Victron MPPT 100/50 with RV Converter Charger same circuit ?

[Spleeft]

Just a quick noob question. When I connect the MPPT to the battery along with the normal Converter/ Charger that's standard on RVs do they both "understand" when to not charge? For instance, when we are camping with shore power and plugged in ( or the on board 4K Onan Genny is running ) and its a blazing sunny day, does the MPPT see the RV charger and safely shut down?

 

[cass3825]

They are both charging based on the voltage of the house battery bank, so yes, they should play nice with each other.

 

[Defenestrator]

It's always safe, but not always optimal. That is, the battery system is one big DC bus and power can be going in and out via multiple devices with no problems, but it's possible that one device will see the charging voltage from another and kick into float instead of bulk mode sooner than it should. Not a huge deal in most cases, but something to be aware of.

 

[cass3825]

It's always safe, but not always optimal. That is, the battery system is one big DC bus and power can be going in and out via multiple devices with no problems, but it's possible that one device will see the charging voltage from another and kick into float instead of bulk mode sooner than it should. Not a huge deal in most cases, but something to be aware of.

Excellent point. Yes, it’ll work, but definitely not ideal.

 

[Spleeft]

Excellent point. Yes, it’ll work, but definitely not ideal.

It's always safe, but not always optimal. That is, the battery system is one big DC bus and power can be going in and out via multiple devices with no problems, but it's possible that one device will see the charging voltage from another and kick into float instead of bulk mode sooner than it should. Not a huge deal in most cases, but something to be aware of.

What options do I have to make it ,more optimal ? And thnx for the replies !

 

[Defenestrator]

I wouldn't worry too much about it unless you actually see the converter kicking into float mode immediately instead of bulk. If the solar controller goes into float when you're plugged in, it's technically a "waste" but probably won't make any practical difference. It'll generally only make a difference on the margins anyways - that is, if the batteries aren't close to fully-charged they'll drag the system voltage down low enough that everything will be in bulk mode anyways.

 

[tictag]

does the MPPT see the RV charger and safely shut down?

Yes, an MPPT monitors the battery voltage and will will shut down when required. It doesn't matter whether this battery voltage is high because it's being charged elsewhere.

The only potential complication is if you consider a discharged battery on a bright sunny day then both the RV's charger and MPPT will be attempting to charge the battery - this might end up charging the battery beyond its charging current limit. Probably not a problem for Lithium-ion with typical 1C charge rates but might be for lead-acid which generally shouldn't be charged at more than C/10 Amps (e.g. 100Ah battery = 10A maximum charge current). Charging a lead-acid at too high a charge can lead to explosive failure.

Some MPPTs can integrate with a current-shunt energy monitor and lower charge rates in such cases e.g. Victron devices.

 

[Defenestrator]

Good point about the overly-fast charging. Not a problem for LFP or large banks, but it might be for a small lead-acid bank. For short periods every now and then, I imagine C/3 or so wouldn't hurt too much as long as it's <80% charged, and above that the voltage will probably be high enough that at least one will kick down to absorb mode.

 

[Pierre]

a Possible solution would be to have a selector switch to select between ‘Solar’ and ‘Mains’ . When at an RV park with a non- metered mains supply , I would select that source and ‘conserve’ my solar system. The solar charge controller should however always be connected to the batteries as to supply a reference voltage. Rather disconnect the PV panels from the solar charge controller in the selection process. Works for me and no overcharging as a result.

 

[ian brooks]

I bought an automatic transfer switch which I plan on installing s soon as I get all my batteries set up.Will has a great video with step by step instructions on the subject .I think that will solve that potential problem for me.

 

[tictag]

I think that will solve that potential problem for me.

A transfer switch only deals with AC i.e. has no effect on DC systems.


Tbh, as @pierre says, it's generally a good practice to have a PV isolation switch so that you can carry out maintenance on your system without a potentially high voltage supply being present. Same goes for your battery.

Also, if you have Lithium-ion batteries, this really won't be a problem; a 100AH LiFePO4 battery can happily be charged at 100A. I doubt your RV and SCC together will be kicking out that much.

 

[Spleeft]

I like that idea for the PV shut off switch. This switch would go on the positive wire, correct?

 

[tictag]

 

[ian brooks]

A transfer switch only deals with AC i.e. has no effect on DC systems.


Tbh, as @pierre says, it's generally a good practice to have a PV isolation switch so that you can carry out maintenance on your system without a potentially high voltage supply being present. Same goes for your battery.

Also, if you have Lithium-ion batteries, this really won't be a problem; a 100AH LiFePO4 battery can happily be charged at 100A. I doubt your RV and SCC together will be kicking out that much.

I guess I should of clarified that I will be using an inverter which as I understand it will energize the converter for the dc side when not on shore power ,I'm hoping at least .Noob here trying to figure out the puzzle.

 

[jbeletti]

@Spleeft - what inverter are you using? Reason I ask is that some inverters are inverter / chargers. With those, you'd likely not need the DC converter.

 

[tictag]

I guess I should of clarified that I will be using an inverter which as I understand it will energize the converter for the dc side when not on shore power ,I'm hoping at least

Yes, that is correct. It will allow you to switch between inverter power and shore power. What I mean to say is that this will not fix the problem we were discussing (that both the RV's charger and SCC combined might exceed charging limits) - whether on shore or inverter power, the MPPT and RV's charger will still be charging the battery together.

As mentioned, this is probably not a problem if you have Lithium-ion battery but might be a problem if you have lead-acid. If it is a problem, the easiest way to fix it would be to isolate your PV array, which, as mentioned, is a good idea anyway.

 

[Spleeft]

@Spleeft - what inverter are you using? Reason I ask is that some inverters are inverter / chargers. With those, you'd likely not need the DC converter.

As TicTag said in post #16, I'm using a standard RV Charger/Converter ( PD 4655L Wildkat PD 4655L MBA WildKat 55 Amp that I replaced the original WFCO 8955 with ) and adding a solar system to charge batteries. ( 2 DC220-6 Fullriver 6 Volt 220 AH AGMs in series )