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Daox 07-22-2012 11:58 AM

Playing with A123 20Ah lithium cells
 
9 Attachment(s)
Yesterday, I picked up a few A123 20Ah lithium cells while I was at Drive Green Expo in Madison, WI. I have been wanting to tinker around with these batteries for a while now.

http://www.youtube.com/watch?v=87Xak65iT84

For those who don't know, these cells are very impressive. These are the batteries that are being used in the Fisker Karma. They can handle 10C (200A) continuous discharge and up to 22C (450A) burst discharge (depends on SOC). Most other prysmatic lithium cells can only handle 3-4C continuous discharge and around 10C burst discharge. The mottcell lithium cells I have in my Prius' plugin kit which you'll see below are 40Ah batteries and only capable of I believe 2C continuous discharge. Through my testing with them I don't even really know if I would say they can do that. Even at 1/2C continuous charge/discharge they get pretty warm.

These cells weigh in at just under 1.1lbs. My Mottcell cells are roughly 3.5lbs. However, I will need to add provisions for assembling and mounting the A123 cells so it will increase their weight, but I shall revisit that when I get there.

A123 amp20 data sheet


So, here are a few images I took so you can get an idea of the size.


Here is the packaging they come in. I got four cells (enough to make a 12V battery).
http://ecomodder.com/forum/attachmen...1&d=1342972254



I didn't have a soda can handy so I used a soup can for scale.
http://ecomodder.com/forum/attachmen...1&d=1342972254



They're very thin!
http://ecomodder.com/forum/attachmen...1&d=1342972311



Length.
http://ecomodder.com/forum/attachmen...1&d=1342972311



Width.
http://ecomodder.com/forum/attachmen...1&d=1342972311



Thickness.
http://ecomodder.com/forum/attachmen...1&d=1342972311



This is the 20Ah A123 cell compared to my 39Ah Mottcell prysmatic cell.
http://ecomodder.com/forum/attachmen...1&d=1342972311

http://ecomodder.com/forum/attachmen...1&d=1342972311

http://ecomodder.com/forum/attachmen...1&d=1342972311



I also measured the tabs. They are 1.775" wide x 1" tall. The positive terminal is aluminum and is .010" thick. The negative is plated copper and is .007" thick.

So, I have a 12V 20Ah A123 battery essentially. I'll be messing around with it a bit, developing a connecting method. Eventually I think I'll probably put it into the Paseo as the starting battery. It should weigh about 5lbs vs the current group 24 lead acid battery that is in there. While I won't be able to use it as an alternator delete battery (not enough capacity, but the wife hasn't been plugging it in anyways, and she has been driving it for the past year), it will lighten things up a bit. Funny too, the A123 cells really didn't cost a ton more than the lead acid deep cycle. If I wanted the same usable capacity I'd need 8 more lithium cells which would make it cost quite a bit more.

Ryland 07-22-2012 12:15 PM

I think this holds true for A123 system cells the same as it does for all other lithium cells, that you need to keep pressure on them so they layers don't fluff up and separate, bolting an aluminum plate to either side seems to be the popular way to do it.

I'm blown away by how cheap lithium batteries are now!

Cobb 07-22-2012 08:51 PM

Wow, looks a lot like those being sold for replacement packs for the first gen insight. I think a guy was selling 50 or 55 for a 1500 bucks.

Any reason you arent going to use these in place of your accessory batter in your prius? If your prius charging system works like the Honda IMA it should cycle off and on less frequently and hold a better charge than any lead acid battery. Most Hondas use the ELD to cycle the alternator or charging system off and on as needed vs a constant like on a typical altenrator use vehicle.

I use to charge my accessory battery before driving my Honda as a kind of mini test of the benefit of a phev and for the first few miles I had great fuel economy till that charge wore off.

How about replacing the pack in your prius with a few of those? :thumbup:

Daox 07-23-2012 08:13 AM

Yeah, that price sounds about right. I paid $27.50 per cell for these four cells.

While those are all nice and fancy options for using these cells, that won't be the case. The Prius' 'starting battery' is simply a small AGM to power up the electronics before the high voltage pack gets connected. To replace that small battery with these lithium cells would be a waste when I can replace a large group 24 battery in my Paseo and save quite a bit more weight. And, while replacing the 6.5Ah cells in the Prius' hybrid pack would be fun, it would be a huge pain too to convert to a new battery chemistry (thinking about the Prius' BMS). Couple that with the cells alone would cost almost $2k and I'm just not seeing that being worth it.

