Need some guidance on watts up meter

[SarasotaSlim]

Thank you for the invite as im new to the electric bikes . Just purchased the Bagibike 48v folding ebike . The display only shows a battery graph of the status of the battery and no info on the true volts or amps . So I was told to get a Watts up meter to get these readings. But b4 i order one i need to know how to hook it up to the bike to get these readings ,remember im new to these bikes and my knowledge is limmited .

 

[Rassy]

In general, you got good advice, but for your application it may not be so good. You have to get access to the positive and negative wires that run between your battery and your controller. If your controller is located within the battery rack that may be very difficult or even impossible. Even if you can get access to these wires, splicing in a Watts Up meter would probably void any warranty on the new bike. More info would be necessary.

Even though I use Watts Up meters on both of my trikes, they are powered by kits that I installed and neither access to the wires nor warranty issues applied.

On several bikes that I put together for friends/relatives there was no interest in having access to the information the Watts Up meter provides, and on one where I did install a meter, it was never used and on a later upgrade I removed it.

Back to your case, You can get a fair idea of your amp hours or watt hours used by simply observing how long it takes to charge your battery. Start with a fully charged battery, take a ride, note how long it takes to recharge the battery, calculate the usage.

Here's an example using made up data: 48 V 10 AH battery, 2 Amp charger, ride 10 miles, require two hours to recharge the battery. Since it took two hours with a 2 Amp charger to recharge the battery you used 2 A * 2 H = 4 AH from your 10 AH battery.

We normally express this information as WH instead of AH because that allows us to directly compare usage between systems of different voltages. Using the formula, AH * V = WH, and since the voltage always varies during usage, for simplicity just using 50 as the average voltage, your charger put 4 AH * 50 V = 200 WH back into your battery, which has a total capacity of 10 AH * 50 V = 500 WH.

While using the above values isn't quite as accurate as a Watts Up meter would be, I find it matches up pretty close with my 48 V LiFePO4 batteries. The important point is, you will have a pretty good estimate of how far you can ride on a charge given the speed and terrain of the test ride. You can also make the same ride at a different speed to see how much speed affects your battery consumption, etc.

 

[docw009]

There are two kinds of Watts UP meters.

The one on the left is easiest to use, as you plug your charger into it, but it's very high level. It will tell you how many watts your charger uses and you do some math to estimate how much actually went to your battery, much in the manner Rassy explains.

The one on the right is intended to be attached (a) between the battery and controller on your ebike and also (b) between the charger and battery. If you had two of them, as they are inexpensive, the latter could be a permanent connection but the one on the bike you would probably attach with connectors for occasional checking. When mounted on the bike, they are too hard to install where you can see them when riding.



When you put it on the charger, all you can get is the amp-hours (Ah) needed to refill your battery. In practice, I've found that this will be the same as the Ah that were used while riding. The meter also displays the equivalent watt-hours. What you won't get is instantantaneous amps or watts being used while riding. Here a pic of one wired into a charger cable,

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You really want to put it on the bike? Easy with a home-built as we have our battery cables open. On a manufactured bike, battery wires are inside the frame, where they should be, nice and safe. You have to dig them out, and attach the wattmeter. You usually do it with connectors so soldering skills are needed. In addition, you cannot install it easily so you can view the data while riding. Most of us look at it after a ride. The meter does store peak amps, so at least we know what the peak watts were.

Here's what it would look like on a bike like yours, with the slide out battery. The battery wires were brought outside and connectors installed, allowing the meter to be connected.. The connectors were actually installed to allow other batteries to be connected, but they also allow a wattmeter.