A 24 volt system has advantages for the inverter. The inverter in my UPS runs off 72 volts.
But you will need a 24 to 12 volt converter for a lot of accessories.
Whenarewethere said
04:37 PM Oct 24, 2022
Make sure all the solar controllers have a lithium profile.
Mike Harding said
05:54 PM Oct 24, 2022
I'll not address your drawings at the moment but rather make more generalised comment.
I'm not keen on PWM controllers and suggest *quality* MPPT which will enable you to use cheap, secondhand, higher voltage ex-house panels.
If I were wiring a caravan from scratch *without doubt* I would use 48V or at worst 24V - never 12V.
It seems to me there are basically two electrical situations with caravans:
1 - I wish to run the microwave, A/C and everything else from solar/batteries
2 - I wish to run everything except microwave/AC from solar.
I tent to 2 and to this end carry a generator for microwave/AC but use external solar for all else. My 800W solar panels charge via Victron 100V/30A MPPT 210Ah AGM which then runs a 500W Victron inverter which, via 240V and a time switch, charges the caravan for two hours per day this in addition to the caravan's own 100Ah AGM and 120W solar panel.
This is not the most efficient way to do things energy wise but, currently, it is by far the most convenient and as I have more solar than I need efficiency is not too important.
I do not support any caravan charging from the vehicle as I usually camp in one location for weeks rather than days however if you are moving daily or so then vehicle charging may be useful otherwise I see it as a needless complication.
Good luck :)
dogbox said
09:22 AM Oct 25, 2022
i don't see any fuses , at least if you have a fuse or two in the right places an something is not right you might not let the smoke out
Gundog said
09:57 AM Oct 25, 2022
The circuit diagram is a KISS one, fuses and circuit breakers would be normally be used on any circuit for power.
Origionally my drawing was incorrect as it was quickly picked up on batteries being set for 24v it was modified for 12v.
I was expecting some discussion on why would you use a solar controller conneted to the towing vehicle to charge house batteries. The thoughts are a normal direct connection to house battery from the tow vehicle will generally see 14.4v delivered initally to the house batteries and then it may settle back to 13.8v, the friend who has a similar setup on his rig rational for using a solar controller is it can use the algorithm to match the battery chemistry.
But no it wont work because the wires from the ute are crossed at the AP (an actual unintentional mistake in the drawing)
Think about usage generally the charging sources are for a specific purpose, solar whilst stationary and the from the ute whilst travelling, even when you stop mid journey the VSR disconnects the tow vehicle and the solar take over.
-- Edited by Gundog on Tuesday 25th of October 2022 10:01:41 AM
-- Edited by Gundog on Tuesday 25th of October 2022 10:08:53 AM
I think there is a possibility that having three different solar regulators set up like this that you may have one 'confusing' another with the result that you do not get the benefit of the all the available 'charge' going into the batteries. A suitable sized single regulator with all inputs going through it would be better (& would make future fault finding easier too). Multiple regulators can be used, but it is more common that they would be compatible with each other enabling 'daisy chaining' which effectively still creates a 'single' regulator using more than one unit thereby increasing current capacity.
Gundog said
10:22 AM Nov 2, 2022
Cuppa wrote:
I think there is a possibility that having three different solar regulators set up like this that you may have one 'confusing' another with the result that you do not get the benefit of the all the available 'charge' going into the batteries. A suitable sized single regulator with all inputs going through it would be better (& would make future fault finding easier too). Multiple regulators can be used, but it is more common that they would be compatible with each other enabling 'daisy chaining' which effectively still creates a 'single' regulator using more than one unit thereby increasing current capacity.
Charge controllers sense the internal resistance of a battery and send their current to the battery terminals based on the resistance of the battery. If the battery is at a low state of charge, the resistance will be low and the charge controller will charge in bulk mode (depending on the battery type).
If the resistance increases, the charging current will decrease because the battery is almost full.
If two or more charge controllers charge the same battery, the battery will be charged quicker. The multiple charge controllers will not compete with each other because they all sense the same internal resistance of the battery. If charge controller A puts in 100Watts, charge controller B will also put in 100Watts into the battery.