At some point in the future I would like to make an EV or DIY hybrid. I'm messing around with these cells because they are what I would like to use should I ever get around to it.

ecomodded 07-23-2012 05:37 PM

The battery packs would be good for portable use as well, for bicycling lights or camping or extending the laptops power.

Love the Li-ion battery technology, I just bought six 3.7 volt 18650 batteries for my flashlight that pump out 2 amps a battery, the flashlight uses 3 18650 to power 3 Ultra bright 12 watt Cree xm-l LED's.


Those A123 batteries remind me of the lipo battery packs, but bigger.

Daox 07-24-2012 11:52 AM

1 Attachment(s)
I've started designing how I want to connect the individual cells up. Keep in mind that I am planning ahead to use these on a hybrid or EV project so whatever I come up with must be scalable.

The cells are basically sandwiched together and wired in series. There are alternating aluminum and plastic spacers between the tabs. The whole string of cells is bolted together on each side with non-conductive (plastic) threaded rod. The aluminum spacers can be tapped for small screws, or drilled for a bananna type connector for BMS connections. In the case of my 12V, I won't need a BMS while using it as a starting battery. This setup keeps the weight down and utilizes all the surface are of the cell's tabs to keep resistance down and allow for high amperage draw.

I am still working on how I want to sandwich all the cells together, but I'll probably have some plates on each end to hold everything together. Some people tend to go overboard on this and I don't think its the most important thing unless you are really pushing the batteries.

I'll also have to add some sort of automotive type lug to the aluminum spacers on the end so I can connect it up to the car.

http://ecomodder.com/forum/attachmen...1&d=1343144465

user removed 07-24-2012 01:58 PM

At that price I might consider using them in my vehicle. I already have a 9 HP Honda Diesel engine acquired for the project. How much would they cost per KWH?

Since they would only be on-off to generate hydraulic pressure, could I avoid having to use a BMS?

regards
Mech

Daox 07-24-2012 02:11 PM

Well one cell is 64 Wh, so 16 cells to get 1kWh. $27.50 * 16 = $440 / kWh.

You only really need a BMS if you want to come anywhere near close to either end of the charged/discharged state. Using it as a starting battery I know this won't be the case. The alternator will only charge it to roughly 50% (I'll be verifying this with testing that I will post later), and starting sure won't take that much power and then it will be topped off when the engine starts. If you can ensure that you aren't going to cycle it deeply at all as is the case for me, you can get away without a BMS. For anything else I'd suggest using one. At the very least you need a way to monitor the cells and watch it so they don't charge up too far or discharge too low. This is a pain and it is how I used to do things on my PHEV kit on the Prius. It gets old fast and you'll want something automated IMO.

Daox 07-24-2012 02:16 PM

Speaking of testing, these are my plans. I will test these cells with my powerlab6 charger. This can charge/discharge at up to 40A (2C for these cells). I will do charge/discharge cycles on these cells at .5C, 1C and 2C. I'll post up the graphs so you can see the voltage sag etc. I'll also post some graphs from my mottcell cells to compare.

user removed 07-24-2012 04:15 PM

In my application the cells would only run a motor to pump up hydraulic pressure. There is no need to monitor or control the power level since there is no necessity to control vehicle speed. The motor would be switched on and off by pressure level switches in the accumulator.
Charging would be strictly when the vehicle was sitting still from the 220 outlet in my garage.
How far the pack was discharged would determine when the Diesel engine took over. I would not use it to recharge the pack.
Similar to the Volt.
Right now I plan on using only the 9 HP Diesel, but if a battery pack was within a reasonable price range that plan could change, even to pure electric propulsion, but in either case there would be no electrical regeneration at this point. It would be purely hydraulic.
The useable capacity of a 10 KWH pack would be useful information. At $4.4k it looks interesting, but I may build the pure Diesel version first, then an electric option later.

regards
Mech

Daox 07-24-2012 04:23 PM

In that case you would need definitely a BMS to detect when the battery is fully charged when plugged in, and also when it is depleated so you can switch over to the engine.

bennelson 07-24-2012 04:41 PM

I like that you needed a micrometer to show how thick they are.

Glad you got them home without short-circuiting!

In all seriousness, that many amps, with terminals that close - be extra careful with anything conductive.

One thing I like about group 31 batteries is that their terminals are farther apart than my socket wrench is long! To me, that's a great safety feature!

Ryland 07-24-2012 06:43 PM

Are the tabs foil or thicker?

bennelson 07-24-2012 06:54 PM

They are almost like soda can aluminum, but just a little softer.

