motor feels weak...

[pcspinheiro]

Hi everybody,

great site and loads of info. However, neither this nor google seem to be helping out with my problem... I have a electric bike that I made using a kit off ebay from some hungarian seller. It uses a 36v, 250W motor and 3x 12V SLA batteries. Its was mostly used by my wife and ran fine. It was left stopped for about 1 year after we had our second child and the batteries never took charge again so I just finished replacing them. However, even though they are the same (7 Ah) as the original ones, the motor feels very weak... it had a lot of torque before. Also, if one makes any resistance for the bike to start moving you can actually hear the motor whirring inside, as if something is moving, but the wheel won't be spinning. I took it apart (at least partially, and the gears don't look worn, at least not noticeably, but I was not able to get inside the motor itself. What is the most likely cause for this? If the gears were worn out it would never pull, I guess, but it does pull... Any ideas are greatly appreciated, we are moving away from Denmark and will sell it but I don't want to sell a turd, plus if it runs well I can possible get more for it.
Thanks in advance!
Best regards,

Paulo.

 

[flecc]

I think the replacement batteries may be the wrong type Paulo. These SLA batteries are made for various purposes, and those for burglar alarms and the like have very long life but inadequate discharge rates for an e-bike. The type motor cycles use for starting are also unsuitable, since they have short life if used continuously at high discharges.

The ones we use have to be deep discharge types that can deliver large amounts of current continuously on demand to give the power, yet not be damaged by emptying them in this manner.

They often look the same externally, and the wrong types are more common these days now that e-bikes mostly use lithium batteries.
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[pcspinheiro]

Thanks for the very quick reply! Maybe I got the wrong batteries then, they look the same and hold the same 7ah but there is no info on discharge rate, not on the old ones nor the ones I bought... But how does that explain the motor whirring but nothing moving? It really feels like something is turning inside... And how to know the next ones will be right? I don't remember ever seeing discharge rates mentioned on betterirs or the eBay adds where I looked...
Regards, Paulo.

 

[Deleted member 4366]

You need to tell us exactly which batteries you have. It might also help to tell us which bike you have and, if possible, something about the motor.

If you don't know what they are, show us some photos.

 

[pcspinheiro]

Thanks again! Here are some photos with the previous batteries, the motor and the new batteries (the ones with tape and the red wires on top. I have nothing else on the motor... no brand, no nothing.

 

[flecc]

Literal translation of the Polish new battery text, not quite sure what to make of it. D8veh?:

Standby mode: 13.6 - 13.9 v

Work cycle: 14.5 - 14.9 v

Maximum start initiation below 2.1 A
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[Alan Quay]

The last one is the initial charge current. All the ones I've used previously are in the 4amp range.

 

[Deleted member 4366]

As far as I can figure out LP7 is a storage battery, not one for electric vehicles.

 

[flecc]

That was my suspicion too, and it could account for that lower power. I don't think we can make much of that motor whirring indication until it has an adequate power source.
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[pcspinheiro]

OK, that sucks... I had no idea that a 12V 7Ah SLA battery could be so different from another, similar looking 12V 7Ah SLA battery... What will happen if I leave these in? OK, lower power, sure, but also higher range? Will this cause damage to the batteries and/or motor?
And the ultimate question, does anyone know where to source the correct ones at a reasonable price, in Europe? On ebay it's very hard to tell if you're getting the right thing, as the descriptions can be rather vague...

Thanks again for all the valuable help!
Regards,
Paulo.

 

[flecc]

Unfortunately, with low power batteries not just lower power but probably shorter range and definitely shorter life, due to the stress the batteries suffer in trying to deliver the necessary current.

The right ones are getting increasingly difficult to source due to the lack of e-bikes now using them. They will be available, but the couple of definitely ok sources I once knew on ebay no longer supply them.

It's likely another member will know of one though, but it may be after the weekend before an answer since the forum is quieter at weekends in fair weather.
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[Deleted member 4366]

When you buy your next ones, make sure that the description says that they're suitable for electric vehicles.

 

[flecc]

Adding to d8veh's answer, if you have a mobility chair company in reach they will know the right kind of batteries since that's the type they need too, so could advise or maybe even know a source. This is the sort of thing I mean by mobility chair:

 

[Alan Quay]

Try vbat.co.uk

They have 7ah deep cycle SLA's

 

[flecc]

Here's the link to the right item at the company Mike mentions. Check the dimensions are ok:

AGM deep cycle battery
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[pcspinheiro]

Thanks so much for all the help! Those are a bit pricey though... The problem I have recurrently ran into is that sellers advertise their batteries as being for "deep cycle" or "mobility devices" and a quick visit to the manufacturer's webpage (when one can be found) shows they are no meant for that purpose... I may have found some on ebay (both UK and .de) that may do the job. In the meantime I need to get rid of these... I will just try to send them back to the seller since they are clearly poorly advertised (I got batteries that do not match the pictures or description, as they say they can be used for mobility devices).

Best wishes,
Paulo.

 

[flecc]

Thanks so much for all the help! Those are a bit pricey though...

Under £90 for a set of three is far from pricey in the UK Paulo, I've seen them at £120 at the upper end of pricing. Anything much cheaper could be the wrong type. Maybe they are cheaper in Eastern Europe though.
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[Alan Quay]

Thanks so much for all the help! Those are a bit pricey though... The problem I have recurrently ran into is that sellers advertise their batteries as being for "deep cycle" or "mobility devices" and a quick visit to the manufacturer's webpage (when one can be found) shows they are no meant for that purpose... I may have found some on ebay (both UK and .de) that may do the job. In the meantime I need to get rid of these... I will just try to send them back to the seller since they are clearly poorly advertised (I got batteries that do not match the pictures or description, as they say they can be used for mobility devices).

Best wishes,
Paulo.

I have purchased batteries from vbat a few times, and I can vouch for them. If they say they are suitable for electric vehicles, then they are.

If you buy batteries from ebay, you take your chances. We have had a few people on here recently with new batteries that are clearly not suitable.

 

[pcspinheiro]

OK, thanks again for the comments. However, I have found a UK seller on Ebay that is, supposedly, selling the exact same MK ES7-12 7.2 Ah battery (as sold on the vbat link that flecc posted)for only £11 + VAT each! Now that's quite cheaper, if I can get him to ship them my way (Denmark).

http://www.ebay.co.uk/itm/2-x-12V-7-2-AMP-AGM-MK-Battery-ES7-12-Mobility-Scooter-Batteries-/251502519162?pt=UK_Health_Beauty_Mobility_Disability_Medical_ET&hash=item3a8eb7e37a

 

[flecc]

Wow, that's the lowest I've heard of for many years! I hope they are the right type.
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