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Need help understanding my solar set up !

missoo

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Dec 1, 2020
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73
Hi guys,

I designed my solar system with someone's help.

All my equipment (Epever MPPT, Battery protect, inverter and charger) are connected together on busbars.
I am not using the Epever load outputs.

I installed a switch on my LifePO4 BMS and I noticed that while the BMS switch was off, the lights in my RV (and probably all other equipments) were still powered. I believe my solar panel are powering my lights (because disconnecting the solar panel, the switch is working normally).

Would you be able to explain me how my solar panels and Epever charge controller are able to power my equipment ? I thought this was not the purpose of a charge controller, I didn't even know they could do that (if we are not using the load output)....

Thanks for your help.

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The charge controller needs battery power to first boot up, then the imbedded software in the controller takes the raw solar voltage and transforms it down to the correct charging voltage. What can and has happened is that the battery can get suddenly disconnected by accident, and the charge controller keeps the system running for a while because it is already supplying power at the correct voltage.

Your wiring diagram appears too complex, and it doesn't help that it is not in English. Frigo means "refrigerator"? Convertisseur means "inverter"?

A well designed system would have breakers positioned between each component that would allow you to isolate each individual component.
 
My theory is that your BMS switch is turning off the BMS. However, your battery bank is still active and powering your system, even with the bms off.
 
You installed a switch which doesn't belong there to turn the BMS off and on. When you turn off that switch, all sorts of unpredictable things happen. Turn it back on and leave it on - Better yet, remove it so somebody else can't turn it off accidently

Don
 
@MichaelK So you believe that if I left longer the BMS off, after a while the electricity on my RV would have turned off ?
Sorry for the french diagram :/ I didn't take the time to translate it ... Indeed "frigo" is refrigerator and "convertisseur" is inverter.
Are breakers and switch the same thing ?
Because I have a switch for my charger, a switch for my inverter. It is just missing a switch (or breaker if it's different) for my charge controller...

@MasnPip the BMS switch is not turning off the BMS. It is only disabling discharge of the battery. However the battery can still be charged. I don't know why @Alphacarina you say that it doesn't belong there....
 
doesn't help that it is not in English
Does not worry me.

Some points regarding the circuit.

The Victron battery protect should not be connected to inverters, the battery protect will be damaged. Thus the inverter needs connecting to the positive buss bar via a fuse/breaker.


The cables and circuits immediately following the positive buss bar need over current protection, either fuses or breakers of suitable value.

You are correct in that if you have solar input there will be a charge to the battery and thus a voltage that will power lighting.

You dont necessarily need to isolate each part of the system with a breaker. On European RV installs its common to use fuses for over current protection, where as in the US using breakers is more common, the breakers have a manual switch option, this provide over current protection and for maintenance/commissioning allows isolation.
Are breakers and switch the same thing ?
A breaker primary use is to provide over current protection, it can be manually tripped to give a 'switch' action.

The circuit shows a change over switch for shore and inverter ac power. Make sure you fully understand the implications of this. A safer option is to have dedicated outlet sockets for shore AC and separate outlet sockets for the inverter AC, and omit the change over switch.

To avoid discharging the battery too far the Victron battery protect will shut off camper loads like lighting. By using the external remote outputs you could disable the two inverters.

Using the fridge thermostat to control the inverter powering the AC fridge may work. However some fridge control and starting systems are complex and may not allow this technique, thus needing the inverter active continually.

Mike
 
@MasnPip the BMS switch is not turning off the BMS. It is only disabling discharge of the battery. However the battery can still be charged. I don't know why @Alphacarina you say that it doesn't belong there....
Because I thought it was doing what he said he installed it there for - To turn off the BMS. Why would anyone want to do that?

Don
 
Hi @mikefitz ,

Thanks so much for your explanations.
I am glad you understand my french diagram :)

If the battery protect should not be connected to inverts, would you recommand me to connect the fridge inverter directly to the bus bas with a fuse on the positive ? Do you know what it would destroy the battery protect if I keep it like that ?

There is a french company selling Victron products, that recommands to put only one mega fuse (and not one fuse on each cable). However the diagram is much more simple that mine. Why they wouldn't recommand to add a fuse on the charger/inverter line ?

