Help!

canuck sailor · May 2011

Hello all - I'm at my wit's end. I have a small panel on my sailboat, 123 watt sharp. I've got a BZP 250 MPPT charge controller and four Trojan 105 batteries. The panel shows 19 or so volts at the panel and at the wires at the controller. It also shows 4 - 5 amps when in bright sun, again at the wires coming from the panel.
When hooked up, the controller's display shows amperage running up to .5 amps, then back to 0, then up again. Battery voltage is at 12v.
Any thoughts on this?

BB. · May 2011

Re: Help!

The BZ controller is known to have many problems and should probably be replaced (using Google Search--works better for short word searches here).

Any number of small controllers from MorningStar, Xantrex, and other should work fine as a replacement.

The smallest "working" MPPT controller I am aware of is the MorningStar 15 Amp MPPT solar charge controller... This controller is a very good one--but probably not worth the extra money for connecting to your single 123 watt solar panel, unless you are thinking of expanding. Assuming this is a Sharp ND-123UJF solar panel (Vmp~17.2).

-Bill

canuck sailor · May 2011

Re: Help!

Thanks. I'd read that here before, but BZP has been working with me. They've replaced what I thought was a bad 250, but this one shows no improvement.
I don't think that leaving a 123 w panel connected full time without a charge controller will do my battery bank any good - four Triton 105s, connected to output 12 volts.
Going to try altering the float voltage next, see if that improves things.
One last question: IF that doesn't work, and I don't think from what I see here that it will, will it cause me any problems to hook the panel directly to my batteries for a few hours daily, until I get a new controller in?

icarus · May 2011

Re: Help!

Your. Panels are likey only going to produce ~ 5 Amps into 12vdc. If you have4 t-105s, that is ~450 ah of battery. That 5 amps is never likely to over charge a battery bank that big. Buy a Morningstar pwm controller. You gain almost no advantage with a MPPT controller on s uch a small system.

You are on a boat, use the BZ as an anchor for a very small dingy! I have one that I have bench tested, and it actually performs worse than no controller at all.

Tony

canuck sailor · May 2011

Re: Help!

Ok, so one MORE question. Came across another American made product, Tektrum. They have a variety of control units, here - http://www.tektrumcorp.com/solar_panels.htm.
I'd be interested in your off the cuff opinion, recognizing that without having a unit in use, it's hard to evaluate.
Thanks,

canuck sailor · May 2011

Re: Help!

Now you have me wondering - everyone, and I do mean everyone, says MPPT is the way to go, at least in the boating world (be nice now!).
I've heard a couple of times now that with small pv panels, PWM makes as much sense. Two questions - why, and what is the threshold for a PMMT controller? I plan on getting another 123 w panel at some point, so this may have relevance to my future needs.

Wally
(lost and confused!)

icarus · May 2011

Re: Help!

Simply put, MPPT give you a better harvest relative to a PWM controller,as much as 30% under low battery/cold PV temps. Most likely, and advantge of ~10% over the course if the day.

So spending $200 plus for a good MPPT as opposed to $50 for a small PWM does not make financial sense for a 10% gain.

For example, your system o f 123 watts might deliver ~ 100 watts net/net, so to get 10 watts, at a cost of $200, you would be better off (financially) buying 100 watts more panel at $2/watt, and yielding a gain of about 80 watts net/net.

Remember, an MPPT controller will convert excess PV voltage to current. A panel producing 17 volts, and putting it into a 12 volt battery, can only put it into that battery at battery voltage, say 14vdc. 5 amp at 14 volts is 70 watts. That same 5 amps into 17 volts is 85 watts.

The reality is that unless the spread between PV voltage and battery voltage is very wide (low battery voltage and or cold PV) the gain is likely be quite small.

Tony

BB. · May 2011

Re: Help!

Here are a couple quick FAQ's about MPPT controllers:

All About Charge Controllers
Read this page about power tracking controllers

Basically, the big advantage to MPPT controllers is the internal power supply is basically a buck mode switching computer controlled power supply which can take high voltage/low current and efficiently down convert it to low voltage/high current... Basically, the DC equivalent of an AC transformer that takes 120 VAC input and outputs 12 VAC output.

What is the big advantage to MPPT is you can put a Vmp-array of ~100 VDC (maximum for many controllers) and down convert it efficiently to 14.5 VDC to charge your battery banks.

Remembering that Power = Voltage * Current:

P=I*V
I=P/V= 500 watts / 100 VDC = 5 Amps DC at 100 VDC
I=P/V= 500 watts / 14.5 VDC = 34.5 Amps DC at 14.5 VDC

So--You can use wire that is about 1/6th the diameter (~9 awg smaller), or send the power 6-12x farther with the same awg wiring.

