Hope that someone can suggest what I can do ....

[rogermunns]

Several months ago I was given 2 old electric bikes from a recently-divorced friend who no longer wanted them. They are Zoom Swift140 model, gents' + ladies'. Can find absolutely no info online. Friend thinks they are 10 years old. Both hadn't been used for years and both had totally duff batteries. I reasoned that new batteries and I should be up-and-running. Well, yes and no. Each battery pod looked similar to many I had seen advertised, so I bought two new packs, one 7Ah and one 9Ah. My wife and I are both well-retired and just want to poodle around for maybe 10 or 15km, couple of times a week.
Both bikes are certainly pedal-assist and both also have twist throttles. Both bikes are in excellent condition. It turns out that the original batteries are lead-acid and of course the new ones are Li-ion. What is happening is that the drive is erratic - on both bikes it's the same - you get assistance with cuts for a couple of seconds - riding on flat is better - and throttle position makes no difference. Any twist activates power (mostly) but altering the twist makes no difference.
I am now pretty sure the motors aren't happy with the Li-ion power delivery.
Question is, of course, what can I do? The bikes are too good to throw, but I now have 2 new batteries of the wrong type. I have searched high and llow for a solution, but found none.

 

[Nealh]

Are the batteries of the same voltage ?
How about some pics of the motor controller ?
Lion is a good replacement solution for SLA, can the li-ons supply enough current to the controller ?
SLA suggests possibly a brushed motor, brushed motors are often more current thirsyt then modern brushless set ups, so current demand may well be higher anf the new batteries may not be able to deliver.

 

[rogermunns]

The mystery for me is that the 'old' lead-acid pack (I stripped it apart) comprised 12 metal-sealed cans plus a load of electronics. If I use 3 12V SLAs, what about electronics? Will I just then have throttle-control? Will the motor be ok with such an arrangement?

 

[flecc]

The mystery for me is that the 'old' lead-acid pack (I stripped it apart) comprised 12 metal-sealed cans plus a load of electronics. If I use 3 12V SLAs, what about electronics? Will I just then have throttle-control? Will the motor be ok with such an arrangement?

They weren't lead acid batteries then, if rectangular cans they were lithium, probably lithium-manganese similar to this one below:



The electronics in the battery are only its management system which also relates to the charger. but you'd need a different charger with SLAs of course.

Everything can work with SLAs, but it will have a very short range, so normally it would be much better with a new lithium battery. However the ones you've bought seem as though they perhaps can't deliver enough current for the system, though that's only a guess at a distance from the behaviour.
.

 

[Alan Quay]

Yeah, pics of everything will be very helpful. Agree with Flecc, does not sound like SLA's in the original battery.

 

[rogermunns]

What I really want to know, is what would you do if you were in my position? The new Li-ion batteries are same voltage. The pics here show the cells I got out of the metal can (I had to slit it open, the batteries / electronics / insulating sheets were tight jammed inside). There were 10 cans, I'm not sure what I did with one of them. There is a clue to the age because in pic 2 I can see 06.12.11 but of course that could be 2011 or 2006. I think 2011 is more likely.
When you ask about controller, where is that? Is it not the electronics pictured here? (And there is something in the new Li-ion can?).

 

[Alan Quay]

So, that is not a lead acid battery, but an older style lithium.
I assume the electronics pictured here is the BMS (part of the battery that manages the cells)

What we really need to help you are pics of the bike. We have no idea where the controller is either, but I'm pretty sure there will be one.

If you follow the throttle wire it will lead to the controller.....

 

[vfr400]

The two smaller pcbs are to keep the cells balanced and the other one is the protection board that switches off power when the battery goes flat or if you try to take too much current from it, and it switches off charging when it's full.

Show us a picture of the bike. There's no such bike as a Swift Zoom 140. I think you're describing the forks.

 

[rogermunns]

Here are some pics. Maybe someone could identify the various items' suitability. As I said, Li-ion battery packs, correct voltage, will not drive the motors properly (intermittent power). Whether they are too powerful or not powerful enough seems the question, but importantly what can I do? Both Gent's and Ladies' bikes have identical controllers, motors and have the same problem. Also on both bikes the throttle controls do no controlling, they are either off (no twist) or they ask for power (twist to max. makes no difference).

 

[rogermunns]

I just had an idea. Could I use both Li-ion packs (in parallel) so see if it is indeed the problem that the new battery packs can't give enough umph? Is there any danger in doing this? I would use wire of suitable current-handling ability.

