New to Solar --- Charge Controller Test ?

System

I have just purchased and wired my first solar panel for use in battery charging for my popup camper. I don't know how to test for output of the charge controller.

I have a multimeter. I used the meter on the panel itself and got a reading of 20.8 volts, so I know that I'm good there.

How do I test that my charge controller output is actually working? I took readings on those, and did not get any voltage reading at all. Do I need to be
actually connected to the battery to get a reading? If so, what kind of range should I expect to get --- I would assume something over 13 volts.

Thanks a lot --- I know this is basic stuff to most of you.

Rance

BB.

Re: New to Solar --- Charge Controller Test ?

Yes, there is a very good chance that your solar charger will not function at all (i.e., show voltage on the output leads) without being connected to a battery...

Your controller's output voltage will depend on the state of charge of the battery, the amount of solar energy/panel size, and battery (and/or controller) temperature.

Check both manuals, the battery manual and the controller manual and make sure that the controller is set for the proper battery (AGM, wet cell, etc.) and temperature (lead acid batteries are very sensitive to change voltage and battery temperature).

Having an accurate (calibrated) voltmeter and knowing the battery temperature (and if wet cell, using a temperature compensated hydrometer), as well as proper use of equalization (and monitoring electrolite levels--again wet cell) are all going to be vitally important to ensure your batteries a long life. If the voltmeter is off by a couple 1/10's of a volt (or more), it is almost useless for accessing the proper charging of a battery (a hydrometer is probably more accurate).

Overcharging (boiling a battery dry) and undercharging (sulfation if the battery is stored discharged for more that a few days) will quickly kill the capacity of your battery bank.

If you want some exact recommendations on how to run your system, knowing the brand/model of the charge controller and batteries would be helpful.

-Bill

System2

Re: New to Solar --- Charge Controller Test ?

Thanks for quick reply. This should be an easy answer for you. Yes, I found someplace else on the net that I must be hooked up to the battery in order to get a reading.

I have a Marine (hybrid) deep-cycle battery on my popup camper. It's a group 27. It is not sealed. I have a new Kyocera, 54-watt panel. I have a new, inexpensive, SunGuard controller. It does not have an LED indicator on it.

I'm continuing to read explanations of multimeter use to test charging. I just went out and hooked everything up. If I have the panel hooked up, I get a reading on the battery of 12.5 volts. If I remove the leads from the panel, I get a reading of 12.1 volts (yes, my battery is somewhat discharged at this time).

I read on another website, if I am understanding this correctly, that I SHOULD have a difference of several 10ths of a volt difference. I'm not sure if I'm actually measuring at the proper place. The site stated that "...and the solar panel at the input terminals must be a few tenths higher than the battery voltage". I was reading this link:
http://www.21st-century-goods.com/page/21st/PROD/CHGCTL7

Does that mean I need to read the solar panel terminals, while hooked up, and measure against the battery? Unhooked up, my panel was outputing 20.8 volts, so the quoted statement doesn't make sense to me.

Again thanks. I know this is going to be simple. I'm just trying to charge a single deep cycle battery. I just don't know where I need to be putting the multimeter leads to get readings, and what those readings should be.

mike95490

Re: New to Solar --- Charge Controller Test ?

1st use a digital meter to measure your battery 12.267V maybe

2nd connect your PV panel to voltmeter -
measure voltage - should be higher 14V

3rd Hook it all up, you should see controller charging battery at higher voltage than step 1, check every hour, it should get larger each time. You don't have a large panel, so this could take 3 days to get the battery completely full.

BB.

Re: New to Solar --- Charge Controller Test ?

OK, there are others here that can provide better answers about controllers and battery systems--but here is my 2 cents worth...

Your SunGuard controller appears to be a simple one voltage setting (14.1 vdc) with temperature compensation ([FONT=Times New Roman, Times, serif]-28[/FONT][FONT=Times New Roman, Times, serif]mV/°C--should be 0 vdc offset around 20C or around 70-77[/FONT][FONT=Times New Roman, Times, serif]°[/FONT][FONT=Times New Roman, Times, serif]F).[/FONT]

So, you will want this controller, if possible mounted next to your battery (~same temperature as battery). And if the battery is around 70-77F, then when fully charged, it should read 14.10 volts.