For a 123 Volt panel with Vmp=17.2 volts on both a MPPT and PWM controller during a sunny but cool day:

0.95 efficiency * 123 watts / 14.5 volts = 8.5 amps using a MPPT controller
123 watts / 17.2 volts = 7.2 amps using a PWM cotnroller
8.5/7.2 = 118% increase in current...

But, that 118% increase will decrease as both the day and the solar panel get warmer...

If you had multiple solar panels, and installed them in series (to increase the Vmp-array operating voltage)--Yes--MPPT is the way to go.

Also, for solar panels >100 watts--typically the big guys that cost less $$$/Watt do not have a a standard "12 volt" rating (~17.5 volts Vmp)--Instead, they are optimized for large Grid Tied Solar arrays with MPPT type (maximum power point tracking) front ends (same as MPPT solar charge controllers) that are designed to run at 200-600 VDC or so...

So, these larger "GT" solar panels are designed with Vmp in the range of Vmp=35-70VDC or even more... Then--when used on a battery based system, you must use a MPPT solar charge controller to properly "match" the array Vmp/Imp to the Vbatt/Ibatt charging requirements.

A starting rule of them I use--Typically, 200 watts or less, look at PWM. 400 watts or more, look at MPPT type solar charge controllers.

At this point in time, MPPT charge controllers are usually not worth the money behind a sub 200 watt single "12 volt" (Vmp = 17.5 volts) solar panel.

-Bill

bmet · May 2011

Re: Help!

icarus wrote: »

So spending $200 plus for a good MPPT as opposed to $50 for a small PWM does not make financial sense for a 10% gain.

Tony

They are advertising an mppt controller for $65. Too good to be true?

BB. · May 2011

Re: Help!

bmet wrote: »

They are advertising an mppt controller for $65. Too good to be true?

Usually. Have not seen one that works yet at that price point.

-Bill

waynefromnscanada · May 2011

Re: Help!

bmet wrote: »

They are advertising an mppt controller for $65. Too good to be true?

Too good to be true? In all likelihood the answer to that is a definite yes. Probably not MPPT, although they say it is, and probably a POS you'll be sorry you touched.
Who is doing the advertising? What make and model?

bmet · May 2011

Re: Help!

Canuck Sailor posted a link in one of his previous post, tektrumcorp.

canuck sailor · May 2011

Re: Help!

Should have included the link....http://www.tektrumcorp.com/solar_panels.htm
Any and all comments welcome. love to hear your opinions on this.

Ok, on to my little challenge. As I noted, BZ has been trying to help. Initially, they sent me a PWM controller, model M20, to replace my original 250. I've hooked it up. When the PV is hooked into it, it shows 14.9v incoming. When I hook up the battery bank, it shows the battery voltage, which is at the moment 11.9. However, and this is where I get fretful, the amperage coming in shows to be .7 amps. That can't be right, can it? That doesn't take my batteries anywhere.
Can someone please tell me what's going on? The M250 isn't working. The M20 doesn't seem to work. Is it me screwing up here somehow?
Voltage from the panel is around 19v, and the ammeter shows 4 - 5 volts. I presume that by hooking my ammeter up to the panel leads, then selecting the appropriate item on my mulitmeter, I am doing it right?
Shoulda taken shop instead of latin I guess...

Wally

BB. · May 2011

Re: Help!

Here is one thread which shows what may be in the "typical" inexpensive WellSee controller and other re-badged controllers.

Compare the picture from the Above Thread, to the pictures at the vendor site listed in the first post of this thread:

mppt ? picture

You can see the difference (lots of copper and iron in the MPPT controller) vs the typical PWM controller.

Copper and coil winding--adds lots of weight and costs to any piece of electronics.

-Bill

Cariboocoot · May 2011

Re: Help!

Wally;

Step one: check the panel. Measuring the Voc (Voltage open circuit - no load attached) is meaningless. Set your multimeter on 10 Amp DC scale (if it has it) and put one lead on each wire from the panel - nothing else on the wires - in bright sunlight. You should get a reading close to Isc (Amps short circuit - the 'I' is for "Intensity"; an old term). It ought to be near 8 Amps. If you can't get this reading the panel is likely damaged and no charge controller can make up for that.

Step two: disregard the charge controller. Hook the negative lead of the panel directly to the battery. Hook the positive lead to the multimeter - again set on Amps - and the other lead of the meter to battery (+). In bright sun you should get around 7 Amps going to a discharged battery.

