Best BMS or a list of best BMS?

Batteries, Chargers, and Battery Management Systems.
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bowlofsalad   1 MW

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Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 03 2013 1:34pm

Hello,

The way I see it, there are three ways to go about this.
1. Rely purely on the BMS to keep each cell within it's appropriate low (uncharged) and high (charged) voltage.

2. Use the BMS for the most part while occasionally or frequently double checking it's work, potentially manually charging a lagging cell or two.

3. Be the BMS and charge the batteries yourself.

Personally, I am leaning towards using lifepo4 batteries. However, I am not sure which of the three ways in using a battery are to go with. I keep going around in circles in my head. A good BMS should never need it's work double checked, but sometimes it sounds like such a thing doesn't exist to many (battery murdering system). Is there a quick and easy way of checking the voltage of the cells? I've looked into celllog 8(C8). I wouldn't use C8 as a logger myself, but I have considered that perhaps there is an easy way to turn it on and off periodically to check the voltage of the cells and use C8s ability to alarm you of over charging (3.7v+).

If I could start a poll, I would, but it seems like a lacking feature here. I have noticed there is some controversy on this issue with some of the more long term members here on this forum, I apologize if this stirs drama.

Who makes the best BMS? Or am I the best BMS? I've been looking for some sort of BMS guide, but I haven't really found one. The number of batteries and BMS options are overwhelming, any guidance would be greatly appreciated.

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Re: Best BMS or a list of best BMS?

Post by cassschr1 » Feb 03 2013 2:41pm

check out liionbms.com

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 03 2013 3:33pm

cassschr1 wrote:check out liionbms.com
:shock: This just went from a maze to a maze of mirrors. :lol:

This is a mighty list, but I don't really know how to tell which could be qualified as 'good', if only there were a rating system on this site with ES members casting the votes.

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Re: Best BMS or a list of best BMS?

Post by 999zip999 » Feb 03 2013 7:24pm

With so much BS on the bms. First we need to know what is the batteries purpose ? Storage or for a car, bike,airplane ect.

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 03 2013 8:46pm

999zip999 wrote:With so much BS on the bms. First we need to know what is the batteries purpose ? Storage or for a car, bike,airplane ect.
Motorized bicycle.

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Re: Best BMS or a list of best BMS?

Post by 999zip999 » Feb 03 2013 11:50pm

The battery depends on the motor and controller you use and vise-versa. It must match and the bms to.

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 04 2013 12:03am

999zip999 wrote:The battery depends on the motor and controller you use and vise-versa. It must match and the bms to.
Alright, fair enough. Do you use BMS personally? Do you use a BMS with something like a celllog8? Or do you act as the BMS?

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Re: Best BMS or a list of best BMS?

Post by llile » Feb 04 2013 2:58pm

Most LiFEPO4 batteries come with built-in BMS. Ping, for instance, custom builds his BMS into every battery. Although there are folks who make them, most of us don't buy the BMS separately from a LiFEPO4. Perhaps you already understood this, in which case my apologies for stating the obvious.

There are several BMS suppliers that will sell you a separate one, including BMSbattery I can't personally say anything about them, although they have been recommended on this board.

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Re: Best BMS or a list of best BMS?

Post by dnmun » Feb 04 2013 4:04pm

EVERYONE who sells a lifepo4 battery as well as a limn battery will use a BMS. no manufacturer sells a lifepo4 pack without a BMS. none.

it is only here that people say you can build a pack and not use a BMS. but anyone who has to bulk charge lifepo4 knows that you need one to protect the battery from overdischarge and help to prevent overcharging and to balance the individual cells.

if you use a balancing charger then you can charge with that and use the LVC on the cycle analyst to try to protect the battery from overdischarge.

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Re: Best BMS or a list of best BMS?

Post by 999zip999 » Feb 04 2013 9:42pm

Bro my point is what are you using a 250watt euro motor or a 750watt 36v hub with a 20 amp controller ? My battery story would be to long if not told in full.
Yuor best bet would be a Ping with a BMS it has some great balancing led's that are great as you can see them balance. People have spent hours watching the lights of the Ping BMS and I miss that time. Plus it's plug and play. Yes just plug and play'. More ride time bigger smile.

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Re: Best BMS or a list of best BMS?

