About li-ion battery charge

[Lagoethe]

Hello

I learned a lot while reading this site: http://batteryuniversity.com/learn/article/charging_lithium_ion_batteries
After reading it, I wonder how battery chargers managed to respect this graph. I mean, are battery charger AC/DC converters only and the management of the current and voltage is made by the BMS and battery itself, or are chargers "smart" (I hate this word) systems ?

To finish and that's the real point, should I take care to the charger when i purchase a battery pack +BMS +Charger?
for example: http://www.cycloboost.com/41-batterie-lifepo4-48v-15ah-velo-electrique.html

Bye

 

[liveforphysics]

Holy Sh*t.

Battery University evidently is living in the 1990s.
You can forget everything it says on that page.

 

[Lagoethe]

Thanks for the answer...
so...

How 2010s battery charges?
Is there caution to take for charge or not?
Is there a web site that explains the management of the charge of Li-ion batteries?

Thanks

 

[dogman dan]

This is it. But you'll have to dig it out of some long discussions. What kind of lithium are you interested in? Lipo is the hot topic these days.

Now that I checked out the cylcoboost website, I see you are looking at some lifepo4. Go to pingbattery.com for batteries in the 30 amp discharge category. good for typical bike kits. Comes with a fairly reliable bms and "smart" charger.

For high performance, go to Hobby King, and see real high discharge lipo stuff, along with chargers that actually are smart. Most of us are human bms's using this type. We depend on knowing our battery range, and use of low voltage warnings, watt meters, etc to know when to stop riding.

 

[neptronix]

What dogman said. Ping batteries ( LiFePo4 ) are a nice, braindead solution that you don't have to worry about and are also reasonably priced.

For Lithium Polymer, I have an iCharger from hobbyking that is pretty intelligent, and also tells me exactly what's going on with the charge. It also has many failsafes to prevent you from doing something really stupid. I just got into this electric bike stuff ~5 months ago and i can handle it

 

[Lagoethe]

Thanks
I think I'll buy those ping batteries to begin.
I was wondering if any caution during charge should be taken to create regenerative brake. I mean during regenerative brake, the current or voltage isn't stable. Would this current damage the battery?


One last thing which isn't about charge.
Ping batteries: 48V 20Ah + BMS =9.9kgs
A123 prismatic: 3.7V 20Ah = 480g so for a 48V Pack without BMS it is 6.2kg
So why not using A123 ? I'm pretty sure there is a reason... but I don't find it.

 

[texaspyro]

So why not using A123 ? I'm pretty sure there is a reason... but I don't find it.

The source for those batteries dried up...

 

[Samba]

A123 prismatic: 3.7V 20Ah = 480g so for a 48V Pack without BMS it is 6.2kg

A123 says they are 3.3 volts, they are LiFePo4 which are usually considered 3.2v
In any case it takes 15 cells in series in series to make 48v. The ping is 16s4p - actually 51.2 volts They are lifepo4 also but 5ah pouches
a 16s1p of the A123 is 7.7kg


I think if you are going to parallel all the leads of 3 packs, you'll want to make sure they are all at a similar state of charge - so charged and balanced - before you parallel them.

 

[neptronix]

I was wondering if any caution during charge should be taken to create regenerative brake. I mean during regenerative brake, the current or voltage isn't stable. Would this current damage the battery?

Yep, that is a problem. Regen can only take in so much energy since batteries can only charge at a certain rate.
Most batteries top out at about 1-2c for charge rate.
I believe A123's are unique in that they can take a charge far quicker than any lithium battery.

So a well programmed regen controller will discard a good 75%-90% of the energy it takes in, to protect the batteries

So why not using A123 ? I'm pretty sure there is a reason... but I don't find it.

Like the previous poster said.. they are hard to find. For some reason, A123 doesn't want to sell to hobbyists or small companies. They act like they are owned by an oil company, by holding on to a killer product and not selling it. I wonder

If you want low weight, and low cost, turnigy/zippy packs are the way to go. But be prepared to be your own human BMS.

 

[Lagoethe]

So a well programmed regen controller will discard a good 75%-90% of the energy it takes in, to protect the batteries

But, why not using another source of temporary electric energy storage. I think of capacitors but there maybe other technologies (I don't know). What is the problem of using them?

A123 doesn't want to sell to hobbyists or small companies

So sad...

But be prepared to be your own human BMS

No, no braindead,...

Last question: are there other famous manufacturers of 20Ah 3.7 lithium prismatic bag with Ah/kg near from A123 with a good reliability, ...

Thanks

 

[liveforphysics]

So a well programmed regen controller will discard a good 75%-90% of the energy it takes in, to protect the batteries

I wish you could teach me the trick to just discard unwanted energy.

 

[liveforphysics]

Lagoethe-

A modern EV application battery has an internal resistance about 2-orders of magnitude lower than when battery university wrote that article on charging, and completely negligible self-discharge properties.

