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Old 11-18-2020, 09:52 AM   #1
Mini-Skoolie
 
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Solar panel readings higher than rating?

Hey fellow Skoolers. So I have 2 200 watt new Renogy panels in parellel. They say the highest voltage rating is 24.1. I bought there dc50 charge controller for its simple use with alternator. It says max voltage input is 25. It was working fine for a month and then the last month as itís been getting colder the voltage during the sunniest part of the goes up to 25.2. Only .2 volts above what the controller can take and it wonít charge. So what Iíve ready is voltage goes up in winter. Panels Voltage work better in cold. It only charges in the morning sun and sunset when sun is low when voltage is between 22-24. So Renogy is being really unhelpful with all of it. There saying to pack them up and send them back to Test them where they will obviously have a different rating than New Mexico sun in winter. They may See them to be fine and they will make me pay for return shipping. Also already have them attached to the roof of the bus any ideas out there
Thanks much everyone
Eric
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Old 11-18-2020, 10:27 AM   #2
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The "maximum" voltage is measured in

"Standard Test Conditions" 25į C cell temperature

"PV USA Test Conditions" is at 20į C **ambient** temp and wind speed of 1 meter per second.

And yes colder temps increases above the results at those conditions.

I reco Victron SCs, the 75/15 specs 75V max, but better to buy panels that are **rated** well below that
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Old 11-18-2020, 11:16 AM   #3
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Dang. Thanks for info. So panels are fine. Already drilled holes down to starter batteries and wires running for this controller. Guess I figured max is max output all around. It’s already set up and get power a lot of the time. I know everyone is trying to stop voltage drops but Is there anyway to create one. Just needs to drop a volt or so. Is there anyway to create that? Thanks amigo
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Old 11-18-2020, 01:09 PM   #4
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I know everyone is trying to stop voltage drops but Is there anyway to create one. Just needs to drop a volt or so. Is there anyway to create that? Thanks amigo

Smaller wire or longer wire so long as the wire can still safely carry the current (check an ampacity table).
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Old 11-18-2020, 04:07 PM   #5
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Just shade the solar panel a little bit as a short term hack. Are these 12v panels?
The solution is get another charge controller.
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Old 11-18-2020, 04:25 PM   #6
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Yeah there 12v panels. Yeah I’ve been shading them currently. Is it bad for controller for the voltage to be on and then voltage to high over and over. Think I’m gonna add 10 feet of wire and coil it up to see. It’s really only .2 volts over. Think this will do it hopefully
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Old 11-18-2020, 06:06 PM   #7
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That controller is a cheap POS anyway, buy a suitable Victron SmartSolar the 15A one not much over $120 or so

Make Renogy refund, or your CC has protection?
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Old 11-18-2020, 06:40 PM   #8
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That controller is a cheap POS anyway, buy a suitable Victron SmartSolar the 15A one not much over $120 or so

Make Renogy refund, or your CC has protection?

I'm not sure there are grounds for a refund (of course they may provide one anyways) unless Renogy sold them the panels and the CC as a package deal or explicitly them they were compatible. It is a well known fact (and stated on every PV panel datasheet) that Voc and Vmp are determined at 25*C and will be higher or lower at different temperatures. Maybe worth a try though, A Victron SCC and DC-DC charger (for alternator charging) would be somewhat competitively priced and much higher quality and well supported.
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Old 11-18-2020, 07:07 PM   #9
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They have a pretty decent rep for customer service

since that is all they have going would be stupid for them to let that rep deteriorate

they'll likely just sell it on as new anyway
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Old 11-18-2020, 07:20 PM   #10
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Is there a victron controller that can charge both from solar and from the alternator. I didn’t buy them as a package but can almost guarantee these panels are max output at 24.1 to make it “ compatable” with there panels. I would happily send it back yes if I can.
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Old 11-18-2020, 07:36 PM   #11
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Crazy to me I know hardly anything about solar and feel I have been trying to explain the temperature difference in volts. Renogy rep first wanted me to send back the controller to test then I explanined this to them and they wanted me to send back the panels for testing. Problem I can’t get a human that knows anything about solar. I told them the results of voltage and they asked me if I have a voltmeter? I feel if they don’t take a refund I may just try to add an extra ten feet of wire. Would it be ok to splice these together? Again don’t know much about electrical but do know more about it than Renogy reps. Haha. Thanks for all your help
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Old 11-18-2020, 07:47 PM   #12
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Is there a victron controller that can charge both from solar and from the alternator.