Daox 07-24-2012 08:51 PM

I did measure the tabs. They are 1.775" wide x 1" tall. The positive terminal is aluminum and is .010" thick. The negative is plated copper and is .007" thick. So, as Ben said they are very thin. I'll add this info to the first post.

Frank Lee 07-24-2012 10:43 PM

Quote:

Originally Posted by Ryland (Post 318090)
I'm blown away by how cheap lithium batteries are now!

Hmmm, 60 volts' worth of those would look mighty fine on the Songi! :thumbup:

Daox 07-25-2012 08:09 AM

3 Attachment(s)
I made some quick end plates last night so I can hook the cells up to my powerlab charger. Nothing fancy, but they're quite similar to what I plan to use when the pack is assembled. I do have a slight concern about using the nylon threaded rod for a long length of cells (for a much larger pack), but for something small like this it should do just fine.


Just two plates of 6061 aluminum with holes drill on the ends for the nylon threaded rod to go through and clamp down on.
http://ecomodder.com/forum/attachmen...1&d=1343217882


Plates installed. I'm not sure if I'm going to tap the plates for additional connections or what yet... We'll see.
http://ecomodder.com/forum/attachmen...1&d=1343217882

http://ecomodder.com/forum/attachmen...1&d=1343217882

jjackstone 07-25-2012 11:29 AM

I would suggest cleaning the aluminum with alcohol or ethanol to remove the ink, factory machining residue, and general oxidation. Additionally I was thinking that a conducting gel such as heat sink compound or similar might make for better conduction between the tabs and the aluminum stock(that's just a theory though).
JJ

Ryland 07-25-2012 03:55 PM

I forgot all about the dissimilar metals like copper and aluminum, they should not be in contact with each other! aluminum oxide is also not conductive, so I'd get something like a scouring pad, to clean up your contacts then grease them with dielectric grease or conductive aluminum never seize on the aluminum side and copper never seize on the copper side.

oil pan 4 07-25-2012 04:35 PM

Any ideas where we can get some of these if there is no drive green expo coming to town?

These cells seem like they could replace my 123A LiFePO4 cells for a little less money and in a unit half the size.

http://ecomodder.com/forum/showthrea...s-18547-4.html
The battery I built is posted on the dieselplace link, its crude but effective.

Daox 07-25-2012 04:49 PM

I bought my cells from Eric Powers (user name ericbecky). He did a group buy on the cells and I reserved a few before they were all gone. He is currently out of stock but was considering doing another group buy when I talked to him last weekend.

Ryland 07-25-2012 11:05 PM

There are a few people selling them on Ebay too a123 20ah | eBay

You can also buy them directly from China http://www.alibaba.com/showroom/a123-20ah.html

From what I've heard how these came to be is that the factory that is making them had a contract to make them, tooled up to make them then something changed and A123 systems was no longer going to use that factory, no idea who's choice that was, but the factory decided to make them anyway and sell them on their own. so as I understand it, it's a little shady, but they are still good cells and people are using them for good projects.
The same kind of thing happened with the E-tek motors, I did some work for one of the guys who helped design that motor and they tooled up in China to build it but before it was supposed to be released they found out that the factory had opened early and was selling it on their own, law suits fallowed and the improved version of the E-tek motor was never released.

oil pan 4 07-26-2012 11:03 AM

Thanks.
Next starting battery I build will be based off something like these.

Daox 07-26-2012 12:19 PM

The vendor Eric gets his cells from, Victpower (min order of 300 cells), has a pretty good reputation. I would be very cautious buying from elsewhere. As Ryland said there are a lot of grey market cells floating around, some without the tabs on them, others may not even be A123 cells.

oil pan 4 07-26-2012 02:34 PM

I may have gotten ahold of those grey/black market cells for my 28 cell LiFePO4 battery. The 28 cell battery seems to have about as much power as its 20 cell counterpart.

I will be looking the next group buy, don't need them now but when I do I will want between 4 and 12 cells.

Daox 07-26-2012 03:09 PM

Quote:

Originally Posted by Ryland (Post 318646)
I forgot all about the dissimilar metals like copper and aluminum, they should not be in contact with each other! aluminum oxide is also not conductive, so I'd get something like a scouring pad, to clean up your contacts then grease them with dielectric grease or conductive aluminum never seize on the aluminum side and copper never seize on the copper side.

I posed this question to the local makerspace and got some interesting answers.

1) Aluminum oxidizes pretty much immediately.

2) The battery manufacturer knows this and likely plated the aluminum with something that doesn't oxidize. This doesn't help my spacers though. So I'm still trying to figure out what to do there. I'm still not even sure that the very thin layer of aluminum oxide will create that much resistance.


