RV system help please

Dlindsey · May 2011

Hi:

I have a solar system on my 40 ft motorhome that is not working well.

I'm going to make some changes and would appreciate advice.

Originally it was an AM Solar system, with two AM100 solar panels and a Heliotrope HPV-22B MPPT controller.

The two panels are wired in parallel.

AM Solar discontinued the AM100 panels, so when I when I added two panels recently I was unable to match the output specs exactly.

I added two UL Solar STP100P-TS panels, which are wired in parallel with the original two AM100 panels.

My battery bank is 4 Interstate U2200 6v batteries wired in series/parallel for 12 volts.

I have a Magnum 2000 watt MSW inverter/charger and an 8KW Onan QD generator.

The specs for the AM100 panels are:
Voc = 27.0 volts
Vpm = 21.5 volts
Isc = 4.88 amps
Ipm = 4.54 aps

The specs for the UL-Solar panels are:
Voc = 22.8 volts
Vpm = 18.6 volts
Isc = 5.76 amps
Ipm = 5.38 amps

There may be some slight shading of panels at various times of the day, from a satellite dish and air conditioner shrounds. I guess that because of that, wiring in parallel is a good thing, yes? I will be looking at moving the panels to minimize or eliminate the shading issues.

I'm using an AM Solar combiner box with #10 wire from the panels to the combiner box and #8 wire to the controller and from there to the batteries. It's likely about 15 ft from the combiner box to the controller and another 15 ft to the batteries.

With the original two panels, I would often see 8 amps to the batteries on the controller. At noon, 10 amps was often seen. I once saw 12 amps.

Since I added the two new panels a month ago, I've seen no big improvement in current input to the batteries. Maybe I've added two or three amps, but it's clearly not working well.

Admittedly it was early spring here in Southern California, and the panels are flat on the roof, but I expected to do better than I did, regarding improved current input to the batteries.

I'm going to buy a meter, probably a Trimetric or a Parametric.

I could use some help understanding what to do to improve the system.

I'm already planning on using heavier wire and putting the new controller(s) in the inverter bay, which is just behind the battery bay. The wire length to the battery bank

Would I be will served to use one Morningstar Tristar MPPT 45, with the 4 panels in parallel? The 4 panels don't match, so that concerns me, but I don't know if I'm worrying for nothing about that.

Or, with the MPPT controller, would I be better off with two parallel strings, each string consisting of one AM100 and one UL-Solar panel in series? My idea here is to match the output voltages of those two strings.

Or do the potential shading issues mean more and parallel is a better idea?

Therefore, would I be better served to have two smaller controllers, maybe two Sunsavers or even two Tristar TS-45-PWM controllers and have each one handle two identical panels in parallel?

Thanks,
Dwight

niel · May 2011

Re: RV system help please

it could be the shading issue among other losses like wire resistance, but it's hard to say what and to what degree. have you tried just connecting the new pvs only and see what the output is from them just to be sure there's no problem there?

as to the cc you would be borderline on the current rating for your present cc, but it may be livable. i am not familiar with the cc you have now and if you plan any more upgrades than you propose then another cc would be mandatory.

soleil · May 2011

Re: RV system help please

With regards to the amps you are reporting (8-12 amps previously, now plus a couple more), is that what's coming into the controller from the panels (~24V), or what the batteries are receiving (~12V)? That maximum is when the batteries are low on charge, right? (When I first hooked up my system I wondered for a second why I was getting so little out of my system, but quickly realized the batteries were charged!

) Is that controller a "smart" charger?

With the 400W of PV panels you have, I would expect that you would get more out of the controller than that. I have 360W of flat mounted panels on my 5th wheel, and I have seen up to 25A to the batteries.

I don't know anything about your panels or charge controller. With regards to your wire runs, I don't believe the 15 feet run of #10 wire from 24V nominal panels to controller would be a problem (I have 25-30 feet of #10 wire from my panels to charge controller, and about 4 feet of #6 wire from the controller to the batteries).

