Solar panel controller

[Yoshimura]

I might add a sola panel to my Roadtrek and I'm wondering how this works when the underhood generator runs or when connected to shore power with inverter charging the battery. Does the solar controller only charge the battery when it detect that no other device charge the battery?

[hbn7hj]

Some do consider the voltage of the battery they are charging and some do not. Mine does not. you will have to check the manual for your controller.

[Winston]

Our system includes three separate and independent charging sources all tied 'in parallel' across the batteries. We were uncertain whether these three devices (a Magnum 2812 combo charger/inverter; a 2nd alternator with Balmar regulator; and a Midnite Solar Classic controller) would all play 'nice' together. Our concern was whether any of the charging sources might ‘sink’ current, that is, attempt to ‘pull-down’/force the battery (and other chargers) to its lower programmed voltage. (Think of connecting a 6 volt battery across a 12 volt battery - - the 6 volt battery with “sink” (accept) lots of current in its futile attempt to force the 12 volt battery down to the 6 volt level). As we were unable to obtain schematic diagrams of these three devices, we 'crossed our fingers', connected everything together and ran tests. Yes, they are very compatible, each doing what it had been programmed to do. Each of the chargers essentially switching to idle/standby when its programmed voltage was exceeded. No current sinking occurred.

A caveat. We program our chargers as Constant Voltage devices. We do not employ any fancy algorithms. It is likely that connecting multiple charging sources in parallel will confuse smart chargers that rely on battery voltage and current to determine mode switching thresholds. Some experimentation and creativity may be required. But, for us, the good news was . . . no smoke!

[rickst29]

Originally Posted by Yoshimura

.....Does the solar controller only charge the battery when it detect that no other device charge the battery?

Good Solar Controllers "sniff" the voltage of the "battery +" output circuit, relative to ground, very frequently. If the Alternator under the hood is trying to charge it's battery at high voltage, or maintaining the Voltage at a point above the Controller's "boost cutoff" (which is near the float voltage), the charge controller will fall into float mode. It thinks that the batteries are charged, even though that might not be completely true WRT the "house" batteries.

You might raise "float voltage" of the Solar Controller a little bit, to exceed engine operating voltages (The ECM and alternator will try to keep around 13.5, although this varies from on manufacturer to another). That way, the Solar Controller will stay in boost mode a little longer. Also check your maxmium boost time, to assure that it doesn't hit the timer limit before hitting the voltage limit.

[themexicandoctor]

Originally Posted by Winston

Our system includes three separate and independent charging sources all tied 'in parallel' across the batteries. We were uncertain whether these three devices (a Magnum 2812 combo charger/inverter; a 2nd alternator with Balmar regulator; and a Midnite Solar Classic controller) would all play 'nice' together. Our concern was whether any of the charging sources might ‘sink’ current, that is, attempt to ‘pull-down’/force the battery (and other chargers) to its lower programmed voltage. (Think of connecting a 6 volt battery across a 12 volt battery - - the 6 volt battery with “sink” (accept) lots of current in its futile attempt to force the 12 volt battery down to the 6 volt level). As we were unable to obtain schematic diagrams of these three devices, we 'crossed our fingers', connected everything together and ran tests. Yes, they are very compatible, each doing what it had been programmed to do. Each of the chargers essentially switching to idle/standby when its programmed voltage was exceeded. No current sinking occurred.

A caveat. We program our chargers as Constant Voltage devices. We do not employ any fancy algorithms. It is likely that connecting multiple charging sources in parallel will confuse smart chargers that rely on battery voltage and current to determine mode switching thresholds. Some experimentation and creativity may be required. But, for us, the good news was . . . no smoke!

Winston,

I pay attention to your posts.

In fact I just sent a pm to Booster asking his opinion.,

You say "our chargers", are you an installer?

And by ditching the Victron algorithm driven systems, etc in favour of "constant voltage devices", do you believe you are achieving* more performance, longer battery life, by doing so even though there are some other known limitations** in doing so?

And again all this happens in part by wiring* directly off the shunt? I ask these questions because I might be interested in rewiring my systems, to do so, if there is a measurable difference in overall efficiency, not because I understand it.

*I have seen it in my truck, right now its a shiny post that some stuff connects to.

*the best performance possible
**way beyond my understanding today, maybe I will be better infomed next Friday

[themexicandoctor]

This is what I understand my shunt to be;

By the way, I have never chosen to go deeper into understanding my system because I purchased the Victron components to do that & I paid the people, who did know.

