Connection problem - newbie

System · April 2007

Hopefully someone can steer me in the right direction! (I'm not an electrician!!) I am hooking up a very simple system for short-period boondocking - we use very little power - a 40 watt PowerUp panel and a 4.5 amp Sunguard charge controller. Yesterday was a very sunny afternoon in Albuquerque & I set up the system, not connected to the single RV battery in order to check power output of panel & controller. After 30 minutes in bright sun - at about 50 degree panel angle - I checked voltage from charge controller at to-battery leads - no indication of any power at all - no movement of the needle on voltmeter. I checked voltage on the panel & my voltmeter pegged to below zero. The older voltmeter doesn't give number readings below zero (not digital), but it does work perfectly. I attached positive from controller to panel, put voltmeter lead on positive out to battery from controller & I have negative volt reading when I put negative voltmeter lead on negative out on panel. Changing only the negative test connection (using either negative on controller & connecting either negative on controller to negative from panel & testing at other negative from controller lead), I get no reading on voltmeter (no needle movement at all).

I would think that in the bright sun, angled pretty well, I should be getting something other than a negative reading from panel. (Am I on the right track?). Any ideas, suggestions? It is starting to look like panel is bad. Thanks for any help!!! - Charlie

Roderick · April 2007

Re: Connection problem - newbie

If you disconnected the panel from the charge controller, the panel should never put out negative voltage under any reasonable lighting conditions (that is, if you're able to read your analog voltmeter, there's enough ambient light).

Maybe the leads are reversed?

What you can try doing is set your multimeter (hopefully) on current, and see how much current is coming out of the panel. If it's a 40-watt panel, I would expect a few amps from it in bright sun, if it's (say) a 12-volt model.

If you look on the back of your panel, see if there's an open-circuit voltage (Voc) and short-circuit current (Isc) rating, and if so, please post here. Then people can help you more.

System2 · April 2007

Re: Connection problem - newbie

Roderick, thanks for the quick response. Yes, this is a 12-volt model. No, the leads weren’t reversed – that was my first thought & I unwrapped all connections to be certain. All of my (above posted) checks were made with the multimeter set on 12V DC. The manufacturer’s website lists the following as specs for the panel: Rated power: 40W; Peak power: 40W; Peak power voltage: 17.8V; Peak power current: 2.40A; Voc – 22.2V; Isc – 2.60A.

crewzer · April 2007

Re: Connection problem - newbie

I am hooking up a very simple system for short-period boondocking - we use very little power - a 40 watt PowerUp panel and a 4.5 amp Sunguard charge controller. Yesterday was a very sunny afternoon in Albuquerque & I set up the system, not connected to the single RV battery in order to check power output of panel & controller.

Charlie,

It's possible / likely that the SG won't operate without the battery connected first. See page 3 of the SG manual for the recommended connection sequence: http://www.morningstarcorp.com/products/SunGuard/info/SG_Manual.pdf

HTH,
Jim / crewzer

System2 · April 2007

Re: Connection problem - newbie

Jim, thanks for pointing that out! Yes, I'm now aware the controller has to be connected to the battery to work. What I'm trying to figure out, tho, is whether the panel is functioning or not. From what my multimeter is telling me, I'm just not sure. Maybe this is serious operator error(!), but I want to know that the panel is putting out juice before I rely on it to keep my battery charged up next week while I'm far from an electric source (other than my tow vehicle). Thanks again for your input. Charlie

mike95490 · April 2007

Re: Connection problem - newbie

40W panel is a pretty minimal panel, it will run a small light for a couple hours a night, More than that, and you will be running your battery down. example:
Day 1 100 %
day 2 90 %
day 3 80% .... if you burn more than you recharge. when you reach 50%, the controller will disconnect the load form the battery to prevent over discharge of the battery.

As to measuring voltage from the panel connections, with nothing but your Volt meter connected, you should see around 15V - maybe a bit more. otherwise you may have a sick panel, bad connection on the back of the panel, something wrong.

crewzer · April 2007

Re: Connection problem - newbie

Charlie,

There are a couple of way to check your PV module's operation. One is to measure its open-circuit voltage (Voc) when exposed to the Sun and not connected to anything but your volt-meter. You should see ~22.2 V when the module is cool, and that will drop as the module heats up when exposed to the Sun.

A way to check your system's operation is to measure and record the battery voltage. Let's say it's 12.6 V. Then, connect the SG to the battery and the PV module to the SG. Exposed to the Sun, and with no loads on the battery, the voltage at the battery terminals should rise fairly quickly to ~13 V or so, and then slowly rise to ~14.1 V, at which point the SG will convert from bulk mode to PWM (absorb mode). Because you're using a PWM controller, the voltage at the PV connection should be just a tad over the battery voltage when the PV module is exposed to the Sun.

Here's a link to all sorts of info about your AG controller: http://www.morningstarcorp.com/products/SunGuard/index.shtml

How big (in Ah) is your RV's 12 V battery?

HTH,
Jim / crewzer

System2 · April 2007

Re: Connection problem - newbie

Jim, thanks for the input. The battery is an Interstate SRM-24. Specs at Interstate's website show: Hours @ Ampere Load: 16.4@5; 4.6@15; 2.3@25. My load is very low - we run a couple of lights at night for a few hours, no 110V inverter, water pump when needed - that's about it. We plan to be away from electric for five days - first run with this solar setup.

I realize now that I shouldn’t have seen any output through the controller (operator error on that one!) without it being connected to the battery. The battery is in a full charge state (I use a Battery Tender). I’m concerned that with the panel only being connected to the multimeter (set in 12VDC mode) in full bright sun the meter pegged to below zero, with no indication of any voltage output at all from the panel. Today is a rainy day in ABQ, so can’t do any checking. I’ll follow your suggested check when I get some sunshine.

Thanks again, Charlie

crewzer · April 2007

Re: Connection problem - newbie

I’m concerned that with the panel only being connected to the multimeter (set in 12VDC mode) in full bright sun the meter pegged to below zero, with no indication of any voltage output at all from the panel.

Charlie,

OK. Make sure you set your meter for a scale high enough (at least 25 VDC) for the anticipated Voc... 12 V is way too low. You should be able to verify the meter's operational status by measuring the SRM-24's "resting" voltage (not connected to any chargers or loads for at least three hours.

Tomorrow's supposed to be sunny and windy in ALB! 8-)

HTH,
Jim / crewzer

Connection problem - newbie

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