Keeping the leads short, and low voltage drop (because of current) from the battery to the controller is important--as the controller needs to know the battery's true voltage to within 60 milli-Volts or so (controller accuracy).

The solar panel voltage (when connected to the controller/battery) will be a few mill-volts (or more) higher than the battery itself because of voltage drop through the controller/wiring. Yes, this is true when the battery is in the "absorb" phase of charging (battery voltage below 14.1 volts and accepting as much current as the panels/charger can supply).

However, once the battery voltage rises to 14.1 volts, the SunGuard controller will go into PWM mode (pulse width modulation). Basically, think of the controller opening and closing a simple switch--the switch is closed 100% of the time while in absorb mode (battery accepting all of of the solar panel's current), but once 14.1 volts is reached, the switch will be open for a time so the battery does not overcharge... Eventually, the switch will be open most of the time and the voltage you see on the solar panel terminals will rise close to the 20.8 volts (full sun, charge controller delivering little charge current to the full battery).

Of course, the 14.1 volts of the battery is dependent on the temperature... If the battery gets 10C warmer (18F), the charge controller will drop the voltage down by 0.280 volts (or 13.82 volts). A cold battery will, of course, get more charging voltage.

Since this is a simple charge controller, you will need to watch the battery "water" like a hawk--and you may wish to disconnect the charge controller for most of the month (maybe connect it a few days every month) when the trailer is in storage... This controller does not (appear) to support a float charging voltage (less voltage once the battery is fully charged) and will tend to electrolyze the water out of the battery during periods of non-use.

As you get used to how the charger works and the battery survives, you will probably look to more sophisticated solar controller/chargers and other battery options.

I am not the expert here--I still have a lot to learn too.

Does this help?

-Bill

nigtomdaw

Re: New to Solar --- Charge Controller Test ?

Bill I m impressed clear and consise I thought you nailed it !:-)

System2

Re: New to Solar --- Charge Controller Test ?

Thanks again for good explanations! Sorry, I'm still trying to work through my basic ignorance.

Yes, I have the 'basic' controller and a small 54 watt panel. I'm only doing this to 'dry camp' for relatively short periods of time. Just need enough juice for minimal camping needs. I do have an at-home charger --- panel will only be used while camping without electrical hookups so no worries on overcharging or other issues. I don't even need it to supply 100% -- just enough so I don't discharge my battery more than 50% while camping.

I HAVE wired with only 18 inches of 12 gauge wire from charge controller (it's portable). So, it will always be close.

What I'm still confused on is this 14.1 volts you mention. My fully charged battery should not be much more than 12.7 volts. Are you saying that when battery is fully charged, AND I am connected to panel, I will see a reading of 14.1 volts (give or take) by putting meter leads on the battery?

When I tested today, I only had panel out only 15 minutes. Panel itself had 20.8 volts. Battery itself had 12.2 volts. When I hooked panel/controller to battery I read 12.6 volts. It sound like that .4 volts difference is what I am looking for (proves that I am charging). Is that correct?

It sounds like I should test this for an entire day and watch the readings go up to hopefully, 14.1 or so. Is that correct?

If so, tomorrow is supposed to be sunny and I'll put this thing out in the yard in full sun and see what it does.....


Thanks again.

12vman

Re: New to Solar --- Charge Controller Test ?

Quote..
"I have a new, inexpensive, SunGuard controller."

Is this the one you are using..?



Quote..

"The SunGauard is the little brother of the SunSaver and it is only available in 12V version with a 4 amp capacity. It is also a PWM controller with temperature compensation and simple 4 wire hookup. The SunGuard has a slightly lower output voltage than the SunSaver and ProStar and may not be the best choice for flooded batteries that require a higher voltage."

BB.

Re: New to Solar --- Charge Controller Test ?

A large Lead Acid battery basically sets the voltage of anything connected to it... With your charger "charging" the battery has 12.6 VDC in that condition (at its current state of charge, temperature, and current flowing in). Your solar panel is a very "weak" battery--it will (with a PWM controller) will assume the voltage of the battery it is connected too (when the battery is below 14.1 volts--because of that PWM "switch" being closed 100% of the time).

Your charger is set to attempt to keep a maximum of 14.1 VDC on the battery--but that will only happen when the battery is more than 80-90% of capacity (and being charged)...

