Bat-man display

[Clem]

Hi, few weeks back I've purchased a WATT METER with the idea of knowing how much "fuel" there was left on my Battery, then I realized the restrictions of not being able to read it as I was riding so I've bought the bat-man as this unit can be installed on the handlebar. I am writing to you guys with the hope somebody will be kind enough to share "HOW TO READ THE DAM THING" with me.
BAT-MAN has 3 screens of which I use only 2 (use my C965 for Assist Levels, speed etc.) one of the Screens shows as an example: 0.00A, 49.98V, 0W & 8.622Ah and the next screen: 15.9Ap, 0.10Vm, 5162Wp & 0.0Kph. So my question is; out of these 2 Screens what is the information I will be taking in consideration to find if I still have enough "Fuel" to continue my journey. Thank you for taking the time to read and put some input. Best regards Clement

[Rodney64]

It would be the first screen. 49.9 volts remaining and the battery has used 8.62ah

Which battery do you have and voltage?
What amp hour is the battery?

[Clem]

Thanks, so if I am running a 48V 10 Ah battery how do I use those 2 readings to determine how much do I have left?

[ykick]

8.6Ah consumed from a 10Ah battery pack resting at 50V (3.85V/cell group) indicates a very healthy battery pack, IMO.

At which point I would keep an eye on voltage drop while under load. 48V battery pack sagging to about 40V under full load is basically empty.

Newer color dash/displays help since they have an easy to read volt/power meter.

[JPLabs]

Subtract Ah used from Ah in the pack when you started, to know how many are left.

Or, look at Voltage, compare to your Low Voltage Cutoff, and have a rough idea how close you are. But voltage plummets fast at the end.

You can do better, for a little work. Bat-man counts Watt Hours. It's disabled in the firmware since folks got confused, but email the Bat-Man owner and he can give you firmware which shows Wh used when the motor is not using power, in the same place you see Watts when you are using power. Wh are the measure of energy in a pack.

Your pack starts with 10 Ah at 48V nominal, so about 480 Wh if fully charged. Know your Wh vs charge level (easy, at 80% you have 0.8 * 480). This is the best way to use the Bat-man, but just using Ah as shipped is still pretty good, and much better than just watching voltage.

[Clem]

I remember when first read and made enquires I was shown what you JPLabs mentioned; if I have a 48V/10Ah Battery =480 Watts (fully charged) this is the "FUEL" I have to play with correct? Would I be also correct when you mentioned in the last paragraph "This is the best way to use Bat-man" ? please confirm this to make sure I understood your statement. On the other hand I still like to learn Bat-man as it comes (Ah) but how do I work it out Ah? Example: using a fully charged 48V/10Ah and after done 30kms the reading is 8.622Ah "HOW do I work this out"? I don't seem to be able to understand it, could you be able to describe the method you use when reading Ah please? Best Regards Clem

[Fred]

I remember when first read and made enquires I was shown what you JPLabs mentioned; if I have a 48V/10Ah Battery =480 Watts (fully charged) this is the "FUEL" I have to play with correct? Would I be also correct when you mentioned in the last paragraph "This is the best way to use Bat-man" ? please confirm this to make sure I understood your statement. On the other hand I still like to learn Bat-man as it comes (Ah) but how do I work it out Ah? Example: using a fully charged 48V/10Ah and after done 30kms the reading is 8.622Ah "HOW do I work this out"? I don't seem to be able to understand it, could you be able to describe the method you use when reading Ah please? Best Regards Clem

You can use Ah to estimate how much "Fuel" you have left in the tank, although I suppose Watt-hours is technically more precise. In your case you have used 8.622Ah to go 30Kms or .287 Ah/Km. So if your battery can deliver the advertised 10Ah (and they can't always) your maximum range would be (10/.287) = 34.8Km. These numbers will vary depending on riding style, speed, amount of pedaling etc. I am guessing you did little pedaling and were moving at a good clip.

[Clem]

Thanks Fred, may I ask you what does tis .287 mean? In this particular trip I end up 49.98V and used 8.622Ah also used power level one and took it easy (Bafang BBS HD) Thanks again. Clem

[Fred]

Thanks Fred, may I ask you what does tis .287 mean? In this particular trip I end up 49.98V and used 8.622Ah also used power level one and took it easy (Bafang BBS HD) Thanks again. Clem

You burned 8.622Ah to travel 30Kms or in other words at a rate of (8.622 divided by 30) = .287Ah per Km driven on that particular trip. Most of the time, these rate of consumption numbers are quoted in Wh per Km or Wh per Mile with Wh being the true measure of energy consumed. Wh is the product of Ah and Voltage and quoting in Watt-hours allows normalization between different voltage systems (e.g 36V or 48V, etc.)

