Hi guys

Could anyone give Me some possible theories to why a brand new battery failed after just 2 weeks (30miles)

I have 2 possible culprits

 

1) Re-gen braking from the KT 48v 30amp controller?

2) charged battery off the bike (key in off position) until full, then turn key to (on position) and charge for another hour.

 

Maybe one of these actions tripped the BMS? Or maybe a combination of both the above? I have a new replacement battery now, but I'm very nervous of this happening again. Some advice would be very helpful indeed as I'd love to turn the Re-gen back on, and not have to send this battery back also

Thanks in advance

Daron

Edited August 15, 20214 yr by CreativeSource

Which bike and battery do you have?

Which bike and battery do you have?

It's a generic 48v 15ah silverfish/whitebait pack from eBay. And it's My Wife's converted freego hawk

Edited August 15, 20214 yr by CreativeSource

Can the battery deliver 35a or more continuous ?

How has it failed? What are the symptoms?

How has it failed? What are the symptoms?

It just died on My wife after about 20 meters, the lights on the pack were indicating a full charge, and indeed it was fully charged, but would not power up the KT3 LCD display, so I tried one of our 36v freego packs just to rule out any other possible cause, this pack turned everything on immediately, so now it all pointed to a faulty 48v pack. The seller said the BMS had failed, but I think he may of just been quoting my theory of what I think happened.

I believe the controller to be a KT 48v 1000w rated current 15A, maximum current 30+1A

The battery BMS is rated at Continuous discharge current 20A.

Peak discharge current 25A - 30A.

Edited August 16, 20214 yr by CreativeSource

Lithium batteries and BMSs can't just fail like that. The cause of your problem is probably something simple, like a fuse or broken connection.

 

What is the battery's current rating? Can it supply 30A continuous? Not many silver fish type can!

Lithium batteries and BMSs can't just fail like that. The cause of your problem is probably something simple, like a fuse or broken connection.

 

What is the battery's current rating? Can it supply 30A continuous? Not many silver fish type can!

I believe the controller to be a KT 48v 1000w rated current 15A, maximum current 30+1A

The battery BMS is rated at Continuous discharge current 20A.

Peak discharge current 25A - 30A.

May I just add, We now have a replacement pack from the same seller, this pack has so far done 100 miles with no issues, the only 2 things I've done differently are the 2 theories at the top of the thread.

We've had ebikes since 2016, We have 8 batteries, and never had a problem with any of them. But We have with this one hence why I'm trying desperately to find the reasons so it doesn't happen again.

The peak discharge rating is only a temporary one for a few seconds use of 5 -10 secs.

If you are using a throttle or PAS 5 then the battery with a 20a continuous rating will be under stress.

If the KTLCD3 doesn't turn on then you have to look at an issue with the battery connection, as vfr has said an internal fuse or wire fault is likely. Though the battery rating is sub par for the controller rating.

I believe the controller to be a KT 48v 1000w rated current 15A, maximum current 30+1A

The battery BMS is rated at Continuous discharge current 20A.

Peak discharge current 25A - 30A.

May I just add, We now have a replacement pack from the same seller, this pack has so far done 100 miles with no issues, the only 2 things I've done differently are the 2 theories at the top of the thread.

We've had ebikes since 2016, We have 8 batteries, and never had a problem with any of them. But We have with this one hence why I'm trying desperately to find the reasons so it doesn't happen again.

That battery is hopelessly underrated for a 30A controller. The 15A on the controller means nothing, functionally. The only thing it does is regulate the current to max 30A. It would be immoral if you asked the supplier for a replacement. Unless the supplier changed something in the second one, it'll soon go the way of the first. You need a 30A CONTINUOUS battery for a 30A controller.

The peak discharge rating is only a temporary one for a few seconds use of 5 -10 secs.

If you are using a throttle or PAS 5 then the battery with a 20a continuous rating will be under stress.

If the KTLCD3 doesn't turn on then you have to look at an issue with the battery connection, as vfr has said an internal fuse or wire fault is likely. Though the battery rating is sub par for the controller rating.

The thing is Nealh, when the 1st pack wouldn't power up the LCD, I replaced the fuse immediately - no good, then I simply tried one of our 36v silverfish packs in the bike, it powered up immediately? So I believe fuse or faulty wire on the bike is to be discarded. And indeed the new replacement pack has now done 100 miles with no problems? That's why I'm trying desperately to discount one or both My theories at the top of the thread as the causes for the pack dying.

 

I certainly take on board what you're saying about the pack, and controller rating being a tad tight, but minus (no Re-gen, and charging with key turned on) this time, the 2nd pack is performing fine?

Battery rating isn't just a tad tight, it is continuous rating is 30% less then the max controller rating. I would say that the battery rating is being misused and stressing the cells unnecessary if used for long periods at high current.

That battery is hopelessly underrated for a 30A controller. The 15A on the controller means nothing, functionally. The only thing it does is regulate the current to max 30A. It would be immoral if you asked the supplier for a replacement. Unless the supplier changed something in the second one, it'll soon go the way of the first. You need a 30A CONTINUOUS battery for a 30A controller.

