LiPoly evolves while LiFePO4 is stagnant?

[methods]

You are platinum after 10 purchases.
I asked since it used to be 7 purchases back in the day.

I have spent many thousands though. . .

the charger luke posted is the one to get.
Dont be fooled by the cheaper chargers that only run 50W or 100W.
250W is the only way to roll :wink:
Thats 10A on a 6S pack. Perfect for charging in parallel

Have a look at the power supply that Chargery puts out too.
Thing works like a champ.

LUKE: Hey, you test that charger yet to see if the outputs float?
If they do I may consider using 2 or 3 of those on my other bikes for safe charging.
I am starting to set people at my work up and they need SAFE solutions.

-methods

 

[bearing]

wow, those are cheap. How would you hook those up in series? Is it hard?

Does this charger work with these packs?

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8582&Product_Name=ZIPPY_Flightmax_5000mAh_6S1P_20C_

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=3823&Product_Name=3E_Lipo_Charger_2-5Cell_w/_Balancer

Thanks

These are not the ones in the first post of the thread, right?
They were 40c/80c these are 20c/30c.
Do you have any data on these, like disharge curve and internal resistance?

 

[morph999]

wow, those are cheap. How would you hook those up in series? Is it hard?

Does this charger work with these packs?

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=8582&Product_Name=ZIPPY_Flightmax_5000mAh_6S1P_20C_

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=3823&Product_Name=3E_Lipo_Charger_2-5Cell_w/_Balancer

Thanks

These are not the ones in the first post of the thread, right?
They were 40c/80c these are 20c/30c.
Do you have any data on these, like disharge curve and internal resistance?

hmmm, I thought they were the same ones. I'll have to check. I don't know discharge time. I was hoping someone could help me. I'm very new to this. More C the better, so a 40C would be better than a 30C right?

 

[liveforphysics]

If cells are free, higher "C" rating with the same capacity is always the better choice. This is because the lower internal resistance cell will always be the cell that lasts longer and stays cooler and charges faster than a cell with higher resistance. The performance of the bike will also stay very stable through the ride.

However, the 40c/80c cells cost 3 times what the 20c cells cost. You can get 25c and 30c cells for about 20% more money than the 20c cells.
In all honestly though, even the worst LiPo with just 20c discharge is still going to be a monster for an e-bike. It's just going to get a little warmer, not have quite as solid of voltage stability under load.

 

[bearing]

Is there a standard for the voltage drop at the C-rating?

The cells in the first post seemed to drop about 0.4V at 40C. Can it be expected that cells with a 20C-rating drops about 0.4V at 20C then?

 

[liveforphysics]

Voltage drop is a function of internal resistance.

The lower the internal resistance, the less the voltage drops.

C rating does seem to be inversely linked with internal resistance, however there is another factor that throws things way off.

The manufactures of different cells all have different ideas of what "steady state discharge" or "burst discharge" actually mean. Some 20c cells are very conservatively rated, and actually are better performers than some brands 30c cells. This makes it tough to know without just looking at a discharge graph of each cell type.

If you are looking for discharge graphs, various RC forums are full of them.

 

[bearing]

I've been googling for:
zippy flightmax discharge graph
zippy flightmax discharge curve

and similar without any luck. If anyone have seen a discharge curve for these cells, please let us know.

 

[linear]

These Zippy packs sure look good at this point from reading the thread. This is really light weight and lot better value than a lot of other options out there.

 

[recumbent]

Although these packs are small and light, it seems we have to purchase about 6 of them and wire them in series and parralel and then charge them seperately also.

I wish there was a 48 volt charger for li-poly batteries.

The reduced lifecycles (about 500) would'nt be such a drawback, because the light weight, small size and low internal resistance is such a great bonus.

 

[methods]

Although these packs are small and light, it seems we have to purchase about 6 of them and wire them in series and parralel and then charge them seperately also.

I wish there was a 48 volt charger for li-poly batteries.

The reduced lifecycles (about 500) would'nt be such a drawback, because the light weight, small size and low internal resistance is such a great bonus.

Not all true
The 6 packs part is true if you want to have about a 48V 15Ah pack

First of all Lipo does not require any type of special charger. Neither does lead acid.
You dont have to charge them in parallel or any other configuration other than the configuration that you are going to use them.


You wire the packs in series parallel once.
You bring out the balance taps.
Spend $10 at hobby city and put all the parallel taps in parallel.
Now your pack has (2) 6S balance taps coming out.