Post by 999zip999 » Feb 05 2013 12:17pm

What we need to see is the motor and controller and it will be easier to suggest a battery and bms.

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 05 2013 10:26pm

999zip999 wrote:What we need to see is the motor and controller and it will be easier to suggest a battery and bms.
I don't own anything concerning this matter, yet. Within the motor/controller area, I might go with something from ebike.ca. If not from there, I don't know of any other options other than ebay and what cell_man has. Sorry for the vague response, I don't really know. Maybe it'd be safer for me to just go with pingbattery.

Somehow, I feel like this question is boiling down to who makes the best battery, but that seems to be a matter of opinion and application.

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Re: Best BMS or a list of best BMS?

Post by llile » Feb 09 2013 10:31pm

Ah! So really, you are also picking out an Ebike, or ebike kit to build, or motors. batteries, and other parts to assemble into an Ebike. Am I correct?

So, the question is - how much technical skill do you want to use on this project? You can just buy an ebike off the shelf, there are many good ones, and ride away with a smile. Or, if you are like me, you must build it. Then you want a kit. Or if you must understand it at a deep level, learn enough to buy all the parts and assemble it with only your wits as a guide! (and some guidance from Endless Sphere of course!)

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 10 2013 1:02am

llile wrote:Ah! So really, you are also picking out an Ebike, or ebike kit to build, or motors. batteries, and other parts to assemble into an Ebike. Am I correct?

So, the question is - how much technical skill do you want to use on this project? You can just buy an ebike off the shelf, there are many good ones, and ride away with a smile. Or, if you are like me, you must build it. Then you want a kit. Or if you must understand it at a deep level, learn enough to buy all the parts and assemble it with only your wits as a guide! (and some guidance from Endless Sphere of course!)
Yes sir, I am aiming to assemble an e-bike. What I am pretty much seeking is a sort of buyers guide on value and pros and cons of various batteries and vendors. Sadly, all there seems to be is a general feeling for word of mouth.

I am most certainly like you in the sense that I am going to 'build' it. If I had a fair amount of instruction to follow, I'd gladly purchase a pile of a123 cells with a BMS and assemble. But the task of assembling a battery hasn't been too cut and dry for myself, perhaps I am missing the details. Surely, there must be a great benefit to assembling a battery to purchasing something pre-made. I grasp the more obvious benefits like potential lower cost (labor) and the benefit of you being the perfect troubleshooter if something goes wrong. But are a123 cells really much better than whatever ping may have to offer?

I have a short list of vendors to choose from, but there are only 2 or 3 that have any real or solid approval here. After reading around so many times, I've come across a few facts that relate to battery lifespan that I don't feel I hear enough. Try not to exceed a batteries C rating or amperage output, and do not discharge the battery beyond 70-72%. These two ideas seem to be the difference between 1000 cycles (this is what I've read two or three times, I don't know these things) and 5000 cycles.

So, to me, a logical course of action would be to take the ideal number of amp hours you'd like to have, multiply it by .43 and add that to it. To illustrate, my potentially ideal number of amp hours is 30. 30 times .43 is 12.9, 12.90+30=42.9, 42.9 times .7=30.03. Since I am not likely to find a 42.9 amp hour battery, I'd aim for around 40 amp hours in this circumstance. What I like most about this idea is, you could play to use a 40ah battery to around 28ah, but if you needed it, you'd still have some in reserve, 4ah in this case if 80% is your lower limit. I suppose all this is speculative and such, but it's fun to think about.

I guess what I seek is a great battery all around, with an excellent BMS. There are an overwhelming number of options, it's easy for me to phase out the less safe ones from the pool of possibility, but the rest are in the air, and the air is packed!

I believe this problem is something that many have encountered more than once. To me, a chart with a list of pros and cons on each battery, cost per watt hour per battery, and perhaps a rating for each battery sold and the vendor selling it. This probably sounds like a complicated tall order, but it seems essential in my mind. There are dozens of vendors for just about every product category in ebikes, sorting through it is difficult to impossible for the most part. It's really hard to know what is good and what is not. I made a http://endless-sphere.com/forums/viewto ... =5&t=47613 poll the other day on this matter, the votes paint an opposing picture, but I don't know how many newbs cast votes there. I've seen several newbie threads asking for help on selecting various parts, so I know this would be of help, I am probably doing a terrible job of describing what I mean. Amberwolf suggests speaking with Justin, I think Justin is associated with ebikes.ca, on this matter. The concept would basically envelope the review section of this forum. Sorry for the long winded post, thanks.

