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RE: Eco-worthy 20a MPPT controller
Will an AC load through an inverter not accomplish that? Or are you looking for constant amps? I find a light bulb through an inverter to be a very steady load indeed. I have 250 watt heating lamps that work well.
Jim
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HiTech
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05/19/13 09:09pm |
Tech Issues
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RE: De-winterizing question
Don't forget after dewinterizing you need to sterilize your system - typically a soak of the whole system with the high chlorine water ( I let mine soak for 24 hours) then flush it again. Far better to do it at home IMO.
Jim
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HiTech
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05/19/13 09:02pm |
Tech Issues
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RE: De-winterizing question
Pump works fine with them open. I blast all the water out them at the house. My tank has a fresh water drain though that gets 99% of everything out of the tank. Probably more than the pump does. I run water in and drain out there to clean the tank. Then I use city water to flush the rest of the system.
Jim
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HiTech
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05/19/13 08:22pm |
Tech Issues
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RE: Best surface for tires to sit on for extended periods?
Sitting unused is harder on them than the particular surface type. When tires are in service the sidewall flexing moves plasticizer around, including to areas where it has leached out or degraded due to UV.
Jim
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HiTech
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05/19/13 06:07pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
Potentially yes but I think I would need a little different power supply. It would have to be adjustable constant voltage, but still be able to pull down the PVs on the input as you vary the voltage like this one. The voltage jumps all around based on changes in condition and I have to rescan with the pot to find the power point, even if it is at the same voltage, with a new pot position.
With 3 out of the 11 Unisolar segments covered in building shade, the Vmpp for panel output has dropped to under 13v, to just a couple of tenths above the battery voltage. I think the fast MPPT scan times for optimizing power on partly cloudy days has some merit. I had wondered if it was just marketing hype but I can see it mattering under some conditions.
If you get the set voltage even a little too high, output plummets as the IV curve suggests. If you get the voltage a little low, you pay hardly any penalty at all.
Jim
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HiTech
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05/19/13 05:02pm |
Tech Issues
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RE: Battery Water
What are your local temps? It is warming up here. Warmer temps plus a little too high float voltage from the converter (check and report voltage as requested above) will waste a lot of energy and use a lot of water. I am guessing the rig is plugged in at home?
Jim
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HiTech
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05/19/13 04:19pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
A inverter is a constant wattage load which works fairly well.
Jim
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HiTech
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05/19/13 04:16pm |
Tech Issues
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RE: Batteries One or Two
Potentially one starting or hybrid battery. Lots of amps and very few amp hours. Do you have a healthy starting battery in a vehicle you could swap over and replace with a new battery?
Jim
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HiTech
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05/19/13 04:11pm |
Tech Issues
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RE: Batteries
If the house batteries are at 13.7 they are being floated (a little aggressively) by a working converter. Should be able to use them to start the genset or the motor (with the jumper switch).
The poor chassis battery has not seen any charging in a long time, it sounds like.
Jim
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HiTech
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05/19/13 04:09pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
The you tube video early in the thread pointed out the temp sensor in the case. I've seen the controller drop the amps from 12 to below 6 when the case heated up in direct sun and bring them back up once it was placed in the shade and cooled down. Too bad i didn't have a DVM on the battery to see what happened to the volts at the same time.
I would seriously consider remoting this sensor to a battery terminal. On my PWM controller it improved the behavior, dropping back charging volts as the battery warmed up.
Any empirical data on how much voltage drop per degree the sensor buys you?
Jim
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HiTech
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05/19/13 03:58pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
Did some testing today. (sorry for the data not being aligned- don't know how to post formatted text).
Setup:
45W 12V Solar Blvd panel with these specs
Maximum Power Voltage (Vmp): 18.0V
Maximum Power Current (Imp): 2.5A
Short Circuit Current (Isc): 2.73A
12V 35AH SLA battery which I depleted about 75% yesterday
Watt's-up meter in-line with the battery to measure current INTO the battery, battery voltage, and watts into battery.
DMM to measure the solar panel's voltage at the input of the MPPT controller.
I have Deans Connectors between the watts-up and the MPPT controller and between the solar panel and the MPPT controller so I can easily unplug things and make changes.
Testing: What I did was measure the current going into the battery if the MPPT controller was "in-the-loop", and then connected the solar panel directly to the battery. With the Deans connectors, I could do this switch around in seconds.
Here are the measurements in order they were taken (if no measurement listed - then I forgot to write it down)
With the MPPT "in-the-loop"
Solar V Batt A Batt V Watts
16.76 3.08 12.51
17.00 3.05 12.51
Solar direct to battery
Solar V Batt A Batt V Watts
2.89 12.50V 35.5
With the MPPT "in-the-loop"
Solar V Batt A Batt V Watts
17.05 3.02 12.51 37.4
16.94 3.07 12.52 37.1
Solar direct to battery
Solar V Batt A Batt V Watts
2.93 12.51 35.7
The battery voltage and watts were from the Watt's-up meter - it has uncertainty in its measurements hence the watts reported are not exactly that calculated just doing the math.