You tie that into an off the shelf 12S balancer made by Hyperion. Costs about $60. That will provide you with Balancing, 3.05V LVC protection, and 4.3V HVC protection.

You charge with ALMOST ANY standard 48V power supply. Your charge current is dictated by the max current of the supply
You just set the voltage of the supply to the voltage of your pack and you have a "lipo charger"
The power supply will run in constant current (CC) till it gets close to the HVC then it will quickly move over to Constant Voltage (CV)
Simple as that.

You charge through the hyperion balancer that will allow up to 15A charge rates. If you want to charge with higher current you can do so by swapping out 2 fets.

If you choose to do something like the "24 channel BMS" you dont even have to set the power supply to the HVC of your pack. You can use 50V or 51V or whatever
You get balance protection, charge protection, and discharge protection

Lipo is no mystery.
Absolutely no different than charging A123 cells.

-methods

 

[Russell]

I wish there was a 48 volt charger for li-poly batteries.

Batteryspace has a 14 cell (51.8V) LiPo charger but your pack would need to have its own BMS.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4715


-R

 

[methods]

While I am on my soap box, I need to vent.

What is with all these companies selling these ridiculous computer controlled chargers claiming that they are "safe...errr"
The models with balancing, sure. Those are definitly more safe since they make it impossible to take any cell over 4.2V (but you can do that other ways)
The models that dont require integrated balancing are *MORE DANGEROUS* than using a power supply.

Case in point: Garry blew up a Lipo once while charging it. The reason is because the charger sensed his lipo pack was a 4S when it was really a 3s.
This caused the charger to barrel right past HVC and blow the pack.

Having a dedicated power supply for a dedicated battery does not invite that chance for error. The supply is set to an exact voltage once and only once.
The adjustment screw is then glued down.
The supply will *never* push more juice into your pack than HVC
The only thing to ensure is that the user keeps the pack in balance.
This is done by permanently attaching a balancer to the pack

You know. . . These hobby packs dont go out of balance anyway.
I can put 5 hard cycles on my Lipo pack that has 48 cells (24 in series) and the cells rarely go more than 100mv out of balance.
That is 100mV out of balance on 24 cells in series. . .
Cheap cells
early production Zippy R packs...

Lets say that worse case scenario, that 100mV is on 1 particular cell.
All that means is that when I charge to 50.4V on a 12S pack that:

4.20V
4.20V
4.20V
4.20V
4.30V - single high cell, worst possible condition
4.20V
4.20V
4.20V
4.20V
4.20V
4.20V
4.20V
---------
50.4V HVC (actually all the 4.20's would be more like 4.19's but whatever)

Ok, so what?
It is not like a lipo is going to explode if you take it to 4.30V

Anyone wants to challenge me on can put your money where your mouth is.
Paypal me $20 and I will put a 2.2Ah pack in my mouth and charge it to over 4.30V
Seriously.

I believe in safety through education and experience, not safety though fear and superstition.

Lipo packs blow when you take them up over 4.3V AND CONTINUE TO FORCE CURRENT INTO THEM

It is not nitroglycerin. . .


Sorry for that rant.
It has been stewing for a few days since I am now monitoring my lipo pack at the cell level and realizing that I have been regularly charging to 4.3V and discharging to 2.7V and I am not dead yet.


-methods

 

[methods]

I wish there was a 48 volt charger for li-poly batteries.

Batteryspace has a 14 cell (51.8V) LiPo charger but your pack would need to have its own BMS.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4715


-R

I dont want to sound like a Jerk, but this is what I am talking about.
(sorry to pick on your post Russell)
The "industry" has you guys convinced that you are not smart enough to charge your own batteries

There is nothing "smart" about that charger.
It is nothing more than a standard power supply in there.
All power supplies have built in short protection and the other features they offer.
You can have that for 1/2 the price on ebay if you just buy a 150W power supply.
Better yet, if you get one on ebay you can use it for a wider range of voltages.

-methods

 

[pwbset]

You can have that for 1/2 the price on ebay if you just buy a 150W power supply.

:lol: I was going to get that exact batteryspace.com charger for my 14s konion pack... personally I'd rather have a 20s pack as it's going to be powering a Clyte 504 and I'm pretty sure that motor is going to be embarrassed when I hook up 52v to it, but would like me if I hooked up 74v. :wink: Methods kind sir... could you provide a cheap example of an ebay power supply that would do 20s to 4.1v or 4.2v/cell at a reason charge rate and without being too difficult for a charging noob like myself to setup? Thanks!