 

[vfr400]

I just had an idea. Could I use both Li-ion packs (in parallel) so see if it is indeed the problem that the new battery packs can't give enough umph? Is there any danger in doing this? I would use wire of suitable current-handling ability.

Those batteries are almost certainly shagged. I've repaired several of them in the past. When shagged, they still charge to 42v and all the cells will measure as 4.2v, but as soon as you try to take current from them, the voltage collapses. You can only see that if you do a proper load test. You can buy cell-packs with the BMS that just require the main wires and charge wires to be soldered inside the case. Always check the dimensions against the case because there are different sizes. Alternatively, replacement batteries aren't that expensive, You can find the batteries and cell-packs on Ebay and Aliexpress.

Edit. I'm referring to the old batteries. i didn't realise that you had bought new ones.

At what speed do the cut-outs occur? Do they happen if you keep the speed below 10 mph?

Can we see a picture of the handlebars from the top?

 

[rogermunns]

Thanks for reply. Yes, the old batteries have been ditched. New ones are 36V, 8.8Ah and 36V, 7.0Ah respectively (gents', ladies'). Both show same symptoms, at any speed. Uphill the motors sometimes groan, and cut out much more. First pic - gents' handlebars, 2nd = ladies'. I weigh 72kg.

 

[vfr400]

Next question: One of the bikes has battery indicator LEDs on the throttle. How do they behave during the cut-out.. Do they go off with the motor or go down to the red or hold firm?

 

[rogermunns]

Thanks. I usually go out for 8 - 10km rides. What I have seen with the display is that the top green light gradually fades and then goes out after 2 journies. Third journey maybe 4th the second one will go out. Have not ridden any significant distance after I have just red. I have noticed a diminution of the top green light when using the motor. But not the other two lights. I haven't noticed what happens when I am in the 2nd green status, but suspect that will also fade when the motor is on. I think I see what you're getting at ---- the battery might not be man enough ??
Is it safe to connect both Li-ion units I have, do you think?

 

[vfr400]

Thanks. I usually go out for 8 - 10km rides. What I have seen with the display is that the top green light gradually fades and then goes out after 2 journies. Third journey maybe 4th the second one will go out. Have not ridden any significant distance after I have just red. I have noticed a diminution of the top green light when using the motor. But not the other two lights. I haven't noticed what happens when I am in the 2nd green status, but suspect that will also fade when the motor is on. I think I see what you're getting at ---- the battery might not be man enough ??
Is it safe to connect both Li-ion units I have, do you think?

You didn't really answer my question: Specifically, do the lights go off at the exact time the motor cuts?

 

[rogermunns]

No.

 

[rogermunns]

The lights do nothing when the power is requested - they stay on. After 20km or so the top green light will have faded to nothing, then the second green light will be full, fading to nothing in another 20km or so. I just went out this evening - only 7km, but power was assisting fine for a lot of the time, uphill or flat. On two of the up inclines the motor cut in/out/in/out every few seconds, then might be ok for 30 sec up rest of the hill. Recall that I have 2 of these bikes (one M, one F) identical situations, both do the same.

 

[vfr400]

That rules out the battery as the cause. The most common causes of that sort of fault are brake switches, which you can eliminate by disconnecting them to test, or motor connectors. You have to follow the wire from the motor all the way into the controller and check that every connection is sound.

 

[rogermunns]

Thank you vfr400. I am a newcomer to elec. bike technology and am struggling to understand some aspects. What are brake switches? I am guessing that are to do with some braking mechanism of the motor? Maybe the intention is to make sure the motor cuts when you put the brakes on, so it is not fighting against the brakes? Anyway, I guess I can work out which wires they are and check connections. But I have to say I'm not too hopeful since I have 2 bikes, both using exactly the same components (except for the frames and the wheel sizes because they are ladies' and gents versions). Both bikes have same history, both having new Li-ion battery packs and both bikes showing just the same problem. Can you tell me how the throttle twist works? Is it a potentiometer? Do they fail? With both bikes there is no assistance by merely pedalling - you have to also twist the throttle grip. And how far you twist makes no difference - as soon as you twist there is assistance. That is, until the motor decides to cut. Or not, if you are lucky.

 

[vfr400]

Throttle work with a hall sensor and magnets to give a signal between roughly 1v and 4v.

Brake switches are in the brake levers. Follow the wire coming out of the brake until you come to a connector.

Check that the motor connector is all the way to the marked line.