A123 26650 12v module compared to calb cells

[Ktraughb]

(Edit): As for cheap HK lipo, I suppose that's an option. I'm not a fan of lipo for safety reasons, but those could also be easily overcome in this application with a fireproof box. It may not have the same versatility and will not have the same level of safety as the A123 pack though. Maybe that does not matter to the OP, but it would to me.[/quote]
On this topic. Yes, safety matters. I do like having a car. Lol. Lipo is not preferred.

 

[Ktraughb]

If I do decide to use 4 calb cells in series... Is there any issue charging them as a 12v module with a 12v lifepo4 charger? Should I use a 3.6v and do each cell alone?

 

[arkmundi]

Its easier to bulk charge your pack with one charger at sufficient amps to do the job. My smart charger is 6 amps. I may get a Meanwell LCD power supply, upwards to 13 amps, for faster bulk charge, cutting my charge time in half. Mostly because those PSU's are fully weatherproof, for on-the-road. I attach two celllogs to my 16S packs, 2x8S, as I have them racked pannier style, so made the packs up in two bricks. The celllogs are programmed to alarm at 3.62 volts, the highest I'm comfortable with. So I manually pull the plug when the alarm beeps. Because I'm running without a BMS and ascribe to the BMS-free philosophy and so am visually monitoring pack health. For whatever reason, there is one pesky cell in my pack that charges faster then the remainder, or is high-V during the charge cycle. It'll trip the celllog first, so is the trigger to disconnect. The pack then settles itself, self-balancing, so that all the cells are are within 0.01V of one-another. There are other battery designs and charging approaches. Mine works fine for me, and would for most.

 

[Ktraughb]

Its easier to bulk charge your pack with one charger at sufficient amps to do the job. My smart charger is 6 amps. I may get a Meanwell LCD power supply, upwards to 13 amps, for faster bulk charge, cutting my charge time in half. Mostly because those PSU's are fully weatherproof, for on-the-road. I attach two celllogs to my 16S packs, 2x8S, as I have them racked pannier style, so made the packs up in two bricks. The celllogs are programmed to alarm at 3.62 volts, the highest I'm comfortable with. So I manually pull the plug when the alarm beeps. Because I'm running without a BMS and ascribe to the BMS-free philosophy and so am visually monitoring pack health. For whatever reason, there is one pesky cell in my pack that charges faster then the remainder, or is high-V during the charge cycle. It'll trip the celllog first, so is the trigger to disconnect. The pack then settles itself, self-balancing, so that all the cells are are within 0.01V of one-another. There are other battery designs and charging approaches. Mine works fine for me, and would for most.

Thank you, sir. Its actually refreshing to hear someone else doesn't like a bms. Good to know. Again, I think for ease of maintenance, I may go with calb cells over the a123. I know for a fact they'll survive the amp burst I'm looking for. And it won't be so difficult to charge between runs. Price is roughly the same.

 

[rtz]

I'd say it's a matter of packaging and convenience. Can you get more A123 cells if you ever need more?

Otherwise; get a couple CAMS and bolt them up and go!

Prices: http://store.evtv.me/products.php?cat=10

Or if in California; drive down to the warehouse and pick some up direct:

http://www.diyelectriccar.com/forums/showthread.php?t=69584

http://en.calb.cn/product/show/?id-630

Is there currently a better/cheaper large format cell out?


Everyone read this so no BMS required:

http://media3.ev-tv.me/cellcare.pdf

Summary:

Discharge each cell down to a specific voltage. Now your pack is balanced and ready. Assemble your pack. Charge it to a specific pack voltage. Now it is ready. Things to remember: Never, ever, ever discharge it below a certain amount. Never, ever, ever charge it beyond a certain amount. No point draining a pack. No point fully 100% charging the pack. To dangerous and just not worth that last little bit. Look at the curves in the charts in that pdf file. Play it safe and keep it all in the flat range. Good luck.

 

[Ktraughb]

I'd say it's a matter of packaging and convenience. Can you get more A123 cells if you ever need more?

Otherwise; get a couple CAMS and bolt them up and go!

Prices: http://store.evtv.me/products.php?cat=10

Or if in California; drive down to the warehouse and pick some up direct:

http://www.diyelectriccar.com/forums/showthread.php?t=69584

http://en.calb.cn/product/show/?id-630

Is there currently a better/cheaper large format cell out?


