Anyone have experience with Renogy vs WindyNation PWM solar charge controllers?

[paulcheung]

You've got 20V nominal panels to charge a 12V nominal battery. I go through all of the details in the video I was telling you about, I suggest checking it out. For the Readers Digest version, simple math without losses and other variables is below"

A PWM will not convert the voltage, just pass through the current and the voltage will be pulled down to the battery voltage. So for 1 panel 8.23A for 5 hours will give you 41.15 amp hours, 8.23A x 5 hours. A PWM will convert the voltage down, and in doing so, because of ohms law, will increase the current. 20V / 12V = 1.6. 8.23A x 1.6 = 13.16A x 5 hours = 65.8aH. That's 24.3aH more than if you used a PWM.

However, since you are using such a small battery, you won't be able to use all that power any ways. I agree with the idea of just buy a small panel and PWM charge controller. The free panels are going to cost you more than you save.

Amy

You mean MPPT?

[Amy@altE]

The Math

You've got 20V nominal panels to charge a 12V nominal battery. I go through all of the details in the video I was telling you about, I suggest checking it out. For the Readers Digest version, simple math without losses and other variables is below"

A PWM will not convert the voltage, just pass through the current and the voltage will be pulled down to the battery voltage. So for 1 panel 8.23A for 5 hours will give you 41.15 amp hours, 8.23A x 5 hours. An MPPT will convert the voltage down, and in doing so, because of ohms law, will increase the current. 20V / 12V = 1.6. 8.23A x 1.6 = 13.16A x 5 hours = 65.8aH. That's 24.3aH more than if you used a PWM.

However, since you are using such a small battery, you won't be able to use all that power any ways. I agree with the idea of just buy a small panel and PWM charge controller. The free panels are going to cost you more than you save.

Amy

[SunEagle]

Like I was saying batteries can only be charged so quickly. Here's some info: http://www.solarpaneltalk.com/showth...eries-Tutorial

It's generally c/8 some batteries could be c/4. c is your capacity, so for 15AH batteries c=15 therefore best possible case scenario with batteries that small 15/4 = 3.75. You can't charge/discharge greater than 3.75amps.

You've been going about this whole thing backwards because you have those panels laying around. The first thing to do is figure out your load, that tells you what battery to get, that tells you what you need to charge it.

If all you actually need is a 15AH battery then I'd suggest selling those panels to pay for what you actually need.

I agree. With a maximum charging current of 3.75amps for that 15Ah battery the biggest panel he can safely use would be about 60 watts with a Vmp ~ 17v and Imp ~ 3.5amps and a 10amp PWM CC.

[Bucho]

How long should I expect for it to take to fully charge the battery with 1 panel? With 2 panels?
With 1 panel I can get 100W output, with 2 panels I can get 200W output I think.

If I can wire 2 panels that would certainly be great!

Like I was saying batteries can only be charged so quickly. Here's some info: http://www.solarpaneltalk.com/showth...eries-Tutorial

It's generally c/8 some batteries could be c/4. c is your capacity, so for 15AH batteries c=15 therefore best possible case scenario with batteries that small 15/4 = 3.75. You can't charge/discharge greater than 3.75amps.

You've been going about this whole thing backwards because you have those panels laying around. The first thing to do is figure out your load, that tells you what battery to get, that tells you what you need to charge it.

If all you actually need is a 15AH battery then I'd suggest selling those panels to pay for what you actually need.

[overtak3n]

For a 15 amp agm battery you would only need one 250 watt panel and pwm will easily keep it charged up, it will actually produce many times what is required. the harbor freight jump start packs are usually a 17 amp agm battery and cost about the same as the the 15 amp battery.

How long should I expect for it to take to fully charge the battery with 1 panel? With 2 panels?
With 1 panel I can get 100W output, with 2 panels I can get 200W output I think.

If I can wire 2 panels that would certainly be great!

[jony101]

Most of the low price pwm are chinese made, the ones you linked you might be able to find cheaper on ebay under a different name. i've used the wincong brand 20 amp pwm charger on both 120 watt and my larger 240 watt panel and it worked like a champ 24/7 nonstop for almost a year till i upgraded to mppt. They do the job. From my expierence you dont need mppt on the larger panels example on my 240 watt panel pwm gets me 6 amps, mppt gets me 12 amps, but they both worked, one is more efficient but cost 5 times more, but if your on a budget pwm will work. the thing to watch is what your panel output voltage is and make sure your controller can handle it.
The price of the wincong controller is less than 20 dollars but it has no LCD, but in my case I just bought a dc 90 volt 30 amp combo LED meter and wired it between controller and battery and can see at a glance from across the room how my battery is doing and the realtime charging current. The built-in LCD screens for voltage/amp readings are over rated and at best are only good for programming the parameters.
For a 15 amp agm battery you would only need one 250 watt panel and pwm will easily keep it charged up, it will actually produce many times what is required. the harbor freight jump start packs are usually a 17 amp agm battery and cost about the same as the the 15 amp battery.

