Does size Matter?

packdaddy · February 2010

I have 6 X 15 watt solar panels hooked to this 30 amp charge controller. (23.5v open / advertised 12v)

Only the top light comes on orange/yellow, and never goes into charge mode. Is my array just too small?

Manual
http://www.sunforceproducts.com/prodinfo/manuals/60022_30ACC.pdf

BB. · February 2010

Re: Does size Matter?

I am not sure--the "yellow" led is battery ~1/2 charged? None of the other LED's come on at any time (I guess all LED's are off, unless the sun is shining on the solar array).

6x15w=90 watts
90 watts / 17.5 volts = 5 amps maximum charge rate

5 Amps is not a lot of charge--but should be OK to run the controller. At most, this is good for a 100 AH 12 volt battery with cycling loads. Or larger--if just trickle charging.

What are the solar array voltage and battery voltages?

-Bill

niel · February 2010

Re: Does size Matter?

are the battery statis leds indicating the battery state of charge? recheck that you've wired it correctly. if you have a digital meter to measure voltage then confirm the battery and pv voltages.

packdaddy · February 2010

Re: Does size Matter?

BB. wrote: »

I am not sure--the "yellow" led is battery ~1/2 charged? None of the other LED's come on at any time (I guess all LED's are off, unless the sun is shining on the solar array).
6x15w=90 watts

90 watts / 17.5 volts = 5 amps maximum charge rate

5 Amps is not a lot of charge--but should be OK to run the controller. At most, this is good for a 100 AH 12 volt battery with cycling loads. Or larger--if just trickle charging.

What are the solar array voltage and battery voltages?

-Bill

I will check at lunch time. I should be getting full sun by then. When I check, should I disconnect the controller and test?

Weather here in S. Texas (Corpus Christi) is 55F and not a cloud in the sky.

packdaddy · February 2010

Re: Does size Matter?

niel wrote: »

are the battery statis leds indicating the battery state of charge? recheck that you've wired it correctly. if you have a digital meter to measure voltage then confirm the battery and pv voltages.

- What is "pv" voltage?
- as far as wiring... I have rechecked that pos & neg are in correctly connected.
- No. it is not indicating state of charge.

FYI... This is the second one I have used. I took the first one back hoping it was just defective. But this one is doing the same thing.

mike95490 · February 2010

Re: Does size Matter?

packdaddy wrote: »

I will check at lunch time. I should be getting full sun by then. When I check, should I disconnect the controller and test?

Measure both, first with charger on, then disconnect the PV side, wait 5-10 min (sort of let voltage stablise) and measure again. Hook PV back up, and let it continue charging.

I'm assuming no loads are on while you are trying to charge.

Have you ever seen the blue LED (Bulk mode) on?

niel · February 2010

Re: Does size Matter?

pv=photovoltaic
see glossary in upper section.

BB. · February 2010

Re: Does size Matter?

The PV voltage--Solar panel voltage. Both unconnected and connected to the charge controller.

Many/most charge controllers will not work if the battery is dead (below ~10 volts or so).

Measuring the voltage going into the charge controller and out of the controller would be helpful.

And can you give us the name of the LED (yellow is supposed to be battery charge level, no orange listed). The photos in the manual are difficult to read LED function/name.

-Bill

niel · February 2010

Re: Does size Matter?

it does sound like either the battery isn't connected/connected right, the battery is dead, or the controller is defective. odds are it sounds like one of the first 2.

russ · February 2010

Re: Does size Matter?

İ get spam on google everyday telling me that it does!

packdaddy · February 2010

Re: Does size Matter?

I think some of my confusion is partly due to a poorly written manual. When I got home the bulk charge indicator was on, but it was green instead of blue like manual said. and the yellow light was no longer lit.

I hit the reset button and noticed that this also activated the battery test lights. After that the yellow light came back on and stayed. Evidently the battery indicator does not stay on.

I disconnected the controller and:
-the battery tested 13.3 v
-Panel is putting out 22.2 v

There is not a name directly beside the yellow light. The top three LEDs are just in a section that says "charge status" I can only assume now that it being yellow means that it is in a trickle charge or float (not sure of the difference) state

The controller will not work if it all connections are not made. When I connect just the array and test the output is says 0v. But when I was able to test the amps by connecting all except the positive side of the battery. It read 4.25 amps and the yellow light was lit.

With everything connected and yellow light on the battery test 14.3 v

Is it safe to say it is working?

mike95490 · February 2010

Re: Does size Matter?

You have to make the battery connection to the controller FIRST, before you connect the PV. You can place a meter inline to measure the PV amps, but if you want to measure battery amps, you have to disconnect PV, attach amp meter to battery leads, connect to charger, and then connect PV to the controller, then you can measure amps going to the battery.