Hope you get it figured out soon.

Dlindsey · May 2011

Re: RV system help please

Hi:

Thanks for the comments. Every bit helps.

What I really want and need is advice on the mis-matched panel issue, the parallel or series/parallel configuration and my question about one or two controllers.

I'm going to play with the solar tomorrow for the first time since the two new UL Solar panels were added. I'll be trying to sort out what each panel is or is not contributing.

Dwight

Dlindsey · May 2011

Re: RV system help please

Soleil:

The 8-12 amps plus a couple is on the 12 volt to the battery side.

I'm not sure of the battery state, although I have not done very much dry camping since the last two panels were installed.

When I'm plugged in, the magnum inverter is charging the house batteries. When I'm driving down the road, the alternator is charging both house and chassis batteries. And when the generator is running, the house batteries are being charged.

So . . . it could be that the batteries have been full when I've been looking at the solar controller.

I need a Trimetric or a Link. That may be my next purchase.

Dwight

Cariboocoot · May 2011

Re: RV system help please

My two cents worth:

You had 200 Watts of panel, from which you'd see 8 Amps charging current. That's not too far off what would be expected: 200W @ 77% efficiency = 154W / 14.2 Volts charging = 10.8 Amps

You added 200 Watts of dissimilar panel (more than 10% different on both Vmp and Imp) and expect to see close to double the original charge current. Instead it has only gone up 50%.

The wire size is adequate for both Voltage and current potential.

You do not know if the batteries actually need any more charge than 12 Amps. If they don't, you won't see it from the controller. (BTW, even 400 Watts of panel is low for that much battery - but you do not rely on panels alone to charge, so it should be okay).

Niel's suggestion is excellent: disconnect the old panels and run only the new and see how much charge current there is. It should be 8-10 Amps (discharge the batteries first so that they need some charging). If you can get 8-10 Amps out of either set of panels but only 12 Amps out of both then the charge controller is not able to pick an optimum power point due to the panel mismatch.

Instead of buying a more expensive MPPT controller like the MS 45, buy an inexpensive PWM controller to use on the new panel set.

Dlindsey · May 2011

Re: RV system help please

Thanks! I appreciate the suggestions.

I'll be playing with it in the morning.

Dwight

Dlindsey · May 2011

Re: RV system help please

OK . . . it was cloudy today, with occasional sun. Not the right day to unhook panels and compare output, because the output of the controller was changing quite rapidly.

I did notice that with the battery at approximately 12.8 volts, the Heliotrope was showing 11.6 amps going into the battery, but was flashing "charged". I take that to mean that the controller was seeing the batteries as charged and had reduced the voltage it was pushing to the batteries. I guess the charger was in float mode. The "mppt active when lit" diode was not lit.

So . . . I turned on the microwave. The Magnum inverter reported 108 amps coming out of the battery.

The "mppt active when lit" light immediately lit and the controller showed16.8 amps going into the controller, on a mostly cloudy day. There were shadows on the ground at that time, so there was some sun.

After myt 30 seconds of microwave experiment, I plugged into shore power and for the last hour the Magnum inverter has been bulk charging the batteries, initially at about 100 amps.

So, in addition to the mis-matched panels, I believe I have a stupid controller, that is going to float mode too early.

I believe I'm going to get another controller or two. Maybe as suggested the best thing will be to have two small controllers, on for each of the two matching panel sets.

I'm also going to get a Trimetric, or a LinkPro. I've never used either, so I'd be interested in any experiences with these meters. The Xantrex Link Pro looks a bit more intuitive and appears as if it might be a bit easier for my wife to understand and use.

Dwight

BB. · May 2011

Re: RV system help please

What are the cables between the existing charge controller and the battery bank (gauge and length)?

Have you taken a DMM and measure the battery voltage at the controller and at the battery bank--Look for voltage drop and such.

