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

Another issue is your free Battery may have slowly sulphated to death. I mean at this point we have spoken on more solar, solar charge controllers, Diodes (including LED diode) and checking the actual current. Just to add something else to the mix I think you should upgrade the battery to LTO... (thats a joke) But really if battery voltage drops off right after the sun goes down or quickly after the panel loses sunlight the lead acid battery might be heading out to pasture so to speak. I personally hate motorcycle, lawn tractor and all those other expensive low capacity batteries that fail every winter on my motorcycles, sometimes even with a tender. I also think that the LED might have been whats called a "blocking Diode" they are used in solar panels so your panels don't become resisters overnight. I think someone was alluding to that above.

Supervstech said:

150 W divided by 5 (20 seconds of a minute) is 30W/minute I skipped a step... my bad. 1.5W outputting for 6 sun hours is 9Wh, or 540Wminutes... plenty of power.
Carry on. Ignore me.

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And my math still sucks...

Should divide by 3... so 50 W/minute... still nowhere near what the 1.5W panel should produce in an average day.

150wh/60 minutes = 2.5w/m /3 = 0.83 watts per 20 seconds. I think he's over-paneled .

TheDroidsYouAreLookingFor said:

I think someone was alluding to that above.

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Good catch.

DThames, Yes, with no controller and no Blue LED, I have used the grinder every day with adequate battery power. No sign of it slowing down in the 20 seconds it is running.

What I'm worried about in fact is the way the battery is being "Exercised". I think it's running through deeper discharge cycles than necessary with the steady night-time drain and then pushing the enevelope so-to-speak as far as overcharging during peak hours.

Battery life is my main concern. The system has proven so far to be reliable. No sign of slowing down after one year of operation. I'd like to be able to run a smaller battery.

SolarRat said:

150wh/60 minutes = 2.5w/m /3 = 0.83 watts per 20 seconds. I think he's over-paneled .

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I dont think your math is right...

It is, it's just incorrectly worded.
And it is roughly saying the same as I was.

9Wh panel will produce far more solar power than a .83Wh draw

tirebiter said:

DThames, Yes, with no controller and no Blue LED, I have used the grinder every day with adequate battery power. No sign of it slowing down in the 20 seconds it is running.

What I'm worried about in fact is the way the battery is being "Exercised". I think it's running through deeper discharge cycles than necessary with the steady night-time drain and then pushing the enevelope so-to-speak as far as overcharging during peak hours.

Battery life is my main concern. The system has proven so far to be reliable. No sign of slowing down after one year of operation. I'd like to be able to run a smaller battery.

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As I was saying above, the diode in that blue LED should stop the panel from draining your battery overnight...don't bypass that diode.

150

tirebiter said:

DThames, Yes, with no controller and no Blue LED, I have used the grinder every day with adequate battery power. No sign of it slowing down in the 20 seconds it is running.

What I'm worried about in fact is the way the battery is being "Exercised". I think it's running through deeper discharge cycles than necessary with the steady night-time drain and then pushing the enevelope so-to-speak as far as overcharging during peak hours.

Battery life is my main concern. The system has proven so far to be reliable. No sign of slowing down after one year of operation. I'd like to be able to run a smaller battery.

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I would get a decent LFP battery and use that.
I don't mean a battleborn obviously... I mean a cheapo pack of 27650 or 32650 cells and a bms an average 6mah pack will give you 84Wh storage, you need... 1Wh tops per day.

The cheap 1.5mah cells would even handle it... and last forever...

Where do you live?

The problem with going with a much smaller battery is you have to make sure it can handle the surge. 150w @12v is 12.5 amps, but figure 15 amps with inverter losses. Your mower battery is probably about 18ah, so it is drawing just under 1C, no problem. If you move to say a small 3ah battery you have to make sure it can handle 5C.

I strapped three of the red laptop cells to the back of this spotlight. They are 2600mah (2.6a) and can power the 6w LEDs for 5 hours. BUT, they would choke if used with your 150w load. Laptop batteries have low C limits. Now, if I used the 3 amp pink Samsung cells (designed for high drain, like for power tools and vape pens) instead it would handle your inverter since they are rated at 20C. They look the same but are very different.

A 3ah lead acid probably won't like a 5C load. Neither will some LFP/Li-ions...you just have to choose the right cells. An old 4ah 12 or 14.4v power tool battery might be perfect, and it should already have some BMS/limiting circuitry built in.

SolarRat,

There is a small circuit board the blue LED is on along with a couple of other electronic components. At least one capacitor and a resistor as best as I can remember. I'll see if I can get a photo of it for you, from one of the new ones.

I am located in Southern New England, USA. About the same Latitude as Toronto Canada.