As the battery approaches full charge (100%), the controller will automatically taper down (via that little switch opening and closing) the average current to maintain 14.1 volts.

Once the battery has been at 14.1 volts for a period of time, and the current is very low--then, ideally a more sophisticated charge controller will drop back down to float voltage (13.8 vdc or so) and maintain that voltage indefinitely. At this state, the battery is neither losing charge or gaining charge (or electrolyzing/boiling away battery water).

You cannot really tell the state of charge of a battery with a charging current or load current connected... You have to turn off all loads (and sources) to the battery and let it "rest" for a 3 hours or longer and use an accurate volt meter (plus temperature compensation chart) to see the approximate state of charge.

The hydrometer--from what I have read here, is much more accurate for determining the true state of charge (and/or using a battery monitor like one of these).

Wind-Sun has lots of little FAQs around their site... Here is the one on Batteries. It does a much better job of explaining than I can ever hope too.

Stolen from this FAQ is the approximate battery voltage vs charge (at ~70F-77F... Remember, you really want to not go much below 50% on a standard flooded cell storage battery to have a good long life:

State of Charge--/--12 Volt battery--/--Volts per Cell
100%---12.7---2.12 (dc volts)
90%---12.5---2.08
80% ---12.42---2.07
70% ---12.32---2.05
60%---12.20---2.03
50%---12.06---2.01
40%---11.9---1.98
30%---11.75---1.96
20% ---11.58---1.93
10%---11.31---1.89
0%---10.5---1.75

Assuming your battery was 12.1 volts at around 70-77F, then it is about 50% charged... So, if this is a 100 Amp*Hour battery, it will take about 50 Amp*hours (actually about 55 amp*hours because of 10% loss due to battery charging losses) to get if fully charged.

I could not find a Kyocera 54 watt panel--but assuming it is about 16.9 vdc at Vmp (Maximum power), its current rating would be roughly:

54W/16.9A=3.2 amps.

Assuming it is summer where you are at and you have 5 hours of sun a day--then your panel, if pointing at the sun at high noon (basically, at the latitude for your location), then you would get:

3.2Amps * 5 hours/sun per day = 16 Amp*hours per day...

55 Amp*Hours (battery 50% + 10% loss) / 16 A*hours/Day = 3.4 days to charge

So, with your setup (assuming accurate meter, guess of sun, etc.), it would take about 3.5-6 days of full sun to fully charge your battery after you have used 50 amp-hours (or at its current state of charge)...

Make sense?

-Bill

crewzer

Re: New to Solar --- Charge Controller Test ?

What I'm still confused on is this 14.1 volts you mention. My fully charged battery should not be much more than 12.7 volts. Are you saying that when battery is fully charged, AND I am connected to panel, I will see a reading of 14.1 volts (give or take) by putting meter leads on the battery?

When I tested today, I only had panel out only 15 minutes. Panel itself had 20.8 volts. Battery itself had 12.2 volts. When I hooked panel/controller to battery I read 12.6 volts. It sound like that .4 volts difference is what I am looking for (proves that I am charging). Is that correct?

It sounds like I should test this for an entire day and watch the readings go up to hopefully, 14.1 or so. Is that correct?

Rancelumsden,

What you are seeing is normal performance in a system such as yours.

The 20.8 V you measured from the “panel itself” is called the “open circuit voltage”, or Voc. Under STC conditions, this is the highest voltage the panel can generate, but there’s no current flowing. Once the panel is connected to a load, current will flow and the voltage will drop due to a variety of reasons, including the module’s own internal resistance.

The battery’s 12.2 V reading (not connected to any loads or charging sources) represents something close to what’s called “resting voltage”. A voltage measurement taken under these conditions gives you a useful approximation of the battery’s state of charge (SOC). In your battery’s example, its SOC is ~50%, which, for a typical Group 27 size battery (12 V x 105 Ah), means that its ~52 Ah short of being “full”.

The 12.6 V reading you saw when you connected the PV module and the controller to the battery did indeed mean that the battery is being charged. It did not mean, however, that the battery’s resting voltage was 12.6 V.

What you saw is called a false high voltage called "surface charge. It’s caused by a thin layer of relatively high specific gravity electrolyte that’s in direct contact with the battery’s positive plates. Like teas steeping, this high SG electrolyte self-mixes throughout the rest of the electrolyte as the battery charges.

