Lets Talk Charge Controllers

[o1marc]

So I have a 2450w solar array and need a MPPT to match. Any recommendations on compatible units.

Looking at this one, but open to options.
https://www.ebay.com/itm/Renogy-Rove...Wvrf:rk:8:pf:0

Midnight Classic makes a nice unit, but are they worth the extra $300+

[Ninjakitty]

I have the midnite classic 200. I have not had a single issue so far. Solar has been up and running for about 4 months. It's built really solid. I don't have any experience with the renogy controllers.

[Ninjakitty]

Also, I'm sure you've seen this, but if not

http://www.midnitesolar.com/sizingTool/

[o1marc]

I read reviews on the top 10 Charge Controllers for 2019. Such a wide range of pricing. As low as $39 and then the Midnight Classics that run $700+. Are any of the more expensive ones any better on ROI than the others?

[PNW_Steve]

Panel specs? Configuration?

Battery voltage? If you are thinking 12 volt you will be limited to about 1000watts with the Classic. You can overpanel to some extent but are limited to 79 amps. Nominal voltage is actually 13.8v. So....

13.8v x 79a = 1090watts

You might get away with using that controller with 2400watts of panels if you go with a 24 volt battery.


Victron makes a controller that is rated for 100 amps on a 12 volt system. That would get you closer.

I have done quite a bit of looking and have not been able to find a controller that is rated for more than 100 amps and still support a 12 volt battery. The higher rated units, that I have found, don't support 12 volt. Only 24v-96v and they are quite expensive.

The folks over on solarpaneltalk have some great info on solar system sizing and design. Lots of informative stickies including my favorite: https://www.solarpaneltalk.com/forum...-size-tutorial

[PNW_Steve]

You could break up your array into two and run two charge controllers and get 158a-200a of charge capacity.

If you have 200a charge capability at 12v then you will need roughly a 2000a/h battery bank. You could run six of these in series : 2 YS 27P | Rolls Battery

Unfortunately that is about 1500 lbs of batteries.... And they cost around $1000 each....

Another option would be to configure your charge controller to limit charge current to protect your batteries from boiling and go with a more modest battery bank. But... If you are going to tell the controller to only use a portion of the panels then why put more up there?

Gotta give it to you Marc. You think big.

[o1marc]

Originally Posted by PNW_Steve

You could break up your array into two and run two charge controllers and get 158a-200a of charge capacity.

If you have 200a charge capability at 12v then you will need roughly a 2000a/h battery bank. You could run six of these in series : 2 YS 27P | Rolls Battery

Unfortunately that is about 1500 lbs of batteries.... And they cost around $1000 each....

Gotta give it to you Marc. You think big.

Ya, $830ea, $5000. Am I thinking too big?

[PNW_Steve]

Originally Posted by o1marc

Ya, $830ea, $5000. Am I thinking too big?

I wish I could remember where I read it, someone made a comparison using a car. The engine is your load, the gas tank is the batteries and the gas pump is the solar.

The engine runs from the gas in the tank. When the tank gets low you refill the tank from the gas pump.

Loads run from the battery and the battery gets refilled when the sun shines.

System design generally goes:

Identify loads
Spec inverter and battery to support those loads.
Spec panels and charge controller to fit battery and local conditions (solar insulation)

Sometimes we have to compromise ideal design because of budget or physical limitations.

I do think that 2400+ watts is a bit overkill in this application. Primarily because of battery challenges. Weight, space and cost.

Lately solar panels have dropped significantly in price. Unfortunately the components that go along with them have not.

I will be spending 1/3 of my "solar budget" on panels and 2/3 on batteries, charge controller and materials. This does not include inverter.

[Iceni John]

I have eight Sharp 255W panels totaling 2040W, and because each group of four are separately tiltable I've split them into two completely separate groups. Each group of four powers a Morningstar TS-MPPT-60 which in turn charges four golfcart batteries in series and parallel, in other words I have two entirely separate systems running in parallel. Even if Something Bad were to happen to one panel, or one group of panels, or one CC, or one battery, or one bank of batteries, at worst I would lose at most only 50% of my total power. Redundancy is good!

You may want to use a CC (or two) that doesn't rely on fans for cooling. Fans are always the first things to fail, and in a potentially dusty environment they'll suck gritty dust into the CC's interior. No bueno.

John

[o1marc]

Okay, 2400 is overkill, I can cut down the quantity of panels. Where should I start for the next piece of the equation. I know asking for averages is subjective, but for a normal Skoolie what would be the requirements? Wiring the electric is not an issue for me, solar is totally greek to me still.

[FamilyCircus]

I can only give you my example as a reference, Im not a profesional.

