chris301up

I have just purchased my first electric bike through Ebay.

This was advertised as a 'Non-Runner' due to the fact that it cuts out and I'm hoping it won't be too much of a problem to rectify.

I have now fully charged it and taken it out for a test ride and sure enough it cuts out on full throttle.

If I switch it off and back on again it will run until I open the throttle fully, and the problem repeats itself.

I have since found out that should I place this on the stand, with the rear wheel off the floor the problem does not occur, but as soon as I put it back on the floor with any weight on it, including the weight of the bike, then the problem repeats itself.

Can anyone please advise?

Unfortunately, I am unable to say what make and model this is as there are no stickers on it to indicate the manufacturer.

Maybe someone can give me some help in this direction also?

nwmtnbkr

Does this have a LIFEPO4 battery? If so, there's a Battery Management System (BMS--a computer board) on the battery that protects the system that may be shutting down when the throttle's full--many people may buy the appropriate Volt battery but do not realize that they need to look at the maximum continuous discharge amperage of the controller and make sure the LIFEPO4 has adequate discharge ratings. Otherwise the BMS will shut the system down when the throttle's opened up and the amperage peaks.

If the battery isn't LIFEPO4, there may be a controller or throttle issue. If you have a volt meter, check the reading on both.

chris301up

When I purchased the bike it was advertised as having a LI-PO battery, so at this stage I can only assume it has a LIFEPO4 battery, but I am going to have a more detailed look at it over the next couple of days.

I don't have a volt meter yet but will aquire one if necessary?

As I am unable to find out the manufacturer of the bike will battery's from other manufacturers also be compatable with my machine?

Zephyr Boy

I just bought and installed a Cycle Analyst meter on my e-bike. After hooking it up and testing it on the stand, with the front wheel (my e-hub) off the floor, it was putting very little strain on the battery and controller unit(I suppose). Placing the e-bike on the ground however, drew much more power from the battery, and then some more when fully loaded (my body weight). I know this a small contribution to a paragraph you wrote, hopefully it will spark other ideas? Good luck.

JinbaIttai

So you bought a mechanic's special and now you need the help of a mechanic to get it to work. Lol.
It will help if you figure out what kind of battery you have. What voltage is the battery at?

nwmtnbkr

Chris,

If the seller didn't provide you with any of the documentation that should have come with the bike, I would suggest you re-contact the seller and ask some specific questions. If it's a LIFEPO4 battery, was it original or a post-purchase upgrade. If an upgrade, who was the vendor and what version of BMS does the battery have, most importantly, what's the amperage rating for maximum continuous discharge. You also need to know specs on the controller if the seller still has any. Is this a conversion kit bike or a bike bought outright as an e-bike. If you can give some info, maybe people can help point you to some online documentation.

If you have a friend who has a volt meter, you might ask to borrow it. Otherwise, they're fairly inexpensive and can be found at most hardware stores. Using one will be able to pinpoint problem that may reflect a short or other electrical issue impeding proper functioning of electrical components. If any of your friends have motorcycles, maybe they could help you test the throttle and controller.

If this bike truly has a LIFEPO4 battery, I'm more inclined to think there may be a problem with the discharge ratings--not enough for the controller--and that the BMS is shutting the battery down to protect it when you hit the throttle. If you get the bike moving through pedaling and then slowly depress the throttle does the battery still shut down?

Good luck, you should be able to pinpoint the problem.

alfonsopilato

I'm no expert, but my gut feeling tells me this is a BMS related matter, I agree with nwmtnbkr

1st get a voltmeter, yes i absolutely agree. find out what your battery voltage is at when fully charged, that will give us an idea what we're dealing with.

