Battery BMS help, please

[Kingwouldbe]

Hello Endless Sphere,

This sight has been a great place to get help and I am in need again being a noob, I have no clue about battery's, so I bought the 48V 20 AH polymer li-ion lithium batter in a case, my friends asked me to get them the same battery, as mine worked great, so I bought 4 more.

Here is the problem, my battery go's almost twice as far, as the other 4, I contacted the seller he said check the BMS, that is way over my head, to send them back to china is not an option.

Where can I get someone to check and or fix the battery's, I will pay $, not looking for a freebe, just help.

Thank you so much for your help

David

http://www.ebay.com/itm/NEW-48V-20AH-Polymer-Li-ion-Lithium-Battery-Lockable-4-Electric-Bike-LIFEPO4-/231049911027?pt=US_Rechargeable_Batteries&hash=item35cba5daf3

 

[dnmun]

why would they say that? it produces power.

do you have a voltmeter and a wattmeter?

can you post up pictures of your battery with the end cap taken off and the BMS pulled out and exposed so we can see how it is built?

did you use the same charger to charge each of them and what was the pack voltage when the charger first went green?

 

[Kingwouldbe]

denmun, I don't know why, I have a voltage meeter 51V full charge, yes I can take some pic's give me a little time I'll take some pics.

I'm thinking, your thinking it's not the BMS.

They all fully charge, my first one just keeps going for about 6 mile climbs, all others only about 1-2 miles, then shuts off, I can turn the key off and it will go for a little while, then shuts off again, I can keep doing that until no juice, yet when I put it back on the charger, it charges in half the time, not the full 4 hours.

Let me get some pics

Thanks

 

[dnmun]

you will need to put a wattmeter or ammeter in the charging circuit to determine if the charger stops charging before the pack has balanced.

it does not sound like the BMS is bad, in fact it is functioning properly if it prevents you from over discharging the pack, but you will need to establish the storage capacity of all these packs also.

 

[Kingwouldbe]

Ok, I checked each battery they came in
54.7V my first battery and the best one
51V.
49V.
41V.
I can see now "Huston, we have a problem"

 

[wesnewell]

There's a couple of things that cause a battery with a bms to shut off.
1. A cell (or cell group) reaches the LVC voltage.
2. The amp draw from the controller exceeds the max amp draw of the bms.

A common problem is the battery pack is not left on the charger long enough for the cells to balance out. Thats' the easiest to test first because all it requires is leaving the pack on the charger for a day or two. If that doesn't fix it, then you have to start checking individual cells.
If it's a bms amp overload, then there's not much you can do about that except ease up on the throttle or get a controller that will not draw as many amps.
To make an educated guess as to your problem would require a lot more info, like each bikes motor system, including controller info like amp draw of each. But a wag is the packs are out of balance. Leave on charger a while to get them balanced.

 

[dnmun]

you really now justy need to figure out how to wire up an ammeter or wattmeter in the negative charging lead from your charger.

this is kinda the most valuable tool to have to diagnose battery malfunctions. it allows you to determine what stage of charging the battery is and you need to know if that charger just turns off when it reaches final voltage and does not push a balancing current.

you will get a lot of advice from people who know nothing about how a BMS works, just like the supplier, so be prepared for misleading tangents here too.

 

[Kingwouldbe]

Wesnewell,

I have checked each on my own bike which is a GNG mid motor 48V 450w.

I like the idea of leaving them on the charger to balance them out I/we may not have done that, taking them off right after the light go's green.

 

[Kingwouldbe]

you really now justy need to figure out how to wire up an ammeter or wattmeter in the negative charging lead from your charger.

this is kinda the most valuable tool to have to diagnose battery malfunctions. it allows you to determine what stage of charging the battery is and you need to know if that charger just turns off when it reaches final voltage and does not push a balancing current.

you will get a lot of advice from people who know nothing about how a BMS works, just like the supplier, so be prepared for misleading tangents here too.

