Do i need a BMS for my lifepo4 battery?

[UNDERLORD]

can i use my battery without a bms and how do i charge it and make shure it is balanced properly when it is charged and how do i prevent it from getting overdischarged it is a 48v 20ah battery and i have a 1000watt hub motor setup on my bike i got from china and i ordered the battery from there too but it came and the bms and charger are dead but the battery works

 

[ddk]

 

[dnmun]

how do you know that the BMS and charger are dead? you cannot use a lifepo4 pack without the BMS to protect it or you will lose the pack.

can you post up pictures and who made that pack and BMS? do you have a voltmeter to measure voltages?

 

[auraslip]

see here -> https://sites.google.com/site/shelbyelectro/batteries/battery-management

 

[dogman dan]

You need a working bms. Definition of a working bms can be that you monitor the pack, and single cell charge low cells as needed. Much debate about what fails more often, cheap china bms, or humans watching packs. Both quite fallible.

Best approach tends to be both, Have a functioning bms, but monitor the pack anyway.

 

[ebent]

I have 48v 18ah LiFePo4. I do not have a BMS. My battery has taken me about 4000 miles so far and feels as pepy as new. I do not very often drain the battery. I have made several rides using 65 percent of AH. But mostly I use 20 or 30% between charges. Early I would check individual cells every few weeks. I stoped. Maybe it is the charger doing the job.

My guess is that if you have a large battery and use modest amounts between charging there is an improved probability of staying in balance. Knock on wood. On this subject intuition rather than absolute knowledge is at work.

Does Grin sell BMS's? The idea of needing one with inconsistant product performance creates a quandry.

 

[wesnewell]

can i use my battery without a bms and how do i charge it and make shure it is balanced properly when it is charged and how do i prevent it from getting overdischarged it is a 48v 20ah battery and i have a 1000watt hub motor setup on my bike i got from china and i ordered the battery from there too but it came and the bms and charger are dead but the battery works

Yes, you can use any battery pack without a bms. But, you must then monitor it yourself if you don't want to damage it. If all cells in your pack are equal. then in theory all you need to do is recharge the whole pack at once using a bulk charger set to the the max voltage of your pack. Assuming a 16s pack, that would be 16 times the fully charged voltage of your cell type. Or 58.4v for 3.65v cells. During the first few charges you should monitor the voltage of the cells to make sure they don't get too far out of balance. If they charge in balance good, then you can check it at random every few charges if you like. A better option would be to hook up a couple of those 8 cell balancers to your pack during charge. They make all kinds of cell monitors with alarms that go off when a cell gets to a set point. Those could also be used to monitor discharge so you don't over discharge the pack.

 

[BATFINK]

Buy yourself a cycle analyst and you can set it to cut off power from the battery as your battery reaches a certain lower voltage to protect it, also helps you keep an eye on what power you are using, speed etc.

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[BATFINK]

Cycle analyst http://www.ebikes.ca/drainbrain.shtml

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[dumbass]

Buy yourself a cycle analyst and you can set it to cut off power from the battery as your battery reaches a certain lower voltage to protect it, also helps you keep an eye on what power you are using, speed etc.

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That's great it the pack votage is low but does nothing for a low cell......

 

[dumbass]

I have 48v 18ah LiFePo4. I do not have a BMS. My battery has taken me about 4000 miles so far and feels as pepy as new. I do not very often drain the battery. I have made several rides using 65 percent of AH. But mostly I use 20 or 30% between charges. Early I would check individual cells every few weeks. I stoped. Maybe it is the charger doing the job.

My guess is that if you have a large battery and use modest amounts between charging there is an improved probability of staying in balance. Knock on wood. On this subject intuition rather than absolute knowledge is at work.

Does Grin sell BMS's? The idea of needing one with inconsistant product performance creates a quandry.

Many people think they can get away without any type of protection (including me at one time). For the most part you are correct in the fact that low discharge levels will generally protect you from a low cell problem. But it does nothing for you while charging. If you are bulk charging without cell protection you maybe over charging some of your cells. This is just as bad as over discharging them.

I learned my leason and now use CellLog8s to protect my packs from low and high voltage.
Bob

 

[UNDERLORD]

i would like to know if anyone knows how i could charge my 48v 20ah LiFePo4 Electric Bicycle Battery Rechargeable 18650 3.2V the charger they sent me from china dosent work and i am looking for a cheap easy way for me to charge my battery any ideas would be appreciated........ how could i make my own charger or could i build one from stuff i could buy at canadian tire?

 

[dnmun]

so you have a vpower pack that won't charge because the charger broke? it is the 5A charger? join the crowd.

 

[UNDERLORD]

how o how can i charge my battery???? anyone

 

[wesnewell]

Buy a 48v charger. ~$20 and up.

 

[dnmun]

usually $2.50 to fix it. i think i have sent out ICLs to repair about 12 now.

 

[Racer_X]

UNDERLORD, Get a ping battery next time, Ping sells LifePo4 battery plus stand alone chargers to go with them.
And he guarantees his products. Good luck

 

[Spacey]

No BMS is great until you realise that the one low cell never empties but......when charging it forces the fullest cell to hit 4.3v to make up the sum total of your charge input.

 

[wesnewell]

No BMS is great until you realise that the one low cell never empties but......when charging it forces the fullest cell to hit 4.3v to make up the sum total of your charge input.

And that's why you use a balance charger. So that doesn't happen if you don't use a bms. Hardly anyone uses a bms (other than the charger) with lipo batteries. I've also bulk charged lots of times without any problems. A pack with decently matched cells can be charged many times without a balancer as long as you don't over discharge it and get the cells way out of balance.

 

[UNDERLORD]

ok so i opened up my bms and looked inside and all my sence wires where unplugged inside my bms so i plugged them back in and my bike came to life......wooohoooo............ now i just need to be able to charge my battery but i dont have a 48volt charger and i cant find a 48volt charger in trhis stupid town i live in so how can i build my own charger or power supply to charge my battery??

 

[dnmun]

did you try charging the pack after you finally plugged in the sense wires? did you open the charger to see what burned up?

if the sense wires were disconnected, that may be reason the BMS would not let you charge it. we will never know.

 

[wesnewell]

48V chargers are a common general public item, so you'll probably have to order on line unless you have an electric bike shop in your town. ebay or one of the shops that sell the chargers.
http://www.ebay.com/sch/i.html?_nkw=lifepo4+48v&_sacat=48618&_odkw=lifepo4&_ipg=200&_sop=15&_osacat=48618&LH_PrefLoc=2

 

[UNDERLORD]

well i guess im guna have to order a charger on the slow boat from china ........ wait wait wait weeks for it and not be able to ride my bike till then .......... i just want to know a way i could charge my batteries till it gets here but i guess no one has any idea how i can do that on here so i guess i will stop asking and just figure out how to charge them myself the trial and error way.

some suggestions from people that have done it befor woulda been nice but i guess no one has any ideas on how to charge my battery till my charger gets here so i will stop asking

 

[wesnewell]

There's hundreds of ways to charge the battery if you want to go to the trouble of doing it. You could charge each serial group of 4 with a standard 12v charger. If you want a charger in a hurry try ebikessf or one of many other places that sell them in the US and Canada.

 

[UNDERLORD]

just wondering but could i take 4 12volt car battery chargers and paralel them together to get 48v and charge my battery like that for now till my charger gets here?