New guy, with an older Xantrex C40

[Linkclan]

Hello all and thanks for having me.

I am posting in the RV forum as this is kind of an isolated system and will be repeated in my fifth wheel.

Currently, I have two 210 panels series connected with a Xantrex C40 controller. Storage is two V-max 125ah parallel for 12v storage. This is to supply my home office / ham radio workstation. It works great except when the Xantrex goes solid green (fully charged) the voltage runs to over 16.4v as tested with my Fluke176 as well as the display on my radio.
Settings are set for;

Charge Control Mode
12 Volt Position
EQ/LVR Manual
Bulk set at 15.0v
Float set at 13.8v

My fear is that it is will cook my batteries as well as possibly damage my equipment. I therefor watch and carefully monitor the voltage and disconnect the panels as it rises above 15.5v. I also disconnect when I leave the office and cannot monitor status.

So... is this normal? And, will it be okay or should I be looking for another controller.

Thanks

[littleharbor]

A C-40 is a PWM charge controller and won't step down voltage like a MPPT type controller does. The max allowable voltage into a C-40 is 125 volts but that doesn't mean you can use high voltage for a 12 volt system. Keep in mind this controller is a 12 24 48 volt controller.

What are the specs of your 210 watt panels? Evergreen solar made 12 volt panels in this wattage range, but regardless if they are 12 volt or higher voltage panels you shouldn't be series wiring them for a 12 volt system. You should be able to dial in the bulk and float voltage on the C-40 with a dmm by pointing the probes in the test points inside the controller. This procedure is described in the manual. If you don't have the manual look it up online.

[Sunking]

Currently, I have two 210 panels series connected with a Xantrex C40 controller.

That is your problem 210 watt panels indicate you are using high voltage solar panels with a PWM controller. Huge mistake. Assuming you wired them in parallel, You are turning you 420 watts into 140 watts. If you wired them in series 70 watts. So now you have a damaged controller and incompatible equipment.

What you need to do is get a good 40 amp MPPT controller like a Morningstar TS-45-MPPT, and wire your panels in series.

73's

KF5LJW

[Mike90250]

To fully charge a battery, you have to raise the voltage above what the battery is sitting at, To do it in a few solar hours, requires going a bit above what a car battery voltage is.
I think if your controller is set properly, 16V for the monthly EQ is not beyond the realm of possibility. This voltage may not be acceptable for some gear.

[Linkclan]

A C-40 is a PWM charge controller and won't step down voltage like a MPPT type controller does. The max allowable voltage into a C-40 is 125 volts but that doesn't mean you can use high voltage for a 12 volt system. Keep in mind this controller is a 12 24 48 volt controller.

What are the specs of your 210 watt panels? Evergreen solar made 12 volt panels in this wattage range, but regardless if they are 12 volt or higher voltage panels you shouldn't be series wiring them for a 12 volt system. You should be able to dial in the bulk and float voltage on the C-40 with a dmm by pointing the probes in the test points inside the controller. This procedure is described in the manual. If you don't have the manual look it up online.

This looks like an informative answer. Nowhere in the manual does Xantrex say what the allowable input voltage should be nor how it relates to the output voltage. I'll have to check when the sun is shining but, I believe with the two panels series connected, I have about 60vdc open circuit. I did see in the manual that it's(C-40) max was 125vdc and felt sure it would be well within its operating range. If I am reading you correctly, I need 12v panels to supply 12v(15.5v) to the Xantrex which is not smart enough to mux a higher volt array into the specified charging voltage? So... Either get a MPPT type controller or, get 12v panels and parallel them for the C-40 to understand and to obtain my 20~30a charging target.

I have eight more of these panels out in the shop and can get the specs tomorrow. They are about 7yrs old, new in the box. If I remember correctly, Sun-Solar is the name.

I also have out there in the shop somewhere, an Outback which i believe is rated at 60a but I think that would be a bit much for this application. I'll keep that around for another project.

Thanks,
Paul

[Linkclan]

To fully charge a battery, you have to raise the voltage above what the battery is sitting at, To do it in a few solar hours, requires going a bit above what a car battery voltage is.
I think if your controller is set properly, 16V for the monthly EQ is not beyond the realm of possibility. This voltage may not be acceptable for some gear.

