Wisper 905e cuts out for a few seconds when going up steep hills

[Malcolm Hall]

I hope someone can give me some advice, or a solution to my problem, when cycling up a steep hill, of which there are many in Sheffield ! if my speed drops below 9 mph, the power can often cut out for about 4 to five revolutions of the pedals. The battery is getting on a bit (4 - 5 years old, but it still manages to last for 12-14 miles on one charge) this problem doesn't seem to be related to the charge level, as it occurs at various states of charge.
This makes life difficult as you can imagine, it usually only occurs when I'm in 1st or 2nd gear consequently doing less than 9 mph, don't know if it occurs under throttle only, as I always pedal, anyway the hills are too steep for throttle only.

 

[Deleted member 4366]

You have what's known as knackered battery syndrome. Time for a new one, unfortunately.

 

[newboater]

that happens on mine ,and also a friends ,both bikes are just 1 year old

 

[Malcolm Hall]

You have what's known as knackered battery syndrome. Time for a new one, unfortunately.

Oh eck !! I was worried that might be the case, at over £500 for a new replacement, do you have any suggestions for a cheaper compatible alternative, can I change the cells in the existing battery ?

 

[the_killjoy]

As d8veh says under heavy load the voltage just sags, time for a new battery. Be cheaper not to get one from wisper - go for a rack mounted one.

 

[Deleted member 4366]

You can use any 36v battery you wsnt if you know how to join a couple of wires.

If you could take your battery out and photograph it to show how the slider that retains it, we might be able to find you a replacement. Try Wisper first. They might have relented on the price.

You could try rebalancing it in case that's all it is. It might work for the newer ones, but 4 or 5 years old is doubtful unless you didn't use it much. To check the balance, you have to ooen the case. Once pen, takes some photos of what's inside for further advice.

 

[Nealh]

As mentioned post some pics of the battery set up. Or If you are able to fit a new 09 usb battery like Woosh or Eclipse sell then the new mounting bracket comes with it they are approx £300.

 

[Malcolm Hall]

Thanks D8veh, here is a photo of the slider, and a separate one of the back of the battery to show where the slider locates. I'll try Wisper again, but replacements are still on their website at £544 for 16Ah (the 11Ah batteries at £469 are sold out)

 

[Nealh]

Is there room to retrofit a 09 usb battery in place of your old one, it needs a space of 385mm x 135mm in depth to be able to fit and remove the battery with the fitting in place. Other wise reposition one on the down tube though not 16ah a 14.5ah one is available which has good 50-60mile range on the flat.

 

[newboater]

sorry to hijack this thread but can it really be batteries that are under 1 year old like ours

 

[flecc]

sorry to hijack this thread but can it really be batteries that are under 1 year old like ours

But what bikes? Are they the same Wisper brand and model as the OP's? It's not unknown for batteries on some makes and models to fail much earlier under high loads.
.

 

[Deleted member 4366]

If you get cutting outblike that on hills, the most likely reason is a probkem with tge battery cells, but there are other reasons like: bad connection at tge battery terminals; bad soldering on the key switch; bad soldering on the BMS; bad soldering on the battery wires anywhere else; faulty key switch; faulty BMS. OP's battery is old, so the probability of bad cells is high, and the probability of bad soldering or faulty BMS is low.

Some batteries power the BMS from cell 1, so if you don't use it for a while, cell 1 will be lower than the others, which compromises capacity and power output. The only way to know if you have this problem is to open up the battery and check the individual cell voltages.

 

[newboater]

But what bikes? Are they the same Wisper brand and model as the OP's? It's not unknown for batteries on some makes and models to fail much earlier under high loads.
.

they are both wisper 705 classics

 

[Deleted member 4366]

Are they not guaranteed?

 

[flecc]

The Classic uses the same 37 volt 11 or 16 Ah battery as others in their range and I think both bike and battery have a two year warranty, much longer on some items like the frame.
.

 

[Malcolm Hall]

I've managed to open my battery case, here are some photos of the inside,
I would say the soldered connections I can see are pretty reasonable.
I've measured the battery dimensions, 100mm wide 110mm deep (but at a push could possibly squeeze 120mm into the frame in this area), the battery is 300 mm high, but as it is under the saddle, I could manage up-to another 80-100 mm for a taller battery. So I suppose a 09 USB is not possible in the same space. I couldn't see a BMS but didn't undo all the packing and sticky tape, perhaps this is located under the battery in the case on the bike frame, I suppose this is where the motor controller is ?

 

[patpatbut]

I fixed the exactly the same battery for my friend.

The BMS is hidden at the top of wires. Remove the tape carefully to reveal them. Check the voltage for each cell and charge it individually.

Pat

 

[Deleted member 4366]

You have to peel back the blue covering at the top of the battery to reveal the multi-pin connector on the BMS.

 

[Pharisee]

I have a 905se that uses the same batteries (14Ah). I bought a second battery when I bought the bike as I often cycle from my home in Bedfordshire to Bookham in Surrey. On a realistic 'road trip' like that I only get a usable range of about 30-35 miles per battery (medium power assist and pedalling all the time) so I needed two. My bike occasionally 'hesitates' for about a second or so as the motor stops driving... certainly not for 4 seconds, thought. It does this with both batteries and has done from new. One battery failed completely after a couple of months and was replaced under warranty. The bike had the same problem with the replacement battery. The complete rear wheel / motor assembly has been replaced under warranty as has the motor controller and pedal sensor in an attempt to cure the problem but it still exists. I've come to accept that it's something I'm not going to cure and have learned to live with it. The bike is 4.1/2 years old now but the batteries still seem to have the same capacity as they did when new. They are kept fully charged and are charged immediately after use. I think that important if you want your batteries to last.

 

[newboater]

those are the exact symptoms of mine ,just hope one day i am not 30miles from home when it happens. perhaps wisper can come up with an answer