BMS purchase for 14s lipo pack

[tenutso]

Yeah. first post! Hi everyone and thanks for letting me lurk this past year without a single post. I'm learning so much from this community and totally addicted.

I'm thinking of rolling the dice on this BMS.
http://www.aliexpress.com/item/14S-48V-LiMn2o4-and-NCM-battery-BMS-with-Balance-function-and-big-current-output-suitable-14S/1725402152.html

My current set up is 14s with hyperion balance charger and now a few people want me to help them with builds but I'm just not interested in explaining the balance, care and maintenance deal with anyone. I'd like to start building packs with a bms for both myself and others. One of my projects would be to retrofit a lipo set up on a 48v scooter and allow the individual to charge "relatively" safely.

I know some of you might have a problem with the default settings of some BMSs. The overcharge and discharge protection might be too low/high but I'm pretty sure I can request adjustment of these rates. Should I consider purchasing a bunch? Price is right and free shipping to Canada it seems.

 

[dnmun]

but it is $56 for the 40A model. i have been selling the D166 from Bestechpower for $46

 

[wesnewell]

The problem I have with all these li-ion bms's is the LV protection and the recovery voltages. You don't want them that low for rc lipo. LV should be no lower than 3.3V and recovery no lower than 3.4V IMO. Otherwise they let you run your rc lipo below 0% soc which is about 3.3V. Of course if you monitor pack voltage you can always avoid that, but that also eliminates the need for the bms anyway, except as a means for an easy charge port. I'm not opposed to bms's for rc lipo for easy charging, but don't expect one that has a 3.0V LV protection to actually protect your cells from over discharge, when they are at 0% soc long before that.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

 

[tenutso]

but it is $56 for the 40A model. i have been selling the D166 from Bestechpower for $46

I didn't realize you were selling these. Do you have the D166 in 14s? The specs are better on this unit.

 

[tenutso]

The problem I have with all these li-ion bms's is the LV protection and the recovery voltages. You don't want them that low for rc lipo. LV should be no lower than 3.3V and recovery no lower than 3.4V IMO. Otherwise they let you run your rc lipo below 0% soc which is about 3.3V. Of course if you monitor pack voltage you can always avoid that, but that also eliminates the need for the bms anyway, except as a means for an easy charge port. I'm not opposed to bms's for rc lipo for easy charging, but don't expect one that has a 3.0V LV protection to actually protect your cells from over discharge, when they are at 0% soc long before that.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=47294

Thanks for the info. Now I've been binge reading for two days straight.

 

[dnmun]

he doesn't know what he is talking about. lipo is not fully discharged at 3.3V which he is using now. it used to be 3.5V he demanded people accept as fully discharged. and now he lowered it to 3.3V but neither is true. lipo is fully discharged at 2.7V.

 

[wesnewell]

he doesn't know what he is talking about. lipo is not fully discharged at 3.3V which he is using now. it used to be 3.5V he demanded people accept as fully discharged. and now he lowered it to 3.3V but neither is true. lipo is fully discharged at 2.7V.

That's pure BS. I've never stated rc lipo was fully discharged at 3.5V. I have stated it was at 0% soc at 3.3v and proved that unless you don't believe your own eyes. I've also shown that at 3.5V it's at 3-4% soc. I have suggested now and many prior times that an LVC of 3.5V per cell is prudent for long battery life, and it is. And you have no fricking idea what LVC I'm using. I've actually had mine set to 3.65V for the last 18 months. No, it's not fully discharged until it reaches 0V, but every time you take it below 0% soc at 3.3V you're just killing it faster. Take it down to 2.7V a lot and it won't be long before it's puffing like your ego. It's you that doesn't know what you're talking about, and this proves it.
http://endless-sphere.com/forums/viewtopic.php?f=14&t=47294
It's been pointed out to you at least once that not all lipo is the same, yet you keep lumping rc lipo in with other versions when it seems to suit you. You're not doing anyone any favors by doing this, and could be causing damage to life and/or property if someone takes your ignorant statements for fact and sends their rc lipo into thermal runaway.

 

[dogman dan]

Easy on the adjectives. Opinions vary.

Does a bms, even the best, make the risk of a contaminated RC lico cell less? There is still a significant hazard in selling folks batteries made from a cheaply made cell.

I think there is a big difference in how much damage a cell gets when discharged below 3.5v, depending on the c rate it is discharged at once it passes below 3.5v. But if I was running a 3.3v lvc on my current battery, an LVC trip would result in a cutoff at pretty close to 3.5v resting. They really start to sag once you pass 3.5v under load.

Ideally, try to at least slow down once you start to see 3.6v under load. 50v for 14s. Your customers need a voltage monitor as well as a bms. I consider 48v under a very light load time for me to stop, but I have been below that.