These are AGM batteries and the bulk charge should be around 15.5. EQ is not recommended for this type battery, ever. I purposely have the C-40 set for "Manual" regarding float so that it never happens. Also, electronic equipment gets a little fussy about getting over about 10% of nominal voltage. Nominal for 6 cells is 13.8 + 1.38 = 15.18 that even puts the recommended bulk charge of 15.5 a bit over what I'm looking for but not yet harmful.

Paul

[Linkclan]

That is your problem 210 watt panels indicate you are using high voltage solar panels with a PWM controller. Huge mistake. Assuming you wired them in parallel, You are turning you 420 watts into 140 watts. If you wired them in series 70 watts. So now you have a damaged controller and incompatible equipment.

What you need to do is get a good 40 amp MPPT controller like a Morningstar TS-45-MPPT, and wire your panels in series.

73's

KF5LJW

I think you hit the nail on the head. Wrong controller for the application! I will look at the Morning star.
Panels are currently wired in series with about 60v open circuit.
I don't think I killed my C-40 as I closely monitor it and shut it down when charging is complete. Batteries are way too expensive to ignore. Sure will be nice when it is in full automatic!

Edit after review of the Morningstar TS-45-MPPT
This appears to be a 3kW controller. Is there something out there for more like a .5 or 1kW system? I'm only charging two batteries.

73-K6PLE

[Mike90250]

Morningstar makes a couple smaller (and larger) MPPT controllers. Midnight Kid is an option, as is Rogue Power

[Sunking]

I think you hit the nail on the head. Wrong controller for the application! I will look at the Morning star.
Panels are currently wired in series with about 60v open circuit.

OK with PWM Controllers INPUT CURENT = OUTPUT CURRENT. All a PWM Controller does is connect the panels to the battery. Basically a switch that turns Off/On 20,000 times a second. So you have your panels wired in series. A good educated guess is your panel current is roughly 8 amps into the controller. Do the math and on the output to the battery you have 12 volts x 8 amps = 96 watts, lets just say 100 watts from 420 watts of panels.

If you are going to use PWM controllers which is a mistake today, you have to use very expensive Battery Panels with a Vmp of 17 to 18 volts. A 100 watt battery panel has an Imp of 100 watts / 18 volts = 5.5 amp. Again do the math 5.5 amps x 12 volts = 66 watts. The highest efficiency with a PWM system is 66% on its bet day. It also forces you to wire all the panels in parallel which sucks.

With a MPPT Controller Output Current = Panel Wattage / Nominal Battery Voltage. Again do the math 420 watts / 12 volts = 35 amps. Huge difference between 35 and 8 amps. Using MPPT allows you to use much higher voltage and cheaper Grid Tied panels and wire them in series. With a 150 Voc Controller you can wire up to about 4 panels in series.

You say you have a Outback Controller sitting around doing nothing. If it is MPPT I would get that thing out, and trash the C40 antique in a heartbeat. Sell it on QRZ to a Sucker.

[Sunking]

Edit after review of the Morningstar TS-45-MPPT
This appears to be a 3kW controller. Is there something out there for more like a .5 or 1kW system? I'm only charging two batteries.

Sure there is, but you need at least 35 amps, so it is not that much larger. The TS-45-MPPT maximum power input on:

12 volt battery is 600 watts,. you are running 420 watts.
24 volt battery is 1200 watts
48 volt battery is 2400 watts.

Keep in mind the Controller does not determine the current, Panel wattage and battery voltage determine the controller current. Just like an Extra Class License does not mean you have to run Legal Limit, nor would you want to. It is just there in case you need it someday in the future. As I said you need at least 35 amps.

One thing to look out for. The TS-45-mpppt has a Voc limit of 150 volts. You want that to be at least 150 Voc as it allows you to wire several panels in series. Many of the smaller controllers have Voc limits of 60 to 70 volts which means you have to wire your panels in parallel. So be careful what you ask for, check the specs, and ask questions.

[Linkclan]

Just like everything else, the projects all grow at a rapid pace!

The Outback is a Flex-80 MPPT charge controller rated for 1250w of panels with a 12v battery system. The original plan was a 24v system which would allow 2500watts of panels.
Also out in the shop is an Outback VX3524. Really would like to have two of these to get 240vac without the losses of my 2kVA buck transformer.
Total of 10ea SunPower 210w panels. SPR-210-BLK-U
Out in the yard s is a Zomeworks Track Rack complete with a 20ft X 6in Gal pole. I do go out and grease the bearings and bushings periodically.
Lets all cry about this one.... Storage "WAS" a really nice set of SolarOne deep cycles in two cabinets. Should have left them dry!
Also found a few(3) of those little AirX 24v turbines.
Everyone should have an old fashioned hand pump for the well too. Electronics fail you know!
General materials are not a problem as I am a commercial electrical contractor (EST 1989).

