something gone funny with my ebike battery. help please..

Electrically assisted bikes, trikes, etc.
paddycork
Posts: 4
Joined: 11 Jul 2019, 7:17pm

something gone funny with my ebike battery. help please..

Postby paddycork » 11 Jul 2019, 7:20pm

hello, i just bought a second hand carerra crossfire e bike. it didnt have the charger, the guy couldnt find it so i have just bought a new one from cycle republic

https://www.cyclerepublic.com/chg-vp-e- ... arger.html


Before charging the voltage was reading around 31v. i plugged in charger and it was charging away and i checked the voltage periodically ( i think it was 39.5 last time i checked) and it was rising. just before going to bed i plugged it out and checked the voltage again and it was 20.4v,

I have just taken it apart today and tested the batteries and they are all reading 4v in their series connections.. any ideas cause im stuck and frustrated!

thanks

paddy

hemo
Posts: 397
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: something gone funny with my ebike battery. help please..

Postby hemo » 11 Jul 2019, 10:37pm

Do all 10 parallel groups of cells each measure 4v ?
You should see a fill charge being in the range 41.5v - 42v.

A faulty voltage reading if batteries groups are all the same may indicate that your DVM needs a new battery it self.

paddycork
Posts: 4
Joined: 11 Jul 2019, 7:17pm

Re: something gone funny with my ebike battery. help please..

Postby paddycork » 13 Jul 2019, 1:58pm

hello. yes they are all 4v and it reads 41v across them all on the batteries.. what is a dvm?

thanks

stodd
Posts: 82
Joined: 6 Jun 2018, 10:24am

Re: something gone funny with my ebike battery. help please..

Postby stodd » 13 Jul 2019, 9:47pm

The DVM is your digital vold meter. The suggestion is that it may have a half dead battery and not be reading correctly.

hemo
Posts: 397
Joined: 16 Nov 2017, 5:40pm
Location: West Sussex

Re: something gone funny with my ebike battery. help please..

Postby hemo » 13 Jul 2019, 11:27pm

If the voltage reading doesn't change with a new dvm battery, then the fault is with battery packs bms.

kwackers
Posts: 13287
Joined: 4 Jun 2008, 9:29pm
Location: Warrington

Re: something gone funny with my ebike battery. help please..

Postby kwackers » 14 Jul 2019, 6:05pm

This might seem a bit obvious - but have you tried putting the battery on the bike?

It could simply be that the bms is designed to shut the battery off fully if it's charged and not connected to the bike.

paddycork
Posts: 4
Joined: 11 Jul 2019, 7:17pm

Re: something gone funny with my ebike battery. help please..

Postby paddycork » 14 Jul 2019, 7:43pm

ok thanks,.. this might sound a bit silly but is the dvm part of the bms or is it a seperate part.. when i open the battery i see the bms and the batteries are underneath. i think it might be that the bms is gone because when i look at it closely it looks like there is water damage to a section of it

i have tried putting the battery in the bike and nothing happens but it has been moved around alot recently in the back of the car so i also could have a loose connection somewhere!

stodd
Posts: 82
Joined: 6 Jun 2018, 10:24am

Re: something gone funny with my ebike battery. help please..

Postby stodd » 14 Jul 2019, 8:42pm

The digital voltmeter DVM is a separate device that will not be supplied with the bike. Check Amazon or ebay; anything from a bit under £10 up.

It is multipurpose and can be used for lots of electrical jobs around the house. If you are at all uncertain about them and what they do it might be better to get a friend to check things out. But looking back it sounds from your first post as if you do have a volt meter and know how to use it.

paddycork
Posts: 4
Joined: 11 Jul 2019, 7:17pm

Re: something gone funny with my ebike battery. help please..

Postby paddycork » 15 Jul 2019, 5:50pm

ok yes. i have a voltmeter and i know how to test voltage with it.. the voltmeter is fine.. it is looking likely something has gone wrong in the bms.. I am going to dend it to this guy and he will put in a new bms for me

https://www.ebay.co.uk/str/batterypoweruk.

I spoke to him on the phone and he seemed sound and reasonable so fingers crossed.