1624916146406.png

"The circuit shows a change over switch for shore and inverter ac power. Make sure you fully understand the implications of this."
What do you mean by "make sure your fully understand the implications of this ?
Everything is already installed and tested, it works. I hope I won't burn in my RV...

"By using the external remote outputs you could disable the two inverters."
You mean manually ? What would I disable them ? In case I don't have enough solar energy ?

"Using the fridge thermostat to control the inverter powering the AC fridge may work."
Fortunately it works because I have also tested it :)
 
would you recommend me to connect the fridge inverter directly to the bus bas with a fuse on the positive
ye.
Do you know what it would destroy the battery protect if I keep it like that ?

The battery protect is designed to be installed between the battery and consumers, things like lights, water pumps, phone chargers, 12v fans and similar 'camper' 12v items. It is unsuitable for connecting to inverters as the Victron report explains, due to the surge current damaging the semiconductors in the protect unit.
Why they wouldn't recommend to add a fuse on the charger/inverter line ?
Because they are not engineers and dont care if your RV burns down.

All cables have a maximum rated current that depends on cable size, the type of insulation used and the way its installed. Typical cables in the high current area around the battery and their maximum allowable current for quality automotive cable will be, 6mm2--50A, 10mm2--70A, 16mm2--110A, 25mm2--170A, 35mm2--240A.
Each cable from the battery or main buss bar and whatever is connected to the end of the cable needs over current protection.
Taking the Victron diagram you posted as an example.

Assume the MPPT controller is a 100/30, so the maximum current to the battery is 30 amps, all the MPPT internal circuits are designed for 30 A. Typically one would wire it to the battery with 10mm2 cable or even 6mm2 if the distance is short. If a fault occurs somewhere along the cable or inside the Victron controller that causes excess current to flow beyond the safe rating of the cable, ( and wires/circuits inside the unit), there is a possibility of fire. To prevent excess current along the path to the controller and its insides, a fuse or circuit breaker is needed. Since the maximum working current is 30A, the use of a 40A fuse or breaker would be suitable at the battery end of the cable.
Its clear that a 200A fuse would not be suitable.

For ease of demonstration and producing system diagrams, often not all fuses or breakers needed for a safe system are omitted for clarity.
What do you mean by "make sure your fully understand the implications of this ?
I do not know the regulations for AC systems in your country ( France?) but in the UK there is a requirement for a permanently installed inverter to have a neutral to earth bond within the inverter and that a 'earth leakage' protection device, a RCD, be installed to prevent electrocution. Also the protective earth wire needs to have a connection to the van metal.

By using the external remote outputs you could disable the two inverters.
I did not explain too well. Since you fitted a Smart Protect I assumed you intended this to shut down consumers when the battery falls to a low value.
You may wish to shut down the inverters if the battery gets too low. The Smart protect can detect a low voltage. It has a relay that switches at the set low volts. This could be integrated with the remote disable of the two inverters and shut them down automatically. (this may need two additional small relays in the remote disable circuits).

Mike
 
Hi and sorry for the delay,

I am going to add fuses to my circuit and I was wondering if this type of fuse was correct.
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Also here are the fuses I think I will add. Are they right ?

Solar panels - MPPT 150/40 : fuse 20 A (2 solar panels 215 W in parallel with 6 mm2 cable)
MPPT - battery : fuse 40 A (10 mm2 cable)
battery - victron inverter 400 w : fuse 75A (10 mm2 cable)
battery - edecoa inverter 1000 w (for fridge only) : fuse 30A . Because the frige consumption is 109kwh/year = 298 w/day (10 mm2 cable)
battery - IP22 charger : fuse 30A (10 mm2 cable)

One more question, as the switch of my BMS is not shuting off the power in my circuit, should I add a breaker between MPPT and solar panels ?
What is usually done to turn off everything in the van ?

Thanks for your help.
 
I was wondering if this type of fuse was correct.
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No! Those are cheap audio fuses. They have a high failure rate (as demonstrated repeatedly here), get very warm and often trip well below their rated value.

Bussman and Blue Sea Systems are highly regarded. Watch out for look alike clones. There are other quality brands too but these 2 get mentioned repeatedly here.




Yea, they are a lot more expensive, sorry. But this is necessary money well spent on safety.
 
What about these ones ?

