Can Ah be translated to Wh and vice versa?
- Thread starter rg12
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scootergrisen
100 W
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- Feb 26, 2018
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Volt * Ah = Wh.
So i guess you are using a 12 volt system.
So i guess you are using a 12 volt system.
scootergrisen said:
The voltages differ...
How did you get to 12V?
I remember that it isn't linear calculation with watt hours, since it changes due to voltage or something...maybe I remember wrong?
So I can just switch back and fourth between the two and the calculation would be right? like 0.11ah to 1.52wh?
For devices that are continuously totalizing, as the voltage changes, the ratio between W and A is changing.
For static conversion, take the average voltage over that time period.
Ah is the better unit for battery SoC, SoH and energy consumed.
Only use watts when voltage conversion is involved.
For static conversion, take the average voltage over that time period.
Ah is the better unit for battery SoC, SoH and energy consumed.
Only use watts when voltage conversion is involved.
scootergrisen
100 W
- Joined
- Feb 26, 2018
- Messages
- 154
My battery is 48 volt 25 Ah so its 1200 Wh.
48 * 25 = 1200.
48 * 25 = 1200.
That 48V is just a "nominal" ballpark. At 100% Full charge may measure 55+V, when nearing "empty" under heavy load may drop to below 40V, with lots of ups and downs in between.scootergrisen said:
The specific numbers will also vary depending on cell chemistry.
That 25Ah is likely to be a marketing exaggeration, and even with accurate measuring tools, the actual capacity will vary by **a lot** depending on discharge current rates, temperature and the cells' SoH.
Measuring in Wh those variations will be **much** greater, which is why sticking with Ah is a good idea.
john61ct said:
Watt hours is good for calculating a pack's capacity, since power is power so if we try to compare 20ah 60v to 20ah 72v you wouldn't get the same range but comparing watt hours will provide more accurate picture.
So to my question, I can't have the system convert wh to ah or vise versa in a comparable way right? since the flactuations of the wh measuring system
As I said, Wh is indeed useful when comparing systems at different nominal voltages.
Just measure at Ah with your meter, and multiply times the average (or nominal) voltage to get Wh.
What type of pack are you monitoring, cells used, chemistry, how many in series? A link would be ideal. Also to the meter.
Just measure at Ah with your meter, and multiply times the average (or nominal) voltage to get Wh.
What type of pack are you monitoring, cells used, chemistry, how many in series? A link would be ideal. Also to the meter.
john61ct said:
Nothing specific, am working on a device with a freelancer and was wandering how to implement the change between wh to ah and I guess I will have him make it go to 0 when switching between the two since they can't be translated in an exact way
Well they can be, for instantaneous Amps vs Watts, based on what the voltage is at that instant.
If I were designing a coulomb-counting meter I'd track both separately internally, then display either or both Ah/ Wh as the user selects, perhaps with an "average voltage" over the tracking period so it makes sense.
If I were designing a coulomb-counting meter I'd track both separately internally, then display either or both Ah/ Wh as the user selects, perhaps with an "average voltage" over the tracking period so it makes sense.
AZeBikeGuy
100 W
When "counting coulombs" sample the voltage when sampling the current for totalizing (accumulating) the current, multiply the current by the voltage and totalize for Wh
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