Where might I find the information necessary to attach one

 

[dnmun]

i don't know if there is a book or utube. the wattmeter has a black wire that is the ground and a red wire for B+. you would insert the wattmeter, (or if you use the ammeter function on your DVM select 10A scale and reposition the negative lead to the 10A plug), into the negative wire from the charger.

sounds like you are newbie but if you have some skills then you can cut open or unsolder the wire on your BMS that goes to the C- spot on the BMS. that is where the charging current goes.

these batteries are all out of balance and you will have to charge them until they all reach the same voltage level at full charge and at that point the charging current will drop to about 60mA and remain there constantly once the pack has balanced as well as the BMS will allow.

balanced means each channel or cell has the same storage capacity as all the others so that when the battery is discharged they all reach the LVC voltage, meaning fully discharged, at the same time.

the only way to do this is to fully charge all the cells to full charge and then measure the amount of charge the battery can produce until it hits the LVC on the channel with the least capacity.

that's why you need a wattmeter and voltmeter as tools to diagnose and maintain the battery.

you can buy them on Ebay for cheap and they arrive in the mail, or you can buy a cycle analyst from justin and use it for diagnosing the battery and then mount it on the ebike so you have control and monitoring capabilities too.

but you can use just a wattmeter for now and even later on the bike.

my last order was for two of these from another seller: http://www.ebay.com/itm/Hot-130A-LCD-GT-Power-RC-Battery-Balance-Watt-Meter-Meter-Power-Analyzer-/181445701784?pt=LH_DefaultDomain_0&hash=item2a3f01b098

 

[Kingwouldbe]

dnmun, that is such great advice I will look on the utube to see if I can find ' how to" information.

I have them all on the charger right now, the green light is on but the fan is no-longer going on the charger, does it keep pumping a low current to balance all of the cells?

Yes Sir, I am a newbee, I only know enough to be dangerous, no seriously, vary dangerous.

Might there be someone who would be willing to do this job for me, I will pay for what it is worth, as long as they work.

 

[docnjoj]

Which company did you get the batteries from?
otherDoc

 

[wesnewell]

You can go through all this crap if you want to, but the easiest thing to do is just plug in the charger and let it charge. If the packs out of balance, which I'm sure they are, they will cycle on and off charging until they become balanced. That may take a few days if they are way out of balance. Your pack is 13s8p li ion, so final voltage should be ~54.6V.
BTW, that one at 41V is already below the typical LVC of a 48V controller which is 42V.

 

[Kingwouldbe]

Which company did you get the batteries from?
otherDoc

http://www.ebay.com/itm/NEW-48V-20AH-Po ... 35cba5daf3

 

[dnmun]

dnmun, that is such great advice I will look on the utube to see if I can find ' how to" information.

I have them all on the charger right now, the green light is on but the fan is no-longer going on the charger, does it keep pumping a low current to balance all of the cells?

Yes Sir, I am a newbee, I only know enough to be dangerous, no seriously, vary dangerous.

Might there be someone who would be willing to do this job for me, I will pay for what it is worth, as long as they work.

you have to learn to do this stuff to be able to maintain them. this battery should be able to carry you for at least 20 miles in LA so they are all outa balance and cutting out long before the capacity is used. the problem could be that the charger does not send the balancing current at the end of charge during the CV constant voltage part so the packs cannot balance unless you take the charger apart and remove the output latching board.

 

[Kingwouldbe]

dnmun, that is such great advice I will look on the utube to see if I can find ' how to" information.

I have them all on the charger right now, the green light is on but the fan is no-longer going on the charger, does it keep pumping a low current to balance all of the cells?

Yes Sir, I am a newbee, I only know enough to be dangerous, no seriously, vary dangerous.

Might there be someone who would be willing to do this job for me, I will pay for what it is worth, as long as they work.

you have to learn to do this stuff to be able to maintain them. this battery should be able to carry you for at least 20 miles in LA so they are all outa balance and cutting out long before the capacity is used. the problem could be that the charger does not send the balancing current at the end of charge during the CV constant voltage part so the packs cannot balance unless you take the charger apart and remove the output latching board.

dnmun, I almost spelt my drink...... I told you my friend " I- B- A- NEW- B....lol. I can only imagine what it must be like trying to help someone who has no knowledge of what your trying to tell them, ( take the charger apart and remove the output latching board ) would you like a side project.......

Seriously, I might have found a helping hand down here in so cal, we will see, I have taken my battery to 2 different shops only to tell them, just put it back together please. They had no clue what they where doing, & I have no clue, yet..... I knew they had none.

The Sphere is really like no other place I have been, I really mean this, I have learned so much and I still know nothing.

I have them on the charger all day we will see if they can get balanced, I will probable get a watt meter also.

I will keep you posted of what happens.

Thank you all for your help.
David