Step three: check the Specific Gravity of each battery cell. Make sure they are even, and that the electrolyte level is up to the bottom of the fill tube. Charge the batteries somehow right away before they become so much scrap metal (if they haven't already).

Step four: figure out where you can put some sizable solar panel because 123 Watts isn't going to do much for 450 Amp hours of battery. Barely keep ahead of self discharge.

Step five: order up new panel(s) and appropriate sized charge controller from NAWS. You're wasting your time messing about with the BZ people. We've yet to see any signs of improvement in their product.

As for Tektrum corp ... looks like an importer of dubious-quality Chinese goods like the Wellsee controller. Notice how the description says MPPT and then says microprocessor controlled PWM charging. The most polite way of putting it would be "some sort of pseudo-MPPT system". A decent PWM controller would probably outperform and outlast this no-name unit.

BB. · May 2011

Re: Help!

canuck sailor wrote: »

Should have included the link....http://www.tektrumcorp.com/solar_panels.htm
Any and all comments welcome. love to hear your opinions on this.

See my post just below--I believe that Tektrumpcorp units are not MPPT--but without popping the case--it is difficult to tell.

Ok, on to my little challenge. As I noted, BZ has been trying to help. Initially, they sent me a PWM controller, model M20, to replace my original 250. I've hooked it up. When the PV is hooked into it, it shows 14.9v incoming. When I hook up the battery bank, it shows the battery voltage, which is at the moment 11.9. However, and this is where I get fretful, the amperage coming in shows to be .7 amps. That can't be right, can it? That doesn't take my batteries anywhere.
Can someone please tell me what's going on? The M250 isn't working. The M20 doesn't seem to work. Is it me screwing up here somehow?
Voltage from the panel is around 19v, and the ammeter shows 4 - 5 volts [probably you mean AMPs]. I presume that by hooking my ammeter up to the panel leads, then selecting the appropriate item on my mulitmeter, I am doing it right?
Shoulda taken shop instead of latin I guess...

More than likely, there is some current flowing if you are measuring 4-5 amps.

19 volts * 5 amps = 95 watts

Which, is not bad from a 123 watt solar panel in "typical" conditions. Not great, but not bad.

The other issue--You need to know the battery bank voltage and state of charge... If the controller thinks the battery bank is full--it will cut back on the charging current.

But, in your case 11.9 volts charging--if that is the correct battery voltage--Your bank is well below 50% state of charge and you need to get it recharged back to >90% state of charge quickly.... The longer it sits below ~75% state of charge, the quicker your battery is "sulfating" and the shorter the life it will have.

Measuring current with a DMM and solar charge controllers is a bit difficult. DMM's can change the operating point and "move the readings around".

In the Vpanel input is more accurate (voltage drop of meter is less critical) and, assuming you have it setup correctly, then you have sort of OK current flow.

The Vmp=19 volts is high (should be closer to 17.2 volts or less) if MPPT was operating correctly--But difficult to tell from behind my keyboard.

Measuring the output current from the charge controller with a DMM will be a bit more difficult as DMM voltage drop can confuse even a working controller.

At this point--Assuming you have good sized / short copper cable from the battery bank to the Charge Controller--And the charge controller is displaying non-nonsensical readings (voltage/current--especially voltage readings that are not close to your DMM voltage readings))--Then it is not working correctly and you are just chasing your tail trying to prove something that has design issues is not working correctly.

If you are going to get into more debugging of your 12 volt DC power system (including your boat and automobile electrical systems)--I would recommend spending around (at least) $60 USD for a DC Current Clamp Meter (meter also does AC current, and has the usual volt/ohm meter functions too).

Very handy to have in general--But not a "great" investment to prove that you have a boat anchor for a MPPT charge controller.

-Bill

Vic · May 2011

Re: Help!

Notice that the Tektrum 15 Amp "MPPT" CC has the elusive "Thunder Protection"
Very useful ! Vic

canuck sailor · May 2011

Re: Help!

Hello Cariboocoot - ok, as suggested. Put the unit's dial on 10a, probe in the 10 amp plug. The reading was .7 in fairly bright sun - it's about 5:30 when I took that reading. With the ammeter set at 20m and the probe, the reading is 7.0. I'm not sure of the scale, so not sure of the situation here. It's either bad, or ok.

I'd go to step two, but it will take some time to get a decent wire to the batteries and, I think, your response to the above might tell me what I need to know.
In the meantime, I'm going to fire up the engine and charge - was going to do that regardless, not wanting the batteries to be sitting at this level.
Is it the panel, based on the above? Can you tell?

Wally

Cariboocoot · May 2011

Re: Help!

Good sun should be around noon with the panel pointed right at it.

5:30 PM ... Canada ... probably not a dependable test.

And we don't know how good your meter is.
I will politely skip the possibility of operator error.:roll:

canuck sailor · May 2011

Re: Help!

I'm in Florida, not Canada. Operator error is a strong possibility, but just in case I managed to get this right, what do my readings say?
I'm not entirely sure how to read the scale is my problem. It looks like it's either 7 amps, or .7 amps, it's certainly not 70!
With the sun going further down, the readings have declined to about 5.7 or .57....

Wally

Cariboocoot · May 2011

Re: Help!

Florida? Traitor!

On the 10 Amp scale the reading should be straightforward Amps. Bright sun directly on the panel should produce a reading of 7.0, not 0.7 (which is seven tenths of one Amp). You sure you've got both meter leads in the right places? I have seen some DVM's that require a shift in the negative lead as well as the positive in order to read Amps. Only your instruction manual knows for sure.

canuck sailor · May 2011

Re: Help!

After correcting for an error in the operator input mechanism:D, and tilting the panel:grr:-) to face the blazing Florida 8)sun at 6:15 local time, the DMM now shows 3.5 amps, not .7, when set up as earlier noted.
Comment? Is the panel toast, or what?

canuck sailor · May 2011

Re: Help!

btw, thank you for suggesting the issue of operator error. Being a conservative and former journalist, the concept of being wrong is quite unfamiliar to me...:roll:

Cariboocoot · May 2011

Re: Help!

canuck sailor wrote: »

After correcting for an error in the operator input mechanism:D, and tilting the panel:grr:-) to face the blazing Florida 8)sun at 6:15 local time, the DMM now shows 3.5 amps, not .7, when set up as earlier noted.
Comment? Is the panel toast, or what?

Probably not. Solar intensity is at its peak midday; less atmosphere to filter through. See what a difference the angle makes? Getting Voltage from a panel is easy, but it's the current that counts.

Note too that this is one of the reasons why getting solar to work on a boat isn't easy; the panels are almost never at an ideal angle to the sun. It's better the closer to the Equator, of course. But I sure wouldn't want to sail through the Northwest Passage relying on solar.

canuck sailor · May 2011

Re: Help!

I suspect my next step is to check the panel tomorrow at noon, plus hook up the battery as you suggested and do your second test.
I was wondering: if the second test, to the battery, shows any substantial difference in amps, what's that indicative of? For example, let's say I show 6 amps at noon - I believe I've seen at least that in the recent past - and the amperage through the battery shows 4 or 3....what's the significance of that, since, as you've said, your second test should show about the same results as the first.
Thank heavens for my wind generator. Now if only the wind would blow.

Cariboocoot · May 2011

Re: Help!

The thing about the second test is that it adds an additional variable: State Of Charge of the battery. A battery that's charged will have high internal resistance and so the current flow from the panel will be low. A discharged battery has lower internal resistance = higher current potential. When testing just the panel the resistance is fixed: dead short across the leads (or as close to as is practical). This leaves only the variable of he amount of sun hitting the panel. You've seen the difference that can make.

What we're looking for here is how much current the panel can put in to the panel with the third variable - the charge controller - removed.

Your battery Voltage reading of 11.9 indicates a fairly well discharged battery (although Voltage is not an ideal SOV indicator) - about 40% charged. BTW, that's below the max you'd want to see. If these batteries have been chronically undercharged or habitually over-discharged there may be no hope for them. You're running with very little panel, so I hope that engine has been fired regularly to boost the batteries up. Even then, alternators don't have the proper charge profile for deep cycle batteries.

Being a conservative and former journalist, the concept of being wrong is quite unfamiliar to me...

Not married, then?

canuck sailor · May 2011

Re: Help!

btw, thanks to everyone for the many replies to my questions and patience with my lack of knowledge. Not all technical forums are this friendly or accommodating, and I appreciate it greatly. I hope I've contributed something here, besides creating hysterical laughter, from my faux pas.

Wally
s/v Gypsy Wind
lying Melbourne FL
heading north to the Great Lakes

canuck sailor · May 2011

Re: Help!

so, if I understand you Cariboocoot (and no, I'm not married and I'm NOT going to ask you you knew, lol!), the second test should show a low amperage with the battery low, right? i.e. if the panel is showing 6 - 7 amps, it would be expected to see a significantly lower reading with a low battery?
I had thought that the current to the battery was greater, the lower the voltage, with the amperage tapering down as voltage approached 100%, i.e. 14.1.
Or am I misunderstanding something here? I'm misunderstanding something, aren't I?

