LiPo battery care and basic information

[nitecheck]

Thanks Gary.
I will start with my orginal plan of 3xunits & see how it goes on the current controller.
Then add another unit but use my "beefer" controller to test .... I have a few extra controllers (for other Ebike & scooter motors) besides my designated spare - so I might have to experiement a bit to get the right combination. This should be fun After I've played with options I'll post some results just in case others may be interested..
Cheers

 

[MitchJi]

Hi,

http://www.fmadirect.com/new_applications/charger_info.html

Scroll down to almost the bottom of the page:

Cold Weather Mode > Did you realize that charging lithium batteries in cold weather (below 50 deg F [10 C]) can cause permanent damage to the battery? Yes, it is true. In fact, at temperatures approaching freezing, a single charge to 4.2v can actually cause complete loss of battery capacity. The damage is permanent and irreversible. For this reason, the Cellpro 4s charger monitors ambient temperature and reduces the full charge voltage to 4.1v per cell below 50 deg F (10 C), preventing damage to the batteries.

 

[ZapPat]

Hi,

http://www.fmadirect.com/new_applications/charger_info.html

Scroll down to almost the bottom of the page:

Cold Weather Mode > Did you realize that charging lithium batteries in cold weather (below 50 deg F [10 C]) can cause permanent damage to the battery? Yes, it is true. In fact, at temperatures approaching freezing, a single charge to 4.2v can actually cause complete loss of battery capacity. The damage is permanent and irreversible. For this reason, the Cellpro 4s charger monitors ambient temperature and reduces the full charge voltage to 4.1v per cell below 50 deg F (10 C), preventing damage to the batteries.

Have a look at lithium_failures. From what I gather it is important to reduce the charging [and discharging] rate as the temperature drops bellow 10oC, but I couldn't find anything about instant cell destruction happening above 4.2V at cold temperatures. Of course it is always a good idea to only charge to 4.1V anyways since cycle life will be highly augmented, but lowers the available capacity by 10% or so. Even with 10% less capacity, modern LiPos still kick but in energy density compared to similarly priced LiFePO4s, and their cycle life will then probably be at least as good if not better than LiFePO4 too.

 

[MrKang]

*TIP

For people who want to use LiPo and want to buy a lipo charger/balancer which works on a 12..24 V DC Input.
Use a computer ATX Power Supply instead of a expensive 30A 13.8 Lab Power Supply.
Just open the CPU PSU..desolder all wires except the green one.
Connect your negative and positive leads to your Lio charger and connect the green wire to the negative inside the PSU.

Voila! a 20A 12V PSU for only ...25 bucks! I Use 3 of those PSU and 3 LiPo balancers . Works like a charm !!

I have integrated an DC volt reading on top of my batterie case to check my LVC

 

[RoughRider]

another question:

what is the point of having a nice energydensity(e.g. 150Wh/kg), but not using it...??

because you better not charge this cell full ==> 4.1V and discharge it only to 40%...

so, its not much better than LiFePo4...right?

 

[recumpence]

Not really.

Lipo is more than twice the capacity of LifePo4. You cannot (should not) drain LifePo4 down totally either. In fact, the only chemistry that should be is Nicad and NIMH.

Lipo CAN be drained to 20% and recharged to 100%. However, their life increases susbstancially if you stay between 40% and 98%.

Most other chemistries benefit from that type of behaviour as well.

Lastly, even if you are only using half their capacity on a regular basis, the added capacity that is not used gives more power upon accelleration than if you just use a lower capacity battery but used more percentage of its charge each time.

Matt

 

[heathyoung]

The main cost of LiPo seems to be the chargers rather than the batteries themselves.

Presumably it is possible to rework the TPP packs BMS/Charger to charge LiPo - the resistors on the LM431 programmable voltage reference could be changed, and the LVC curcuit could be reworked (with another LM421 voltage reference + divider resistors - as the LVC will be higher than the 2.5V that the LM421 is set to) - I take it that the TC54-2.1V was selected due to its lower voltage sensitivity? When I was messing with LVC's for other batteries I wish I had know about these (rather than using LED forward voltages as low voltage zeners!)

