-_- 32cells 15.9 volts in the garbage ?

KhellSk

Lots of guys helped me out lately and made me realize my 15.9v panels were 32 cells. ''why didn't you count them then'' you ask. Well I'm an idiot. 

Now to my questions. Someone pointed out than those 32 cells panels have a hard time charging 12v batteries because they need optimal conditions to reach a voltage high enough to actually charge the thing. Now I feel like an idiot even more because i have 5 of them and 1 legit 36cells 17v.... 

its often cloudy here meaning that 3/4 of the time they are close useless, well if I understood that right.

So I'm now thinking if I should just put them on a separate charge controller all together, buy an other legit 36 cells panel or 2, put them with the one I already have on the charge controller i already own ( 12v only, 30a PWM 400w Max). Or maybe chuck em in a bin somewhere. With the knowledge I have now, it makes more sense to me, but again I feel like an idiot so I would like you guys input on that, so far y all been greatly helpfully.

Photowhit

Those were sold as being safe to connect to 12 volt batteries without a charge controller, the theory being they would not have a chance to reach high enough voltage to over charge the batteries. They aren't junk, but I wouldn't connect them that way. MPPT charge controllers keep coming down in price, maybe at some point it would be worthwhile connecting them 2x2 for 12 volt charging, or a string of 5 for 24 volt charging.

Estragon

What's the max voltage on the pwm controller?

BB.

Don't worry about buying 32 cell panels... They are pretty rare these days except for specialty applications, so it is pretty understandable what happened.

In anycase, I am pretty sure that pretty much everyone here has been through a couple of courses at the school of hard knocks.

For now (during winter), just put the lower voltage panels wired directly to the battery bank... Use a fuse+switch or a circuit breaker for the rated current (i.e., if 12 amp rated Imp for the panels, multiply by 1.25 fudge factor = 15 or 20 amp fuse/breaker and 14 AWG--15 AWG or 12 AWG--20 amp circuit minimum--Larger wire will not hurt anything, and will help if you have long wire runs). Leave the switch on during winter (circuit breaker can replace fuse+switch, your choice--Put fuse/breaker near battery bus to protect wiring out to the array) and check the battery bank voltage/specific gravity.

During summer, check the battery bank voltage (not over ~14.8 volts or so when charging), or >~1.265 specific gravity--roughly on a sunny afternoon). This is a "manual charge controller" and I don't usually recommend that ("manual" is just a trip point==when you forget and "toast" the battery bank.

In this case, because these are lower voltage 32 cell panels, they should not toast the battery during normal operation. And you always have the switch (or the option of adding a cheap PWM controller for those panels--if needed).

-Bill

KhellSk

Estragon said:

What's the max voltage on the pwm controller?

400w 

KhellSk

BB.

For now (during winter), just put the lower voltage panels wired directly to the battery bank... Use a fuse+switch or a circuit breaker. Leave the switch on during winter


Pretty sure a charge ctrl gonna cost me the same money as a small breaker box would. Tho a simple line fuse holder, 15amp fuse. But i would need a 30amp light switch. Pretty those arny cheap. while its 40ish for chrg ctrl.


During summer, check the battery bank voltage (not over ~14.8v). This is a "manual charge controller" and I don't usually recommend that. Because these are lower voltage 32 cell panels, they should not toast the battery during normal operation. And you always have the switch

you ld be confortable enough to leave for a work shift without a Chrg Ctrl ?(with those 32cells panels )

KhellSk

Photowhit said:

Those were sold as being safe to connect to 12 volt batteries without a charge controller...They aren't junk, but I wouldn't connect them that way.

which way ? W/o a chrg ctrl or the way i suggested, on a secondary chrg ctrl on the same batteries?


MPPT charge controllers keep coming down in price, maybe at some point it would worhtwhile.

I cant pretend i know what a mppt would accomplish more if the voltages cant reach decent enough voltage to charge with a pwm.

mcgivor

With a MPPT controller it would be possible to connect the 32 cell panels in series to achieve ~31.8V,  the MPPT controller will down convert this to the voltage needed to charge the battery, at the same time the excess voltage is converted to increase the current, read this link, it will answer many questions you may have. Be aware however there are some cheap imposter versions of "MPPT" controllers which do not work as described. 
https://www.solar-electric.com/learning-center/batteries-and-charging/mppt-solar-charge-controllers.html 

BB.

What was the amp*hour rating of your battery bank?

What type of batteries? Flooded cell, AGM, car battery?

