Favorite generic PWM charge controller?

[camelCase]

Hi, first post here and hopefully not a tiresome question...

I have the opportunity to get a couple of free used solar panels off of an old RV. Supposedly they are about 10 years old and 250 watts each. They have some 10ish gauge wire and MC4 connectors but nothing else. I'd like to install them to my old truck camper and want to do it on the cheap as I'm a little dubious about how much power I'll get out of them here in rainy Seattle.

My question is if there is a budget minded charge controller that anyone would recommend? The panels say Vmmp = 30.5, Voc = 37.6 and current of 8 amps. I would probably need to wire them in parallel if I used a PWM controller? Thanks!

 

[OnTheRoadAgain]

Congrats. good find.

Just remember...there are good Charge Controllers and there are cheap charge controllers......

But it's not easy to get a good AND cheap charge controller.

That said...I bought a used Xantrex C40 40 amp PWM controller for about $40 and it's been phenomenal so far.

 

[grizzzman]

Hi, first post here and hopefully not a tiresome question...

I have the opportunity to get a couple of free used solar panels off of an old RV. Supposedly they are about 10 years old and 250 watts each. They have some 10ish gauge wire and MC4 connectors but nothing else. I'd like to install them to my old truck camper and want to do it on the cheap as I'm a little dubious about how much power I'll get out of them here in rainy Seattle.

My question is if there is a budget minded charge controller that anyone would recommend? The panels say Vmmp = 30.5, Voc = 37.6 and current of 8 amps. I would probably need to wire them in parallel if I used a PWM controller? Thanks!

Are you planning on running the system at 24 volts? If not you will need a MPPT controller or loose about (at least) 1/2 the watts at 12 volts.

 

[coil1002]

Hi, first post here and hopefully not a tiresome question...

I have the opportunity to get a couple of free used solar panels off of an old RV. Supposedly they are about 10 years old and 250 watts each. They have some 10ish gauge wire and MC4 connectors but nothing else. I'd like to install them to my old truck camper and want to do it on the cheap as I'm a little dubious about how much power I'll get out of them here in rainy Seattle.

My question is if there is a budget minded charge controller that anyone would recommend? The panels say Vmmp = 30.5, Voc = 37.6 and current of 8 amps. I would probably need to wire them in parallel if I used a PWM controller? Thanks!

Solar harvest is not as bad as you would think this is my totals with a 300 watt array and I live in federal way

 

[Bubba1]

You will probably be fine with either controller. That said I would try a mppt. My no name pwm controller and 200w of panels is producing 60 to 80 amps a day at 12v. I'm considering the rich solar controller at about $80. What batteries do you have?

 

[camelCase]

You will probably be fine with either controller. That said I would try a mppt. My no name pwm controller and 200w of panels is producing 60 to 80 amps a day at 12v. I'm considering the rich solar controller at about $80. What batteries do you have?

coil1002, wow, I think I could run my camper almost indefinitely with that amount of power. If I'm reading your chart right and doing my mental math correctly, you get over 20ah per 100w panel per day on summer days?

Bubba1, my camper has 2 group 27's in parallel. They're a couple of years old but seem to still hold a charge great as I've never even pulled them down to 60%. They're enough to run the LED lights and a diesel heater over night. I'll probably replace them with something better when they go bad, but they're working for now. The truck has a voltage sensing relay from the alternator that pushes ~50 amps into the batteries when they are under 80% charged, so I can bring them back up fairly quickly while driving or idling. I modified the sense wire on the alternator with a switched diode so I can bump the voltage from 14.4 to 15v and back as desired, which means the camper batteries see ~14.7 or so volts from the alternator when the diode is in the circuit.

I'm getting excited to install the panels as I see myself going on lots of fishing trips soon as my wife has just moved her mother in with us. ? Those panels should even enable me to even do some remote work from the road.

 

[MisterSandals]

I'm getting excited to install the panels as I see myself going on lots of fishing trips soon as my wife has just moved her mother in with us. ? Those panels should even enable me to even do some remote work from the road.

I think you are correct and should consider getting a good SCC from the get go.
Something like this with a 5 year warranty and industry standard for reliability and ease of use (with bluetooth app!), its a great investment.

Amazon.com

 

[fratermus]

My question is if there is a budget minded charge controller that anyone would recommend? The panels say Vmmp = 30.5, Voc = 37.6 and current of 8 amps. I would probably need to wire them in parallel if I used a PWM controller? Thanks!

I own and use some inexpensive PWM for some things but I don't think they are a good fit here. As others suggested, the panel specs make them tough to use productively with PWM on a 12v bank (lots of wasted power). It would make more sense for a 24v bank, since Absorption voltages would be in the ~28.x range.

In cloudy Seattle a 30A MPPT (panels in parallel) would work well with 12v bank. A 40A MPPT if you plan on traveling to sunnier places and want to harness the extra sunpower. 15A/20A MPPT (panels in series) if the bank is 24v.

 

[williamsk913]

With an open voltage of 37.6, you will be leaving a lot of watts on the table. PWM controllers work best on nominal "12v" panels (around 18 or so volts) on a 12v battery bank. I would personally go with a 40a mppt. Fair warning... eBay and amazon do not police their listings and many controllers advertised as mppt controllers are just pwm. Chances are if it is under $90 for a 40a MPPT, it is probably not an mppt.

 

[12VoltInstalls]

You will probably be fine with either controller. That said I would try a mppt. My no name pwm controller and 200w of panels is producing 60 to 80 amps a day at 12v. I'm considering the rich solar controller at about $80. What batteries do you have?

Two group 27s are a good match for 200W pwm

I’m not sure about that rich solar controller but I think will has reviews on it.
I have an epever 40 mppt now but ran the P30L that came with my original kit for several years. The pwm- or at least that brand pwm- used to equalize hard at 15+ volts. I have the epever set for 15.8; I’m not saying it hasn’t ever punched over 15V but I’ve never seen it over ~14.8.
That bothers my head a little because I think 14.x is a little soft for equalizing lead acid batteries, longevity-wise. I’ve added very little water ever to my batteries but the pwm would use some water (especially the year I ran with 10-year-old group 31s). The epever has been online since ?April? and my batteries have not needed any water. That seems like it’s because they dont equalize hard? Unsure.

The point is a few more bucks for the mppt might pay for itself in battery life. In my case, I think I’m going to hook up two more of the 100W panels I have to my pwm just to punch the batteries better.

Just thoughts to consider - it is possible I’m ocd and nutty

 

[fratermus]

I have the epever set for 15.8; I’m not saying it hasn’t ever punched over 15V but I’ve never seen it over ~14.8

IIRC it's on a once-a-month timer so you might not catch it happening. I've seen mine do it if I were standing in front of the display at the time. If you want to force one (or force it more often) you could set absorption voltage to EQ voltage after a full charge then change it back.

Sorry for the digression.

 

[12VoltInstalls]

IIRC it's on a once-a-month timer so you might not catch it happening. I've seen mine do it if I were standing in front of the display at the time. If you want to force one (or force it more often) you could set absorption voltage to EQ voltage after a full charge then change it back.

Sorry for the digression.

Hmm. Once a month? I don’t think that is nearly often enough- and what if it’s a cloudy day? I’m not gonna fuss with it. I have enough parts and cable on hand to just hook up the trusty P30L to 200W of panel and give it a second charging source. Pretty sure that nails’em hard weekly.
(I don’t know why I think this but I think with lead acid every ten days would be great)