do used prismatic cell from BH need balancement? what is the work and maintenance that i will have to do

[sharinginfos]

HI
i only want lifepo4 .
Battery hookup sell those used JD 3.2v 30ah 5c rated prismatic Lifepo4 cells or those for 5 dollar more

Lishen 3.2v 40ah Lifepo4 Prismatic 6C Power Cells - slight swell

These cells were all recovered from backup power units. These are rated for up to 6c (240a) discharge current. Specs are in the 2nd photo. QR codes are all in tact and not scratched off. Flange nuts are included. Some of these have a slight swell to them from being compressed under load but they...

batteryhookup.com

i like that i would save time not having to solder weld but what about the time required to build a pack and what is the maintenance to do with those and frequency.

I need to know in advance to avoid surprise.

do they need to be ballanced? how do i do that, is it a part i need to added wich ? is just a balancing bms enough?
Any yearly additional balancing to do ? how to ?

i ask that because at first i was going to choose used headway cells but people here told me headway require a lot of maintenance..

thank for clarifying

 

[j bjork]

Good quality cells with little (and equal) wear needs little if any balancing, also depending on the use. If used with high currents and down to very low soc it will need more. Low quality and worn cells will need more balancing. If bying used cells that hasnt been paired before, well then it probably is hard to tell before trying.

 

[sharinginfos]

. Low quality and worn cells will need more balancing. If bying used cells that hasnt been paired before, well then it probably is hard to tell before trying.

HI
when you say If used with high currents and down to very low soc it will need more how to we give more balancing? are you talking about leaving it longer on the charger? are you talking about having to disassembling them and then reassemble? are you talking about simply having to add a device that do active balancing?

when you look at BH prismatic cells used (some have slight sweel) what is the probable scenario. like im aware that the battery pack will only be using the capacity of the lowest capacity cell and that is ok since i dont need much AHours and will use it one a week no more.
What balancing would have to be done . just at the beginning or also once every years.

I looked at vids and the strategy seems to be full charge indivitually then do a capacity test . why is the capacity test usefull to do ?

 

[j bjork]

You balance by discharging the cells that are higher voltage than the others, until they are equal.
More balancing means you have to discharge more.. Either by longer balancing time or higher balancing current (or both).
How you do it is up to you, you probably will be using a bms? In that case you can start with the built in resistors and see if it is enough.
If not, you can add active balancers or manually balance with resistors or light bulbs. Or use a balancing charger.

A capacity test is useful to determine the health of the cells, and if you plan to have more parallel cells you can use the result to group them so you get similar total capacity in all the groups.

 

[calab]

get a 1s charger for manual balancing each 1s to equal voltages, measurements in voltages do fall so let them rest after a charge, before probing for a voltage measurement.

 

[sharinginfos]

You balance by discharging the cells that are higher voltage than the others, until they are equal.
More balancing means you have to discharge more.. Either by longer balancing time or higher balancing current (or both).
How you do it is up to you, you probably will be using a bms? In that case you can start with the built in resistors and see if it is enough.
If not, you can add active balancers or manually balance with resistors or light bulbs. Or use a balancing charger.

A capacity test is useful to determine the health of the cells, and if you plan to have more parallel cells you can use the result to group them so you get similar total capacity in all the groups.

HI i dont understand why you say that discharging them is needed.
from what i currently understand. when you receive the cells , you connect them im parallel, plug them in a power supply set it to 3.60 v and let that charge until the power supply does not imput more. you let them sit connected for a day or 2 and they are ready to be placed in series .
I intend to use a bms yes.

i dont intend to have multiple cell in parallel. it will be 16 s 1p . is capacity test usefull in that scenario?

one thing i ask myself if what i say above is right is how to spot a cell that is inadequate, broken or needs to be replaced. Because even if it is a bad cell, il will eventually reach 3.6v so how to undermask its inadequate quality?

 

[sharinginfos]

get a 1s charger for manual balancing each 1s to equal voltages, measurements in voltages do fall so let them rest after a charge, before probing for a voltage measurement.

