

I intend to use 4x250Wp panels to charge my 200-400Ah 12V Lipo bank (have still not decided on the size, partially due to the cost). So at peak times I am charging ~100A of power (absolute max).

I found this controller on the Australian Ebay site: Powertech 12V 24V 30A MPPT Solar Regulator Charge Controller Latest Model | eBay

You can download the manual from the site, and it seems that you can freely choose the bulk charge voltage and the float voltage, and even switch off the temperature compensation for the float voltage. Oh, and it's MPPT too.

I'm thinking of mounting 4 of these, that way I have one for each panel, which should increase efficiency and also provide some failure tolerance.

Bad idea, good idea?

Hi Campr,

Do you know if they will tai to each other? If not they might not charge at full potential.

I did a bunch of research on this and found that the 2 top controllers are the Midnite MPPT and the Outback ones. You could run all 4 panels on one controller.

These have also been proven to work well on a boat.

Cheers,

CJ

[dennisail]

Do you know if they will tai to each other? If not they might not charge at full potential.

Why would it matter if each was run separately? I would have thought this would have actually been better for redundancy and also each controller can run each panel to its own peak performance, say one is shaded etc.

[s/v Jedi]

I don't know anybody using a Powertech MPPT controller. Are they real or fake? who makes them? Any good references, reviews, tests? What efficiency factor do they have?

To me it sounds like cheap ones that don't work well if at all. Assume I would have seen them otherwise.