diy solar

diy solar

1.5 Watt panel supplying power coffee grinder for my coffee grinder every morning but I need a small controller

Your adjustment steps would seem to be reasonable.

If you have capacitor that you are charging to a set voltage, so you can make adjustments, put a bleed resistor and a switch on it so you can quickly drop your "battery" voltage. Once it will charge up to your correct max voltage, keep repeating the charge cycle and monkey with the MPPT setting. Those instructions are pretty hard to follow but if you can get your charge time to be as low as possible, that would be your best setting.
 
SolarRat, Those are the directions I was talking about. I understand "bottle" means "battery" but beyond that they do not make much sense to me.

Dthames, I tried adjusting battery voltage with a capacitor connected to the battery outputs on the board, instead of the battery connected. In some directions posted by another user it mentioned to do it that way. It seemed to end up with about the same adjustment position of the trim-pot as with the two battery outputs not connected to anything.

edit: I suddenly get it about using a capacitor to time how fast it charges fully. OK, that makes sense. Sort of like measuring for the highest current ouput. Adjust the MPPT trim-pot until it charges the cap the quickest, as you described. I'll try that in the next few days. Another project has me sidelined on this one, until then.

One thing I was wondering is what if I were to set the MPPT (I'll call it input) voltage lower ? Let's say 15.5 volts instead of 18.5v. When I tried that temporarily it seemed to boost the battery voltage a tenth within a couple of minute. Maybe the battery was still recovering from when I used the grinder. I don't know.

This morning as the sun was just coming up I noticed the LED was flashing fast and only red. I have not seen it do that before now and I cannot find anything in the manufacturers description about what it indicates. I do not have enough experience with battery management systems to fully understand how they work with a single cell. I do not know for instance what happens for instance, if the PV panel is putting out too much voltage.

The MPPT adjustment trim-pot adjustment is there for a reason, I assume. I have no idea what that reason is however. Any procedure I try is a result of blind faith but I have no idea really, what I'm doing exactly.

Battery was at 12.5v before grinding this morning. It's already back to 12.5v now. The MPPT board has been connected almost 24 hours. I'm not satisfied it will ensure the best longevity for the battery unless I can adjust the MPPT board to get it to read 13.5v daily.
 
So on the charging a capacitor thing.....since you have a small panel, waiting for it to charge the battery fully could take days. If you have 3 18650 lithium ion cells, you can put them in series and charge to about 12.6v. These are small capacity and will charge faster than your larger battery. Or if you have a large capacitor, you can charge it up. But it might charge in seconds. So you want a dump button or switch so you can easily lower the voltage and watch it come up again as the charger charges it. Or if you have a large capacitor, you can also add a parallel resistor (or pot) across the capacitor and adjust it so it is bleeding just less than the charger is charging so the voltage comes up slowly. Then with adjustments you can increase the bleed load and see if you can adjust the charger to keep up and to actually bring the voltage up. If you are doing that adjustment in real time, you should be able to find the sweet spot on the charger/panel setup.
 
Just use an ammeter and adjust the input till you see the highest reading.

tirebiter said:
I'm not satisfied it will ensure the best longevity for the battery unless I can adjust the MPPT board to get it to read 13.5v daily.
Click to expand...

With a 1.5 watt panel? You better start off with a fully charged battery. Good luck...
 
tirebiter said:
Battery was at 12.5v before grinding this morning.
Click to expand...

This battery has had an unusual (sub-optimal) life for over a year? Even a brand new LA battery charged to 13.5v during the day will fall to the 12.7/8 range after an overnight rest. With an old abused battery, 12.5v after a long rest ain't bad, 12.6v would be great. How many years do you expect a $25 mower battery to last? I don't get more than a year or two out of them on my tractor in the Florida heat...

You'll get 10 years out of 3 or 4 good 18650's...in a much smaller package, with more efficient charging.
 
Get a 12V coffee grinder. Stack some diodes until the voltage is right for battery. No controller.
 
For now I'm going to leave it alone and keep using it daily. See if the 12.5 maintains or goes up or goes down.

Another project is keeping me busy for now. I'll get back to the MPPT adjustment in a few days, probably. The voltmeter was switching from 12.5 to 12.6 this morning, before turning on the inverter. Later it was reading 12.5 again.

For the record, the voltage had dropped to 12.0 by the time I was done running the the grinder.
 
DanHitch said:
Get a 12V coffee grinder. Stack some diodes until the voltage is right for battery. No controller.
Click to expand...

I am not trying to use a 12Volt coffee grinder. I am attempting to make use of this Harbor Freight 1.5 Watt PV panel to keep a lead acid battery charged to run an invertor to use the ac powered coffee grinder I have. There is a LOT to read about in previous posts in this thread.
 
I would use my multimeter to see what your adjustments are doing on the battery side of things. mainly I think you are just looking for voltage cutoffs. Im guessing its adjustable as to what the charge voltage is and what the charge voltage cutoff is. Find out what your battery is supposed to have or copy the settings from another controller. Multimeter should tell you what your adjustments are doing. Seems as if you have your charge voltage cutoff pretty low. As for the power supply. Find a household brick adapter that is over 15 volts... laptop charger should do. polarity will be on the brick but usually inside of the plug is positive outside is neg. you can also test it with a multi-meter first, that is what they are for after all. Also I want to note that you didn't use a diode because you didn't want it to eat up all your power from the panel. Then proceeded to put a bunch of diodes and transistors with a computer on the panel. I think you just really wanted a neat controller and not a solution to the problem. That's fine and a fun way to learn but the diode was your original problem with overnight discharge.
 
