Is there a budget cycle analyst

[steve marino]

I have a low end eBike that I really like, but it has one of those 5 red LED readouts for the battery's state of affairs. It's better than nothing, but just barely. I don't need a fancy Cycle Analyst because I'm not interested in real time constant power usage, but WOULD like to know the battery's actual power status. Is there anything on the market that would do that? Just an analog (preferably) or digital gauge that gave me an idea of how much power I had left at the end of a ride? Something simple like a gas gauge on a car. I know the analogy isn't the same, in a car w/ an ICE you have as much engine power with a full tank as w/ a quarter, but something along that line.

 

[Lightning P38]

I have a low end eBike that I really like, but it has one of those 5 red LED readouts for the battery's state of affairs. It's better than nothing, but just barely. I don't need a fancy Cycle Analyst because I'm not interested in real time constant power usage, but WOULD like to know the battery's actual power status. Is there anything on the market that would do that? Just an analog (preferably) or digital gauge that gave me an idea of how much power I had left at the end of a ride? Something simple like a gas gauge on a car. I know the analogy isn't the same, in a car w/ an ICE you have as much engine power with a full tank as w/ a quarter, but something along that line.

Get a volt meter and you can get an exact readout. it is your fuel gauge!

I have a 36 volt li-on battery system. At full charge the volts read 42. At 0 charge the volts read 30. So at the end of a ride, if I have 36 volts, I know the battery is 50% charged. If I have 39 volts the battery is 75% charged.

Also, it seems you can get more charge cycles from a battery if you store the battery at 80% charge instead of fully charged. So after a ride I check the volts and make a mental note of how much charge time needed for the next ride, and wait until the the day of the ride to charge it up.

I know how long it takes to increase the voltage by two volts, so I can plan out the needed charge time. It takes about an hour to charge up to 100% from 80%. From 60%, about 2 hrs, etc. I need to write down the times so I have a better record of charge times.

 

[harryS]

How about this?

Electric Bike Scooter Digital LED Voltmeter Voltage Display Gauge Meter Durable | eBay

Find great deals for Electric Bike Scooter Digital LED Voltmeter Voltage Display Gauge Meter Durable. Shop with confidence on eBay!

www.ebay.com

For $7.50, it might not be bright enough to see in daylight, and maybe it jumps so fast you can't read it. Most likely, it will be off on calibration. And maybe it will run the bike down if you don't turn off the battery, Who knows. I ordered one. It looks cool.

 

[JuicePower]

I have a low end eBike that I really like, but it has one of those 5 red LED readouts for the battery's state of affairs. It's better than nothing, but just barely. I don't need a fancy Cycle Analyst because I'm not interested in real time constant power usage, but WOULD like to know the battery's actual power status. Is there anything on the market that would do that? Just an analog (preferably) or digital gauge that gave me an idea of how much power I had left at the end of a ride? Something simple like a gas gauge on a car. I know the analogy isn't the same, in a car w/ an ICE you have as much engine power with a full tank as w/ a quarter, but something along that line.

Do you want a display on your bike? If not just a volt meter from Radio Shack or HarborFreight will work on battery terminals.

 

[steve marino]

Thanks Harry and JP. I have a volt/ohm meter, but it's one of those Harbor Freight multi meters and quite large, for a bike anyway. Not sure if it could hold up to road shocks either. A lot of our roads in Tucson are nothing but solid patches over patches! I'm also going to order that $7.50 volt meter Harry unless I can find a US made one at an auto parts store, assuming that auto parts store are considered essential businesses and are still operating.

Analog w/ a black dial on a white face would be perfect. If I wire it right, no worries on running down the battery, as mine turns itself off after a few minutes if it's left on w/ no activity. You wonder why they don't do something similar w/ auto headlights?

This looks promising. Would just have to make a clear waterproof housing for it, maybe out of a Tupperware type container, or cruise the Dollar Tree stores for a flashlight, cut it down, and stuff the meter inside the light end of the flashlight.

AC 0-50V Round Analog Voltmeter Voltage Panel Meter Dia. 66.4mm DH52 | eBay

Accuracy :Class 2.5.

www.ebay.com

 

[steve marino]

On a separate note, does anyone know how lithium batteries discharge? On my old film cameras that had mercury batteries, those would maintain full voltage until they were way down, then suddenly drop. This was great, as your light meter would be accurate up to the point when the battery suddenly died. When they stopped making the mercury batteries, the silver oxide replacements would slowly drop voltage over time, so your camera's light meter would progressively get more and more inaccurate and you wouldn't know it until you developed the film. How do lithium batteries discharge?

 

[harryS]

Here's a discharge curve for a 36V10AH made with the 26F, typical of the better cells used in Chinese batteries. This would be a 40 cell pack, with 10 series group, each group having 4 cells in parallel (10S-4P).

It comes off the charger at 42.0volts, but as soon as you put an ebike type of load (8 amps) on it, you see the voltage drop down to 40-41V. You'll see the voltage swing 6 volts lower down to 34 V when it's used up.

 

[Lightning P38]

Here's a discharge curve for a 36V10AH made with the 26F, typical of the better cells used in Chinese batteries. This would be a 40 cell pack, with 10 series group, each group having 4 cells in parallel (10S-4P).

It comes off the charger at 42.0volts, but as soon as you put an ebike type of load (8 amps) on it, you see the voltage drop down to 40-41V. You'll see the voltage swing 6 volts lower down to 34 V when it's used up.