I'm a bit disappointed to not have a much greater charging amps (only ~ 0.1A greater) given the delta between the battery and the panel is about 4V. Thinking that I may just be so low in power that I'm not in a high efficiency zone for this MPPT controller.
Putting my ear to the MPPT controller, I hear a regular 'ticking' noise. Will at some point drag out my digital scope and take some measurements to see what is going on.
It would be worth running your battery down to 11 volts or so and running similar tests.
Jim
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HiTech
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05/19/13 03:56pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
Testing with a 75 watt lightbulb directly hooked to the buck converter output, no dice. It works as expected. The load cannot pull the solar output down more than a few tenths away from Voc.
Trying with a 1500 watt resistance heater it is better, but still cannot get down to Vmpp, much less below to be able to scan back and forth for the Vmppt.
I'm back to the 700w inverter and an old battery. I have about 400w of load. It is very jumpy, going from 18v out of the panel to 14v very quickly. In addition the setting on the pot jumps around with any minor change in light, especially even thin clouds. It appears the panel max output is closer to the theoretical Vmpp of 16.5v +/- .5v, while the Max output of amps & watts from the buck converter into the battery is closer to 14.5-16.0 v at the panel, as observed yesterday.
Collecting more data.
Ok it has to be the varying efficiency of the buck converter. At the moment max panel output is at 16.2v +/- .1, but max amps into battery are at panel voltage of 14.8 +/- .2v. Panel temp averages 126F.
There is some loss of low light performance with this set up. In 100% building shade where all the lighting is indirect I get .42A panel direct, or 10% of panel direct full sun output. With the buck booster in the circuit and adjusted to the MPPT (14.9v) it is only getting .38A. So a 10 percent loss of available shade power, but only 1% of normal output. It would not surprise me to see a similar loss through the PWM controller though at those power levels.
Jim
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HiTech
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05/19/13 03:00pm |
Tech Issues
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RE: Eco-worthy 20a MPPT controller
Derate is all you need it to do. Very handy if it is functional.
Jim
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HiTech
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05/18/13 09:38pm |
Tech Issues
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RE: Atwood RV Furnace keeps tripping 10amp breaker
There is a DC 10 amp breaker?
Jim
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HiTech
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05/18/13 07:45pm |
Tech Issues
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RE: It works! Manual MPPT controller v2.0
Additional info in the old manual MPPT thread here.
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HiTech
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05/18/13 07:23pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
Sal that is compared to panel direct. I am pretty sure it is accurate. Sun is strong here and it was over 90 degrees. At 16.5v the panel still generated good power, but most of the day the max power point found manually was between 14.5v and 16v. It was not a crystal clear blue day though there were only a few thin clouds. I bet under standard test conditions the max power point really is 16.5.
The panels were almost scalding to the touch, but the Unisolars are not supposed to drop much until temps are quite high. I will take some temp readings tomorrow.
I was pleased that where I normally get high 3's to just over 4.0 amps into the battery from just one panel, I got over 4.5v in for many hours. Panel direct to the batteries yielded substantially similar results to my PWM controller. I imagine if measurable the buck booster would have been just slightly better vs PWM compared to panel direct, just because of voltage drop losses through the FETs.
Jim
On last edit, I was maximizing amps *to* the battery though. Not watts *from* the unisolar. So the buck booster efficiency table comes into it. I have a watt hour meter at the buck booster input as well as into the battery so I can check max power generation from the panel vs. max power to the battery. The power supply efficiency line is not linear.
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05/18/13 07:21pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
It is not to be left alone for sure when close to the max power point. I had to adjust every 30 minutes at times. But I got in excess of 10% higher amps into the battery than ever through my PWM controller. So I count the original as a fail, but the buck converter as a success. It is indeed a manual tracking MPPT device. I found my real Vmpp to be between Vmppspec and Vmppspec -2v. I think I could have set it at about 1.5 V below Vmppspec and left it all day and still been almost 10 percent higher yield than PWM, with no power point tracking, just panel output power offset from Vbatt. The biggest benefit seems to be decoupling from the battery voltage rather than the exact maximum power point.
Jim
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HiTech
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05/18/13 06:30pm |
Tech Issues
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RE: McGyver stories
Ok that is great to know. I have heard of using duct tape, but gorilla tape or eternabond are probably much stronger.
Jim
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HiTech
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05/18/13 03:13pm |
Tech Issues
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RE: Initial test manual home brew $8 MPPT controller
Well to close this out, using a $10 buck booster, it works!
Jim
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HiTech
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05/18/13 02:54pm |
Tech Issues
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RE: Back from the CAT scale
Sure have. Usually the front tires are too aired up when i feel the same in an RV. Remember the front end is lighter than empty when towing so you have to drop air pressure a little. Otherwise the contact patch is too small and you know from racing why that is bad. I would go a few psi below door sticker or better yet by the wheel weight on the tire chart for those front tires.
Jim
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HiTech
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05/18/13 02:18pm |
Tech Issues
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