Similarly, a battery under load will indicate a "false low" voltage because the thin layer of electrolyte in contact with the plates will be lower than that of the rest of the fluid. However, once the load is removed and the battery has had a chance to "rest", the voltage will recover.

The 0.4 V difference between the resting voltage and the charging voltage is a good initial indicator that the battery is charging. However, this difference should increase to ~ 1.4 V for a flooded-cell lead-acid battery like yours. This is the difference between the 14.1 V regulation voltage and a fully charged battery’s resting voltage of ~12.7 V.

Once the battery voltage reaches 14.1 V, the controller will hold it there for as long as there’s sufficient charge current and little or no load on the battery, and the battery will slowly continue to recharge.

I suspect that Morningstar chose the 14.1 V absorption voltage to allow the controller to be used with both flooded-cell batteries, which typically require ~14.4 V, and sealed batteries (AGM or gel), which typical require 13.9 V to 14.3 V. Accordingly, you may see 14.1 V at the battery terminals for several hours, but the battery won’t be 100% full.

The controller contains a thermistor and it will adjust the PWM regulation voltage according to its temperature, which is assumed to be something close to that of the battery. The reference temperature is 25 C / 77 F. For every 10 C / 18 F decrease in ambient temperature, the regulation voltage will increase by 0.3 V, and visa-versa. So, depending on the temperature of the controller, you may see a PWM regulation voltage other then 14.1 V.

The output current from the PV module is probably ~3 A or so. If the battery really is at ~50% SOC, I’d expect it’ll take two or three days for the PV module to “fully” recharge the battery.

Finally, you may be able to hear the controller when it’s in PWM mode, as it will “hum” as the transitors are turned on and off as Bill described above.

HTH,
Jim / crewzer

System2

Thanks to all of you: New to Solar --- Charge Controller Test ?

Thanks to all of you guys!

12vman --- yes, the pic of the controller you posted is the basic one I have.

Yes, I'm finally getting it and appreciate the detailed answers!

Actually, I really find this exciting, even though it's a very minor use of solar. I've been 'environmentally active' for decades, and I know I can't cost-justify the panel, but wanted to support 'the cause' (and I really dislike the idea of camping and generators).

So, I really admire those of you using solar on a regular basis for larger-scale applications and appreciate bearing with me on this.

I'll get that panel outside this am (got full sun) and monitor it over the day.

12vman

Re: Thanks to all of you: New to Solar --- Charge Controller Test ?

I used one on a small yard lighting system and it never brought the battery to full charge. Just thought I'd make you aware of that..
~Don

To add..
Consider the C-12 controller. This give you a little elbow room for expansion. Also, You can operate from the "Load" side of it that has an adjustable shutdown voltage setting to avoid damage to your battery..

http://www.xantrex.com/web/id/71/p/1/pt/25/product.asp

rohanjcp

Following yor footsteps

Hello rancelumsden,

Thank you for sharing your experiences with us. I am a beginner and was interested in setting a similar system as yours. I was going to buy the Kyocera 65W solar panels and buy the rest of the parts.

Since you also ordered a Kyocera panel, I wanted to ask your experience with it. Specifically, I was wondering if you needed to buy anything else aside from the solar panel and charge controller- wires? fuses? adaptors? Are you happy with the volmeter or the multimeter you got? Does the manual explain how to implement the tests you did? And was it relatively easy to assemble? Any other suggestions for a newbie like me would be helpful.

Thank you so much for reading.
rohanjcp

raytech

Re: New to Solar --- Charge Controller Test ?

First off, Hi i am raytech. i have built my first panel from some robust (not powerful) cells. didn't want to jump into the pool if there wasn't any water, or i couldn't swim. I have since purchased enough (brittle) cells to make (3) 63 watt panels (if i don't break more than 2). My current panel is small. it registers just over 19 volts at full sun light exposure. it is only about 7 watts (based on stated amps - see below). I have a charge controller with diversion and Schottky diode installed (found out the diode the hard way). Now to the question portion.

