Ebike battery voltage or controller issue?

Hi there,

I've recently finished building my 13s 3p battery with Samsung 25r 18650 batteries, which has left me with a voltage of around 45v when charged,

When first built I managed to ride 200m down the road, before it all suddenly went black...

I returned home and put the battery on charge, the controls would then work when on charge, motor would operate etc. But as soon as I took it off charge it would die after a couple of seconds...

I'm sure this is a voltage cut off issue with the controller I'm using, but I can't figure out exactly why as my controller is 36/48v 20a, my bms is rated at 60a, so is it that the 45v my battery is at is just enough to trick the controller into thinking I have a 48v battery on low power? But not low enough for the 36v limits?

Any ideas would be greatly appreciated!I have been considering buying a 36v controller but don't feel like wasting any more money if I can help it!

Many thanks

Your battery is the issue, not the controller. A 48V nominal battery should read ~54.6V when fully charged. Less than 54V indicates a potential problem.

Have you left your battery on charge for at least 24 hours to let the BMS balance the pack sufficiently since building it? If not, do so. Otherwise, it’s time to start investigating what the BMS is seeing at the sense wires.

Dan

EDIT: Before doing anything drastic, you should also confirm the voltage of your charger. This should similarly read ~54.6V.

Edited May 16, 20223 yr by danielrlee

Thanks for the fast response!

I actually miscalculated the battery configuration to begin with as the nominal voltage of my cells was 3.6v and not 3.7 that I had used to work out my final pack voltage... (I know...rookie! )

So I actually fully charged all cells seperately before welding, tested all points meticulously to ensure the voltage was constant, the overall voltage was 54. 6v when the pack was complete.

I then rode it for up the road, it cut out. It will only charge to 45.5v now.. I'm a little concerned I have damaged the pack in some way, as you say it is the root cause, I will try to charge for a whole day and see if I get anywhere!

Although one thing to mention, I am using a58.8v charger... (I hoped I could get away with this as long as I checked the voltage whilst charging...) will this be an issue still?

Many thanks!

First of all physically check with a reading the chargers out put voltage at the charge connection, the voltage pot could be set low and need adjusting to the correct voltage of 54.6v.

The 58.v charger is incorrect voltage so one needs to either reduce the voltage or get a correct charger. What will occur is the first cell group to reach max voltage of 4.2v (often #1 or the last one wil cease any further charge so battery will end up un- balanced.

Edited May 16, 20223 yr by Nealh

Thanks for the fast response!

 

I actually miscalculated the battery configuration to begin with as the nominal voltage of my cells was 3.6v and not 3.7 that I had used to work out my final pack voltage... (I know...rookie! )

So I actually fully charged all cells seperately before welding, tested all points meticulously to ensure the voltage was constant, the overall voltage was 54. 6v when the pack was complete.

I then rode it for up the road, it cut out. It will only charge to 45.5v now.. I'm a little concerned I have damaged the pack in some way, as you say it is the root cause, I will try to charge for a whole day and see if I get anywhere!

Although one thing to mention, I am using a58.8v charger... (I hoped I could get away with this as long as I checked the voltage whilst charging...) will this be an issue still?

 

Many thanks!

45.5v suggests possibly massive un-balance of the cell groups, one will have to manually check all 13 cell groups for balance then re-balance if needed and then only charge with a 13s charger not a 14s one.

they used the wrong charger with to much voltage and then this happened.

https://www.youtube.com/watch?v=WdDi1haA71Q:383

If the 14s charger has a voltage pot and it can be turned down to 54.6v then one can manually rebalance any wayward cells and then use the charger as normal.

I perodically sheck my charger output to ensure it is correct and hasn't wandered.

My eBike (48V, 15A) turns off after about 300 meters of riding, and I can only turn it on again after a hard reset (turning the battery Off-On using a key). I decided to measure the voltage on the battery and saw 72 volts.

Can you help me figure out what's going on?

check your multimeter first. Make sure it is on DCV and not AC.

If the LCD is off when the bike stops then it's a battery fault. Otherwise, the fault is elsewhere: controller or sensor or cables.

My eBike (48V, 15A) turns off after about 300 meters of riding, and I can only turn it on again after a hard reset (turning the battery Off-On using a key). I decided to measure the voltage on the battery and saw 72 volts.

 

Can you help me figure out what's going on?

The battery in your voltmeter needs replacing. Put a new one one in, then measure again to see that your battery is knackered.

The battery in your voltmeter needs replacing. Put a new one one in, then measure again to see that your battery is knackered.

You're correct. After I replaced the batteries in the voltmeter, the voltage on the eBike battery showed 51 volts. However, this doesn't solve the issue I described above

You're correct. After I replaced the batteries in the voltmeter, the voltage on the eBike battery showed 51 volts. However, this doesn't solve the issue I described above

A 48v battery, should be over 54v when it's fully charged. That's the first thing you need to check.

51v for a 48v nominal battery isn't good if that is full charge voltage, either the balance is well out of whack or you have a bad /duff cell group.

The reason for the bike cutting out after 300yds is the battery is very sick and needs recycling, the cutting out is severe voltage sag/collapse or a bad cell group that sits at a very low voltage.

Any battery is only as good as the worst performing cell group as it is this group that will fail first no matter how well the others are.

The anology is as d8veh usually puts it , imagine each cell group is a pail of water and you have 13 pails. Each pail represents the capacity like a battery cell group , one pail has a hole at the bottom so the water drips out leaving the water level very low . When empty or near empty the system is dead and conks out, even with the other pails still full the one pail has no capacity and is the weak link.

Edited November 20, 20232 yr by Nealh