LiPo battery packs

[Just]

Alan, you wrote: "Two chargers is one option for faster charging"

Do you connect the chargers in parallel? Do you put diodes between them?

[o00scorpion00o]

o00scorpion00o wrote: "With lipo you can buy more batteries as you get more money and add to the pack for higher voltage or capacity or both, with a ready made LiFeP04 you cant!"
Really? Can you explain why? Or just go over the Ping's site and he will explain how to connect its LFP4 battery packs (with BMS) is serial as well as in parallel.
Any comments?

Okay let me rephrase!

You can parallel 2 ping batteries sure, however it will cost you more to do it that way initally, where as with LiPo or indeed even hobby king's LiFeP04 batteries you can buy the smaller 5 ah batteries and keep adding until you have the capacity that meets your demands!

But most of all you will be getting 30C instead of 1C rated batteries, which is much better if you want to use a smaller 10 ah pack but you pull or want to pull more than 10 amps from the battery!

I hope that makes sense?


Mark

[o00scorpion00o]

Alan, where can I buy this basic battery monitor, which you mentioned in  your post above? What's its voltage range? Is it programmable?

you wrote: "very loud warning device which can be handy if you forget to disconnect the pack" - don't you disconnect it at all from the battery? What's its power consumption (my guess it's just a leakage...)?

All the info for the cell log

http://epbuddy.com/index.php?main_page=product_info&cPath=30_8&products_id=27

You leave it connected to the battery while riding your bike and disconnect when not using it!

[o00scorpion00o]

Bikemad, you wrote: "but not really enough for high regen currents"

So, how high are the regen currents usually? Do they depend just on the motor or both the controller and motor? Please tell more... 

You can set the regen on some controllers, but you can get 20 amps or more regen current depending on your speed and the hill you are going down! That's why your batteries need to be able to take it!


And for connecting, for instance 2 Ichargers, you can use 2 separate power supplies to power 2 chargers or 1 power supply provided it's rated for 2 chargers!

And you simply parallel your packs, if you have 2 packs and 2 chargers that's fine, if you have 4 packs and 2 chargers you gust parallel 2 packs balance and power leads to 1 charger and the other 2 packs to the 2nd charger!

But really buying 1 decent charger is more than enough, and just parallel all your packs to the 1 charger!

[Just]

"you gust parallel 2 packs balance and power leads to 1 charger" - how can you do so? the balance lines as well as power leads in separate packs have different voltages (at least 0.1V will have)! As for me, I use a special board to connect them in parallel while charging...

[o00scorpion00o]

"you gust parallel 2 packs balance and power leads to 1 charger" - how can you do so? the balance lines as well as power leads in separate packs have different voltages (at least 0.1V will have)! As for me, I use a special board to connect them in parallel while charging...

You only parallel charge (afaik) I'm still learning about LiPo also, if the cells are not very out of balance. Parallel charging will still sense if a cell is over charged and adjust accordingly.

You can parallel charge as many packs as you want!

Mostly though if you keep within the specs of LiPo you should not need to balance charge very often, though I would still connect all the balance leads, just in cast 1 cell decides to go over!

I think 0.1 volts is acceptable between some cells, probably even a little more, though I stand to be corrected on that!

[Just]

if so, you can just make the cells in different packs be in parallel by connection its balance wires... But way do you disconnect them while discharge? Why not to leave them connected forever?

[Just]

As for the CellLog, it's voltage range is up to 44VDC, but I need up to 52VDC at least

[o00scorpion00o]

if so, you can just make the cells in different packs be in parallel by connection its balance wires... But way do you disconnect them while discharge? Why not to leave them connected forever?

Afaik, voltage still travels through the balance wires and one battery may try charge another that way and it might not be good!

And you will need the balance wires connected to the cell monitor!

You need a cell monitor for 52 volts? Right, the cell monitor will monitor up to 8 cells for up to 44 volts each pack, for instance you want 52 volts? well the closest in LiPo is 12S for 49 volts charged!

So you connect 2 x 6S packs to give you 44 volts nominal or 49 volts charged!

In other words 2x 6S 8ah packs in series for 44 volts and another 2 in series then wired for parallel to give 16ah

That's 4 batteries that's 4 cell monitors? make sense?

I suggest you check out the endless sphere forum, there is endless information there on LiPo, oir any battery from much more experienced people than I.

But I hope I am of some help!


Mark


Mark

[Bikemad]

It's a 15V 23 amp charger Alan?

That was the charger recommended in their specs?

And I thought it would charge all 8 cells @20 amps?

Though I'm only using 6S and I'll be parallel charging

Mark, I presume it's the power supply that's 15V 23Amp (345Watt).

The icharger 208B pictured in your earlier post has the following printed on the case:
Charge: 0.05-20A(350W max)

Basically, the maximum current is limited to 20Amps, but as the maximum charger output is 350Watts, the current will be reduced if the pack voltage exceeds 17.5V

If a five cell pack has been discharged to 3.5V per cell, the pack voltage will be 17.5V.
So your charger would begin charging at ~20Amps and be producing the maximum Wattage (17.5V x 20Amp = 350Watts).
As the pack voltage increases during the charge, the current will automatically reduce to stay within the 350W max output.
At 4.0V per cell the current will have fallen to 17.5A, and at 4.2V per cell it would be down to 16.7Amps.