BEWARE - you NEVER EVER put your amp meter across the battery terminals. if you do, your neighbors are likely to call the bomb squad. Either the meter goes "BOOM" or the batteries do.

packdaddy · February 2010

Re: Does size Matter?

mike90045 wrote: »

BEWARE - you NEVER EVER put your amp meter across the battery terminals. if you do, your neighbors are likely to call the bomb squad. Either the meter goes "BOOM" or the batteries do.

Ya I figured that one out on my own. The meter wires almost melted in my hand.

niel · February 2010

Re: Does size Matter?

next time have fuses for your battery connections and get a meter with a builtin fuse as well.

BB. · February 2010

Re: Does size Matter?

Yes--it sounds like everything is working...

A battery that has been resting for ~3 hours (no charge/no loads)--will read around 12.7-12.8 volts when charged.

And 14.3 volts (to maybe 14.5 volts) maximum is fine for charging. If you get above 14.5 volts--you may overcharge the battery ("boil" the battery and have to add distilled water more often, or if this is a sealed battery cause it to vent electrolyte and give the battery an early death).

-Bill

packdaddy · February 2010

Re: Does size Matter?

Thanks for the confirmation! I just don't know enough to feel confident in my assumptions.

Is it safe to say that if my battery is testing at 13v - 14.5v when hooked to the controller then it is charging? This way I don't have to depend on those darn lights.

BB. · February 2010

Re: Does size Matter?

14.5 volts would be charging heavily/nearly fully charged
13.8 volts would be charging lightly (or charging a discharged battery)
13.3-13.6 would be light charging/floating for long term storage
Below 13 volts not much is happening

Without knowing how much current is being supplied--it is difficult to tell the exact state of charge just on voltage (little current going into a full battery, or a lot of current going into a 1/2 discharged battery).
-Bill

mlail · February 2010

Re: Does size Matter?

I have a couple of quick questions about this thread.

To help avoid melting the wires going to the Amp meter, can someone use a simple inline fuse with the amp meter? Like the ones found in car radios? Also, how is it possible to attach those small wires between the batteries and the charge controller or inverter. The typical leads are too small to handle that kind of load, aren't they? That would suggest that a better (more expensive) Amp meter is needed?

Sorry, I too am learning so I ask questions were I can. So I noticed that you might be running a 12vdc charge controller, isn't 22 vdc coming in too much or at least at the high end of its rating, (for the safty of the average charge contoller)? If you are using a 24 vdc charge controller, isn't 22 vdc on the low side?

Thanks for helping clear my confusion!

mike95490 · February 2010

Re: Does size Matter?

to avoid melting your ampmeter wires, you need to measure currents within the ampmeter specs. If your PV is rated for 7 amps, that's within the 10a range of most handheld meters. 2 in parallel are 14a which is beyond the range. Would you plug a 12v light into a 120V outlet? Would you do it anyway if you had a fuse?

The 22V you see from the PV, is open circuit, and when you load the panel with the charge controller, you get about 17V. After losses in the charge controller, you have just enough voltage to equalize the battery at 16V.

Yes, 22v is too low to charge a 24v battery bank

BB. · February 2010

Re: Does size Matter?

mlail wrote: »

To help avoid melting the wires going to the Amp meter, can someone use a simple inline fuse with the amp meter? Like the ones found in car radios?

It is certainly possible--Many meters have internal fuses--but many of those, when set to 10 amp full scale bypass the fuse... The added resistance of the fuse adds enough resistance that it can make for inaccurate current readings (adds too much voltage drop to the circuit under test).

It really ends up being the operator's responsibility to ensure meters are connected correctly. Direct Connect Amp Meters are by definition, very close to a dead short.

Also, how is it possible to attach those small wires between the batteries and the charge controller or inverter. The typical leads are too small to handle that kind of load, aren't they?

Most DVM's are not really large enough to measure those high values of current. You can purchase some nice cumulative DC Amp*Hour / Watt*Hour meters that will address some of the issues with the smaller DVM's.

If you need to measure high currents, purchase a shunt and use an accurate milli-volt meter to read the voltage drop across the shunt. $25-$30 for a 100 or 500 amp shunt.

That would suggest that a better (more expensive) Amp meter is needed?

There are other solutions... For AC curcuits, a clamp on amp meter is a very nice and accurate solution. Separate the wire you want to measure current on and clip the clamp on the wire... Transformer coupled so no exposed voltages or high current connections to made. Very safe. Try to get a True RMS reading meter if you will be measuring non-sine wave current/voltage profiles (non-RMS reading meters assume that all AC voltage/current are sinewaves. Measuring MSW inverters and such will not give accurate readings).

You can also get for ~$100-$200+ clamp on DC Amp Meters too. The use a Hall Effect Transistor to measure the DC magnetic fields. The problem I have seen with them is that the Zero setting drifts quite a bit (by 1 amp or more) over a short period of time. The average DC clamp meters are not very accurate for lower value currents--But they are "safe" and very quick and easy to measure currents through your DC side of your Solar RE system.