Bill

KhellSk

mcgivor Photowhit said:

Mppt  would work great as long as I can find one both quality enough but cheap enough to justify buying for for a ridiculus 240 watts.

 I ld have to take off the 36 cells and use it somewhere else. Put the 5x 32cells in series.

One issue tho. For the life of me i cannot find a website with schottky(germanium made) diodes for bypass in Canada. Theres Mouser website but i got more confused than anything. 

I know i want them to have around 0.4v foward barrier and could also whistand the total Isc of the panel(s). And also a reverse voltage rating higher than the total Voc of the panels.

But Bill just mentionned on an other post that those damned thing need their own insulation even to just install them i wouldnt know how to and where to put them. I wish they made simple inline sockets with wires on both sides like for the fuses.

KhellSk

BB. said:

What was the amp*hour rating of your battery bank?

What type of batteries? Flooded cell, AGM, car battery?

Bill

2x flooded Trojan 6v 210ah in series
 inside an insulated wood box outside

Had first bought a trojan 12v 130ah thinking i was gonna be fine, upgraded thinking more storage would help but you guys made me realized that my 32cells just wouldnt cut it when it comes to charge the last 30 35% of the battery.

 Oh well i have better storage now. If only i could get those panels work better. @Mcgivor and @Photowhit have a good idea. I just need a Mppt charger worth buying for 240watts system. 

And if I do i need to find good bypass diodes and how to put em in

BB.

It does depend on what diodes you specifically get (some are simple two axial lead devices, others are the "transistor" case with a metal tab that is to be bolted to an electrically insulated heat sink.

Assuming your battery bank is of reasonable size with a flooded cell battery bank, I would not be worried about one day of "uncontrolled" charging... But you could also do the test on your day off (when you get a bit of sun).

Say you have 2x 6 volt @ 200 AH golf cart batteries (Flooded cell, water level above the plates, and 1/2 way up the chamber--Do not fill right to the brim... That could cause electrolyte to run out the top of the cell as bubbles form during charging/water gets warm).

• I have 5x 48w panels = 3.02A 15.9V rated ( 3.35a 19.8V max)
  
• 5 * 3.02 amp panels = 15.1 amps
• 15.1 amps * 1.25 NEC derating for wiring/breakers = 18.9 Amps--Round up to 12 AWG cable (minimum) and 20 Amp fuse/breaker
• 15.1 Amps charging / 200 Amp*Hour battery bank = 0.076 ~7.6% rate of charge

Nominally, I would suggest 1% or less rate of charge for long term float charging. And >2% rate of charge you should use a charge controller for long term float charging.

Assuming your battery bank is discharge somewhat before charging (not just floating for days/weeks/months at a time).... I would not worry too much about 1 day unattended at 10% or less rate of charge--Especially since this is a 32 cell panel.

Just make sure your batteries are, at most, lightly fizzing (not a "boil" from gassing), and the temperature is less than 120F maximum (lots of gassing/boiling and high temperatures are hard on batteries--That is excessive "equalization charging").

-Bill

KhellSk

BB. said:

• 15.1 Amps charging / 200 Amp*Hour battery bank = 0.076 ~7.6% rate of charge

Wait i have 2x 210ah. Dont they add up ?

Did i mention Im an idiot... i spent 500bucks thinking i was almost tripling my storage capacity. Glad I finaly found you guys xD

BB.

You are correct KhellSK.

I tend to not remember names+system configuration very well (names are just not in my wheelhouse). So, I just used a generic example.

In your case, you have 2x 12 volt @ 210 AH batteries in parallel, so you have a 12 volt @ 420 AH battery bank... And my above calculations for your system would be:

• I have 5x 48w panels = 3.02A 15.9V rated ( 3.35a 19.8V max)
  
• 5 * 3.02 amp panels = 15.1 amps
• 15.1 amps * 1.25 NEC derating for wiring/breakers = 18.9 Amps--Round up to 12 AWG cable (minimum) and 20 Amp fuse/breaker
• 15.1 Amps charging / 420 Amp*Hour battery bank = 0.036 ~3.6% rate of charge

So, even less chance of damaging your batteries from 'overcharging' with your 48 watt panels (in parallel).

For now, I would just connect your 48 Watt panels in parallel (in theory, you should have a ~5 amp fuse in series with each panel to prevent a shorted panel from getting too much current from the other panels (sunny day) or being fed back from the battery bank (any time).

Me, if I was cycling the batteries more or less daily, I would not worry about your 48 watt panels overcharging the battery bank, especially during winter.

