Questions about: galvanic isolation, inverter/charger, bms and battery balancer

DIY
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1

Hello,
I have several questions (I suppose I can ask them at once):

  1. If I have installed “Quatro” inverter/charger on a boat do I still need a transformer/galvanic isolator? Doesn’t “Quatro” already galvanically isolated?

  2. Do I still need a bms with “Quatro” inverter/charger for LiFeP batteries? Or this inverter/charger has integrated bms in it?

  3. If I connect multiple LiFeP 24V batteries in parallel does bms control the whole pack of batteries and I still need battery balancer, or bms is sufficient to control state of charge of each battery?

Thank you.

2
  1. The Quattro is galvanically isolated between DC and AC. The AC input and output are directly connected so you still need galvanic protection on your boat. I use an isolation transformer as it gives more robust protection than a galvanic isolator.
  2. Yes, you still need a BMS.
  3. If the batteries are in parallel you do not need a balancer. If you use Victron Smart or NG batteries then you only need 1 BMS for the whole set of batteries. In parallel, make sure you use equal wire lengths and fuses etc. See the Vitrron book Wiring Unlimited.
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3

Hello, and thank you for an answer.

In case I use Victron “Quatro” Inverter/Charger but with third part batteries and BMS. Will this system correctly work without batteries balancer(s)?

Thank you.

4

You will have to consult with your battery supplier to answer this. Victron Quattro works with 3rd party batteries, some are properly integrated others not.

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5

Hello,
Thank you for an answer.

I have another question about “Quatro 24/8000/200-100/100”:

  • There is a limit to continuous output power equal to 8000VA (6400W) and 30A continuous current. But what about auxiliary output power limits? It’s marked it has 50A current limit. And does power envelope from auxiliary output sums with inverter output to 8000VA? Or they’re not?
    Thank you.
6

The auxiliary output is only turned on when there is ac connected to the input and is for non critical loads, such as water heaters that you do not want to operate when your are running on DC power without ac input.

When you have ac input available, the inverter can pass through up to 100A of ac, 100A x 230V = 23,000VA and the inverter can add 8,000VA to give 31,000VA total output. Of this, 11,500VA (50A x 230V) can go to the auxiliary output. Your output wiring needs to be capable of this.

7

Cool, I didn’t knew this property that it can add power in such a way.
So if I understand correctly: if I have input AC from grid and generator (this can sum up in total 200A?!) and then use my battery I can have on my main AC output (non auxiliary) 230*200 + 8000VA = 54kVA?

And I’ve seen in can charge up to 200A a battery? If I’ll have 40A in AC input this will give me:
230 * 40 / 28.4 = 323A => 200A (because it is limited to 200A)? (Here I take 28.4V a charging voltage of LiFePO battery. Not sure if it’s correct or I should take 24V?).

8

You can not have 100A in from grid PLUS 100A in from AC, only one AC input is active at a time. It switches to whichever input has voltage and if both inputs have voltage then it chooses AC input 1. SO the limit is as I said, 23kVA.

It should be 200A at the max charge voltage, but power limits may apply if the units gets warm and it derates to avoid overheating.

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