Tuesday, February 6, 2018

[Electric Boats] Re: #18650 Batteries

 

If it were only true! Your arithmetic is good but the raw data unfortunately is a bit overoptimistic. I would LOVE to duplicate my 8 big honking golf cart batteries with only 500 or so cheap lithium cells but it won't happen. Most of those cheap cells with wild capacity claims are actually only about 1200 to 1800mah and some are even less. I have heard of them testing out at 900mah.

Possibly the most costly element is not the cells themselves, but the BMS required to keep so many cells playing nicely with each other at a high degree of safety and reliability. Better cells will spec out more consistently, Careful testing and matching will help. Panasonic is probably the best brand and they will not be cheap. There is so much difference between good (Panasonic) and bad (brands you haven't heard of, from China) that there are probably counterfeit Panasonics being sold.

DIY building a 18650 bank or 26650, 32600, 32650 or whatever size cell bank is much more practical where thermal runaway is not such a big deal. An ebike pack, for instance. Otherwise you gain very little by not just buying a balanced pack from a manufacturer or salvaging from an electric car. Far simpler to go with large prismatic cells, big enough that there is no need to wire in parallel, I think. The BMS can be quite simple or possibly not even used, with space for air circulation and individual fuses between cells, I am thinking. But for now I am sticking with my golf cart batteries.

Keeping my eye on the Samsung 21700 though. Tesla will probably be making kajillions of them under license, soon.

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Re: [Electric Boats] #18650 Batteries

 

OK, so this raises several questions!     :)

1)  One of the sites listed chargers - and they said they were for ION batteries, NOT LiFePO4.  Is there that much difference in the charger?

2)  One of the kits had magnets in it.  What are THOSE for?  Is that to make sure the bars stay connected if you hit a bump?

3)  Looks like both of these allow you to connect a bunch of batteries in parallel.  Is it COMMON to connect a bunch of cells in parallel like that, and THEN connect the big chunks in series, and the BMS only monitors the blocks?

3.a)  What happens if one of the cells in the parallel block dies / shorts??  Will that not flame the whole block?

I do totally get that the BMS would cost more than the batteries if you monitored each and every 18650 in a larger bank.

John

On Tuesday, February 6, 2018, 1:02:27 PM CST, James Schwarz jschwarz@latticesys.com [electricboats] <electricboats@yahoogroups.com> wrote:


 

There are two companies that provide DIY kits for building lithium batteries from 18650 cells, namely:


Jim Schwarz

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Re: [Electric Boats] #18650 Batteries

 

There are two companies that provide DIY kits for building lithium batteries from 18650 cells, namely:


Jim Schwarz

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Posted by: James Schwarz <jschwarz@latticesys.com>
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Re: [Electric Boats] #18650 Batteries

 

Those are not rechargeable cells good for your mini Maglite flashlight though makes it really lightweight. 

On Tue, Feb 6, 2018 at 7:56 AM, oak oak_box@yahoo.com [electricboats] <electricboats@yahoogroups.com> wrote:
 

I saw AA Energizer Lithium batteries at the grocery store, and was thinking about the past a year (or two or three?) ago where someone said they were going to put together a bank from a whole bunch of small cells.

It seemed odd that they had plenty of lithium AA batteries, but no chargers.  Looking the internet, it kinda' seems like these aren't meant to be recharged - just used as a higher capacity disposable??  Is that really true?

Then, I came across #18650 batteries.  Just looking at the internet, they appeared to be very close to the AA battery form factor, but on closer inspection, longer and thicker - but also higher capacity?  And higher voltage - these were rated as 3.7V cells, not 1.5 like AA's.

Many of the 18650 batteries were about 3000mAh, but some by Garberiel, seemed reasonably priced (on Amazon), and claimed to be 6000mAh.   I haven't done the math yet, but it looked like it would be a cheap way to get a 48V bank quickly, and then as I wanted to put more $$ into it and as the experiments went forward, I could always add more capacity in parallel (which at that point would probably be more expensive than just buying higher capacity cells to begin with).

Anyway, I was curious if anyone has played with these cells?  Is the 6000mAh rating likely to be real?

Sounds like it would take about 221 of these to make a 48V, 100Ah battery - is that right?
13 x 3.7=48V   17x6Ah>100Ah, so 221 cells to make up the bank...   @ about $15/10, about $330 for the bank???   That sounds way too good to be true.  Of course, there would need to be monitors and battery boxes, etc...   But does this math sound at all close???


John





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Re: [Electric Boats] #18650 Batteries

 

Anyone who claimed to have a 6000mah 18650 cell is lying to you. Even Tesla isn't there in that form factor. The best 18650s commercially available are from Panasonic (Tesla's partner in lithium joy) and have a capacity of 3400mah. And they are not cheap. 


I would so very much like to be proved wrong in this. 

For fun, I purchased 30 similar 18650 cells, black shrink wrap, no branding, marked 6000mah capacity. There was a mush-mash or capacities, mostly around 1200mah. I was able to build a few small packs for my son's Halloween costume and other toys, but I would never want to depend on them for my safety (like powering a dinghy or such). 

If your goal is a small diy pack, I would suggest buying surplus laptop packs and ripping them apart and repacking to your needs. Count on about 3000mah per cell. 
For a 48v nominal, go for a 15-series pack. There are BMS boards readily available for that size. 

Best of luck,

/Jason

--
Jason Taylor
v:514-815-8204

On Feb 6, 2018, at 08:40, Chris Morriss chris.morriss@ouroboros.myzen.co.uk [electricboats] <electricboats@yahoogroups.com> wrote:

 

I use 18650 cells (salvaged from an old laptop PC battery pack) for two high-power LED torches I have.  Chargers are available from Amazon to charge two of the cells in parallel.  Unfortunately they are difficult to charge in series (unlike lead-acid batteries) without sophisticated charge-equalisation circuitry.