Assuming these are flooded cell batteries--Just monitor the water levels (refilling every 1-3 months is normal for typical deep cycle battery), and monitoring specific gravity and battery voltage (basically 13.8 thru 14.8 volts is "charging", and a resting battery--no charge/no discharge is around 12.7+ volts for 100% state of charge).

When spring comes around and you have lots more sun--You might keep a closer eye on the system to make sure you are not overcharging with the 48 Watt panels (i.e., turn off the switch for a day and see how things look).

Eventually, you will probably need to do something else (rewire panels, charge controller, new panels+charger controller, etc.).

If you wish, you can put a "signature" on your post. Click on your name and navigate or click on this link to create/edit your signature:

https://forum.solar-electric.com/profile/signature

-Bill

tabbycat

On boats fuse holders in battery boxes have to be ignition protected. Fuses are considered an ignition source. It might be a good idea on land also. Check the Blue Seas website.

KhellSk

BB. 

In your case, you have 2x 12 volt @ 210 AH batteries in parallel, so you have a 12 volt @ 420 AH battery bank

Nop its 2x 6v @210ah. Is it a 210ah bank or 420 ?

I put my system as a signature but its not showing for some reasons

KhellSk

@Photowhit @mcgivor

I am looking for mppt CC and for the rating, i dunno if i should divid my 240w by 12v(battery bank) or the Vmp of the panels in series 5x 15.9  ( max current of one lanel)

Also would you give me an exemple of the specs i should be looking for in diodes that i could use as a reference while browsing

mcgivor

The cheaper true MPPT controllers fall into this category https://www.amazon.com/EPEVER-Charge-Controller-Tracer-Display/dp/B01G413122 be prepared to pay about double or more for a name brand with a solid reputation, personally I've no direct  experience with this controller but do know others who report it works well.

mike95490

[2x Flooded  6v 210ah]
  in series, that gives you 12V  210 ah    Your batteries max charge rate would be about 25A.   So a controller would have to handle 350W.   So the panels you list, will not over power the controller you have.

KhellSk

mcgivor said:

The cheaper true MPPT controllers fall into this category https://www.amazon.com/EPEVER-Charge-Controller-Tracer-Display/dp/B01G413122 be prepared to pay about double or more for a name brand with a solid reputation, personally I've no direct  experience with this controller but do know others who report it works well.

When choosing the rating. How do i figure the amps

mcgivor

To be honest choose the highest amperage your wallet allows, the price difference is marginal, one thing to consider is future expansion,  a larger capacity allows for this and it will happen, trust me on that.

KhellSk

mcgivor said:

I agree but.I ld like to be able to know how to calculated it next so I dont have to ask again. Do i have to divide by the battery voltage or Vmp of the panels when it comes to MPPT ?

KhellSk

@BB.


this is the 5th, JB is slightly different and it doesnt have specs behind it but the front look exactly the same and when I tested it with a volt meter and amp meter It had the same results as the 4 others

Photowhit

KhellSk said:

I agree but.I ld like to be able to know how to calculated it next so I dont have to ask again. Do i have to divide by the battery voltage or Vmp of the panels when it comes to MPPT ?

Basically MPPT charge controller are rated on their output amperage. I like to push the max on these others like to be well within the output amperage max.

I would calculate the output of a 240 watt array in 2 ways, first figure out if the charge controller can handle 5 in series, that is still gong to be around 150 volts VOC (Voltage open circuit) which is a lot for them to handle, I would suggest most of the inexpensive wouldn't handle this!

Then I would use the total Standard Test Condition (STC) rating for the entire array 242 watts. From that I infer the Normal Operating Cell Temperature (NOCT) value which is about 75% of that or 242x.75=182watts. I would divid the 182 watts by max output voltage when charging the batteries, for 12 volt flooded batteries that will be around 14.5 volts. 182watts/14.5volts= 12.5 amps (using the formula amps x volts = watts)

So you need a Charge controller that will handle a VOC of around 150 volts ( if you panels specifies a VOC multiple by 5, you should also check to see what the coldest temperature in your area is! VOC at STC is around 75 degrees. below that the VOC will increase, if it's close you might plug it into Midnight solar string sizing tool, I think you can get a good estimate of the max VOC)

So, that's how I would do it, it assumes the charge controller can handle over paneling and most can. Others might use the total wattage of the array 248 watts and divide by the minimal output voltage around 12 volts, this would get you just over 20 amps, not likely to ever happen unless you really abuse your batteries and have very cold bright mornings.


