Fiido D21 battery issue

[stormfeet]

Hi! Has anybody with a Fiido experienced the following?

Normal behaviour:
1. Charger in unconnected state (charger's LED shows Green)
2. Connect the charger to battery (charger's LED goes Red)
3. When fully charged, Charger LED is green again.

In my bike, there seems to be an issue:
1. Charger in unconnected state (charger's LED shows Green)
2. Connect the charger to battery (charger's LED goes Red > for 2 seconds > then it goes green again)
3. After having been connected for 4 hours, there is still no charge on the battery at all.

It's just a couple of months beyond the 12 month battery warranty

Is there any fix I can do that avoids buying new battery?

 

[Nealh]

Battery is either fully charged or it has a fault , the fault could be a low voltage cell group or a faulty BMS.
First you need to check the battery discharge voltage with a meter and tell us the result.

As it is under warranty then affect a claim to the vendor of the bike where it was bought from, after the warranty period we can likely help you sort out the issue.

 

[Nealh]

Red charge turning to green means the battery is charged , though if it isn't the case then the BMS has detected a fault. A fault can only be rectified by opening the battery and making some checks but as under warranty at the mo it will be voided if you do so. So simply as above post make a warranty claim.

 

[cyclebuddy]

The behaviour (2) suggests the battery is already fully charged. As Neal says, you first need to measure/check the battery voltage is okay.

 

[stormfeet]

Thank you for the advice. The bike was purchased from a local vendor which has since closed shop, they couldn't compete with manufacturer's direct sales...

Fiido support have come back saying it's out of warranty, but suggested some tests.

As the battery doesn't power on at all (pressing the button on the batter itself, not connected to the bike), they suggested checking the 2 wires going to the button, and if the fuse might be blown.
I'll get a voltmeter and test it this weekend, fingers crossed!

 

[Nealh]

First check the output voltage .

Just a few examples of what one might see.
If 41.5v - 42v for a36v battery thenit is fully charged.
If 0v then likely a blown fuse .
If only a residual very low voltage then BMS in sleep mode or detects a fault.

As the battery is said to be out of warranty then with our help we can guide you with steps to open and check the battery pack.

 

[stormfeet]

If it's any help, here's a preliminary test we did, that we sent to Fiido before they replied sayingto open it up:
D21 battery Test

 

[Nealh]

The 2.2v reading initially suggets the BMS doesn't switch on , unlikely to be a switch issue so you will need to remove the battery and open it to take a voltage reading direct off the battery pack and directly off the BMS connection. As well as those 10 individual cell readings off the sense connector pins.

With luck your worse case scenario is a poor dry solder or wire connection issue or simply a duff BMS that needs replacing.
I can't see it being a low cell group at this stage with a 2.2v reading, though unitl the battery is opened we won't know for sure.

With my LG hg2 bottle battery I had the same issue twice, both times the Daly BMS gave a discharge reading of only 3v or so, pack voltage was generall ok but slightly unbalanced due to the BMS. I binned the BMS and now won't buy Daly brand again as they are proving unreliable as is also borne out on ES forum.

 

[stormfeet]

out of interest, where can a BMS be ordered, if the issue is that?

 

[Nealh]

Ebay or aliexp £10 - £20 depending on the quality, yours has sw option so if one is needed buy one with the sw wires.

 

[stormfeet]

We opened the cover! (total novices)

Fiido says to check the fuse, and in their videos, the fuse is a very obvious blade-fuse thing on the red cable.

2 things we noticed:
1. My seatpost doesn't seem to have an obvious fuse like in their videos. The cables lead to some plastic-wrapped circuitboard. Maybe it's much deeper inside?
Should we try to pop the bottom cover, or from the top? Hesitant to force/break something

2. There seems to a slight burnt smell, but I have no idea if they are like that normally.

Photos attached. Grateful for advice

 

[cyclebuddy]

Looking at your pics, the insulation on one of the red/positive wires looks to me like it was starting to melt, which usually happens from sustained/abnormally high current. What were you doing to it?!!

I've not opened my own (D11 but identical), but at a guess I'd think if you disconnect the plugs at the top end and removed the 5 screws from the bottom of the battery post, the whole battery cluster/BMS might push through. Then at least you'd be able to see what is what to test the cell strings/examine the BMS as Neal suggested.

The 2.2v is normal when the battery is switched off by the way (mine measures that too).

 

[stormfeet]

Looking at your pics, the insulation on one of the red/positive wires looks to me like it was starting to melt, which usually happens from sustained/abnormally high current. What were you doing to it?!!

It was charged normally, nothing was ever done to it (hence my confusion)

Fiido have come back with: "Can you cut the two white wires and short them together?Because I h suspect that the on button of the battery is bad." quote unquote

 

[cyclebuddy]

Fiido have come back with: "Can you cut the two white wires and short them together?Because I h suspect that the on button of the battery is bad." quote unquote

If that's what Fiido advise, you've nothing to lose by trying. It's a non-latching push to make switch, so if the switch is faulty bridging those two wires only tells the BMS to turn on. (guessing the red wires illuminate the LED).

I suspect they may well have had problems with it before, because 1) they've made it available in their spares section and 2) it's now a metal bodied switch as below rather than the plastic body in both your pic and theirs. If that is your issue, the part is available here.

 

[stormfeet]

Just tested the switch:

video

Let's see what Fiido says next