Battery capacity running down

[naughtyus maximus]

Hi to everyone,i'm new to the forum and this is my first post and its a problem post .

I converted a saracen mantra for my partner,. who at 62 had started to struggle with the hills the poor thing.I fitted a voilamart 250w front wheel from ebay and a 36v x-go battery, also from ebay.Putting the whole thing together was fairly simple,and the look on my partners face the first time she tried it out was a joy to behold.She absolutely loved it.She then insisted that i build one for myself as i was literally holding her up .So i converted my own mantra using a voilamart 250/1000w rear wheel and 48v x-go battery,and overall i've been very impressed with it.I've been getting about 24 miles to a full charge using the electric virtually the whole distance whilst pedalling at the same time.However the last three journeys have gotten me only about 15-16 miles.I'm assuming the capacity of some or maybe all of the batteries is getting lower.This is a bit disappointing as its only been charged maybe 60 times or so in the 8 months i've been using it.The battery listing stated it would have a lifespan of 500 charges.I never really believed that but thought i might possibly get a couple of years out of it before i needed to replace it.I've shot a message to the seller (chinese),and surprise surprise got no response.We dont have a great deal of money,hence the reason for converting our existing bikes,and i dont relish the prospect of replacing our batteries every 8 months.So i was toying with the idea of stripping the existing battery and replacing the individual battery cells myself with something that will give a greater lifespan.So,my question is,is it doable.I'm reasonably confident i can do an as was replacement if its simply a matter of de-soldering and re-soldering.Also which batteries would you members recommend that would give a greater lifespan.I'm keen to use the existing battery casing as its the only one i could find to fit my frame.Any advice would be much appreciated thanks.

 

[Flatcap_FPV]

Hi there,

A couple of possibilities to consider before going the whole hog and build an entire new pack:

1. How often do you use the bikes and Cycle the batteries? (no pun intended )
Even though they are rechargeable if they are left for prolonged periods fully charged this shortens the life span of the batteries and isn't good practice. Try giving the pack a conditioning cycle first, that may do the trick!

If you aren't using them for an extended period personally i would say 4 weeks or more (Though other peoples opinion may vary) then you should bring the battery pack down to the correct "storage" voltage.

2. You may have just one (or more) bad cell/s, in which case swapping just the bad cell would be a considerable cost saver compared to building/buying an entire pack.
This is easy to isolate any good/bad cells using a multi-meter after a fresh charge. Any cells that are particularly questionable will be considerably lower voltage than the others.
Always replace like for like capacity and discharge rate of cell.

3. You say it was a cheap Chinese kit... Unfortunately they are never the most reliable for using components that are up to scratch, they often sell products that are over-rated or use cheaper 2nd parts which were rejected at QC from a reputable manufacturer. You may have been lucky with the first kit and not so lucky with the 2nd kit.
Ultimately there is a reason why batteries are so expensive, finding an "allegedly" identical battery half the price of the other is not just retailer price variation. (10-12% price difference maybe)

USB memory sticks are a perfect example, you can buy a cheap 1Tb usb drive for about £20 on ebay, but you can only fit about 10Mb on them because they hack the boot sector so it looks like its a much higher capacity! (in reality a 1Tb usb stick is around the £200+ for a real one)

 

[vfr400]

Conditioning cycles don't work on lithium batteries for Ebikes. There is a possibility that your battery is out of balance. You can check that by measuring the voltage on the terminals or charge port immediately after disconnecting it from the charger. A 36v battery should be 42.0V and a 48v one 54.6V. The further from those voltages, the more out of balance it is. Do the test first, then we can advise how to balance if necessary.

1000w motors will wear out a battery very quickly if the battery is not up to providing the power, which is normally 25 amps. The 500 charges are if you're gentle on the current. Some of the cheaper batteries are only rated at 15 amps. Please give a link to your battery's listing if you want more specific info about that.

 

[Flatcap_FPV]

Yes what vfr400 about conditioning batteries... Ignore my ramblings!

Been a long day and forgotten we are talking lithium batteries which are memory free!

 

[Nealh]

I expect the battery is only using poor medocre China brand cells rather then genuine branded ones.
As VFR has said a battery link please.
The cells aren't solder but spot welded using nickel or steel plated nickel so not easy to repair, if you don't already have the equipment. Soldering is a no no as too much heat can damage cells.

If you have to go get the battery re-celled use Jimmy at https://ebikebatteries.co.uk/

He will make the arrangements to collect and deliver again.​

 

[naughtyus maximus]

Hi there,

A couple of possibilities to consider before going the whole hog and build an entire new pack:

1. How often do you use the bikes and Cycle the batteries? (no pun intended )
Even though they are rechargeable if they are left for prolonged periods fully charged this shortens the life span of the batteries and isn't good practice. Try giving the pack a conditioning cycle first, that may do the trick!