Tesla use this size of cell in huge battery packs in their electric vehicles!

18650 cells are usually up to about 3.7 amp-hours, so I certainly wouldn't trust the 6 A-hr specs you've seen.


On 06/02/2018 12:56, oak oak_box@yahoo.com [electricboats] wrote:
I saw AA Energizer Lithium batteries at the grocery store, and was thinking about the past a year (or two or three?) ago where someone said they were going to put together a bank from a whole bunch of small cells.

It seemed odd that they had plenty of lithium AA batteries, but no chargers.  Looking the internet, it kinda' seems like these aren't meant to be recharged - just used as a higher capacity disposable??  Is that really true?

Then, I came across #18650 batteries.  Just looking at the internet, they appeared to be very close to the AA battery form factor, but on closer inspection, longer and thicker - but also higher capacity?  And higher voltage - these were rated as 3.7V cells, not 1.5 like AA's.

Many of the 18650 batteries were about 3000mAh, but some by Garberiel, seemed reasonably priced (on Amazon), and claimed to be 6000mAh.   I haven't done the math yet, but it looked like it would be a cheap way to get a 48V bank quickly, and then as I wanted to put more $$ into it and as the experiments went forward, I could always add more capacity in parallel (which at that point would probably be more expensive than just buying higher capacity cells to begin with).

Anyway, I was curious if anyone has played with these cells?  Is the 6000mAh rating likely to be real?

Sounds like it would take about 221 of these to make a 48V, 100Ah battery - is that right?
13 x 3.7=48V   17x6Ah>100Ah, so 221 cells to make up the bank...   @ about $15/10, about $330 for the bank???   That sounds way too good to be true.  Of course, there would need to be monitors and battery boxes, etc...   But does this math sound at all close???


John





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Posted by: "Jason (Electric Boats) Taylor" <jt.yahoo@jtaylor.ca>
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Re: [Electric Boats] #18650 Batteries

 

I use 18650 cells (salvaged from an old laptop PC battery pack) for two high-power LED torches I have.  Chargers are available from Amazon to charge two of the cells in parallel.  Unfortunately they are difficult to charge in series (unlike lead-acid batteries) without sophisticated charge-equalisation circuitry.

Tesla use this size of cell in huge battery packs in their electric vehicles!

18650 cells are usually up to about 3.7 amp-hours, so I certainly wouldn't trust the 6 A-hr specs you've seen.


On 06/02/2018 12:56, oak oak_box@yahoo.com [electricboats] wrote:
I saw AA Energizer Lithium batteries at the grocery store, and was thinking about the past a year (or two or three?) ago where someone said they were going to put together a bank from a whole bunch of small cells.

It seemed odd that they had plenty of lithium AA batteries, but no chargers.  Looking the internet, it kinda' seems like these aren't meant to be recharged - just used as a higher capacity disposable??  Is that really true?

Then, I came across #18650 batteries.  Just looking at the internet, they appeared to be very close to the AA battery form factor, but on closer inspection, longer and thicker - but also higher capacity?  And higher voltage - these were rated as 3.7V cells, not 1.5 like AA's.

Many of the 18650 batteries were about 3000mAh, but some by Garberiel, seemed reasonably priced (on Amazon), and claimed to be 6000mAh.   I haven't done the math yet, but it looked like it would be a cheap way to get a 48V bank quickly, and then as I wanted to put more $$ into it and as the experiments went forward, I could always add more capacity in parallel (which at that point would probably be more expensive than just buying higher capacity cells to begin with).

Anyway, I was curious if anyone has played with these cells?  Is the 6000mAh rating likely to be real?

Sounds like it would take about 221 of these to make a 48V, 100Ah battery - is that right?
13 x 3.7=48V   17x6Ah>100Ah, so 221 cells to make up the bank...   @ about $15/10, about $330 for the bank???   That sounds way too good to be true.  Of course, there would need to be monitors and battery boxes, etc...   But does this math sound at all close???


John





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Posted by: Chris Morriss <chris.morriss@ouroboros.myzen.co.uk>
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[Electric Boats] #18650 Batteries

 

I saw AA Energizer Lithium batteries at the grocery store, and was thinking about the past a year (or two or three?) ago where someone said they were going to put together a bank from a whole bunch of small cells.

It seemed odd that they had plenty of lithium AA batteries, but no chargers.  Looking the internet, it kinda' seems like these aren't meant to be recharged - just used as a higher capacity disposable??  Is that really true?

Then, I came across #18650 batteries.  Just looking at the internet, they appeared to be very close to the AA battery form factor, but on closer inspection, longer and thicker - but also higher capacity?  And higher voltage - these were rated as 3.7V cells, not 1.5 like AA's.

Many of the 18650 batteries were about 3000mAh, but some by Garberiel, seemed reasonably priced (on Amazon), and claimed to be 6000mAh.   I haven't done the math yet, but it looked like it would be a cheap way to get a 48V bank quickly, and then as I wanted to put more $$ into it and as the experiments went forward, I could always add more capacity in parallel (which at that point would probably be more expensive than just buying higher capacity cells to begin with).

Anyway, I was curious if anyone has played with these cells?  Is the 6000mAh rating likely to be real?

Sounds like it would take about 221 of these to make a 48V, 100Ah battery - is that right?
13 x 3.7=48V   17x6Ah>100Ah, so 221 cells to make up the bank...   @ about $15/10, about $330 for the bank???   That sounds way too good to be true.  Of course, there would need to be monitors and battery boxes, etc...   But does this math sound at all close???


John




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Posted by: oak <oak_box@yahoo.com>
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