A2B battery help needed

alfgar

100 mW
Joined
Mar 18, 2017
Messages
41
My first post so I apologize if I’m in the wrong place ....and for the length of the post as well.

I recently purchased an A2B metro as a project bike. The person I bought it from had a Velocity and a Metro. He had only one auxiliary B battery which he shared between the two bikes.

He said he purchased the Metro from a Motorcycle dealer without the main "A" frame battery inside but it did have an auxiliary "B" battery until it began working intermittently and then not at all. When the Metro’s "B" battery stopped working completely he began sharing the "B" battery from the Velocity for both bikes.

Before buying the Metro this week, I tried it with the Velocity "B" battery and the Metro worked fine. He also had the Metro’s original "B" battery that stopped working 2 years earlier so I took it as well.

When i got home, I plugged in the Metro’s original "B" battery. Charger light was yellow for 2-3 hours then went green.

Surprisingly I measure 40-41 volts with my analog volt meter (on the yellow female connector of the B battery) but the bike still does not run when the battery was plugged in. Again, the bike worked with the Velocities "B" battery just a few days ago.

As an added surprise, I removed the black cap where the main A battery should be and it does have the internal main battery inside. But when I plugin the charger directly on the bike frame, the light turns green immediately. Well, yellow for about 2-3 seconds and then straight to green.

Note: I am somewhat handy but very new to electric bikes

Basically, what are my next steps per battery....(or should I start a different tread per battery.)

Tks in advance and sorry again for the length.
 
Did you check the voltage on the internal A battery? it might be salvagable. It's possible the charger is reading a lower than average voltage as a wrong battery type. A 36V pack would not charge on a smart 48V charger.

There have been times when a builder took a very low battery, and charged it on a dumb charger at a very low amp-rate. Sometimes it works, but sometimes the battery is just too far gone.

https://endless-sphere.com/forums/viewtopic.php?f=14&t=70581#p1136005
 
Again really new at this...but When i reached into the frame and put my voltmeter onto the "A" battery...it didn't register any voltage. Not even sure if I'm putting the meter onto the correct terminals of the battery TBH....I used the Red and Black terminals of the battery....seemed logical, to me anyways.
 
The internal battery has a BMS with protection circuitry that prevents charge or discharge if some of the cells go out of balance too far (it happens)
It may be possible to track down and fix the problem (replace the cells or just manual rebalance). But you will need to remove the pack and break it open...not a task for the inexperienced.
I take it you are using the key switch to swap between battery packs ?
And i thought the Velociti B pack had an additional external switch comared to the Metro B pack ?
The external B pack that wont work , may well have a similar problem, needing to be internally checked for individual cell condition.
There are threads on this forum detailing the repair of these packs.
Where are you located ?
 
"If it was me"...I would gently gut the internal A pack, to see if the cells are salvageable or not. Its true that if you tested the red/black connectors to the BMS, then the "gatekeeper" might not allow any voltage to pass from the cells to the outside world. IF...you charge the cells at a low rate, the pack might recover, and the BMS "might" start working again (do you feel lucky?).

If the pack is beyond dead, toss it (using the proper disposal regime) to save weight. If it regains useful power, make a wooden cover and mount it on the cargo rack until it dies, while you plan your next move.
 
spinningmagnets said:
"If it was me"...I would gently gut the internal A pack, to see if the cells are salvageable or not. Its true that if you tested the red/black connectors to the BMS, then the "gatekeeper" might not allow any voltage to pass from the cells to the outside world. IF...you charge the cells at a low rate, the pack might recover, and the BMS "might" start working again (do you feel lucky?).
.
The A2b internal BMS also prevents charging via the normal external charge port if the pack voltage is too low or out of balance.
You would have to bypass the Bms with a charge connection direct to the cells to try to revive it.
Bottom line is you have to remove the pack and break open the covers.
Tricky, but it can be done with care.
 
Good morning and thanks for all the quick responses everyone.

Apparently I’m not as adapt with the search feather as you younger folks but I should be able to follow instructions to links anyone may have.

As to your comments:

- “you will need to remove the pack and break it open.” : Are their instruction on here on how to break open the internal “A” battery pack?

- “I would gently gut the internal A pack, to see if the cells are salvageable or not.” : How would I do that? Do I need a digital meter? Do I measure the voltage per cell on each end without breaking any connection, etc?

- “IF...you charge the cells at a low rate, the pack might recover, and the BMS "might" start working again” : How would I do that, and yep.... I feel a little lucky. Also if I can save the “A” battery, why would I make a wooden crate. Can’t I just close the pack (with black electric tape or with shrink) and just put it back in the frame.

- “...bypass the BMS with a charge connection direct to the cells to try to revive it...” : Basically how do I do this? Do I charge each cell one by one for example.


As to the “B” battery. Again, the battery seem to charge normally for a few hours before the charger light went greem and at the yellow battery femal connector, I do measure around 40 volts.

