Learning Curve
1 W
Hey folks, I am having a problem charging my battery and really need some help figuring out what could be wrong.
I have a Brand name electric bike with a lithium ion 48 volt, 15 amp hour battery that I bought new just over 3 years ago. I live in a rural area, and don’t go out much, but I rely on my bike to get into the nearest town every week or 2. The ride is 10 hilly miles in and back. I haven't put this battery through more than 150 charge cycles, and many of them were not bringing the battery to full charge... and I really did everything I could to optimize it's life span...
I usually only charge it to approximately 90% full just before I am about to go to town, and leave it at about 50 - 60% when it will be sitting a week or two, until charging it up for the next trip. For the first 2 and a ½ years, charging it after the 10 mile trip and sitting for a week, took about 3 hours. This year it seemed to maybe have a tiny bit less power than it did the first couple years, but still takes me the 10 hilly miles into town and back, with power to spare. Over the past 6 months it seemed it was maybe taking a bit less time to charge then it used to and had a bit less power. But nothing that noticeable.
But then one day, it suddenly charged for less than an hour after the 10 mile ride to town and back. I am not technically competent enough to know how to use a multimeter on this encased battery, so all I have to go on is the 4 battery indicator lights, but the 4 indicator lights have never been accurate and all 4 stay on when the bike is resting even when the bike is only charged to 50 -60%, and only go down to 3 lights when resting when the battery is a couple miles away from empty. (or only 1 flashing indicator light)
I thought maybe it wouldn’t charge because I created an imbalance by never fully discharging the battery, and always recharging, partially or fully after the ride to town and back, which only took it down to approx. 50 to 60%.
So I charged it as long as it would charge after draining it pretty low, down to 2 indicator lights, and it charged for an hour and 3/4. Which was longer than the hour it would charge, before I drained it that low... Then I rode the bike about 12 miles, and at the end of the ride, it quickly went from 2 battery indicator lights to 1 blinking indicator light. So I quickly shut it off, walked it home and recharged it. This time I was able to recharge it for 2 hours, and then it wouldn't charge any more. But it should have taken much longer from as close to completely discharged as it was...
So I contacted the guy who sold me the bike new, who I was told by our local bike shop was authorized to sell and work on that brand of bikes. I brought him my battery and he said he had recently seen several other failed BMS systems of the same brand of bike just in the past couple months, which he thought was odd as he had never seen this before and said the BMS should last the life of the battery. But he thought that was the problem. And he said he could replace the BMS for $250, and though he couldn’t guarantee the remaining battery life, or check the remaining capacity until the battery's BMS was replaced and it could be fully charged, he guessed it was probably still OK and with the replaced BMS it would work just like the original … except the green light I see on the button on the battery when it is on, would no longer light up.
I agreed to this and he did the repair, and then emailed me the battery was fixed, he had replaced the BMS, and the battery tested out at 14.3ah, which he said is a very good result for a 15ah rated battery. Implying he had been able to fully charge the battery after the fix, as he told me he couldn’t check this before the battery was fixed, as it wouldn’t fully charge. He also said the cells were balanced.
I paid him, got back my battery and charger, and today, thinking he sent it back fully charged, I put it in the bike to go for a ride. I wondered as soon as I turned it on because initially the first battery indicator light flashed on and off for a few seconds. The only other time it did this was when I had intentionally discharged the battery to be very low, and the first time I started it after I drained the battery down to one flashing indicator light and then recharged it. I wondered why it would still be doing the same thing if it had a new BMS… ? but then all 4 indicator lights lit up and everything seemed fine the first 1000 feet. Then I started going up a hill, and noticed the battery indicator lights dropped to 3, something it doesn’t normally do on a big hill until I have ridden 5 miles… I thought maybe the guy who repaired it had discharged it a bit- after testing the fully charged battery capacity? But another 200 feet up the hill and the battery indicator dropped to only one flashing light. Like it did when I intentionally ran it right down. The bike still seemed to be running normally, ?( maybe I am not recalling the last few seconds properly ?) but thinking maybe he had given me back a drained but fully repaired battery that just needed to be recharged, I quickly turned my bike off, walked it home, plugged it into the charger, hoping it would charge a few hours and be fine. But instead it charged for two hours, before the light on the charger turned green and it stopped charging. Which is exactly how long it charged after I ran it down to one flashing light, BEFORE the BMS was said to have been replaced, and before my presumably fully charged battery had it’s capacity tested at 14.3 amp hours… Does this even make sense?
The only difference now it is *repaired* is that the light that used to light up the button to turn on the battery, showing it was on, performed as the repair guy said, and it no longer comes on.
I only understand the basics of how batteries and ebikes work.
So… my question is, what might be going on that would account for these problems, and is there anything that matches this description that would persist unchanged after the BMS was replaced and the battery was tested, and found to have plenty of remaining capacity and balanced cells?
Sorry this is so long.. I just need to be sure I understand the range of possible things that might be going on ..?
