100W Panel with PWM or MPPT & ACR to start motor

[dave777]

There are a some generic $20 PWM solar charge controllers and $100 MPPT models to chose from. Both have "smart" charging capability.

Currently we have one old 100W panel, but its controller is a tiny unbranded cube with one led for charge and one for full.

I'm going to replace our old diode based combiner with an ACR relay (probably Yandini).

I would connect the new solar controller to the house bank.

Any thoughts on a "newer" PWM controller on an older panel? Don't know if getting a better (more money too) MPPT is worth it. Also want to be sure Solar would play nice with an ACR relay.

Should the ACR be put in permanent OFF while on shore power if you've got a multi-bank smart charger?

[Capt.Don]

I have an old 70 watt panel that I've been experimenting with. I ended up going with a mid-priced 10 Amp PWM controller that supports battery selection (I have AGMs), Renogy Viewstar. Many of the cheap eBay controllers don't have the selection options for different types of batteries and charge voltages etc. I didn't want some cheapo controller to cook my batteries.

The 70 watt panel puts out about 4 amps (at least with my testing so far), so the 10 amp controller should support about 2 of these panels. It is maddening the dozens of $5 controllers on eBay. A common recommendation on CF is to go with a name-brand controller. Renogy stands behind their products and reviews are generally favorable. I gave up looking for a deal and just bought their controller.

I'm using the 70 watt panel as an experiment, to eventually buy panel(s) that will fit on my bimini. At this point, I think 2 50 watt panels would fit, so I can use the controller, cabling, .... Will continue experimenting on the boat this spring/summer and eventually install a couple solar panels.

Good luck,
Don

[Panope]

I am using a Morningstar ProStar 15amp PWM controller and a single, 100 watt panel. Not exactly inexpensive, put you do get a digital display of Volts and Amps.

Not sure if it is considered to be "smart", but it does not seem to over-charge the batteries. I only add water once a year and even then, only a dribble is needed (Note: I am not a liveaboard and the controller is turned off about half the time). Batteries are 4 years old and going strong. Never been plugged in to shore power.

Steve

[donradcliffe]

I've been using the Renogy pwm controller that came with their 100 watt panel for 3 years to charge an AGM battery. I'm happy with the results. The MPPT controllers aren't worth the extra money.

[pcmm]

Solar panels aren't very effecient to start with so you want to squeeze as much out of them as you can. an inexpensive MPPT controller will only cost you around $100 anyway so why not get the extra 20% out of your panels?? PWM controllers are just a waste of money these days.

for the ACR I wouldn't wory about it. when you are charging with the shore power charger, its going to see the elevelated voltage on both banks and likely not connect them. Even if it did connect the banks, theres no harm as the charger will just see them as one load. alternatively you could just connect up the shore charger to the house bank and let the ACR control when the starter bank gets charged.

[thudbranch]

If you can't keep your panel fully in the sun (most likely the case on a sailboat) you may want to spend the extra for a MPPT controller. I just purchased a Genasun GV-10 Lead-Acid and GV-10 Lithium MPPT Solar Charge Controller after a lot of research to go with my 100watt panel. MPPT controllers can make optimum use of a partially covered panel by raising the voltage and reducing the amps for optimum solar conversion and power produced by the panel at that moment in time. It is one of the very few marine grade controllers around at less than $250. My controller was $110 and comes with a 5yr warranty. All the PWM controllers I found under $200 were not at all water proof. I will update this post once I test the Genasun in the next month in the rainy-cloudy season of my home in the Pacific NW.

[pcmm]

Originally Posted by thudbranch

If you can't keep your panel fully in the sun (most likely the case on a sailboat) you may want to spend the extra for a MPPT controller. I just purchased a Genasun GV-10 Lead-Acid and GV-10 Lithium MPPT Solar Charge Controller after a lot of research to go with my 100watt panel. MPPT controllers can make optimum use of a partially covered panel by raising the voltage and reducing the amps for optimum solar conversion and power produced by the panel at that moment in time. It is one of the very few marine grade controllers around at less than $250. My controller was $110 and comes with a 5yr warranty. All the PWM controllers I found under $200 were not at all water proof. I will update this post once I test the Genasun in the next month in the rainy-cloudy season of my home in the Pacific NW.

I would add, Buy a larger controller than the panel. if you have 100watts now, you'll want more later so buy a controller thats good for at least double what you have now!

[roland stockham]

Depends mostly on the panel voltage. If the panel produces 15v and the battery is at 13.8 best you can gain is 1.2v, less than 10%. If however it is a 28v panel you can potentially get double the power from a mppt controller the a pwm. At least that's my reading but I am a novice with solar, about to install my first panel.

[mitiempo]

Originally Posted by donradcliffe

I've been using the Renogy pwm controller that came with their 100 watt panel for 3 years to charge an AGM battery. I'm happy with the results. The MPPT controllers aren't worth the extra money.

If you want the most out of your panels MPPT is the winner. Here is a real world test over 7 days - MPPT had a gain of 20.8% over PWM.
MPPT vs. PWM Controllers Photo Gallery by Compass Marine How To at pbase.com

[mitiempo]

Originally Posted by pcmm

for the ACR I wouldn't wory about it. when you are charging with the shore power charger, its going to see the elevelated voltage on both banks and likely not connect them. Even if it did connect the banks, theres no harm as the charger will just see them as one load. alternatively you could just connect up the shore charger to the house bank and let the ACR control when the starter bank gets charged.

I agree. When I install an ACR all charge sources go to the house bank only. The ACR takes care of the little current the start battery needs.

[mitiempo]

Originally Posted by roland stockham

Depends mostly on the panel voltage. If the panel produces 15v and the battery is at 13.8 best you can gain is 1.2v, less than 10%. If however it is a 28v panel you can potentially get double the power from a mppt controller the a pwm. At least that's my reading but I am a novice with solar, about to install my first panel.

Most nominal 12 volt panels have a voltage of about 18 in full sun. This will result in a gain with MPPT. Higher voltage panels need MPPT as very few PWM controllers will accept their higher voltage.

Read the test I linked to in a previous post.

[TheThunderbird]

I prefer 3 PWM on as many independent panels, than the best MPPT with all panels in series.

And, test is for lithium batteries, a rarity still..

[mitiempo]

Originally Posted by TheThunderbird

I prefer 3 PWM on as many independent panels, than the best MPPT with all panels in series.

And, test is for lithium batteries, a rarity still..

The test showed output - MPPT vs PWM. The type of battery is not important.

Series on a sailboat is not a good idea with shading. My preference is separate MPPT controllers for each panel. Victron 75/15 used on many systems.

[TheThunderbird]

Sir, battery type makes a difference, as Maine sail stresses up, in so far the bulk phase, where MPPT has a clear advantage is on up till 99,5% of SOC.

Given the extra cost of MPPT, having one for each and every panel makes it uneconomic vs a 120% of installed panels under PWM control.

Understanding (what was written) is more important than being right. Surely I am not .. However I don't buy easily any conclusions from what is found.

MPPT is good when the input voltage must be greatly adapted to the charging voltage. Buying 32 or 36 cell panels (monocrystalline) is far more important than the MPPT/PWM dispute

Regards

[mitiempo]

If the bank large relative to the solar array, as with many cruisers, the MPPT controller will remain in bulk far longer than a shore power charger or alternator will. This is where the gains are made. MPPT offers no advantage in absorption which in a large bank will be only in the last part of charging.