This is only when I turn the “B” battery on with the power button beside the 3 pin connector on the other side of the “B” battery. Why am I measuing voltage (40 V) and yet the bike won’t work.

I doubt it’s the bike as it works well when connect with the Velocities “B” battery.


Tls again everyone.
 
breaking the pack open once out of the frame ( thats not always easy as its a tight fit) is a matter of several screws and a load of adhesive holding two halves of the pack casing together.
cels are assembled in groups of 4 in parallel and 10 in series, so first test each parallel group to see if all 10 are equal.
likely one or more is low so try charging just that one group first (4.2 volt single cell charge) to see if it will come up to the same voltage as the others.
if you have one group of 4 that wont hold a charge, you will then have to start breaking out single cells from the group for charging and testing .
be careful there are many angry little electrical Pixies in there waiting to bite you ! :lol:
 
Took me all this time to get the @#@#% internal battery out. It was really stuck in there and no matter how slow and steady I pulled it wouldn’t budge. Plastics straps beside the battery broke after a while.

Ended up fishing a guitar wire through the open holes of the battery case and heated up (very gradually) the bike frame with a heat gun expanding the frame just enough to yank out the battery. And it still took quite a pull to get it out.

Hillhater

***Any links on how to charge a group of cells or individual cell?

Do I just connect a charger, matching the voltage of the group, or individual cell if I go individually?

Do I need to disconnect the group or individual cell from the pack when charging either way I go....


tks again for all your help
 
If you have the pack casing split open, you should be able to identify the individual paralell groups.
Check each group voltage first , looking for any low voltage (<3v) groups.
You can then try charging individual low voltage groups simply by connecting a single cell voltage (4.2v) charger across that group. No need to disconnect any of the group series connections.
 
alfgar said:
Took me all this time to get the @#@#% internal battery out. It was really stuck in there and no matter how slow and steady I pulled it wouldn’t budge. Plastics straps beside the battery broke after a while.

Ended up fishing a guitar wire through the open holes of the battery case and heated up (very gradually) the bike frame with a heat gun expanding the frame just enough to yank out the battery. And it still took quite a pull to get it out.

Hillhater

***Any links on how to charge a group of cells or individual cell?

Do I just connect a charger, matching the voltage of the group, or individual cell if I go individually?

Do I need to disconnect the group or individual cell from the pack when charging either way I go....


tks again for all your help

Welcome to A2B metro ownership, I had the same experience removing the A battery from my 2010 A2B and found that brute force combined with unseemly and profane incantations was the solution to the problem. When reason and finesse fail, brute force and ignorance will solve all stubborn mechanical problems in my experience. Of course brute force and ignorance often is the cause of the problem so it is a matter of fighting fire with fire. In the case of the A2B it was the lousy design that made the "A" battery impossible to remove easily that qualifies it for the "ignorance" label.

You don't need to remove the cell group to charge but you should use a lithium charger in preference to a fixed voltage supply. A cheap and cheerful iMax B6 can be had for less than $20 provided you have a suitable power supply to power it and if you don't you can press an ATX power supply scavenged from an old PC into service. In all likelihood even if you are able to recover a cell group you will find that due to age and low state of charge the internal resistance of the cell group will be so high that the BMS will cut out under modest load due to the cell group voltage dropping below the 3V cutoff. If all the cell groups voltages are ok you may have to reset the BMS. On the "A" battery BMS there is a reset switch in front of the socket that the balance wires plug into, a single press will reset the BMS. There is also an automotive fuse plugged into the top side of the BMS board so it would be wise to check that too. Good luck.
 
Once you have the pack out, look for the BMS board (follow the wires). You can measure the cell voltages on the connector if you use some real skinny wires (be very careful not to short anything). That will tell you a lot.

Charging the pack at very low current (<50ma) is a good idea if the cells are below the cutoff voltage. Once they get up to around 3.0v, you can increase the current. Since the BMS is preventing charge and discharge, you need to bypass it with the charger connections so you go straight to the pack. Once all the cells get over the cutoff voltage, it should charge through the BMS like normal.

I have one in the same state but haven't gotten around to extracting it yet. I plan to replace all the cells with new ones.

BMS board removed:
A2B BMS Board 1.jpg

Other side:

A2B BMS Board 2.jpg
 
fechter said:
Once you have the pack out, look for the BMS board (follow the wires). You can measure the cell voltages on the connector if you use some real skinny wires (be very careful not to short anything). That will tell you a lot.

Charging the pack at very low current (<50ma) is a good idea if the cells are below the cutoff voltage. Once they get up to around 3.0v, you can increase the current. Since the BMS is preventing charge and discharge, you need to bypass it with the charger connections so you go straight to the pack. Once all the cells get over the cutoff voltage, it should charge through the BMS like normal.

I have one in the same state but haven't gotten around to extracting it yet. I plan to replace all the cells with new ones.