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Re: Best BMS or a list of best BMS?

Post by dnmun » Feb 10 2013 2:46am

instead of making it hard, just focus on how the pack will fit on the bike. the ping 48V15Ah is 11.25"x5.8"x4". make a cardboard box identical in size and see if it will fit in the frame. that's all you need to worry about. ping makes the best pouch pack, but they cost more. sun-thing28 guy is cheaper but does not have much of a reputation yet because only a few people have bot his battery.

you should expect the battery will be a lifetime investment if it is a lifepo4 pack. the current packs he makes will last 5 years easily. they are much better built than the older ping packs which did already last 5 years in some cases. he just got better at making the pouches and better at assembling the pack. plus he gives top notch support.

so make a cardboard box and see if it fits.

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Re: Best BMS or a list of best BMS?

Post by 999zip999 » Feb 10 2013 12:21pm

Bowlof salad just buy a premade lifepo4 pack with BMS.

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Re: Best BMS or a list of best BMS?

Post by cassschr1 » Feb 10 2013 4:02pm

So you want 40 amphr pack, thats huge,if your talking decent voltage.How many volts you want?
Lipo, ifyour super confident, own your home,or (not in apt. building)
konion, build it yourself,safe, or should say safer, no bms needed,THATS A BIG ONE, more capacity for the space than 26650 cells below,
a123 cylinder cells, safe, probably the real thing,bms preferred but not absolutely, monitor with cell-logs.
A123 pouch, safe, kind of hard to figure how to mount when dealing with large pack 24 to 30s. Don't know if the cells were 2nds etc.etc. etc. etc.Ya, there lots of doubts in my book if there gonna last 10 years. Read Circuits threads on this.He works with this stuff for a day job.
All these should be monitored with cell-logs if you want to be a happy camper!
I own all of the above, so I'm not biased, in large packs too.

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 10 2013 4:32pm

cassschr1 wrote:So you want 40 amphr pack, thats huge,if your talking decent voltage.How many volts you want?
Lipo, ifyour super confident, own your home,or (not in apt. building)
konion, build it yourself,safe, or should say safer, no bms needed,THATS A BIG ONE, more capacity for the space than 26650 cells below,
a123 cylinder cells, safe, probably the real thing,bms preferred but not absolutely, monitor with cell-logs.
A123 pouch, safe, kind of hard to figure how to mount when dealing with large pack 24 to 30s. Don't know if the cells were 2nds etc.etc. etc. etc.Ya, there lots of doubts in my book if there gonna last 10 years. Read Circuits threads on this.He works with this stuff for a day job.
All these should be monitored with cell-logs if you want to be a happy camper!
I own all of the above, so I'm not biased, in large packs too.
I am not willing to use lipo. It's going to be some kind of lifepo4 for myself. Someone on this forum sells a123 cells, http://endless-sphere.com/forums/viewto ... 31&t=36589 through this thread. Next to that, there is em3ev.com.

Basically, this question is to try to learn what the most reliable BMS is. The whole 1 2 3 thing seems to have been missed. What do you do? The first post in this thread speaks of options 1-3, which of the three do you primarily go with or think is best?

Personally, I think 2 might be the most wise way to go, I'd really like to know who makes the most reliable BMS though. I understand celllogs are good for manual monitoring, but I am interested in a BMS that is great for preventing overcharging and discharging. It's hard to really know who's BMS is most reliable. Even a simple contrast and comparison of reliability of the BMS system on pingbatteries to em3ev would be at least interesting.

Where do you purchase a BMS for a123 cells?

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Re: Best BMS or a list of best BMS?

Post by Kingfish » Feb 10 2013 4:34pm

dnmun wrote:instead of making it hard, just focus on how the pack will fit on the bike. the ping 48V15Ah is 11.25"x5.8"x4". make a cardboard box identical in size and see if it will fit in the frame. that's all you need to worry about. ping makes the best pouch pack, but they cost more. sun-thing28 guy is cheaper but does not have much of a reputation yet because only a few people have bot his battery.

you should expect the battery will be a lifetime investment if it is a lifepo4 pack. the current packs he makes will last 5 years easily. they are much better built than the older ping packs which did already last 5 years in some cases. he just got better at making the pouches and better at assembling the pack. plus he gives top notch support.

so make a cardboard box and see if it fits.
Exactly. I make models before building. First in CAD, then I print out a pattern and use that to mock up, then model that and refine as necessary. Works with battery bags and not too bad with fairings too :wink:

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 10 2013 4:55pm

Thanks for the suggestion.