As Mike said before, we mainly use fuses in Europe instead of breakers. I suppose there are good fuses too.

fuse.JPG
 
DIY solar 12.jpg
Fuse F1 to F4 midi fuses, F5 mega fuse, F6 MRBF

To get a more simple layout the fuses and positive buss bar can be combined.

midi mega fuse holder.jpg

Issues with the circuit.

The 1000 watt inverter will take a very high current to start up the fridge under certain conditions. Thus it needs to be connected with heavy duty cables and fused for full output.

Its not possible to connect the Victron Battery Protect to the inverters, as doing this will destroy the Battery Protect.

To have a degree of control over the inverters you can use the BMV relay and the Battery Protect relay to disable the inverters using their remote inputs, connect in series with the existing remote enable control circuit.

Mike
 
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Thank you !

Is it correct to buy the fuse box and mega/midi fuses on aliexpress ? They look like the same than on Amazon.
As I have already a positive bus bar, if I choose the "combined version", it means that I wouldn't need my positive bus bar anymore ?

For now, I had less than 1 meter cable for my fridge inverter. According to the maths, I believe that 10 mm2 could handle the 1000w (83A). But adding the fuse, if I get more than 100 cm lenght, I'll switch to 16 mm2.

For my battery, I only have 50 cm lenght cable and I calculated that I wouldn't consume more than 120Ah. Is it correct to keep my 120A mega fuse ?

Ok I wont connect my battery protect to the inverter. I don't have the BMV but this one. I am not sure I understand what to do with the relay and remote inputs. Do you have any diagram ?
61bU8Ch88TL._AC_SL1200_.jpg


Update: I realised I am already using the inverter remote on my "comutator". I believe I won't be able to use it on the battery protect relay. However, the BMS is here to protect my battery from deep discharge no ? What would be the advantage of using the BMV relay and battery protect relay ?
61OrJUfDqML._AC_SL1001_.jpg


Could I add a circuit breaker between solar panels and MPPT to cut the current off ?
 
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buy the fuse box and mega/midi fuses
Ebay and Amazon could be a source. These are standard automotive fuses so should be available from an auto electrical specialist. I suggest buying from a company in Europe rather than aliexpress ( assuming you are based in France)
"combined version", it means that I wouldn't need my positive bus bar anymore ?
Yes, the fuse distribution holder effectively combines the buss bar and fuse holders, the style in the picture having one mega fuse position and 4 midi fuse.
Is it correct to keep my 120A mega fuse ?
This is the 'master' fuse fitted as close as practical to the battery positive post.
Any cable regardless of length should be fused to protect the cable from currents higher than the rated maximum.
The absolute maximum allowed currents are, 10mm2, 70A, 16mm2 110A, 25mm2 170A.

The battery you are using is a lithium battery, should there be a fault somewhere in the circuit, ( a accidental connection between the positive and negative) and the BMS were to fail to protect, (open the output path) then the battery will deliver a very high current ( 1000s of amps) , this will melt cable insulation and cause a fire.

The automotive mega fuse is only rated for interrupting 2000 amps

in order of current interrupt performance using quality branded fuses with a 12v battery,
mega fuse, 2000 amps
ANL fuse , 6000 amps
MRBF fuse, 10,000 amps
Class T fuse, 20,000 amps

The Blue sea MRBF fuse and fuse holder, whilst not offering the highest protection of the Class T fuse, is acceptable in my view.
. I don't have the BMV but this one.
Component part and diagram changes make it difficult to offer advice. The Aili may give passable performance but does not have the programmable relay that the BMV series have.

Because you do not have the inverters connected to the Victron battery protect, any low voltage protection will have to be carried out by the battery BMS or the low voltage shutdown in the inverters.
This should be enough to protect the battery from low voltage.

If you need additional protection against low voltage for the fridge inverter, then the relay contacts in the Victron Battery Protect, could be added in series with the enable control to the inverter.

What BMS are you using? Is It user programmable?
Can the inverter low voltage shutdown levels be user programmed. if not what are they set at?

