48v battery only lasting about a mile

Danzkieman

New Member
Region
USA
I have a 750 watt ebike powered by btn electic bikes. Currently has 440 miles on it. 48v 12.5Ah battery. When I first got it there was no problem riding full throttle on the way to the store and back (about 4 mile round trip) but over the past few months the range has been dropping now I can hardly get to the gas station with pedal assist without it dying. I measured the voltage at a full charge (52.9v) then rode it until it shut off. Checked the voltage when I got back and it read 52.1v. I researched battery percentages and correlating voltage and found that my battery dies around 84% (52.1v). It seems that it also doesn’t take on a full charge. It makes it to 89%(52.9v) before the charger light turns from red to green indicating a full charge. I don’t know a whole lot about ebikes and batteries as this is my first one but I figured I’d come and ask here for suggestions before I buy a new battery.
 

harryS

Well-Known Member
You probably have an unbalanced battery. One of the cell groups is stuck at partial charge and can't get to full charge. Your one mile ride drains that weak cell group to the minimum, which shuts off the battery.
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You go to recharge, and since the rest of the battery cells are nearly full, the charger shuts off as soon as the good cells reach full charge, which leaves the weak cells starved. Nothing much you can do, except buy a battery with better quality cells.

Some people like to try balance charging, but that's your call.
 

Solarcabin

Well-Known Member
Region
USA
As HarryS said it sounds like your battery has developed a memory in a cell and isn't taking a full charge or discharging fully.

This happens generally when you don't regularly discharge a battery and fully recharge and just use short charging times.

If your ebike battery has a USB port you can try to drain the battery using some other plug in USB device and just let it drain until it shows no bars. It won't hurt the battery and BMS will protect it.

Then completely recharge the battery using the supplied charger and that will usually work to get back the capacity.

If that works then remember to let your battery drain to around 20% when riding and recharge to full at that point and your battery will maintain capacity.

If that doesn't work you will probably need a new battery.
 

Danzkieman

New Member
Region
USA
As HarryS said it sounds like your battery has developed a memory in a cell and isn't taking a full charge or discharging fully.

This happens generally when you don't regularly discharge a battery and fully recharge and just use short charging times.

If your ebike battery has a USB port you can try to drain the battery using some other plug in USB device and just let it drain until it shows no bars. It won't hurt the battery and BMS will protect it.

Then completely recharge the battery using the supplied charger and that will usually work to get back the capacity.

If that works then remember to let your battery drain to around 20% when riding and recharge to full at that point and your battery will maintain capacity.

If that doesn't work you will probably need a new battery.
Yeah that makes sense because I ride it to work and I only live about 1/2 mile away and top up when I get home. My battery doesn’t have a USB port. Is their another way to completely drain the battery?
 

Danzkieman

New Member
Region
USA
Also any suggestions for a quality battery for this bike? I’m not sure how universal the plug in ports are but I have 2 prongs approximately an inch apart
 

Solarcabin

Well-Known Member
Region
USA
Yeah that makes sense because I ride it to work and I only live about 1/2 mile away and top up when I get home. My battery doesn’t have a USB port. Is their another way to completely drain the battery?
Well, not really that I am aware of because it is plugged in to the ebike controller.

let me do a little research and see if some of my battery buddies can help.
 

Solarcabin

Well-Known Member
Region
USA
OK, try this:

Put your battery on your charger and even though it turns green and says full leave it in there for 10-12 hours.

The charger will keep checking the BMS and sending a small charge and over that time the smart BMS if it has one will rebalance the battery.

Now, I recommend you do that outside because it could potentially overcharge a battery with a bad BMS and overheat and start a fire.

If your battery is visibly damaged do not do this,

Then ride your ebike until you drain the battery to vey low and at least 20% and again recharge full and do that when ever you are riding.

Hope that works for you!
 
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JRA

Well-Known Member
Provide a picture of your battery. Most suppliers across the pond have access to a variety of cases it is just luck of the draw if they have one like yours.
 

Danzkieman

New Member
Region
USA
Here she is
image.jpg
image.jpg
image.jpg
 

JRA

Well-Known Member
Send those to herbert@dtbattery and let him know you want a 48v 12.5ah one and see what he says?
 

tomjasz

Well-Known Member
Region
USA
City
Minnesnowta
Yeah that makes sense because I ride it to work and I only live about 1/2 mile away and top up when I get home. My battery doesn’t have a USB port. Is their another way to completely drain the battery?
Lithium ion batteries do NOT have a memory. Period. Advice is being given on cherry picking Google sources. Several MONITORED
8-10 hour charges may balance the pack. BTN uses a featureless BMS. Don’t start doing derp discharges. Doing di can severely damage and create a catastrophic event. Understand some advice given is from sources with only forum reading and Google searching. Some of use have built repaired sold and supported batteries for years. JRA HarryS are trysted sources.
 
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Solarcabin

Well-Known Member
Region
USA
Lithium ion batteries do NOT have a memory. Period.
"The battery appears to remember that you have only taken part of its storage capacity -- and eventually no longer supplies its full energy. Experts refer to this as a "memory effect," which comes about because the working voltage of the battery drops over time because of incomplete charging-discharging cycles."
 
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Solarcabin

Well-Known Member
Region
USA
What an idiot. Its capacity loss. Not memory like old school chemistry. Jeebus. Please…
Anyone fan cherry pick poorly written descriptions. I’m gonna just call you “orange man” from now on.
That description is from the battery experts and scientists and you call it poor?
 
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tomjasz

Well-Known Member
Region
USA
City
Minnesnowta
2013 lots has progressed in nearly a decade. Thats what science does. Learning and advancing.
 
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keithj69

Member
Region
USA
What an idiot a 2013 article. Nothing has been learned since then.
Its capacity loss. Not memory like old school chemistry. Jeebus. Please…
Anyone fan cherry pick poorly old written descriptions. I’m gonna just call you “orange man” from now on.

Warch and read Professor Dahl FFS
"You'll see nothing like it, I have the same memory, the greatest memory. No one knows as much as i do about this. I have forgotten more cells than this battery"
 

keithj69

Member
Region
USA
That description is from the battery experts and scientists and you call it poor?

Just like your knowledge of laws and ebike motors turned out to be crap so is your understanding of ebike batteries.

That is why so many people here have you on ignore.
YOU POSTED A 9 YEAR OLD ARTICLE! Things have advanced quite a bit since that time.