how do you protect li-ion batteries for a pack?

[Klem]

batteryjunction.com sells PCBs to international customers. Their range is not as great as batteryspace but their international postage is far more reasonable (Batteryspace int postage charges make my eyes water).

Junction.com sells a 4 cell PCB with 5.7A upper limit.

 

[jspeybro]

Interesting.

When I post a link to Dealextreme it gets deleted - even though I can't find anything in the Forum rules against doing it !

didn't notice this so must be something recent. maybe http://tinyurl.com/ can be a workaround.

 

[josepoyanuk]

bro,

I think I know what you mean...No, you only need one protection circuit for the pack, which will be made up of any number of batteries connected in parallel and then in series to make the voltage you want.

You do need to source the correct PCB for the number of cells you want to build.

Probably easier to have a look at these pictures. This is a 10Ah 11.1V (3 cell) pack made up of 12*18650 batteries. Each cell is a row of 4 batteries connected in parallel, and then these rows or 'cells' are connected in series with the other rows to make up the 3 cells.

Compare the circuit diagram with the numbered leads in the photo. You will see how the four leads come up to the PCB.

This PCB can be used for either a 3 cell or 4 cell pack. In a 3-cell the contact marked 'B3' is ignored.

The JST plug is for balance charging and has its 4 leads connected to the batteries using the solder pads of the PCB. If you want to balance charge then check the charger as it will have the polarity marked on the plug port. You then plug in the JST to see what plug lead needs to go to what cell join.

Some examples of 3-cell PCBs above. The one on the left is 3 Amp limited while the two on the right are 5Amp.

Hi,

Can I ask you a couple of things I dont have clear about Li-ion pack?
I dont understand why I need a PCB. All Li-ion batteries out there have a build in micro PCB. Do I really need to install the big PCB in the picture? If I dont, then can I still use safetly a universal charger with this 11.1 pack?

I noticed that this PCB board always needs a universal charger with the current limited. Am I right?
Then I read that there are other PCB/PCM that can balance the batteries and look the same as these PCB (so it uses a universal current limited charger). But it seems to me that this PCM is exactly the same as the board inside the simple version of any charger with balance function: a box with 12Vin and JST plug. However this charger box does not use a universal charger, it uses a wall plug. And I think they can be connected to a car battery directly too (?)

If I put a PCM do you think I can connect it directly to a car battery?
Do you think I can connect a charger box with balance, like the cheap Tenergy for 20bugs, directly to the car battery instead of the wall charger?

thank you,
jose


(my idea is to do a very versatil battery pack for my radio transceiver, with a wall charger, but also with a 12V direct input. The problem is, for this second part, that I never saw a car cigarette adapter DC to DC with current limitation output. I think the box takes about 1.5A )

 

[Klem]

No, you don't need a protection circuit (PCB) if you can monitor the battery and control the power going in and out in some other way. Lithiums are fragile in the sense that they will be permanently damaged if you exceed their specifications. For example if you let any cell deplete below 2.5V, or if you charge a cell beyond its capacity (4.15V). An unbalanced and unprotected pack being charged by a universal charger is a recipe for damage as the charger monitors the overall voltage only, not individual cells.

If you have a pack with a JST plug with leads connected to each cell and use a smart charger then you can monitor individual cells when charging and use the balance function to maintain peak performance. In this case and using a torch driver that controls the current draw and monitors the voltage with a cut out function (like Taskled's drivers), or if you simply use the pack in one torch only and monitor the time/use carefully then you can get away without using a PCB.

Not all Li-ion batteries have a PCB inside them and it is often impossible to tell in a website photograph beyond testing them or reading the specs or reviews (if it's not clear in the specs). If you join cells together to make a pack you don't want batteries that are already individually protected and that is why some cells are for sale without them. A pack with individually protected cells will interfere with the packs main PCB. You only want/need one PCB that monitors the cells individually and determines power in and out at the combined voltage.

Here are a couple of examples where I don't use a PCB;

A 5-cell 42W torch, because I could not find a PCB small enough to go into the battery compartment. In this case I trust the driver to monitor the battery when in use and is programmed to cut off at 15V (5*3V). When charging I use a smart-charger on balance mode. The battery has a JST plug connecting all cells individually for balancing. The battery is used for no other purpose.

A 4-cell 75W HID, because I could not find a PCB that allowed a 9A+ current draw in the time I was building it. I use it for single night dives of under 60minutes only. If left on for too long the battery will be permanently damaged and by that I mean the HID will go out and won't be able to be recharged. The battery has a white JST plug connecting all cells individually for balance charging, and a red Deans plug for quick charging and is also used as the switch to power the toggle circuit. The battery is used for no other purpose.

Yes, I know, it needs a coat of paint!

So yes, you don't need a PCB if you are mindful of what is going on, know when to turn it off and have some way of individually charging each cell.

Newer model PCB's/PCM's include balancing functions. The PCB's in my earlier post photo's do not.