BMS board removed:
View attachment 1

Other side:


Fechter, is that an A or B BMS?
It looks similar to my "B" but different and both quite a bit larger than the "A" BMS in my A2B.
 
Tks for the great responses again. Although I will need to research a little more as to some of the basics details you guys are offering. I think I can pick up rather quick but all of this is still very new to me right now...

I guess once I open up the battery I’ll get a better idea as to how to “bypass” the BMS, and measuring the cell voltage.

Prognosis doesn’t look to good as I’m only getting a .8 volts when I measure at the terminals that connect to the BMS.

Also, if anyone has any ideas as to why my “B” battery charges, measuring 41 volts at the yellow connector but yet the bike doesn’t work when connected to it....The bike works well when another B battery from a Velocity is connected.
 
alfgar said:
Also, if anyone has any ideas as to why my “B” battery charges, measuring 41 volts at the yellow connector but yet the bike doesn’t work when connected to it....The bike works well when another B battery from a Velocity is connected.

That's probably a bad sign. The voltage looks normal but it must be tripping under load. Could be the cells are sagging so much they trip the low voltage cutoff. I would find a way to put a medium load on it while measuring the voltage. Something that will draw around 5A or less. I have big resistors, but have used light bulbs and hair dryers before.

I don't know where the BMS in the picture came from as it was already removed when I got it. I'm sure the other one is similar in function.
 
fechter said:
alfgar said:
I would find a way to put a medium load on it while measuring the voltage. Something that will draw around 5A or less. I have big resistors, but have used light bulbs and hair dryers before.

Wouldn't I need an inverter for a hair dryers or bulbs connected to a DC source? Sorry for my stupid question as it seems like one :? .

But I do believe I have a 36v 500 watt motor from an old e-scooter around in my garage...mind you if I remember my high school electronic, from a few lifetimes ago, that is considerably more than a 5A load.

Regardless of the load I use, if the load doesn't work when connected to the battery, am I looking at changing the cells out basically?
 
My hair dryer will work on DC. Most will but the on/off switch doesn't like it so I just leave it on and unplug it to turn it off.

The 500W motor will be a good load. With nothing connected to the shaft, the current draw will be much less than 500W.

If the pack won't power that, either the cells are bad or there is a problem with the BMS.
 
Went ahead and connected the motor and the voltage went from 41v straight to 0 as soon as I pushed the button on the B battery.

Also , the “on” button of the battery that glows blue when there is no load, was no longer blue when I connect the motor.

The motor would “sputter” for a split second every minute or so but that’s it...

As soon as I removed the motor, I again could measure 41V and the battery “on” button glowed blue again.
 
Good test.

Kind of strange. Seems almost like a bad connection somewhere. I'd try opening up the battery and see if maybe there is just a loose connection in there. Un plug and re-plug everything and check any screw terminals for tightness.

Could also be the cells are totally shot. If you had a way to measure individual cell voltages when loading it, you could tell for sure.
 
Hope it’s as simple as a loose connection, going to be pretty busy for the next few weeks so it will need to wait a while.

But I did get a chance to breakdown the main “A” battery and took some readings.

As a reminder, the bike came from a Harley dealer who had it sitting in the show room and the battery probably was never charged …..The battery case has “2009.04” on it so I figure it’s around 8 years old.

These are the readings I got with my volt meter.:

At each cell pack that I measured I got .14V / .15 volts

At most all individual cells, I measured .14 V / .15 V although there was one at .19V and another at .12V

At the “big” black and white wires from the battery pack to the BMS board, I got 1.45 volts.

At the red and black terminal that go from the BMS to the bike connector, I measured 1.15v. Interestingly enough, the longer I left my voltmeter there, the more the voltage counted down incrementally: 1.15V then 1.10V……. .80V, .79V and so on for as long as I had the meter on it. ?????

Been researching how to rebuild a new battery pack and it seems easy enough if the BMS and the battery cases, of both batteries, are salvageable. But I will need to invest in tools I will probably never use again.

At this point I will need to think about the value added advantages of just paying someone to do the repairs and begin to enjoy the bike or dive in with both feet and begin a new hobby.
 
Those are some pretty low voltages. Explains the problem.

I've had good results with reviving cells in that condition. Low current charge for a long time to get them up into the healthy range followed by normal charging. At 25-50mA, it may take several hours to get up to 3.0v

If the bike sits too long without being charged, the BMS board slowly drains them below the point where the BMS enables charging. It gets stuck there since you can't charge it. Bypassing the BMS board and going straight to the cells is needed to "jump start" the pack.

Cells can be damaged by the low voltage condition too, so extra caution is advised when charging.

Replacing all the cells with new ones is the best solution if you can afford it. I've seen new packs for these things go for something like $800. Ouch, no thanks. You could use upgraded cells for better-than-new performance.
 
i already rebuild a A2B frame pack and the bms looks just like a simpel one...no reset option/button.
 
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