Following on from my introduction to this forum I have questions

[LesG]

Hi, As I mentioned on my introduction post I live in a hilly area of Lancashire which means that I have to struggle uphill to get home after every cycle trip.
I thought an ebike would solve my problem, but I am having trouble with the batteries.
I bought a 2nd hand Chinese ebike, a Hercules H 580 and got 2 48v batteries with it.
I got no instructions with it and very little help from the seller.
I charged both batteries and they both did about 9 miles on assist the first time I took it out, I didn't really want assist to be on all the time, but apart from turning the "ignition" key off there didn't seem any way of using it without assist.
Yesterday when I took it out the first battery lasted the same amount of time, but the other gave up after a couple of miles.
When I got home I checked the voltage and it showed over 50v so I am confused, I tried it again this morning and it will do literally 5m at most before cutting off.
I could do with as much advice as possible but I know that some of you will think that I bought cheap and you get what you pay for.
Thanks in advance,
Les

 

[cyclebuddy]

Hi Les

When you buy second-hand you really don't know the condition of the battery(ies), so it's best to assume they're toast and factor in the price of a new one.

A quick google suggests your bike is a 26" e-MTB; it has an LCD on the left side which allows you to apply more or less assist. That you only got 9 miles from each 48v 10Ah battery suggests they've been/you've been hammering them pretty hard - likely up the hill you mention in your introduction post?

That you're now measuring 50v on one battery and it's cutting out almost instantly suggests it's knackered (voltage sag). A pedelec is Pedal assist... not a moped. Applying max power up steep hills regularly on a battery with cheap(ish Chinese) cells really will kill it prematurely.

I wonder if you're expecting too much from it?

 

[flecc]

As Cyclebuddy has said, the batteries may well be finished. When new a nominal 48 volt battery should read 56 volts fully charged. Everything you describe indicates the voltage is collapsing early under load, usually meaning the battery cells are failing.

Probably why the seller was getting rid of it, batteries being expensive makes that the most common reason for selling an e-bike.
.

 

[Bikes4two]

Voltage Sag -

• a phenominon of all batteries, new or old, whereby the off-load voltage drops when the battery is put under load (i.e. draws current).
• As a battery ages (through time and/or usage), the voltage sags more dramatically and for instance, in a ebike where the power draw could be considerable, the voltage sags below the safe Low Voltage Cut-off point and the battery's BMS (Battery Management System), switches off power.

Alternatively, poor/corroded connections between the battery and motor will also result in voltage drops so as a first aid measure, check out all power connections but given the history of this bike and it's batteries, the gut feeling is that the batteries are pooped!

 

[saneagle]

I'm wondering if your bike has a fault that's causing it to draw too much current. A dodgy controller or bad connection can do that.

First of all, check that the motor connector is pushed in all the way to the marked line. 1mm short can give the problem you describe. Beyond that, you need to do some more detailed tests with a meter. It might be worth opening up the controller box to check the connections in there in case it has the old style connectors, which can melt.

Did you try riding it on different power levels? What's the result of that? Do both wheels spin freely? Is there something on the LCD that shows how much power you're using and is it behaving as it should?

You have up and down buttons on the LCD to adjust the amount of power you use. Normally, there's level zero, which switches off assistance. Does yours have that?

 

[Deleted member 16246]

Aside from the stated possibilities, a badly out of balance battery can switch off like that when it still has a lot of potential power in it. If one set of parallel cells is at a lower voltage than the rest, it will quickly cause the BMS to shut off. Also, that bank of cells will never get charged up properly, because once the other banks of parallel cells reach the full charge level, the BMS stops charging all the cells.

I have a 36 volt battery which went like that. I had to open the case to measure the voltage of all the groups and found one group at 3.3 volts while all the others were at 4.2volts. I charged it separately with a 4.2v charger and monitor it through some extra contacts on the outside of the case (insulated for safety). I now keep it in balance and the two year old battery is performing great as long as I do this. When it was badly out of balance, the battery would shut off at about 2 miles. Now I can get well over thirty odd with the same effort on the pedals.

