sitting for 3 weeks, now showing full all the time

[Mike Dabrowski 2000]

During the charging the energy is absorbed by the battery as charge, and little heat is generated. It is in the final topping zone where all the charge energy is changed into waste heat. If you are using a 350ma charger, that heating period may not be reached if you do not charge long enough to get into that zone.
This is why it is recommended to put a voltmeter on the terminals and to watch for the voltage to stabilize. If the process is cut short especially when there is evidence of the pack being unbalanced (recals strange SOC behavior), only part of the pack will be balanced, the cells that really need to be charged because they have fell behind the rest due to self discharge,may not get fully charged.
Since the purpose of the balancing charge is to get all the cells full, one should really be watching to confirm that the pack is really fully charged.

A single high internal resistance cell can get over 150F and vent even if the rest of the pack is still in the charge zone.
From what I have heard form people that have built their own chargers, most are running the fan. Even running it at 4-6V will keep the pack cool.
Cool ambient temps will also help.

[3ps]

OK. I will do some more reading. If I measure the voltage and determine I need to run the pack for 20 hours instead of 15 (for example), can I then rely on this 20 hour figure or do I need to check each time I charge?

FYI my charger originally came from retepsnikrep.

[kennysmith]

The term "vent" has been mentioned a couple times and should be explained. I think it means the battery actually blows out the side, thereby ruining that cell. Too easy to pass over that word without understanding the seriousness.

[Mike Dabrowski 2000]

The pack will take different amounts of time each charge, as the pack balance, the starting SOC, will ultimately determine how long it takes to get fully balanced.
In theory we should see less balancing time as the pack is charged more frequently.

Venting is where the cells internal pressure has risen to the point where the pressure relief valve right under the bump on the positive terminal pops open and vents gasses and some potasium hydroxide fluid. This permanently changes the battery capacity by allowing the cell to develop dry areas of the plate, effectively making it a cell with reduced active plate area.
A look inside a cell:
\Battery packs exposed - MIMA Honda Insight Modified Integrated Motor Assist

Unfortunately the white powdery dried potasium hydroxide cannot be seen without removing the heat shrink.
If you are standing next to the pack and it is quiet, you will hear a psssss sound like a hole in a tire if you vent a cell. Not something you want to hear, and is the reason I have a PTC monitor built into my chargers, which will shut down when a high temp threshold PTC resistance is detected

[3ps]

Hi,

I left my car for a week, and this problem happened again.

I have 2 questions:

1) Is this "freezing" of the charge indicator a common issue, and does it indicate anything in terms of long my battery has left?

2) How do I run the battery fan while I am using the charger?

Thanks.

[Mike Dabrowski 2000]

Actually under the positive terminal (bump) of each cell there is a poppet valve, that is there to vent any pressure that exceeds the valves pressure rating. The vent can allow the potassium hydroxide electrolyte to vent, which eventually leads to dry spots in the felt like material that is supposed to be saturated with the electrolyte.
Once this happens, the cell will never have full capacity again.

Just connect a 6 to 12 V @ ~1A power supply to the fan wires, and it will cool the pack.

[3ps]

That's a bit of a nuisance. I am having to grid charge it twice a week to avoid recals. Is there an easy access point for these wires?

Any thoughts on if this latest quirk means the battery is close to the end?

[mrkcohen]

Apropos of nothing:

Just rig up a 12V wall wart for running the fan = Just connect a 6 to 12 V @ ~1A power supply to the fan wires.

I never heard the phrase "wall wart" before. For some reason it made me chuckle.

Thanks for that...

[Mike Dabrowski 2000]

You need to discharge as completely as you can between charges to increase the cell capacity.
The reasom my charger has a custom harness is so the fan, PTC, and HV wires can be brought to a single safe connector that you can easily plug into in a minute.

[3ps]

Ok so here is the scenario. I use the car Mon-Fri and sometimes at weekends.
I do ~50 miles per day.
It generally does a negative recal every 4 days.

So what I have planning is to do an overnight charge on Sunday, and then another on Wed night.

But I can't guarantee that the battery is discharged when I do this. For example I just did a charge on Sunday night. I decided to see if I could last the week, but yesterday morning it did a recal. But it did it on the way into work. So by the time I got to work it had sorted itself out.

Is it OK to charge/balance it that evening, with the recal finished and everything back to "normal" with a healthy charge showing?