solar charging

we try to camp off grid as much as possible, but find  the  original 80watt solar panel is inadequate. i then used a portable 100watt jobby to supplement this. not much better. i have bought a portable 200watt panel. obviously with the inclement weather this is still boxed! the 100watt panel uses a 10amp controller and the 200watt has a 20amp. my question is. can i fit both controllers to the leisure battery, 105amp lithium, simultaneously or am i heading for trouble. my reason for opting for portable is non interference of original fitting, and always a possibility of transfer to alternative vehicles. thankyou for any replies.
Doug.

Yes - different controllers with different power outputs can be connected to the same battery.  If your Sargent solar setup is the same as mine was, you may benefit by routing your 80w panel through a better controller that bypasses the EC700.  Many on the Forum have done this.

thanks for reply Nigel. perhaps if i had your expertise this could be a consideration. with my technological skills being hampered by a non active brainbox this is not!

Yes, it is possible to fit both to one battery but, what you are likely to find is that one panel will suppress the output of the other panel. That's because of slight differences in the "target" voltage at which each of the controllers change their charging mode (either because they are different makes/designs, or because of component tolerances).

This, for example, is likely to mean that the output of one controller is "fooled" into moving to its lowest-output mode because the output from the other controller raises the battery voltage higher than a single controller would "expect".

It is not likely to cause any harm to the battery, because the result will always be less charge going into the battery than the sum of the two systems - so no great risk of overcharging. That method (of connecting two charge controllers to one battery) always carries the likelihood that the two controllers will alter each other's behaviour (because they are not programmed to "understand" the voltage variations that the other controller is imposing on the battery).

The result is likely to be that one of the panels only really makes a significant contribution while the battery is heavily discharged. You can expect it to enter "float" mode relatively early and from then do very little in terms of adding to the battery's state of charge.

Roopert wrote:Yes, it is possible to fit both to one battery but, what you are likely to find is that one panel will suppress the output of the other panel. That's because of slight differences in the "target" voltage at which each of the controllers change their charging mode (either because they are different makes/designs, or because of component tolerances).

This, for example, is likely to mean that the output of one controller is "fooled" into moving to its lowest-output mode because the output from the other controller raises the battery voltage higher than a single controller would "expect".

It is not likely to cause any harm to the battery, because the result will always be less charge going into the battery than the sum of the two systems - so no great risk of overcharging. That method (of connecting two charge controllers to one battery) always carries the likelihood that the two controllers will alter each other's behaviour (because they are not programmed to "understand" the voltage variations that the other controller is imposing on the battery).

The result is likely to be that one of the panels only really makes a significant contribution while the battery is heavily discharged. You can expect it to enter "float" mode relatively early and from then do very little in terms of adding to the battery's state of charge.

Roopert - what you say makes sense to me but I'm not an electronics man.  I discussed this some time ago with someone who is and he said there is no problem having two controllers connected to the same battery and he has exactly that on his Nuevo, one controller being for a portable solar panel.  Both controllers are MPPT, I don't know if the same would apply if one was PWM.  I just did this google search and came up with this:

https://diysolarforum.com/threads/multiple-mppt-solar-charge-controllers-to-the-same-battery-bank.72263/

PS: Just found this old e-mail:

I know from what you have said and observed that two SPs connected to the same battery, each though their own MPPT regulator, will charge the battery just as effectively as two SPs connected in parallel through one MPPT regulator. Why doesn’t the charging voltage from one regulator affect the other?

These are intelligent chargers, when you measure the Battery Voltages under charge you consider you are looking at the Voltage from the MPPT, you are not. The MPPT continuously monitors the Current and Voltage and varies its duty cycle. Two or more MPPT's, or an MPPT and a PWM  Controller, will synchronise and use the second MPPT Voltage and Current to increase the duty cycle when needed in a fraction of the time it takes your brain to think about the question. When the Battery is charged both will back off accordingly. MPPT's from different manufacturers have different algorithms and can be observed performing their procedures accordingly.

sounds highly technical. i shall try the panels in triplicate as soon as .thanks for input.