I think of the 60 cells in the battery, one has fault which drains the others in its parallel set. When I spot that the bad set is even a little bit lower than the rest (0.6 volts lower than the rest so 4.19 on the whole battery and 4.13 on the bad set, I do a long balance charge . This means leaving the charger plugged in for about 3 hours after the red charging light goes out. This brings all the cell groups into balance. You do need to make sure the set up is supervised though, in case the charger or BMS goes wrong and over charges the setup.

 

[saneagle]

Aside from the stated possibilities, a badly out of balance battery can switch off like that when it still has a lot of potential power in it. If one set of parallel cells is at a lower voltage than the rest, it will quickly cause the BMS to shut off. Also, that bank of cells will never get charged up properly, because once the other banks of parallel cells reach the full charge level, the BMS stops charging all the cells.

I have a 3 volt battery which went like that. I had to open the case to measure the voltage of all the groups and found one group at 3.3 volts while all the others were at 4.2volts. I charged it separately with a 4.2v charger and monitor it through some extra contacts on the outside of the case (insulated for safety). I now keep it in balance and the two year old battery is performing great as long as I do this. When it was badly out of balance, the battery would shut off at about 2 miles. Now I can get well over thirty odd with the same effort on the pedals.

I think of the 60 cells in the battery, one has fault which drains the others in its parallel set.

There are some BMSs that take their power from one cell group, typically the first. They take that power even when you don't use the battery, so if you don't charge the battery for a long time or you don't charge it to full, that cell will go down and down.

 

[WheezyRider]

Aside from the stated possibilities, a badly out of balance battery can switch off like that when it still has a lot of potential power in it. If one set of parallel cells is at a lower voltage than the rest, it will quickly cause the BMS to shut off. Also, that bank of cells will never get charged up properly, because once the other banks of parallel cells reach the full charge level, the BMS stops charging all the cells.

I have a 3 volt battery which went like that. I had to open the case to measure the voltage of all the groups and found one group at 3.3 volts while all the others were at 4.2volts. I charged it separately with a 4.2v charger and monitor it through some extra contacts on the outside of the case (insulated for safety). I now keep it in balance and the two year old battery is performing great as long as I do this. When it was badly out of balance, the battery would shut off at about 2 miles. Now I can get well over thirty odd with the same effort on the pedals.

I think of the 60 cells in the battery, one has fault which drains the others in its parallel set.

Tony, could also be a BMS fault. @Nealh had a batch that would randomly discharge certain banks. Try experimenting with charging the pack up and leaving the BMS detached for a few days and see if the suspect bank keeps its charge or it drops as before.

 

[Deleted member 16246]

Tony, could also be a BMS fault. @Nealh had a batch that would randomly discharge certain banks. Try experimenting with charging the pack up and leaving the BMS detached for a few days and see if the suspect bank keeps its charge or it drops as before.

Thanks. Might try that. To be clear though, if I charge up and balance the whole battery,and then leave it alone for a few days,it seems to remain in balance. If I take it out and give it some stick for a few miles, I tend to find the affected group drops slightly lower, even when measured on arrival home without charging. I tend to think one of the cells is weak in that group. I can live with it for now, and the battery is two years old with about 1500 miles on it. It still has plenty of useful life, albeit that it needs a bit of Hands on to monitor it's balance and correct its foibles...

 

[LesG]

Thank you for all of your replies, Cyclebuddy, I don't think I expect too much as I don't know what to expect at all, I wasn't too sure if this is normal for batteries.
I have been peddling uphill too., not expecting the battery to do all the work and have always used it on level 1

Flecc, Fully charged both batteries read 53v which is obviously down from what you say a new battery should read, it certainly appears that the batteries are not as good as they should be.

bikes4two, the connections do appear to be in good working order no rust or debris on any of the connections.

