It depends on the battery chemistry, battery depth of discharge and charging method. Can be as low as 0.1C for trickle charging lead acid batteries up to say 0.7-1.2C for fast charging Li-Ion batteries.

Generally lead acid and sealed lead acid battery chargers (as well as other battery chemistries) are rated for a maximum size battery they can charge which takes this initial charging inrush into account.

If this is an application, have you checked the sales literature of the battery charger?

"Inrush current in terms of %age of float current" AT THE STARTUP of its charging cycle cannot be predicted with certainity because this depends on the internal resistance of battery. This will vary with the type of battery also.

AT THE STARUP OF CHARGING CYCLE, I presume that the battery is completely discharged. Accordingly the internal resistance is low & therefore battery can draw large current if source is capable of delivering. Thus a current limited source ( read battery charger ) is must for charging a completely discharged battery. If source current cannot be limited and if a completely discharge battery is connected to the source, then chances are that the source will fail or its fuses will blow since it will see it as a "short circuit" on output side.

Thanks and regards

Ashok Toshniwal, Bangalore, India

The current will be always be (V_C – V_B) / (R_C + R_B), that is, the difference between the charger and battery voltages divided by the sum of their internal resistances, effectively as stated by ashoktoshniwal.

However he is wrong on one issue, when a lead acid battery is fully discharged the electrolyte is nearly water and has a high resistance. The result of this is that when a charge is connected the terminal voltage of the battery rises rapidly to the charger open circuit voltage and very little current flows. As the battery starts to charge the electrolyte density increases and resistance decreases. The current then increases and, if the charger is limited current, the battery voltage will drop.

This phenomenon will give a totally flat battery the same voltage current characteristic of a fully charged battery at the start of the charge. Remember that lead acid batteries should never be allowed to be discharged totally flat.

Regards

Chas

In good chargers it has no in-rush current more than its charging rate set in charger.

Otherwise it depends on the discharged conditon of battery & the difference between battery & charger voltage [ in cheaper ones it also depends on line voltage].

It is highest and lowrs with charging. When Battery has charged it is zero.

Kazek

never mind