Caraman wrote:I discussed this some time ago with someone who is and he said there is no problem having two controllers connected to the same battery and he has exactly that on his Nuevo, one controller being for a portable solar panel.

It would be nice to think that two solar controllers could somehow "synchronise" with one another. But the fact remains that each solar controller has no way to know about the existence of the other. The primary factor that a charge controller uses to determine the state of charge of a battery is by monitoring the rate of change of voltage over time. If two controllers are simultaneously trying to change the voltage of the battery, the internal "model" of the battery that each uses will be incorrect. Unfortunately that is unavoidable.

As I said, there should be no risk at all of any damage, but you won't get the full benefit of both panels.

Roopert wrote:

Caraman wrote:I discussed this some time ago with someone who is and he said there is no problem having two controllers connected to the same battery and he has exactly that on his Nuevo, one controller being for a portable solar panel.

It would be nice to think that two solar controllers could somehow "synchronise" with one another. But the fact remains that each solar controller has no way to know about the existence of the other. The primary factor that a charge controller uses to determine the state of charge of a battery is by monitoring the rate of change of voltage over time. If two controllers are simultaneously trying to change the voltage of the battery, the internal "model" of the battery that each uses will be incorrect. Unfortunately that is unavoidable.

As I said, there should be no risk at all of any damage, but you won't get the full benefit of both panels.

but how do you get the full benefit of both panels?  

• Connect them in series with one larger higher voltage controller but if one generates a lower power than the other, because it's smaller or in the shade, it will drag down the other to the lower power? 
  
• Connect them in parallel with one larger controller but if one has a lower voltage it will drag down the other to the lower voltage.  This means the portable panel should be matched by voltage to the fixed 80w panel which I have discovered not all are.
  

Peter Brown wrote:Any interconnection between panels should be done before the controller, using two controllers introduces the inefficiencies that Roopert mentions.

If you want better harvesting early morning, evening and in the winter connect the panels in series, this increase the potential voltage per light conditions.

If you want to harvest the maximum energy in good light conditions, connect the panels in parallel.

Personally I find that in the UK summer an 80w panel is fine for a couple of weeks off grid without travelling but no tv.

So do you recommend that the OP connects his 200w folding solar panel to his battery through its own controller, or, replaces the controller for his fixed 80w panel with a single larger controller for both panels that bypasses the EC700?

Yes but the OP has already bought 2 x portable different size solar panels (100w & 200w) to supplement the 80w panel on his roof, each having its own controller.  My question is, is he better off connecting his 3 x controllers in parallel with each other to his LB, or, connecting his 3 solar panels to 1 x controller that's good for at least 380w of solar panel?  If the latter and he connects them in series, the voltage will be higher but the current will be dragged down to that of the 80w panel which is no good. If he connects them in parallel, the current will be higher but the voltage will be dragged down to the lowest voltage of one of his solar panels.

well i'm completely flummoxed. had no idea charging a battery could be so simple/complicated ! think i might just forget the whole schemozzle and stick to ehu. thanks for all replies anyway!
doug

I'm not trying to dissuade you from connecting multiple controllers to one battery.  Far from it as my research suggests many do it and it works.  If it was me though, I would want to come up with a better way of connecting to the LB than wires trailing through an open window, behind the seat and crocodile clips.  Any lead coming off the LB's positive terminal should also have an appropriate in-line fuse close to the terminal.

Nigel. i'm probably completely wrong but the factory fitted panel is 80w. i have introduced a 100w portable. when i used this setup the battery was flat within a couple of days. i'm assuming the 80w controller is preventing the extra 100w being used. likewise i assume the 200w panel will be the same.