 

[tenutso]

Here's a datasheet from Bestechpower for my D167 14S order. I actually requested 2.8 LVC and 4.3 HVC but what they sent me for my final confirmation is a bit off. Very responsive and polite customer support I must say though. Can anyone with experience offer any advice on the adjustable settings before I get back to them to confirm my order.

These are cells I have for my build:

http://www.hobbyking.com/hobbyking/store/__18560__Turnigy_5000mAh_1S_20C_Lipoly_Single_Cell_.html?strSearch=1S%205000mah

 

[dnmun]

what did they send you? i use 2.8V/4.28V and it works fine. i have a 2.5V/4.25V D131 too. it works fine. they make the best stuff we can buy but if you give them the wrong information they have to make something special just for you which others don't use.

you do not have to order 14S. you can order 16S too and use just the first 14 channels and leave the other two empty until you go to 15S or 16S.

 

[tenutso]

what did they send you? i use 2.8V/4.28V and it works fine. i have a 2.5V/4.25V D131 too. it works fine. they make the best stuff we can buy but if you give them the wrong information they have to make something special just for you which others don't use.

you do not have to order 14S. you can order 16S too and use just the first 14 channels and leave the other two empty until you go to 15S or 16S.

They haven't actually sent me anything yet. Just a datasheet to confirm my order which I attached above. Just making sure the settings on my datasheet are acceptable. They've listed LVC as 3.0 instead of 2.8. I like your idea of getting 16S if messing with wire harness isn't an issue.

 

[dnmun]

the extra wires just have to loop around the sense wire bundle. it will only cost a buck more.

in fact you should find some other people close by in your country to split the airfreight cost. that is what i did for a bunch in two orders, or maybe three orders now from bestechpower.

i saw their D132 BMS and another one today on a web site where i had been watching a big water cooled motor:

don't know why anyone would want 4S but: http://www.ebay.com/itm/BMS-LiFe-4-Series-12V-/321298742737?pt=US_Rechargeable_Batteries&hash=item4acee5bdd1

or why you would only want 12S in a D131 when they make them 24S wide: http://www.ebay.com/itm/LiFe-BMS-battery-management-system-12series-36v-pack-/321250629075?pt=US_Battery_Converters&hash=item4acc0795d3

and here is the D132, but only 8S: http://www.ebay.com/itm/LiFe-BMS-battery-management-system-8series-24v-pack-/321250611668?pt=US_Battery_Converters&hash=item4acc0751d4

 

[wesnewell]

They haven't actually sent me anything yet. Just a datasheet to confirm my order which I attached above. Just making sure the settings on my datasheet are acceptable. They've listed LVC as 3.0 instead of 2.8. I like your idea of getting 16S if messing with wire harness isn't an issue.

You do realize that recommended max charge for these cells is 4.2V don't you. And max recommended discharge is no less than 3.5V. Even a 3.0V LVC will let you discharge the cells below 0% soc. Anyone with any sense will tell you the same thing.

 

[dogman dan]

His bms, he can do what he wants. Maybe he wants an overcharge for racing or other high performance use?

Does adjusting the HVC up affect when the bms starts discharging the high cells? Or is that set no matter what?

 

[dnmun]

4.2V is not overcharged. you cannot just make stuff up and demand people believe it because you bot a hobby king pack and now you are an expert.

there are 400 billion laptop cells charged to 4.2V every second of every day.

 

[Punx0r]

It is over-charged if your application requires a HVC of <4.1vpc

Looking at the spec for some of the newer 18650 LICO cells it seems they're rated for 4.35vpc. No doubt due to the purity and thus stability of the electrolyte.

A BMS with adjustable cell LVC and HVC would be very useful. Then you could match it to your application, whether you're using primo LICO with a safe operating range of 2.7-4.35V or shonky RC LICO at 3.5-4.1V.

I think we must accept that SOC is defined by the cell manufacturer and subject to various caveats.

 

[friendly1uk]

Very little in this thread makes sense. I would like to start again.

Are we talking lipo, as in 2.7-4.28v cells? because 48v is not 14s. It is 13s, and $20 programmable units exist for 13s.

 

[wesnewell]

4.2V is not overcharged. you cannot just make stuff up and demand people believe it because you bot a hobby king pack and now you are an expert.

there are 400 billion laptop cells charged to 4.2V every second of every day.

Do you you have a reading comprehension problem? Can you point to where I said 4.2V is over charged? No, because I never said that. I said it was the recommended max charge.

 

[wesnewell]

He is using the rc lipo cells he linked to above that have a recommended max charge voltage of 4.2V and are at 0% soc at ~3.3V, not 18650 cells which have different specs with a 0% soc at under 3V. Charging these cells to 4.28v under normal conditions on a daily basis and using an LVC of 2.8V is just stupid IMO.

