Basic noob battery questions.

[Callmenobody]

Well, this is all new to me so I hope that I don't ask those annoying questions everyone starts with (I have googled).

Sooo, my in-laws electric IKEA bike broke down and their No1 solution it to leave it at my doorstep and ask me to fix it. No matter what it is.
I removed the battery and noticed that the plastic around the positive connector was melted but since the fuses where ok I guessed that this was due to a bad connection generating heat. So I just opened the battery to check the cells and that everything look ok, then I cut the melted plastic away and plugged the battery back in.
All worked like a dream for a few months but after leaving the bike outside a while during this winter it is quite dead.

The indicator on the battery doesn't light up and I get no voltage between the positive rail and ground.
If I open the battery up and measure the cells they seem to be alright and if I plug the charger directly to the bikes control box (or whatever it is called) the bike lights up.

So I guess that the PCB in the battery is fried.

Now to the question (I like to explain the story behind the problem).
Can I just order a aftermarket 36V xxA battery of a Chinese site and plug it in and get the bike working again? The original battery only has a positive and a negative going to the box so I can't see why not.

As long as the cells fits in the original plastic box that is.

 

[e-beach]

Hi Callmenobody , Welcome to ES where you will never get a yes or no answer. :lol:

Except to say, no, you can not just get any battery and make it work. You need to know the amp draw of the old system and you didn't give us the type of chemistry the old battery is. I could give you a better answer except you haven't given us much to go on.

Q's: Do you have a make and model of the bike? The battery chemistry? Any links to specs on the bike?

Can you post a clear and in focus picture or two of what you have? (just keep the file size under 512k for easy posting)

If you give us a little more info we might be able to help you out.

 

[Callmenobody]

Ah, of course.
I'll get back to you tomorrow with information regarding the battery.
I had it opened earlier today but forgot to take notes.

Scratch that! Just remembered something....

This is it!

http://thebatterydoctor.eu/documentation/protanium/

 

[goatman]

you checked both of those fuses?

 

[Callmenobody]

Yes, even with a DMM to be sure

 

[amberwolf]

All worked like a dream for a few months but after leaving the bike outside a while during this winter it is quite dead.

The indicator on the battery doesn't light up and I get no voltage between the positive rail and ground.
If I open the battery up and measure the cells they seem to be alright and if I plug the charger directly to the bikes control box (or whatever it is called) the bike lights up.

So I guess that the PCB in the battery is fried.

By "the cells seem to be alright", what exact voltages do each of them read?

If any are below about 3V or so, the BMS has probably shut the pack output off to prevent overdischarge of the cells.

If they do not recharge leaving the charger on there, then the BMS has also shut off the input to the pack to prevent a potential fire.


If the cells are all well above 3v, then the BMS may have water damage, and need to be replaced. If so, then whether that is easy or hard depends on the bike design.

If it does not have anything ohter than the main + and - connections for the pack to the bike, then it will probably be standard parts. If it has a main + and - conneciton, and also other smaller connections (not for the charger), then it would probably be OEM parts only available thru Ikea (or whoever made it for them).

Same goes for the battery as a whole.

 

[Callmenobody]

I didn't take notes but all a good bit over 3v and it doesn't charge, at least it doesn't indicate that it does.

Parts through IKEA I think I can forget. A new battery from another bike brand is to expensive, over $300 and the bike is not worth it.

 

[amberwolf]

If the cells are all good, and the bike powers up with the charger plugged into the port, then one more question.

Is the charging port the same port as the discharge port? Or is it a separate port?


If it is the same port, then the charger can turn on the bike evne if the BMS is completely nonfunctional, because the cahrger is effectively wired "past" the battery, directly to the bike, and does not have to pass thru any part of the battery to operate.

If the charge plug is on the bike itself rather than the battery casing, it also means there doessn't have to be any connection to the bike from teh battery. This means the connection itself where battery plugs into bike could be damaged, corrosion on contacts, for instance, etc, especially around the area where plastic had to be cut away due to melting. If that's the case, then replacing the connector between bike and battery (or evne hardwiring it) would fix the problem.


It also means the BMS could have failed internally, which then also means that you could replace just the BMS with any of them that can supply enough current for the bike (probably 20A or less?), and is made for the correct number of cells in series. (10s) But I'd work out a guaranteed-good connection from battery to bike before worrying about that.

If it is a separate port, then it must pass thru the battery (BMS anyway), first the charge FETs and then the discharge FETs, to reach the bike. This means that the BMS would have to be functional, and that all the connections from the battery to the bike are good as well...but the BMS is turned off when the charger is not connected. In this case, it depends on the BMS's power source for what the failure mode might be.

If it's powered by the whole pack, it means that the positive main connection from batery to BMS is the most likely failure point, or perhaps the negative main conection. This could be the wire itself at either end or anywhere between, or it could be an onboard fuse on the BMS itself.

If it's powered only by a subset of cells toward the most negative end of the pack, then the balance wire to the most positive of those cells may be broken, again at either end or anywhere between.

It could also be that the entire connector for the balance wires is either not fully plugged in, or is corroded from water intrusion, which effectively does the same thing.

 

[Callmenobody]

I am sorry for the late reply, I really appreciate all the help.
Family got in the way.

I removed the battery and did some research.
The charger port is on the battery itself.

With the battery removed completely:
1. The battery measures just below 36V with a DMM on the connectors to the control box, but I forgot to use a dummy load.
2. The charging indicator doesn't light up if I connect the charger to the battery.
3. The battery connects to the bikes control box with two wires, red and black (positive and zero I guess).
4. Connecting the charger only directly to control box lights the bike up.

With battery connected:
1. After some rest the back-lit display flickers once and then goes black.
2. No power in the bike except for above point.
3. No power to the bike if charger connected to battery.