It would seem you have enough solar and battery capacity to power the fridge for long periods and its unlikely, since you have battery monitoring with the AiLi and perhaps a smart BMS, you will not allow the battery volts to fall too low.
In the unlikely event the battery becomes too discharged, the BMS will shutdown.

as the switch of my BMS is not shuting off the power in my circuit, should I add a breaker between MPPT and solar panels ?
What is usually done to turn off everything in the van ?
Fitting a switch between the panels and controller rated for the input DC current and voltage would disconnect the panels.
To completely isolate the system from the battery you could add a battery isolation switch between the 'master fuse' at the battery and the rest of the circuit.


Mike
 
Thank you so much for helping me understand how it works. I am really grateful.

To calculate the wire section I use the formula :
wire section = I * 2 L * 0,021 / 0,36 = 120 * 2*0,5 * 0,021 /0,36 = 7 mm2

Which means that for 50 cm lenght and 120A I can use a 7 mm2 cable for my battery . Am I wrong with my calculation ? I am a bit confused with your affirmation :
10mm2, 70A

The Blue sea MRBF fuse and fuse holder, whilst not offering the highest protection of the Class T fuse, is acceptable in my view.
Allright I will invest some money for safety.


I am using the overkillsolar BMS and I use recommanded settings.

I just discovered that I can programm the Victron inverter 500 VA but I need to buy the VE Direct USB cable that I don't have.

About the Edecoa inverter, I don't think I can programm it but in the manual I can see :
DC low voltage protection : 10 V +/- 0,5 V

Fitting a switch between the panels and controller rated for the input DC current and voltage would disconnect the panels.
To completely isolate the system from the battery you could add a battery isolation switch between the 'master fuse' at the battery and the rest of the circuit.
I also have the BMS switch. Isn't it enough as it unallows the battery to get discharged ?

Is it important to be able to disconnect the panels ? Because I saw that energy was still circulating in my circuit while th BMS was shut off.


Also... I bought the Epever 150/40 MPPT as Will recommanded it for quality.
However I only have for now 2 solar panels 215 W in parallel. I was thinking maybe adding a third later. Was it totally over dimensionned ?
I am wondering if I made a bad decision here. Maybe the second miskate was building a 280Ah LifePo4 as I am not sure I will be able to fully charge it....

Therefore I am considerating changing my MPPT for a duoracer 100/30, in order to connect my engine battery at the same time. But it would be some trouble as everything is installed and the screen controler is not the same as mine.

Any thoughts about it would be really helpful.
 
50 cm lenght and 120A I can use a 7 mm2 cable for my battery .
The cable manufacturers state the maximum current the cables can tolerate. The numbers I gave in the last post are for thin wall multi strand insulated cabled commonly used in the UK for automotive applications. These are the maximum currents , for cables at higher temperature , or in looms with other cables, or are under insulation material, the rating is reduced. I am not familiar with your calculation method, however I know a 7mm2 cable will not carry 120 amps without getting very hot.

overkillsolar BMS and I use recommanded settings
That is a good BMS, I use the same type. If you are worried about low voltage disconnect you could increase the default values. I use 12.8 volts for the low disconnect.

I also have the BMS switch. Isn't it enough as it unallows the battery to get discharged ?


The switch used on the Overkill BMD only prevents discharge current through the BMS, it does not completely disconnect the battery from external circuits.
Is it important to be able to disconnect the panels ? Because I saw that energy was still circulating in my circuit while th BMS was shut off.
The switch only stops current flowing out of the battery thorough the BMS. This is what Steve (who sells the BMS) said,
The idle power draw of the 4s BMS is less than 5ma. The discharge shutoff switch prevents system loads from discharging the battery. Unplugging the balance wires will take the standby power to zero but the cells still have a self discharge rate.
If you disconnect the system completely with a mechanical switch after the battery the solar controller will shut down. If you disconnect the solar panel from the controller no current will be delivered to the circuit.
. I bought the Epever 150/40 MPPT as Will recommanded it for quality.
However I only have for now 2 solar panels 215 W in parallel. I was thinking maybe adding a third later. Was it totally over dimensionned ?

