Dual sensing VSR with solar

[Cheet22]

Hi all,

I've scanned a million posts on here and elsewhere trying to find a definitive answer to my dilemma, with no success.

So I'm hoping someone here can explain/confirm my thinking

I have a 2010 mk7 LWB that has two factory batteries under drivers seat. I know front is aux and rear is starter

I have installed a new agm leisure battery in rear for "house".

I have 500w solar connected to this through a 40a mppt controller. It's not a dual battery controller, only single.

I have also just received a dual sensing vsr and about to fit, but i be started having concerns about the validity of adding this.

I plan to connect from van front aux battery to vsr, then vsr to the new agm. I also plan to install a breaker near vsr so i can disable vsr if i want

My theory is that when running, vsr still detect increased voltage from van alternator, making a connection to rear agm battery and thus charge that battery.

In reverse, as i read online, with engine off but solar on to the agm battery, again the vsr should engage and the solar charge the van aux battery too. I can use the breaker though if required to focus all solar charge on agm battery.

This is my ideal as it's means van aux benefits from solar when van laid up when not in use.

But my concern now, is that i can't seem to get a definitive answer to is what really happens when engine runs given that solar is also pushing a charge? Engine and solar would both be pushing a charge as such, so what happens? Is that ok?

My theory is that the mppt controller will sense power going into agm leisure battery via engine running and reduce/stop solar charge? Does that seem correct?

Just want to be sure it won't blow up or overcharge?

[workbox]

Once your AGM leisure battery fully charged MMPT will go into float. (stop charging)
If your vehicle comes with smart alternator then vsr / split charger is no good to you.
Even if you have got conventional (old type) alternator, split charger is not ideal I would opt for B2B charger instead.

[Airthies]

Once your AGM leisure battery fully charged MMPT will go into float. (stop charging)
If your vehicle comes with smart alternator then vsr / split charger is no good to you.
Even if you have got conventional (old type) alternator, split charger is not ideal I would opt for B2B charger instead.

B2B charger won't allow bidirectional charging as a dual sensing VSR will, as basically they're just a big relay.

Sent from my A55ho11 using Crapatalk

[workbox]

Once your AGM leisure battery fully charged MMPT will go into float. (stop charging)
If your vehicle comes with smart alternator then vsr / split charger is no good to you.
Even if you have got conventional (old type) alternator, split charger is not ideal I would opt for B2B charger instead.

B2B charger won't allow bidirectional charging as a dual sensing VSR will, as basically they're just a big relay.

Sent from my A55ho11 using Crapatalk

You right, I thought question was "Engine and solar would both be pushing a charge as such, so what happens? Is that ok?"

[Rob62]

Have you tried talking to the manufacturer? They know how their systems work and how they work with various vehicle types..

[imageoven]

B2B charger won't allow bidirectional charging

You can get B2B chargers with built in solar controllers which will do the job
https://www.12voltplanet.co.uk/votronic ... solar.html

[bortaf]

I use this below from renergy for the exact same config as you except i dont have a smart alt
https://www.renogy.com/dcc50s-12v-50a-d ... with-mppt/
When the house battery is full it charges the "starter" battery or in yours and my case it charges the van Aux battery.
A far cheaper option is to just use what you have and add a £30 dash solar pannel for the Aux battery, i used this system for over a year whilst building the camper and it worked fine, i have 4 of these in differant vehical i own
https://www.amazon.co.uk/gp/product/B07 ... UTF8&psc=1

One thing to be aware of with the DCC50s is if solar is low and you start the engine the B2B is limited to 25A as long as any solar is coming in, switch off the solar and it will give you 40A+ from the B2B, no biggy but if your only getting 2A of solar and you run the engine the max you'll be charging the house battery at is 27A, it's a quirk of the unit

[ste550]

Hiya , just ordered a Renology 50 amp with solar £240. Should do the job, I want to get my seats back in