When I selected the 400 Watt inverter. It seemed reasonable to plan on a 3:1 surge current at startup. The low mass of the small diameter motor and spinning blade apparently have relatively low inertia to overcome. The startup draw is a lot less than the 7:1 that I had been considering before getting the clamp meter. 350w at startup is about it for less than a second, I believe.

This may be the first and only time I'll ever recommend a starting battery over a deep cycle for solar use, but your "20 seconds a day" use is out of the ordinary, requiring just a quick high C burst and no sustained draw.

I have one of these tiny things in my small Yamaha. I bet it could handle your surge usage...

tirebiter said:

DThames, Yes, with no controller and no Blue LED, I have used the grinder every day with adequate battery power. No sign of it slowing down in the 20 seconds it is running.

What I'm worried about in fact is the way the battery is being "Exercised". I think it's running through deeper discharge cycles than necessary with the steady night-time drain and then pushing the enevelope so-to-speak as far as overcharging during peak hours.

Battery life is my main concern. The system has proven so far to be reliable. No sign of slowing down after one year of operation. I'd like to be able to run a smaller battery.

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I just wanted to make sure I understood and yes that Zener would be a very simple and easy way to avoid a controller and limit the battery voltage. As for a smaller battery, a pack of fairly high current Li-ion or LiFeP04 should work great. I bet 4 of these cells would work great.

TheDroidsYouAreLookingFor said:

Another issue is your free Battery may have slowly sulphated to death ...
... if battery voltage drops off right after the sun goes down or quickly after the panel loses sunlight the lead acid battery might be heading out to pasture

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I bought the battery brand new. This solar powered coffee grinder has been it's only use. I never put it on a battery charger before use.

Another tid-bit of info follows. I am learning what information is required in this discussion:

It's a 240 ah battery. Voltage does not change very fast regardless charger connected or not, sunlight or not.

Turning on the inverter drops it suddenly and using the grinder makes it drop as suddenly and even moreso. When I'm done grinding and shut off the inverter, the voltage suddenly goes right back up to around 0.5v less than before use.

It sounds like everything is working as intended. For some reason i thought it was a used battery. 240 amp hours of battery @12v is really large compared to your charging and load though. For comparison a powerwheels jeep has just under 10 amp hours @ 12 volts and is used for an hour or 2 at a time... you may need larger solar just to fully charge the battery as your losses will start to add up from internal resistance. Are you sure its 240 Ah and not 24? 240 amp hours of lead is like the size of 3 gallons of milk...

SolarRat said:

... your "20 seconds a day" use is out of the ordinary, requiring just a quick high C burst and no sustained draw

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Precisly SolarRat. In other words, it has all day to recharge which is why I figured the tiny PV panel would be enough.

I had to disable the built-in control circuit because of the distance from the panel to the battery. The long wires apparently offer enough resistance to adversely affect the charger's ability to do it's job.

I pondered over putting the battery closer to the panel and using shorter wires for "low power" PV panel supplied amperage, to the battery. That would mean I would have to use long, heavier wires to supply battery + volts and carry "higher power" amperage to run the inverter when the grinder was in operation.

I also wondered about wiring up a remote on/off switch for the inverter and using a long extension cord to plug the grinder into. That would keep the wires carrying"higher power" amperage between the inverter and battery short. It would also add a long 110 Volt extension cord to run the grinder off of and another length of wire to the inverter circuit for the on/off switch. Never mind the complication of adding the remote switch.

Neither of these other two schemes seem as desirable so I went with the long wires carrying "low power" amperage to the battery.

Droids, VERY good catch. It's 240 cold cranking amps. Not 240 ah. Doh !!!

I just took another look to verify. Another correction. 230 CCA. Not 240 as reported. Guessing a little over 30 ah. 230/7.25=31.724. The constant , 7.25 being used to derive approximate ah from CCA.

Battery Voltage today is reading 12.4 with PV panel leads connected or not. It's been cloudy for a couple of days. Open circuit at 19.7 volts with heavy overcast/cloudy sky.

I bet the battery is sitting at minimum charge.
12.4 is quite low on a la cell.
Do you have a bulk charger you can attach to the battery? Or could you take it to an auto parts store or walmart to test? They will fully charge it first free...

If it isnt showing correct cca ability a new one may be needed.

35ah SLA battery from harbor freight would be about 60 with coupon...
Lead batteries need a good surface charge amperage if they get used... the 1.5w cell may not be able to do that.

Another good reason to use a bank of LFP cells...
If you were close I'd put something together for ya that would work better, and test your solar output etc...

Get 4 of these for $27 total. You can screw them together and put ring terminal wire attachment on each end, $10 BMS, and you are done. $4 charge controller if you like.

I assume this is just a "just to see if I can do it" type project. If so you succeeded. Now, I wouldn't spend much time or money improving the design, I'd get a bigger battery, bigger panel and bigger inverter. Then, you could not only grind your coffee beans, you could brew them too! Everything will get easier as you have more buffer to work with....