Everyone read this so no BMS required:

http://media3.ev-tv.me/cellcare.pdf

Summary:

Discharge each cell down to a specific voltage. Now your pack is balanced and ready. Assemble your pack. Charge it to a specific pack voltage. Now it is ready. Things to remember: Never, ever, ever discharge it below a certain amount. Never, ever, ever charge it beyond a certain amount. No point draining a pack. No point fully 100% charging the pack. To dangerous and just not worth that last little bit. Look at the curves in the charts in that pdf file. Play it safe and keep it all in the flat range. Good luck.

Wow evtv has a fantastic write up on exactly the things I've been researching. Thanks so much for that link. Very informative. And I never thought about replacement. You're right, original a123 are hard to come by. That seller owns them all now. Lol. It appears calb continues to release their cells and better replacement models as well. Any particular charger you might recommend that won't break the bank, but is lifepo4 friendly?

 

[arkmundi]

Yea, I'm of the mind to keep 80%<SOC<20%, meaning never fully charged, never fully discharged. Long trip, I'll do 90%<SOC<10%. So at most I'm running on 16ah, sufficient for most all my trips. Very long and I'll put on an extra 20ah pack. FYI, A123 cells are available through http://buya123batteries.com, now StorTronics managed, the retail distributor for A123. They are not difficult to acquire, just expensive. But yea, I'm all for better pricing and am myself considering EIG and Calb cells, for my next pack. 80ah cells? That's a hefty amount of ePower.

 

[Punx0r]

That process is called bottom-balancing. It's rarely (ever?) used in commercial systems and considered daft by most people on this forum, so I would think carefully before following that advice. Also, well matched cells and conservative charge/discharge limits will reduce the frequency with which you need to balance the pack, but will not eliminate the need. You need either a BMS or balance charger.

 

[dnmun]

it really is too bad that the people who continue to promote this ignorant idea of 'bottom balancing' that the idiot on evtv has promoted cannot be held responsible for damaging batteries when people actually follow their advice and refuse to use a BMS as is needed for any lifepo4 chemistry.

just another ignorant anonymous nobody giving advice to newbies who have no clue how misleading is the advice they get for free. only here. other forums have technical people who will correct misinformation.

 

[arkmundi]

You need either a BMS or balance charger.

Or the human BMS doing visual monitoring. Why I called it philosophy, because there are different perspectives. If I were running on nitro-Lipo, which I'd never do, then yea, I'd have both a BMS and a balance charger. But I'm running on a very robust cell and have never seen a need for either. I know because I look at the V on each cell in my pack twice a day - on return at low-V and after charge at high-V. Neither a BMS or balance charger will ever be as smart as I am and I'm of a mind to not delegate my intelligence, especially when it costs. FYI, I have a balance charger. I just never use it. And its over-charging that is the main culprit if damaging cells. But I also have a very capable smart charger that turns itself off at near 100%.

 

[dnmun]

you also have destroyed a battery by over discharging it by accident when you left the controller on, which you do not ever mention.

 

[arkmundi]

you also have destroyed a battery by over discharging it by accident when you left the controller on, which you do not ever mention.

rubbish. we'll never agree, but your approach is to trash people's perspective. Its very difficult to over-discharge A123 cells. So I'll up your trash move ... you don't have a clue what has happened in my eWorld, just speculation...

I have built exactly four battery packs. 3 A123 AMP20 and 1 A123 26650. My first A123 pack was stolen off my back porch while I had it charging. Lost the charger too. My two AMP20's for the MAC/Trek are working wonderfully. My 26650 pack remains serviceable. Have replaced exactly 4 cells in the 96 cell pack, because I bought a full carton of 100. So what the frellnfrackisthatjackhack???

 

[Ktraughb]

Hmm. A heated debate with two very opposing opinions. Seems to be a decent amount to of data to support both. I may risk it, and while I'm new to lifepo4, I'm definitely not new to electronics/electrical projects. I realize I may risk the cells, but I intend to charge these as described above without a bms. I think with what I'm doing, burst power only, it doesn't make at of sense to have a full bms built. I won't be drawing tons of amperage daily, or for extended periods at all.

