Strange performance from new ebike kit

[cosmicman]

Hi all - perhaps someone could help clear up a problem I have ??

I recently bought a 36v 750 Watt ebike kit off ebay - got 3 x 12v SLA batteries at 12ah each and wired in series for 36v.

After fully charging I set off down the road and about every 20 seconds the bike stalls for a few seconds and then continues. Its been doing it the whole time I ride the bike (had it a week now) . At 1st I thought my motor blushless hub was changing gears or something, but it is a gearless hub I have so it must be something else.

The motor pulls for 20 seconds, stops for 5 seconds and then pulls for another 20 seconds - and so on and so on. I'm getting 25 mph + out of it, but it stalling about 4 times before getting to this speed and then even stalls momentarily whilst at that speed.

Has anybody any ideas why this might be happening ?

Any help would be appreciated as its driving me nuts!

Tony

 

[torker]

Do you know what brand the motor is? Is it new or used? Does it cut out under part throttle or only when wide open?

Welcome btw

 

[cosmicman]

Here's the picture its a new kit off ebay I got.

It's actually only when I have the throttle at full it happens, when I accelerate, or mentain full top speed - I do both most the time I'm on the bike.

 

[torker]

If it only happens at full throttle it sounds like the lvc "low voltage cuttoff" in the controller may be your problem. Others on here will probably know that motor controller combo just by seeing that pic. Otherwise I would check voltage. It should be 40 volts even after a short ride. Check all your connections between those batteries and use at least 12 ga. wire. Plus check all the connectors to make sure all the pins/contacts are straight and making good connection.

 

[cosmicman]

I think I will solder the battery connections and upgrade the battery wire, as I am using 240v lamp cable wire at the moment.

I'll see if that makes any difference.

Thanks for the recommendations.

 

[torker]

Yea that should help as lamp cable is usually only 16 or 18 ga. A bit too small .. let us know how it works. And if you don't have any 12 ga. around just double it up and use both sides of that lamp cord for a jumper.

 

[DerekG]

At rest after use a 36V SLA pack will read around 38-39 volts. 40 is a bit high unless you just too them off the charger. Fully charged the pack should be 40.5 volts. 13.5 volts is the ideal standby/float charge for good reason... ideal voltage between sulfation (too low voltage) and positive plate corrosion (too high voltage)

As mentioned before good chance the higher gauge wire = more resistance = more of a voltage drop which may trigger LVC although it happening in predictable intervals is a little odd.

 

[cosmicman]

Just an update..

After replacing the wire connecting the batteries with some 30 AMP cable the problem vansished!

Thanks for the suggestions!

 

[torker]

Awesome !!