MMPT vrs PWM

[larrylwill]

I bought this controller off Amazon a couple years ago for my RV with 280A of solar and 280A Lifepo4 batteries.
Its working fine but recently there is speculation that its a PWM, since there is no inductors in it. So I thought if I went to a real MMPT one I might gain a couple more amps. I pulled into the sun and was getting about 8 amps to the batteries, which are almost full. I then hooked up a real MMPT controller and got the same current. Do you think its because the battery is almost full or is it not worth the trouble to change?

WERCHTAY 60A MPPT Solar Charge Controller 12v/24v Current Auto Focus MPPT Tracking Charge with LCD​

 

[Mirlen]

280 AMPS of solar or watts? 280Ah of batteries? If the batteries are full unless you have a decent load then the 'charge' rate is going to be low. That Werchtay is very likely a PWM controller. What MPPT charge controller are you using? What voltage batteries? What are the ratings on the panels from the label on the back? PWM works OK when the panel voltage coming in is close to your battery voltage as it won't convert any extra voltage to increased current like an MPPT will, so usually you're going to run panels in parallel to keep voltage close to the battery for 12v systems. If you ran the panels in series then you would basically waste the extra voltage and it'd get thrown out, but again it all depends on the specs of your batteries and the panels.

 

[larrylwill]

Yes, 280W of solar and 280A of batterys. The MMPT is a SUNTHYSIS 30A. The panels are in parallel. 2 are 100w Monocrystalline 1 is an older 80w Polycrystalline.

 

[Mirlen]

Parallel into 3 to 1 combiners? Mixing panels of varying Voc/Isc ratings can greatly impact performance, heres one of many videos on this:

Having pictures of the rear labels is handy to have on hand for planning changes etc, always good to keep that info handy.

 

[larrylwill]

I cant get it now I broke my foot a couple days ago. I watched it. Yes I get it but Im still better off with that odd panel than only 200W. If I can fit a bigger pannel in its place since its bigger than the 100w ones I will upgrade later.
thanks

 

[Rednecktek]

280w / 14v = 20a so yeah if you're only seeing 8a then your batteries are either mostly full OR there's something wrong with your panel setup.

When they're full any measurement of performance is pointless because the load just isn't there.

Without knowing what kind of panels you have and how it's tough to guess.

Yes, that Sunthsys is a proper MPPT and will perform better than the lying PWM, but there may be optimizations needed to the panels.

 

[larrylwill]

I have seen 17 amps on ocassion. Now its been in the garage only powering a phone. Maybe tomorrow Ill back it out and power on the AC for a load to see how each controller does. Howerever 1-2 amps more to change to a MMPT I dont think its worth it. I bought a 20A Sunthsys by mistake then ordered the 30A from Amazon. Both have different firmwear and neither can connect to my phone with blutooth although the phone sees it and gives me a code, it never finds it. I have been in tough with CS and they are very helpful.