Also, I think I mentioned it, but the copper lead is plated with something. I'm not sure what. My first guess would be tin, but it might also be zinc. However, zinc is much farther up on the galvanic series than tin...

Daox 07-26-2012 03:36 PM

Just got some more info.

Apparently the copper terminal is plated or is made of 'aluminized copper', so attachment to an aluminum spacer should not be an issue.

Also, a makerspace member recommended "noalox". It claims to:

•Anti-oxidant
•Reduces galling and seizing on aluminum conduit joints
•Suspended zinc particles penetrate and cut aluminum oxide
•Carrier material excludes air to prevent further oxidation
•Improves service life of aluminum electrical applications
•Costs a lot!

Ok, last one I added. :) But, with that new info and some noalox I think I should be in pretty good shape.

Cobb 07-26-2012 07:54 PM

:turtle:Oh, ok. Yeah, I am sure those will do better in your gasser vs your hybrid. Id even add a solar panel too if you were me.:thumbup:

Ive wanted to replace the lead acid battery in my Insight with something like a few prius sticks, IMA sticks or a lifepo4 battery for some time now. Price has been the main hold up. From what I see the Honda charges the battery for the first few minutes after start up, then when the voltage falls before 12.6 volts. The only exception to this is regen braking. When ever you regen it also activates the charging system. As we know lead acid batteries need a long continue low amp charge vs a short high amp, whish is what the Honda does by way of the ELD and a dc to dc converter.

Although I replaced the motorcycle battery the car came with with a group 51, I did find 2 more mpg from disconnecting the power steering and see an effect with use of the lights, drls, hids vs halogen, etc.

Good luck.

Daox 07-27-2012 08:28 AM

7 Attachment(s)
I've pretty much finished up the first round of testing on the first cell. Capacity wise it isn't quite up to the 20Ah spec (I don't have the 1C discharge Ah number handy), but its fairly close. I also found that with my mottcell cells that sometimes multiple cycles tended to increase the capacity almost like the cells needed to be exercised. However, this wasn't true for all the cells I tested.

Anyway, here are a few charts.


The first test was to charge/discharge at .5C (10A). My laptop went to sleep during the charge so I only have the discharge which is thankfully the more useful (to see voltage sag).

http://ecomodder.com/forum/attachmen...1&d=1343390925





I have a few more charts from my 1C (20A) tests. The first shows the voltage over time for the discharge cycle.

http://ecomodder.com/forum/attachmen...1&d=1343390955



This shows the volts over time for the charging cycle.
http://ecomodder.com/forum/attachmen...1&d=1343390955



Below you'll see the Ah put into the cell over time.

With these two charging charts, I can fairly accurately estimate the state of charge (SOC) that these cells will sit at when they are connected to my alternator on the Paseo. For example, lets say my alternator puts out 14V. 14V gives us 3.5V per cell (well below the 3.65V max charge voltage, so no need for a BMS). By looking at these charts we know the cells hit 3.5V around the .9 hour mark. By looking at the capacity chart at the .9 hour mark it looks like I'll have close to 17Ah stuffed into the batteries. This is actualy quite a bit more than I thought which is nice. Though, I do have to verify my alternator output. If the alternator puts out 13.5V (3.375V/cell) we're looking at a capacity of around 10Ah. So, a little voltage variance goes a long way.

http://ecomodder.com/forum/attachmen...1&d=1343391192







Next up is the 2C (40A) tests. You can see the voltage is starting to sag a tiny bit more, but its very reasonable. I don't have a mottcell chart handy right now, but I'm pretty sure there is more sag at 1C on my mottcell cells than there is at 2C with these cells.

Here is the voltage over time for the discharge cycle.
http://ecomodder.com/forum/attachmen...1&d=1343391809



Here is the voltage over time for the charge cycle.
http://ecomodder.com/forum/attachmen...1&d=1343391809



And here is the capacity over time for the charge cycle.
http://ecomodder.com/forum/attachmen...1&d=1343391809

Daox 07-27-2012 08:39 AM

I will also mention I monitored cell temperatures here and there. The cell was simply sitting on a board, no insulation or end plates squishing things together.

At .5C there was almost no noticably increase in temperature. I shall recheck this when I test the other cells.

At 1C dis/charge I saw a pretty constant 4F above ambient in cell temperature. The cell heated up very uniformly. The terminals I thought would heat up as well, but they always remained at a lower temperature than the cell. This may be due to the large aluminum blocks on them.

