LiPo V Lifepo4

[neptronix]

I love how liveforphysics talks up the NMC batteries as if lifepo4 was dead but fails to provide any reasoning when asked.

So let me do my best.
The 'tri-metal' batteries such as NMC, NCM, and other various lithium-nickel type batteries seem to have fantastic capacity per pound. Go look at allcell's packs at chicago electric bikes for an example:

http://www.chicagoelectricbicycles.com/Batteries.html

36v 10ah weighing in at 4.8 pounds.... that's including a heat dissipation material, tape, a BMS, and wiring.
An equivalent lipo pack would be about 6 pounds, in cell and wire weight alone.

Given that weight is a big issue in bikes.... this is quite a big deal.

Mind you, these are 1-2C cells, so they are not so high performance. Meanwhile there is unobtanium stuff out there that will do 10C or above, and charge at high rates as well. But generally... these are newer chemistries that are showing a lot of promise.

http://www.batteryspace.com/linicomn-cells-packs.aspx

Here are some of the unobtanium cells. Battery space has been listing them for a while. I have called and emailed repeatedly and cannot get a price out of them.

With safety near or equal to lifepo4 with better capacity per weight than lipo, i think this is the battery flavor of the future.

 

[jonescg]

Those ~170 Wh/kg cells would be great if not for the cylindrical format. Pouches would be far more convenient. Still, let's hope the unobtanium reserves open up a bit

 

[dogman dan]

Lifepo4 is not dead yet. It hasn't even begun to see it's ultimate usefulness. But it may not be the end game battery for the ebike or other EV's. I think lifepo4 will eventualy become the battery of choice for golf carts, even if it doesn't have the small size and range we want in a car. I am amazed the golf industry hasn't figured out yet, that doulbe the range on carts means you can have the whole fleet out on the course all day, instead of half the carts back on the charger by afternoon. Huge savings to have to own less carts.

 

[theRealFury]

I think lifepo4 will eventualy become the battery of choice for golf carts, even if it doesn't have the small size and range we want in a car. I am amazed the golf industry hasn't figured out yet, that doulbe the range on carts means you can have the whole fleet out on the course all day, instead of half the carts back on the charger by afternoon. Huge savings to have to own less carts.

Its already happening... you can even buy lithium golf cart replacement battries now such as these made in the USAbut unfotunately the price needs to drop a LITTLE first lol.

 

[Bazaki]

Can you guys confirm that Lifepo4 is really much safer then Lipo ?
I'm not afraid of overcharging/overdischarging my lipo batteries, since I monitor it really good.

But I'm afraid for puncture a lipo cell, since I ride off road al lot. What would happen if a Lifepo4 cell got punctured ? No risk at any fire ?

 

[theRealFury]

Its not as clear cut as saying lifepo4 is safe and lipo isnt im afraid. I have seen both lipo and lifepo4 go up in flames when punctured and the same when overcharged. I have also seen lipo cells with massive slashes in them right through the different layers inside and not so much as getting warm... The main thing you have to realise is that no battery technology is safe. I once had a tiny little 3v lithium button cell explode on me because it shorted, had metal shrapnel stuck in my finger and got some nasty taste in my mouth that could have been bad for my health. Best to just protect any battery as though its fragile... that way you dont have to worry when it takes a trip down the asphalt by its self.

 

[wojtek]

I agree.

I wouldn't say Lifepo4 are better for beginners. There are ONLY few rules about taking good care of Lipo and you are as safe as using any other chemistry.
When i started ebiking, i knew NOTHING about battery. Chemistry classes long forgotten. But i followed the rules mentioned in ES and was using successfully Lipos for 15 000km in last 2 years.

If you are a beginner, you gotta know what you are doing when building a pack. Whatever chemistry it is... And learn a lot and experience! That gives more confidence and peace of mind, than trying to chose "safe" battery.

 

[neptronix]

lifepo4 is the safest lithium chemistry i know of.
liveforphysics had a very hard time getting various lifepo4 to ignite.
lithium cobalt polymer ( macbook batteries, RC lipo etc ) on the other hand - no problem!

Check out his testing videos..

http://www.youtube.com/watch?v=8IBapfB0Imo

 

[hinv]

I purchased a bunch(16) of these:
http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=18631
because they were the cheapest way to build a powerful pack.
My questions are:
Should I expect quality problems from these Turnigy batteries?
Was it wise to get the hardcase ones, or did I just waste some weight?
Did I buy the right charger to go with them?
http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=18918

It says 6s so I am hoping that it can go up to 6s otherwise I will have to do some funny wiring for the balancing wires...which I might do so I can charge in bike like doctor bass does it.