And what was the voltage at the battery (and/or inverter) when it was surging 100 amps?

464 AH @ 12 volt battery bank? --That is quite a kick at 100 Amps (sound like a great charger and/or your batteries are discharged a bit).

I think they are flooded cell--have you measured the specific gravity and/or resting voltage to estimate their state of charge?

-Bill

PS: Add BMV-600S and BMV-602S - Victron Energy Battery Monitors as another company that has a couple users here that like their product very much.

dwh · May 2011

Re: RV system help please

Dlindsey wrote: »

I did notice that with the battery at approximately 12.8 volts, the Heliotrope was showing 11.6 amps going into the battery, but was flashing "charged".

Okay, so the battery was charged and was floating at 12.8v. I would bet that the 11.6a of current flowing into the 12v bus wasn't going into the battery bank, but rather was powering some loads connected to the 12v bus.

I take that to mean that the controller was seeing the batteries as charged and had reduced the voltage it was pushing to the batteries. I guess the charger was in float mode. The "mppt active when lit" diode was not lit.

Right.

So . . . I turned on the microwave. The Magnum inverter reported 108 amps coming out of the battery.

The "mppt active when lit" light immediately lit and the controller showed16.8 amps going into the controller, on a mostly cloudy day. There were shadows on the ground at that time, so there was some sun.

Well then, there you have it. 16.8a from that array of PV modules on a day of less-than-perfect-sun is in the ballpark. I wouldn't change it until after checking the output under full direct sun.

So, in addition to the mis-matched panels, I believe I have a stupid controller, that is going to float mode too early.

Not too early - at too low of a voltage. Check with AM/Heliotrope. I seem to recall reading that there is a screw adjustment on the circuit board to adjust the voltage set points. You might only need to configure it correctly for your battery's recommended voltage.

I believe I'm going to get another controller or two. Maybe as suggested the best thing will be to have two small controllers, on for each of the two matching panel sets.

Nah, if you were seeing 16.8a out of that array in partly cloudy conditions, then I think that you are probably fine running the 4 PV modules together. Do the microwave test in full sun first.

I'm also going to get a Trimetric, or a LinkPro.

Good idea.

Dlindsey · May 2011

Re: RV system help please

Hi:

Thanks for all the suggestions. They helped. I've nt done everything yet, but I got started and made some progress.

We had a mostly cloudy day today, so I was only able to get occasional sunshine to test with.

I located the manual for the Heliotrope HPV-22B controller and found two pots to adjust. On the rear of the device was a voltage pot, adjustable as I recall from 13.4v to 14.8v. It was set in the middle somewhere. I turned it up to 14.8v.

On the front of the device is a "MPPT adjust" pot. Playing with that gave me a bit more current.

My batteries were full, after 12 hours of shore power. I unplugged from shore power and ran the microwave for intervals.

I saw 18.7 volts for a short while, while running the microwave and with a short burst of sunshine.

I'd still like to have a Morninstar Tristar controller much closer to the batteries and I'll likely something like that eventually. But for now, it's working better.

Thanks so much for the help.
Dwight

Cariboocoot · May 2011

Re: RV system help please

You might want to turn that Voltage pot back down a tad to get the charge V near the battery specs. Probably 14.4 at most (Interstate has some very high Voltage specs on their batteries). Not really a good idea to have the system creep up to 18 Volts.

dwh · May 2011

Re: RV system help please

Dlindsey wrote: »

I located the manual for the Heliotrope HPV-22B controller and found two pots to adjust. On the rear of the device was a voltage pot, adjustable as I recall from 13.4v to 14.8v. It was set in the middle somewhere. I turned it up to 14.8v.

On the front of the device is a "MPPT adjust" pot. Playing with that gave me a bit more current.