[overtak3n]

With PWM controllers Amps in = Amps out.

So those 250w panels have a Vmp of 30.4v and an Imp of 8.23a that's where the 250w comes from: 30.4 x 8.23 = 250.192

This means that if you put them in parallel you get 8.23 x 2 = 16.46

So you should be able to use a 20amp charge controller. It's only when we start talking about MPPT that watts in and watts out comes up.

Does this suggest that I can use a PWM controller?
I'm curious how this works so I'm going to restate what I think I learned, but correct me if I am wrong please.

The 30.4V rating is more important than the 36V open circuit volt rating.
With PWM at 30.4V and 8.23A, that's 250W in. But if the controller is converting it to 12V for the battery I only get 12V * 8.23A out = 100watts.
So I can safely use this PWM controller, but there will be a lot of power loss, maybe a lot of heat?

If I were to use an MPPT controller, for a 12V battery how does it deliver the full 250 Watts from 30V panels?
Can someone show me the math please?

Glad I asked about batteries you can only charge batteries so quickly. Those batteries are way too small for your solar panels.

You mean they'll charge so slowly that I'll need a larger capacity in case it runs out of charge?

Anyway, this is for a school competition and we have constraints. 15Ah is the maximum allowed.
There are several rounds, none of them use the solar panels and battery simultaneously. It's either purely solar or purely battery. I was just hoping to charge the battery in between rounds.

Thanks.

[Bucho]

We haven't decided on batteries yet. Thinking of using a deep cycle battery like this:

http://www.amazon.com/gp/product/B006T07BC0/ref=olp_product_details?ie=UTF8&me=

Thanks.

Glad I asked about batteries you can only charge batteries so quickly. Those batteries are way too small for your solar panels.

[Bucho]

Sorry for he confusion. I assumed the controller can handle 30A, at 12V that's 360 watts. For two 250 watt panels, that's not enough.
Also, I modified the original post to fix the voltage but forgot to modify the rest of the post. Edited the post again.
Thanks.

With PWM controllers Amps in = Amps out.

So those 250w panels have a Vmp of 30.4v and an Imp of 8.23a that's where the 250w comes from: 30.4 x 8.23 = 250.192

This means that if you put them in parallel you get 8.23 x 2 = 16.46

So you should be able to use a 20amp charge controller. It's only when we start talking about MPPT that watts in and watts out comes up.

[jimindenver]

That battery weighs 9.8 lbs, not much storage there. With a 15 Ah capacity you will only get 7 and a half before it needs to be recharged. We had a 35 Ah gel cell that we used to keep cell phones and Mp3 players charged. It also powered a small portable DVD player or two small personal fans. With such limited use it would go a week to 10 days before needing to be recharged. The last trip we used it we replaced the portable DVD player with a TV/DVD combo that pulled 65w. That didn't sound like much but watch a movie or two and the battery needed to be recharged. After that we went to the full size systems and the gel cell is somewhere in the garage.

[overtak3n]

Or this:

http://www.atbatt.com/csb-battery-evh12150-12v-15ah-extended-deep-cycle-battery.asp

[russ]

We haven't decided on batteries yet. Thinking of using a deep cycle battery like this:

Deep cycle? Not at all - those are standard batteries.

[overtak3n]

We haven't decided on batteries yet. Thinking of using a deep cycle battery like this:

http://www.amazon.com/gp/product/B006T07BC0/ref=olp_product_details?ie=UTF8&me=

Sorry for he confusion. I assumed the controller can handle 30A, at 12V that's 360 watts. For two 250 watt panels, that's not enough.
Also, I modified the original post to fix the voltage but forgot to modify the rest of the post. Edited the post again.

Thanks.

[Bucho]

We were given two solar panels 250 watts each. At 30-37V and 30A, I think wiring the solar panels in parallel to charge the battery together would require at least 40-50A charge controller so I'm probably only going to use 1 solar panel to charge the battery unless someone can recommend a charge controller that can handle both panels and is affordable (at most about $100).

Thanks!

So I don't see where your getting the 30A from also can you tell us what you're using for batteries?

[overtak3n]

Should I be looking at the 30V max power rating or the 36V open circuit rating of the panels?

As for the controller:
Is a PWM controller not suggested because I can't charge a 12V battery with 30+V panels so it won't work?
Or is it that I can charge the battery but there will be a lot of power loss so it would be inefficient?
Which of the above two is correct?

This is for a small project, for a school competition, so spending hundreds on a MPPT charge controller would be out of the budget.

Thanks for all the help!