# CALB Cell voltage?



## PeterH (Mar 20, 2009)

Hi there,

Depending on how far you go back or what source you refer to, the max and min safe voltage for a CALB cell seems to change. So let me ask the question to see what everyone thinks today. I'm using 45, 130 Ah CALB cells in my build.

What is the 'fully charged' resting voltage of a CALB cell after a full charge to 3.65 VDC? 

If I understand my ELCON's programming, it will discontinue charging when the cells reach 3.65 VDC each. In my case, with 45 cells, that would be at 164.25 VDC.

Just as importantly, what is a safe voltage of a single cell at full discharge? I mean just before voltage starts to rapidly fall. If I were to bottom balance all of the cells, this is the voltage I'd use as the bottom.

I'm looking for this information to help me decide the minimum voltage at no current, and the minimum voltage at full current to properly set up my Soliton Jr. In my case would I'll probably limit max current to of 500 Amps.

Thanks,
Pete


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## Ziggythewiz (May 16, 2010)

Fully charged is 3.4V. The recommended curve is constant current till you reach 3.6, then hold constant voltage until the current drops to .05C. They should then rest at 3.4.

If you're bottom balancing, I wouldn't take em past 2.5


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## PeterH (Mar 20, 2009)

Thanks for the response. 

Once it is working properly, I'll be using a BMS so I think that means I'm basically top-balancing. So I'll use 2.9 as my min voltage for now and 3.4 as my expected fully charged voltage.

I have yet to run the Elcon to a full charge. I want to be in the room watching the paint dry when I do, and haven't had the opportunity to do so just yet.

Do you have any experience/information with how much they will sag under a full load?

Thanks,
Pete


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## Ziggythewiz (May 16, 2010)

I do not, and 'full load' is a very relative term. If you don't need every drop, you might consider not charging to quite full either. CALB recommends 90%.


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## PeterH (Mar 20, 2009)

Yes... that is a difficult thing to describe. My full load will be very different from someone else's full load. I'll just have to make a guess and adjust based on experience. I expect to be very conservative with driving this rig.

I'd prefer to stay with a 90% max charge to extend the life as much as possible but, as I bet you know, you can't tweak the Elcon charger's programming much... 

And now that I think about it, they never did supply any information on any of the other charging profiles that might have been programmed into this charger. I need to ask my vendor about that again...

Thanks,
Pete


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## dladd (Jun 1, 2011)

PeterH said:


> Hi there,
> 
> Depending on how far you go back or what source you refer to, the max and min safe voltage for a CALB cell seems to change. So let me ask the question to see what everyone thinks today. I'm using 45, 130 Ah CALB cells in my build.
> 
> What is the 'fully charged' resting voltage of a CALB cell after a full charge to 3.65 VDC?


I charge to 3.5vpc, and they settle at 3.4vpc after sitting.



> If I understand my ELCON's programming, it will discontinue charging when the cells reach 3.65 VDC each. In my case, with 45 cells, that would be at 164.25 VDC.
> 
> Just as importantly, what is a safe voltage of a single cell at full discharge? I mean just before voltage starts to rapidly fall. If I were to bottom balance all of the cells, this is the voltage I'd use as the bottom.


when I was doing a bunch of cell testing, I found that at a .3c discharge current my CALBs were falling off the cliff by 2.7v. I didn't go any further than that. 2.5 would be VERY close to 2.7v with regards to energy, seeing as you are on the very steep part of the curve by then.



> I'm looking for this information to help me decide the minimum voltage at no current, and the minimum voltage at full current to properly set up my Soliton Jr. In my case would I'll probably limit max current to of 500 Amps.
> 
> Thanks,
> Pete


I have my cells limited to 500a, and find I often hit 130v (48 130ah cells, 153v nominal) at 500a depending on the temperature. However, I have several weak cells so I see much more sag than most folks with these, so don't go on my data! 

personally I'd probably set a no load low voltage of 3.1vpc (I assume this just is used as a go/no go for powering on the controller?), and a loaded low voltage of 2.8vpc and see how it goes.


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## Elithion (Oct 6, 2009)

PeterH said:


> If I understand my ELCON's programming, it will discontinue charging when the cells reach 3.65 VDC each.


The charger has *no *idea what EACH cell's voltage is. It only knows the _total_ pack voltage. Based on that, there is no way for it to know the _individual _cell voltage. Before a pack is top balanced, by the time the charger stops, some cells will be overcharged.



PeterH said:


> In my case, with 45 cells, that would be at 164.25 VDC.


ONLY if the pack is perfectly top balanced. 

Otherwise, at 164.25 VDC, some cells will still be at 3.3 V, and the most charged cells will be at, say, 5 V.

See this explanation of the mechanism that ruins Li-ion cells when relying only on a charger to limit the charger.

This application note tells you how to specify an ElCon charger for a Li-ion pack. Note that a "Li-ion profile" does not harm a top balanced pack (nor does it have any advantages over a plain CCCV profile), but will harm a pack that has not yet been top balanced.




PeterH said:


> I'll be using a BMS...


Install one _before _your first charge, or you might harm the most charged cells during your first, uncontrolled charge. If you're going to install a BMS anyway, do it sooner rather than later, and save yourself the hassle of having to replace a few damaged cells later.

Here a selector of all Li-ion BMSs available.


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## mizlplix (May 1, 2011)

Heh...

Elcon chargers only have one true charge algorithm at a time. The rest is just 10 steps representing cell count in your pack. 

The algorithm is programmed by the US Distributor. the charger has 10 step settings representing ten different cell counts in the pack, those you can change using the button under the label opposite the side with the colored L.E.D.s.

It is not "field programmable with tools included" as they so fondly advertise.

That is false.

it will cost you 2 way mailing and $75.00 to change your algorithm.

Miz


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