 

[arkmundi]

I've been to the BMS-free and BMS-for-sure debate before and as you say, there is good argumentation on both sides. Its a choice those making battery packs needs to make. In favor of taking the BMS-free approach first is the possibility of adding in one latter, should the need be perceived, and postponing the additional cost. I say should the need be perceived because I believe in direct observation, collecting your own data over time and making an independent informed choice. I may add in a BMS at some point in time, if its obvious to me I need it. At this time, however, its not apparent. I'm staying below high-voltage and above low-voltage specifications for the cells. And as said, the A123 line of cells are very robust and appear to self-balance just fine. Its differences in internal resistance that lead to out-of-balance conditions during either charge or discharge. I don't see that in my pack.

 

[Ktraughb]

I've been to the BMS-free and BMS-for-sure debate before and as you say, there is good argumentation on both sides. Its a choice those making battery packs needs to make. In favor of taking the BMS-free approach first is the possibility of adding in one latter, should the need be perceived, and postponing the additional cost. I say should the need be perceived because I believe in direct observation, collecting your own data over time and making an independent informed choice. I may add in a BMS at some point in time, if its obvious to me I need it. At this time, however, its not apparent. I'm staying below high-voltage and above low-voltage specifications for the cells. And as said, the A123 line of cells are very robust and appear to self-balance just fine. Its differences in internal resistance that lead to out-of-balance conditions during either charge or discharge. I don't see that in my pack.

Do you think the modules I posted in question by hymotion would be susceptible to imbalance issues? I know a 4s module with the calb cells would be simple to check voltage on often. Not so simple without pulling the a123 module apart and adding individual lines. Thoughts?

 

[wb9k]

Do you think the modules I posted in question by hymotion would be susceptible to imbalance issues? I know a 4s module with the calb cells would be simple to check voltage on often. Not so simple without pulling the a123 module apart and adding individual lines. Thoughts?

If you look at the paper I put together on these modules, you'll see that at the front of the assembly there are four screws. Those are your sense points. To monitor voltage, all you have to do is connect a cell log or some such to those screws. No need to add wires or do any surgery of any kind. I have a harness with alligator clips that I use when I balance my modules by this method. Now, if you want to drive more than a couple Amps of current at a time into individual cell groups using the balance sense lines, THEN you'll need to do surgery and beef up the inner sense lead connections to handle the heavier current. The output power leads at the + and - ends of the pack are more than adequate for your needs and bulk charging at any current you can muster from a 120 Volt outlet--and the cells will take it too. It seems to me this would be easier than buying individual cells that aren't fused or even assembled into a pack. I don't understand where this idea comes from that four big cells is easier to work with than a bunch of smaller cells already assembled into a quality pack that even has fully accessible sense leads. Think about this---if one cell fails in the 11P pack what are the consequences? Compare this to a single cell failure in any 1P pack.

 

[Ktraughb]

Do you think the modules I posted in question by hymotion would be susceptible to imbalance issues? I know a 4s module with the calb cells would be simple to check voltage on often. Not so simple without pulling the a123 module apart and adding individual lines. Thoughts?

If you look at the paper I put together on these modules, you'll see that at the front of the assembly there are four screws. Those are your sense points. To monitor voltage, all you have to do is connect a cell log or some such to those screws. No need to add wires or do any surgery of any kind. I have a harness with alligator clips that I use when I balance my modules by this method. Now, if you want to drive more than a couple Amps of current at a time into individual cell groups using the balance sense lines, THEN you'll need to do surgery and beef up the inner sense lead connections to handle the heavier current. The output power leads at the + and - ends of the pack are more than adequate for your needs and bulk charging at any current you can muster from a 120 Volt outlet--and the cells will take it too. It seems to me this would be easier than buying individual cells that aren't fused or even assembled into a pack. I don't understand where this idea comes from that four big cells is easier to work with than a bunch of smaller cells already assembled into a quality pack that even has fully accessible sense leads. Think about this---if one cell fails in the 11P pack what are the consequences? Compare this to a single cell failure in any 1P pack.

True, but if one cell fails it will have to be de-soldered, replaced and balanced and re-soldered into the pack. Would a fresh cell affect the overall stability of an individual pack?

 

[wb9k]

Think about this---if one cell fails in the 11P pack what are the consequences? Compare this to a single cell failure in any 1P pack.

True, but if one cell fails it will have to be de-soldered, replaced and balanced and re-soldered into the pack. Would a fresh cell affect the overall stability of an individual pack?

