need help on wiring kc 120 panels wrongs amps

Re: need help on wiring kc 120 panels wrongs amps

Still a little confusing to read... But, basically, a solar PV panel is the same as a battery... Hook several cells + to -, that is a series connection and the output voltage will be, roughly, just n x Vpanel (4 panels * 19 volts = 76 VDC). The maximum current will be just the current of one panel.

If you connect + to + and - to -, then that is parallel... The voltage will be that of one panel, but the current will be "N" panels * rated current (6 amps * 4 panels = 24 amps).

Depending on the charge controller you are using, a simple charge controller should simple take the panel current and pass it, unchanged in value, to the batteries (assuming that the batteries are in need of charging and can take full current).

If you have a more expensive MPPT type charge controller (like an Outback MX 60), it can behave like a transformer and convert, say 24 vdc at 5 amps to 12 vdc at 10 amps--so you have to know the voltage and current at both the input and output side of a MPPT type controller.

So, if you take two 19 volt 6 amp panels and connect them in series, the voltage will be 38 VDC and the current will be 6 amps.

If you take the two 19 volt 6 amp panels and connect them in parallel, the voltage will be 19 VDC and the current will be 12 amps.

The above reading assume the panels are in full sun and you have a load that you can adjust for the maximum power point of 19 VDC and 12 amps. This is something a MPPT type controller does automatically--it adjusts the input current and voltage to find the maximum power point of the panels and, using an internal switch mode DC to DC power supply, to put out the 12 VDC and maximum available current to the battery (approximately 12 vdc and 19 amps in this example).

The simple way to test the panels is to check the open circuit voltage (see panel ratings) with a volt meter, then short the panel(s) with the voltmeter set to the appropreate amp scale (one panel, set meter to 10 amp scale), then short the panel with the meter... You should read, approximately 6-7 amps (depending on temperature, sun light, etc.). Putting several panels in parallel will probably exceed the maximum rating of your meter--so be careful.

Lastly, it is possible that you have every connected correctly and your RV's charge controller is simply limiting the current to 4 amps at that time--I don't know and can't tell from here though...

You talked about 14 awg wire getting pretty hot... The probably indicates that your are passing well in excess of 20 amps of current. That is not safe (can catch fire), and is also not very efficient--you are losing a lot of energy as waste heat... And if this is the wire going to the battery bank, you are probably not charging the batteries as well as you could be as there is significant voltage drop in the wire (so the charge controller thinks that the battery is more fully charged than it really is--and it will take longer to fully charge the battery bank).

-Bill

Re: need help on wiring kc 120 panels wrongs amps

i will try shorting the meter as part of the curcuit to the battery.

Please stop one second!

I am not sure how to read your statement here... But, the only safe method is to short the, otherwise disconnected, solar PV panel (one only) with your current meter... If you short any more than one panel (or a panel rated more than, typically 10 amps), you will damage/destroy your meter.

If you short a storage battery with your DC meter--you will cause massive sparks, current flows, melted wires, and possibly fire and/or explosions...

You may know exactly what you are doing with your meter--but I don't--so I want you to either be sure what you are doing, or get some help from someone who may have more experience.

-Bill

Re: need help on wiring kc 120 panels wrongs amps

Now that I got that warning out of the way...

If you have a simple charge controller (which for smaller systems is probably better than the expensive MPPT type controllers), you have to understand a bit how they work... In simple terms, there is an internal switch that simply connects the solar panel directly to the battery(ies) when charging. So, during absorb/bulk charging (batteries need all current possible from solar panels), if you connect the panels incorrectly (say in series rather than parallel)--you will see unexplained results.

What you will see is with two 19 VDC / 6 amp panels in series connected to a 12 VDC bank is (current can be 10-20% less and still be OK in full sun):

While the batteries are charging (full current from panels), you will see ~12-13 VDC at the batteries and 6 amps (if the panels are in series. As the batteries begin to fill, you will start to see the batteries approaching 14 vdc and the current start to ramp down (it may be a smooth reading of, say 3 amps, or it may read 6 amps / 0 amps / 6 amps / 0 amps as the controller switches on and off (depends on controller brand and, sometimes, settings). On the solar panel side, you will see approximately battery voltage as the batteries charge (12-16 vdc), and as the controller starts to limit current, you will see the input voltage to the controller start to rise quickly to 19 or even 38 VDC... You do run the risk of damaging the controller if the input voltage from the series solar cells is too high (above controller maximum input voltage).

If you have two 19 VDC / 6 amp panels in parallel connected to a 12 VDC bank:

Basically, it will be similar to above, but instead of 6 amps, you should see around 12 amps ramping down as the batteries fill. And the maximum input controller voltage will only be 19 VDC max (in full sun, batteries charged, controller taking very little current).

The solar PV panels behave pretty much like batteries--the only major difference is that they are current limited and shorting them does not draw that much more current than the maximum rated power current... And, because of this, they can be connected to storage batteries and operate at less the solar PV panel's rated voltage just fine (you cannot do that with most chemical batteries--they will try to output more current until they overheat or damage themselves). Solar PV panels put out more slightly more voltage when cold... And Current/Voltage (I/V) curve is pretty flat... Constant current until rated voltage is met, then as the current is reduced, the voltage rises a bit more to V open-circuit.

Hope the above helps you diagnose the problem a bit better.

-Bill

PS: Chad, you would be connecting the current meter correctly... Of course, you will want to stay under 10 amps and with multiple parallel panels in full sun, you probably will exceed it.