At 2C there was a good temperature increase. Probably more like 10-12F. I'll also have to verify this because I'm not 100% what ambient was.

drmiller100 07-27-2012 10:19 AM

i'd be surprised if the prius is as low as 14.0 volts when the starting battery is fully charged and certainly it will not be lower.

Thank you for the research.

It sounds like these would be VERY nice batteries for an electric car. I've gotten a bit of push to build an electric verison of my trike. Sounds like this woudl be a good solution.

Daox 07-27-2012 10:26 AM

These batteries won't be going in the Prius, they'll be used as the starting battery in my Paseo. They'll be replacing the group 24 lead acid battery that weighs about 40 lbs with this which will weigh about 5 lbs.

Daox 07-27-2012 10:54 AM

Darin remembered that there is another EM member using an even smaller lithium pack as a starting battery. Here is the link to his post.

http://ecomodder.com/forum/showthrea...tml#post318908

Cobb 07-27-2012 10:35 PM

So much for the 900 mah that is stamped in the left front corner. :eek: Wonder if they are purposely mislabeled for customs reasons?

Strangely after that gorup buy I remember seeing an article about a batch of defected cells that had a crease in them, like those.:eek:

Think I got a good dozen of IMA cells that are worth a dam and similar in capacity. I am going to try and make a 14 volt 6.5 amp hour battery out of them for under the hood. Then hook a 5 watt solar panel to that as well. :thumbup:

Then of course remove the 12 volt starter with the lead acid battery. :eek:

drmiller100 07-28-2012 12:10 AM

Quote:

Originally Posted by Daox (Post 318965)
These batteries won't be going in the Prius, they'll be used as the starting battery in my Paseo. They'll be replacing the group 24 lead acid battery that weighs about 40 lbs with this which will weigh about 5 lbs.

sorry, I should have read more closely. I understood you were using it as a starting battery for an ICE.

My experience is EVERY modern normal running vehicle has 14.0 to 14.4 or so volts, fully charged, and engine running.

I have a small automotive shop, and we specialize in fuel injection and electrical issues, and battery voltage at idle is something we pretty much always check.

Daox 07-28-2012 10:42 AM

You are correct drmiller. Your post reminded me , so I just went and checked it. The voltage varied from 14.2V to 14.4V, but it mostly stayed in the 14.3-14.4 range. So, we'll say 14.35V as an average.

14.35V gives us 3.575V per cell. That is going to leave these cells pretty much topped off all the time. Max charge voltage is 3.65V per cell and you gain very little capacity between 3.575V and 3.65V according to the charts.

I actually wouldn't mind a slightly lower voltage, but this is what I have. I don't believe there is an easy way to adjust the alternator output. Someone correct me if I'm wrong. But, this should do just fine.

Daox 07-28-2012 11:06 AM

2 Attachment(s)
I also wasn't able to find the 'noalox' product at the local store that was supposed to be a distributor. What I did find was this stuff. It claims to improve conductivity and protect aluminum electrical connections.

You're supposed to work this paste in with a wire brush or emery cloth to both sides of the connection, then put them together. Sounds to me like its attempting to stop the oxidation before it starts. This sounds like a different product than the noalox which claims to 'cut aluminum oxide'.

I'd like to test it to see how well it really works. So, I'm thinking I'll cut a bunch of aluminum spacers and stack them together and measure the resistance. Then I'll use this stuff and reassemble the stack and measure resistance. Ideas are welcome for a better testing procedure.

http://ecomodder.com/forum/attachmen...1&d=1343487568

http://ecomodder.com/forum/attachmen...1&d=1343487568

Daox 07-28-2012 11:12 AM

2 Attachment(s)
So, to clarify, it looks like Ox-gard and Noalox are fairly similar. I mention this because my Ox-gard was $4 for a 4oz tube vs Noalox at $12 for a 4oz bottle.

Here is the MSDS data for Ox-gard:
http://ecomodder.com/forum/attachmen...1&d=1343488220


And here is the MSDS data for Noalox:
http://ecomodder.com/forum/attachmen...1&d=1343488220

jjackstone 07-30-2012 11:16 PM

Daox,

Don't know that you'll be able to measure much difference in resistance. The big gain with this type of product is that it fills in all the little unseen pits and holes found in most unpolished materials essentially creating a larger surface area. That is why the conductivity increases. JJ

Daox 07-31-2012 08:07 AM

The paste is not conductive. I tested it. I would think the main benefit is from being able to make a solid aluminum-aluminum connection without two layers of aluminum oxide (an electrial insulator) between them.

Small update. I'll finish up testing cell #3 today. Number 4 should be done a couple days after, then I'll work on assembling them into a 12V pack.


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