Off-grid solar charge controllers

[cedric]

how do i figure the size charger needed

Here in Brisbane it rarely gets below 50deg F at night time in winter most of year its about 60 to 90F My other home in Philippines it never gets below 60 deg F on the coldest winters night.
My favourite PWM charger for small 12v systems is a Chinese copy of an old Steca model. No brand name but available here in Aus from a few big electronics stores.just about impossible to destroy it. Rated max input is 26v but it will take 36 v no problems and still never gets warm. Not like MPPT chargers that tend to die when operated 50% above rated input. They know they not that reliable as only 2 years warranty.. Another reason not good value most PWM as you know give 5 years, as they know there not going to be problem

Picture of it added its a 30a model

I have two solar mono panels rated at 29.7 volts and 8.3 amps

I am using 12v batteries in my RV. Can you recommend a controller that would maximize my charging.
It's my understanding that only an mppt controller can down convert to 12v and make use of all the power by increasing the amps going into the batteries.
thanks for your help
cedric

[Sunking]

I have two solar mono panels rated at 29.7 volts and 8.3 amps

I am using 12v batteries in my RV. Can you recommend a controller that would maximize my charging.
It's my understanding that only an mppt controller can down convert to 12v and make use of all the power by increasing the amps going into the batteries.
thanks for your help
cedric

Ok you have roughly 240 watt panels. Best configuration for an RV would be to wire them in series and minimum MPPT charge controller size is 40 amps @ 12 volt battery. A good quality product in that size is MorningStar Tri Star MPPT Controller

[cedric]

Ok you have roughly 240 watt panels. Best configuration for an RV would be to wire them in series and minimum MPPT charge controller size is 40 amps @ 12 volt battery. A good quality product in that size is MorningStar Tri Star MPPT Controller

Thanks for the quick reply. Yes, they are 250watt mono panals from LG.
Could you help me understand why this is best? In series would be ~60volts input to the controller?Is that correct?

I was thinking connect the panels in parallel and use the SunSaver Duo. It is rated a 30v input

As you can tell I am in the first phase of the learning curve. thanks for the help

[Sunking]

Thanks for the quick reply. Yes, they are 250watt mono panals from LG.
Could you help me understand why this is best? In series would be ~60volts input to the controller?Is that correct?

Yes that is correct. But here is the catch. You go into the CC at 60 volts @ 8.3 amp (500 watts), and go out to the battery at 12 volts @ roughly 40 amps (500 watts).

You can also wire them in parallel if you wish. You then go in at 30 volts @ 16.6 amps, and out at 12 volts @ 40 amps. However the higher input current means more loss and larger wires. So your best option is series wired for maximum efficiency an dlower installation cost. It is a Win-Win scenario.

The Morningstar Tri Star MPPT have a maximum Voc input of 150 volts. That means you can use a panel voltage up to around 130 volts, and at the same 500 watt input would be 3.8 amps input and 40 amps output.

[cedric]

Yes that is correct. But here is the catch. You go into the CC at 60 volts @ 8.3 amp (500 watts), and go out to the battery at 12 volts @ roughly 40 amps (500 watts).

You can also wire them in parallel if you wish. You then go in at 30 volts @ 16.6 amps, and out at 12 volts @ 40 amps. However the higher input current means more loss and larger wires. So your best option is series wired for maximum efficiency an dlower installation cost. It is a Win-Win scenario.

The Morningstar Tri Star MPPT have a maximum Voc input of 150 volts. That means you can use a panel voltage up to around 130 volts, and at the same 500 watt input would be 3.8 amps input and 40 amps output.

Thanks again for your help. The panels have mc4 connectors. Is it best to just cut those and run #8 awg wire to the batteries? or is it better to spend the extra for wire with the mc4 connectors? I'm looking at #8 wire on amazon that has these specs:

Price is 0.79 per foot of wire - You will receive one continuous section of wire
High Current Transfer
Tinned Conductors
Pure (OFC) Oxygen Free Copper with 665 Strands of Wire
We Are An Authorized Stinger Internet Dealer!

thanks
cedric

added: I need 12 ft of wire to reach the batteries. sorry to reach the controller which will be mounted near he batteries.

[Mike90250]

cutting the factory cables, will VOID the panel warranty. Buy a "MC extension cable" and cut IT in half for your array wiring. Forget that wire vendor selling snake oil, in a camper, using "tinned" wire, like they use in boats, will increase your corrosion resistance. Go a gauge thicker, with generic wire, instead of spending $$$ on snake oil.

Ultra Fine wire (welding wire or Locomotive wire) tends to work out from crimped connectors, unless you use a multi-ton hydraulic crimp tool.

[cedric]

cutting the factory cables, will VOID the panel warranty. Buy a "MC extension cable" and cut IT in half for your array wiring. Forget that wire vendor selling snake oil, in a camper, using "tinned" wire, like they use in boats, will increase your corrosion resistance. Go a gauge thicker, with generic wire, instead of spending $$$ on snake oil.

