Best small/light-duty MPPT controller?

[Herbie]

I've done a little searching, but since the tech is moving pretty fast, any thread older than a couple of years probably doesn't have up-to-date info on the current products out there, so I thought I'd post up looking for help. Can anyone recommend a smaller/lighter-duty MPPT controller that supports ~10A or less?

I'm currently using a Solar Cynergy 60w panel and a 1st gen Morningstar SS-6 PWM controller. I'm having pretty good success, especially since my panel is currently mounted such that I can either use it on my pop-top van roof at a nice angle (and park facing North), or pull it out of the rack and re-position it on the ground for good exposure, etc.

However, due to mounting issues, I'll probably need to move the panel farther aft on my roof, which will make it inaccessible for "off-roof" placement (unless I start carrying a ladder!) The upside is that with the change in mounting, I should be able to add a 2nd 60w panel. When this happens, I'll need to replace the charge controller, so I'm looking at MPPT models.

Here's the thing - most of the stuff out there seems like serious overkill. If wire my panel in series, which seems like the better choice, I'll only be running 3.55A max. (That panel's Imp @ 17.0v Vmp). Even if I went parallel, that's still less than 8A. The smallest "name brand" MPPT controller I've seen supports 20A.

Given the 17.0v Vmp, I suspect I'd see some extra efficiency even just sticking with a single panel, which would be nice as well. But again, $130-$150 for a 20A+ Renogy seems like overkill, especially since I'll never be able to put that much solar on my van. I see a lot of Chinese import/knockoff stuff that's cheaper/lower-spec, but it's hard to know what you're getting there.

Thanks all!

 

[Herbie]

For completeness: Battery is Odyssey PC-2150 AGM. Unlikely to change away from AGM batteries, if that's a factor in this discussion.

 

[Bear in NM]

Herbie,

Nice looking van. I just got into the van game a month ago.

I went through this exercise with my cargo trailer last spring/summer. I could not find a lot of good brand "lesser" size mppt's. I settled on a Midnight solar controller, but my trailer has more mounting room than I would guess you have in your van. I spent about 350 dollars on my two batteries, and could not bring myself to gamble and skimp on a charge controller. I am betting your Odyssey was about a hundred more than my batteries. I have all of my components on Anderson plugs, and a couple of volt/amp meters that I can plug in-line in various spots to confirm what my solar and controller are doing. I have the Midnight mppt and two Morningstar pwms, and check those. If I had an Odyssey battery, an "unknown" controller would sure give me pause, as you noted.

I am interested in what other think about your question. I completed my panel installation on my new to me van last weekend, but am going to run my Morningstar Sunsaver Duo pwm. I thought about moving my Midnight from my trailer, but it is a bit large.

Craig

 

[Rando]

Victron MPPT 75/10:

Regular version ($80): http://shop.pkys.com/Victron-Energy-MPPT-7510-Solar-Charge-Controller_p_4311.html

Bluetooth version ($110 - worth the extra $ in my opinions anyway): http://shop.pkys.com/Victron-Energy...-Charge-Controller-with-Bluetooth_p_7180.html

These are small, work well and are completely bomb-proof.

 

[Rando]

PS, if you are worried about taking good care of your expensive battery, you could buy the 75/15 model of this charger and wire your house loads through the 'load' terminals on the charge controller, which will give you a programmable low voltage disconnect to shut everything down when the battery gets too low. On the bluetooth model all the set points and voltages are configurable through an excellent iOS/Android app and you can monitor system performance in real time as well.

 

[pdavitt]

Victron MPPT 75/10:

Regular version ($80): http://shop.pkys.com/Victron-Energy-MPPT-7510-Solar-Charge-Controller_p_4311.html

Bluetooth version ($110 - worth the extra $ in my opinions anyway): http://shop.pkys.com/Victron-Energy...-Charge-Controller-with-Bluetooth_p_7180.html

These are small, work well and are completely bomb-proof.

I second Rando's suggestion, Victron makes good stuff. Be aware that the amperage ratings for Charge Controllers are mainly for the output to the battery. So the amperage has to be recalculated for 12-14 volts vs 17-20. Which means that you will have a higher amperage going to the battery than incoming from the solar panels.

Pat

 

[Herbie]

Thanks Rando, that looks like a good choice that's a bit closer to the "sweet spot" for small solar needs.

 

[jonyjoe101]

just make sure you connect your panels in series to increase the voltage. Mppt requires the high voltage panels to give you a increase performance. Mppt won't give you any increase amps from one panel, but it will at least work just as good as your pwm controller. I always heard that mppt only works with large panels but I had to try it for myself. Below is my results.

120 watt panel (21 volt) with mppt = 6 amps
same panel with pwm = 6 amps

240 watt panel (36 volt) with mppt = 12 amps
same panel with pwm = 6 amps

I use the ecoworthy 20 amp mppt (cost 100 dollars) with my 240 panel I get about 12 amps with my 102 ah agm, with my 11.1 volt 94ah lithium I get up to 15 amps of charge power.
This controller has an LCD screen that shows voltage/amps going into battery, and everything (bulk/float voltage) is adjustable from the 4 buttons on the controller. The victron has no LCD screen and you need a add-on doongle to adjust the voltage. As far as quality, my ecoworthy has been running non-stop 24/7 for almost 5 years.

 

[Rando]

The 'must wire in series for MPPT' idea is a common misconception. You will get a benefit from MPPT regardless of how you wire the panels, slightly more if they are in series, but not much more. If you have a portable and fixed panel, you want to use them in parallel - so you can disconnect the portable and still get power from the fixed panel.

For the example here (2 panels, each 3.5A at 17V), in parallel you will get 7A at 17V. - with MPPT this will give you 120W @ ~13.7V = 8.7A into your batteries. With PWM you will get ~7A into your batteries, so you will get more power with MPPT. The are some second order effects with temperature and wire losses, but in general the math above is fairly close to the reality.

 

[plh]

I have the Eco worthy 20 amp mppt as well on 2x 125w panels. Works fantastic.

 

[devero4]

I have to third what Rando said, as I myself have just acquired the Victron 75/10 BT smart controller and so far have been very pleased. The price has come down a little on these since they came out which is what allowed me to buy it. Using it with my 55Ah Marine/RV AGM solar generator. I was using a $20 Moohoo/Allpowers PWM from Amazon which was okay, but the Victron allows you to see almost everything you need - I would buy it again.

 

[Bbasso]

I too have the Eco worthy 20 amp mppt as well on 2x 100w panels. Works fantastic for two years, but I'm thinking about upgrading to 400wt total and the 100/30 Victron with bt hopefully by winter.

(Almost a quote lol)