2nd I would get a cycle analyst hooked up,

then , i would use the analyst to control the max amperage drawn.. you are bound to hit the sweet spot . start with 40 amps and make your way down as the problem persists.


how do i know? because i gots the same behaviour on my 72 volt system. if i throttle too fast from standstill, too much current is drawn to propell the bike from a zero velocity, and this leads the bms to shut down,

in fact for that exact reason i added a push button normal close switch which i use to disconnect the battery from the controller. so when the bms shuts down, i perform a reset using this switch so that i don't need to physically disconnect the wires etc etc and interrupt my travel

nwmtnbkr poses a good question.. what happens when you throttle slowly, meaning as the bike picks up speed and presents less rolling resistance, squeeze the throttle gently .. the theory being, you draw less amps all at once and you don't irk the bms , that should keep you rolling. you should be able to go full throttle once your bike is moving at an adequate speed.


i don't think it's a throttle issue. all the throttle is : it's three wires, basically. one ground, one 5 volts coming from the controller and the third is a percentage of that 5 volt coming back from the throttle going to the controler. as you squeeze the throttle you change the resistance and draw a percentage of that 5 volt which is what that third wire is.. therefore that third wire has 0 to 5 volt on it depending on the position of the throttle and the controller translates that voltage signal to a percentage of your battery's voltage and sends it to the motor. simple and if that throttle were malfunctioning, the kinds of symptoms you'ld get would not be a shutoff of the batteyr but more like the bike stuck on full throttle or not starting at all, i.e some kind of pinched wire shutting off the 5 volt signal to or from the controller

ok, so once you've hooked up a cycle analyst and controlled how much amps you're drawing form the battery .... and you've gone as low as say 20 amps, and the problem persists.. then i would have to conclude that you've got a problematic BMS or the battery is not correctly balanced. I know this is kinda hazy in its description, but i'm no electronic genius

i'm not an expert, just lived a few of those moments and what i've told you so far is based on experience.

in effect i've repeated what nwmtnbkr said but corrolated it with events that have occured in my ebiking experience

keep on truck'in letuce know what you find (and yes i know it's let us and not letuce )

chris301up

Thank you all for your advice.

I have tested the battery at full chage and it reads a steady 36 volts and 5ma.

This may seem like a silly question but when openning the trottle are the lights on the power indicator supposed to decrease to the empty position or are they supposed to remain steady? This is whats happenning on this bike and I was thinking this may help to direct me to the fault.

I am reasonably adept at mechanics and electronics so I thought I would buy this as a project to work on and if I can sort it out fine, if not, I'll probably scrap it!!

alfonsopilato

ah yes, when i described the throttle i said there are three wires.. where there are cases where there is a 4th wire. that 4th wire carries the full voltage across your battery and is meant as an indicator (it only carries the full voltage not full amperage, thank God.)

that indicator wire is hooked to a series of LEDs which light to let you know what voltage you're at.

so the answer is yes, it's normal that under load the battery pack will read a lower voltage than nominal, and as a consequence your LEDs will reflect the same. i wouldn't put too much stress on that indicator, i personally don't like it much _ it's a gadget mor than anything else, IMO,

alfonsopilato

36 volts you say? hmmm.. ok

ok, keep in mind that a BMS on a LIFEPO4 battery will shut down if a) it reaches critically low voltage or b)too much amps are drawn all at once (i'm basing this on what i've lived, for more detailed info, you may want to contact a LIFEPO4 expert)

it would be good to know what your controller is rated at, and the same for your motor... that way you can get replacement battery and controller if necessary.

what i was about to propose is slighty costly but it will definitely lead to a resolution. it's called scoping the problem by replacing parts for knwon good components.

i.e you want a known good battery and put in instead of your existing one
same goes for your controller

this is what i would have done in your place.. and if i replace the battery and the problem goes away, then i know it's my battery. see? i told you i was not electronic genius, this is simple troubleshooting 101 for those who don't mind spending a little.