Ultra Fine wire (welding wire or Locomotive wire) tends to work out from crimped connectors, unless you use a multi-ton hydraulic crimp tool.

Thanks Mike for the info. I didn't think about the warranty! yikes... glad I asked.
I thought all wire was generic. Where do people go for generic wire? I want stranded wire right?
thanks

[SunEagle]

Looking for a reliable 20 to 30 amp charge controller.

I am building a small portable solar energy system to be used while camping on my property. I currently have 4 mono crystal panels each rated at 80 watts, with 17.6 output voltage & 4.55 operating amps. I also have a couple of Universal UB12500 50Ah batteries and a Wistler 2500 watt inverter. I plan on getting more batteries but for now I need a charge controller.

What I am looking for is something that is reliable but doesn't cost an arm and a leg. Using the 4 panels in parallel I will have about 18 amps total amps. I need a minimum 20 amp charger but would rather have one rated for 30 amps.

I have looked at the Morningstar, Steca, WELSEE and Net Meter Solar to name a few. I believe that the more expensive ones are not necessarily the more reliable ones. Any information would be greatly appreciated. Thanks

Vince

[cedric]

I am building a small portable solar energy system to be used while camping on my property. I currently have 4 mono crystal panels each rated at 80 watts, with 17.6 output voltage & 4.55 operating amps. I also have a couple of Universal UB12500 50Ah batteries and a Wistler 2500 watt inverter. I plan on getting more batteries but for now I need a charge controller.

What I am looking for is something that is reliable but doesn't cost an arm and a leg. Using the 4 panels in parallel I will have about 18 amps total amps. I need a minimum 20 amp charger but would rather have one rated for 30 amps.

I have looked at the Morningstar, Steca, WELSEE and Net Meter Solar to name a few. I believe that the more expensive ones are not necessarily the more reliable ones. Any information would be greatly appreciated. Thanks

Vince

I am looking for the same thing except I need to handle 40amps. The only controllers I have seen recommended on this forum are the name brand expensive models.

[russ]

With charge controllers and inverters you pay for what you get.

[cedric]

With charge controllers and inverters you pay for what you get.

This is based on fact or assumption?

I have seen RV forums where people are raving about BZ mppt500 which handles 500 watts at 12v.
It cost $205 at the lowest price I have found. That said, there is one forum where they were bashing the BZ products back in 2005. I have not found any forums with negative reports in the last few years since they did a firmware upgrade. No I do not work for BZ. I am just trying to learn from people who have used these products.

What I hate is when someone who may have experience with only one product throwing out blanket statements about the whole line of products. It is really not helpful and in my experience rarely the whole story.

My mother used to say you get what you pay for and she is still paying $10 a bottle for Bayer aspirin. Despite my assurance they are all made from the same chemical.

[SunEagle]

With charge controllers and inverters you pay for what you get.

I don't necessarily agree. While I agree that going cheap usually gets you cheap. But going really expensive sometimes gets you mediocre quality for a high price due to the Manufacturer's name.

I agree with Cedric. We both want to know what others have purchased and if they feel the item was worth the cost or not.

One person's opinion is not always the correct one due to lemons. The more people that support an item the better chance it is worth the cost.

With that said; I don't think it is too much to ask to know which charge controllers are worth their price?

Vince

[cedric]

controller rated amps

Could someone tell me which amps the solar charge controller is listed for.
Say you want to get a xyz controller listed at 40 amps. Is this rating for input as well as the amps it can handle feeding into the battery?

I ask because I am looking at the xantrek c40 which is rated for 40amps and the spec's say it can handle 125v max pv input. I have 2 panels that are rated 250 watts each at 29v and 8.4 amps. It was suggested here that I connect the panels in series which means at the controller I would have 58volts coming in from the panels and 8.4 amps??
So... the controller takes this and puts up to 40 amps into the batteries (best case?)???

So do I need a 40 amp controller because of the 40 amps going into the batteries? or does only the input amps of 8.4 matter? And I could by a 15 amp controller instead.

thanks for any and all help
cedric

[russ]

This is based on fact or assumption? What I hate is when someone who may have experience with only one product throwing out blanket statements about the whole line of products. It is really not helpful and in my experience rarely the whole story.

My mother used to say you get what you pay for and she is still paying $10 a bottle for Bayer aspirin. Despite my assurance they are all made from the same chemical.

Get a life and get real. Buy cheap garbage and be happy - makes no difference to me. I wouldn't do it.

Buy asprin made in Asia - no one has any idea what is really in it.

[SunEagle]

Get a life and get real. Buy cheap garbage and be happy - makes no difference to me. I wouldn't do it.

Buy asprin made in Asia - no one has any idea what is really in it.

Ok. I will go with the path that says pay more and get better. So which make and model charge controller do you recommend for the 30 to 40Amp range?