I was talking about voltage output from the mppt controller, not amperage, not battery voltage, not overnight battery voltage. He doesnt know how to set his mppt controller up. Get some readings amd adjust until within spec is all im saying. Use a power brick, get the battery charged and adjust controller with miltimeter, then go from there. We already know his amps arent there but charge controllers measure voltage to make decisions so you need to know what is going on when you adjust things.
 
TheDroidsYouAreLookingFor said:
I was talking about voltage output from the mppt controller, not amperage, not battery voltage, not overnight battery voltage. He doesnt know how to set his mppt controller up. Get some readings amd adjust until within spec is all im saying. Use a power brick, get the battery charged and adjust controller with miltimeter, then go from there. We already know his amps arent there but charge controllers measure voltage to make decisions so you need to know what is going on when you adjust things.
Click to expand...

I get what you were saying, and you were correct, but what I was saying is you can't fine tune a tiny, mV sensitive device with a multimeter that only reads in 100mV steps. At least not very well. And with this tiny system, every mV counts. So to follow your steps without a better multimeter would be like beating your head against the wall.
 
I mentioned previously that I have a D 811 Fluke meter. It's good to a smaller increment of voltage than the el-cheapo Harber Freight meter I leave connected. I don't think I'll see much difference by using it though but maybe it's worth a try.

For now I m monitoring it each day. So far every day is full direct sunlight aimed almost perfectly perpendicular to the surface of the PV panel for a while every 24 hours.

This morning, before grinding my coffee, battery voltage was at 12.5/12.6 flashing between the two until I turned on the inverter. Several hours after grinding, it is reading a steady 12.5 Volts. I switched the meter to a lower voltage range and it is reading 12.59 Volts.
 
Before grinding my coffee this morning the el-cheapo multimeter was reading a steady 12.6 volts at the battery. Switching to the lower scale it reads 12.63 volts. It seems to be slowly increasing the battery voltage in the full sun we have been getting since putting The MPPT board in place.

We are due for some cloudy weather in this locale, over the weekend. I'll stretch my monitoring until after the cloudy period ends. Before drawing any conclusions or attempting adjustments using a capacitor and stop watch.

edit: I just checked several hours after grinding my coffee, this morning. The battery voltage reads 12.65. Still sunny out.
 
Last edited:
TheDroidsYouAreLookingFor said:
I think you just really wanted a neat controller and not a solution to the problem. That's fine and a fun way to learn but the diode was your original problem with overnight discharge.
Click to expand...
My problem was towfold. Overnight discharge during the short hour days was only one part. The other part was too much charge during the long days. I was seeing up to 16 volts at the battery more than once this past summer, before I began disconnecting it part way through the day.

Yes that is all I wanted ... a neat controller that would take care of overcharging on long days and also prevent nightly discharging on short days. So far this MPPT board seems to be doing that, barely. I'm hoping it is a total solution to my problem. Not just a solution to the nightly discharge part of my problem.
 
Yesterday morning before grinding my coffee, the meter read 12.65 Volts. It was cloudy all day, yesterday. This morning, before the sun came up the meter was flashing between 12.65v and 12.66v.
 
It's been about 3 weeks of daily grinding and observing battery voltage. It was holding steady at about12.62/3 volts. About a week ago it dropped to about 12.57/8 volts. Fluctuatiing about 30 millivolts. Have not seen above 12.60 for about a week.

At some point I'll gear up to try resetting the MPPT board using a capacitor to gauge charging current.

An interesting sidenote. I went out and checked my car battery voltage after sitting overnight. 12.5 Volts. No problems with it but isn't 13.5 desireable ?
 
tirebiter said:
An interesting sidenote. I went out and checked my car battery voltage after sitting overnight. 12.5 Volts. No problems with it but isn't 13.5 desireable ?
Click to expand...

See my post #66:

SolarRat said:
Even a brand new LA battery charged to 13.5v during the day will fall to the 12.7/8 range after an overnight rest. With an old abused battery, 12.5v after a long rest ain't bad, 12.6v would be great.
Click to expand...
 
tirebiter said:
It's been about 3 weeks of daily grinding and observing battery voltage. It was holding steady at about12.62/3 volts. About a week ago it dropped to about 12.57/8 volts. Fluctuatiing about 30 millivolts. Have not seen above 12.60 for about a week.

At some point I'll gear up to try resetting the MPPT board using a capacitor to gauge charging current.

An interesting sidenote. I went out and checked my car battery voltage after sitting overnight. 12.5 Volts. No problems with it but isn't 13.5 desireable ?
Click to expand...
Car batteries will only be above 13v during or soon after charging... they rapidly drop the surface float charge and settle to 12.8 or lower depending on capacity degradation and load duration.
If you are reading 12.5 the battery has a large drain when parked, or the battery is nearing failure...
 
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