iMax B6AC Charger Issue

[Nox]

I have a 5200mAh 7.4v (2s) 50C Continuous, 100C burst LiPo battery that I am trying to charge with an iMax B6AC charger. I set the charger at 5.0 A 7.4v (2s) on the LiPo Charge mode. The battery has already been balanced. Once it does the battery check and I hit enter, it automatically goes to 1.0 A or less and will only go down from there. I'm using the AC power supply so I figured it would be enough power to give it a continuous 5.0 A charge. After 15 minutes of charging, going down to as low as 0.6 A charge, it has now only charged 128 mAh.

Question 1: Why are the charging Amps so low even though I set it to 5.0 Amps?
Question 2: Why does it tell me the charge is finished (in fast charge mode) when it's not?

I'm looking to sell my RC car and I want to make sure the person that buys it isn't getting a bad battery charger or battery.
Any input/help will be greatly appreciated! Thanks!

 

[Merv]

If you balanced the pack, then it’s changed. The balance setting on the iMax also changes the pack. The amps go down as the pack reaches full charge.

Try either, using the pack or use the storage setting on the iMax, then charge again. The storage setting brings all cells to the same mid charge level, also balancing the pack.

 

[Hai-Lee]

Once the chanrge was determined the number of cells it will NOT allow the battery to be overcharged. Overcharging a LiPo is a very dangerous thing with similar results to shorting one out. The reason that the charge current drops is because any higher charge current would be force feeding what is an already charged battery and damage would ensue.

Use the discharge function on the charger set for around 2A so that the battery is really flat and then do a balance charge. This will give you the maximum charge and will show the current battery capacity.

Have fun!

 

[quorneng]

Nox
You need to use the individual cell voltage display as LiPo chemistry is very sensitive to cell voltage.
If it is showing 4.20 V on each cell then the battery is fully charged. The Imax simply will not put in any more amps
It is also useful to check the cell voltages as you start a charge. If the battery was at 'storage' level then then the cell voltages should start off at about 3.85 V and slowly rise during the charge.
If the battery is is good condition the charge amps should not start to drop until the cells are at about 4.1 V. If the cell voltages are different by more than about 0.2 V the Imax will reduce the charge amps for safety.