If a six cell pack has been discharged to 3.5V per cell, the pack voltage will be 21V, so it would commence charging at ~16.7Amps.
At 4.0V per cell the current will have fallen to 14.58A, and at 4.2V per cell it would be down to 13.88Amps.

When the charger reaches the maximum preset pack voltage, the current will slowly start to decrease as less current is required to keep the pack voltage at its maximum. This gradual wind down takes almost 20 minutes on my 7 cell 10Ah pack (see attached graph) and noticeably extends the charging time.

The attached graph shows a maximum current of 5.2Amps (my charger has a 150Watt limit) and 1.2Ah being put back into a partially used 10Ah pack. If the charger was able to put all of the 1.2Ah back in at a continuous rate of 5.2Amps it would only take 13 minutes 50 seconds, but this gradual current wind down extends the charge time to almost 25 minutes (and a balance charge extends it considerably more).

Hopefully you will be able to understand why a 350 Watt output cannot charge an 8 cell pack at 20 Amps.
In order to produce 33.6 Volts (8 x 4.2V) @ 20 Amps you would require 672 Watts, but your charger will only supply 10.42 Amps (33.6V x 10.42A = 350W).

Alan
  

[o00scorpion00o]

I think what you are saying is that I should have got a 24 V power supply then?


The Charger itself has a 4-32 volt input range!

I think I understand, so I set my charger to charge each cell to 4.1 V to per long battery life. 4.1 x 6S =24.6 volts.

So the charger has a max of 350 watts charge, meaning 24V divide by 350 = 14.22 amps! Yeah I think I got that. I never thought about that!

Now I will set the balance to fast so that should speed things up a bit + by charging to 4.1 should help keep the cells in balance anyway. There is an option on the Icharger to stop charging when the total voltage reaches whatever you want so that would be 24.6 volts and not balance charge at all, provided the cells are closely matched to begin with.

To be honest I would probably leave the balance wires connected all the time on fast balance, as it will still probably charge plenty fast for me anyway!

Some guys don't balance at all if they are pretty closely balanced to begin with!

I can always find a meanwell charger on E-Bay when I get the cash together again. I intent to bulk charge so as not to have to break my pack down to parallel charge. So I would need a 48 V meanwell adjusted to 49.2 Volts and maybe 1500 watts, that's 30 amps charge! 

For now though I would still be happy with 14 amps charge!

[MonkeyMagic]

o00scorpion00o wrote: "With lipo you can buy more batteries as you get more money and add to the pack for higher voltage or capacity or both, with a ready made LiFeP04 you cant!"
Really? Can you explain why? Or just go over the Ping's site and he will explain how to connect its LFP4 battery packs (with BMS) is serial as well as in parallel.
Any comments?

Alan, where can I buy this basic battery monitor, which you mentioned in  your post above? What's its voltage range? Is it programmable?

you wrote: "very loud warning device which can be handy if you forget to disconnect the pack" - don't you disconnect it at all from the battery? What's its power consumption (my guess it's just a leakage...)?

Bikemad, you wrote: "but not really enough for high regen currents"

So, how high are the regen currents usually? Do they depend just on the motor or both the controller and motor? Please tell more... 

Alan, you wrote: "Two chargers is one option for faster charging"

Do you connect the chargers in parallel? Do you put diodes between them?

"you gust parallel 2 packs balance and power leads to 1 charger" - how can you do so? the balance lines as well as power leads in separate packs have different voltages (at least 0.1V will have)! As for me, I use a special board to connect them in parallel while charging...

if so, you can just make the cells in different packs be in parallel by connection its balance wires... But way do you disconnect them while discharge? Why not to leave them connected forever?

Dmitryl I think it's fair you start paying poor Alan $2 for his responses Have you bought a Magic Pie yet!!???

DID SOMEONE MENTION LIPOOOOOO!!!!!!!!!!!!!!!!!!@!@!@!!@?

lol

[o00scorpion00o]

HAHAH

I might have mentioned LiPO once or twice!


LiPo! 

[Bikemad]

Alan, where can I buy this basic battery monitor, which you mentioned in  your post above? What's its voltage range? Is it programmable?
you wrote: "very loud warning device which can be handy if you forget to disconnect the pack" - don't you disconnect it at all from the battery? What's its power consumption (my guess it's just a leakage...)?

Dmitryl, you can purchase these from HobbyKing, but they are not adjustable and are meant for LiPo packs (not LiFePO4).
They are available for 1-6s packs.

I use a 6s version to monitor my 7s pack by simply connecting it across 6 cells using the balance lead. As my cells are always closely matched, it is good enough for me.

I always connect my battery monitor/warning device to my pack before I connect the pack to the bike, and I usually remove the pack with my Turnigy watt meter and the battery monitor still connected, and it stays like this until I have chance to enter the details from the watt meter into my spreadsheet.
As I don't always do this straight away, it's reassuring to know that the battery monitor will alert me before the pack discharges low enough to cause permanent damage, just in case I'm distracted and completely forget what I was doing.
Once everything has been disconnected from the packs power leads, I finally unplug the monitor from the balance lead.

Its current consumption is ~17mA.

Alan
 

[o00scorpion00o]

Alan,

you can adjust cell monitors voltage alarm range can't you?

And they can monitor up to 8S.


Mark