Epecially the last person, a quiet & unassuming professional who worked on my van was an Electrical Guru from trade school & then 40 years of having real world experience as Southern California owners bring "irredeemable Electrical systems on rvs & boats to him because everyone knew down here, if Marc Roundry cannot fix it, it is beyond help ..."

Marc just closed West Coast Marine & RV Electrics down, a week before Covid 19 started.

He was the Guy.

And he was very patient & exacting.

I am NOT looking for another Guru, simply trying to ascertain whether I am running at a 2, 10, 25% loss & is it worth the investment to revamp my 2 year old system or wait another 5 years.

If its 11% loss, I am splitting hairs.

Or even 15%.

But if its more, I am motivated.

[themexicandoctor]

The shunt - if you need better photos, please let me know - it does look like one Victron component is connected to the shunt?

[rickst29]

We can get a hint from Solar setups which have been "split" into multiple controllers sharing one bank of batteries, in order to figure out what will happen here. On Internet I have two "pure-Trailer" friends with configurations where massive Solar arrays are split in half - sharing the same battery bank, charged by two Solar controllers.

When the whole "coach-side" system is showing low Voltage on the +12 VDC bus (due to a high power consumer, such as a non-compressor fridge running on 12V or a too-loud stereo set ), OR the batteries are just plain "too low", then everyone will want to charge.

They only fall into "float mode" when one of the chargers "drops out" to conduct a Voltage Test, and finds (just for itself) that the other chargers are running the bus at nearly float stage already. It then makes a "wrong decision", falling from "Bulk mode to down to "float mode".
- - -
But that only happens when the OTHER chargers can maintain a Voltage above "Float" Voltage, all by themselves. Other people who have dual Solar Arrays on a pure trailer have reported that there's only a small increase in total charging time for having 2 dumb controllers (testing independently) versus expensive controllers linked in (ahem, sorry about the terminology) a "master-"slave" relationship. (All on a single battery bank, obviously.) The concluded that the Master/Slave capability isn't worth the extra money, unless it was "built in for free, already there" or you're running at least 3 Solar controllers.

So my advice is, just leave the alternator (and possibly the BIRD) "fooling" the Solar sometimes, while in motion. The alternator "floats" everything during the drive, but Solar will still do a great job at camp (with the engine off.)

[booster]

Originally Posted by rickst29

We can get a hint from Solar setups which have been "split" into multiple controllers sharing one bank of batteries, in order to figure out what will happen here. On Internet I have two "pure-Trailer" friends with configurations where massive Solar arrays are split in half - sharing the same battery bank, charged by two Solar controllers.

When the whole "coach-side" system is showing low Voltage on the +12 VDC bus (due to a high power consumer, such as a non-compressor fridge running on 12V or a too-loud stereo set ), OR the batteries are just plain "too low", then everyone will want to charge.

They only fall into "float mode" when one of the chargers "drops out" to conduct a Voltage Test, and finds (just for itself) that the other chargers are running the bus at nearly float stage already. It then makes a "wrong decision", falling from "Bulk mode to down to "float mode".
- - -
But that only happens when the OTHER chargers can maintain a Voltage above "Float" Voltage, all by themselves. Other people who have dual Solar Arrays on a pure trailer have reported that there's only a small increase in total charging time for having 2 dumb controllers (testing independently) versus expensive controllers linked in (ahem, sorry about the terminology) a "master-"slave" relationship. (All on a single battery bank, obviously.) The concluded that the Master/Slave capability isn't worth the extra money, unless it was "built in for free, already there" or you're running at least 3 Solar controllers.

So my advice is, just leave the alternator (and possibly the BIRD) "fooling" the Solar sometimes, while in motion. The alternator "floats" everything during the drive, but Solar will still do a great job at camp (with the engine off.)

I think there are very specific circumstances that different brands of chargers and controllers have issues. In the trailer case, they appear to have the typical startup test of voltage to determine if a charge cycle is required. If any other charge source is holding up the voltage when the controller is activated, or in this case shuts down to look, it will think it is looking at the battery voltage and not charge. That "feature" in chargers controllers can cause all kinds of cases where they undercharge by going to float. Many/most chargers also do that same check, including shore chargers, B to B chargers, and alternator regulators (including Balmar).


The problem with that kind of system is that it is often almost impossible to get the charger to actually get into a charge cycle if you want to because the batteries really are low, and many of the controllers and chargers, once in float won't go up to full charge when the other source is removed unless the voltage drops quite a bit.


