Bike cutting out when battery on 3 bars

[bikemerchant]

I bought this custom made bike 2 days ago
https://www.adverts.ie/other-sports-...nches/25432673

Was close to fully charged, worked well day 1.
Charged for a few hours and today after about 8km it cut out, just after a stop at a shop.

The battery was showing 3 of 4 bars but the voltage started dropping quickly towards zero, it said something like controller/motor error (I can’t exactly remember) and shut itself off.

I stopped, slipped the battery out and back in and the screen would work again, showing 3 of 4 bars. It worked for less than a minute before the screen shutting off again (no error message from here on, just shut straight off).

Repeated this multiple times – it would shut off once the output reached roughly 700w each time.
No noticeable damage to any cables and it has not been exposed to water since I got it.

Charged it fully and no issue on first test - although I expect the same once i drain 20% or so of the battery.
The seller seems genuine, isn't ducking any questions now but can't troubleshoot it.

Can anybody help me?
Feeling pretty down after my new purchase

Advanced settings are:
Lim: 72kmh, DIM 29inches, UNT:0, P1-46, P2-0, P3-0, P4-0, P5-15, C1-2, C2-0, C3-5, C4-0, C5-10, C6-1, C7-1, C8-0, C9-0, C10-N, C11-0, C12-2, C13-5, C14-3, L1-0, L2-0, L3-1, L4-5.

 

[soundwave]

sounds like the batt has had it and cant supply the voltage needed under load and cuts off.

well used batts suffer from voltage sag at the end of there life when there is not much capacity left in the cell and any load pulls the voltage down.

cheap packs from china will also suffer from this as lie about the capacity.

 

[bikemerchant]

Thanks for the quick response!

Both the battery and controller were showing at least 3 of 4 bars before each shutdown though, so I imagine this would indicate the battery was not actually low enough to shut off?

It was showing 49.1V without any power and was shutting off when it dropped to 46V or so (is only supposed to shut off at 40V). Could it be giving a false reading of remaining battery life?

 

[soundwave]

when there is no load the voltage will shoot back up it cuts out because the voltage drops to low for the controller to stay on.

how many miles has it done and was the batt brand new? as nothing about this in the listing which is strange.

 

[Sturmey]

Hi. Some points that might help.
That's a big battery (20ah) so it could take more than 'a few hours' and up to 10 hours to fully charge if you have a 2 amp charger.(for example) If your battery is worn, there is a few settings that may help for the time being.
The first thing I note is that your P3=0, so you have a 'voltage' or speed throttle and this can pull full current (30 amps in your case) until your set or throttle speed is reached. (This 30amp surge can be irrespective of PAS level with a voltage throttle/PAS). I would be inclined to change to P3=1, so you have a 'current' or torque simulation throttle/Pas levels and this will help eliminate surges of current, especially if you use the lower PAS levels.
An alternative option (if the above doesn't work on your controller) would be to reduce the overall controller current by setting say C5=7 or less. The lowest value is C5=3 which will half your controller current.(You may need to look up the KT LCD8 manual).

 

[Benjahmin]

In the advert it states that the controller is 30A. It does not state what the maximum current delivery of the battery is. It needs to be a MINIMUM of 30A as a maximum rating, preferably more.
The symptoms you describe sound like the battery is either not capable of delivering the amperage being called for or, it is at the end of it's life.
Being a 1000w motor it is probably direct drive rather than geared. DD motors are very heavy on batteries. They are very inefficient at low speeds (so when climbing hills) and pull a lot of power in stop start riding. Best used at high speed on the flat.
So, what is the age of the battery? What make/model number cells are in it?
3 out of 4 bars tells you nothing. What voltage is the battery when just charged?

 

[Nealh]

You have had the answers already, the battery is either knackered or or it can't deliver the current the controller asks for.

3of 4 bars isn't nearly fully charged it is about 60/70%, anything less then 54v fully charged needs investigating.

If knackered a battery will still charge to 54.6v, if it doesn't reach even 54v then it is knackered or has a bad cell group which will pull the voltage down. It only needs one of the 13 cell groups to hit 40v/lvc first for it to cut out.

If the battery isn't able to deliver at least 35a continuous then it is no good for a 30a controller, ideally for 30a you will want 40 or 45a continuous discharge from the battery to allow for voltage sag and not to stress the cells.

If this is a used bike it probably was sold because the seller new the battery is poor.

For this bike a battery will be upwards of £500 to have decent cells capable of 40a continuous.

 

[Nealh]

At 700w the current draw will cause severe voltage sag, either the cells aren't capable of 30a continuous or the battery is knackered.
Check the charger make sure it outputs 54.6v, if so charge the battery till the green light comes on then check the battery voltage. Let us know both voltages.

I would suspect the battery isn't up to supplying the current needed, but with no battery specs other the 48v 20ah we have little else to go on.

C5 is your only answer reduce the parameter by the value of 1 each time and ride it till it stops cutting out, if it stops cutting out tell us the C5 value and that will give an idea of the batteries actual capability.
Or a link if possible to the actual battery fitted, may be ask the seller.

 

[bikemerchant]

sounds like the batt has had it and cant supply the voltage needed under load and cuts off.

well used batts suffer from voltage sag at the end of there life when there is not much capacity left in the cell and any load pulls the voltage down.

cheap packs from china will also suffer from this as lie about the capacity.