 

[Russell]

I dont want to sound like a Jerk, but this is what I am talking about.
(sorry to pick on your post Russell)
The "industry" has you guys convinced that you are not smart enough to charge your own batteries

There is nothing "smart" about that charger.
It is nothing more than a standard power supply in there.
All power supplies have built in short protection and the other features they offer.
You can have that for 1/2 the price on ebay if you just buy a 150W power supply.
Better yet, if you get one on ebay you can use it for a wider range of voltages.

-methods

The only problem I see with using a power supply rather than a purpose built battery charger is that the power supply is not "set and forget" if you want to follow the recommended charging profiles. Take SLA's for example; my 36V charger puts out up to 44.5V and then when it senses the current drop to some level it reduces the voltage to 41.4V and holds there. If I used a power supply to charge my pack I'd have to set the voltage to 44.5V then monitor the current so I could disconnect it when the battery was charged or I could simply set the supply for 41.4V and maybe not get as good of a charge...I don't know. I need to read up on why the higher voltage is initially used and if similar profiles are followed for LiPo and LiFePO4 unless someone here can tell me why it's so.

-R

 

[methods]

Sure...

You can hook any combination of power supplies in series to add up to the correct voltage.

20 * 4.2V = 84V

Ok...

Most power supplies can go +/- 10%

48V supply +/- 5V = 43V to 43V
36V supply +/- 4V = 32V to 40V

Take a 48V supply and put it in series with a 36V supply and you have a 84V supply.
Right on the money.

There is a glut of 350W supplies on ebay right now
I am at work so I dont want to get links, but go ahead and get them and post them
We can hash through them

The lower "max current" of the two supplies will be your CC
You want this to be about the same as your pack or less
If you have a 10Ah pack you would want to charge at about 10A
A 20Ah pack would want to charge at about 20A
This will get you about 1 hour charge time.

All you have to do is this:

Buy the 36V supply
Buy the 48V supply
Wire the out put in series

To balance you can build a "24 channel BMS" and just populate the first 20 channels

how does that sound?

Go find the 350W power supplies on ebay (but dont buy! lets talk first) then read up on the 24channel BMS

-methods

 

[methods]

I dont want to sound like a Jerk, but this is what I am talking about.
(sorry to pick on your post Russell)
The "industry" has you guys convinced that you are not smart enough to charge your own batteries

There is nothing "smart" about that charger.
It is nothing more than a standard power supply in there.
All power supplies have built in short protection and the other features they offer.
You can have that for 1/2 the price on ebay if you just buy a 150W power supply.
Better yet, if you get one on ebay you can use it for a wider range of voltages.

-methods

The only problem I see with using a power supply rather than a purpose built battery charger is that the power supply is not "set and forget" if you want to follow the recommended charging profiles. Take SLA's for example; my 36V charger puts out up to 44.5V and then when it senses the current drop to some level it reduces the voltage to 41.4V and holds there. If I used a power supply to charge my pack I'd have to set the voltage to 44.5V then monitor the current so I could disconnect it when the battery was charged or I could simply set the supply for 41.4V and maybe not get as good of a charge...I don't know. I need to read up on why the higher voltage is initially used and if similar profiles are followed for LiPo and LiFePO4 unless someone here can tell me why it's so.

-R

I cant speak to lead acid as I know nothing about it.
Lipo does not need any sort of "charge profile"
Every charger on the market just charges them at a constant current then constant voltage.
As far as I know, the same goes for Lead Acid. Maybe they stage them for heat, I dont know.

Power Supplies are set and forget for Lipo
So long as you have a small leakage current on the supply.
When my supply reaches HVC the leakage current goes down to 300uA which I am sure is lower than the leakage of the pack itself.

-methods

 

[Russell]

I cant speak to lead acid as I know nothing about it.
Lipo does not need any sort of "charge profile"
Every charger on the market just charges them at a constant current then constant voltage.
As far as I know, the same goes for Lead Acid. Maybe they stage them for heat, I dont know.

Power Supplies are set and forget for Lipo
So long as you have a small leakage current on the supply.
When my supply reaches HVC the leakage current goes down to 300uA which I am sure is lower than the leakage of the pack itself.