If you aren't using them for an extended period personally i would say 4 weeks or more (Though other peoples opinion may vary) then you should bring the battery pack down to the correct "storage" voltage.

2. You may have just one (or more) bad cell/s, in which case swapping just the bad cell would be a considerable cost saver compared to building/buying an entire pack.
This is easy to isolate any good/bad cells using a multi-meter after a fresh charge. Any cells that are particularly questionable will be considerably lower voltage than the others.
Always replace like for like capacity and discharge rate of cell.

3. You say it was a cheap Chinese kit... Unfortunately they are never the most reliable for using components that are up to scratch, they often sell products that are over-rated or use cheaper 2nd parts which were rejected at QC from a reputable manufacturer. You may have been lucky with the first kit and not so lucky with the 2nd kit.
Ultimately there is a reason why batteries are so expensive, finding an "allegedly" identical battery half the price of the other is not just retailer price variation. (10-12% price difference maybe)

USB memory sticks are a perfect example, you can buy a cheap 1Tb usb drive for about £20 on ebay, but you can only fit about 10Mb on them because they hack the boot sector so it looks like its a much higher capacity! (in reality a 1Tb usb stick is around the £200+ for a real one)

Hi Flatcap thanks for your response.

We use the bikes at least once a week,most times twice a week.They are generally pretty much out of charge each time,or at least close to it according to the displays.They then get a full recharge each time.

I paid somewhere along the lines of £190 for the battery.I've no idea if thats cheap or expensive to tell you the truth.

I'm all for saving a few bob by just replacing a defective cell,i'm just a bit concerned i will be doing the same in a months time with a new defective cell!!!.

Agreed, Chinese goods are not good,thats for sure.

 

[naughtyus maximus]

Conditioning cycles don't work on lithium batteries for Ebikes. There is a possibility that your battery is out of balance. You can check that by measuring the voltage on the terminals or charge port immediately after disconnecting it from the charger. A 36v battery should be 42.0V and a 48v one 54.6V. The further from those voltages, the more out of balance it is. Do the test first, then we can advise how to balance if necessary.

1000w motors will wear out a battery very quickly if the battery is not up to providing the power, which is normally 25 amps. The 500 charges are if you're gentle on the current. Some of the cheaper batteries are only rated at 15 amps. Please give a link to your battery's listing if you want more specific info about that.

Hi vfr,

thanks for your reply.

heres the listing link

UK E-bike Lithium Li-ion Battery 48v12ah Cannon Head for 350w Electric Bicycles for sale online | eBay

Find many great new & used options and get the best deals for UK E-bike Lithium Li-ion Battery 48v12ah Cannon Head for 350w Electric Bicycles at the best online prices at eBay! Free delivery for many products!

www.ebay.co.uk

I've only ever used the 1000w setting once just to see how fast it was capable of, 50kph on highest pedal assist setting.The rest of the time its been used on the 250w setting.

I will take it over to a mechanic friend and ask him to check the voltage.I've just recharged it today so should be an accurate reading.I'll let you know when i've got the reading.Although this has never been dropped there is nevertheless something rattling inside it.Its been like it for quite a while and so i don't believe its responsible for the sudden lack of capacity, or that it could have short circuited something as i understand the actual battery cells are shrinkwrapped.Also the battery charger has something rattling inside it and thats been rattling from new,but as it was charging up ok i wasn't too bothered by it.Gotta love those Chinese goods .

I believe my battery is only rated at 12 amps

I'll get back to you when i've got my reading many thanks.

 

[naughtyus maximus]

I expect the battery is only using poor medocre China brand cells rather then genuine branded ones.
As VFR has said a battery link please.
The cells aren't solder but spot welded using nickel or steel plated nickel so not easy to repair, if you don't already have the equipment. Soldering is a no no as too much heat can damage cells.

If you have to go get the battery re-celled use Jimmy at https://ebikebatteries.co.uk/
He will make the arrangements to collect and deliver again.

Thanks for your reply nealh

ive added a link in response to vfr

many thanks for the recommendation i'll contact them and get a price

 

[naughtyus maximus]

Thanks for your reply nealh

ive added a link in response to vfr

many thanks for the recommendation i'll contact them and get a price

I'll have to put the feelers out and see if anyone i know has a spot welder thanks for the heads up

 

[Nealh]

From the battery link I would say that no name China cells are used, likely that even your one try out run at 1000w setting will have caused cell damage as they would have been at their max limit. Battery is stated as for 250-360w output only.

Sellers who use branded cells usually make appoint of saying so.

 

[vfr400]

You can't believe anything it that listing specification. Clearly, it has been cut and pasted from an entirely different battery as it's for a 36v one. 250W or 100W makes no difference to the current if all that does is restrict the speed, which is what I guess it does. You need a wattmeter or ammeter to show what the actual current is. Does your LCD show watts. If so, what is it when you're starting off on level 5 or going slowly up a steep hill?