I'm looking at making some packs up using the 'zippy' 6S packs, two in parallel (with the balancing wires in parallel as well) - as long as both packs are at the same SOC, is there a problem with using this approach?

 

[Dave-s]

Nope, no problem at all.
I built a 8s4p pack using 4s1p 4000mAh packs I ordered from eBay.
Just hooked up all 4 balancing taps together.

 

[heathyoung]

I thought that would work, thanks.

I'm still looking at charging circuits, rather than going a shunt based design, I'm thinking of making individual chargers per 3.7V cell, and making a custom switchmode power supply with multiple 5V rails (just all wound on the same toroid) to run it all.

 

[MitchJi]

Hi,

I'm still looking at charging circuits, rather than going a shunt based design, I'm thinking of making individual chargers per 3.7V cell, and making a custom switchmode power supply with multiple 5V rails (just all wound on the same toroid) to run it all.

Check here:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=9522&start=0

Creating single cell chargers

Of particular interest:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=9522&start=0#p146954

I'm looking for DoctorBass's posts about single cell chargers as I know he was advocating them a year ago or so.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=2586&p=35650 - The post of yore, I guess.

http://endless-sphere.com/forums/viewtopic.php?f=14&t=1984&p=26590 - One source; seems to be the slow 2A variety

And:
http://endless-sphere.com/forums/viewtopic.php?f=14&t=9522&start=0#p147464

Here's what I'm doing:
Up until recently, Bill Zelman (Powermed here...) was selling Vicor 48V/3.7V 20A DC-DC convertors for $10 each, and that was shipped, so I bought a bunch (24...). He was also offering a nifty 48V/4.2A supply, so I bought some of them as well. In the box above, I've mounted 16 of the 3.7V supplies on a 2-1/2" x 1/4" x 12" piece of aluminum...

 

[heathyoung]

Interesting - a lot of these chargers seem to be running from a low voltage source - The CC/CV method isn't too bad, and simple to implement, though I'm not sure where to terminate the charge (ie. what current when in CV mode? is it a function of capacity?)

Using multiple isolated DCC converters seems like a good idea.

 

[GGoodrum]

Interesting - a lot of these chargers seem to be running from a low voltage source - The CC/CV method isn't too bad, and simple to implement, though I'm not sure where to terminate the charge (ie. what current when in CV mode? is it a function of capacity?)

Using multiple isolated DCC converters seems like a good idea.

When the current drops to about 20-30mA, the cell is about as full as it will get.

-- Gary

 

[GTA1]

Having used Lipo batteries for RC, the only thing I have to add to this excellent thread is:

Think very hard about safety when you locate your battery:

i.e. if it catches fire, where will it be relative to the rider? Do you want it between your legs as it bursts into flames?

Think real hard about a casing (metal or very hard plastic) that can protect the battery from punctures, which can instantly cause a short and fire.

If you use a casing, be sure it is vented --- so heat can't build up from sunlight or other sources.

Lipo is a very high density power storage system... use with care.

 

[RWP]

I have a 10S2P system of 4 18v 5Ah cells.

Today when I went to charge my cells with an iCharger 1010B I got arcing when connecting the charging wires and also when connecting the balancing wires. :? Almost fried the balancing card!

I charge in the 10S configuration with each of the cells plugged into the balancing cards 5S connectors and the each of the 5S cells in series to make 10S so I plug the Deans connector to the Deans serial connector from the cells to the Deans connector from the charger. The iCharger is set to charge at 10S. But this was occurring before the iCharger was even turned on.

The iCharger was not plugged into the power supply (PS).

Finally I plugged the iCharger into the PS and then when I plugged the batteries into the iCharger all went well.

Is there a sequence when connecting the batteries for charging into the iCharger? Should the Deans connector (main power wires) be connected before or after the balancing wires?

Does in matter if the PS is connected to the iCharger before or after the batteries are connected?

Kinda scary...

Roy

 

[liveforphysics]

You had your balance taps in the wrong slots.

