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Author Topic: Confused about Lithium Ion  (Read 1440 times)
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Most charging circuits use chips like these to handle the charging.

ww1.microchip.com/downloads/en/DeviceDoc/21984a.pdf

As you can see, they charge either LiPo or Li ion batteries.

Check this PDF for some details about the limits of LI batteries:

www.batteryonestop.com/baotongusa/products/datasheets/li-ion/sanyo-ur18650f-26a.pdf

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but do I need a special circuit in order to cut-off the power once it battery reaches a certain level?

This is usually handled by the charging chip but when you buy batteries from a reputable source, they usually ask if you want a 'PCB' (protection circuit) embedded in the battery. e.g.

http://www.ebay.com.au/itm/ws/eBayISAPI.dll?ViewItem&item=280769021348&refid=store&ssPageName=STORE:HTMLBUILDER:SIMPLEITEM


This is a tiny board bundled in the outer sheath of the battery that you cannot see and does not materially change the length of the battery.
These boards help preventing over discharge, short circuit protection and sometimes overcharge protection.

https://master-instruments.com.au/related_info/PCMs%20for%20Lithium%20Ion/PCMs%20MI%20Offer%20for%20Lithium%20Ion%20and%20Lithium%20Polymer%20batteries.htm

If you want to stick to Li Ion then your will probably end up with the 18650 format cell (in link above) unless you go for a proprietary format/charger such as camera batteries. If so you will need a holder such as these:

http://www.digikey.com/product-detail/en/BK-18650-PC4/BK-18650-PC4-ND/2330513

This will allow you to remove the batteries and charge them individually if you want. (Be sure of both batteries getting full charge).

If you want to charge them in circuit, in series check these out:

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en544320

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...because a single cell (3.7) wouldn't be able to power the Arduino (5V)..

There are several threads about running Arduinos at 3.3 volts (and much lower). You can run them at voltages way lower than a single Li battery discharged to its lowest safe level.
« Last Edit: January 10, 2013, 12:47:26 am by lemming » Logged

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LiPo is useful if you need high current.  If not, NiMH may work better.  But, if you feel you must use LiPo, I would suggest you use LiFePo4 as it's the latest technology and doesn't have the "explode" factor that standard LiPo does.  LiFePo4 are readily available outside the US (as most are made in China and HK).  Anyway, they have a little lower voltage (3.7/3.3 per cell) but that actually works out well for battery powered systems.

As far as charging. It's fairly straight-forward.  I typically do a trickle charge via solar with a voltage limiter with a simple voltage divider.  This works with any type of LiPo battery. If you go with a trickle charge and voltage limit, the main thing to worry about is low voltage.  You need to devise a circuit that will terminate when the voltage is lower than a certain amount.  If not, you'll kill your LiPo battery.

Tim
« Last Edit: January 10, 2013, 10:29:46 am by teckel » Logged

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Thank you very much guys for the responses.

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but do I need a special circuit in order to cut-off the power once it battery reaches a certain level?

This is usually handled by the charging chip but when you buy batteries from a reputable source, they usually ask if you want a 'PCB' (protection circuit) embedded in the battery.
Is it safe to assume the camera batteries I linked to have this protection circuit embedded? Or should I distrust anyway and use what kind of circuit?
The component you linked to, you say is for charging, and maybe I haven't made myself clear, I don't need help charging, I'll use the original charger for the camera batteries. I'm also not attempting to.. how do you call that, trickle charge? (Use while charging at the same time).
I just need to be sure the battery won't explode while using it, that's all.

This is a tiny board bundled in the outer sheath of the battery that you cannot see and does not materially change the length of the battery.
These boards help preventing over discharge, short circuit protection and sometimes overcharge protection.

https://master-instruments.com.au/related_info/PCMs%20for%20Lithium%20Ion/PCMs%20MI%20Offer%20for%20Lithium%20Ion%20and%20Lithium%20Polymer%20batteries.htm
That seems like what I would be needing, but I got confused with your comment "bundled in the outer sheath of the battery". In the end, are these circuits I'd use between the Arduino and the Li-Ion battery? Or are they just saying those red 18650 Sanyo batteries have them already on? Or is it, that they sell them packed with the circuit or...?

Also, they say
Quote
When the voltage and/or current return to acceptable levels, the safety circuit automatically resets allowing normal operation of battery assembly.
Does it mean the Arduino would stop functioning just as if I had removed the battery or is it left in standby mode or...? It is not very clear, I guess I'd want the cut off circuit to just shut down it all (probably I know I'd have to read something from the Arduino pins then stop the arduino via software???)


If you want to stick to Li Ion then your will probably end up with the 18650 format cell (in link above) unless you go for a proprietary format/charger such as camera batteries. If so you will need a holder such as these:

http://www.digikey.com/product-detail/en/BK-18650-PC4/BK-18650-PC4-ND/2330513

This will allow you to remove the batteries and charge them individually if you want. (Be sure of both batteries getting full charge).
Yes exactly, I don't really feel like using 18650s since they seem a bit untrustable. I think I'd be more confident with a proprietary format battery pack.

LiPo is useful if you need high current.  If not, NiMH may work better.  But, if you feel you must use LiPo, I would suggest you use LiFePo4 as it's the latest technology and doesn't have the "explode" factor that standard LiPo does.  LiFePo4 are readily available outside the US (as most are made in China and HK).  Anyway, they have a little lower voltage (3.7/3.3 per cell) but that actually works out well for battery powered systems.

As far as charging. It's fairly straight-forward.  I typically do a trickle charge via solar with a voltage limiter with a simple voltage devider.  This works with any type of LiPo battery. If you go with a trickle charge and voltage limit, the main thing to worry about is low voltage.  You need to devise a circuit that will terminate when the voltage is lower than a certain amount.  If not, you'll kill your LiPo battery.

Tim
No actually I feel like i must not use LiPo, that's more or less the reason for this topic, since it's popular enough to be on every single google search, and I barely could find info on using simple camcorder batteries by themselves (except for a project where some guy uses an Arduino to do something in a camera, so thanks to that guy all hits in google "camcorder arduino battery" link to his project).
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Have a read of this , may help to alleviate the confusion.
http://batteryuniversity.com/learn/article/types_of_lithium_ion

Lithium Ion is a just a generic name for a large range of differant batteries which have differant chemistries, with Lithium being the common element in them all.
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Is it safe to assume the camera batteries I linked to have this protection circuit embedded?
I do not know if the protection circuit is in the batteries or in the Canon charger and Canon camera. Also it is probably a Chinese knock-off and sometimes they cut corners. Contact the seller and ask.

Quote
..maybe I haven't made myself clear, I don't need help charging...
No, you were clear. I just offered an alternative of a couple of 18650 cells that you could separately test/charge and know that they had protection built in. For those you would need a different charger.

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...but I got confused with your comment "bundled in the outer sheath of the battery...
The coin sized circuit is invisible under the heat shrink plastic (just behind the nipple) and you wouldn't know its there. I get the Sanyo batteries but they are black because the wholesaler that I get them off, seals in the PCB with a black heat shrink sleeve (covering whole battery).

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Does it mean the Arduino would stop functioning just as if I had removed the battery
Yes.

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I don't really feel like using 18650s since they seem a bit untrustable.
The 18650 refers to the format of the battery not the reliability. Sanyo (battery division recently bought  by Panasonic) is second to none in quality and safety. If you buy a Sanyo 18650 you will be safer than buying a no-name proprietary format battery.






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Thanks so much man, I got it at last.
Time to do some shopping.

Thanks again!!! smiley
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