Your options depend on a number of things. Most times, cell "failure" (which is relatively rare to begin with) is not a catastrophic problem, but the development of an undesirable behavior (like excessive self-discharge). In those cases, whether or not this even becomes noticeable depends on mostly the frequency with which a battery is used. If used often and charged with a BMS, you may never even notice anything at all. It's more a case of a "dud" in the bunch, but because it's (in this case) less than 10% of the total cell group, the other 90% of cells that are still OK can pick up the slack unless the problem is severe, which it rarely is. These Hymotion modules we are talking about have been in storage for a couple years by the time they are pulled out and tested. If problems like HSD exist in the module, the cell group will already be dead and the module scrapped. The chances of you having this problem with these batteries are consequently very low.

Let's say that somehow a really severe problem develops with a cell and you are able to figure out who the culprit is (not always easy without a good quality meter, mind you). Cell replacement in these modules is not really possible because of their design. You can, however, easily use a dremel tool to carefully cut one of the weld straps to isolate a problem cell. Then you'll have the same pack, but with a little less capacity and a little less power capability. For your application, the battery would continue to perform acceptably. Re-(top)balance the pack and continue on your way. You could replace the cell, but you would have to resort to some pretty ghetto techniques, which doesn't seem to be your style (and good on you for that.)

Keep in mind that I work in warranty, so I see pretty much everything that breaks. My head is always looking at what can go wrong, and planning for those events. My experience with the Hymotion packs and modules (and I have a lot of it) says that these modules are in all likelihood going to give you years of trouble-free performance, and they are as easy to care for as it gets. I don't use a BMS on any of my Hymotion packs, opting instead for the kind of techniques that Arkmundi describes in this thread. This is not for everyone (and certainly not for lipo), but if you control your processes intelligently and are vigilant in overall pack supervision (mostly during charging), all should be just fine. The Hymotion module in my audio system probably sees near to 100 cycles per year. I balance it once or twice a year. It doesn't need any more than that. All charging happens right on the audio rack. The 26650 packs I use in my lawnmower and other devices run about the same, with the same type of pack management techniques.

Hope that helps.

 

[Ktraughb]

Think about this---if one cell fails in the 11P pack what are the consequences? Compare this to a single cell failure in any 1P pack.

True, but if one cell fails it will have to be de-soldered, replaced and balanced and re-soldered into the pack. Would a fresh cell affect the overall stability of an individual pack?

Your options depend on a number of things. Most times, cell "failure" (which is relatively rare to begin with) is not a catastrophic problem, but the development of an undesirable behavior (like excessive self-discharge). In those cases, whether or not this even becomes noticeable depends on mostly the frequency with which a battery is used. If used often and charged with a BMS, you may never even notice anything at all. It's more a case of a "dud" in the bunch, but because it's (in this case) less than 10% of the total cell group, the other 90% of cells that are still OK can pick up the slack unless the problem is severe, which it rarely is. These Hymotion modules we are talking about have been in storage for a couple years by the time they are pulled out and tested. If problems like HSD exist in the module, the cell group will already be dead and the module scrapped. The chances of you having this problem with these batteries are consequently very low.

Let's say that somehow a really severe problem develops with a cell and you are able to figure out who the culprit is (not always easy without a good quality meter, mind you). Cell replacement in these modules is not really possible because of their design. You can, however, easily use a dremel tool to carefully cut one of the weld straps to isolate a problem cell. Then you'll have the same pack, but with a little less capacity and a little less power capability. For your application, the battery would continue to perform acceptably. Re-(top)balance the pack and continue on your way. You could replace the cell, but you would have to resort to some pretty ghetto techniques, which doesn't seem to be your style (and good on you for that.)

Keep in mind that I work in warranty, so I see pretty much everything that breaks. My head is always looking at what can go wrong, and planning for those events. My experience with the Hymotion packs and modules (and I have a lot of it) says that these modules are in all likelihood going to give you years of trouble-free performance, and they are as easy to care for as it gets. I don't use a BMS on any of my Hymotion packs, opting instead for the kind of techniques that Arkmundi describes in this thread. This is not for everyone (and certainly not for lipo), but if you control your processes intelligently and are vigilant in overall pack supervision (mostly during charging), all should be just fine. The Hymotion module in my audio system probably sees near to 100 cycles per year. I balance it once or twice a year. It doesn't need any more than that. All charging happens right on the audio rack. The 26650 packs I use in my lawnmower and other devices run about the same, with the same type of pack management techniques.

Hope that helps.