When you have a 10s pack made from 5s packs, it's critical to label which balance leads relate to the full packs leads.

Once you've passed hard current through a balance tap lead, you need to inspect all the pins with an ohm meter to ensure your balance taps still are able to make a good connection. If not, snip it off and solder on a new connector. You want those to be good. That charger will never draw more than 300mA through a balance tap lead if you are connecting things correctly.

The main pack charge leads should make a small spark when first connected to charge the little output filter cap. That should be the only spark involved in the charging process.

1. Connect main pack leads.
2. Connect balance tap leads in the CORRECT slots.
3. Plug-in the charger's power supply.
4. Make sure the charger is on the settings you desire.
5. Start charging.

Best Wishes,
-Luke

 

[RWP]

Thanks Luke,

You had your balance taps in the wrong slots.

It seems impossible for me to put the balance taps into the wrong receptacles as the balance taps are shaped in such a way that it is only possible to connect them one way.

When you have a 10s pack made from 5s packs, it's critical to label which balance leads relate to the full packs leads.

Label what where???

The main pack charge leads should make a small spark when first connected to charge the little output filter cap.

What is the "little output filter cap"?

Roy

 

[MrKang]

Hi RWP,
I use 12S5P combinations with 10 pcs of 6S Lipo packs 4000mAh

I use a 12S balancer. This is how i work when charging.

- I turn on the chargers power suply (12V CPU Powerssupply)
- Then i put two packs in Serie
- I first connect the negative and then the positive lead to the balancer
- then you have two balance connectors left to put in.
- If you look at your balancer you can see the cell numbering count up from 1 to 12 ( in your case 10)
- you connect then the first balance connector (1 -5) with the first Lipo connected from the negative wire.
- then the second one (6-10) with the other Lipo
- The balancer then recognizes you have a 10S pack
- check your balancer if it has the correct values for charging and then hit start to charge!

 

[liveforphysics]

RWP- the plugs are molded so they can't be plugged into the indivdual slots incorrectly, but you certianly can get the plugs mixed up between the left and right slots. This effectively puts a 20v short between the balance pin and the charging connectors of the packs in series. Remember, the end balance taps are the same as the output leads, so if you don't orient them correctly with the plugs that also connect to the charge leads, its the same as shorting the pack.

 

[RWP]

Thank you "MrKang" and "liveforphysics".
Got it now.
Roy

 

[RemoteContact]

Is this an awesome deal or what,

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9174

Cinco de mayo special, 5s 5ah for 50 bucks.

 

[ktm_paul]

Is this an awesome deal or what,

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9174

Cinco de mayo special, 5s 5ah for 50 bucks.

Has anyone bought these or similar? How many cycles are they good for?

Are they suitable for emotorcycle too? I understand charge/discharge concerns...

 

[RemoteContact]

my 6 packs come in tomorrow!

 

[ktm_paul]

Is there any harm in connecting these in parallel (say 6 of them):

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=9174&Product_Name=Turnigy_5000mAh_5S_20C_Lipo_Pack

Then using this to charge and balance them?

http://www.hobbycity.com/hobbycity/store/uh_viewItem.asp?idProduct=6609

Other than it being 'slow'?

I am thinking of 6P4S (really 20S) of these packs. Connecting first parallel then series. Was going to use two of the chargers above...

Am I missing something?

Thanks.

 

[recumpence]

my 6 packs come in tomorrow!

You can always run to the local convenient store to pick up a six-pack if you get really thirsty. No need to order them. :wink:

Matt

KTM, no problem with paralleling them at all. I am setting up a 12S 5P 2.2 KWH pack myself right now.

Matt

 

[ktm_paul]

my 6 packs come in tomorrow!

You can always run to the local convenient store to pick up a six-pack if you get really thirsty. No need to order them. :wink:

Matt

KTM, no problem with paralleling them at all. I am setting up a 12S 5P 2.2 KWH pack myself right now.

Matt

thanks matt. how will you connect them in parallel?

PS isnt that 1.1 kwh though? 12 * 3.7 v * 5 * 5 Ah