Range, battery capacity, and charging efficiency

[bob2.0]

I repaired my broken motor recently (replacing rusted magnets) and the battery had not been fully charged for a few months because of this.

This week, I charged it up and riding around to test it working, and the battery is OK.

Everything is fine and I seem to be getting slightly better range. Maybe the motor is working better than before now.

This week I got about 82 miles (132 km) on about 80% charge, at high speeds on fast roads, which is good and better than it was before.

[Odo read 88 miles, but I know it over-reads by just under 10%. Battery was at 70.0V, about 20%. fast = over 75 kph for >80% that mileage.]

My question to you is whether I have a 120Ah capacity, because it seems very good to me if that was 7.2 kWh. BUT when I charge it up it uses 1kWh per 10%.

So, it's either doing about 14 miles/kWh (which seems very high) but charging up at 70% efficiency (which seems very low).

Or, it's actually 120 Ah (it says 100 Ah on the battery itself), doing 11 miles/kWh (seems about right) and charging at 85% (seems about right).

Do you have a way to calculate how much charge goes into your battery, and what your efficiency is when riding?

[jeff-jordan]

...
This week I got about 82 miles (132 km) on about 80% charge, at high speeds on fast roads, which is good and better than it was before.
...
My question to you is whether I have a 120Ah capacity, because it seems very good to me if that was 7.2 kWh. BUT when I charge it up it uses 1kWh per 10%.
...

First, 132km with one charge and some remaining percentage in the battery is quite good!
Maybe you really have a 120Ah battery (or something in between, maybe a good 100Ah with about 110Ah real capacity).

But it's not easy to calculate the battery capacity based on these observations.
The efficiency of the charger is an unknown quantity (usually between 80 and 95%, but it depends on temperature, grid voltage (240 or 220V), battery voltage (usually more efficent when the battery is low) and whether the battery is charging normally or balancing (at the end).
Furthermore the common power meters (that you use to monitor the power consumption) are pretty inaccurate (+/- 15% is not uncommon).

If we assume an average efficency of 80% (for the genuine 10A charger), 10hours would mean about 8kWh.

The only way to get more reliable results, is to measure the charging process (at the bike) with a so called coulomb meter, like this one or that one which will, by the way, give you much more reliable information about the charging state of the battery than the unreliable bar gauge at the speedo display.

The first link is for a coulometer that's easy to install (with hall sensor to measure the current), but everything but waterproof (so you have to place it in the "tank compartment"). The second one requires some alteration at the high current wiring of the bike, because you need to loop in a 150A shunt.

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Not to forget: there is an easy way to determine whether your battery is a 100Ah or a 120Ah model. Just look at it's label

[bob2.0]

Label says 100Ah.

It does not have that bar code though. Maybe it was a prototype 120Ah?