 

[naughtyus maximus]

You can't believe anything it that listing specification. Clearly, it has been cut and pasted from an entirely different battery as it's for a 36v one. 250W or 100W makes no difference to the current if all that does is restrict the speed, which is what I guess it does. You need a wattmeter or ammeter to show what the actual current is. Does your LCD show watts. If so, what is it when you're starting off on level 5 or going slowly up a steep hill?

Thanks for your response vfr.I've today had a mechanic friend test the voltage of the battery for me.The wheels electrics has a 4 prong connector that connects to one end of the battery.This connector has two negative terminals (prongs) side by side and there are two positive terminals (prongs) side by side,so - - ++.He took a reading from the two outer terminals first,the terminals on the battery not the connector prongs, and got a reading of 53.8v,a little down from what you said it should be.We couldn't get a reading from the two inner terminals.Bear in mind its just been fully recharged.It does have a watts reading on its lcd,but i've never payed much attention to it.I'm heading off out on it sunday,so i will pay more attention and take some readings for you many thanks.

 

[naughtyus maximus]

From the battery link I would say that no name China cells are used, likely that even your one try out run at 1000w setting will have caused cell damage as they would have been at their max limit. Battery is stated as for 250-360w output only.

Sellers who use branded cells usually make appoint of saying so.

Oh that doesn't sound too promising.That battery was the battery that was recommended by the wheel kit supplier,a different supplier to the battery supplier.If i recall correctly the wheel kit listing stated that the 250w setting was the road legal setting for the uk.But the listing then went on to tell of a stronger power level that could be achieved by disconnecting (i think) a blue wire at the controller .I tried it once just to test it out.I hadn't really noticed a great amount of difference,and as sue likes to potter along i reconnected it back to 250w setting and left it at that.

 

[minexplorer]

Hi to everyone,i'm new to the forum and this is my first post and its a problem post .

I converted a saracen mantra for my partner,. who at 62 had started to struggle with the hills the poor thing.I fitted a voilamart 250w front wheel from ebay and a 36v x-go battery, also from ebay.Putting the whole thing together was fairly simple,and the look on my partners face the first time she tried it out was a joy to behold.She absolutely loved it.She then insisted that i build one for myself as i was literally holding her up .So i converted my own mantra using a voilamart 250/1000w rear wheel and 48v x-go battery,and overall i've been very impressed with it.I've been getting about 24 miles to a full charge using the electric virtually the whole distance whilst pedalling at the same time.However the last three journeys have gotten me only about 15-16 miles.I'm assuming the capacity of some or maybe all of the batteries is getting lower.This is a bit disappointing as its only been charged maybe 60 times or so in the 8 months i've been using it.The battery listing stated it would have a lifespan of 500 charges.I never really believed that but thought i might possibly get a couple of years out of it before i needed to replace it.I've shot a message to the seller (chinese),and surprise surprise got no response.We dont have a great deal of money,hence the reason for converting our existing bikes,and i dont relish the prospect of replacing our batteries every 8 months.So i was toying with the idea of stripping the existing battery and replacing the individual battery cells myself with something that will give a greater lifespan.So,my question is,is it doable.I'm reasonably confident i can do an as was replacement if its simply a matter of de-soldering and re-soldering.Also which batteries would you members recommend that would give a greater lifespan.I'm keen to use the existing battery casing as its the only one i could find to fit my frame.Any advice would be much appreciated thanks.

ive had batteries lose range because they have become un balanced,as vrf has said.

does the battery have a dumb or intelligent BMS? if intelligent ,does the battery have an on/off switch? it MUST be ON when charging for the battery to enter balancing mode.

You can read all the cumulative cell voltages with a multimeter when drained low,to see the difference between cells. Then use a mobile phone charger to even them up. Then put the battery on a full / balancing charge. Ive had success with this recently,as if there is too much disparity between cells the BMS wont go into balancing mode at the end of the charge.

Makes me VERY angry that the charging instructions that came with each of the 3 batteries ive bought never mentioned this important point of the ON/OFF switch.ive been charging expensive batteries for years and only now have learned ive never balanced them ever. Permanent reduced capacity damage has occured to all of them as a result. You can prob catch it early tho before permanent.

 

[vfr400]

53.8V is a little low if measured straight off the charger. If you left it for a while before measuring 53.6V could be normal. It depends now whether you have one or two cells down and the rest at 4.2V or all 13 at 4.14V.

 

[naughtyus maximus]

ive had batteries lose range because they have become un balanced,as vrf has said.

does the battery have a dumb or intelligent BMS? if intelligent ,does the battery have an on/off switch? it MUST be ON when charging for the battery to enter balancing mode.

