Golden motor BAC 281P controller

[Duncan C]

Hi,
I'm new to this forum and have introduced myself in the welcome forum.
I have a 250w 36v golden motor front drive conversion and it worked fine on Friday when I parked my bike. On Monday when I went to go to work it was dead. I have spent the last few evenings playing with a few things and now I am out of ideas. I'm pretty handy mechanically but electronics is witch craft to me.
My first thought was dodgy battery switch or connector as these have both caused trouble in the past.
I found a couple of loose wires so sorted them out thinking that I had found the problem. Unfortunately I haven't.
I have 38.6 v at the battery connectors to the controller. However when I connect the controller the voltage drops to 0.6v. I haven't left it connected for long but nothing gets hot or smells bad that I have found so far.
However I can't open the controller up yet as I have had to order some funky triangular screw driver bits to open the case. When that gets opened who knows what will have gone on.
If anybody has experienced this before and knows how to or if it is even possible to fix I'd be much obliged.

Thanks

Duncan

 

[Alan Quay]

For the battery to go to 0.6v (practically 0v) it must the BMS (Battery Management System) cutting it out.

When you measured 38v was that fully charged? It seems a bit low.

Possibly a duff cell, or it's out of balance.





Sent from my HTC One_M8 using Tapatalk

 

[Duncan C]

Hi, It was fully charged over Sunday night for riding to work on Monday. I didn't measure the voltage until Wednesday night as I didn't get a chance on Tuesday. The battery is less than a year old and I use the charger supplied by the battery seller.
If it is out of balance would a recharge possibly sort it out? or is it a replacement job?

Thanks

 

[Deleted member 4366]

Get your voltmeter out. Check the voltage on the charger. Charge the battery until the charger goes green, wait a few minutes and then measure the voltage on the battery terminals. Those two simple tests can show whether your battery is OK.

From what you've done so far, it would appear that the BMS is switching off because it's detected a problem in the battery, but that doesn't necessarily mean that the battery is bad.

Please show us a photo of your battery or a link to it.

 

[patpatbut]

Where do you live in Oxfordshire? If you live near me I might be able to help.

 

[Duncan C]

Hi, OK I've put the battery on charge and I was surprised at how long it took to charge considering that it hasn't been used since it was last charged.
The charger voltage was 43.8v and the battery after a couple of minutes off charge was 42.7v
Link to battery is http://www.ebay.co.uk/itm/Battery-for-electric-bicycle-e-bike-24V-36V-48V-10Ah-13Ah-LiFePO4-Li-MNC-/322058296525?var=&hash=item4afc2b9ccd.
I don't want to open the battery up as I only got it in October so if you think it is duff I'll see what the vendor says about fixing it.
Patpatbut, thanks for the offer I'm in East Hendred near Wantage. Hopefully if it is the battery I can get it fixed.

 

[Kuorider]

Looks like you got it from Harts cycles in Corstorphine Edinburgh or someone next door. Good blokes so you should be ok. You are much nearer Jimmy at Instat where the battery may have come from. If the vendor does not help, try Jimmy who will help you out.

 

[Deleted member 4366]

The charger voltage was 43.8v and the battery after a couple of minutes off charge was 42.7v
Link to battery is http://www.ebay.co.uk/itm/Battery-for-electric-bicycle-e-bike-24V-36V-48V-10Ah-13Ah-LiFePO4-Li-MNC-/322058296525?var=&hash=item4afc2b9ccd.

Can you remember which options you selected when you bought the battery?

Which shape battery is it?

A 43.8v charger is for LiFePO4 battery. Is yours LiFePO4?

 

[Duncan C]

d8veh, Yes LiFePO4, sorry I should have mentioned that but I didn't think of the battery having protection devices. The battery is the flat slide on to a plate on your bike rack kind. I'd post a picture but I haven't figured that out yet.
Interestingly I popped it back on charge last night and this morning the output voltage is 43.4v
Kuorider, Thanks for the information. If everybody is sure it is a battery problem then I'll contact them.

 

[Deleted member 4366]

43.4 volts is pretty good. it looks like you've got a healthy cell pack. The next thing to check is the the solder joints on the back of the key switch and on each of the kettle plugs/sockets, plus the bullet connectors between the kettle plug and the controller. The bullet connectors are the most likely culprits. Pull them apart, squeeze them down and then make sure they're pushed fully in.

 

[Duncan C]

Having got a good output voltage I decided to stick it all back together and see what happened. It works, which is great, however I don't know if I got a random poor charge on Sunday night or if remaking all the connections again for the umpteenth time today I miraculously fixed the one that was causing all the trouble. Still can't complain as it works again. A big thanks for the help and offers of support. If it hadn't been for you people I would have been chasing the controller as the issue not the battery. So THANK YOU very much.

 

[Kuorider]

Don't forget to check the brake lever switches. If the bike is ok one day and dead the next this is often the problem. Make sure that the levers are snapping back to the off position and operating the micro switches properly. A slightly slack cable and a floppy lever can cause what appears to be a major electrical fault.