Saneagle, both wheels turn freely, no brakes binding etc, I have only used it on level 1 as that has always been enough power for the hills when first out, yes the controller has a read out, I have attached 2 photos one showing battery level, power level kph and one other bottom left hand side that I don't know what it means this appeared to work as it should until it cut off unexpectedly it does not have a level 0 no assistance level.
On the other photo in red is I presume the voltage going to the throttle, but as I have mentioned I know nothing of ebikes, maybe I should have done more research....
One more thing, excuse my ignorance, but is the motor controller in the wheel hub, on the handle bars as pictured or the box under the battery housing?

Tony1951, I'm not sure I have the skills for testing in this way unfortunately, I am a little out of the loop for people to turn to in my area for this kind of expertise

Wheezyrider, just to clarify, are you saying to charge the batteries fully, disconnect, leave for a few days then retest?

 

[WheezyRider]

Wheezyrider, just to clarify, are you saying to charge the batteries fully, disconnect, leave for a few days then retest?

No, I was replying to Tony's post about his battery. Sorry if it caused confusion

 

[Deleted member 16246]

No, I was replying to Tony's post about his battery. Sorry if it caused confusion

Probably my fault for divertin Wheezy.

 

[Deleted member 16246]

There are some BMSs that take their power from one cell group, typically the first. They take that power even when you don't use the battery, so if you don't charge the battery for a long time or you don't charge it to full, that cell will go down and down.

I missed that post saneagle. Interesting. I wonder if that is what is going on. Except, thinking about it, the affected group is about no3 of ten. Could still be there the cause though.

 

[saneagle]

I missed that post saneagle. Interesting. I wonder if that is what is going on. Except, thinking about it, the affected group is about no3 of ten. Could still be there the cause though.

Not sure. It's usually the first or last group. In theory, it could be any, but no.3 just seems a bit illogical.

 

[WheezyRider]

I missed that post saneagle. Interesting. I wonder if that is what is going on. Except, thinking about it, the affected group is about no3 of ten. Could still be there the cause though.

The overall current draw of a properly functioning BMS (non-Bluetooth) in standby mode should be micro Amps, so it should take quite some time to drain a bank, even if it is drawing power only from one bank (I am sceptical about this arrangement, seems like very poor design. I also doubt that the voltage from one bank would be sufficient to drive the MOSFETs of the BMS into saturation. This normally needs 5 to 10V to not just switch on power MOSFETs, but also drive them to the point of maximum conduction. It could be that a BMS uses a voltage from the first bank to signal that the sense cables are attached - but this would be an incredibly small current). If you are seeing the effect within a day or so, it should not be caused by a normally functioning BMS.

 

[saneagle]

Another thing it can be is the transistor that switches on the bleed resistor for group 3 is stuck on. You can test that by feeling the bleed resistors. Any that are bleeding will be quite warm or hot. Don't test hot of the charger because that's when they're supposed to be bleeding. Test with a slightly run down battery.

Who remembers those Ping batteries that we used to use that had LEDs on each chanel so that you could see when they were bleeding? Those BMSs were quite popular too, but I can't remember who made them.

 

[zoros]

How much did you pay for the bike?
Z

 

[LesG]

How much did you pay for the bike?
Z

Is this reply aimed at my original post? It seems to have been overtaken with talk of batteries
If so I paid 420 pounds for it, so obviously not expensive in ebike terms, but I think it is still a lot of money

 

[zoros]

You get what you pay for in Ebikes. Anything less than £1500 is not going to cut it. Less than £1000 and your starting to scrape the barrel. Less than £500 - junk, I'm afraid.
Z

 

[Brik]

Is this reply aimed at my original post? It seems to have been overtaken with talk of batteries
If so I paid 420 pounds for it, so obviously not expensive in ebike terms, but I think it is still a lot of money

Are you sure the charger is suitable for the batteries, maybe the first owner had to replace the original charger?