HI what is the advantage of using a 1s charger vs what i have written in the last post? is it because a 1 s charger is cheaper than a power supply?.
By the way, i have a lot of time at home so time is not a limit for me money is.

 

[calab]

Connecting in parallel must be very close in voltage otherwise a surge happens and its not good.

1s charger is just an option, sometimes those balance chargers take a very long time to balance the pack, because the balance charger isnt powerful enough like those cheap 6s rc chargers dont have much discharge current, and mediocre charge current. Unlike an expensive iCharger that has higher current limits.

 

[sharinginfos]

Connecting in parallel must be very close in voltage otherwise a surge happens and its not good.

1s charger is just an option, sometimes those balance chargers take a very long time to balance the pack, because the balance charger isnt powerful enough like those cheap 6s rc chargers dont have much discharge current, and mediocre charge current. Unlike an expensive iCharger that has higher current limits.

HI calab ok so if i follow you instead of plugging them in parallel it is preferable to individually bring them to 3.4 or 3.5 v and then that is it you assemble them in parallele without charger to let the micro flow get them really at same voltage. then you can assemble them in serie with bms and use the pack . you are saying avoid directly putting them in parallel in case the voltage difference between voltage would be large and it would kind of shock the cells to have different neighbor voltage.?

so i would need 2 different charger . one that is 1s and another that is 16s. Or can one charger do both to avoid buying something that will only serve once? the first battery i would build would be around 10Amphour 48v lifepo4 . i imagine that having a charger that allow you to select the current and the pourcentage of charge you want to put in is important (80% 90% 100 pourcent?) what else is important ? maybe a smart charger that auto adjuste the curent making it smaller the closer it aproches the wanted voltage? you talk about a balancecharger that seem to be a a good idea of caracteristic to have on a charger too right. any sugestion of such a charger ?

In a video a guy said that it is not a good idea to charge them to 3.6 since it make the battery swell and instead to do the balancing at 3.4v(no compression needed) to prevent damage. what do you think about that?

would you happen to know the answer to this question: one thing i ask myself if what i say above is right is how to spot a cell that is inadequate, broken or needs to be replaced. Because even if it is a bad cell, il will eventually reach 3.6v so how to undermask its inadequate quality?

 

[calab]

I had too an epic day of riding, a little river bed riding with the low water levels but gorgeous views a nice sun beaming down with a cool light breeze, was all out of refreshments which is a mix of whey, for when the muscles pump when cycling. A cool young white tail buck with antlers and no fear. What am I saying? There are many ways to do things, that is a common saying. You get by with what you got, you broke then you buy a 1s charger, you rich you buy an iCharger (must do lp4) or Meanwell (cc/cv's works for li-ion) or a Meanwell clone.

A general warning is dont put batteries or cells in parallel without them being very close is voltage.
For a cell range 0.010-0.020, some go ~0.10-0.20, when your talking 3.60v or 3.40v
For a battery range, 36.00v to a 35.80v would be good, but not a 30v to a 36v parallel.

The surge comes from the Internal Restistances of each battery, the difference betweent he 2 causes the surge, the wider the gap in voltage between the two batteries (or cells) you will be connecting, the larger the surge, the greater the damage, and more heat, bad bad heat. It would be like charging the lesser battery at waaaaay above its C-charge max rate, like 5x or more. Maybe you could do the math, a little science experiment.

The other comment was just that you could use a 1s wall outlet charger, if the voltages were correct to charge up each 1s. It wouldnt really matter if the charger was set to 3.50 because all you need to do is have the voltages close, between the cells. Have them all within voltage range, connect them in parallel, the cells if your doing it that way. Series wouldnt really matter, but you'd want them close anyways, just do them all the same voltage. Individual cells now, not packs.

Using a single Meanwell set at a single voltage, to charge two batteries that you will parallel, just takes twice as lone as buying two Meanwells or any charger. BMS Battery sells chargers that you specify what you want and they make it. Go read what they are about if your interested.

 

[sharinginfos]

ok so i can parallel them at any voltage is what i understand from you message. could you tell me why in a lot of youtube vid they say charge them all to 3.65v?

could you provide a link of a cheap 1s charger as you say me not rich.

 

[sharinginfos]

anyone?