Inverter Multiplus 2 3000va battery bank too small

[teddysx3]

Hello everyone!

Have some question for you.

I'm building my solar system. The inverter I have purchased is a Multiplus 2 3000va 230V version. The battery bank at the moment I have a 100ah battery (planning to upgrade in the future) but for now I only have one. I see in the manual they recommend a 400ah battery bank. I'm assuming this is to account for the 2600w current draw that the inverter is capable, and the 5000w peak power current.

My question is, If I'm not going to use up all this watts from the inverter, let's say this 100ah battery has a C1 discharge rate, that's 1200w at 12v. If I'm not even going to use up these 1200w, would I be ok until I upgrade more batteries? I'm guessing this 400ah battery bank that is recommended in the manual is for the MAX rated current that the inverter can output, so the batteries can handle it. My cables are 0000 gauge, big cable's in order to handle this big current from the inverter.

But even if I go over 1200w, with a 100ah battery, wouldn't the BMS of the batter limit, or cut off?

Thanks guys!

 

[time2roll]

Yes the small battery will power the Victron up to the limit of the battery. Best to stay well under 1000 watts initially. While the battery BMS should cut power if needed I don't recommend this on a regular basis. Keep in mind 400ah is a minimum recommendation. Depending on loads and expected run time, the system could need a much larger capacity.

 

[teddysx3]

Yes the small battery will power the Victron up to the limit of the battery. Best to stay well under 1000 watts initially. While the battery BMS should cut power if needed I don't recommend this on a regular basis. Keep in mind 400ah is a minimum recommendation. Depending on loads and expected run time, the system could need a much larger capacity.

Yes, I agree and understand. The 400ah is a minimum recommendation. I plan to get to 300-400ah, but at the moment just have the 100ah to start.

I really don't think I need even 200-300ah, but I just wanted to make my self a super nice reliable system. I don't have AC, most of my appliances are 12v, maybe a coffee machine, hair dryer from time to time. So I hope I will be good with the 100ah is I don't exceed the 1000w limit.

I mean, that's the only concern were, that they recommend 400ah, because of the power of the inverter to put out 5000w peak right?

 

[time2roll]

I mean, that's the only concern were, that they recommend 400ah, because of the power of the inverter to put out 5000w peak right?

Probably derived from lead-acid where a small battery will suffer immediate voltage drop at high level draw and the inverter will shut down. Victron wants the equipment to work as designed to provide reliable service to the user and operate reliably as expected. The rating fits LFP much the same.

Also check the charge settings are compatible with the battery.

 

[rmaddy]

But even if I go over 1200w, with a 100ah battery, wouldn't the BMS of the batter limit, or cut off?

You should setup the MultiPlus to turn itself off at a voltage higher than what the battery's BMS cuts off. The BMS is meant as the last line of defense for the battery cells. Setup your equipment so the BMS's defenses are never actually needed.

One thing to consider while you only have 1 100Ah battery is to use a much smaller fuse to the inverter. Normally you would use a 400A fuse with your 4/0AWG wire for a 12V 3000W (really 3000VA) inverter. But since your battery can only handle a 100A discharge, put a 120A fuse, or even 100A fuse. Replacing a fuse when you try to push the battery too hard is cheaper than damaging the battery. Then again, the BMS should shutdown the battery before any battery damage occurs.

 

[teddysx3]

You should setup the MultiPlus to turn itself off at a voltage higher than what the battery's BMS cuts off. The BMS is meant as the last line of defense for the battery cells. Setup your equipment so the BMS's defenses are never actually needed.

One thing to consider while you only have 1 100Ah battery is to use a much smaller fuse to the inverter. Normally you would use a 400A fuse with your 4/0AWG wire for a 12V 3000W (really 3000VA) inverter. But since your battery can only handle a 100A discharge, put a 120A fuse, or even 100A fuse. Replacing a fuse when you try to push the battery too hard is cheaper than damaging the battery. Then again, the BMS should shutdown the battery before any battery damage occurs.

You are totally right!

I was going to use a 100ah ANL fuse, for the main fuse for the system, as my battery is 100ah, and when I upgrade, will bump up the ANL fuse respectively to the amp hours of the battery. 400a battery with a 400a ANL main fuse.

But on my Victron lynx, I also will need to install a 100 amp fuse, instead of the 400 amp mega fuse that is recommended by the manual. Thanks for the tip! I was going to neglect this, I had it in mind, but did not plan it.

Probably derived from lead-acid where a small battery will suffer immediate voltage drop at high level draw and the inverter will shut down. Victron wants the equipment to work as designed to provide reliable service to the user and operate reliably as expected. The rating fits LFP much the same.

Also check the charge settings are compatible with the battery.

Yes, the 120 amp charger will be way too much for the 100ah, I will need to dial it down a bit. The Renogy batteries can take .5C charge, but I think I will keep it on the safe side, and do .25C maybe, to long life the battery.

 

[Bud Martin]

Notes: That 3000VA inverter will have large capacitor bank which will cause large inrush current when hooking it up to the battery and it may trip the BMS, you should use pre-charge resistor to charge up the caps first. Every time you disconnect the inverter from battery for a long time, the caps will discharge so you will have to do pre-charge every time when you connect the inverter back up to the battery.
Search the tread about 'pre-charge resistor'