17.5 AH "Whale" Power Reading

[JKeating]

We purchased 2 17.5 AH Panasonic batteries earlier this year. We are using them with a Bafang Mid-drive motor. We are unclear about how to read the battery's built in power meter. For example: in the photo, 3 out of 4 lights show green, does this mean that the battery is around 75%?

[max_volt]

It's counter-intuitive but red means good or full. The leds dont change color but are on or off.

[Fred]

IMHO those lights are close to useless. You really need some kind if watt-meter or a Cycle Analyst if you want to measure capacity used. The indicator on the Bafang display may be a little more accurate, but again it is only measuring voltage which will vary depending on load being drawn at the time of reading.

[ykick]

Those lame attempts at crude LED volt meters along with those damn % (percentage) display meters are basically useless. At least until you study, measure and better understand battery voltages by a real and reasonably accurate volt meter.

OP didn't mention voltage of this pack but for example if it's 52V, full hot charge will be somewhere above 58V resting. But the moment you put a load on that it will sag/drop down 2-5V. Remove the load, it'll spring back up to a little less than where it started. Now when that 52V pack is reading about 50V resting, it's damn near empty and you should go very easy on throttle and power demand until it can be recharged.

If 48V pack, the full charge voltage should be above 54V but the same sag/drop principles apply. When 48V pack is around 46V, it's practically empty and you should ride gently until it can be recharged.

So, if you use a volt meter and study the loaded and unloaded results during the discharge curve of a battery pack, those LEDs and sometimes the % meter may then provide some useful tidbits to help approximate SOC (state of charge)? Otherwise, there's little basis for comparison to what they're representing.

[AZguy]

I have done exactly what ykick said.

I've been logging my rides. With a voltmeter I've been measuring start and end voltages and note the number of LED's and bars on the LCD (I also log mi's ridden, moving time, and average speed). I understand the relationship between the LED's on both my 52V and 48V batteries, and LCD bars on the display. With only four LED's - it really is more like three since even when I [very, very infrequently] take a battery to LVCO the last LED is still on so it's sort of meaningless beyond saying the LED voltmeter is "on".

I put a batt-man on a month or so ago and it gives you light-years better information and I now add the readings from it (Ah, Wh) into my logs. I really suggest a device like this. It's not terribly budget-breaking for sure, a little bit of a pain to install, but the information is invaluable - I have a much better idea of SOC just by looking at the Ah and voltage instead of silly little bars (or LED's). it *really* helped me figure out how to tune my PAS parameters in the controller.

[kerrylaw]

I like to know what voltage my batteries are at. Since I run a 52V pack on my fat bike and my DPC-10 display is for a 48V pack, it is inaccurate and pretty much worthless as far as determining my battery voltage. So I installed a small, $2 voltmeter below my display. It is powered by the main battery and activated by a small red momentary switch I installed near my left thumb. I don't want to discharge my pack too low, so I check this often when riding. It works well, as it is nice to know what voltage my battery is at. As I said, the displays "bars" are worthless and with this, I know my battery voltage to the 1/10th. Yea!!







Here is a sample of the "2 wire meters" sold on Ebay that I used. Just $2 -$3. They come in RED, BLUE, GREEN or YELLOW. Just mount the meter somewhere handy like your handle bars or downtube. Connect the meter to your battery via inside the battery cradle. Either wire it directly ( always on when battery is installed) or install a momentary switch somewhere in the circuit like I did. Maybe avoid the battery cradle by just putting a plug on its end, so all you need to do is plug it into the batteries charging port, once the battery is on the bike. ( Unplug to remove the battery. ) Easy-peasy!

[Orrie]

Hello,

I like your idea about the volt meter. Can you provide some details on how you connect it to the battery and a link to which one you used, I would like to try something similar. Thanks

[barber]

Good info.. Thanks
Barber