The reason I was suggesting you might be pushing the ride was that if we assume an average voltage of 48 during the trip, you consumed (.287 x 48) = 13.77 Wh/Km. On my last trip on a BBS02 equipped Fat Bike with some pedaling (and a far from svelte rider), I consumed about 8.8 Wh/Km. Being from one of the colonies like me, I assume you were actually measuring Km traveled and not Miles?

[JPLabs]

I remember when first read and made enquires I was shown what you JPLabs mentioned; if I have a 48V/10Ah Battery =480 Watts (fully charged) this is the "FUEL" I have to play with correct? Would I be also correct when you mentioned in the last paragraph "This is the best way to use Bat-man" ? please confirm this to make sure I understood your statement. On the other hand I still like to learn Bat-man as it comes (Ah) but how do I work it out Ah? Example: using a fully charged 48V/10Ah and after done 30kms the reading is 8.622Ah "HOW do I work this out"? I don't seem to be able to understand it, could you be able to describe the method you use when reading Ah please? Best Regards Clem

I think Fred covered this well already, but sometimes it helps to have a couple descriptions, so I'll bust it up into bullet points, with automotive analogies. The analogy is not perfect, though, gallons are more like Wh than Ah, but maybe this will help it all click:

• Amps are rate of flow. How fast you can discharge your pack. As in a 70A pack, one with a 70 Amp BMS.
  • Like how big the fuel system is on a car, in Gallons per hour.
• Amp hours are different. Amps flow, * time. If the pack can deliver 70A peak, that has nothing to do with amp hours. If the same pack can deliver 10A for one hour, it's a 10 Amp hour (Ah) Pack.
  • This is like gallons of gas in the tank.
• Volts are how much 'force' is behind that flow.
  • Like how much energy is in a gallon of gas. If 24V pack is gasoline, a 52V pack is Nitromethane. Nitro applies a lot more force to the pistons.
• Multiply Amp Hours * Volts to figure out how much energy is in the pack.
  • Just like the more gallons, and the more potent the fuel, the more energy is in a gas tank.

To use Amp Hours for 'how empty is my pack' estimation, you just need to know how many Ah you put into the pack when you charged, and how many you have used.

• If you charge the 10 Ah pack to 80%, you have 8 Ah in there. 10 * 0.8
  • Like 8 gallons in a 10 gallon tank....
• So, if you started with 8Ah, and during the ride you see you used 6Ah, subtract. You have 2 Ah left in the pack.
  • 2 gallons of gas.

So, Amp Hour tracking tells you the 'fuel level' in the pack, fairly well. But, it does not tell you range. You have to estimate range, based upon understanding how far the pack takes you if its full:

• If you have 2 Ah left, 20%, and the full pack can take you 20 miles, then your range remaining is, very roughly, 20% of 20 miles, 0.2*20 = 4 miles left.

Or you can use a bit more ease math to do that a little better, if you use the Watt Hour function:

• Calculate your energy usage of the bike. After a ride, how many miles did you go? How many Wh did you use?
• Divide (Watt Hours Used) / (Miles traveled). This is your bike's efficiency, in Wh/Mile.
  • Like MPG for a car.
• Do same as above, but using Wh instead of Ah.

This is only a little better, mostly if you are running the pack real low. Remember, I said the analogy to a car is imperfect. Here's why. Voltage drops as the pack empties. So, it's like you start with high energy fuel (the nitro) but as the pack empties, the voltage drops. So by the end you are running lower voltage, or weaker fuel. You don't go as far for each Ah (or gallon) used.

If you track Wh instead of Ah, the above is factored in, so you get more precise information.

Whew, that was longer than I thought it would be, hope it helps.

[Fred]

I like the analogy of voltage drop being akin to going from high octane fuel to lower octane.

[Clem]

I must say thank you to you all, thank you for taking the time to help and sharing your knowledge with me . I will say I still have to digest all of it and probably will attempt to contact Bat-man and download the software to get W/hours which seems to be missing off my bat-man. Thanks again and best regards Clem