I have a Brand name electric bike with a lithium ion 48 volt, 15 amp hour battery that I bought new just over 3 years ago. I live in a rural area, and don’t go out much, but I rely on my bike to get into the nearest town every week or 2. The ride is 10 hilly miles in and back. I haven't put this battery through more than 150 charge cycles, and many of them were not bringing the battery to full charge... and I really did everything I could to optimize it's life span...
I usually only charge it to approximately 90% full just before I am about to go to town, and leave it at about 50 - 60% when it will be sitting a week or two, until charging it up for the next trip. For the first 2 and a ½ years, charging it after the 10 mile trip and sitting for a week, took about 3 hours. This year it seemed to maybe have a tiny bit less power than it did the first couple years, but still takes me the 10 hilly miles into town and back, with power to spare. Over the past 6 months it seemed it was maybe taking a bit less time to charge then it used to and had a bit less power. But nothing that noticeable.
But then one day, it suddenly charged for less than an hour after the 10 mile ride to town and back. I am not technically competent enough to know how to use a multimeter on this encased battery, so all I have to go on is the 4 battery indicator lights, but the 4 indicator lights have never been accurate and all 4 stay on when the bike is resting even when the bike is only charged to 50 -60%, and only go down to 3 lights when resting when the battery is a couple miles away from empty. (or only 1 flashing indicator light)
I thought maybe it wouldn’t charge because I created an imbalance by never fully discharging the battery, and always recharging, partially or fully after the ride to town and back, which only took it down to approx. 50 to 60%.
So I charged it as long as it would charge after draining it pretty low, down to 2 indicator lights, and it charged for an hour and 3/4. Which was longer than the hour it would charge, before I drained it that low... Then I rode the bike about 12 miles, and at the end of the ride, it quickly went from 2 battery indicator lights to 1 blinking indicator light. So I quickly shut it off, walked it home and recharged it. This time I was able to recharge it for 2 hours, and then it wouldn't charge any more. But it should have taken much longer from as close to completely discharged as it was...
So I contacted the guy who sold me the bike new, who I was told by our local bike shop was authorized to sell and work on that brand of bikes. I brought him my battery and he said he had recently seen several other failed BMS systems of the same brand of bike just in the past couple months, which he thought was odd as he had never seen this before and said the BMS should last the life of the battery. But he thought that was the problem. And he said he could replace the BMS for $250, and though he couldn’t guarantee the remaining battery life, or check the remaining capacity until the battery's BMS was replaced and it could be fully charged, he guessed it was probably still OK and with the replaced BMS it would work just like the original … except the green light I see on the button on the battery when it is on, would no longer light up.
I agreed to this and he did the repair, and then emailed me the battery was fixed, he had replaced the BMS, and the battery tested out at 14.3ah, which he said is a very good result for a 15ah rated battery. Implying he had been able to fully charge the battery after the fix, as he told me he couldn’t check this before the battery was fixed, as it wouldn’t fully charge. He also said the cells were balanced.
I paid him, got back my battery and charger, and today, thinking he sent it back fully charged, I put it in the bike to go for a ride. I wondered as soon as I turned it on because initially the first battery indicator light flashed on and off for a few seconds. The only other time it did this was when I had intentionally discharged the battery to be very low, and the first time I started it after I drained the battery down to one flashing indicator light and then recharged it. I wondered why it would still be doing the same thing if it had a new BMS… ? but then all 4 indicator lights lit up and everything seemed fine the first 1000 feet. Then I started going up a hill, and noticed the battery indicator lights dropped to 3, something it doesn’t normally do on a big hill until I have ridden 5 miles… I thought maybe the guy who repaired it had discharged it a bit- after testing the fully charged battery capacity? But another 200 feet up the hill and the battery indicator dropped to only one flashing light. Like it did when I intentionally ran it right down. The bike still seemed to be running normally, ?( maybe I am not recalling the last few seconds properly ?) but thinking maybe he had given me back a drained but fully repaired battery that just needed to be recharged, I quickly turned my bike off, walked it home, plugged it into the charger, hoping it would charge a few hours and be fine. But instead it charged for two hours, before the light on the charger turned green and it stopped charging. Which is exactly how long it charged after I ran it down to one flashing light, BEFORE the BMS was said to have been replaced, and before my presumably fully charged battery had it’s capacity tested at 14.3 amp hours… Does this even make sense?
The only difference now it is *repaired* is that the light that used to light up the button to turn on the battery, showing it was on, performed as the repair guy said, and it no longer comes on.
I only understand the basics of how batteries and ebikes work.
So… my question is, what might be going on that would account for these problems, and is there anything that matches this description that would persist unchanged after the BMS was replaced and the battery was tested, and found to have plenty of remaining capacity and balanced cells?
Sorry this is so long.. I just need to be sure I understand the range of possible things that might be going on ..?
As long as it isn't a fire hazard and the indicator lights only go down to one for a few seconds every few miles, I am not sure it matters... esp. now I know the battery isn't actually critically low and in danger of damage if I keep riding.