When you program your charge controller you can add the cutoff voltage in the software. That means if your battery reaches a pre-defined voltage, it will stop charging. You can tell charge controller A to charge to 12 volts and charge controller B to charge to 12.8 volts. This is not needed but is good to know because one charge controller might stop charging if it reaches that point, and you will be wondering why that is. Also, if the wires of charge controller A are a bit longer, it might enter float mode earlier than charge controller B because of the voltage drop (increased resistance).
If the charging current becomes too high, the internal resistance of the battery will change because of the heat generated. The charge controllers will then reduce their power input to the battery.
Cuppa said
08:22 PM Nov 2, 2022
Gundog wrote:
Cuppa wrote:
I think there is a possibility that having three different solar regulators set up like this that you may have one 'confusing' another with the result that you do not get the benefit of the all the available 'charge' going into the batteries. A suitable sized single regulator with all inputs going through it would be better (& would make future fault finding easier too). Multiple regulators can be used, but it is more common that they would be compatible with each other enabling 'daisy chaining' which effectively still creates a 'single' regulator using more than one unit thereby increasing current capacity.
Charge controllers sense the internal resistance of a battery and send their current to the battery terminals based on the resistance of the battery. If the battery is at a low state of charge, the resistance will be low and the charge controller will charge in bulk mode (depending on the battery type).
If the resistance increases, the charging current will decrease because the battery is almost full.
If two or more charge controllers charge the same battery, the battery will be charged quicker. The multiple charge controllers will not compete with each other because they all sense the same internal resistance of the battery. If charge controller A puts in 100Watts, charge controller B will also put in 100Watts into the battery.
When you program your charge controller you can add the cutoff voltage in the software. That means if your battery reaches a pre-defined voltage, it will stop charging. You can tell charge controller A to charge to 12 volts and charge controller B to charge to 12.8 volts. This is not needed but is good to know because one charge controller might stop charging if it reaches that point, and you will be wondering why that is. Also, if the wires of charge controller A are a bit longer, it might enter float mode earlier than charge controller B because of the voltage drop (increased resistance).
If the charging current becomes too high, the internal resistance of the battery will change because of the heat generated. The charge controllers will then reduce their power input to the battery.
When a charge controller senses the internal resistance of the battery what is it actually measuring? I'm guessing the measurement would have to be either voltage, or perhaps rate of voltage rise/fall over time? which perhaps in turn is interpreted as 'resistance' in the battery?
I wasn't aware that resistance was a matter of significance in Lithiums though, I thought that they had ultra low resistance & that the main parameter to determine when 'full' was a very small change in cell voltage - unlike in LA batteries where 'full' is determined by length of time held at a constant charge voltage. (with acceptance of charge dwindling as resistance increases).
I'm really just thinking aloud as Lithiums are beasts I have had no direct experience with. If it were me I would prefer to have all sources coming through the same controller if for no other reason than to be able to more easily monitor & understand what was going on, but you sound confident about what you want to do so give it a burl.
Gundog said
01:42 PM Nov 4, 2022
One thing that is often overlooked is different types of solar panels should not be mixed in the same string.
Its also better to have small strings attached to their own contollers.
For example origionally you had a set of folding portable panels say 100w with it own solar controller later you mounted 2x100w monocrystal panels and then added 2x120w polycrytal panels for best results each string will perform better with its own solar controller.
I have not or intend to use this diagram I have seen a similar setup to this however I have embelished it for interest sake.
bear in mind all solar controllers would have Lithium charging set points.
-- Edited by Gundog on Monday 24th of October 2022 03:46:45 PM
-- Edited by Gundog on Tuesday 25th of October 2022 09:32:07 AM
Yes, 24 volts!
Be careful that your MPPT controller is not dictated by the cheap controllers.
You may have to adjust the bulk to absorption up a touch. Same with absorption to float.
Or if you can adjust the cheap ones down a bit.
But at the very least thoroughly measure the amps out of each controller until you are happy with the order of cutoff of the MPPT.
It maybe ok as it is.
Second post in this thread is my experience with 2 MPPT controllers:
https://thegreynomads.activeboard.com/t68781260/questions-solar-charging/
I have modified the pic I think it right now.
A 24 volt system has advantages for the inverter. The inverter in my UPS runs off 72 volts.
But you will need a 24 to 12 volt converter for a lot of accessories.
Make sure all the solar controllers have a lithium profile.
I'll not address your drawings at the moment but rather make more generalised comment.
