Is there lag when charging a lithium battery?

[Trex]

Hi,

When charging my hv battery yesterday with the petrol motor, see "It takes 3.2lts of petrol to charge the battery in my Phev", I noticed it took longer for the first 2 bars that were not lit up to light up than majority of the others. see :

With 1 bar showing (out of 16) on the hv battery display ( I ran the AC till the petrol motor started and then pressed the charge button) I commenced the test:
7.31am-1 bar after pressing charge button ( this bar was already lit )
7.37 -2 bars
7.42 -3 bars
7.45 -4 bars
7.48 -5 bars
7.52 -6 bars
7:55 -7 bars
7.59 -8 bars
8.02 -9 bars
8.06 -10 bars
8.10 -11 bars
8.14 -12 bars
8.19 -13 bars
8.28 -14 bars petrol motor idled down here
8.34 -14 bars petrol motor stops and charge mode still showing on display

Notice that it took 6 mins to light bar 2 then 5 mins to light bar 3 then a lot of 3 and 4 mins (which if I had noted the seconds could have evened out to something roughly the same) until it got towards the end of the test ie 12 to 13 bars 5 min, 13 to 14 bars 9 min (this could be explained by a battery not accepting a charge as the voltage gets higher).

Now I ran the high voltage air conditioner to flatten the battery and make sure the hv battery was empty (to hot here to run the heater)
and made the petrol motor start before I pressed the charge button ie the hv battery was discharging before it started to charge.

So what I trying to say is does a lithium battery when it changes its state from discharging to charging have lag, or what member maby I think would call hysteresis, or do you think it is just the gauges or sensors or something? Does the chemical reaction take a while to build up? EDIT Perhaps I should have said does the reversal of the chemical reaction take a while to build up?

My head hurts. :lol:

Regards Trex.

 

[RazMan]

Trex - you really need to get out more :lol: :lol:

 

[jaapv]

The charging software controls the charging rate to prevent the battery from being damaged. Most likely the variations are temperature-related.

 

[Trex]

Razman: you are right. Off to the pub now. :lol:

jaapv : You could be right about temperature although I had warmed up the petrol motor,it started nearly straight away, going to the petrol station and back about 8 mins away ie 16 mins there and back. Stopped for 5 min,when I got back home, to top up fuel to brim. Then did test. It is still very warm here.

I think because I did not note the seconds in this test it could be hard to make any assumptions . Anybody think the same?

Regards Trex.
Not the ICE, battery pack temperature - it heats up with charging.

 

[Stvtech]

I'm cannot be specific about the batteries in a PHEV, but other Lithium Polymer\Lithium Ion batteries have to be charged using two distinct phases.

The first is constant current, where the charger pumps as much of the available current as the battery can safely handle into the pack, before switching to constant voltage at a much lower current for the last part of the cycle where the cell voltage is brought up to it's maximum fully charged value - which in the case of LiPo chemistry is 4.2v/cell.

Applying this to a PHEV, this is why rapid chargers can only safely go to 80% - any longer and they risk raising the cell voltage above the maximum value, which will kill the battery pretty quickly and possibly in a very dangerous way. I am assuming that rapid chargers bypass the normal CC \ CV charge circuitry in order to apply 400v into the PHEV's 300V pack, thereby ramming a lot of current into the pack in the shortest possible time.

 

[jaapv]

I'm cannot be specific about the batteries in a PHEV, but other Lithium Polymer\Lithium Ion batteries have to be charged using two distinct phases.

The first is constant current, where the charger pumps as much of the available current as the battery can safely handle into the pack, before switching to constant voltage at a much lower current for the last part of the cycle where the cell voltage is brought up to it's maximum fully charged value - which in the case of LiPo chemistry is 4.2v/cell.

Applying this to a PHEV, this is why rapid chargers can only safely go to 80% - any longer and they risk raising the cell voltage above the maximum value, which will kill the battery pretty quickly and possibly in a very dangerous way. I am assuming that rapid chargers bypass the normal CC \ CV charge circuitry in order to apply 400v into the PHEV's 300V pack, thereby ramming a lot of current into the pack in the shortest possible time.

That is exactly what they do, and I am still surprised Mitsubishi implemented the option. It cannot help with battery life.
I am even more surprised that the software apparently allows repeated charging after a rapid charge, which offers the owner the scope of killing/blowing up the battery

 

[Regulo]

I have a domestic energy monitor, and I've noticed that if I plug the car in straight after use, it sometimes takes about 10 to 15 minutes to instigate charging. I put it down to the battery maybe being hot. Any ideas, comments?

 

[Trex]

Hi,

Ok I found the answer I was looking for in a website called Electropaedia .

Electropaedia states : "During charging the chemical reaction lags behind the application of the charging voltage and similarly, when a load is applied to the battery to discharge it, there is a delay before the full current can be delivered through the load. As with magnetic hysteresis, energy is lost during the charge discharge cycle due to the chemical hysteresis effect."

For the moderators Electropaedia state :"You may freely use extracts of the information published here in your own publications or Web sites but only if, in each instance, you prominently acknowledge Electropaedia as the source with a link to the web site as follows http://www.Electropaedia.com. "

This could also help explain why I am getting better fuel consumption using a technique described in " I use charge mode for better fuel consumption" in this section ie technical discussions.

My head still hurts (you there RazMan?) :lol:

Regards Trex

 

[anko]

I have a domestic energy monitor, and I've noticed that if I plug the car in straight after use, it sometimes takes about 10 to 15 minutes to instigate charging. I put it down to the battery maybe being hot. Any ideas, comments?

It can happen later in the process as well. I have noticed that if you briefly interrupt the power, it will skip the pause :shock: