Solar and alternator charging on passage observations and questions

[socaldmax]

Originally Posted by millhouse_44

Hello all;

I've been following this post sequence trying to figure out my problems with my system. I have a Leopard 40 Cat with 600 Ah battery bank of sealed AGM batteries. Standard alternator fit-out not three stage external which I will get sorted based on these posts thank you!

I recently fitted 540 Watts of Solar panels (3x180W panels) with an MPPT charge controller (3-stage). I have been cruising in Thailand since install, about a month and I've been monitoring the performance of the solar. I have not been impressed so far with what I'm getting and I have some theories on why it is not working as advertised. I was expecting to get about 150 Ah of power from the panels and we are consuming about 240 Ah per day, so I knew there would still be a deficiency but since we are on the move regularly and have an onboard Genset I was not worried about having to top up once in awhile (OK, about every 2-3 days).

My problem is that my panels are not pushing out enough voltage. Actually, the MPPT controller is not 'letting' them - the voltage into the controller is coming in at 19 V but the 'out' voltage is only about 12.8. This is in 'bulk' and 'boost' mode. I've seen as high as 13.2 to boost mode and in float it is about 13.2 as well. The controller is set for closed-cell batteries (which I have) but this reduces the voltage for charging down about 0.7 V from what it would be with regular flooded lead-acid (according to the MPPT specifications see attached).

My theory is that the problem is with temperature. It is very hot here and sunny every day. The temperature rises rapidly in the morning and during the heat of the day is 36-40 degrees C. The solar system is tested at 25 degrees C and from what I'm reading online there is a loss of 10-25% in power output from the panels as temperatures rise. The issue though is that I'm still seeing 19V coming into the charge controller and only 12.85 out (on average). I'm wondering if the charge controller is overheating and therefore reducing the efficiency? The controller does not feel warm to the touch and I don't even hear the internal fan running most of the time on it.

The other thing is, I am wondering about changing the MPPT controller setting back to the 'standard' (non-closed cell) setting to up the voltage output. I read that using this setting can damage closed-cell batteries but I presume that is only if the voltage is too high. Does anyone know whether this 'trick' to up the voltage would work or have any negative consequences for the batteries over the long term? (the output should be 14.8 for non-closed cell and 14.2 for closed cell during bulk charging and 13.8V and 13.2 during boost according to the specifications of the charge controller).

Lastly, the MPPT charge controller has a temperature compensator input on it that is not currently connected. Obviously some form of thermostat can be installed on this that will help the unit compensate for the higher temperatures. I have asked the installers about the fitting needed and ordering one. Does anyone have any experience with this? Will this help solve the 'voltage out deficiency' problem I'm experiencing?

Thank you for the assistance!!

Derek Miller
S/V Small Cat Fun
Phuket, Thailand

First off, that solar controller looks like one of the low end controllers that I'd stay away from. Assuming that it really is a 30 amp MPPT controller, the output voltages that you are seeing are based on battery SOC, rather than potential charger voltage. This means that although the charger says it can put out 14.3v into your batteries, the actual voltage will be determined by how much current you're using at the time and what the battery voltage is. If you anchored for a day and shut everything off, you might see higher voltages as the battery charged, but voltage really isn't a good measure of solar performance.

Better controllers would display input V, input watts and output V and A. This would give you a much better idea of solar system performance. There's a good chance that your controller is defaulting to a lower voltage without the battery temp. probe. You might also be getting shading or the sun is low in the sky, which will drastically cut down on output.

In terms of your solar array vs solar controller, the array is rated at 540w and your controller is rated at 400w, so theoretically you might be losing some power due to self-regulation in the summer. Instead of getting 36-37A at midday in the summer, the controller will be maxed out at probably 32 amps. This isn't a problem in the winter, but either way, you're not getting all 540w of output.

You may also have some other losses related to cable size and length, but since you didn't specify, I don't know.

I'd recommend dumping that off brand controller and getting a well known brand- Midnite Solar, Outback, Morningstar, etc. Not only are these proven MPPT controllers (get a 45 amp model) they can also handle 150v input, so you could wire the panels in series and reduce your voltage losses without changing any cable sizes.

Hope this helps!

[millhouse_44]

Thanks for all the assistance! Sorry to 'hijack' the thread but I thought this was an appropriate thread to discuss 'power' output given the theme. Next time I will start my own but what I typically get when I do that it a lot of 'you should search this forum for other posts on the subject before posting a new thread' so it seems you can't win sometimes on here.

It seems logical to me that the controller is not sufficient for the amperage/watts/volts being produced given it has a 10 Amp max rating and 400 watt maximum input. I queried this when I got the controller from the vendor but they indicated that since the panels won't be 100% efficient all the time because of the fixed mount, I'll only probably see 350-400 Watts power maximum at any given time in any event. They assured me that the controller would be sufficient for the panel array but I'm sure it is not now. The array is pushing out lots of amps - about 20 amps at peak afternoon power with a good sun angle, but again only at 12.8 Volts. It seems logical what you guys are saying that the controller is 'dumbing' it down to avoid overheating or something. I know there is 19 Volts going into the controller and only 13.1 coming out (losing a bit in the cables as mentioned) so the problem seems to be with the controller. Leonics is indeed Chinese. It wasn't super expensive - about $300 USD. It is guaranteed for one year so maybe I just need to get them to 'upgrade' me to a different one.

There is no shading. The panels are mounted on a fit-for-purpose mount behind the hard top. There is a tiny bit at times from the VHF antenna but that's it. The cables may be slightly long - the controller is about 6 feet from the battery. I will chop those down as well and measure the Volts at the end of them as well.

Thanks again. Much appreciated - back to the vendor again I guess!

Derek

[Ex-Calif]

Originally Posted by millhouse_44

It seems logical to me that the controller is not sufficient for the amperage/watts/volts being produced given it has a 10 Amp max rating and 400 watt maximum input. I queried this when I got the controller from the vendor but they indicated that since the panels won't be 100% efficient all the time because of the fixed mount, I'll only probably see 350-400 Watts power maximum at any given time in any event.

It would seem more logical that the biggest 12V controller they have is 400w so that's what they sold you.

I went to their website and did some scrounging for a user guide or manual - zippo...

I glean from their marketing brochures that the controller can supply regulated 10 amps directly - hence the 10 amp "rating" Presumably you can hook up a 10 amp load (water pump etc) and as long as the system has 10 amps it will run the pump. This is in separate to the 400W array input capacity. So unless it is load connected I would disregard the "10 amp capacity" bit.

What you have is 540W of solar trying to be regulated by a 400W controller. I don't know if this Leonics controller is any good or not. I don't know if their MPPT charge regime is correct or not. I do know that I would be interested in the controllers on Socaldmax's list over Leonics.

[socaldmax]

Originally Posted by millhouse_44

Thanks for all the assistance! Sorry to 'hijack' the thread but I thought this was an appropriate thread to discuss 'power' output given the theme. Next time I will start my own but what I typically get when I do that it a lot of 'you should search this forum for other posts on the subject before posting a new thread' so it seems you can't win sometimes on here.

It seems logical to me that the controller is not sufficient for the amperage/watts/volts being produced given it has a 10 Amp max rating and 400 watt maximum input. I queried this when I got the controller from the vendor but they indicated that since the panels won't be 100% efficient all the time because of the fixed mount, I'll only probably see 350-400 Watts power maximum at any given time in any event. They assured me that the controller would be sufficient for the panel array but I'm sure it is not now. The array is pushing out lots of amps - about 20 amps at peak afternoon power with a good sun angle, but again only at 12.8 Volts. It seems logical what you guys are saying that the controller is 'dumbing' it down to avoid overheating or something. I know there is 19 Volts going into the controller and only 13.1 coming out (losing a bit in the cables as mentioned) so the problem seems to be with the controller. Leonics is indeed Chinese. It wasn't super expensive - about $300 USD. It is guaranteed for one year so maybe I just need to get them to 'upgrade' me to a different one.

There is no shading. The panels are mounted on a fit-for-purpose mount behind the hard top. There is a tiny bit at times from the VHF antenna but that's it. The cables may be slightly long - the controller is about 6 feet from the battery. I will chop those down as well and measure the Volts at the end of them as well.

Thanks again. Much appreciated - back to the vendor again I guess!

Derek

It actually produces 30 amps, the 10 amp rating is for the DC load output, you shouldn't be using that section.

Again, when you're seeing 13.1v, that's because the batteries are at 13.1v and you're pulling current for whatever is on at the time. The voltage won't rise until the batteries are close to fully charged. Since your batteries are never fully charged, you're not going to see 14.xx volts.

Really the only thing wrong with that controller is it might not actually be an MPPT, or the algorithms it uses aren't near as good as the higher quality MPPT controllers, and it's limited to 30 amps, or slightly over.

[carstenb]

Monte

Lots of guys on here who know oodles more than I do abot batteries etc.

But you cna cut your consumption by something between 60-80 amps per day quite simply and without sacrificing anything.

Simply turn your plotter screen brightness down to zero when you are not looking at it. The plotter still function, even though the screen is dark. Set your AIS guard zone adn it will still sound the alarm. SAme for RAdar (I, personally would set this for 15 minute sweep intervals and save more power - but to each his own)

When an alarm sounds or you want to get your GPS position, simply increase the brightness do what you need to do and turn it back down again

saves about 2-3 amps per hour.

[monte]

Thanks for the input and feedback and no problem with thread hijacking. It's good to have lots if different experiences in one place.

[Maine Sail]

Originally Posted by socaldmax

the output voltages that you are seeing are based on battery SOC, rather than potential charger voltage. This means that although the charger says it can put out 14.3v into your batteries, the actual voltage will be determined by how much current you're using at the time and what the battery voltage is.

+1 Read this over and over until it makes sense..

Originally Posted by socaldmax

Again, when you're seeing 13.1v, that's because the batteries are at 13.1v and you're pulling current for whatever is on at the time. The voltage won't rise until the batteries are close to fully charged. Since your batteries are never fully charged, you're not going to see 14.xx volts.

+1 !!!

Again this can not be stressed enough and many folks misunderstand how CC/CV charging works. A solar controller is simply:

Constant Current then Constant Voltage or a CC/CV controller.

Constant Current = The full current the charge source can provide.

Constant Voltage = The charge controller or regulator LIMITS VOLTAGE to the preset level.

You can't attain a terminal VOLTAGE until you have enough CURRENT at the right SOC for that CURRENT to get the battery bank to the limiting voltage. CV charging (absorption & float) is simply voltage limiting.

In BULK/CC the battery voltage is INCREASING >>>>>>>>>

At ABSORPTION/CV the battery voltage is HELD CONSTANT at the voltage preset point-------------

At FLOAT/CV the battery voltage is HELD CONSTANT at a reduced voltage ---------

[cwyckham]

You are getting the right answers here. There may be nothing wrong at all with your controller (other than it is slightly undersized) and a brand new one from a high end manufacturer probably won't help.


What is the current from the controller when the voltage is at 12.8V or whatever voltage you're seeing that is lower than the maximum?


To re-state Maine Sail's explanation in a slightly different way:


There are three phases. During the Bulk phase (and in your situation, you're probably always in bulk phase), the battery voltage is what the battery voltage is and the controller pours in as much current as it can.


The current from the controller will go to your DC loads and to the battery. As the battery fills up, the voltage will slowly rise. When the voltage hits the maximum setpoint (usually somewhat over 14V), the controller will now start to reduce the amount of current to hold that voltage for a set time period (this is called absorption) before dropping the current even further to bring the voltage down to "Float".


The controller controls Current, not Voltage. It decides how much current to send based on the battery's Voltage. The battery's Voltage is based on its state of charge.

[cwyckham]

Originally Posted by millhouse_44

Thanks for all the assistance! Sorry to 'hijack' the thread but I thought this was an appropriate thread to discuss 'power' output given the theme. Next time I will start my own but what I typically get when I do that it a lot of 'you should search this forum for other posts on the subject before posting a new thread' so it seems you can't win sometimes on here.

...Derek

Hi Derek,

It does get confusing sometimes when people are talking about two different things in one thread. Hence sometimes people will recommend a new thread unless it's just a quick aside.

When you post a new thread and others recommend that you search for existing threads, they don't usually mean so that you can post in them. they usually mean they think the answer is already in the archives and you don't need a new thread at all.

If you've read the archives and your question isn't answered, then a new thread is certainly fine. In this case, you have a very specific problem and I'm sure the answer isn't in the archives.