Using two solar controllers will work OK if they are the same model and on the same setting with wiring that doesn't give on more voltage drop than the other. It only really makes any difference once you get to full absorption voltage if they don't match as on will not put out full current if it running at lower voltage at the tie together point. When you are still in bulk, the system voltage is below both of the mismatched controllers running setpoints, so both will be putting out full power.


These are the kinds of issues that cause people to say that their sources "don't play well together", and there are really not very many ways to not have it happen. In the case of the trailer controllers, if they didn't shut down once running to check non charge battery voltage, the problem would go away except and initial startup of the solar if on some other charger first. Checking voltage in the middle of the charge cycle, is IMO, not a valid check anyway to tell if the battery is full. You have deal with surface charge, voltage drop from loads, etc so very poor an indicator of SOC.


About the only way to truly get the systems to play well together is to have them centrally controlled off of actual battery SOC particularly at full charge. With lead acid about the only way to accurately tell true full is by battery charging amps to the battery at absorption voltage. With lithium, you can get by on voltage in most cases. In lead acid batteries, you can do it by having solar controllers and chargers that run off of internal or external battery monitors on a common shunt that is measuring battery amps. The controllers and chargers don't care where the amps are coming from, just what they are, and they control the same if they are furnishing the amps or another source is. Very accurate charging achieved every time, on their own. Winston's system is suited to lithium and he would be able to explain how he handled it all for them.


One thing that may come up with the system you are looking at would be the lack of float when there is only one battery in the system, so low capacity. Depending on how the hysterisis is on the charger, which is hard to have precise because of the low voltage drop with discharg, the battery could be quite low at any given time, so if the charging source is removed then, that would be the discharge capacity starting point for that cycle and lower available power.


Every system is different and will have different interactions, so it is very important to look at how each of the systems actually handles the charging profile and control. Things like checking the voltage mid cycle would be a big no-no in multiple source systems where they are on at the same time, for instance. Learning how to fool the systems is often also beneficial. Things like throwing on a bit load to lower voltage to get a charger to go into a full charge cycle is the battery has surface charge or a wimpy solar output is holding up the voltage just enough to prevent the full charge start.

[rickst29]

Originally Posted by booster

<< Big snip by rickst29, there was good stuff in it >>
....Every system is different and will have different interactions, so it is very important to look at how each of the systems actually handles the charging profile and control. Things like checking the voltage mid cycle would be a big no-no in multiple source systems where they are on at the same time, for instance. Learning how to fool the systems is often also beneficial. Things like throwing on a bit load to lower voltage to get a charger to go into a full charge cycle is the battery has surface charge or a wimpy solar output is holding up the voltage just enough to prevent the full charge start.

Surprisingly, (or anyway - it sure surprised ME) a pair of cheaper EPEVER controllers (BN series) scanning the bus independently, takes only a little longer to reach "float" in both controllers, than a pair of more expensive Master/Slave "Trion" controllers. But the advantage for Trion increases with the number of controllers, and the size of the battery bank.

Your hint about putting load to "drag it down, force another Boost/Asborb cycle" is spot-on. My 'BN' controller with 'MT50' does not offer a button sequence to "dang the torpedoes, go back into boost mode", and there have been a couple of times when I would like to have done that. (Sort of a "charge wizard" button for the Solar Controller). But I've gotten so handy with the MT50, I can drop the "Boost return" pretty fast when I want to. EpEver is the brand I'm most familiar with, because they're so darn cheap. And so am I .

[Winston]

Originally Posted by themexicandoctor

You say "our chargers", are you an installer?

And by ditching the Victron algorithm driven systems, etc in favor of "constant voltage devices", do you believe you are achieving* more performance, longer battery life, by doing so even though there are some other known limitations** in doing so?

We write in the first person plural as a habit dating from our ‘professional days’ where our letters were written on behalf of the ‘entire company’. No we’ve never been involved in RV installations other than our first (and hopefully last) ProMaster van conversion.

“Bulk, Absorption, and Float” are terms developed for lead-acid/AGM batteries and have no relevance to lithium. If there is a charge profile specifically intended for lithium batteries, we have yet to find it, or even a good thread/discussion of what it should be. Since lithiums can generally accept charge rates greater than any charger can produce, our goal is “to give it everything the charger has to give” until a target charge level is achieved. In this connection we use Constant Voltage chargers which are really not pure constant voltage. If one were to put a ‘real’ Constant Voltage, say 14 volts, across a lithium battery whose terminal voltage was, by way of illustration, 13.4 volts, the resulting current would be monumental and resulting fireworks, spectacular. The reality is that charger limitations and wire resistance serve to limit the current at levels tolerable by both charger and battery.