I'm going to open a little hole in my tin hat and tell you all this was set aside in a metal cabinet at the shop except for the battery bank. 2008 got me thinking about the unthinkable!

So.... What I really want to do at this point is maintain my workstation with a couple panels, batteries and charger. Hopefully with very little common mode noise. With the Xantrex, I was able to simply shut it off and operate in a relatively quiet environment. Guess I could shut any of them down. I looked at the Chinese variations and they are all in plastic enclosures and the consensuses is that they are all very RF noisy.

In the end here, It looks like that C-40 was simply the wrong component as I was completely oblivious about the MPPT technology. I will take your advice and get myself a TS-45. May as well get two as I intend to put the same system together in the fifth wheel.

Thanks,
Paul

[Sunking]

Paul the best Charge Controller for Hams is Morningstar MPPT series. They generate the least RFI. The perfect setup for a ham shack is a 200 watt panel, MS Sun Saver 15 amp MPPT, and a pair of Trojan T-105-RE. This is what I use, but with one caveat. I use a Astron 12/70 amp power supply. The solar just sits there and collects dust because the power supply keeps the battery charged up and runs the equipment. If you want more, then move up to 500 watts of panels, a 45 amp MS TS-45-MPPT, and a pair of Trojan LR16RE-B batteries.

Solar is only useful in that set up if power is out and the sun is shinning at noon. Even on contest weekends I do not bother bringing the panels. I just use the 2 Trojans and they are more than enough for 2 days of contest.

[Linkclan]

Paul the best Charge Controller for Hams is Morningstar MPPT series. They generate the least RFI. The perfect setup for a ham shack is a 200 watt panel, MS Sun Saver 15 amp MPPT, and a pair of Trojan T-105-RE. This is what I use, but with one caveat. I use a Astron 12/70 amp power supply. The solar just sits there and collects dust because the power supply keeps the battery charged up and runs the equipment. If you want more, then move up to 500 watts of panels, a 45 amp MS TS-45-MPPT, and a pair of Trojan LR16RE-B batteries.

Solar is only useful in that set up if power is out and the sun is shinning at noon. Even on contest weekends I do not bother bringing the panels. I just use the 2 Trojans and they are more than enough for 2 days of contest.

Per above, MS TS-45-MPPT is already in my Amazon cart. I also have an Astron 12/50 and have been contemplating a few upgrades, DMs, PowerPoles etc. At least this will get it out, plugged in and possibly move that project to my desk. My PowerGate will only charge at 10a but that will be sufficient as there is very little draw on the batteries. At this point, the batteries are already here and in use. Got the AGMs as they are kept indoors and less likely to burp noxious fumes into my work-space. I believe the freezing we have up here contributed to the failure of my SolarOne banks outside. Not much of a contest ham but I probably will attend our field day and probably run the gota station with my KX3 out of its self contained 20ah power box. Pic of that is on my QRZ page.

Thanks for all your help guys!
Seriously thinking about installing the primary system as my E bill is going through the roof!

Paul
73-K6PLE

[Sunking]

Seriously thinking about installing the primary system as my E bill is going through the roof!

If you think the POCO charges a lot, how about 5 to 10 times more for Off-Grid.

[SunEagle]

Per above, MS TS-45-MPPT is already in my Amazon cart. I also have an Astron 12/50 and have been contemplating a few upgrades, DMs, PowerPoles etc. At least this will get it out, plugged in and possibly move that project to my desk. My PowerGate will only charge at 10a but that will be sufficient as there is very little draw on the batteries. At this point, the batteries are already here and in use. Got the AGMs as they are kept indoors and less likely to burp noxious fumes into my work-space. I believe the freezing we have up here contributed to the failure of my SolarOne banks outside. Not much of a contest ham but I probably will attend our field day and probably run the gota station with my KX3 out of its self contained 20ah power box. Pic of that is on my QRZ page.

Thanks for all your help guys!
Seriously thinking about installing the primary system as my E bill is going through the roof!

Paul
73-K6PLE

Paul. Believe it or not the best way to reduce your E bill is to use less electricity.

Generating the power yourself from batteries is still much more expensive then purchasing it from just about any POCO. The only way solar will really save you money is to go with a grid tie system. Using batteries will put in the poor house a lot faster.