They do not, but they do sell both components separately VIctron Smartsolar and Victron Orion-TR Smart are the two products you would need.



Quote:
Originally Posted by MedicineBus View Post
I didnít buy them as a package but can almost guarantee these panels are max output at 24.1 to make it ď compatableĒ with there panels. I would happily send it back yes if I can.

The thing is, if you look on the panel datasheet it will almost certainly state that specifications are at 25*C and give a figure called something like "voltage temperature coefficient" which tells you how much to adjust for each degree above or below 25*C / 77*F


This is standardized across pretty much all PV panel manufacturers / brands. So technically speaking they are not at fault here. But as John said, customer service (not tech support) seems to be one of their selling points as a brand, so it is likely they would accept the return if you bought it recently enough. Its worth a try at least.
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Old 11-18-2020, 07:48 PM   #13
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Problem I can’t get a human that knows anything about solar.

This seems to be quite a common problem with Renogy tech support.
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Old 11-18-2020, 10:53 PM   #14
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Why do you think you need anything between your battery and alternator?

You haven't specified what units comprise your bank. . .
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Old 11-19-2020, 12:11 AM   #15
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Why do you think you need anything between your battery and alternator?

You haven't specified what units comprise your bank. . .

My assumption was LFP (because that's why people usually buy this unit it seems) but looking back at the thread, OP doesn't specify battery type.
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Old 11-19-2020, 09:35 AM   #16
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Yeah lfp. Only one 100 ah for now until I get more money to throw in for another. Found one for $500. So yes I wanted alternator charging because of rainy Oregon weather. But by the looks of how much power I consume I don’t think it’s all that necessary. But I do really like the function of it trickle charging my starter batteries because the bus sits for a month or two between places. The other thing is a lot of other options I have read say to be careful with alternator charging with lithium and this controller has a setting for lithium. I probably don’t need alternator charging though. Just thought it was a good excuse for beer runs in a 30 ft bus
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Old 11-19-2020, 04:10 PM   #17
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The other thing is a lot of other options I have read say to be careful with alternator charging with lithium and this controller has a setting for lithium. I probably donít need alternator charging though. Just thought it was a good excuse for beer runs in a 30 ft bus

Well you are correct about needing to be careful with Alt charging with LFP, the Renogy DCC50S is not the only option though. There are maybe 4 or 5 companies that make products for this purpose (DC to DC chargers), most are standalone units, not all in ones so it will be hard to replace the DCC50S with a single product but easy to replace it with two dedicated components (a solar charge controller and DC-DC charger)
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Old 11-19-2020, 06:05 PM   #18
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A dedicated SC is a better idea anyway if you're doing much more than keeping the battery topped up in a vehicle parked outside too far from shore power.
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Old 11-19-2020, 09:01 PM   #19
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A suggestion or two:
Get a small capacity solar panel and controller to charge your bus battery separately. Keeping up your bus battery won't need a huge amount of power to keep it topped off. Another option is to connect the output of your charge controller through a 20 - 30 amp diode. There won't likely be a lot of current flow from you RV batteries to the bus battery, and you won't have any current flow from the bus battery to RV circuits. The diode will have about .5 - .6 voltage drop, but that won't be a big issue. Older RVs sometimes had isolation diodes for this purpose.
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Old 11-25-2020, 06:46 PM   #20
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Quote:
Originally Posted by MedicineBus View Post
Dang. Thanks for info. So panels are fine. Already drilled holes down to starter batteries and wires running for this controller. Guess I figured max is max output all around. Itís already set up and get power a lot of the time. I know everyone is trying to stop voltage drops but Is there anyway to create one. Just needs to drop a volt or so. Is there anyway to create that? Thanks amigo
It is a bad idea to have your charge controllers max input voltage be so close to the VOC of your panels. An inexpensive controller wit a VOC of 60 volts will not only be more efficient but will give you room for upgrades in panels. You'll want to do that soon enough.
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