In choosing a lithium charge profile we first ask “do we want to charge the lithium battery to 100% SoC each charge cycle." The answer is probably not. There is evidence that maintaining a lithium battery at 100% SoC shortens the life of lithium batteries. As we’ve reported in other threads, we have run numerous full discharge tests. We manually charge the pack until each of the cells has reached its high voltage ‘knee’ where further charging sends the cell voltage dramatically higher and rapidly; then discharge the battery in 10% increments waiting a minium of 10 hours between each discharge segment. The resting voltage (after 10 hours) is measured/recorded.

We found that 13.36 volts repeatedly resulted at 90% SoC. So 13.36 volts became our target charge level. But alas, none of our charges allows programming with this precision so we’ve settled on 13.4 volts. We run our Midnite Solar Controller and our Magnum Charger full-time at 13.4 volts. Our Balmar regulator failed and we’ve replaced it with a DIY Constant Voltage regulator which we have adjusted to limit alternator temperatures (when driving). A voltage of 13.8 volts provides a charge rate of 150 amperes when the battery is below 70% SoC and it drops to 100 amperes or less (common of all constant voltage charge sources for both lithium and lead-acid) as the battery charges.

The above may be interesting reading but as we noted in our first post, it’s irrelevant unless you have lithium batteries. We’d stick with the Bulk, Absorption, Float algorithms if you have lead-acid/AGM and experiment how to make the various chargers play ‘nice’ with one-another.

[Winston]

Originally Posted by rickst29

Surprisingly, (or anyway - it sure surprised ME) a pair of cheaper EPEVER controllers (BN series) scanning the bus independently, takes only a little longer to reach "float" in both controllers, than a pair of more expensive Master/Slave "Trion" controllers.

What is the objective in having two controllers?

[booster]

From what Winston says, rather than 14.6v and shutoff, having the plain old constant voltage PD charger that runs at 13.6v, as long as you could get one with full shutoff and auto restart.


Our Magnum on CC/CV would be capable of that as it will do a full charge, shut off until a setable restart point and then repeat.


There seem to be lots more of the lithium specs that want to limit the charge rate to lithium batteries lately showing up. Winston, what have you seen, opined, on them? Any idea of if and how much faster charging might be detrimental?

[Winston]

Originally Posted by booster

Our Magnum on CC/CV would be capable of that as it will do a full charge, shut off until a setable restart point and then repeat.


There seem to be lots more of the lithium specs that want to limit the charge rate to lithium batteries lately showing up. Winston, what have you seen, opined, on them? Any idea of if and how much faster charging might be detrimental?

What model Magnum do you have? Our 2812 'seems' to operate on the principal that once the charger is on . . . it stays on. When the battery voltage reaches the programmed Magnum voltage, the ammeter and other current indicators show the battery vacillating between small charge and discharge currents. This could, we suppose, be the Magnum cycling on and off, but we've always assumed that small load changes and measurement errors were responsible. Ultimately, our ideal charger would be a power supply. When the power supply voltage equals the resting voltage of the battery, no current flows to or from the battery and the power supply acts, well, just as a power supply should - - it supplies any power required by any/all connected devices. For this reason we prefer that the charger output remain "on" at all times - - always ready to pick-up any load that's connected.

Concerning lithium charge current limitations, we have seen some of the discussions on this forum on that topic but as we already have out battery pack, we've not been scanning the sales literature as conscientiously as we did when we were initially in the market. It seems that many of the “drop-in” lead-acid replacement lithium batteries have low charge and discharge limits which we assumed to be a function of the internal wiring/interconnection of the many smaller cylindrical cells comprising these batteries. Have you found larger prismatic lithium cells with similar low charging current limitations? Maybe Markopolo should weigh-in on this one.

In any event, our GBS batteries can be charged at 3C . . . that's 1500 amperes - - thus our comment that the limiting factor, for us anyway, will always be the chargers themselves.

[booster]

Here is a profile from the Magnum ARC50 remote that controls the charging profile and it itself is getting it's data from the battery shunt.


https://www.magnum-dimensions.com/si...ARC_CD_Web.pdf


Page 28 is where the profile and descriptions are.






