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Lithium ion battery question (not really rc related)
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candy76man
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Lithium ion battery question (not really rc related) - 02.11.2013, 06:15 PM

Hey, I can't find much info elsewhere on what I am doing and figured there are some electrical gurus that frequent these forums so I hope it's ok to post a non rc related question here anout batteries.

Here's what I did. I have a set of porter cable cordless power tools that run on 18v lithium ion packs. The packs state that they are 1.1 ah on the sticker which I think means the pack is made up of 1100 mah cells (18650 cells). I ordered some panasonic 3400mah cells which is the highest capacity 18650 size cell currently available. I removed the 5 1100mah cells from my porter cable pack and replaced them with 5 of these panasonic cells thinking I should get about three times the run time on my tools.
Is there any reason that shouldn't be the case? I ask because I was running a tool today (reciprocating saw) with the modified pack and after a few minutes of continuous running it suddenly acted like the pack had died...my second pack that still has the stock cells in it ran a lot longer without issue and when I put the modified pack back into the same tool a hour or two later it ran again like it had plenty of power, although I didn't run it for long.

Is it possible the electronics pcb in the battery pack will only work correctly with 1100mah cells? is there some difference between 18650 cells besides just the capacity?

any info on this would be great
   
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pinkpanda3310
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02.12.2013, 01:54 AM

Does each of the new cells have it's own protection circuit? Are the new batteries labelled NCR and the old ones IMR?
   
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02.12.2013, 02:38 AM

How were they charged? Were they full capacity beforehand?


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nativepaul
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02.12.2013, 08:23 AM

Are the actually LIons, what are the voltages? Did the saw sound like it was reciprocating as fast as normal? Over triple the capacity from the same chemistry in the same size can sounds suspicious to me, NiCads only doubled in their whole lifetime and NiMh are approaching their death and still haven't doubled, despite subC cans growing.

Do you have a spec sheet for them?

In boat racing were we have maximum battery weights we are now seeing some cells that offer more energy density but sacrificing power density, 6200mah cells the same weight as most 5000s but 14c instead of 30c+, while that is less than 25% increase in capacity for a 50% reduction in current capability, could it be possible that they have taken that same ratio to the extreme doing it 5 times would net near 3400mAh, say the original LIons were 30C reducing the C rate 50% 5 times leaves a <1C cell, using it at anything over 3A could be taxing it severely and reducing its capacity, did they warm up in use?


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Last edited by nativepaul; 02.12.2013 at 08:40 AM.
   
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candy76man
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02.12.2013, 05:49 PM

Ok, the panasonic 3400 mah cells model or part number is NCR18650B so they are NCR but the cells that came in the porter cable pack do not say NCR or IMR on the label The only printing they have one them says SE US18650VT and below that is this number T T1125QH09S.

I'm pretty sure these 3400mah cells do not have protection, I figured that's built into the pcb in the power pack.

I tried to use the new pack again today and it was the same, ran for a minute or so and then just acted like it's dead, if I let it rest for a minute it would run again for a bit and then peter out, about an hour later my old pack ran dead so I tried the new one again and this time it ran without a problem off and on untill I finished what I was using it for.
One thing I notice is when the original cells go dead the tool will other run at full power or not at all, but the pack with new cells isn't doing that, it's will suddenly run real slow and then stop.

The 3400mah pack has never gotten warm to the touch when charging or in use and it the tool seemed to run a bit faster on the 3400mah cells untill it stops running anyway.

This is a private test done on the 3400 cells. Here is another review on them

I did not charge them before soldering them into the porter cable pack, I'm using the stock charger for the packs. when it goes to trickle charge they are usually right around 18.2 volts and will get up to 18.9 volts if I leave them in the charger over night....same as the stock pack will do.
   
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pinkpanda3310
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02.12.2013, 06:50 PM

To me it looks as though the cells you bought are hobby grade and the stock cells are industry grade.

The NCR ones you linked are good for about 3A continuous current draw while the stock cells are rated at 15A (when new http://www.google.com.au/search?q=SE...JIWTiAfwloGwCA). In rc language - you bought cells with a much lower C rating and your sucking the guts out of them.

That's my perspective anyway.
   
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pinkpanda3310
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02.12.2013, 07:21 PM

I found a few alternatives you might look into. It also looks like Paul is spot on with the push-me-pull-me effect of discharge rate vs drain rate.

http://www.oveready.com/battery-/bat...y/prod_47.html

http://www.orbtronic.com/batteries-c...ell-high-drain
   
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candy76man
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02.12.2013, 07:52 PM

Quote:
Originally Posted by pinkpanda3310 View Post
I found a few alternatives you might look into. It also looks like Paul is spot on with the push-me-pull-me effect of discharge rate vs drain rate.

http://www.oveready.com/battery-/bat...y/prod_47.html

http://www.orbtronic.com/batteries-c...ell-high-drain

Hmm, I did some research before I bought them but I completely missed the fact that there are so many different types of 18650 size battery, I thought lithium ion batteries were lithiumion batteries, didn't know there were different chemistry and materials used to make them. So basicly for power tools I need a IMR type cells? 15 to 20 amp continuous discharge rating?
   
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pinkpanda3310
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02.13.2013, 08:44 AM

I should correct my last post I meant to say 'discharge rate vs capacity'

Generally speaking I would look for IMR cells but I would also still pay attention to the specs. One of the links I gave is for AW IMR cells which are highly revered in other circles because it boasts +15A current. The second link is for panasonic cells which boast 10A current with marginally longer run time.

There are many other batteries that claim all sorts of things but if you stick with trusted brands the specs should be reasonably accurate (sounds familiar doesn't it).

If you really want to satisfy your puzzle about your recent upgrade you could connect the battery pack to a cordless drill using wires and an watt meter in series. Pull the trigger and add a little resistance to the drill (maybe put a glove on) then watch how many amps are pulled and volts dropped. Repeat with the stock battery and compare results.

Crude? Yes, very crude but it should be kinda easy to tell the difference between 3A cells and 10A cells.
   
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candy76man
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02.13.2013, 09:27 PM

Quote:
Originally Posted by pinkpanda3310 View Post
I should correct my last post I meant to say 'discharge rate vs capacity'

Generally speaking I would look for IMR cells but I would also still pay attention to the specs. One of the links I gave is for AW IMR cells which are highly revered in other circles because it boasts +15A current. The second link is for panasonic cells which boast 10A current with marginally longer run time.

There are many other batteries that claim all sorts of things but if you stick with trusted brands the specs should be reasonably accurate (sounds familiar doesn't it).

If you really want to satisfy your puzzle about your recent upgrade you could connect the battery pack to a cordless drill using wires and an watt meter in series. Pull the trigger and add a little resistance to the drill (maybe put a glove on) then watch how many amps are pulled and volts dropped. Repeat with the stock battery and compare results.

Crude? Yes, very crude but it should be kinda easy to tell the difference between 3A cells and 10A cells.
Thanks for all the help, SO I guess these 3400mah cells would be well suited to use in a laptop battery or something like that that has low amp draw?

Now I need to find some 2000mah imr cells at a reasonable cost....10 bucks a piece would still be 20 less than a new porter cable pack and would be almost double the capacity so that would be worth it to me.
   
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pinkpanda3310
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02.13.2013, 11:04 PM

I'm not all that familiar with computers but I think 3A cells are suitable Hope you get it all worked out
   
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