Here is a low cost mfg. and their line of clamp on Digital Multi-Meters.

Sorry, I too am learning so I ask questions were I can. So I noticed that you might be running a 12vdc charge controller, isn't 22 vdc coming in too much or at least at the high end of its rating, (for the safty of the average charge contoller)? If you are using a 24 vdc charge controller, isn't 22 vdc on the low side?

It is confusing... But the voltage of your system is set by the battery bank itself. You could connect a 120 volt solar array to the battery bank, and as long as the bank was large enough (AH rating)--the bank would hold the voltage between 10.5 and 15.5 volts, depending on state of charge, amount of current, and temperature.

Where Batteries are "Voltage Sources/Sinks" with regards to current -- Solar panels are almost the exact opposite. Solar panels are constant current sources regardless of the output voltage (between zero and the rated voltage of the panel).

When you connect a current source to a voltage sink, the voltage sink is what sets the system voltage. So, you have a 22 volt Voc solar panel rated at 5 amps, the solar panel will simply output 12 volts at 5 amps into the battery bank.

The solar charge controllers must be designed to handle the higher voltage of the solar panels because when unloaded... A Vmp=17 volts will have a Voc (open circuit) voltage that is 22 volts or higher (Voc/Vmp rises as temperature falls).

Math wise... Look the equation for Power:

for PWM controller: Power = Voltage * Current

So--if you put a high voltage solar panel (say Vmp=24 volts) on a 12 volt battery bank--because you cut the power by 1/2, the power going into the battery bank is 1/2 too...

That is why MPPT charge controllers are nice (Maximum Power Point Tracking). They "down converter" high voltage / low current into low voltage high / current at the battery bank (excluding losses):

for MPPT controller: Power = Vmp*Imp (of panel) = Vbatt*Ibatt (of battery)

Thanks for helping clear my confusion!

You are very welcome. I hope that this make sense.

-Bill

BB. · February 2010

Re: Does size Matter?

Sorry, forgot to answer the 22/24 volt charging question.. Mike did...

The details are a bit more confusing... Regarding Vmp (voltage maximum power)--Ideally the Vmp rating should be:

Vmp~>Vbatt charging + 2 volts for controller/wiring drops

But Vmp changes quite a bit with temperature... A very hot panel has significantly lower Vmp. On a 100F day, your:

Vmp hot ~ Vmp * 0.78

So--you have to allow for Vmp depression in hot weather. And, you have to allow for Voc increases in sub-zero weather... You have to configure your strings for your local weather conditions, controller type, and battery bus voltage...

-Bill

mlail · February 2010

Re: Does size Matter?

Bill,

You answered things extremely well. Now all I need to do is retain all of this. I guess that is the case when we start anything new!

Also, What becomes very clear is that people tend to think about electronics as a static think. Instead the electronics is very varible. Maybe it is the sun aspect to the equazion.

Doesn't the voltage drop, "Vmp~>Vbatt charging + 2 volts for controller/wiring drops" also depend on the size and distance of the cabling? Is this + 2 Volts an average or mainly the controller?

Thanks!

mike95490 · February 2010

Re: Does size Matter?

mlail wrote: »

Doesn't the voltage drop, "Vmp~>Vbatt charging + 2 volts for controller/wiring drops" also depend on the size and distance of the cabling? Is this + 2 Volts an average or mainly the controller?

Thanks!

No, you are supposed to use cables large enough to not have to tolerate wire heating losses. Over the course of several years, it can amount to days of generator runtime to make up the loss. Or buy large enough wire, run higher voltage PV and use MPPT controllers.

BB. · February 2010

Re: Does size Matter?

The Vmp>Vbatt+2volts is just another rule of thumb that estimates the costs of many variables...

Vbatt may be 13.8 or 14.5 or 15.5 volts or higher or lower--Floating, Bulk Charging, Equalization, temperature (cold is higher, hot is colder for battery charging, AGM's are not usually charged above 14.4 volts or so.

2 volt drop--you need 1-2 volts across controller to move current. Does not account expressly for voltage drop--but you should take that into account. Also, Vmp is temperature dependent.

Also Vmp for solar panels is a pretty flat curve--you can move 5% up or down in voltage and not loose much current/;power.

So--the formula is just a short hand to do a "sanity" check when somebody talks about Vmp 15 volt panels charging batteries in the desert (hot solar panels)...

If you are sending power from the array to the battery/controller shack--then you really need to look at MPPT charge controllers which allow you to run Vmp~100 VDC nominal to reduce current which reduces voltage drop, and keeps the minimum voltage at the controller way higher than the Vbatt+2v rule of thumb.

Even I recognize that the details are much more boring. :roll:

-Bill

Does size Matter?

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