Not a lot of good choices out there, the Midnite KID would handle 150 volts and 30 amps at around $320, The Renogy 30 amp only handle 100 volts (from my feeble mind)

You could roll the dice and go with an off brand like this; for $90, at least Amazon will stand behind it for a month or so;
https://www.amazon.com/Controller-12V24V48V-Battery-Regulator-Batteries/dp/B07G36DQ75

KhellSk

@BB.  I dont think my m75 are self regulating like you said

http://iodlabs.ucsd.edu/dja/codered/engineering/procedures/solarPower/Siemens M75 Spec Sheet.pdf
https://www.manualslib.com/manual/999851/Siemens-M55.html#product-M75
https://www.aepsurplus.com/upload/attachments/siemens solar panels.pdf

KhellSk

Photowhit said:

I would calculate the output of a 240 watt array in 2 ways, first figure out if the charge controller can handle 5 in series, that is still gong to be around 150 volts VOC (Voltage open circuit) which is a lot for them to handle, I would suggest most of the inexpensive wouldn't handle this!

Using only 4x 48watts 15.9v 19.8Voc 3.02a Isc3.35

PV Array
Rated PV Array Power:	192	Watts
Anticipated Array Power @ 40C:	179	Watts
Rated PV Array Current:	3.02	Amps
Battery Charging Current @ 14.4 V:	13.3	Amps
VMP (Maximum Power Point Voltage) :	63.6	Volts
VOC (Open Circuit Voltage):	79.2	Volts
VMP @ -30 C°:	79.2	Volts
VOC @ -30 C°:	93.6	Volts

Tristars are too expensive and I dont know any other brand other than ur suggested EPever

Heres a EPever I could get for a decent price;  would it work ?

Tracer3210AN  

It doesnt say the # max of Panels and 2 stars confuses me

Max. PV open circuit voltage
vs
MPP voltage range

littleharbor2

This should give you some idea of how much over paneling your controller can take.

KhellSk

Holy moly. Thats a lot of tolerance. But my problem is with Voc and that "mpp voltage range" (dunno what this means)

I cannot use 5 in series or I ll bust it. Thank you tho its good to know

KhellSk

@BB.  Are these going to work for blocking like you said ?
diode-15sq045
https://www.amazon.ca/gp/aw/d/B07CHFJ5WC

Also couls I you them to replace the bypass diodes already in the panels ?

MR750 W9something (i ld gave to look again whats the other number , see picture above)

jonr

Don't add a blocking diode if you are going to use matched panels with a MPPT controller.

mcgivor

KhellSk said:

Photowhit said:

I would calculate the output of a 240 watt array in 2 ways, first figure out if the charge controller can handle 5 in series, that is still gong to be around 150 volts VOC (Voltage open circuit) which is a lot for them to handle, I would suggest most of the inexpensive wouldn't handle this!

Using only 4x 48watts 15.9v 19.8Voc 3.02a Isc3.35

PV Array
Rated PV Array Power:	192	Watts
Anticipated Array Power @ 40C:	179	Watts
Rated PV Array Current:	3.02	Amps
Battery Charging Current @ 14.4 V:	13.3	Amps
VMP (Maximum Power Point Voltage) :	63.6	Volts
VOC (Open Circuit Voltage):	79.2	Volts
VMP @ -30 C°:	79.2	Volts
VOC @ -30 C°:	93.6	Volts

Tristars are too expensive and I dont know any other brand other than ur suggested EPever

Heres a EPever I could get for a decent price;  would it work ?

Tracer3210AN  

It doesnt say the # max of Panels and 2 stars confuses me

Max. PV open circuit voltage
vs
MPP voltage range

The Epever controller will work, however  if the panels are all in series the VOC  is a little too close to its rated maximum. The better arrangement would be two strings  ( two panels in series ) combined in parallel, the output dose not change just the VOC and VMP will be reduced. This will not be a problem with a 12V nominal system.

VOC is the array, or module, voltage without load, this voltage will increase at lower temperatures. At -30°C 93.6V is close  the maximum  rated input of 100V, in the series / parrallel arrangement the VOC would be 46.8V so well within limits.

VMP is the voltage when module is at maximum power. With series modules the VMP voltage is additive 

The MPPT controller will automatically find its maximum power point by tracking the constantly changing voltage, hense Maximum Power Point Tracking, MPPT.
 

Practically all the information needed is in the learning center, take the time to read especially what's relevant to your application if there are questions by all means ask, as a beginner this resource is invaluable https://www.solar-electric.com/learning-center
This link contains a glossary of terms used in solar discussion https://www.energy.gov/eere/solar/solar-energy-glossary