that experiment may cost ya around 500 bucks (notice the use of ya instead of you, that's meant as a suthern accent, i use it whenever i talk ridiculous money )

but.. if you get a cycle analyst and limit the amperage, that may be less costly as a first step in resolving your issue. these analyst run you around 120 bucks US or so. i got one and i honestly tell you that i can't imagine operating my bike without it. now here's the catch, in order for this analyst to work, it needs to hook up to your controller... so you know where i'm going with this. you'll need to lookat your controller. www.ebikes.ca not only sells these analysts but they actually build them. they are great folks, i would contact them if i were you and get into a convo with them about the types of connectors you have on your controller and see if you can fit one on.

for those reading this, please don't fry me for my proposition of replacing parts as a means of troubleshooting... i come from an I.T. background, and that's how i normally resolve issues, i tackle the probable causes by ensuring i have good components at hand to swap, so you can imagine i have more than one pc at home etc, for that reason, one pc goes down, i open it up, suspsect it's this or that component, i swap parts, whammo done.

chris301up

Just an update.

I have fully charged the battery once again and taken it out for a test ride.

If I get it moving and gently open the throttle the indicator lights decrease on the indicator panel and eventually the bike cuts out. This is far more apparent on an uphill gradient.

Also, when I pedal (without using the throttle) the motor kicks in and again it cuts out when I put more pressure on the pedals.

alfonsopilato

hmmm ok.. i was gonna ask you at which point the cutting out happens and you've beat me to the punch

that uphill gradient tells me something, the fact that the problem is more pronounced uphill tells me that it's a "load" issue. by that i mean, the battery is unable to supply the requied power to the motor and reaches its limit and cuts out.

if you had a cycle analyst hooked up, i bet you that you would see your amps and wattage go high just before your battery cuts off. and by "high" i mean whatever cut out point your battery can't afford. that number may differ based on the battery. in your case that limit may be reached because your battery reached its limit and that may be due solely to the capacity of your battery, or the battery reaches its limit sooner because one or more of its cells isn't properly balanced or the bms itself is busted. whatever the root cause the scope of the problem is quite clear at this poitn, it's causing the bms to believe it's attained the limit. in movie terms, "you [the battery pack] can't handle the truth !!! [amperage]"

how much did ya pay for the bike? if ya don't mind my asking (use of ya, means i'm talking money, lol)

all levity aside, you need to consider how much you're willing to invest in this. are you looking to get a good performing bike etc? maybe i should just read your post ok so that tells me something. well, i was of the same mindset when i started and had a budget cut out , so there ya go.

misslexi

From what I've seen a 36V LiFePO4 should show more than 36V when fully charged, at no load, more like 40V. Since buying a battery just to see if that's the problem is expensive guess work, as is buying a controller, there may be a cheaper alternative.

If you loaded the battery with a 2 ohm resistor it should draw about 20 amps. Problem is that's 720 watts and most resistors can't handle that. But, you could buy a bunch of relatively inexpensive power resistors from Radio Shack or better yet, a local electronics store, then parallel them to build up the power rating to some respectable level. So you could but 10 20 ohm resistors and parallel them to get your 2 ohms, if each one could handle 20 watts you'd have a 200 watt dummy load.

The experiment may toast the resistors if the total power rating is less than the planned power pull, that's why you want to find cheap ones. And all the the power draw is converted to heat so I'd set the dummy load on cement or metal, not the family dining table.

Put your volt meter on the battery and touch the load, if it cuts out then you most likely have a battery/BMS problem, if not, it's more likely a controller/throttle issue.

chris301up

Heres an idea. Whats the problem with hooking up 3 x 12 volt rechageable batteries and seeing what happens? The BMS - is that the circuit board inside the battery case? Should I hook up 3 batteries - do I actually need the BMS?

alfonsopilato

misslexi now we're talking!

Chris, i'm very interested if you decide to perform the load test, so please keep us posted

errrm.. if you decide to place 3x12 volt batteries, what amperage is it outputting. so.. we're talking 36 volts at how many amps? all the bms does is ensure that the battery pack discharges and charges the cells equally, and in addiition it has a cutoff circuit to protect the pack from overdischarging.

nwmtnbkr

I think you definitely could test the bike with 3 12-volt SLAs. Just make sure the rear rack can handle the weight before you mount them and be careful about hitting bumps while doing a test ride with 3 SLAs on board.

