Dead bike

Adamantman

Just Joined
Nov 5, 2020
1
0
Hi,

I've had an electric bike for years, my first was a Giant 350w which I used to commute 4 miles a day on. I bought that 2nd hand and it started to weaken with the battery age and the cost of a new battery was more than I originally paid for the bike, so I sold it on. I then looked for a suitable replacement on ebay and found a 48v 1000w bike, kit built on a very good secondhand frame. It was a completely different bike to the first one and I loved it. Being able to go up hills without peddling was a dream. I used it for nearly a year in all weather's, then one very wet spell, it failed to work, perhaps it'd go 50 yards then die. I assume it must be a short somewhere. I also notice it won't recharge.
I'm no expert in bikes..i can change tyres and brakes but that's about all. So I've tried a couple of bike shops to have a look at what the problem is but they both refused point blank. So I'm at a loss as what to do. I suppose the only thing I can do is sell it to an enthusiast who would know how to fix it.
 

Benjahmin

Esteemed Pedelecer
Nov 10, 2014
2,590
1,747
70
West Wales
What you are suffering from sounds very much like voltage sag caused by current draw being supplied from a battery with ageing cells or cells incapable of delivering the maximum current.
A 1Kw motor is almost certainly a direct drive motor as opposed to a geared hub. DD motors, whilst being fast on the flat, are renowned for being highly inefficient at low speeds and during hill climbing. What this means is that they draw a high current (limited by the max current rating of the controller) but wasting a lot of it as heat rather than mechanical rotation.
So, starting off draws maximum current causing the battery voltage to sag, if it sags below around 31v then the low voltage cutoff (lvc) in the controller will cut in to protect the battery. This stops the current draw allowing battery voltage to recover and the whole thing starts again.
This is theory only at the moment and without more detailed specs it'd be difficult to give solutions
 

vfr400

Esteemed Pedelecer
Jun 12, 2011
9,822
3,993
Basildon
Show some photos of the whole bike and the various electrical parts, especially any control panels or switches.