My Freedom Won battery is rated at 200AH.

My mother's inverter trolley has 2 × 105AH battery. 210AH.

Actually I have a lot more power than she does, as my battery pack is 50V, whilst hers is 12V.

Why is the AH measurement used for batteries? It really doesn't tell you how much power they store. 

Surely it is more useful to say that my battery is 10KWH and she has two 1.26 kwh batteries. 

Edited January 5, 20232 yr by Bobster.
may/my

Eish @Bobster.I'm with you on this one. I feel the ah is lost in translation. It needs the Voltage to be understood fully. But then again ah is just that Amps over a period of time. Where as kWh is more specific about Power over a period of time. So I guess the ah Is pretty misleading. 

Your FreedomWon Home Lite 10/8 is a monster in comparison to the trolley 210ah 🤣🤣 Talk about a knife  🔪 to a gun 🔫 fight 🤣

 

I guess Ah has always been used and applied to the spec of a specific battery. When reading the specs you know you are looking at a 2V, 6V or 12V battery. Now that we talking PV the norm has become power as Steve indicated. More different voltages are at play. Also in the past there calc were done by guys knowing the relationship between Ah, volts and kWh. Nowadays non technical guys are involved and kWh is the better method. Power used have always been expressed as kWh (units) so not new. 

10 hours ago, Bobster. said:

My Freedom Won battery is rated at 200AH.

My mother's inverter trolley has 2 × 105AH battery. 210AH.

Actually I have a lot more power than she does, as my battery pack is 50V, whilst hers is 12V.

Why is the AH measurement used for batteries? It really doesn't tell you how much power they store. 

Surely it is more useful to say that may battery is 10KWH and she has two 1.26 kwh batteries. 

I understand your reasoning. The notion of using  Ah metric is one of a legacy issue. 

The atomic unit of  electric-chemical storage is a cell. In the case of lead acid this cell voltage is nominally fixed 2V wether that cell is small or big. The larger cell has more storage, and this ability is expressed as ampere-hour rating. 

Back in the day you only  got single cells and you built your    requirement  up using individual cells wired up in serie. On the railways we had banks of 55 cell blocks to make up 110vdc. So if you need to replace and buy one cell, you had to know  the size of the cell, and therefore you ordered using Ah rating. 

12v battery is really a modern convenient package of 6 individual cells, as you might know. 

Y'all have some great points... For the most part I use kWh instead of Ah, it's a more relevant measure.

The issue is that with lithiums you can have the same capacity but with the deeper DoD, where acid batteries can only discharge to about 50% where most good lithiums can go down to like 10% without issue. Ah does have it's place in testing etc, when testing a 100Ah I will draw 50Ah at 20A for 2,5 hours with a load tester. At that point the voltage should range between 12,2V to 12,5V and that's a good way to pick up issues with batteries that charge up to the right voltages but discharge to like 11V instead of the expected 12,5V after that time. (For customers who complain about battery life, since I don't have access to loads and other measurements this is one I can do in the lab)

So at the end, it has it's uses and from a technical perspective it is a useful measure to have but kWh will serve the general public better...

Because with older battery chemistries like lead acid, the energy(kWh) it delivers varies drastically due to voltage voltage sag and how much current you draw from it. Its almost impossible to rate a lead acid battery in kWh because it would depend on the application. 
 

If you look at the rating on a lead acid battery it says 200Ah (0.2A). That means you will get 200Ah from the battery if you constantly draw 0.2A amps from it. Yes 200 milliamperes! that is not a typo. But if you constantly draw 5A from it then you will only get 180Ah out of it. The efficiency of the battery drops like crazy depending on the current draw. If you draw hundreds of amps like in a typical UPS/inverter application you will be lucky to even get half of the 200Ah it’s rated for. In the data sheet of each battery there is graph to show the relationship between capacity and current draw. 

Also, to calculate the energy in KWh, you need to take the voltage into account. Lead acid batteries have crazy volt drops when high current is drawn which again stuffs up the energy calculation. So I think to keep things simple they stuck to amp hours.

lithium batteries are different, the voltage remains relatively constant and you can pull 100’s of amps without effecting it’s efficiency much. So they can use energy in kWh as a rating which is indeed a much better way to rate an energy storage device. 
 

 

Edited January 5, 20232 yr by BrettB

Note the capacity ratings on a Pb battery are also determined over a gentle 20hr discharge. That's not how you use them is it? I think discussing the merits of LiFePO4 over Pb is like flogging a dead horse. Pb batteries are like an overweight stripper, cheap, heavy, they don't do much work, widely available and in the end you'll regret your decision.

Edited January 7, 20232 yr by WJP

4 hours ago, WJP said:

Note the capacity ratings on a Pb battery are also determined over a gentle 20hr discharge. That's not how you use them is it? I think discussing the merits of LiFePO4 over Pb is like flogging a dead horse. Pb batteries are like an overweight stripper, cheap, heavy, they don't do much work, widely available and in the end you'll regret your decision.

If one can only afford a 1400 and not a German 3L car I would rather go for a 1400 than walk. 

The same we find 9 out of 10 apartments don't have an inverter and have LED lights when they can easily power lights with a single lead acid. For LS lead acid can still be OK. Daily cycling yes one would go for a lithium. 

Say you in a flat and using lead acid for lights and router only you could recharge it fully during the times that the grid is on. 

As things look now LS seems to stay with us all the time so you are spot on. 

It all boils down to the specific application. 

1 hour ago, Scorp007 said:

If one can only afford a 1400 and not a German 3L car I would rather go for a 1400 than walk. 

The same we find 9 out of 10 apartments don't have an inverter and have LED lights when they can easily power lights with a single lead acid. For LS lead acid can still be OK. Daily cycling yes one would go for a lithium. 

Say you in a flat and using lead acid for lights and router only you could recharge it fully during the times that the grid is on. 

As things look now LS seems to stay with us all the time so you are spot on. 

It all boils down to the specific application. 

If the budget is limited just buy a smaller LiFePO4 battery. There are some 12V lithium drop in replacements as small as 7Ah. Lead is dead baby.

When it comes to consumer devices like your mom's trolley, I believe that marketeers rely on consumers' unit blindness to confuse them into simply picking the product with the higher visible number. And why not choose the specification unit that will let your product sell better - not kWh in this case - when 100 Ah x2 makes it look so appealingly close to your monster and such excellent value. Who even has heard of voltage? Megapixels anyone?