Few days ago I was trying to recharge a bank of ten batteries connected in parallel. I connected the charger directly to the battery terminals at 13.75 V as specified in battery manufacturer datasheet.
The problem: the batteries were about 11.4 V at that time and my DC supply transformer was supplying a the maximum current of 50 A. Well ... 50 A for 10 \$\times\$ 9 Ah batteries is way too much, not to mention that the wires started to melt due to high current so I realised that I need something to limit the current and quickly figured it out that I need a resistor.
I've seen numerous youtube videos and documentation about how a resistor works and it's limitations, I ended up using this calculator.
13.75 V at 4 A = 3.4375 \$\Omega\$ resistor, but I found a 3.3 \$\Omega\$ resistor which (based on the calculator) should be capable to limit current at 4.16 A, dissipating with 57.29 W of heat.
Big surprise when I connected it on positive terminal (tried on negative also) and only about 0.6 A of current was flowing to the batteries, despite the fact that the batteries were discharged and without any kind of resistor they alone would draw > 30 A.
So my question is: why is that? Why does the 3.3 \$\Omega\$ resistor limit the current to 0.6 A and not to 4.16 A as calculated. Is there a possible difference in resistance which doesn't allow the current to flow at max capacity?
I've also tested the resistor with a multimeter and the resistance is fine. I've also connected it to positive and negative of a single battery and about 4.3 A of current was flowing - so it works as it should but not when connected with the charger.
I have absolutely no clue about it, could someone please help me to figure it out?