You can connect your chargers to whatever power source within the range of voltages and current draw your charger requires. Some will accept 12V DC (car batteries).

Picture of a smart charger with a 5-cell battery used in the top torch. Note the two plugs; a yellow XT60 plug for normal charging and power draw (2 terminals + and -), and the white JST plug with a lead connected to each cell, so the charger can monitor and balance. Unprotected batteries in a pack with no PCB/PCM.

 

[josepoyanuk]

Thank you. This has been very helpful.
About the chargers, what does it mean 12V 1.5A for me? does it mean that it Takes 1.5A from the power supply or that I can not Give it more than 1.5A?. I ask you this because all the chargers I saw for sale only state voltage and current draw, but nothing else. I got a reply from a seller for a cheap charger with balance and he told me that I can not connect it directly to a battery. But a very similar charger is for sale in other page with crocodile plugs! (I know the charger in your last photo can be connected directly to a car battery, but it will be to big to put it in my pack)

do you know of a charger that would allow a torch (or a transceiver) to run and get the li-ion pack charged at the same time, the same as lead acid emergency lights ?

thanks for your help,
jose

 

[pinkpanda3310]

Thank you. This has been very helpful.
About the chargers, what does it mean 12V 1.5A for me?

Power (watts) = Volts (V) * amps (A)

Lots of hobby chargers are 50w max. So the power needed for that charger would be 50w / 12v = 4.16A A 12v 5A supply would allow the charger to run at maximum capacity. The power output is not always the maximum capacity as it depends on the cells. The cells have a 'c' rating for discharge as well as charge the link below explains better. http://www.fortbendrc.com/tips/LithiumBatterySecrets.pdf

do you know of a charger that would allow a torch (or a transceiver) to run and get the li-ion pack charged at the same time, the same as lead acid emergency lights ?

I would suggest making more packs so you don't need to do this but maybe some of these other guy's know how to do what you want.

 

[josepoyanuk]

Hi, thanks for the reply.
I read the article and it was useful.
Then, to be completely sure my charger will not burn, I need to find something that connects to the cigarette car plug and limits current to 4 amp. the only thing I found are step down converters, from 24v to 12v and limit to 1.5 or 3 Amp, but I'll keep searching.

I'll try to make my pack as versatile as possible because one alone will be already quite expensive for me. a pack that can run and charge at the same time will actually replace the power supply; it will be amazing.

thanks you
jose

 

[pinkpanda3310]

You don't need to limit the current going into a charger, you want to make sure you have enough current (above the required current). So running off your car battery direct is no problem provided the engine is turned off. If you want to run the engine while charging that's a different issue. Auto systems can have large voltage spikes which could do damage to the charger.

I'm still not a hundred percent sure of the implications of charging and running similtaneously will do. I'm also a little confused on the "replace the power supply" comment.

 

[josepoyanuk]

ok,
the comment was because i want to use this particular battery pack in a portable backpack two way radio (I am also a flashlight fan). these radios usually run from a desktop power supply, not portable and very heavy. but if it can run from a battery that is charging (and drain power from the battery instead of the wall plug) then I potentially can use it all the time without the dedicated power supply. that is to say: i can take it anywhere I want on my back

the analogy is when you turn on a the lead-acid warehouse emergency light still plugged to the wall. yes I know: they dont run all the time. but transceivers dont transmit all the time.

my perfect pack would be the one Klem did, with 4 cells in paralel for 12 Amp, with a balance charger attached to it and a power supply too. so I only need to carry a cigarrete plug cable and/or an AC cable.

 

[Klem]

You've lost me on the scenario you are thinking of. Can you draw us a quick sketch?

The 4-cell power supply in the above photo is 16 unprotected 2400mAh 18650 batteries in a sealed hobby project box. The battery configuration is 4S4P, so it is 16.5V when fully charged, and being unprotected you don't want to deplete it to lower than 10V. If it had a PCB it would cut-out at about 12V.

One neat way of monitoring the voltage is this little device made for RC hobbies. It scrolls continously through showing each cells voltage then gives you a total. Any pack configuration from 2-6cells. DX sells it for about $3;

 

[pinkpanda3310]

Jose. I think I understand what your getting at. Your power supply to the radio currently must be worth $ or are you trying to save space? A hobby charger (like the one pictured above) is likely to be roughly as big than a 4s4p pack. The one pictured above also needs a separate 12v power supply which can be just as big. I'm guessing you'll be going for something like this - http://www.hobbyking.com/hobbyking/...2_6S_Battery_Balance_Charger_AC_DC_w_PSU.html

It doesn't need a separate power supply. It can run on 11-18v DC or 100-240v AC. Just change the input cable like you said.