-methods

I think with lead-acid the charge voltage is increased just to speed things up. You're right about Lithium though and Batteryspace even sells an adjustable power supply to charge them.

http://www.batteryspace.com/index.asp?PageAction=VIEWPROD&ProdID=4815

This one on eBay also looks pretty nice;

http://cgi.ebay.com/MASTECH-VARIABL...286.c0.m14&_trkparms=66:2|65:15|39:1|240:1318

-R

 

[morph999]

Here is a 48v lead acid charger that I just bought.

http://www.batteryspec.com/cgi-bin/cart.cgi?action=link&product=123&sub2=1230086

Batteryspec sent out my confirmation e-mail and tracking number the same day that I bought it. I haven't received it yet but they got really fast service. I like them. I should be getting it in about 4 days since I selected the slowest delivery button.

 

[recumbent]

Lipoly got a bad rap because a few jokers deliberately short circuit some laptop batteries and filmed it when a company had a recall couple years ago. But the RC guys abuse lipoly batteries constantly with no problems.

Thanks "Methods" for clearing up the issues about wiring and charging.

http://www.itselectric.ca and http://www.hi-powercycles.com sell 54volt and 56 volt lipoly packs for about $700-$800 for 10amp/hr packs. Expensive, but very light, compact and powerfull (C- rates) and that counts for a lot to people like me who want discretion.

 

[methods]

http://www.itselectric.ca and http://www.hi-powercycles.com sell 54volt and 56 volt lipoly packs for about $700-$800 for 10amp/hr packs. Expensive, but very light, compact and powerfull (C- rates) and that counts for a lot to people like me who want discretion.

That's a 15S pack
That would work out to 6 Hobby city 5S 5000mah packs which you could have for under $350

5000mah 5S
3S2P gets you 15S 10Ah 55V pack
10Ah * 15C gets you 150A rated output
You could dump 200A burst no problem

On sale now: $57 each
http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6499&Product_Name=ZIPPY_Flightmax_5000mAh_5S1P_15C

Comes wired with balance taps
I swear by these hobby city Zippy packs.
I have over 300 cycles and 1200miles on my pack
If you know me, thats hard miles with 120A bursts and 80A cont.

Hard to beat that :wink:
Everybody likes to get twice as much for half the price.

-methods

 

[GGoodrum]

You say want you will, but the fact remains that LiCo-based cells are inherently volatile, and you you need to take precautions with them, especially as they age. Patrick is right that you don't need a LiPo-specific charger, and that a fixed current-limeted supply will work just fine, but you need to make sure the cells stay reasonably balanced.

They way I've seen some here mount these packs is what worries me. Velcroing them to the bike , with no protection, is just asking for trouble, in my opinion. One crash that either rips out the balance wires or the main leads in a way that shorts cells, and they can start burning. If you've never seen a LiPo pack burn, it is pretty spectacular. I have yet to figure out how to put out a LiPo fire until all the cells have cooked. The heat is intense.

You also need to keep an eye on LiPo packs, to make sure non of the cells "puff", which they can do if air or moisture somehow gets into the cell, or if the cell is stressed too much. Packs with puffed cells need to be disposed of, and not used further. This is what usually happens when the packs are close to the end of their life.

The reason there have been fewer problems in the RC world with these is that people have learned, the hard way in many cases, to take proper precautions when dealing with LiPos. I'm just encouraging those here who use them, to do the same, that's all.

-- Gary

 

[methods]

I agree.
They must be respected.
Always good to teach people to respect the dangers involved.

My beef is with the fear mongering.

Truth be told, I get a lot of PM's and emails from people looking for help setting up Lipo systems.
I try to talk 9 out of 10 of them into getting something that is less dangerous.
I think there are people who inherently understand and know how to mitigate risk
Then there are people who just dont get it or dont have the background to properly assess the situation.

As far as mounting concerns, that is a valid argument.
Personally, I just velcro my packs to the bike because I am reckless
If I crash and they blow up that would make for a good story.
I would certainly agree that if someone wants to be safe they should consider proper mounting techniques.

-methods

 

[pwbset]

Thanks Mr. Methods.. I'll search ebay and post some links when I get a sec. I'm not so worried about balancing the cells I'll be using are the konions and I'll have about 80 extras so if one duds I'll just replace it. 48v+36v sounds perfect for my needs! 74v15ah nominal should please that old 504's desire for power.

 

[methods]

Thanks Mr. Methods.. I'll search ebay and post some links when I get a sec. I'm not so worried about balancing the cells I'll be using are the konions and I'll have about 80 extras so if one duds I'll just replace it. 48v+36v sounds perfect for my needs! 74v15ah nominal should please that old 504's desire for power.

What a second now. . ..

What chemistry are those? :?

(big sigh, slaps head)

-methods

Edit: Ok, I read that they are fire/explosion proof?

Why dont you want to balance them?