View attachment 48834

What does the yellow line mean vs. the blue line? Thx.

 

[ruffruff]

What does the yellow line mean vs. the blue line? Thx.

8amp load VS 12amp load

 

[harryS]

A 6A load is probably more typical. Well, it doesn't matter what load, the shape of the curve is the same. At a lower current, you'll start a little closer toward 42V at the start, so the useable swing is a little larger, closer to 7 volts.

With a 48V battery, you start around 53 volts and drop to 44V, for a 9 volt swing.

The above voltmeter probably isn't damped, like voltmeter displays on a decent E-bike screen. We'll probably see 4 volts of jitter on the display as the motor accelerates.

 

[JuicePower]

A 6A load is probably more typical. Well, it doesn't matter what load, the shape of the curve is the same. At a lower current, you'll start a little closer toward 42V at the start, so the useable swing is a little larger, closer to 7 volts.

With a 48V battery, you start around 53 volts and drop to 44V, for a 9 volt swing.

The above voltmeter probably isn't damped, like voltmeter displays on a decent E-bike screen. We'll probably see 4 volts of jitter on the display as the motor accelerates.

What is the presenting problem? Running out of power boost? Range?

I bought a second battery pack and in the middle of my route, I swap batteries.

On one hand I a addicted to technology and other times reject it. I have owned 16 new large sailboats and some I loaded up all the instrumentation and others none. Boat instruments cost as much as a organic bike per each.

I ration power on windy days where my routes are 40 mile range.

 

[harryS]

What is the presenting problem? Running out of power boost?

No problem here. Just providibg some answers. My ebikes use LCD3 displays, which can show voltage. If it;s down to nominal volatge, I know I had better be on my way home or carrying a spare.

Still that little handlebar meter looks cool, so I ordered one..

 

[tomjasz]

I use a wattmeter like the Turnigy for the first few rides on a new build. I quickly get a feel for how the battery will perform.
These meters are not waterproof but also very useful to sort battery issues and then it's back in the tool box.

 

[steve marino]

Wow, great info here. Thanks everyone. I like the chart Harry posted showing battery discharge rates.

 

[harryS]

Came from China in 15 days. Add two days in quarantine and then I opened it up. In bright sunlight, it will need a cardboard sunshade, but in the shade, it's nice looking. Voltage will drop as the bike pull current, but in idle, it gives a stable voltage.

 

[Sierratim]

Thanks Harry and JP. I have a volt/ohm meter, but it's one of those Harbor Freight multi meters and quite large, for a bike anyway. Not sure if it could hold up to road shocks either. A lot of our roads in Tucson are nothing but solid patches over patches! I'm also going to order that $7.50 volt meter Harry unless I can find a US made one at an auto parts store, assuming that auto parts store are considered essential businesses and are still operating.

Analog w/ a black dial on a white face would be perfect. If I wire it right, no worries on running down the battery, as mine turns itself off after a few minutes if it's left on w/ no activity. You wonder why they don't do something similar w/ auto headlights?

This looks promising. Would just have to make a clear waterproof housing for it, maybe out of a Tupperware type container, or cruise the Dollar Tree stores for a flashlight, cut it down, and stuff the meter inside the light end of the flashlight.

AC 0-50V Round Analog Voltmeter Voltage Panel Meter Dia. 66.4mm DH52 | eBay

Accuracy :Class 2.5.

www.ebay.com

The analog meters are great, but they'll be quite a bit needle bounce riding on anything other than smooth pavement. Digital is probably better for a bike mounted meter.

 

[Sierratim]

I use a wattmeter like the Turnigy for the first few rides on a new build. I quickly get a feel for how the battery will perform.
These meters are not waterproof but also very useful to sort battery issues and then it's back in the tool box.

I installed a Watts Up meter; (Link Removed - No Longer Exists) on an ebike conversion i did maybe 9 years ago. The battery voltage provided an accurate gauge of remaining capacity as noted in other posts. The power readings gave good feedback on how fast I was drawing down the battery in a real time sense. Not as good as the Cycle Analyst, but much cheaper. Worked well for some years. I retired this bike a couple of years ago when the battery started losing too much capacity.

 

[harryS]

I also use the Tenergy/Watts-Up meters. Mine must be a copy of a copy, typical of China gear. They only cost about $10 on ebay, And typical of chinese electronics, they're amazing but they break if you look at them too hard. If you get one that works, it;s handy.

Never rode with one placed so I could see it. It was always down by the battery, and I'd check it for the AH used after the ride.

I put the above meter on a bike that didn't have a voltage readout. Nothing new. I see about a volt sag on the 36V pack at any given level when the motor runs at a cruise. I put a cardboard sun shield around it, so it's easily seen. Maybe some day, I'll learn how to 3D print and make a nice sun shade,

 

[tomjasz]

What is the presenting problem? Running out of power boost? Range?

I bought a second battery pack and in the middle of my route, I swap batteries.

It's nice to have useful data on battery function. A BT BMS is a perfect answer. But I have several batteries that aren't BT enabled and use a switch and cheap digital meter on one build. Both batteries are mounted and just flip the switch to change batteries.

 

[JuicePower]

It's nice to have useful data on battery function. A BT BMS is a perfect answer. But I have several batteries that aren't BT enabled and use a switch and cheap digital meter on one build. Both batteries are mounted and just flip the switch to change batteries.
View attachment 50339

Since you wired in a gauge, do you also wire in running lights?