I hate to bring up an old thread, but i have been searching for about an hour or so, here and elsewhere, and this one seemed most relavent to my topic. I have a battery that is shot. I am new to this, but was wondering about the voltage.

when i say the battery is shot, i mean about .8 volts open. with the solar panel attached through the charge controller it hits about 1.8-1.9 volts. open voltage of the charge controller is up to 19+ volts. is this normal? or have i done something incorrectly? also how do i check the amperage of the panel. i have seen many different ways, both with and without resistors. which way is correct?

my main question is:
should the voltage of the connected solar panel drop when trying to charge a battery of a lesser voltage?

second question is:
how do i accurately test the amperage to calculate wattage?

sorry for the winded version

BB.

Re: New to Solar --- Charge Controller Test ?

A lead acid battery (when properly charged and working) is (more or less) a constant voltage device (i.e., it tries to hold ~11-14.5 volts across its terminal).

A solar cell, once it has sufficient sunlight--is (more or less) a constant current device... The output current is proportional to the amount of sunlight.

So when you connect the two together--the battery will set the system voltage and the solar panel will set the charging current (up to ~Vmp or voltage maximum power--above this voltage, the current starts to drop off).

So--the battery you have is in one of several states.

1. Dead--not charged. So, adding current will bring its voltage up to a "charging state" (likelihood is that the battery will never recover enough charge capacity to be of any use).

2. Open Cell--inside there is a cell connection or cell to cell bus that is open/corroded through. In this case, you will never get much current through the battery and it will remain dead (voltage may rise quite a bit with charging current).

3. Shorted Cell--One (or more) cells has been shorted together by shedding lead debris at the bottom of the cells. Battery will probably never come up to full voltage (one cell shorted).

To measure the charging current just put an amp meter (10 amp full scale to start with) in series between on battery post and the charging wire (do not place a amp meter across a lead acid battery--fire and smoke will result--you can, however place an amp meter across the output of a solar panel to measure its short circuit current and see if the panel may be good or not).

In the end, if a lead acid battery has not been taken good care of (stored nearly fully charged for its entire life)--Then it is probably no good (lead sulfate hardens inside the discharged battery and never recovers--hardening starts in hours/day or so when below 75% state of charge).

Some people, with heavy duty fork life batteries, have reported being able to restore some useful capacity. Your mileage may vary.

-Bill

raytech

Re: New to Solar --- Charge Controller Test ?

I most appreciate the detailed response. It was actually the answer i was looking for, proving me right, and that i had not miswired my system. when i hook up my multimeter in the 10 amp max config, and put it in line with the charger i get absolutely nothing. i hook up the negative to the comm and still nothing. i have an electro-tek cat 2 btw. is this a mis config on my end? or am i maybe not interpreting correctly.

again thanks for the response. I am actually soldering my new panel together right now. already cracked a panel, but it still has a full .5 out. man they are paper thin.

BB.

Re: New to Solar --- Charge Controller Test ?

By the way, if you have a solar charge controller between the solar panel and the battery--the solar charge controller may need 6-10 VDC from the battery before it will begin charging (depends on the design of the charge controller).

-Bill

mike95490

Re: New to Solar --- Charge Controller Test ?

When a battery is low, a panel can be connected directly to it, to charge, you should see a battery voltage increase every 5 minutes or so, if it really is charging.
11.005V 11.008V 11.011V and so on...

raytech

Re: New to Solar --- Charge Controller Test ?

it never got above about 1.8 volts at full sunlight. i am guessing dead. on a happier note, i just got done tabbing 50 solar cells. only cracked 2 (still same voltage, unsure amperage) and actually broke a corner off of one. this is my first time working with cells, so i am pretty happy with those numbers. they are paper thin. you can feel them flex through the solder iron. so glad i bought one with heat adjustment

I thank everyone for advice, and gladly accept more (novice to expert)

and i have tried the direct connection. exact same numbers, plus the voltage drop of the schottky (bout .17) ran without it for a few days only to realize that was a bad idea. battery showed negative voltage. never saw that before. read "-.71"

System2

Re: New to Solar --- Charge Controller Test ?

I also have this controller. I hooked it up to a monitor.
Mine will charge the battery to 14.3 volts.......it will hover there for a short while, then drop to 14.1.
It will fluctuate going back and forth from 14.1 to 14.3 for a few minutes, maybe 10 or 15 minutes.
After about 30 minutes of hitting 14.3 initially it will settle in at 13.8 and seems to stay there till the voltage goes down.
I know that doesn't seem to jive with what Morningstar is stating, but that is how mine works.
Seem to be a nice little unit for small solar applications.
The SG4 is completely quiet.......and will stay running till the voltage drops below 6 volts.
They dont mention the SG4 going into a float mode, but mine eventually settles into a 13.8 volt charge.......that sounds like a float charge to me.

unberleavable

Hy Everyone, Greetings from Down Under.