I think I'll go feed the puppy, and ponder this.

Wally

canuck sailor · May 2011

Re: Help!

fyi, for all - here, I can contribute something. Cruising boats often significantly undercharge their batteries, as a result of the way we use them. If we're at anchor for a period of time when it's cloudy and windless (assuming wind and solar, fairly typical), then the batteries get significantly drawn down.
Many cruisers use a generator rather than run the diesel. Others run the diesel for an hour or so, bring the voltage up to 13.1 or so, then let it run down again. That gets expensive and diesels are noisy and pricey to repair if it becomes necessary.
As a result, and we mostly know this, we are killing our batteries more rapidly than necessary, but the various tradeoffs - run the engine with an expensive regulator and expensive diesel fuel, install more and varied expensive electronics that can go sour in remote places where repair/replacement isn't possible, expensive aux generator - aren't always attractive. A lot of boats don't have room for a large enough pv array - I will likely to to another 130 w panel, for a total of about 250 and that's all the room I have to charge up 400 plus ah of battery. And I'm thinking of getting another 225 ah worth. Plus perhaps install a second Airex wind generator.
We reduce usage with LEDs, etc., make sure our battery banks are fairly large, try to keep the drawdown to less than 50% - but still, to a greater or lesser extent, batteries are an expendable item for those of us who cruise.

Cariboocoot · May 2011

Re: Help!

canuck sailor wrote: »

so, if I understand you Cariboocoot (and no, I'm not married and I'm NOT going to ask you you knew, lol!), the second test should show a low amperage with the battery low, right? i.e. if the panel is showing 6 - 7 amps, it would be expected to see a significantly lower reading with a low battery?
I had thought that the current to the battery was greater, the lower the voltage, with the amperage tapering down as voltage approached 100%, i.e. 14.1.
Or am I misunderstanding something here? I'm misunderstanding something, aren't I? I think I'll go feed the puppy, and ponder this.

Wally

It's t'other way 'round. The more discharged the battery, the greater the current from the panel (solar intensity being equal). It's the Voltage difference between the panel trying for 17.5 and the battery being at 11.9 - lots of electrons want to hurry over to the battery; high current. As the battery recharges and its Voltage comes nearer to the panel's the current flow will lessen (standard transfer of energy thing). But the current is likely to always be less than the Isc because the battery will always have greater resistance than a dead short.

BB. · May 2011

Re: Help!

Solar panels are, more or less, "constant current sources"--which, electrically, is the exact opposite of batteries--which are constant voltage sources...

What does that mean? Batteries, we are all familiar with... You take a 12 volt car battery and it starts around 12.7 volts fully charged. You put a bunch of current on it--and it stays still around 12.x volts.

Solar panels, on the other hand, Below, roughly Vmp (17.2 volts or so for your panel)--If you place a dead short on a panel, it will output no more than ~Imp to Isc (maximum power, or short circuit current)... Basically if you have full sun, the solar panel will output no more than Imp from zero volts to ~Vmp of 17.2 volts... (the panels are not perfect--so they will output a little more current a zero volts--but not much).

So--The operating voltage is reached around when weak sunlight hits the panel (Vmp to Voc--voltage open circuit). The current is then proportional to the amount of solar energy hitting the panel...

Full noon time sun on a clear day--Your panel will output near its Imp/Isc ratings.

If you connect your battery bank directly to your solar panel (+ to +, - to -; don't get it backwards or you will destroy your solar panel instantly)--The panel will output current proportionally to the strength of sunlight hitting the panel.

When connecting a 17.x solar panel to a 12 volt battery--you do not even need a charge controller to do this... Put a volt meter on your battery and watch the voltage rise (as the battery approaches full charge). And with a current meter, the amount of current will be the amount of sunlight at that moment. This is actually a good way to check your solar panel to make sure it is working correctly (again, watch polarity--can easily ruin your panel if connected backwards to battery).

To cut down on charging current, put an on/off switch in the lead to the battery and turn it on to charge, and off to stop charging... that is pretty much what a PWM charge controller is doing--just a bit faster On/Off switching.

When the battery voltage hits the Absorb voltage--the controller starts opening the switch more often to keep the battery at 14.x volts. The battery itself, will draw less and less current. At some point, the controller will decide the battery is full (current draw, timer, or combination) and drop the voltage back to 13.x volts for "Float" charging--Just enough current to keep the battery fully charged.

-Bill

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