-_- 32cells 15.9 volts in the garbage ?

mike95490 · December 2018

If you are going to live with the shade on the panels, you are going to have to have lots of generator run time to keep batteries alive.

Not sure why / where BB said to put diodes on the panel wires. I think if you can find panels with lots of bypass diodes built into them, that could possibly help. But shaded panels don't "suck" power away from fully illuminated panels, they produce the same voltage with nearly any amount of illumination, it's the amps that increase as the light gets brighter. That's how virtual tracking works.

The power lost in diodes has to be dissapated with heat sinks, so using your numbers, each diode needs a heat sink good for about 2 watts. if it's insignifiant to your production, no problem, but diodes overheating and failing, will be a problem, because failed diodes short out, and then if there is enough power - fuse open. in the case of a solar array, not enough power to fuse them open, so they will silently fail shorted, if they don't have proper heat sinks

BB. · December 2018

I suggested no diodes for a 12 volt system... However, he should use a fuse per parallel connected panel--But diodes have been used in times past as an alternatives for fuses (But as you say Mike, diodes can fail open or shorted--Not really an acceptable replacement for proper fusing/circuit breakers).

The blocking diodes are there to block the solar panels from (slightly) discharging the panels at night (something that modern solar charge controllers take care of automatically).

-Bill

KhellSk · December 2018

BB. said:

I suggested no diodes for a 12 volt system...i dunno what to tell you guys because ive seen an increase in my voltage since i installed them. Voltage i need to charge the last 30% of the battery. ( it was my initial problem for this thread, i couldnt get past 12.4)

If you rememver the panels were facing SE and had them at 21° which was a mistake since im in the forest. Ill add pictures of what we built today. Now all 32cells are facing full south at 45° and are on hinges so I can bring them to 68° during summer.

I just need to figure out what to do with the 36cells 100w. I like to keep it butbi read on an other thread it might not be a good idea to have a panels facing annother direction

KhellSk · December 2018

I just looked up where arizona is. You guys are way down south on the mexico border almost on the pacific shore. Ahah. Im in Canada close the east coast in the appalachians xD

I bet its more simple for solar over ther

jonr · January 2019

In that area and this time of year, you want about 65 degrees (25 less than vertical). Due south unless you have good reason to do otherwise.

NANOcontrol · January 2019

If you have an increase in voltage with the diodes, you may have a very leaky panel.Or it just got a way lot colder outside. Actually, it could could be possible to solve this problem in the summer and use a PWM with a cheap ebay boost or buck converter. Depends if the panels are in series or not. Set the output voltage to the maximum voltage needed to charge the batteries. This would only be a couple volts more. I'm doing this right now heating water from a 30V panel to 80V on a water heater at power point. I've been going to write a how to making any cheap PWM controller into one that performs nearly as well as a MPPT model for only a $10 outlay.

KhellSk · January 2019

NANOcontrol said:

If you have an increase in voltage with the diodes, you may have a very leaky panel.Or it just got a way lot colder outside. Actually, it could could be possible to solve this problem in the summer and use a PWM with a cheap ebay boost or buck converter. Depends if the panels are in series or not. Set the output voltage to the maximum voltage needed to charge the batteries. This would only be a couple volts more. I'm doing this right now heating water from a 30V panel to 80V on a water heater at power point. I've been going to write a how to making any cheap PWM controller into one that performs nearly as well as a MPPT model for only a $10 outlay.

Whats aleaky panels and how do you find which ?

BB. · January 2019

Solar panels are really just giant diodes. When you connect a 12 volt battery to a 12 volt solar panel, the solar cells (diodes) will at night, leak a little bit of current from the battery back through the panel (discharge the battery bank).

Older panels, panels with problems, etc. can have higher leakage current at night and significantly discharge the battery bank.

In the old days, people would use 32 cell panels and blocking (series connected) diodes to reduce the the reverse current flow ("real diodes" have lower leakage current).

Today, we use 36 cell (or higher voltage panels for 12 volt battery systems) and s solar charge controller that turns off the solar panel to battery bank connection at night, and greatly reduce leakage current.

HOWEVER, solar charge controllers do use some battery current at night... Simple PWM controllers use less, and large MPPT controllers (with internet connections etc.), can use a fair amount and actually discharge the battery bank itself over weeks or a few months (i.e., if solar panel breaker is opened, snow over panel, etc.).

-Bill

KhellSk · January 2019

@BB. @mcgivor @littleharbor2 @Photowhit

Guys. I think this is a success. I know lots of people made it sound like it wasnt gonna work and you probaly doubted it yourselves.

But today was a clear sunny day, with my new racking facing south at 45ish degrees. All 32 cells having blocking diodes. The 100w 36cells wasnt even plugged in!!! From 12.3 last night, Ive reach 13.6 around 11h30 slowly going to 12.9 (2pm).

Im well aware that its not optimal like in arizona or just plain out in a field but Im really optimistic about the increases in voltage. This confirms that my angle was too steep for the forest and having the panels facing SE @ 20° was really costing me.

Now my only problem left is amperage being halved. @BB. says its normal during winter time here on the 45th parallel. I ll just add a blocking diode the the 100w panels and this should put me around 9amps... till luminosity gets better.

Anyway I couldnt have made so much progress without your help. Thank you very much.

*** update, sun has set 2 hours ago and battery really is full.

NANOcontrol · January 2019

Seeing and believing are often both wrong. FOW

A blocking diode is just not going to increase output. Do you block each panel or use a single blocking diode? Your setup should be fine in the winter. It is summer when the solar panel voltage drops with temperature. You bought unknown used panels. I recently had a lightning strike and several bypass diodes went bad. Testing, remove any individual panel. If output goes up on system the panel is drawing current.