You can read all the cumulative cell voltages with a multimeter when drained low,to see the difference between cells. Then use a mobile phone charger to even them up. Then put the battery on a full / balancing charge. Ive had success with this recently,as if there is too much disparity between cells the BMS wont go into balancing mode at the end of the charge.

Makes me VERY angry that the charging instructions that came with each of the 3 batteries ive bought never mentioned this important point of the ON/OFF switch.ive been charging expensive batteries for years and only now have learned ive never balanced them ever. Permanent reduced capacity damage has occured to all of them as a result. You can prob catch it early tho before permanent.

Thanks for the post,thats very interesting.I have no idea about the bms,how would i tell which one it is?.On the battery listing page it says the bms will balance the individual batteries.
The battery has an old car ignition key type switch.When the key is turned to the first position it shoots out a locating pin that engages with a hole on the clamp to hold the battery in position on the bike.When its switched to its second position it turns the battery on.To remove the battery at the end of a run i have to switch the battery off to remove the battery from the bike.Therefor i know without a doubt that it has never been switched on when i've charged the battery up.
I guess the first step i need to take is to give it a charge with the battery switched on and see if that improves things at all.I'll do that this week and take it out for an evening run and see if it makes things any better.
On the subject of instructions,neither my battery or my charger came with any instructions whatsoever.On the ebay listing page for my wheel kit it says to attach the battery to the bike with the battery turned off,which kind of indicates that they expect the battery to be charged with it in the on position.
If this is all thats needed then it will be a nice no cost solution to the problem.fingers crossed.
Many thanks,i'll get back to you and let you know how i get on.

 

[naughtyus maximus]

53.8V is a little low if measured straight off the charger. If you left it for a while before measuring 53.6V could be normal. It depends now whether you have one or two cells down and the rest at 4.2V or all 13 at 4.14V.

Hi vfr,many thanks for the reply.I took the bike out yesterday and concentrated on the wattage display.It has 5 pedal assist settings.On setting 5,ie maximum pedal assistance,when i get going it shoots up to around 800-900 watts,then settles down to around 250 watts.Strangely,on pedal assist 1,the least amount of pedal assistance,it shoots up to 800-900w and then settles down to around 350-450w.i'm not all that confident that display is reliable,it seems to shoot up and down in ways that don't seem to make any kind of sense.
minexplorer left an interesting post about the need for the battery to be switched on when being charged in order for the cells to be balanced,which mine never has.So thats going to be my first port of call.Its fully discharged at the moment and so i'm going to give it its first recharge with it switched on and see if that makes any kind of difference.I'll let you know how i get on thanks.

 

[Nealh]

The BMS often takes it's power from the first or more often the last cell group, if it utilises a switch then this group doesn't get balanced without the battery being switched on. If a battery has a switch use it to make full use of the BMS functions, if you battery is out of balance which 53.8v suggests then it might right it self straight away or may take more charge /discharges to right it self.

 

[vfr400]

Hi vfr,many thanks for the reply.I took the bike out yesterday and concentrated on the wattage display.It has 5 pedal assist settings.On setting 5,ie maximum pedal assistance,when i get going it shoots up to around 800-900 watts,then settles down to around 250 watts.Strangely,on pedal assist 1,the least amount of pedal assistance,it shoots up to 800-900w and then settles down to around 350-450w.i'm not all that confident that display is reliable,it seems to shoot up and down in ways that don't seem to make any kind of sense.
minexplorer left an interesting post about the need for the battery to be switched on when being charged in order for the cells to be balanced,which mine never has.So thats going to be my first port of call.Its fully discharged at the moment and so i'm going to give it its first recharge with it switched on and see if that makes any kind of difference.I'll let you know how i get on thanks.

That's normal. Your bike's controller works as a speed controller. Each level limits a different maximum speed, and max power is given on all of them. Current depends on speed ( the faster the motor spins the less current you get, so the slower you go, the more current and torque you can get. Torque is proportional to current.

 

[minexplorer]

when i get going it shoots up to around 800-900 watts,then settles down to around 250 watts.Strangely,on pedal assist 1,the least amount of pedal assistance,it shoots up to 800-900w and then settles down to around 350-450w.

its normal for the controller to constantly vary the power due to things like accelerating.lowering the power when up to speed and the degree of incline/decline of the terrain an choice of gears, the amount of power needed will continually fluctuate. the higher the assist level the watts wont drop as much.

if your charger is the type with a fan you should hear it coming on and off from time to time after the green light indicates charged.then you will know its balancing.not so easy with non fan types.best to leave as much as a whole day if its never been balanced. my 52v only charges to 57.5v instead of 58.8v now.half the cells cant reach 4.2v anymore so the BMS seems to balance them all at 4.1v.