This means, a simple CC/CV supply can give them exactly what they need to charge with no fancy charge algorithms or C/10-20 cut-off's etc.

Modern LiPo (like Nano-Tech's) can be charged at >10C rates, meaning full charge in 6minutes. It also has the highest energy and power density available right now (for reasonably priced batteries at least).

So, in your example with a 20Ah 48v pack, it could handle regen charge rates of >10KW, which is enough to instantly cause the tire to skid on pretty much any bicycle, making it adequately high enough to get every possible bit of regen energy you wish to capture.

On the other hand, regen on a bicycle is unfortunately mostly worthless, as most of our energy goes into wind-drag rather than stored inertia. Expect to see maybe 5-10% range increase at the most from regen for normal applications.

 

[Lagoethe]

Thanks for the answers

A modern EV application battery has an internal resistance about 2-orders of magnitude lower than when battery university wrote that article on charging, and completely negligible self-discharge properties.

As you told me I forget battery university now.

This means, a simple CC/CV supply can give them exactly what they need to charge with no fancy charge algorithms or C/10-20 cut-off's etc.

I still don't understand how the charge on battery is made: CC/CV mean constant current and constant voltage (how would that be possible?) , or constant current or constant voltage. The voltage of the battery goes up with time isn't it? Really sorry this is a newbie question who have never load a battery (or at least taken care of how it works).

Modern LiPo (like Nano-Tech's) can be charged at >10C rates, meaning full charge in 6minutes. It also has the highest energy and power density available right now (for reasonably priced batteries at least).

They seem very very interesting but i'm afraid of the care-taking of this technology. I mean it's not as simple as: buy 4*10s plug them together. Charge them with a single charger, one operation, go to bed, take the battery, plug on your vehicule, let's go. As I wrote before, I'll begin with a battery pack for dummies

On the other hand, regen on a bicycle is unfortunately mostly worthless, as most of our energy goes into wind-drag rather than stored inertia. Expect to see maybe 5-10% range increase at the most from regen for normal applications.

I agree with you. I think that for in-town applications (thinking of european ****** trafic in big cities) the regen would be more 10-15% (based on the fact that I spend 1/3 of my time accelerating when i drive, 1/3 seeing the red light, 1/3 braking - I exagerate but I'm not so far from what happens for real). And 10% is huge.

 

[liveforphysics]

CC/CV means, constant current until the SOC (state of charge) climbs to a point at which it's able to hold a constant voltage.

It looks like for your application, the Ping pack is an excellent place to start out, and familiarize yourself.

 

[dogman dan]

If you do settle on a ping, for a starter battery on a bike with a low amp (20-25 amps) controller, 48v 15 ah is a good size. The 20 ah is a bit heavy and cumbersome on a bikes rear rack. So is a 48v 15 ah, but less so, and it's tolerable to ride.

One way to simplify lipo, is to run 12s. Halfway between 36v and 48v nominal voltage, You can get it with two 6s batteries. So unplug a couple plugs, hook up to two chargers, and it's really not so bad to charge the lipo.

Once you get the lipo, you'll be playing with 72v soon enough though.

 

[dangerzone]

Last question: are there other famous manufacturers of 20Ah 3.7 lithium prismatic bag with Ah/kg near from A123 with a good reliability, ...

Thanks

If we are talking about Lithium then there are Kokam prismatic cells 40Ah (built into electric ariplanes), Li-Tec 40Ah (electric Porsche and Mercedeses use them) then there's Thundersky 40Ah up to 100Ah and they all weight around 40Ah per kilo, so A123 are a bit better than that and have a longer life cycle...

Then there's the French SAFT batteries which are even produced in USA but I guess they are only for military use and I even doubt they would be affordable or reasonable. Headway plans to start selleing their prismatic batteries soon, should be way cheaper than A123 but I dunno if they'll match the power or quality, we'll see.

Apparently there are a lot of guys riding bikes on those RC plane batteries, many of them have them for quite some time. Yet there are many who dislike them, if u overcharge or neglect them for some time they turn to shit instantly, some of them even burst to flames. The Kolibri battery which made the Audi A2 drive for more than 600km uses those, we'll see if they have come up with a good solution so far...

 

[Lagoethe]

I put this subject off the grave because i'm thinking of charging the battery with my own system.
There will be different charge possibilities
-230V 10A
-230V 64A
-from the braking. (in tests)

so I'd need a little bit precisions about:

CC/CV means, constant current until the SOC (state of charge) climbs to a point at which it's able to hold a constant voltage.

Does that mean that the charger act like this:
1st: The controler controls the current amperage (fixed at 1C max). Voltage = battery voltage
when the voltage = 4.2V/cell
2nd: The controler controls the voltage (fixed at 4.2V). current = the current drained by the battery.

Have I well understand or did I make a mistake?