 

[tenutso]

That all being said and well appreciated the fact of the matter is this BMS (D167) will not have the flexibility to meet these requirements either way. We're stuck with 3.0v/4.28v as the closest settings based on hardware limitation. I'm pretty aware that HK lipo cells are not the most ideal cells out there for a BMS application so the real question is will this BMS serve a useful purpose for building HK lipo packs. Ideally one would prefer not to continuously bounce of BMS limiters and allow them to do their job as a fail-safe. We're not talking production packs here. Maybe only time can tell.

 

[friendly1uk]

I think the back N forth between dnmun and wes must be a little confusing. Who do you believe hay..

Minimum voltage is 2.7v and we aim to balance them all to 4.2v each. During the balancing operation some cells may get past 4.2v (well, if they didn't non would ever need trimming back down) and it is this over-shoot that concerns the high voltage cut-off. 4.28v is the maximum before the charging setup realises it can't trim them back down quickly enough so must terminate charging.


So, back to my question. From the top. What are you doing. Non of this makes sense. 14s lipo is not 48v. This thread will never make it off the ground at this rate.

 

[wesnewell]

According to the spec sheet, they can set over charge voltage down to 4.2V. So unless the spec sheet is wrong, there's no reason you have to have it higher than that.
http://www.bestekpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCB-D167.html
The problem he runs into is that unless he can change his controllers LVC from 42V up to ~49V the bms will let him over discharge his rc lipo considerably if he doesn't monitor it manually. And the reason he wants 14s is for more power and/or range and the controller will support it.

 

[tenutso]

I think the back N forth between dnmun and wes must be a little confusing. Who do you believe hay..

Minimum voltage is 2.7v and we aim to balance them all to 4.2v each. During the balancing operation some cells may get past 4.2v (well, if they didn't non would ever need trimming back down) and it is this over-shoot that concerns the high voltage cut-off. 4.28v is the maximum before the charging setup realises it can't trim them back down quickly enough so must terminate charging.


So, back to my question. From the top. What are you doing. Non of this makes sense. 14s lipo is not 48v. This thread will never make it off the ground at this rate.

I'm Not sure why series is in question. Wouldn't the same principles apply to 13s-16s and so on. I'm still a student when it comes to all this. I have several 58.4 lifepo4 universal chargers which I'd like to reuse and would naturally like to reach the highest voltage possible without blowing a 63v cap on my controllers. 14s should sing in a 48v set up as far as I'm concerned.

 

[dnmun]

you can use the 15S lipo on the 48V controller.

there is no ambiguity. wes does not know what he is talking about. he does not know how a BMS works and has a need to destroy any conversation in which i am involved trying to help someone. his stalking me has gotten to the point i am more than annoyed.

his deliberate attempts to make people afraid to do anything but what he says is ok is offensive beyond words but there is nothing i can do to stop him from continuing this vendetta against anything that involves using a BMS.

his claims that a BMS will destroy the battery and cause fires as well and his demand that we accept 3.5V as fully discharged because he says it is so is deliberate misinformation and i will not allow this place to sink any deeper into more and more misinformation about batteries and BMSs.

 

[friendly1uk]

I think dnmum said these won't balance till 4.2v so if you drop hvc to 4.2 there is a knock on effect. One that is easy enough to understand. However I found the language barrier between me and henry at bestek a real problem. So much so, that I don't actually know for sure what he sent me. I did try for custom figures but he just seemed to argue with me. So I gave up.

If the op really wants a 48v lipo pack as he said, It is 13s and I can work with that. If I ever pass 13s I will buy two 13s boards and sum them up. If anyone in the uk wants a bestek 12s lipo bms let me know. I doubt I'm going to use it. I don't like his stuff.
14s will indeed make a 48v setup over perform. Except for battery meters, which will claim more is left than there is. Which I believe can be cured if the controller has the separate power wire for switching it on, as this wire is the one the battery meter watch's so a voltage divider could sort it out. Maybe... .. I'm just making this up as I type.


Edit to answer the post above:
I thought you were building a 48v pack. Which would allow the use of the $20 programmable bms. I don't personally feel another cell is worth it. You end up buying from bestek which I have done and don't fancy doing again. It was lots more money for a product that just didn't excite me. In fact, I wanted to get the soldering iron out. I imagine a scooter might pull more than the 30 amps the $20 board can cover, but swapping fets is not so hard. I know people in europe who can customise the $20 microprocessor based boards for you, to do lots of things. This is why the change over from 13s to 14s is such a sticking point for me. I have to leave the cheap flexible boards and move to something I don't actually like. They can hit 4.305v per cell you know. That is within spec of the board, but not the cells. I can't work with that. Who could I blame after the disaster if I pair up incompatible stuff.


edit again. Now dnmum is above me. Must type faster...

Almost 100% agree with you dnmum, except it is not just you. He seems to jump on anybody promoting the only method of battery management that anyone outside of rc modelling uses. All electric vehicles use a bms for good reason, but I have seen people here avoid the topic recently because they know what will happen if they utter the abbreviation. That is unacceptable.