KhellSk · January 2019

NANOcontrol
Seeing and believing. I dunno what you mean but it works while it didnt before i do those changes. Was cloudy af again today and made it to 13.4v. I couldnt even get past 12.4 then.

Dont worry brother i tested them before buy them last summer.

All in parallel, added a blocking diode to each one

BB. · January 2019

You still want to get (ideally) closer to 14.75 volts (~75F), or at a minimum of >14.2 volts for multiple hours per day (several time a week).

-Bill

KhellSk · January 2019

BB. said:

You still want to get (ideally) closer to 14.75 volts (~75F), or at a minimum of >14.2 volts for multiple hours per day (several time a week).

-Bill

yeah but it was cloudy today all day. Even then i managed to go from 12.3 to 12.7v(after few hours of dark) battery is full at least an wont freeze or sulphate. Thats pretty good for a cloudy day in the forest.

when im lucky enough to have a couple hours of real sun it will reach 14.2 14.5 for 2 hours then go back down to 13.7. But roght now without the 100w, it doesnt quite do it but im going to install it soon. I just re installed the 32cells 3 days ago and wanted to see how it went before investing more time. I installed a blocking diode on the 100w and gonna mount soon.

Renogy wanderer has 3 stage charge bulk, boost and float. Plus equalization every 28days.

Manual doesnt give voltage to expect but so far i figured that the float/bulk is 13.1 to 13.7v. The boost would be the 14.1 to 14.7v. And equalization 15 over.

Has to be said that Im running on the 130ah battery alone for now. If all the modification are a success I will put back the 210ah bank. Hopefully i will find an other 48w next summer for cheap to fill the 400wmp on the charge controller (1x 100w plus 5x 48w = 340w at the moment ) and get a better C-rate on my system.

mcgivor · January 2019

Read post #73 again, your batteries are not fully charged, the voltage needs to be higher, 13.7V is not a bulk value, it's a float voltage in cold climates at best, you are destroying your batteries, if they are not reaching 14.7V daily if discharged overnight. This point has been mentioned multiple times, if you don't get them fully charged, they are doomed, textbook chronic undercharging.

KhellSk · January 2019

Also, to help you understand why a system so small works for me;

I dont use an inverter. I just have a boat electric board with 12v socket, 1x dual 2amps usb (5v). I picked a laptop with a cpu from a gen that has low power requirements. I dont have a fridge or a pump. All this system is for is my milwaukee drills batteries with a milwaukee car charger (12v to 12v), laptop, cell phone, flash light and eventualy a small 9w led light bar.

KhellSk · January 2019

mcgivor said:

Read post #73 again, your batteries are not fully charged, the voltage needs to be higher, 13.7V is not a bulk value, it's a float voltage in cold climates at best, you are destroying your batteries, if they ate not reaching 14.7V daily if discharged overnight. This point has been mentioned multiple times, if you don't get them fully charged, they are doomed, textbook chronic undercharging.

I will. Thanks for making sure. It didnt before my recent changes ( it did during summer)but im pretty sure it will once i add in the 100w. It almost did it today with a sky saturated with clouds( it might have in the afternoon but i was gone). Its been dark now for at least 4 hours and its still at 12.7. Is it what you meant ??

Im not touching them tonight to see tomorow what it is at. I did this 2 days ago, it was a clear sunny day all day and it still was full the next morning (12.7) when i woke up. I never fully discharge them. I stop at 12.1 being 55%ish on my battery specs, at most. I often stop before that and the only overnight load is the pwm cc.

mcgivor · January 2019

What are the specific gravity, SG readings ? That will reveal the truth, voltage is a poor method of estimating state of charge, a battery that has little to no capacity left, can still have voltage which appears good. Do you have a hydrometer? an essential tool when using flooded batteries.

KhellSk · January 2019

mcgivor said:

What are the specific gravity, SG readings ? That will reveal the truth, voltage is a poor method of estimating state of charge, a battery that has little to no capacity left, can still have voltage which appears good. Do you have a hydrometer? an essential tool when using flooded batteries.

Do you have suggestions for brands and models for those

mcgivor · January 2019

Here is an example of what's needed, I don't have any specific brand. https://www.amazon.com/OTC-4619-Professional-Battery-Hydrometer/dp/B0050SFVHO

Tecnodave · April 2019

I recognize those rare 33 cell panels, count them again, they are 33 cells, I'd bet that they are Arco Solar M-75 panels or Siemens SM-75panels.....Seimens bought Arco Solar division and kept everything the same. They were marketed as "self regulating panels" that could not over charge the batteries. They were not meant to be used with a controller. Other manufacturers also sold "self regulating panels" some had an 8 X 4 arrangement for 32 cells. More common was the 30 cell panels, also sold by Arco/Seimens 3 rows of 10 cells. The voltage at MPP is too low to use a controller. I use some for testing but due to the low voltage they are difficult to use. Even a blocking diode has too much voltage drop to achieve a full charge. Use your 36 cell panels with a PWM controller, but connect these directly to the battery in your climate. I don't think that you will have an over charge situation in that thin Cnuk sun. Picture is old sun beaten Arco M-75's that survived Arizonz desert on a two way radio repeater

check that flaky Internet will not allow me to post that pic. I will post that later

-_- 32cells 15.9 volts in the garbage ?

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