I certainly do not think it is immoral to ask for a replacement pack? You have to remember, not all of us are as technically minded as you guys. I've learned a great deal in a couple of years about this stuff, but do not proclaim to be an expert, that's why I'm asking for advice. This pack is rated on the sellers eBay site has good for 1000watt ebikes, and both the current ratings on the pack, and controller seem to match up from My perspective. I even asked him all this numerous times in our enquiries?

But if indeed this is the reason for the failure of pack 1, then I can always turn the controller current down in the KT3 LCD... Yes?

I certainly do not think it is immoral to ask for a replacement pack? You have to remember, not all of us are as technically minded as you guys. I've learned a great deal in a couple of years about this stuff, but do not proclaim to be an expert, that's why I'm asking for advice. This pack is rated on the sellers eBay site has good for 1000watt ebikes, and both the current ratings on the pack, and controller seem to match up from My perspective. I even asked him all this numerous times in our enquiries?

But if indeed this is the reason for the failure of pack 1, then I can always turn the controller current down in the KT3 LCD... Yes?

Most 1000w kits/ebikes have 25A controllers, so that battery would be just about suitable for them.

 

As far as batteries are concerned, they're all suitable for 1000w motors. It's the controller that you have to match them to because it's the controller that regulates the max power. Your 30A at 48v is about 1500w from the battery.

Edited August 16, 20214 yr by vfr400

Most 1000w kits/ebikes have 25A controllers, so that battery would be just about suitable for them.

 

As far as batteries are concerned, they're all suitable for 1000w motors. It's the controller that you have to match them to because it's the controller that regulates the max power. Your 30A at 48v is about 1500w from the battery.

I understand what you're saying and completely take it on board, thank you. But could you possibly give Me an answer to one of My possible theories also? (Re-gen braking)

The 1st pack was charged full, then (off the bike) I turned the pack key (on) it then charged for another hour? Then My wife braked in the first 20 meters, could this of overcharged, and then tripped the BMS?

Regen is generally very bad for most batteries, depending on how it's regulated. Those batteries should be charged at about 2A. On a steep downhill or using EABS, you could go ten times that if the regen is unregulated. The other thing is that regen charges through the discharge terminals, which by-passes all the normal charge controls.

 

Does your controller specifically mention regen or EABS and is it switched on in the settings? If not, it probably doesn't do it.

Edited August 16, 20214 yr by vfr400

Regen is generally very bad for most batteries, depending on how it's regulated. Those batteries should be charged at about 2A. On a steep downhill or using EABS, you could go ten times that if the regen is unregulated. The other thing is that regen charges through the discharge terminals, which by-passes all the normal charge controls.

 

Does your controller specifically mention regen or EABS and is it switched on in the settings? If not, it probably doesn't do it.

Thanks for the reply.

The Re-gen braking is switched on/off via the KT3 LCD, It as levels rated 0-5. 0 being off, and 1 giving the most Re-gen charge back to the pack, but not the most braking power, if that makes sense? It does to Me. Level 1) being maximum charge but little help braking.

Level 5) being maximum braking (in fact dangerous) and very little charge

Battery rating isn't just a tad tight, it is continuous rating is 30% less then the max controller rating. I would say that the battery rating is being misused and stressing the cells unnecessary if used for long periods at high current.

I can lower the current from the controller to the battery via the C5 setting on the KT controller. I've also obviously removed the Re-gen function also in the C settings.

 

1) But in My defence, 15amp rated current, 30a max (controller)

2) 20amp rated current, 25-30amp max (Battery)

you can see why most of us would believe this was a good match, including the seller when I asked him this question several times.

I can lower the current from the controller to the battery via the C5 setting on the KT controller. I've also obviously removed the Re-gen function also in the C settings.

 

1) But in My defence, 15amp rated current, 30a max (controller)

2) 20amp rated current, 25-30amp max (Battery)

you can see why most of us would believe this was a good match, including the seller when I asked him this question several times.

 

Seller doesn't know what he is selling or understanding the ratings.

 

The controller is 30a rated current, this will be the defacto current if throttle or PAS 5 is used, yes the current can be dialled back but so will the bike performance esp climbing. The 15a rated current is only if you want a tame/limp bike using those 1000w DD hubs.

The battery is a 20a continuous rating, the upper rating 25/30a is only for brief 5 -10 second bursts typically but even this will stress the cells early reducing it's life.

 

The risk is there that the battery may get warm so be careful if using the PAS 5 setting or throttle.

Seller doesn't know what he is selling or understanding the ratings.

 

The controller is 30a rated current, this will be the defacto current if throttle or PAS 5 is used, yes the current can be dialled back but so will the bike performance esp climbing. The 15a rated current is only if you want a tame/limp bike using those 1000w DD hubs.

The battery is a 20a continuous rating, the upper rating 25/30a is only for brief 5 -10 second bursts typically but even this will stress the cells early reducing it's life.

 

The risk is there that the battery may get warm so be careful if using the PAS 5 setting or throttle.

Will do Nealh, and thank you for all your help. I continue to learn more every day. My Wife is disabled and only ever uses the throttle sparingly, and 99% of the time She's in PAS level 1. We did 30 miles on the new pack in hilly north Dorset at the weekend, before I dialled back C5 today. it performed brilliantly, and the pack did not get warm, very strange? But with all you guys have said on this subject I have taken the above measures ie: dialled down C5 to help the pack.

Again, many thanks

Daron