So I spoke with the seller today. He is a middleman that actually bought them directly from the pdf posting you gave me. Interestingly, when I mentioned someone told me they were bulk charging these with success he finished my sentence with "until he burns his house down." He exclaimed again I should not bulk charge these and they should only be operated with a bms. Is he just trying to sell me something? I told him you had great success in your prius and he almost acted like he couldn't believe it. You've given me the best supporting info to this point, so I'm inclined to trust your research and results. It seems some people really fear batteries in general. Then again, I'm the same guy who built a 8000+ Farad super capacitor module with zero balancing, charged it at 250 amps... And saw zero issues. Still to this day.

 

[wb9k]

If you use a balancing charger, that is your BMS during charge. If you closely watch your cell balance with every charge and discharge cycle and bulk charge to about 1/2 Volt below 100% SOC for the pack, you can go months or even years in cases like yours without the need for any balancing of any kind. But, you have to KNOW the pack, know the numbers you have to obey, and know how to be extra careful when it's needed. Lots of people out there (and in here) aren't qualified to run this routine and should never be allowed near any li battery without a full time BMS attached to it. You sound to me like you can pull this off no problem, but you have to understand the risks and do what you are comfortable with.

Personally, I've made mistakes overcharging cells in the past enabled by the use of an unregulated solar panel on lithium packs. The small current available didn't seem like a risk....but it was. Today, I ALWAYS have some level of built-in hardware overprotection in addition to my own internal assurances of where my pack SOC is. The key is to NEVER make it possible to overcharge a cell to a dangerous level. If a pack has been in storage for a while, you can do this by dialing back the voltage on your power supply. For example, an LFP "12 V" battery is at 100% SOC at 14.4 Volts. If you are taking a pack out of storage that was balanced when you put it away, verify present balance and correct any issues visible there. Then charge the pack to 13, or 13.5 Volts (limit the supply to this value) and check balance again after current falls to near zero. If still OK, take it up another 1/2 Volt until you reach 14.2 or so. Make sure nobody exceeds 3.6 Volts, hopefully all are around 3.55. Use and repeat.You'll notice you need a current-limiting, adjustable output power supply which is, IMO, mandatory for anyone who wants to manage li batteries without a "traditional" BMS. If you're not willing to make that investment, then get a BMS or a balancing charger to use with your existing supplies. A good balancing charger like the Cell Pro 8 is also pretty much a requirement in my opinion. The supply I'm using (a nice Kikusui supply capable of 0-35 Volts at 0-20 Amps I got on eBay) along with my cell pro and accessories cost me about $500, so maybe a $200 BMS you can plug into any old "12 Volt" supply--which you probably already have--isn't such a bad deal. I don't let this setup run totally unsupervised (while I'm away from home or in bed.) I do charge unsupervised with my systems that have good commercial BMS's or automatic shutdown on charging with multiple other protections as well.

If you're reading all this and are thinking, "this is serious, but I get it and can make this work", then you're probably OK. If you're scratching you head trying to figure what I just said, buy a BMS or a balancing charger.

 

[wb9k]

Re-reading your post, it sounds like maybe you think I don't have any BMS in my Hymotion Priuses. That is NOT the case. The Hymotion pack has a very good BMS integrated into it. What you are looking at is 1/2 a single module from a Hymotion pack, which includes 7 88-cell modules, a BMS, DC/DC converter-charger, contactors, and a bunch of wiring, and sensors for safety and thermal concerns. I absolutely have BMS's in all my cars and motorcycles that plug in. I didn't have one on my scooter battery, and don't use them on my lawnmower, or audio sytem packs. For those, I use bulk charging or balancing-charging instead. Just wanted to be sure that's clear.

 

[Ktraughb]

Re-reading your post, it sounds like maybe you think I don't have any BMS in my Hymotion Priuses. That is NOT the case. The Hymotion pack has a very good BMS integrated into it. What you are looking at is 1/2 a single module from a Hymotion pack, which includes 7 88-cell modules, a BMS, DC/DC converter-charger, contactors, and a bunch of wiring, and sensors for safety and thermal concerns. I absolutely have BMS's in all my cars and motorcycles that plug in. I didn't have one on my scooter battery, and don't use them on my lawnmower, or audio sytem packs. For those, I use bulk charging or balancing-charging instead. Just wanted to be sure that's clear.

No, I understood what you meant. I just didn't convey it well in my last post.