What a fantastic post for people like me that I'd consider a newbie. So clear and concise...excellent!!!

I have a few questions that might sound simple.

I have a AGM Deep Cycle 135amp battery hooked up to a DC-DC Charger that charges the battery when I drive. No problems.

When I pull up or camp. I put a folding set of 200w Panels and hook it directly to the battery. There's a little volt meter that's always hooked to the battery with a toggle switch, so I can check the voltage of the battery or what's going in.

Last time I used the panels. The little volt meter was ranging between 17 to 18 volts with the panels connected, full sunlight and the fridge running 65 litre evakool fridge/freezer and this scared me a little.

Does this mean the MPPT Controller I have on the  solar panel has died and not controlling the voltage correctly? I certainly have not seen it go that high before.

Is there a test I can do to check the Controller?

When I hook the Multimeter direct to the terminals of the controller connected. I am getting 40+ volts

Can I hook the panels to the input of the dc dc charger and control voltage that way?

Thank you

BB.

Unber,

Welcome to the forum. I will suggest that you create a new "thread" with your questions. It will be easier for us to follow the Q&A for your system.

In general, AGM batteries should be between ~11.5 volts (~50% discharged, under load) to ~14.4 volts maximum for AGM at 75F/25C (fully charged). The battery is essentially discharging at ~12.8 volts or lower. And charging if 13.8 to 14.4 volts.

You are correct, if you are seeing >~14.4 volts, the battery is being over charged (AGM batteries particularly do not like being overcharged). And if you run >~15-16+ volts, your 12 VDC loads can be damaged.

Note, we are talking about the battery bus voltage... Solar panels can easily be ~20-22 VDC ("12 volt" panels) if unconnected.

If your MPPT controller is working correctly, you will see "operating voltage" on the battery bank and around Vmp=17.5 volts or so when charging (as battery gets fully charged, the array voltage will head up to Voc (voltage open circuit) of ~20-22 VDC (no load on panels).

I am a little confused... You talk about connecting your panels directly to the battery bank (200 Watts) in one place, and the other asking if your MPPT controller is working correctly. Yes, you can connect your panels directly to the battery bank (watch polarity, connecting panels backwards will ruin your panels--fuse or not).

If you are seeing >~16 volts on your battery bus with the panels>MPPT controller>battery --- Then the MPPT controller is probably having problems.

Note--You should always connect the solar charge controller to the battery bank first, then connect the solar panels (and disconnect solar panels first, then controller from battery bank). If you connect the battery bank second, the charge controllers can get "confused" (or even possibly damaged in a few cases). The solar charge controllers need good battery bank voltage first to boot/run their microprocessor (generally >9.5 volts of battery voltage to boot).

Longer term, getting a DC Current Clamp Voltmeter (AC/DC current clamp DMM--digital multimeter) is really handy. You just clip it over one wire, and you can measure the current flow (don't have to disconnect wires and put a DMM set to 10 amp scale in series to measure current). Here are a couple meters for you to see your options (lots of choices out there--Note, there are lots of AC/DC voltage DMM, and AC clamp DMMs that do AC+DC voltage measurements--but not DC current, you need to get an AC+DC current clamp capable DMM):

https://www.amazon.com/gp/product/B019CY4FB4 (mid-price meter) ~$105
https://www.amazon.com/gp/product/B00O1Q2HOQ (good enough for our needs) ~$52

Without a current meter--You can use a good quality (12.XX) meter to see what the battery bank is doing... Charging, you want 13.8 to 14.4 volts (with 14.4 volts held 2-6 hours per day, ~13.6 "float voltage"). And you really don't want to see the battery bank below ~12.10 volts (no loads/resting for 3+ hours) and avoid drawing much below 11.50 volts under load... Lead Acid batteries don't last as long taken below 50% state of charge, and if taken to dead/10.5 volts, they can easily be ruined.

-Bill

Porschephanatic

GREAT THREAD!      Watching with interest.