250W House panel to Redarc

Code4

New Member
Can I attach this 250W solar house panel to my Redarc BCDC1250D or is the max voltage going to be too high ? Pic is from the rear of the panel.
250W House panel.jpg
 

CaptainBanana

Well-Known Member
Can I attach this 250W solar house panel to my Redarc BCDC1250D or is the max voltage going to be too high ? Pic is from the rear of the panel. View attachment 69999

It's .6 higher than the red arc is rated, you're probably going to have to call Redarc and ask them if their cut off his hard at 32 volts.

Also I'd be surprised if that Chinese panel put out anywhere near the claimed output and you might want to test it voltage yourself to see if it does actually cut off at 32.6v.

I had Redarc in my last caravan but I put enerdrive in my current one because they support much higher voltage.
 

Hoyks

Well-Known Member
The 32V is probably on a brand new panel at midday on a perfectly clear, cloudless day.

If in doubt, you could run it through a MPPT regulator to knock it down to 14V.

As the panel will be lucky to crack 8A and the charger can handle 50A, I think there is a margin of safety there.
 

dabbler

Active Member
The claimed VOC of 37.5v (Vm isn't the number to look at) is much higher than Redarc 1250 will handle and Redarc claim the unit's MTTP won't switch on if input voltage is too high. But you need to ask them if it will actually damage the dcdc.

The efficiency might drop with age degradation resulting in lower power output but the voltages may still be close to stated (and probably will).
 

cam04

Well-Known Member
12v chargers, if they work at all, will just clip all the extra voltage and take what they can use, leaving a max 7a @ 12v. If you get a proper buck constant voltage converter you now have the opportunity for nearly 250w @ 12v = 20a which suddenly makes carrying the behemoth panel somewhat worthwhile. The cheap eBay blue inline chargers will handle your panel at 12v 7a no problem and protect the red arc from the fun and games - just find a naked battery feed like a fridge power outlet or the terminals direct.
 

mac_man_luke

Well-Known Member
Open circuit voltage is too high

Redarc recommend open circuit voltage of 17.5v to 28v

Open circuit voltage will be close to maximum with not much sunlight (but current potential will be low)

If you want to use that panel get an MPPT controller such as one of the Victron units as they will take much higher input voltage (and are really good)
 

mac_man_luke

Well-Known Member
12v chargers, if they work at all, will just clip all the extra voltage and take what they can use, leaving a max 7a @ 12v. If you get a proper buck constant voltage converter you now have the opportunity for nearly 250w @ 12v = 20a which suddenly makes carrying the behemoth panel somewhat worthwhile. The cheap eBay blue inline chargers will handle your panel at 12v 7a no problem and protect the red arc from the fun and games - just find a naked battery feed like a fridge power outlet or the terminals direct.

MPPT does not clip voltage, that is PWM that would do that which is only in really cheap solar controllers (or ebay "mppt" controllers)

Either want a panel with lower open circuit voltage or a solar controller rated for higher voltage panels
 

cam04

Well-Known Member
MPPT does not clip voltage, that is PWM that would do that which is only in really cheap solar controllers (or ebay "mppt" controllers)

Either want a panel with lower open circuit voltage or a solar controller rated for higher voltage panels
Yes, I should have mentioned “cheap”. Anything capable of handling all of that voltage will be exxy and essentially make the red arc redundant like an Enerdrive DCDC but you are talking a lot of money. It would be cheaper to replace the panel as you mentioned and carry on with the red arc in than go that way. At least the little ‘clippers’ or a cheap buck converter will give him a charge at a cost that makes sense for a second hand house panel worth $50 - well that was the point I poorly made in the first place. I agree with you, just trying to get a result that he can live with. I got an ‘indicated’ 9a out of an eBay special pwm on one of those house panels which is a tick in the box for most people.
 

mac_man_luke

Well-Known Member
Victron solar controllers are pretty good value between $100-200 depending on the model and generally will accept 70-100v input
I had a 320w Sunpower panel on my canopy with a victron smart solar and it was so much better than anything automotive / 12v
(unfortunately became impractical with my RTT so run crappy useless flexible panels now)
 

cam04

Well-Known Member
Just a heads up. I had a crappy first gen kings 160w semi flexible which failed in short order. They came to the party and replaced it and it turns out they have made some decent steps in the right direction with the 2nd gen one they sent me. I’ll be getting another for the $160 they want - I. Was forced down the semi flexible route also - they slide under the bed mattress in the camper.
 

Bru9

Active Member
The short answer is no.
That's a 24v panel and the redarc is for 12v (22voc) panels. from what I have learned electronics dont have much tolerance to voltages and can easily be damaged even by the VOC. At 0 degrees temps that could easily be 40v plus!
It's ridiculous spending that much and being limited to 12v panels, the best bang for buck is enerdrive dc dc and a victron mppt, the small victrons are good value for money. Quality controllers (not the weekend warrior brands) have wide voltage ratings because of the cold temps, uncertainty with panel brands, you need a safe buffer. I also have a voltage rated breaker on the solar raw input for those times things dont mix too well.
Voc numbers are at 25c and drop ever so slightly in heat.

PWM simply connects the panel directly to the battery in bulk stage, so the battery pulls down the vmp close to the battery volts, so high voltage panels in bulk stage = big power loss. and in absorption all the changes, is it sends pulses of various widths and on/off breaks to average the power simply as a great cost effective way to regulate the voltage. Even in float. Same deal for controlling dc motor speeds without actually lowering the voltage. With 12v/17-18vmp panels you loose a few volts worth (17-14.4) lower vmp panels are not always a good match due to voltage losses.

The MPPT separates the battery and panel, and is always trying to load up the optimal power curve vmp, it simply converts the excess voltage to more battery current. An mppt will fire up as soon as the panel voltage is enough to push through the mppt in early morning. It dont matter what the voltage, as long as the panel is a bit higher than the battery, panels collect current.
Mppt is great not soo muvh for gains in performance, that is overrated, but to avoid carraying 20meters of 8b&s, see how horrible that is, how it tangles soo much. I have seen places where you literally cant get any sun until you walk 100meters away.:oops:

The reason the sunpower are better than automotive 12v is simply because of quality. Those kinds of panels are the real deal and made for house roofs which is big business. The last of the quality "12v" have dried up.
 
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