It has done just under 1500km. Seller said battery was bought 9 months ago,

In the advert it states that the controller is 30A. It does not state what the maximum current delivery of the battery is. It needs to be a MINIMUM of 30A as a maximum rating, preferably more.
The symptoms you describe sound like the battery is either not capable of delivering the amperage being called for or, it is at the end of it's life.
Being a 1000w motor it is probably direct drive rather than geared. DD motors are very heavy on batteries. They are very inefficient at low speeds (so when climbing hills) and pull a lot of power in stop start riding. Best used at high speed on the flat.
So, what is the age of the battery? What make/model number cells are in it?
3 out of 4 bars tells you nothing. What voltage is the battery when just charged?

9 months old. Seller said it's Samsung inr18650 35e, 3400mha.
I'm waiting on a response from him about maximum current delivery of battery.
Battery was 53.1V just after being fully charged.
I rode it for 400m, let it rest for 20 mins and then it read 52.5V, unsure if this indicates a poor battery?
You would just rely on Voltage to figure how much battery is left rather than the battery bar reader?

At 700w the current draw will cause severe voltage sag, either the cells aren't capable of 30a continuous or the battery is knackered.
Check the charger make sure it outputs 54.6v, if so charge the battery till the green light comes on then check the battery voltage. Let us know both voltages.

I would suspect the battery isn't up to supplying the current needed, but with no battery specs other the 48v 20ah we have little else to go on.

C5 is your only answer reduce the parameter by the value of 1 each time and ride it till it stops cutting out, if it stops cutting out tell us the C5 value and that will give an idea of the batteries actual capability.
Or a link if possible to the actual battery fitted, may be ask the seller.

What do you mean both voltages? How do I check the charger outputs 54.6V? When the charger light went green the bike screen read 53.1V.

 

[wheeliepete]

What do you mean both voltages? How do I check the charger outputs 54.6V? When the charger light went green the bike screen read 53.1V.

53.1v is low for a fully charged 48v battery, which could mean it's out of balance. You need a multi meter to read the charger and battery voltage, essential bit of kit for an ebike owner.

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[Nealh]

With a meter as WP has linked to, plug the charger into the wall socket and turn it on.
Set the meter dial to 200v DC and take a voltage reading from the charger leads end connector, it should read 54.6v.

The battery at 53.1v is not good and indicates a battery poorly balanced or one that is not in tip top condition. The only way to know which it is, is to open it and take 13 voltage readings from the cell pack. The battery has 13 cell groups that make up the 48v nominal voltage.

A 20ah battery is circa 20.4ah using Sam 35e so means it has 6 cells in parallel for each of the 13 cell groups, so in all 78 cells. 35e is a mediocre 8a rated high capacity cell, though ideally any cell is best kept to about 60% of it's current rating for it not to suffer damage. The 35e at 30a discharge should just cope but it is possible that it may have suffered some damage if they have at all, over heated or come close to it.

35e would not be my battery of choice for a 30a discharge with only 6 cells in parallel. It is a very good choice for lower power stuff and I believe is was a battery of choice chosen by NASA for there space probes etc for the good long life and capacity as very low power usage.

 

[Nealh]

Battery bars as a gauge are very unreliable to use as a fuel gauge, voltage is much better but best of all is a watt meter as it will use watt hours as a gauge. A 20.4ah 48v battery will be 980wh.

 

[Benjahmin]

You definitely need a meter, they're not expensive.
As Nealh has said, the output from the charger should be a minimum of 54.6v, possibly slightly more.
A fully charged 48v battery should be 54.6, possibly slightly less, but no less than 54.5 if in good condition. Measure at battery output terminals when disconnected from the bike.
If it is only 9 months old it may have been damaged by too high a current draw, or it may be out of balance through lack of use or poor charging.
As said earlier, this is a high power, low efficiency set up. You can't throw just any 48v battery on it and expect it to work well - for long.
I'm starting to suspect that this is what the previous owner/builder found and is the reason it was sold on.

 

[bikemerchant]

Thanks guys, I will try all you have so kindly advised
Will this multimeter do the job?

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[bikemerchant]

Multimeter gave a reading of 52.9 when fully charged.
I screwed open the battery case but now it seems that if I open the taping keeping the cells together to test them, it will be very difficult for a novice like myself to put it back together?

 

[trevor brooker]

Multimeter gave a reading of 52.9 when fully charged.
I screwed open the battery case but now it seems that if I open the taping keeping the cells together to test them, it will be very difficult for a novice like myself to put it back together?

Have a look at my posts to see the advice I received.
https://www.pedelecs.co.uk/forum/threads/intermittent-fault-on-battery-causing-loss-of-power.35875/

 

[bikemerchant]

The only way to know which it is, is to open it and take 13 voltage readings from the cell pack.

Could anyone link a video showing how to do this?

 

[Benjahmin]

You'll have to put up a photo of what you see when you take the lid off the case.

 

[Nealh]

Batteries differ some are easier to open then others and inside some have extra insulation layers as well. For cell measuring one only has to expose the BMS with the multi connector on the end to get at the pins outs for measuring, at this stage there is no need for anything drastic.
As Benjamin has mentioned take pics and we can guide you with easy to follow advice, all that is needed is a multimeter and sometimes a pair of needles or a pair of PCB strip pins for easier probing.

 

[bikemerchant]

Thanks!
Here they are
The white bit on the side is what a guy on youtube seemed to test, but it's glued to the rest and I don't want to break anything.

Also I have used the bike from fully charged a couple times since and noticed it breaks down once the voltage drops below 44.0V (the voltage parked could be over 50.0 but once the load increases to drive it drops. I managed the load output today to keep it over 44.0 at all times and it didn't crash. No idea what this could suggest (I put C12 down to 1 which apparently should only cut the battery out when it hits 39.0, unless the BMS overrides this)