question

m1kkel avatar image

Battery needed?

Hi

I am about to install a mp-II 5000/48 and a Smart inverter RS 450/100.

I was wondering if a battery is needed before the system will work?

The system is grid parallel

I Will wire the 48v terminals to each other, until battery and busbar arrive.


Multiplus-IIbattery
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2 Answers
Alexandra avatar image
Alexandra answered ·

@m1kkel

No dont do it... Battery is the main reference for the system. Falls under crazy shed guy experiment and oops I voided my warranty.

There will be damage to components and unexpected behaviours.

https://community.victronenergy.com/questions/25592/multiplus-operation-with-a-battery.html

And are the two going to share the one bank? Also not a recommendation. They should each have their own banks if the are both running ac loads.

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I wasent aware that they are powered from the battery source. Since it’s a grid parallel system, i thought the multiplus would be powered from grid.

Ok I will wait until my battery is ready. But they will share the same battery. The rs450/100 is only a mppt controller and not a inverter, so I don’t see why they can’t share the same battery. ?

@m1kkel

Sorry you called it an inverter RS so had my wires crossed no pun intended- yes they can be connected to the same bus bar. And yes the battery is used for reference even in an mppt.

Thanks!

wkirby avatar image
wkirby answered ·

The MultiPlus is not a grid inverter, it is a battery inverter. A battery must be present for it to work correctly. The battery provides a stable Voltage reference for it to work. The Voltage from charger is not predictable, depending upon PV power available at any given random time.

Think about removing the battery from your vehicle and just using a charger in its place, you wouldn't expect things to go very well?

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Interestingly I have one of these mppts along with. 250/60 and a 150/100

if the circuit breaker to the battery trips the 450/100 seems to continue supplying the loads in the house whereas the other 2 shut down

maybe I have a problem then ?

@Chapelier

It was never said that it does not work only that possible damage that can occur. We are talking dc power and huge amps.

Just because nothing bad has happened so far, does not mean it is safe to do or can be recommended.

O.k fair enough but how do I switch it off in the case of the breaker to the battery tripping ?

You should have a way to disconnect the panels.

Change the dc breaker on the battery to a fused system rather than a trip system. I am not a fan of breakers on the battery side, seen too many good systems killed by them. Usually it is undersized (hence annoying tripping during normal operation) or have the wrong trip curve.. completely wrong like an AC rated one.

There are many on the market, but these are the ones we use.

Or we just use victrons mega fuses on the battery side.

Mmmm I use a 400amp nsx400dc Schneider breaker . Haven’t had any nuisance trips. I do also have the battery connected through a 300amp mega fuse on the lynx distributor but I need the circuit breaker as my bms will trip it on a high or low voltage cell . It’s never had to trip (except when I tested) as the 96 bmw cells stay within about 20mv and the Victron cuts of charge and discharge way before my set point for shutting the system down .

I am seeing some oddities since adding the rs 450/100

In VRM the numbers don’t add up to the mppt’s . I prob need to read through the manuals again and check all my settings

Maybe I’ll tidy up my wiring first though


c5c89aa5-7c2d-4d38-a539-247614ff7760.jpeg

Yes that’s one fair mess you have there