Doug - others on this thread have cast doubt that connecting two controllers to the same battery will work but unhelpfully they haven't said what will work when the solar panels are dissimilar like yours.  I suspect they haven't tried connecting two controllers to the same battery and therefore are only theorising.  I haven't tried it either but I have read of plenty of people who have and say it works.  

Ian has suggested you should fit a dual battery MPPT controller.  I have done this by replacing Sargent's controller which in this long 2020 thread has been categorised as a first generation 1980s technology 2-stage controller that has long since been superseded by PWM and now MPPT controllers which are infinitely better.  I do not know if your EC700 still has this controller but if it does I strongly recommend it is unplugged from the EC700 and replaced with a new MPPT controller that bypasses the EC700 as per the 2020 thread:

https://www.autosleeper-ownersforum.com/t32226-ec700?highlight=EC700+solar+regulator

I'm late to this but has anyone suggested connecting the smaller panel to the VB and the larger one to the LB? Separate controllers (NOT Sargent) and separate well sized wiring directly to the respective batteries. The effect of any small cross feeds between batteries due to any issue within the Sargent elechronics is likely to be negated by the excess resistance in the Sargent cabling.

It seems to me (without any electronics knowledge) but with extensive experience of mixing multiple battery charging means in the marine field (e.g. mixing generator, main engine and shore power charging) that any attempt to mix dissimilar panels, dissimilar controllers, dissimilar batteries or dissimilar wiring is bound to lead to a lowest common denominator situation, which is fine if you have good charging outputs available but not if trying to eke out the best efficiency from very limited solar panels.

The Bargee wrote:I'm late to this but has anyone suggested connecting the smaller panel to the VB and the larger one to the LB? Separate controllers (NOT Sargent) and separate well sized wiring directly to the respective batteries. The effect of any small cross feeds between batteries due to any issue within the Sargent electronics is likely to be negated by the excess resistance in the Sargent cabling.
....

I think the OP's problem has been his LB going flat rather than his VB.  But, if he is doubtful that connecting two controllers to the LB works and he doesn't want to meddle with his Sargent solar setup what he could do is switch the solar charge on his EC700 CP to his VB i.e. not smart or LB, and then connect the controller for his larger 200w folding panel directly to his LB.  This would help immensely with his LB charging especially if his folding panel controller is a reasonable one that supports Li batteries.  As many of us have found out, not only is the Sargent controller and wiring poor so is its associated so-called smart solar charging regime.  The Sargent controller mine came with was not configurable for a Li.  If this is still the case, it is surely another reason for its poor performance on the OP's van which has a Li LB.

Caraman wrote:

The Bargee wrote:I'm late to this but has anyone suggested connecting the smaller panel to the VB and the larger one to the LB? Separate controllers (NOT Sargent) and separate well sized wiring directly to the respective batteries. The effect of any small cross feeds between batteries due to any issue within the Sargent electronics is likely to be negated by the excess resistance in the Sargent cabling.
....

I think the OP's problem has been his LB going flat rather than his VB.  But, if he is doubtful that connecting two controllers to the LB works and he doesn't want to meddle with his Sargent solar setup what he could do is switch the solar charge on his EC700 CP to his VB i.e. not smart or LB, and then connect the controller for his larger 200w folding panel directly to his LB.  This would help immensely with his LB charging especially if his folding panel controller is a reasonable one that supports Li batteries.  As many of us have found out, not only is the Sargent controller and wiring poor so is its associated so-called smart solar charging regime.  The Sargent controller mine came with was not configurable for a Li.  If this is still the case, it is surely another reason for its poor performance on the OP's van which has a Li LB.

Yes indeed! I was simply trying to think of a way of deploying the OP's new 200 watt panel in the most effective way. 

Simply setting the existing installation to VB only and installing the portable panel to LB only (direct) may well be all that is needed for the OP's needs, and if the new controller (connected direct to the LB) is Li configurable then even better.