Your panels are OK is series or parallel connection to that controller. EPever allow the controller to be 'over panelled' so adding a 3rd panel will not be a problem. In real life you never get full output from the solar panel. With three panels you may loose a small amount of solar yield around midday, (as the controller limits the maximum to 40 amps), but the higher yield early and late in the day will be an advantage.
I think you will find even with the two 215 watt you will have enough power for your system.
Maybe the second miskate was building a 280Ah LifePo4 as I am not sure I will be able to fully charge it....
Do not worry. It does not matter if a lithium battery is fully charged, in fact the battery will have a longer life if not full charged. With your 430 watts of solar and modest electric requirement there will, most of the time, be enough solar power. In winter or poor weather, alternative charging may be an advantage.
Rather than change the Epever solar controller, add a engine battery to house battery charger, a Battery to Battery charger.
This is added to the system and both the Epever controller and the additional B to B controller will work together.
Units to consider are , the Victron Orion tr Smart 12 12 30, the Sterling BB 12 30 and the Votronics VCC 12 12 30.

Most vehicles can supply the alternator power for the B to B chargers. What vehicle make and age of is your van?

Mike
 
Hi Mike,

The numbers I gave in the last post are for thin wall multi strand insulated cabled commonly used in the UK for automotive applications.
Allright. We use cables which are called "H07V-K". They are probably the same.
6193101302501cable-souple-h07v-k-10mm-rouge-600x600.jpg

About the formula, it's commonly said that the shortest the cable is, the more it can handle current. However, just in case I will change my cables for 25mm2. Safety is important :)

If you disconnect the system completely with a mechanical switch after the battery the solar controller will shut down. If you disconnect the solar panel from the controller no current will be delivered to the circuit.
In France, I have read several times that we should first connect the MPPT to the battery, and only then connect the solar panels to the MPPT or it will dammage the MPPT.
If I have a switch after the battery, the MPPT is going to be only connected to the solar panels while the switch is off. Isn't it going to be a problem ? I am very confused with that.

Do not worry. It does not matter if a lithium battery is fully charged, in fact the battery will have a longer life if not full charged. With your 430 watts of solar and modest electric requirement there will, most of the time, be enough solar power. In winter or poor weather, alternative charging may be an advantage.
Thanks. I totally am reassured !


What vehicle make and age of is your van?
I have a Renault Master from 2018. "Euro 6" I don't know if they are called the same in english.

I have thought of using a Orion Smart. However, I found it a bit expensive because it's only to charge my engine battery and it can work in only one direction. I mean I won't be able to charge my house battery while driving. I am not sure if it's worth it.

I am still considerating using a battery master and the one that it's mainly use in France as I can buy it in a shop in my town. Unless you can explain me how to build my own circuit :/
dispositivo-csb2-codice-10191-500x496.jpg


However, I have read that it could totally discharge the house battery if no solar panels are connected (I believe you should know why but I can't really explain it in english). I guess the solution would be to disconect it if the van is parked in a garage for a long time.
 
If I have a switch after the battery, the MPPT is going to be only connected to the solar panels while the switch is off. Isn't it going to be a problem ? I am very confused with that.
That may be the case for some types, but most MPPT controllers survive a disconnection of the battery. You could add a similar switch to the solar panel to controller connection and isolate the panels before the battery disconnect.
Renault Master from 2018. "Euro 6" I don't know if they are called the same in english.
I think there is a small misunderstanding.
I thought you wanted to charge the lithium battery from the engine. Renault allow a maximum of just over 40 amps to be taken from the alternator to power auxiliary circuits. Euro 6 results is a low average voltage at the engine battery, the battery to battery charger will boost this to charge the house battery.
The Victron Orion is used to charge the house battery from the engine battery when the engine is running. This will put 30 amps into the lithium battery when driving.

If all you need is to provide a small current from the lithium battery to the engine battery then the CBE CSB2 will do this. You are correct, if the engine battery has always a small loss of energy the CBE unit will take power from the lithium battery to make up for the loss.
If the camping car is in a garage with no sun for a long time then the lithium battery could be discharged also.
The BMS would prevent damage to the lithium battery.
If the car is in the garage connect the AC charger if you have AC power available.
The CSB2 could be disconnected from the engine battery, but the engine battery would loose power over some time and you would not be able to start the car. ( unless you disconnect the engine battery).


We use cables which are called "H07V-K". They are probably the same.
they are not the same. The H07V-K is for stationary applications, the some company offers FLRY-B for automotive applications that are more robust, operate at higher temperatures, and have higher current rating.
H07V-K
H07V-K.jpg


FLRY-B

FLRY-B.jpg
Mike
 
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