I'm not keen on PWM controllers and suggest *quality* MPPT which will enable you to use cheap, secondhand, higher voltage ex-house panels.
If I were wiring a caravan from scratch *without doubt* I would use 48V or at worst 24V - never 12V.
It seems to me there are basically two electrical situations with caravans:
1 - I wish to run the microwave, A/C and everything else from solar/batteries
2 - I wish to run everything except microwave/AC from solar.
I tent to 2 and to this end carry a generator for microwave/AC but use external solar for all else. My 800W solar panels charge via Victron 100V/30A MPPT 210Ah AGM which then runs a 500W Victron inverter which, via 240V and a time switch, charges the caravan for two hours per day this in addition to the caravan's own 100Ah AGM and 120W solar panel.
This is not the most efficient way to do things energy wise but, currently, it is by far the most convenient and as I have more solar than I need efficiency is not too important.
I do not support any caravan charging from the vehicle as I usually camp in one location for weeks rather than days however if you are moving daily or so then vehicle charging may be useful otherwise I see it as a needless complication.
Good luck :)
The circuit diagram is a KISS one, fuses and circuit breakers would be normally be used on any circuit for power.
Origionally my drawing was incorrect as it was quickly picked up on batteries being set for 24v it was modified for 12v.
I was expecting some discussion on why would you use a solar controller conneted to the towing vehicle to charge house batteries. The thoughts are a normal direct connection to house battery from the tow vehicle will generally see 14.4v delivered initally to the house batteries and then it may settle back to 13.8v, the friend who has a similar setup on his rig rational for using a solar controller is it can use the algorithm to match the battery chemistry.
But no it wont work because the wires from the ute are crossed at the AP (an actual unintentional mistake in the drawing)
Think about usage generally the charging sources are for a specific purpose, solar whilst stationary and the from the ute whilst travelling, even when you stop mid journey the VSR disconnects the tow vehicle and the solar take over.
-- Edited by Gundog on Tuesday 25th of October 2022 10:01:41 AM
-- Edited by Gundog on Tuesday 25th of October 2022 10:08:53 AM
Charge controllers sense the internal resistance of a battery and send their current to the battery terminals based on the resistance of the battery. If the battery is at a low state of charge, the resistance will be low and the charge controller will charge in bulk mode (depending on the battery type).
If the resistance increases, the charging current will decrease because the battery is almost full.
If two or more charge controllers charge the same battery, the battery will be charged quicker. The multiple charge controllers will not compete with each other because they all sense the same internal resistance of the battery. If charge controller A puts in 100Watts, charge controller B will also put in 100Watts into the battery.
When you program your charge controller you can add the cutoff voltage in the software. That means if your battery reaches a pre-defined voltage, it will stop charging. You can tell charge controller A to charge to 12 volts and charge controller B to charge to 12.8 volts. This is not needed but is good to know because one charge controller might stop charging if it reaches that point, and you will be wondering why that is. Also, if the wires of charge controller A are a bit longer, it might enter float mode earlier than charge controller B because of the voltage drop (increased resistance).
If the charging current becomes too high, the internal resistance of the battery will change because of the heat generated. The charge controllers will then reduce their power input to the battery.
When a charge controller senses the internal resistance of the battery what is it actually measuring? I'm guessing the measurement would have to be either voltage, or perhaps rate of voltage rise/fall over time? which perhaps in turn is interpreted as 'resistance' in the battery?
I wasn't aware that resistance was a matter of significance in Lithiums though, I thought that they had ultra low resistance & that the main parameter to determine when 'full' was a very small change in cell voltage - unlike in LA batteries where 'full' is determined by length of time held at a constant charge voltage. (with acceptance of charge dwindling as resistance increases).
I'm really just thinking aloud as Lithiums are beasts I have had no direct experience with. If it were me I would prefer to have all sources coming through the same controller if for no other reason than to be able to more easily monitor & understand what was going on, but you sound confident about what you want to do so give it a burl.
One thing that is often overlooked is different types of solar panels should not be mixed in the same string.
Its also better to have small strings attached to their own contollers.
For example origionally you had a set of folding portable panels say 100w with it own solar controller later you mounted 2x100w monocrystal panels and then added 2x120w polycrytal panels for best results each string will perform better with its own solar controller.