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I'm running two BP solar panels tied in series to produce 24V at about 5 amps. They feed into a Xantrex C40 controller which charges 2 Trojan deep cycle batteries tied in series to make 24V. This PV system is running a small communications repeater. The entire system is inside a small vented but not chilled enclosure. The issue I'm having is during full sunlight, the charge controller is not outputting any amps to charge the batteries, even though it is showing 23 volts when the controller is set to charge up to 27 volts. What I'm thinking is happening is that the temperatures inside the enclosure is causing the controller to enter its high temperature cut back mode. Does anyone know of a charge controller that is meant to handle high temperatures? Or is there something else I'm missing? Thanks in advance for any advice.
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Where are you located?? is it extremely HOT??
What is the wire distance from the panels to the controller??
What is the actual specs on the panels?? Are they 2 of the 17-18 VMP panels?? or 30 or 36 VMP panels??1160 watts, Midnite 150 , Xantrex SW2000 -
Location is the California High Desert area. Daytime summer temperatures routinely exceed 100 degrees. Distance from the panels is approximately ten feet. The panels are rated at 17 Voc each. I've measured up to 38 volts coming from the panels tied in series, which is well within the range stated in the CC's manual for 24V operation.Comment
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OK if I had to guess I would say your charge controller is not capable of high temperature environments or just so hot inside if you are using temperature compensation. 100 outside ambient temp means inside the cabinets can exceed 150 degrees.
I do a lot of work for cellular telephone companies. In very remote locations in the Desert SW (AZ to TX) they use solar PV and outside cabinets. We have to use cabinet air conditioners to keep the equipment cool and operational.MSEE, PEComment
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Unfortunately air conditioning is out of the question in this application. There is barely enough room for the two panels and the enclosure in this location. I did install an 80 CFM fan this morning to help push more air through the enclosure. This is in addition to the two smaller fans blowing directly on the heat sinks of the repeater equipment and charge controller. These fans have a combined draw of less than 0.3A so they shouldn't have much effect on the PV system.
The repeater has a max draw of 2A. The batteries are 2 Trojan J185H. Since the maximum that the panels can put out is only 5A (under absolute perfect conditions, and including edge of cloud effect), I'm wondering if I can do without a charge controller and just have a diode in-line to prevent back feeding into the panels?Comment
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OK I think I can determine what the problem is real quick. You have a 24 volt 225 AH battery being charged with only 5 amps for a couple of hours per day. Just guessing you are using a PWM charge controller and 2 110 watt panels wired in series correct? Or using a MPPT charge controller with two 70 watt panels wired in series?
What I am trying to say is your panel wattage is grossly undersized and not able to fully recharge your batteries in a day. You batteries are in a deep discharged state, and you do not have enough panel wattage. Just in fan power alone you are burning up 200 watt hours every day or 8 AH hours @ 24 volts. That is about half the energy your panels are producing each day. Your radio consuming 5 amps works out to 2880 watt hours per day.
So here is the bottom line. You radio and equipment burns 3 Kwh per day, and your panels only generate about 500 watt hours per day. To do this you rpanels need to generate 6000 watt hours per day if using a PWM controller, or about 4500 watt hours per day if using MPPT. So if i assume you are in say LA area and using a MPPT controller you would need a 1200 watt solar panel and a 60 amp charge controller.
Try reading this Sticky Thread as it will help you out quite a bit because it is based on exactly what you are trying to do. .MSEE, PEComment
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Thank you for confirming my suspicions. Because this system is supposed to be pretty well hidden from view, I'm going to have an interesting time trying to add more panels.Comment
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You are welcome. As soon as you gave some details it was crystal clear what the problem is. Physics suk in the real world.
Since I am a ham and lot of experience in commercial radio operation I am curious what your application is? Internet provider? Trunked radio? What?MSEE, PEComment
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800MHz cell phone band for voice and data.Comment
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For your personal use? Just be aware they are prone to cause interference for cellular carriers which is easily detectable and traceable. So wat I am saying is if your repeater causes interference to the cell phone carrier they will find you. They have the equipment and trained personnel that specialize doing just that. Mobile ones are tougher to trace because it is a moving target. Stationary or fixed repeaters only takes minutes to locate. I will give you a hint. They send out a special code to turn on the GPS receiver and broadcast your location. It is built into every cell phone for 911 service.MSEE, PEComment
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All business class hardware meant to extend vital communications along a dangerous and remote stretch of highway.
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OK you are just repeating a sector off a nearby cell site in a hole with bad coverage. If you give me the location like a zip code I can tell you exactly what is required. But you are looking at a 3 Kwh/day system. Your battery is also grossly undersized. At 24 volts mission critical you are looking a 800 to 1000 AH. I do this for a living for all the major Telco'sMSEE, PEComment
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