However it may still be better to intercept the existing solar controller output (two wires) and take it straight to the VB (i.e. bypass the Sargent), which should be a very simple wiring exercise. I think I recall that just one of the issues I had with my EC700 was that the Smart/VB/LB selections seemed to change at the whim of the Sargent, so for example if I selected "LB only" then I could not rely on the selection staying that way! I had to keep checking!

Certainly the advised reason for my original total and calamitous EC700 shutdown (which in large part prompted total removal of my Sargent installation) was voltage spikes from the Sargent solar controller, so on that basis alone there may be good reason to separate all solar outputs from the Sargent system. We have seen another thread recently concerning over-voltage issues which can only be due to problems with the Sargent solar controller and seem reminiscent of the problem I had.

You're probably right about wiring the Sargent controller direct to the VB (just as my Votronic DuoDig is).  However, when I still had the Sargent setup it defaulted all the solar charge to the VB whenever the EC700 was shutdown.  During a couple of predominantly winter Covid lockdowns when the van was SORN'd with the EC700 shutdown, I found this was sufficient to keep the VB charged despite having a vehicle alarm and regularly going in and out of the van using the central locking.  The LB managed without charge as when the EC700 is shutdown its only load is the tracker.

Others may comment on this but if the OP's preference is being off-grid, relying solely on a folding solar panel (rather than a roof panel) to charge the LB may limit the places he can go.

Caraman wrote:

Others may comment on this but if the OP's preference is being off-grid, relying solely on a folding solar panel (rather than a roof panel) to charge the LB may limit the places he can go.

Despite my limited experience of solar I have realised that there is a massive difference between a good solar controller with amply sized wiring throughout compared to a poorly wired and inefficient installation. We have 3.5 times the nominal panel capacity now, but perhaps 10+ times the charge rates compared to what we saw with the original installation, such that since about April when I installed these I have never felt the need to plug the van in, home or away. On that basis my recommendation to Doug would be to flog the panels he has, fill any space on his roof with matched good quality panels, run new amply sized wiring, and fit a good MPPT controller. Proper job!

the 80w fixed panel and Sargent off allows both batteries 13.2v. will try adding the 300w two portable panels when weather permits. if this fails i'll be in the pub!

Caraman wrote:Doug - others on this thread have cast doubt that connecting two controllers to the same battery will work but unhelpfully

If you read what "others" have actually said, nobody has cast doubt (as far as I can see) that it will work. All that the "others" have said is that it is not likely to give you the full benefit of both (or all three) panels.

As you (and others) rightly say, the optimal solution if you need to deploy multiple panels is to have several identical panels. But in the real world, that may not be possible - in which case there is no simple, perfect solution.

If I were in that situation, I would aim to use two panels in series, because (for my use) that would be likely to give the best overall solution - because I tend to go north rather than south outside of the summer months, and so I value low-light performance. Obviously that would require a controller with an adequate voltage rating. Having two non-identical panels in series is of course not optimal - but it won't be a disaster.

Back to the OP's existing situation: It seems very likely that there is a fault somewhere, unless his typical daily 12V use is unusually high. We have a single 150W panel on the Trooper, and it is self-sufficient in terms of 12V for 3-seasons use anywhere in the country, and will maintain both LB and VB throughout the winter. There's no way to know where the OP's problem lies without further investigation. At the simplest level, he could measure the open-circuit voltage and short-circuit current of each of the panels (disconnected from each controller) in full sunlight, which would show whether any of them has failed. When the first panel on the Trooper failed (after less than 2 years) the open-circuit voltage of the panel dropped to approximately 12V - which meant that it could contribute nothing to the battery.

On my older 2014  nuevo the max output for the OE set up is 120w  ,  not realy any roof space  more panels , I have a 200w portable  solar panel with mppt controller , working with OE sollar works fine ,the portable panel pointing at the sun greatly increases the sollar harvest . I use my 200w panel to charge  my 1800 w bluetti that gives me off grid 240 volts to all My 240 needs including micro wave oven .