Lithium batteries for domestic ESS - Ampere-hour comparison

mudell

Hi all,

I’m new here and I would like to ask a question for my better understanding of Ampere-hour ratings of LFP batteries. Would be great if someone would spare some time to help out !

Assuming I have 2 batteries each having 10kWh capacity:

Battery 1: 10kWh, 48V, 208.33Ah (low voltage)

Battery 2: 10kWh, 450V, 22.22Ah (high voltage)

My question is- does this mean that battery 1 will last around 9x longer than battery 2, due to the higher Ah rating of battery 1?

Thanks for helping !

DonovanCSampson

Most lithium ion battery cells run at approximately 2000 mAh, or 2.0 mAh. When you combine these cells together in a series, they still produce only a combined 2.0 amp hour. In a series, it is the voltage that combines, not the amp hours.

Regards: rv battery monitors

EdwinMoriarty

Not Exactly, Mudell, the cycle life of a battery depends on the actual using situation.

The rated Ah of battery 1 is higher than battery 2, but it doesn’t mean their DISCHARGE CURRENT level is better than battery 2, do you understand?

Let me show you an example, 48V, 208.33Ah, and their rated discharge current is 100A(about 0.5C), and when you discharge in this current, the power is about 5 kw.

450V, 22.22Ah, rated discharge current is 11A(Also about 0.5C), the power is also about 5 kw.

Then you should know, in their rated discharge current, you should refer to the cycle life shown on the datasheet, but not just to consider which battery has higher capacity.

JeffClarke

Hi Mudell….To answer your question…No…they will last the same amount of time. But I think there maybe something you are misunderstanding.

Without getting distracted with all sorts of clever comments about minor variations in battery physics…etc, and by just focusing on basic electrical theory, maybe the following will help.

Power = Voltage x Current ( P= E x I)

Your Battery 1 and 2 specifications fulfill the formula. Consequently they supply the same power to the load, ie 10Kw.

The current draw from a load consuming the same amount of power to operate it, is dependent on the nominal voltage to drive that load. You could have two separate water pumps rated at 500W. If Pump 1 had a nominal input voltage of 450V (same as Battery 1) then it would draw 1.11A only (P=E x I or if translated, I = P / E). The pump would run for 20hrs off your 450V - 22.22A/Hr Battery.

Pump 2 on the other hand might have a nominal voltage 48V (Same as Battery 2) and considering it is also rated at 500W, it will draw 10.42A. Again same basic formula (P=E x I or if translated, I = P / E). The pump would run for 20hrs off your 48V - 208.33A/Hr Battery.

The term 10KwH is the most inappropriate term used to rate the capacity of a battery. It stores 10Kw of power, and if you have an appliance that consumes 500W, then that battery will last 20hrs. That is the basic thing you need to understand. Nominal voltage of the battery and appliance must match, and that then dictates the current draw.