Growatt 3k 24 volt and 12btu minisplit

[TheeBigGuy]

Will this power a 12btu 110 volt minisplit... Does it have enough power to start it.... And if I want to run the heater for 4 hours at night app 1,000 watts how many batteries do I need.. If it doesn't have enough to start it can I just use capacitors to get enough amps for start up? Thanks

 

[RCinFLA]

If mini-split is inverter-air cond likely yes. Most mini-splits are inverter type air cond and have very little additional starting current surge.

Just make sure you have large enough battery and battery cable gauge. Air cond will likely be about 12 amps at 120v. Will draw about 65 amps of battery current on 24v system.

If LiFePO4 would not plan for more then 70% capacity useage. If lead-acid don't plan to use for then 50% capacity and be aware of real capacity at the current you are drawing. Most lead-acid capacity is stated at 5% rated AH in amps (5 amps for 100 AH). At 20% rated AH in current amps their true capacity drops to about 65% of rated AH's.

 

[TheeBigGuy]

If mini-split is inverter-air cond likely yes. Most mini-splits are inverter type air cond and have very little additional starting current surge.

Just make sure you have large enough battery and battery cable gauge. Air cond will likely be about 12 amps at 120v. Will draw about 65 amps of battery current on 24v system.

If LiFePO4 would not plan for more then 70% capacity useage. If lead-acid don't plan to use for then 50% capacity and be aware of real capacity at the current you are drawing. Most lead-acid capacity is stated at 5% rated AH in amps (5 amps for 100 AH). At 20% rated AH in current amps their true capacity drops to about 65% of rated AH's.

Great information thank you...You said a lead acid 100ah battery is 5 amps so if 70% on a lifePO4 thats 7amps...In order to cover the 65amps thats 10 LifePO4 100ah batteries or basically $10,000.00....Which equates to years and years before a break even...It never works out in my mind why switch to solar...Is my thinking correct?

 

[RCinFLA]

No, just used 100 AH as example because it matches % easily.

65 amps for 4 hours is 260 AH consumed, assuming air conditioner runs continuously for the four hours of time. Duty cycle will depend on room size and climate temp.

Taking 260 AH. For LiFePO4 would need 260AH/70% = 371 AH rated battery capacity. For LiFePO4, 100 AH, like BattleBorn, need total of eight batteries. Two in series gives 24v 100 AH, times four for 400 AH total capacity, total of eight 12v, 100 AH batteries. About $8,000 for BattleBorn.

If individual LiFePO4 cells, it takes eight in series to make a 24v system. So if using 280 AH cells would need 8 series by two strings in parallel, 16 total individual 280 AH cells giving 560 AH of total capacity.

Until you get some experience with care and feeding of LiFePO4 batteries I would not recommend building with individual cells as if you screw up it can be a very expensive learning exercise.

 

[Dhopewell]

The cost of batteries can much lower than described above. First a 70% duty cycle is extremely low for lifepo. Some very sophisticated users on this forum go to or beyond 90% routinely, and testing on this chemistry has demonstrated that allows for rated cycles. There’s nothing wrong with buying more batteries than you need but the deep discharge qualities of lifepo is one of their attractions.

I won’t argue that or how much you need to know to build your own, but even as stated the price differentials leave a lot of room for learning as you go. At current pricing for 280ah cells the system above a 24v 560ah, costs between 2500-3000. Here are the costs I’m seeing:

16 280ah cells - shop a little prices vary $2025
Daly 250A smart BMS and accessories. $250.
1/4” x 72” copper bar $60
10 ft 2/0 wire and terminals. $100
Fuses and fuse blocks. $100. = 2600

If you are handy you spend a month learning and build this battery. You’ll save 5-7k.

 

[gnubie]

Battleborn states that their batteries can be discharged down to flat (BMS cuts off) and still receive 3000 cycles.

 

[apctjb]

.It never works out in my mind why switch to solar...Is my thinking correct?

The vast majority of people that go solar are grid connect and don't have batteries. Depending on where you live you can get solar installed for no money down and instant savings on your electric bill...

 

[Fosse]

The cost of batteries can much lower than described above. First a 70% duty cycle is extremely low for lifepo. Some very sophisticated users on this forum go to or beyond 90% routinely, and testing on this chemistry has demonstrated that allows for rated cycles. There’s nothing wrong with buying more batteries than you need but the deep discharge qualities of lifepo is one of their attractions.

I won’t argue that or how much you need to know to build your own, but even as stated the price differentials leave a lot of room for learning as you go. At current pricing for 280ah cells the system above a 24v 560ah, costs between 2500-3000. Here are the costs I’m seeing:

16 280ah cells - shop a little prices vary $2025
Daly 250A smart BMS and accessories. $250.
1/4” x 72” copper bar $60
10 ft 2/0 wire and terminals. $100
Fuses and fuse blocks. $100. = 2600

If you are handy you spend a month learning and build this battery. You’ll save 5-7k.

What is this 1/4” x 72” copper bar?

Thank you