[Ex-Calif]

Originally Posted by cwyckham

The current from the controller will go to your DC loads and to the battery. As the battery fills up, the voltage will slowly rise.

Three great posts from Socal, Mainesail and CW...

I didn't want this thought to get lost.

If the boat is drawing 20-30 amps and your solar array is producing 30 amps there is little/no battery charging going on...

Some people forget that.

[DeepFrz]

What everyone seems to be missing is the input voltage. The MPPT tracking range of that controller is 26 - 75 volts. The OP has stated he is getting 19 v. at the input to the controller. Some of his panels should be in series to increase the input voltage.

[Ex-Calif]

Originally Posted by DeepFrz

What everyone seems to be missing is the input voltage. The MPPT tracking range of that controller is 26 - 75 volts. The OP has stated he is getting 19 v. at the input to the controller. Some of his panels should be in series to increase the input voltage.

Good catch - the devil is in the details...

[roetter]

Hi Monte

I did not read the whole thread, but here is my recollection from our crossing in a L450 with two Hitachi 80's.

We also still had the 840Ah LA from Lagoon.
We had 950W solar, but same problem as you guys with many cloudy days and afternoon shading.
Used a small Honda 2000i initially every two days then every day until a wave gave it a good wash.
Then had to run one engine twice every night.
Solar kept up during the day and filled a little bit extra to make it to midnight for the first engine run.
Consumption about 25A (600Ah/day). Two Lagoon fridges plus two Dometic portable freezers, plus 2 plotters and radar most of the time due to many squalls.

Replacing the alternator with a high output one is quite costly.
I checked the voltages and found quite a drop in the cables from the alternator to the battery post, specifically from the port one due to the longer run.
I put in a Sterling alternator-to-battery charger and had a much improved amperage coming in and higher voltage at the battery terminals. However, we lost the boat soon after.
I don't think the Hitachi ever goes above 14.0V at the alternator. Together with more than 0.5V drop in the cables there is not much pressure left at the battery terminals to push the amps in.
The temperature reduction in output voltage from the regulator is pretty agressive, so it drops the voltage down pretty quick.

Doing long passages is not something we do often and at anchor the solar does just fine, so why spend all the extra money.

Out of frustration with low voltage alarms when using winches or espresso machine on LA I went to 1400A and upped the solar to 1800W.

Now we can be pigs on power at anchor. The wife is happy because we can even heat the shower water with excess power most days.

For crossings and as a backup I may get two 12V semi-flexible 100-150W each solar panels without a controller and hook them up to the batteries directly while orienting them towards the sun where ever there is no shade only when needed. Most times these panels would be stowed.

[sailinglegend]

Originally Posted by cwyckham

....The controller controls Current, not Voltage. It decides how much current to send based on the battery's Voltage. The battery's Voltage is based on its state of charge.

I thing these are confusing and misleading statements and don't help to understand what is really happening!

As Mainsail says a "Charge Controller" in its absorption or float stage is a Constant Voltage charger or a "voltage limiter". This voltage on the battery is what governs the current the battery can take. If the battery "wants" 30 amps at a certain State of Charge (SoC), then a 500 amp charger will not deliver any more current than a 50 amp charger. In this situation The battery decides what current it will take for a given SoC, not the charger.

The battery voltage at the end of bulk stage and the beginning of absorption stage will be a constant 14.4v and yet the SoC will be rising from 80% towards about 95%. The battery voltage is only based on the SoC when the battery is not under charge OR discharge.

[cwyckham]

Originally Posted by sailinglegend

I thing these are confusing and misleading statements and don't help to understand what is really happening!

As Mainsail says a "Charge Controller" in its absorption or float stage is a Constant Voltage charger or a "voltage limiter". This voltage on the battery is what governs the current the battery can take. If the battery "wants" 30 amps at a certain State of Charge (SoC), then a 500 amp charger will not deliver any more current than a 50 amp charger. In this situation The battery decides what current it will take for a given SoC, not the charger.

The battery voltage at the end of bulk stage and the beginning of absorption stage will be a constant 14.4v and yet the SoC will be rising from 80% towards about 95%. The battery voltage is only based on the SoC when the battery is not under charge OR discharge.

I think you're right. I've re-read it a few times and I was bloody confusing. Thank you for taking the time to clarify.