camper van .

[Gandhi]

Hi every one, I am a new member and no very little about solar power . This is probably the cause of my problem. I have fitted a 36 cell mono crystaline panel to the roof of my van. I have connected this panel to a 20 amp. DC to DC charger with a built in MPPT regulator. and the charger/ Reg . is connected to an AGM 140A/H 12v battery and also via a 16mm square cable to my Crank battery. The open cct. Voltage of my panel on a good sunny day is 22+ volts. The problem seems to be that when I connect the house battery to the system the panel voltage drops from 22V to about 12.3V. and produces a current of only 3.5 amps even when the house battery is 50% discharged. When driving the vans Alternator (2005 VW Transporter) will only send about 6 amps max back to the house battery. The end result of all this is that I have never seen the house battery show " Fully Charged". Any help would be appreciated. Thanks
Gandhi

[SunEagle]

That 22V is the open voltage from your single panel. When you connect a load, like the battery, it will drop down as low as the battery voltage.

As for only getting 3.5 amps of charging. That may be due to a single panel not seeing the correct amount of sunlight therefore it is only producing a lower output then stated.

What is the Imp rating of your panel?

With a 140Ah battery you really need about 14 amps of charging. You may get that amount with 3 x 100 watt panels.

[chrisski]

Do you know how many watts this panel is? My guess is its a 100 watt panel and is in indirect sunlight. Also, did you hook the Charge Controller to the battery prior to attaching the panels? It'll be in the instructions, but usually the charge controllers need to sense the the battery voltage, 12 VDC, 24 VDC, etx., before hooking the panels up. This means it can decide what to convert the incoming voltage to for charging.

[Gandhi]

Thanks chrisski. The panel was sold to me as a 200watt. ( i new no better) yes i hooked up the chargeer inthe following order:- 1 . Black wire to earth (ground), 2. Blue wire to battery positive, 3 . Red wire to crank battery , and 4 . Brown wire to panel.

[Gandhi]

Thanks suneagle. 1. he panel voltage drops below the battery volts. 2 what does lmp mean and 3 . Would 3 100w panels work better than 1 300 w panel

[sdold]

If the panel voltage is the same as the battery voltage, it may not be a true MPPT charge controller. MPPT would let the panel operate at its max power voltage (probably around 18V) and you'd see more current to the battery than you see from the panel. If the charge controller cost less than $100 or so it's probably not MPPT, Some of the cheap ones from China are known to be fakes.

[chrisski]

I'm a beginner also. My brand new 100 watt panel 12 Volt panel read 20 volts short circuit with 15 amps short circuit in Arizona Sunshine pointed at the sun. I consider the amperage unreliable because the meter was rated for only 10 amps. That is 15 amps is much higher than the rated 6 amp short circuit voltage. That is for an "Emergency generator" that is powered by a PWM charger. This Emergency generator is probably not much more capable than charging our USB devices including laptops and cell phones. I don't have a true deep cycle battery for it.

The MPPT system I'm building for my RV will have 440 amp hour batteries with 600 watts of panels. I also have a 2200 watt generator to run any larger items in my RV. The generator could be used to charge those batteries for things like extended cloudy days. Once I get this built in October, I've got a Battery monitor to watch energy consumption and make sure I don't drain my batteries too low.

[SunEagle]

Thanks suneagle. 1. he panel voltage drops below the battery volts. 2 what does lmp mean and 3 . Would 3 100w panels work better than 1 300 w panel

Imp is the number of amps when the panel is operating at 100%.

If you have an MPPT CC the 300watt panel is better. If you have a PWM then the 3 100w panels wired in parallel is acceptable.

[Bala]

What brand is the DCDC charger?

When I was looking at them even the MPPT controller built in to them the highest solar input was 29V in the redarc brand which is what I have.

Also how are you determining your battery State of Charge SOC.

[Gandhi]

Hi Sun Eagle. Thanks, I have a built in MPPT

[Gandhi]

Hi Bala , Brand of chatger / controller unknown. . SOC measured with a Voltmeter reading was 12.06 Volts ie. 50%

[Gandhi]

Hi sdold, The charger/ controller cost me about 220$, but I hear you about the cheap and nasty chinese junk.

[Bala]

Hi Bala , Brand of chatger / controller unknown. . SOC measured with a Voltmeter reading was 12.06 Volts ie. 50%

Should be a brand name on the controller.

How old is the battery?

How long since it was at full charge?

What is the battery running?

The Solar aside If the DCDC charger is only supplying only supplying 6amps from the Alternator to a flat battery you have either a defective charger, incorrect/faulty wiring or a failed battery.