I know you can set the end of absorption time to trigger on time or amps to the battery, and might be able to do it on SOC from the built in monitor also. I think going by the acceptance amps of the batteries (return amps) at your trigger point, it would do what you want to do as shown in the profile. Ours is on a MS2000

[themexicandoctor]

I just realized something.

Sometimes when the Solar is charging throughout the day, the new MPPT Charger has a little info message;

WHY IS THE CHARGER OFF?

Because I rarely turn it on unless I need to charge something.

AM I MISSING SOMETHING IMPORTANT HERE?

IS MY MAGNUM CHARGER SUPPOSED TO BE ON WHEN THE SOLAR IS ON?

I believed they were independent of each other?

[rickst29]

Originally Posted by Winston

What is the objective in having two controllers?

Good question, because it's not directly applicable to Class B. I used the example to describe why "arguments" between the on-board converter and the Solar Controller are mostly harmless, in the same way as the tested example.

With that clarification why I even brought it up, it IS applicable when the Solar Array is huge (big RV, not class B), generating two much power for one 'moderate-priced' Controller, but easily handled by twins. Imagine this case (At this time, I have no idea how to track down the real one which I read about): 1100 watts on the roof, divided into 600+500 watt arrays. A pair of 40A controllers could do a decent job, and each of the individual arrays could be wired in Series (lower current = smaller wires, less I-squared-R power loss).

And in that case, using a network of Master/Slave controllers was only a tiny bit faster than using independent controllers, in time to reach final "float mode" on all controllers. I conclude that the same relationship exists between a plugged-in onboard Converter and a Solar Controller.

[booster]

One thing to always remember when comparing profiles and times in stages of the charging, when talking about wet cells.


The time to get to float is not any kind of indicator that the charging filled the batteries well or poorly. All it tells you is either the charger thought the batteries were full or the maximum timer ran out of time.


It all depends on the profiles, algorithms, timers, etc in the charging source. Very few of them do a very good job of getting batteries accurately charged, IMO.


The only way on the solar to compare controllers accurately, I think, would be how many watt hours of power were recovered in any particular amount of time, under the same conditions. This reading has to be taken at the controller(s) not the battery, so a monitor will not give that information unless there are no loads running at all the entire test time.

[rickst29]

Originally Posted by themexicandoctor

I just realized something.

Sometimes when the Solar is charging throughout the day, the new MPPT Charger has a little info message;

WHY IS THE CHARGER OFF?

Because I rarely turn it on unless I need to charge something.

IS MY MAGNUM CHARGER SUPPOSED TO BE ON WHEN THE SOLAR IS ON?

I believed they were independent of each other?

I presuming 'MAGNUM CHARGER' to be the plugged in Converter, right?

They are 'independent' in decision-making, because they are not interconnected in a master/slave relationship. But they do interact, because they share the same same +12V battery post. Every 20 seconds or so, the MPPT will momentarily stop charging, in order to test the battery voltage,. It may very well see "high voltage" on the battery post, because the Magnum is also charging the battery, and is capable of raising the voltage past the Solar "float mode" value all by itself.

It's only a 'wrong decision' if you care about the cost for shore power going through the Magnum. If that's a really big deal, you could switch off the Magnum (at it's circuit breaker) for the middle of the day. It would stop charging the battery, and Solar would be responsible for charging and maintaining the battery all by itself. But I wouldn't do that - it will wear down the circuit breaker switch, and I'd also forget to turn the 'Magnum' back on for evening use. I'd just let the Magnum 'dominate' whenever the RV is plugged in.

[booster]

Originally Posted by themexicandoctor

I just realized something.

Sometimes when the Solar is charging throughout the day, the new MPPT Charger has a little info message;

WHY IS THE CHARGER OFF?

Because I rarely turn it on unless I need to charge something.

AM I MISSING SOMETHING IMPORTANT HERE?

IS MY MAGNUM CHARGER SUPPOSED TO BE ON WHEN THE SOLAR IS ON?

I believed they were independent of each other?

Are you reading this on the Magnum remote? If so, what model remote?


The charger section only needs to be on when connected to shore power, so it can charge the batteries. The inverter section would be turned on if you are trying to use 115vac off the batteries.


Our charger comes on automatically when we plug in to shore power, I think there may be a setting to make it do that or turn it off, but I haven't looked.


If we aren't plugged in to shore power, solar running or not, the charger and inverter lights on the remote ARC50 are off. When we plug in the charger light comes on, but we can turn it off at the remote.


I have never seen that text on our Magnum remote display, so would have to look it up to see what it actually is saying, and why.