I have seen posts on other forums by people who run Elite Power's LIFEPO4 batteries without a BMS , but you have to be especially careful while charging. Your battery may not have an optimum life span, but then you bought this as a non-runner so, hopefully, you're not out-of-pocket too much. It might be preferable, if you're comfortable with electronics, to disassemble the battery pack, examine it to see if you have bad cells or soldering and, if necessary, beef up the BMS using a compatible one rated to handle the maximum continuous discharge rate of your controller (BMS boards have improved, Ping batteries out of China are now using version 2.5 of their BMS). Good luck.

chris301up

I thought the BMS did that but wasn't sure.

I know the battery for my bike outputs at 36 volt but there is nothing on it to indicate the manufacturer or other output details.

The batteries I was thinking of trying are listed as follows: 3 x NEW 12V 10AH Mobility Scooter/Electric Bike Batteries.

They are listed at a good price and are relatively close to me.

Your further comments would be appreciated.

ecowheelz

As other posters have mentioned, it sounds like the BMS is cutting out the power when the bike is under load. It's probably an aftermarket battery that wasn't compatible with your bike / controller. The SLA's should work great if this is the problem. Not sure if you can bypass the BMS, but that would be one option. Otherwise, the easiest solution might be a new battery...

misslexi

Thought of one other idea: I've heard that controllers also have low voltage cutoff. I guess that means it could be the either the BMS OR the controller shutting down. The fact that you can get this to reset by turning off the controller makes me think it's the part making the decision and not the BMS. Maybe others know if a BMS that's entered the shutdown state takes time to reset?

Your idea to try different batteries is sound, if not expensive. I hate to see you spend money on heavy, relatively short-life SLAs just for a test. If I had this problem I'd scavenge 3 batteries from my lawn mower, ATV and snowmobile. Heck even my better half's car battery could be missing for a while, just to test of course.

nwmtnbkr

Chris,

SLAs are heavy and you may find the bike doesn't handle as well as you'd like if all three are mounted on your rear rack. You might want to consider alternatives before purchasing SLAs. Several web sites sell 36V NICADs and NIMH packs, which will weigh less than SLAs (and have a longer life). Ebikes.ca even sells a 36V 8aH Nicad in a triangular layout that will fit in a bag that hangs off the frame for $240, giving you a better ride with a lower center of gravity.

chris301up

Just another update.

I have now disconnected and by-passed the BMS from within the battery pack, taken it out for a test ride, and sure enough - IT WORKS !!!

There is the odd intermitant hesitancy (cut out) particularly under full throttle, but I would now probably assume this is due to a bad cell?

At least it has given some idea to where the fault lies.

My only problem now is to find out what the AH is on the existing battery so that I can order the correct replacement.

nwmtnbkr

Chris,

Congratulations on tracking down the issue. Now what you really need to know is the maximum continuous discharge rating for the controller. The BMS has to allow the maximum amperage drain required by the controller or you'll have shut down issues again when you open the throttle up or climb hills since the amperage drain will increase. It's conceivable that this battery is under-powered, in terms of amperage ratings, especially since it appears that the BMS is shutting the system down when the controller is calling for more amperage. If you don't want to pay for a new LIFEPO4 battery right now (they are expensive), you could consider alternatives, including NiCADs. Good luck.

alfonsopilato

me and my friends kept saying it's the bms, bms bms and surely enough looks like it

that will be $23.67 please.

we only accept credit or debit cards and money orders

JinbaIttai

The correct AH you want is the biggest possible who's weight you can tolerate. 15 to 20 ah is a typical sweet spot.


EDIT: Wait. Is this battery mounted in some kind of case? Feel free to post photos!

alfonsopilato

correct me if i'm wrong, AH is the measure of how long a battery can supply a given voltage at a given amperage. it's the equivalent of liters of gaz. so in your case, as long as you have the matching voltage and amperage, you should be fine