On My Giant Bike the App tells me more precisely what % Level I am currently at.

So I figured out a Formula to

** "Time" the % Needed.**
(for my battery & charger)

It is as follows:

**2.25 Minutes for every % of charge needed.**
Example:

If Battery is currently at 32%

But I want it at 80%

Take 80% minus 32% and it Equals 48

48 X 2.25 minutes = 108 minutes

That is 1 hour & 48 minutes Charge Time

This formula gets me within just a couple percentage points every time....................

HOW AM I DOIN RAVI ?

I've been convinced by members here with much more experience than I do to not muck with aftermarket chargers for my Giant...so I'll likely purchase another OEM Giant charger to use at work for days where I deplete the battery too far on a morning ride to get home in the afternoon.

I really like the idea of

@CSH's post above for calculating the approx time of charging, and had some questions on the maths and the Giant specs for my battery (Giant Revolt with a 375Wh, 36V battery)

- Giant quote 375Wh, 36V, 13.8Ah for my Revolt (https://www.giant-bicycles.com/au/revolt-eplus-pro-2020 ) - but 36V x 13.8Ah = 497Wh, so either the battery is > 375Wh or the 13.8Ah is more like 10.5Ah - I'm assuming the latter (375Wh and 10.5Ah) - can anyone comment? I'm guessing Giant just incorrectly quoted the Ah rating from one of their 500Wh bikes (or Marketing just getting funky/enthusiastic) ??
- the Giant EnergyPak smart charger is quoted at 6A, which seems a lot to be dumping into a 10.5Ah battery - just under 0.6C - whereas if the battery was a 500Wh 13.8Ah, the 6A charger would only be charging at 0.43C (I realise the Giant charger is "smart" and will back off the amps when getting above 80%) - is charging a 10.5Ah battery at 6A (0.57C) too fast, or remains fine as long as I let the battery cool after a ride prior to charging and monitor temperature during charging?

Back to some maths - I'm keen to come up with some numbers to approximate charging times similar to what

@CSH did above.

My battery is 375Wh 36V, and the Giant specs on the charger claim 6A current - which is a lot - next time I'm charging I'll take note to feel how hot the DC.

I'm assuming the Giant smart charger charges at 42V, and up to around 80% battery capacity should be supplying up to 6A to the battery.

- 6A x 42V = 252W - ie what the charger is delivering assuming full current (6A)
- 375Wh/252W = ~1.5hours to full charge (ignoring that the "smart" charger will back off the current once the battery hits ~80% or so) -
**this seems too quick** - have I got my maths wrong?
- assuming the above is correct 90 minutes for 100% is 0.9 minutes for 1% or 54s for each 1% - which again looks
**way to short** compared to @CSH 's calc above of 2.25min of each % charged - have I got my maths wrong?

@CSH if I backwards engineer your numbers of 2.52min for every 1% of charge increase, that's 252min or 4.2h to fully charge (100%) - which "feels" about the right amount of time to fully charge a depleted battery - but it obviously depends on the battery size (Ah), voltage, and charger current.

If I assume (maybe incorrectly) your Giant has a 36V battery and the same smart charger as I have (charging at 42V and 6A max and ignoring "smart" charger reduction in current at the top end), my maths again appears way out:

42V x 6A = 252W

252W x 4.2Hours = 1058 Wh - and I'm assuming the battery on your Giant isn't 1KWh

Somewhere along the line I've got the maths wrong...but I don't know where ?

cheers

Mike