On a "3-stage" charger, the stages are Bulk, Absorb and Float. The way it generally works is that in bulk stage, the charger works in "constant current" mode - i.e., it tries to feed the max current available to the battery. To accomplish that, it raises the voltage however high it needs to be to get the max current flow until the battery reaches a certain voltage set point.

In Absorb stage, it operates in "constant voltage" mode, whereby it holds the voltage at a certain point for a certain length of time to allow the battery chemistry to absorb all the electrical excitement it can. An Iota charger (with IQ/4 module) will stay in absorb until the current flow to the battery drops below 1a, or 8 hours, whichever comes first.

In Float stage, the charger operates in "constant voltage" mode at a lower voltage to hold the battery up to full, but not to overcharge and bubble it.

The voltage set points for the 3 stages often look like:

Bulk - constant current until battery reaches certain voltage
usually 14.4v or 14.8v (14.2v for Gel type)

Absorb - constant voltage until current drops below 1a
usually holds at around 14.2v

Float - constant voltage
usually somewhere between 13.2v and 13.8v

So the question is: When you cranked up the pot on the back to 14.8v - which stage's set point got changed?

dwh · May 2011

Re: RV system help please

Cariboocoot wrote: »

(Interstate has some very high Voltage specs on their batteries).

He's got Interstate.

Dlindsey · June 2011

Re: RV system help please

Hello all:

I thought I'd update you on my system and the story so far.

As you'll see if you review the thread, I have 4 100 watt panels of two types (the original AM 100 panels were discontinued).

I added two more panels with a different voltage and was/am unhappy with the results. Once, when running the microwave with the panels in full sun I saw 18 amps. Usually I was getting 10 - 12 amps into the batteries. I believe that the inadequate programming, especally voltage, and the relatively small wires with long runs, were the issues.

After receiving good counsel here and elsewhere, I decided to use larger wire and to get rid of the flush mounted AM Solar controller, which was 15 ft or so away from the batteries as the wire ran.

I bought a Morningstar TriStar MPPT-60 controller. I bought the MPPT-60 because I wanted the Ethernet port. It also gives me room to grow. I could conceivably get 800 watts on the roof of the motorhome and might do that someday.

I also bought a Trimetric meter and the remote meter for the TriStar.

I got it installed and working yesterday, with 30 ft of #4 welding cable from the roof to the controller and 4 ft of #2 welding cable from the controller to the batteries.

At 2pm in Southern California, with some high clouds and haze, I saw 22 amps into the batteries. At 5pm I had 8 amps into the batteries.

Now we're cooking! It's working MUCH better than with the AM Solar controller. And things are wired, fused and switched (cutoff switches) better than before.

So I'm a happy camper.

Now to get 200 watts more up there as a next step.

Dwight

BB. · June 2011

Re: RV system help please

Cool!

Hopefully, you will have much more power available... And get your batteries charged quicker and more fully.

Did you run the remote battery temperature or voltage sense leads to the new charge controller?

-Bill

Dlindsey · June 2011

Re: RV system help please

Bill:

The battery temperature lead is already there, bolted to a battery stud. The voltage sense is not hooked up yet, but I'll do that next weekend.

dwight

BB. wrote: »

Cool!

Hopefully, you will have much more power available... And get your batteries charged quicker and more fully.

Did you run the remote battery temperature or voltage sense leads to the new charge controller?

-Bill

Dlindsey · June 2011

Re: RV system help please

Hmm . . . Looking at the log in the Tristar controller, it seems that yesterday I had a vmax on the panels of 21.4v and a max power into the batteries of 535 watts.

I guess that would be 25 amps from the panels to the controller.

Not bad for 4 mis-matched 100 watt panels (two different types and voltages).

If I'm reading and understanding this correctly, my system is working very well indeed.

Dwight

Dlindsey wrote: »

Bill:

The battery temperature lead is already there, bolted to a battery stud. The voltage sense is not hooked up yet, but I'll do that next weekend.

dwight

RV system help please

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