Hello, I recently bought a folding E Bike with a 48v, 13Ah Silverfish type battery, Bike is less than a year old, 600km in total. The problem is that the battery level on the Display and on the Battery itself shows it is fully charged, but when I check the battery with a Multi Metre, it only shows 38.6 volts. The Charger output shows 53.3 volts on the Multi Metre. Could I have been given a 36v battery passed off as a 48v?
Battery Undercharge?
- Thread starter Ballina
- Start date
docw009
1 MW
I suppose you checked the battery removed from the ebike, because the output terminals are on the bottom. You had to turn the keyswitch on the battery off to remove it from the bike too. Did you turn it back on to measure the voltage?
The operational voltage of a 48V Silverfish is 54.6V at max charge, and the bike usually shuts it off around 41-42V, The battery itself shuts off around 40V if it is balanced,
The operational voltage of a 48V Silverfish is 54.6V at max charge, and the bike usually shuts it off around 41-42V, The battery itself shuts off around 40V if it is balanced,
Does the system operate correctly? Or does it not operate the motor? Have greatly lessened range? Etc?
The charger light usually comes on whenever the BMS of the pack turns the charge port off, which is often but not always when the pack is full.
That happens whenever any cell reaches HVC, so if you have problematic cells or groups that have less capacity than others, they fill up before the rest and the BMS turns off the input, so the charger thinks the pack is full and turns off.
Assuming the BMS has a balancing function (they don't all) then if you leave the charger connected, then after some time (minutes to hours) it will turn back on once the BMS has drained down the highest cell(s) a bit, allowing the charger to fill the other cells a bit more.
The process will repeat over time, until eventually they are all the same voltage (balanced). This doesn't actually fix anything becuase the low-capacity cells are stlll the same lower capacity than the rest, but it lets you use a bit more of the pack's capacity than otherwise at the beginning of such a problem, though as time goes on the problem gets worse and worse until it can take days or more (weeks in some cases for large capacity packs) to rebalance the pack to "finish" charging.
If your pack's BMS has no balancing function, then no matter how long you leave it connected, it won't charge further (unless some of the cells are so bad that they are leaking internally, draining charge off as heat constantly).
If the voltage you read on the pack is actually correct, then why your display shows a higher voltage I don't know, unless it has accidentally been recalibrated to see the low voltage as the higher voltage it shows you. (there's a post in another thread where someone did that).
But it is also possible that the low reading on the battery itself is that the BMS has turned off it's output (or whichever port you're measuring at), and you are only seeing a ghost voltage there, which if you place a load on it would disappear down to zero volts.
The charger light usually comes on whenever the BMS of the pack turns the charge port off, which is often but not always when the pack is full.
That happens whenever any cell reaches HVC, so if you have problematic cells or groups that have less capacity than others, they fill up before the rest and the BMS turns off the input, so the charger thinks the pack is full and turns off.
Assuming the BMS has a balancing function (they don't all) then if you leave the charger connected, then after some time (minutes to hours) it will turn back on once the BMS has drained down the highest cell(s) a bit, allowing the charger to fill the other cells a bit more.
The process will repeat over time, until eventually they are all the same voltage (balanced). This doesn't actually fix anything becuase the low-capacity cells are stlll the same lower capacity than the rest, but it lets you use a bit more of the pack's capacity than otherwise at the beginning of such a problem, though as time goes on the problem gets worse and worse until it can take days or more (weeks in some cases for large capacity packs) to rebalance the pack to "finish" charging.
If your pack's BMS has no balancing function, then no matter how long you leave it connected, it won't charge further (unless some of the cells are so bad that they are leaking internally, draining charge off as heat constantly).
If the voltage you read on the pack is actually correct, then why your display shows a higher voltage I don't know, unless it has accidentally been recalibrated to see the low voltage as the higher voltage it shows you. (there's a post in another thread where someone did that).
But it is also possible that the low reading on the battery itself is that the BMS has turned off it's output (or whichever port you're measuring at), and you are only seeing a ghost voltage there, which if you place a load on it would disappear down to zero volts.
Thank you for your reply. I only bought the bike a month ago and havent been able to test its range properly yet as we have had a few weeks of very heavy rain. The farthest I have gone is 18km and it was after that , that I decided to test how much charge I had used. It was down to 34v from full. I assumed full for a 48v would be around 52-53volts. Then I fully charged it again and tested it, and it only came up to 38.6v. Display showed it was full at that??
Well, if you don't know if the bike is working or not now, or if it will run the motor, etc., then you'll have to test it to see if it still works.
Then start testing the mentioned things to see which if any is causing the wrong voltage reading, if that's what it is, or if it really is reading that then open up the pack and measure all the cell groups. (there are plenty of battery pack troubleshooting and testing threads over the years that go thru this, though it will take a while of poking around to find them until the new forum search is fixed up).
Then start testing the mentioned things to see which if any is causing the wrong voltage reading, if that's what it is, or if it really is reading that then open up the pack and measure all the cell groups. (there are plenty of battery pack troubleshooting and testing threads over the years that go thru this, though it will take a while of poking around to find them until the new forum search is fixed up).
