Understanding Batteries and voltages

[John117]

Hi guys, I am planing on doing a solar project and saw a video saying that 48v batteries are the way to go nowadays. Because it is more efficient and cheap. I understand the efficient part, because you don't need thick cables, and that's the same reason it should be cheaper, right? (less copper)
Looking for batteries on Amazon I get these 2 as an example, obviously the 1k one is HUGE, and it should have more capacity but is it cheaper like watt-hour or something?

51.2V 100AH LiFePO4 Battery $1,099.99
12V 100Ah LiFePO4 Battery $170.99

I am guessing that W=Volts x Amps, right? Why not advertise the watts? And what if I have 4 solar panels that are 200w each but at 12v? Even if I connect them in series I can only get 48v, is that enough to charge the huge battery on this example? Do I have to always have a higher voltage than the battery in order to charge it right? So I probably have to add another panel in series to get 60v? I know panels are now coming in higher voltage also. But I just want to understand this.

**************************************************UPDATE ************************************

I just wanted to add my idea to see what you guys think



Thank you in advance!

 

[Nobodybusiness]

Hi guys, I am planing on doing a solar project and saw a video saying that 48v batteries are the way to go nowadays. Because it is more efficient and cheap. I understand the efficient part, because you don't need thick cables, and that's the same reason it should be cheaper, right? (less copper)
Looking for batteries on Amazon I get these 2 as an example, obviously the 1k one is HUGE, and it should have more capacity but is it cheaper like watt-hour or something?

51.2V 100AH LiFePO4 Battery $1,099.99
12V 100Ah LiFePO4 Battery $170.99

I am guessing that W=Volts x Amps, right? Why not advertise the watts? And what if I have 4 solar panels that are 200w each but at 12v? Even if I connect them in series I can only get 48v, is that enough to charge the huge battery on this example? Do I have to always have a higher voltage than the battery in order to charge it right? So I probably have to add another panel in series to get 60v? I know panels are now coming in higher voltage also. But I just want to understand this.

Thank you in advance!

48vdc vs 12vdc allows you to run higher wattage inverters at lower amperage.

3000 watt inverter at 48v = 62.5 amps
3000 watt inverter at 12v = 250 amps.

You can run smaller gauge wire with higher voltages.

Most batteries are listed in Amp Hours (AH) or Watt Hours (WH).
AH are a measurement of charge
Wh are a measurement of energy.
51.2vdc x 100 AH = 5200WH

Divide your cost by the WH to find $ per WH.

$1099/5200= .211 per Wh
$171/1200= .144 per Wh

As far as charging them you need a charge controller. Preferably MPPT charge controller.

The controller would take your panels and convert to the appropriate voltage for charging.

 

[John117]

48vdc vs 12vdc allows you to run higher wattage inverters at lower amperage.

3000 watt inverter at 48v = 62.5 amps
3000 watt inverter at 12v = 250 amps.

You can run lower gauge wire with higher voltages.

Most batteries are listed in Amp Hours (AH) or Watt Hours (WH).
AH are a measurement of charge
Wh are a measurement of energy.
51.2vdc x 100 AH = 5200WH

Divide your cost by the WH to find $ per WH.

$1099/5200= .211 per Wh
$171/1200= .144 per Wh

As far as charging them you need a charge controller. Preferably MPPT charge controller.

The controller would take your panels and convert to the appropriate voltage for charging.

Thank you so much! so in that example the 12v is actually cheaper than the48v battery. Interesting!

 

[alcook62]

Thank you so much! so in that example the 12v is actually cheaper than the48v battery. Interesting!

Don't fixate on price alone. If you want a 48-volt system you must combine 4 of those 12-volt batteries in series to achieve the 48 volts. Each of those 12-volt batteries has its own BMS that manages its respective battery. The problem is when the 4 series battery has been cycled repeatedly the individual batteries drift out of balance from each other. The system will lose the ability to produce full power potential due to either over-voltage/under-voltage cutoff when the 4 batteries drift out of balance. This can be mitigated, however, it can also be prevented altogether by just purchasing a single 48-volt battery.

 

[Nobodybusiness]

Thank you so much! so in that example the 12v is actually cheaper than the48v battery. Interesting!

Per WH yes but that doesn’t tell the whole story as you know..

48vdc is definitely way to go..

 

[John117]

Don't fixate on price alone. If you want a 48-volt system you must combine 4 of those 12-volt batteries in series to achieve the 48 volts. Each of those 12-volt batteries has its own BMS that manages its respective battery. The problem is when the 4 series battery has been cycled repeatedly the individual batteries drift out of balance from each other. The system will lose the ability to produce full power potential due to either over-voltage/under-voltage cutoff when the 4 batteries drift out of balance. This can be mitigated, however, it can also be prevented altogether by just purchasing a single 48-volt battery.

I see!! no one explained that in the videos, thank you! I added an image of my idea, you think it will work?

Per WH yes but that doesn’t tell the whole story as you know..

48vdc is definitely way to go..

Thank you!!