Conditioning new lithium battery without riding the bike?!

[rooel]

I have just bought a new 24 volt 10 amp LiFePO4 and would like to condition it by running it down to the cut-off point a few times and fully recharging. At present however I do not have time to ride the bike the requisite number of miles (15 to 20 each time, I expect), but I can tape the throttle to full-on, turn the bike upside down, and switch on the battery.
As the wheel is not under load it takes quite a while to run down the battery, but can someone confirm that this method will not adversely affect the battery or the motor?

 

[flecc]

It won't adversely affect anything, but it will just seem to run forever, very many hours and into a second day, maybe beyond. I once tried this with a battery that was already very low, one LED lit out of five, and after over seven hours nothing had changed, it was still spinning on just as healthily.

The only way to do a condition discharge is under load, i.e. riding the bike. You don't have to do a discharge run all in one go, you can do it in as many short stages as you like to run it right down and it will be just as effective.

 

[rooel]

Thanks, flecc. I can confirm your advice: yesterday I rode for ten miles then turned the bike upside down and the motor ran for a further seven hours before the battery reached the cut-off point. Today, not being free to ride any distance, I started the motor at around 9 am and 7 hours later it is still running. Looks like it will not stop until Sunday afternoon. If I can use the bike next week I shall do a series of short runs, but always with a spare battery in the bag in case I lose power far from home.

 

[Mike63]

condition it by running it down to the cut-off point a few times and fully recharging.

How many times does this need to be done ?

 

[flecc]

Advice varies considerably Mike, anything from not at all to three times. Once is all that is really necessary to stabilise the cell contents and reset any integral battery meter zero point that might be necessary.

 

[Ajax]

I've seen reference to this before and i've always just taken it as read, but Is this 'conditioning' of the battery really of any benefit? Also can someone explain the science involved, and whether this applies to Li-Pols or just nicads.

I have a relatively new Li-pol which doesn't seem as powerful as my original battery was, would this help any, or have i just bought a battery which was sitting on a shelf for a while. eg buyer beware.

Thanks

 

[flecc]

It may help and won't do any harm Ajax. There are two aspects where lithium batteries are concerned. One is that today's high density content cells may need to have their internal chemical charge evened out immediately after manufacture, and fully charging to the absolute maximum, followed by fully discharging to the safe minimum voltage is the most effective way to ensure that. There are the odd pundits who say this is a waste of time, but I know of no battery manufacturer who says this, most advising conditioning at least once.

The other aspect concerns the better type of battery integral meter. These need to know what is empty to measure from in order to give a reasonably good content measure. The full discharge to empty gives the zero point from which the meter can measure content. Over time this drifts off with variable charging and usage, so it's sometimes necessary to repeat the conditioning cycle to reset the meter zero. Some sources recommend every 30 or so charges, but I think that's excessive, unduly stressing the battery. Basically the greatest stress on a lithium battery occurs during the top 10% of charging and bottom 10% of discharging, so it's best to avoid doing both frequently. Charging frequently is the best way to run a lithium battery, avoiding full discharge every time if possible.

 

[Mike63]

Advice varies considerably Mike

...cheers for that Flecc.

 

[rooel]

With the bike up-ended, the throttle taped full-on, and the wheel spinning away it took eleven hours for the battery to run down to its cut-off point. I decided to condition the battery partly to comply with the general advice to do so, but also because I am wondering if this 24 volt 10 amp LiFePo4 is up to standard.

When it arrived the voltage was reading around 26.5 volts, but when connected to the charger it would go up to only 27.8 volts (whereas my existing 24 volt LiPo and a 24 volt Li-ion have always charged up to 29 volts). When I drained the battery for the first time (10 miles riding the bike and the rest with the bike upended) the cut-off voltage was around 22 volts which is two or three volts lower than the other two batteries when they are drained to the cut-off point. When I drained the battery for the second time (with the bike up ended) the voltage cut-off point was again around 22 volts. I have charged again overnight and once more the fully charged voltage is just under 28 volts. The other thing I noticed on the second charging was that the voltage rose from 22 volts to 25.5 within 10 to fifteen minutes then rose at the normal rate from that to just under 28 volts over the next five hours or so.

Does this suggest that there is a defective cell or two in the new battery? It is the first LiFePO4 I have used.

 

[flecc]

Not necessarily, LiFePO4 cells are rated at lower voltages than other lithium types, nominally 3.2 as against 3.7 volts. Some use additional cells to compensate, but whether they do or not, the fully charged voltages are not directly comparable. LiFePO4 fully charged are at about 3.6 volts per cell, other lithium types are at about 4.2 volts per cell peak, so it seems your battery has eight cells where your old one had seven cells reaching those higher voltages.

 

[vhfman]

As flecc says the cell count and chemistry differences between your previous batteries and your new LiFePO4 battery will show the difference of end point voltage. For 8S LiFePO4 the charge voltage should be 29.2V compared to7S Li-ion/LiPO of 29.4V, so actually not a lot of difference.
I wonder what the charger output voltage is for your LiFePO4 battery? It should be as I mentioned 29.2v for a nominal 24V LiFePO4 battery, assuming 8S cells. If the charger outputs with no battery attached, you can carefully measure the voltage and see if it’s correct.

Chris

 

[rooel]

Thanks, flecc and vhfman, for setting my mind at rest. The LiFePO4 charger is labelled at output 29.2 for 24 volt 10 amp, but I would prefer not to check this as there is a possibility of a short if I measure the voltage across the output terminal which is a small coaxial.

 

[Davanti]

It may help and won't do any harm Ajax. There are two aspects where lithium batteries are concerned. One is that today's high density content cells may need to have their internal chemical charge evened out immediately after manufacture, and fully charging to the absolute maximum, followed by fully discharging to the safe minimum voltage is the most effective way to ensure that. There are the odd pundits who say this is a waste of time, but I know of no battery manufacturer who says this, most advising conditioning at least once.

The other aspect concerns the better type of battery integral meter. These need to know what is empty to measure from in order to give a reasonably good content measure. The full discharge to empty gives the zero point from which the meter can measure content. Over time this drifts off with variable charging and usage, so it's sometimes necessary to repeat the conditioning cycle to reset the meter zero. Some sources recommend every 30 or so charges, but I think that's excessive, unduly stressing the battery. Basically the greatest stress on a lithium battery occurs during the top 10% of charging and bottom 10% of discharging, so it's best to avoid doing both frequently. Charging frequently is the best way to run a lithium battery, avoiding full discharge every time if possible.

Thanks Flecc. That is the best explanation of something that has always bugged me.

A day never goes by that I don't learn something new on this forum - "every day is a school day!"

Thanks again

Don