 

[pinkpanda3310]

Sorry. Double post :sick2:

 

[josepoyanuk]

Hi,
I refered to one of the first pictures in the thread, the one that is 11.1V. I like this volt meter. I did not know it scrolls all cells. I wanted to put a micro volt meter, but this is better. I wonder if it does not interfere if I solder in parallel with the balance charger. Here is the sketch :

 

[josepoyanuk]

Jose. I think I understand what your getting at. Your power supply to the radio currently must be worth $ or are you trying to save space? A hobby charger (like the one pictured above) is likely to be roughly as big than a 4s4p pack. The one pictured above also needs a separate 12v power supply which can be just as big. I'm guessing you'll be going for something like this - http://www.hobbyking.com/hobbyking/...2_6S_Battery_Balance_Charger_AC_DC_w_PSU.html

It doesn't need a separate power supply. It can run on 11-18v DC or 100-240v AC. Just change the input cable like you said.

Wow! yes, definitely this is what I was looking for ! I could not find this on ebay: two incomes 220 and 12. I think I'll go for this.

A power supply is not expensive but it is bigger that the radio alone and weight about 5 Kg. You can not carry it with you. I want to make a portable Backpack radio just for fun of operating something that is very light and at the same time giver a full RF output, something totally autonomus.
Thanks a lot for the link.

 

[josepoyanuk]

can you solder directly to the battery tips? will that not burn the plastic film inside?

 

[Klem]

josepoyanuk,

Yes you can solder directly to the battery tips...there's a photo of this in this thread.

OK, I was confused trying to understand why anyone would want to charge their battery while it was being used underwater (dive lighting section).

 

[pinkpanda3310]

OK, I was confused trying to understand why anyone would want to charge their battery while it was being used underwater (dive lighting section).

Yeh, the sub forum, thread title and outcome are not quite aligned.

Speaking of which, Jose, the charger I linked does not automatically start charging when a power supply is plugged in. It needs programing the first time you use it and then push the start button, each subsequent time you power up the charger you will need to push the start button. I just wanted to make that clear

 

[josepoyanuk]

- Yes, sorry about the outcome. But everything is related somehow. Once I imagened a rechargable spotlight that can be run from the car at the same time it is charged. It would be great for hunters. So they can use it permanently and at any time unplug it and move away from the car/truck still with a full charge. No need to turn it off for charging, maximun flexibility. It works the same as my radio battery. (I'm probably a bit absessed with portablily)


-I noticed that I need to set the charger before using it. Ummmm... I thought again may be the cheap balance charger with this: a car filter (I found it if filter the car noise and it limits current too). so the same configuration as in my original sketch but with a car filter to be totally sure I wont ruin the charger.


-I wonder what happens if I turn on any device when the balance charger is making it's job. I see two cases: the device takes more current than the charger or it takes less. probably I try to see how it behaves and it is safe.

 

[pinkpanda3310]

I notice in your little sketch the charge rate is only 1.5A, and the consumption of the radio is 1A (receiving only). That doesn't leave much to charge the battery. If it were charging from flat it would take an aweful long time to reach full capacity. Not only that but the same charger is listed elsewhere with a charge rate of 0.8A - http://www.hobbyking.com/hobbyking/store/__7637__Turnigy_balancer_Charger_2S_3S.html

You might be better off running a parallel harness from the 12v supply to both the charger and the radio with a toggle switch at the radio to switch between battery or 12V power. That way the battery can charge at the full rate.

 

[josepoyanuk]

I notice in your little sketch the charge rate is only 1.5A, and the consumption of the radio is 1A (receiving only). That doesn't leave much to charge the battery. If it were charging from flat it would take an aweful long time to reach full capacity. Not only that but the same charger is listed elsewhere with a charge rate of 0.8A - http://www.hobbyking.com/hobbyking/store/__7637__Turnigy_balancer_Charger_2S_3S.html

You might be better off running a parallel harness from the 12v supply to both the charger and the radio with a toggle switch at the radio to switch between battery or 12V power. That way the battery can charge at the full rate.

Yes, that is correct. Then, it would not charge when receiving. The thing is that in fact, I forgot to mention it, these transceivers are in stand-by most of the time. So in fact, as an average, they transmit 10% of time 8A, they receive 10% of time 1A, and the rest of the time they are just waiting for a signal at less than 1A drain. This is average taken by manufacturers to calculate battery life. Of course, with Klem's battery I can drain the pack in one hour if I transmit all the time, but in practice that will not happen.

The thing is, when passing from transmiting to receiving-standby what will happen? will than confuss the charger, will it burn it, or will it make to give more current, so the battery will finally burn....me? I found in your website the Hobbyking DC-4S Balance Charger. This has incorporated the display that Kem mentioned so it is great. But it has also output for 4S. Imagen the charger get confussed when I transmit and it overcharges the pack.
I dont know nothing about electronics and I couldnt find on google someone that had tried this before.

These radios can only use conventional power supplies that weight about 3Kg. I dont know why is this but I never saw a switching light weight 13.8V for a radio transceiver. Moreover the power supply is as big as the radio, so carrying it with me is not an option.