Kemosabe70 said:
Also, I would appreciate an accurate reading of where the battery is at.
If it has an LED meter on the side of the battery, that's generally good enough for most uses, as long as you are not riding it to empty most of the time. So you probably don't need a meter on the handlebars for this.
Keep in mind that no meter can tell you what the battery's present state is, directly.
You can use a wattmeter that can read negative Ah (or Wh), and detect current in both directions, *and* that remembers all of it's readings when power is disconnected (like the CA and some of the cheap wattmeters--many don't). Then there are a couple ways to "track" the battery capacity.
Drain the battery completely till it shuts down, then reset the meter, and disconnect the battery from the bike (so no slight drain from the bike alters the readings). Charge the battery thru the meter, causing it to go negative in Wh or Ah, until it's full. Now it will read the actual capacity of the battery, with a minus sign. As you ride, it will get lower and lower, till the end of the ride, or until the battery shuts off, which will be somewhere near zero (but may not be exact because of the nature of this stuff). Disconnect the battery from the bike, and recharge thru the meter, which "increases" the readout as it recharges.
Alternately, charge the battery to full, then hook up the meter, reset it, As you ride it will count up how many Ah or Wh you are using, so ride until it shuts off. When it does, that's the max reading it should ever show. Then you disconnect the battery and meter from the bike, and recharge thru the meter.
Both of these methods will accumulate error over time, depending on a number of factors, so you don'[t want to depend on either extreme (full or empty) being accurate. But it works ok between the extremes. The "disconnect from bike" can be a switch, or a plug to disconnect, there's a bunch of ways to wire it up. If the battery has separate charge and discharge ports then you also have to move the meter from the dishcarge port to the charge port and back each time, or wire up a switch to do that. If it has just one port, it's simpler. (this depends on it's BMS type).
Alternately you can use just voltage as a general indicator. That's how the little meters on the side of the battery work, with a number of LED lights. This works reasonably well with a healthy battery.
Some throttles have a voltmeter that gives you more detail, or the wattmeter can be used with it's voltage display.
A wattmeter, if it also has a speed sensor on it, can be used to measure Wh/mile, which keeps track of your usage over a ride. This lets you have an idea of how mcuh capacity you actually use per mile, so you can guesstimate your range based on your pack's capacity.
So there's a number of ways to track the battery usage / capacity...but they are all really telling you what it was *last time it was charged*, or guesstimating based on voltage.