12 V 300 amp hour in series

[PanamaTripp]

I’m designing an off grid system for a small house after watching Will ‘s video on the chins 12 V 300 amp hour lithium iron phosphate battery I have decided to go with four of them in series to make 48 V. I’m new with lithium iron phosphate batteries, and cannot figure out how to calculate the watt hours if I hook for 12 V 300 amp hour batteries in series please help thanks guys

 

[BentleyJ]

A 48V battery would be a better choice than 4 x 12V batteries in series.
Your question: 300Ah x 51.2V (4 batteries x 12.8V) = 15,360Wh

 

[siegex]

A 48V battery would be a better choice than 4 x 12V batteries in series.
Your question: 300Ah x 51.2V (4 batteries x 12.8V) = 15,360Wh

I don't understand isn't a 48v battery consist of alot of batteries allready in series?

What's the benefit of making your own 48v system versus buying one pre made?

 

[MichaelK]

I’m designing an off grid system for a small house after watching Will ‘s video on the chins 12 V 300 amp hour lithium iron phosphate battery I have decided to go with four of them in series to make 48 V. I’m new with lithium iron phosphate batteries, and cannot figure out how to calculate the watt hours if I hook for 12 V 300 amp hour batteries in series please help thanks guys

Did the manufacturer specifically state that this model of battery can be put in series? You are better off buying a 48V battery that has a BMS designed for 48V. There is no guarranty that four 12V batteries in series can stay balanced.

That being said, you need to remember the basic electrical mantra, in series volts add while amps stay the same. In parallel, amps add while voltage stays the same.

In your hypothetical case, the first half of the mantra applies, in series volts add while amps stay the same. So, you get 300Ah at 48V, or a total of 300Ah X 48V = 14,400Wh. Assuming you never want more than 75% depletion, that means ~11kWh of available power.

 

[BentleyJ]

I don't understand isn't a 48v battery consist of alot of batteries allready in series?

Yes, and the Battery Management System has a connection to ALL the cells in that one battery therefore can keep all the cells balanced. With 4 separate 12V batteries you will end up with 4 batteries that are each balanced internally but are out of balance with the others.

What's the benefit of making your own 48v system versus buying one pre made?

With off-the-shelf, manufactured battery prices coming down the benefit of a DIY project doesn't make as much financial sense as it used to not to mention Electrical Code is now requiring UL listed products.

That said, IMO the benefit of a DIY battery is being able to change a cell or the BMS yourself and not have to worry about violating the warranty or if some proprietary part is available and for some of us its a fun project.

At this point in battery development, the beneifit of using closed loop communication with the inverter is limited or can be worse than just using voltage control.

 

[pollenface]

With off-the-shelf, manufactured battery prices coming down the benefit of a DIY project doesn't make as much financial sense

really depends on your supplier and the price for each option available to you, in my case DIY makes more financial sense

There is no guarranty that four 12V batteries in series can stay balanced.

I am using a HA02/powMR 48v balancer which does precisely that, without it I notice a small deviation of the end batteries.

 

[Dagoth Ur Does Solar]

It should also be mentioned as well that on top of the issues with balancing each battery, you're likely to save money going with a 48v battery, as you don't need busbars or fuses between batteries.

I agree with Will's recent video that in the current year, 12v just doesn't make sense for most people. There's obviously exceptions, though.

This is coming from me, who recently built a 12v system and wish I'd have just gone with a 48v from the onset.