I have 6 panels at 325watts each, Im breaking mine up into 3 strings of two panels and using 3 inexpensive 150v/40amp MPPT charge controllers. This makes it way cheaper than a single controller and adds redundancy to the system. each controller was 166.00 on fleebay. More wire yes but way cheaper. I was looking at the Magnum PT-100 but at 750.00 it was out of my immediate price range

[o1marc]

Originally Posted by FamilyCircus

I can only give you my example as a reference, Im not a profesional.

I have 6 panels at 325watts each, Im breaking mine up into 3 strings of two panels and using 3 inexpensive 150v/40amp MPPT charge controllers. This makes it way cheaper than a single controller and adds redundancy to the system. each controller was 166.00 on fleebay. More wire yes but way cheaper. I was looking at the Magnum PT-100 but at 750.00 it was out of my immediate price range

What do you have for a battery bank?

[FamilyCircus]

I haven't purchased them yet since they are a bit of a depreciating asset, they dont stay fresh for months at a time, so I will buy them when I get very close to being done with the build.
With that said, Im using 9 GC12 group 12v 150Ah flooded batteries for a total of 1350 Ah and so 675 of usable capacity.

I chose flooded because they tolerate more cycles than AGM and gels are just junk and I cant afford Lithium.

Attached is the picture of my battery box

[PNW_Steve]

The first piece of the equation is how much do you use.

All subsequent calculations depend on the load.

What you use is VERY lifestyle dependant.

The most cost effective approach to solar is to reduce consumption before adding capacity.

[o1marc]

Originally Posted by PNW_Steve

The first piece of the equation is how much do you use.

All subsequent calculations depend on the load.

What you use is VERY lifestyle dependant.

The most cost effective approach to solar is to reduce consumption before adding capacity.

So I need to source my appliance needs first?

[joeblack5]

If you like experimenting, then run your AC from a belt driven DC motor and or your electric hot water tank on a voltage directly from the solar panels. Then in addition you have preferable multiple mppts to charge your battery. No need to have an overly large battery bank. The water heater replaces a large part of that capacity.
I am working on the Ac belt driven compressor directly of the solar panel. It is self regulating...more sun more Ac.. The mppts take care of the rest.

Later j

[Yukon Cornelius]

Originally Posted by PNW_Steve

You could break up your array into two and run two charge controllers and get 158a-200a of charge capacity.

If you have 200a charge capability at 12v then you will need roughly a 2000a/h battery bank. You could run six of these in series : 2 YS 27P | Rolls Battery

Unfortunately that is about 1500 lbs of batteries.... And they cost around $1000 each....

Another option would be to configure your charge controller to limit charge current to protect your batteries from boiling and go with a more modest battery bank. But... If you are going to tell the controller to only use a portion of the panels then why put more up there?

Gotta give it to you Marc. You think big.

That would be a monster of a system tho....

[PNW_Steve]

Originally Posted by o1marc

So I need to source my appliance needs first?

In order to size a system that fits your needs well you should probably know what your loads are.

Otherwise you are spending a fair bit of money and making a guess.

A "kill-a-watt" meter is an awesome tool for finding out what your appliances really use.

[AaronTSchultz]

I am wondering myself which charge controllers to purchase as our plan is to be completely electric. 2000+watts solar into 2 charge controllers, into 2 salvaged tesla batteries in parallel. Batteries are at 24v with small tolerances of about 24.4 high and 18.x low. However the charging amp ability is quite high for the batteries. My question is after I run these to the inverter/charger which will also have shore power capabilities.... How do I wire the inverter/charger to charge the batteries back equally, (if they are in parallel) if we are plugged in somewhere and it's necessary. Or am I completely over thinking this?

Lastly any advice on hardware for this build would be helpful. I would like the mobile monitoring abilities as well as over and under charging disconnects.

Thanks all for any advice

[Ninjakitty]

Originally Posted by AaronTSchultz

I am wondering myself which charge controllers to purchase as our plan is to be completely electric. 2000+watts solar into 2 charge controllers, into 2 salvaged tesla batteries in parallel. Batteries are at 24v with small tolerances of about 24.4 high and 18.x low. However the charging amp ability is quite high for the batteries. My question is after I run these to the inverter/charger which will also have shore power capabilities.... How do I wire the inverter/charger to charge the batteries back equally, (if they are in parallel) if we are plugged in somewhere and it's necessary. Or am I completely over thinking this?



Lastly any advice on hardware for this build would be helpful. I would like the mobile monitoring abilities as well as over and under charging disconnects.



Thanks all for any advice

The inverter/charger will have a DC side. It uses the positive and negative DC cables to pull from the batteries and send to the batteries.

I run all my DC positives to a bus bar and from that busbar to the batteries, same for negatives, also have my grounds on the negative busbar.

Your in parallel with 2 batteries, run from + busbar to + on one battery and - negative bus bar to the - on the other battery.

Just how I have it setup