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Re: Best BMS or a list of best BMS?

Post by SamTexas » Feb 10 2013 5:19pm

Building a battery pack from scratch is not a complicated task. It does involve a lot of time. I built 4 or 5 packs for my ebikes before I bought my first ready made battery. Obviously I like the packs I built much better mainly because none of them has the Battery Murdering Systems (BMS) included.

"Home made battery packs" is the tittle of the thread. It's mostly about 18650 laptop cells, but the principle applies to all cells. Read that thread and ask questions. People with ACTUAL experience will help you through the process, if you choose to go that way. BTW, don't even bother comparing Ping or other common LiFePO4 battery with A123. There is no comparison. A123 is head and shoulder above, assuming of course that the cells are bought from a reputable seller.

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What BMS style do you use?

Post by bowlofsalad » Feb 10 2013 7:01pm

There seems to be conflict on what is better, what do the will the polls tell us?

For your time, I offer you this silly little tune. https://www.youtube.com/watch?v=sJQYoGyEtDs :D

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 10 2013 7:06pm

Thanks for the response sam. I found the thread, http://endless-sphere.com/forums/viewto ... &start=495 I'll be sure to look it over, looks interesting at a glance.

What makes a123 so much better than lifepo4?

I am really a newbie, maybe you could spell it out for me.

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Re: Best BMS or a list of best BMS?

Post by SamTexas » Feb 10 2013 7:10pm

You're welcome.

A123 IS LiFePO4. Just a much better version of LiFePO4. A123 is a real company (though now bankrupted) with real technology, real production falicity, real quality control. But from the users' point of view, here are what matter: Much much higher rate of discharge and supposedly much longer life. And of course more expensive initially, but supposedly less expensive in the long term because of the longer life.

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Re: Best BMS or a list of best BMS?

Post by bowlofsalad » Feb 10 2013 7:39pm

SamTexas wrote:You're welcome.

A123 IS LiFePO4. Just a much better version of LiFePO4. A123 is a real company (though now bankrupted) with real technology, real production falicity, real quality control. But from the users' point of view, here are what matter: Much much higher rate of discharge and supposedly much longer life. And of course more expensive initially, but supposedly less expensive in the long term because of the longer life.
I've been doing enough reading to make my eyeballs bleed (kidding about the bleeding) and I've come across some information on life expectancy of lifepo4. The keys to lifepo4 lifespan seem to be depth of discharge and temperature, or at least not exceeding a certain rate of power consumption. I've developed a super simple formula for finding a person's ideal battery size. It's hard to say how far a person will go per mile on each amp hour, how much pedaling they do, wind, rate of acceleration, bicycle, weight and so on play a huge role in all of this. However, once you know your ideal battery size, multiply it by .43 and add that to the battery. So if 20ah is likely to get you to all the places you imagine going, multiply by .43 and add that number to the original number. So the math goes 20 times .43 is 8.6, 8.6 plus 20 is 28.6. Seeing as how there aren't too many 28.6 batteries, you'd round to 30ah. So you'd have a 30ah battery, this is part of the battery life extending magic occurs. I assume a tool like cycleanalyst would help with this, as I think it measures the consumed AH on the run. Multiply 30 by .7 and that will give you 70% of 30 or 21. Consume no more than 21ah and you'd be set, 21 would be your life extending level of discharge. You could go deeper, and slightly decrease the battery life if you really needed to and it wouldn't destroy the battery like discharging the battery to the dreaded 'lvc'. I think the reason for a123s greater lifespan (if that is true) is because if you abuse it, it'll survive, it won't get so hot when you discharge it so rapidly, and I think it might be able to handle deeper discharge better.

For a while, I thought a123 was a different chemistry, but I guess they just do something special with the ingredients in making their lifepo4 battery. In the end, they just come out with a better product.

I theorize, if treated well, you could achieve the same battery life with lifepo4 as you could with a123, but where is the fun in that? :twisted:

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