What is my watt meter telling me?

I recently installed a Luna cycles 150a watt meter in my system. ebike kit 48v 20ah 13s7p allcell 22amp controller. Todays ride 23.1 mi. Peak amps 20.7, I understand that; 1059.4 peak watts delivered, I understand that; 49.76 minimum voltage, I understand that as "sag" under load. total energy delivered 419 whrs. ?? total charge delivered in amp hrs 4.6 ?? out of how many/much?? What's the difference between energy delivered whrs and amp hrs?? How do I figure out how much is left in reserve?

Watt hours is the most accurate. Amp hours is based on the voltage. Watt hours equals E = 5W × 3h = 15 Wh. Whereas Amp hours is how many volts X amps x hours. Most batteries are rated in amp hours, but a higher voltage pack can have same amp hours as a lower voltage pack, but the higher voltage pack has more watt hours! I use amp hours to measure my packs, but I also monitor the packs very carefully and remember that as the pack degrades the amount of amp hours and watt hours degrades. For example, I have 2 44v nominal 16 ah multistar packs so the max watt hours I should be able to take from it is 704 which is 44v x 16= 704 wh. But, I never take that much, because I want my batteries to last a long time. :|

Shoestring said:

How do I figure out how much is left in reserve?

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You'd have to run it down ot the battery cutoff (bike stops working) and then note down the final Ah and Wh reading.

Then that is your actual capacity.

Whether the battery will realyy deliver the rated Ah or Wh will dpend on several t hings, including it's age, design, BMS setup, marketing hype if any, and wehtehr it is being used within the cells' rated capabilities.

Also note that for wh ratinig; Luna prints this on the label but it may be very inaccurate, see this thread for one I have here
https://endless-sphere.com/forums/viewtopic.php?f=14&t=81108&hilit=+luna

Ok, I'll start with a full charge and run it down until the bms cuts the power, then note the meter totals. Then work backwards to see how much in reserve is left in the tank. I'm assuming the amount of energy stored in the battery will be the same regardless of the speed at which it is discharged? Either pull 20amps for 1 hr or 1amp for 20 hrs. total energy delivered would be the same, correct? Or would discharging at a slow constant rate yield more watt hrs?

As the BMS will cut out on low voltage, it is obvious that the available energy will not be same at e.g. 0.05C discharge and at 1C discharge rate due voltage sag...
In addition, the delivered energy is also reduced by losses on internal resistance of the battery.
In other words, the Ah ratio of two modes of discharge is not same as Wh ratio, the Wh ratio is even worse than Ah ratio due mentioned losses.
If the lead battery is in question, than you have third cause of reducing Ah at high discharge rate: the Peukert constant...

Actually,,, if you discharge your battery at a very very low rate, say 200 watts, you will get a bit more wh from it than if you pull 700w continuous. The slower you discharge, the less you heat the battery. It's not a lot, but something to know if you are desperate to go a long way on very little.

But do your test riding as you would normally ride, then work with that total watt hours number.

Another thing to anticipate, if you keep riding into cold weather, you will get less from your battery then, when it's well below 50F. When it gets really cold, keep the battery warm by bringing it inside if you can, and insulate your battery compartment.