Thanks,
hinv

 

[theRealFury]

I purchased a bunch(16) of these:
http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=18631
because they were the cheapest way to build a powerful pack.
My questions are:
Should I expect quality problems from these Turnigy batteries?
Was it wise to get the hardcase ones, or did I just waste some weight?
Did I buy the right charger to go with them?
http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idProduct=18918

It says 6s so I am hoping that it can go up to 6s otherwise I will have to do some funny wiring for the balancing wires...which I might do so I can charge in bike like doctor bass does it.

Thanks,
hinv

The Lipo you bought is good stuff and really cheap... wish I lived in USA for all these cheap Lipo It was definitely wise to buy the hard case Lipo as the main danger for Lipo is impact damage and the hard cases will help to prevent that (to some extent).

As for the charger… it all depends on how you intend to connect your 16 packs up with parallel and series connections. Are you doing 16S 4P with 4 packs in series and 4 packs in parallel or some other configuration?

I’m sure that charger will be able to charge your pack but I don't think it would have been my first choice I’m afraid. IIFC each charge port is only 50W max current so if you are charging a 4S pack with 20AH (as per above setup guess) then each 4S pack would take 7 hours to charge... that is if the charger can handle running all 4 circuits on full 50W output for 7 hours without blowing.

Edit: Edited for lousy spelling and grammar. I think i need to go back to school.

 

[dogman dan]

Good battery choice, so so charger choice. Some have reported problems with that on. Apparently , really good chargers get pricy for lipo. But it will do you for awhile. You'll need a power supply for it. The meanwell ones are the favorite for many of us.

Hardcase is cool, you can just throw em in a bag and ride. Otherwise you need to do something to help protect against poking or rubbing holes in the packs.

 

[ToughRowToHoe]

Neptronix, I just checked and it appears those unobtainium batteries (LiNiCoMn 18650 Cylindrical Rechargeable Cell: 3.7V 2000mAh (7.4Wh, 6.0A Rate) (0.6)) are shown listing for $6.95 each: http://www.batteryspace.com/linicomn-cells-packs.aspx

 

[ToughRowToHoe]

Hi Magudaman,

That's interesting, thanks.

LiFeP04 may have a longer calender life, the only thing is the cycle life. It may even have 1000 cycles but it will still last only 2-3 years from usage, so 10 year calender life is irrelevant for this purpose.

If one was to ride 12 miles a day (based on my own setup) that would be maxing out the pack and 100% dod (or almost charging to 4.15 ) that's why I said 400 cycles in the beginning. That would equal 4368 miles a year for 12 miles 7 days a week.

So 1000 cycles x 12 = 12000 miles capability of the 10ah LiFeP04 pack so roughly 3 years at just 12 miles a day, or half if you had to charge twice and do 24 miles a day!

Of course you could increase the ah to 20 if you wanted and that would mean your pack would last 6 years, but that's heavy!

I think I would rather the LiPo because it's lighter and it does the job, and it's cheaper to buy even if the LiFep04 lasts longer to begin with, with the advances in battery technology something better will be available in 3 years and I'm sure LiPo will be a lot cheaper then too making it even more attractive. I don't want a heavy LiFeP04 when I know better lighter batteries are only a few years away. And my Light LiPo does the job for now!

I don't think it's long before we can ride around with a 20ah pack that weighs the same or less than a 10ah LiPo pack!

Actually, I'm pretty sure the underlined part above is incorrect. So long as the usage doesn't change and max voltage charge is adjusted down slightly, the cycle life should increase at an almost exponential rate for the much more stable Fe chemistry.

For most chemical batteries, using smaller amounts of the battery at lower C rates decreases the mechanical/chemical stresses that lead to battery wear per that chart Magudaman posted.

Lipo does not benefit nearly as much because it has side reactions that shorten its life. Babying them doesn't help nearly as much because the side reaction calendar life clock is ticking with just about any usable charge.

Babying Fe and the other stable chemistries makes a big difference in how long they will last. Babying them does come at the cost of making them even heavier and more expensive up front.

 

[hinv]

Thanks for the answers. I'm glad to se that I made a good choice for batteries. The cgarger will get me by too.
Since I work on SGI computers, I have some 48v 1500watt non adjustable power supplies at the shop. Could I just use one of these and a battery medic while charging 12S3P? Will the battery medic do the ballancing while I charge?