#BATTERY STATUS IN PARALLEL CONNECTION SERIES#

Charging close to 100% SOC battery just with 1% of C (less than 1 A for a car battery) rises the voltage to above 14 V.

And the same happens even more to the other direction. Cranking at 100 A will drop to about 11 V and the voltage drops maybe to 10 V at 200 A. putting lights on on a car (~15 A) would drop 12.7 -> 12.1-12.4 V depending on the battery. But when you put some load to that 12.7 V battery, the voltage drops very easily a few tenths. 100% SOC battery may have 12.7 V and 0% 11 V (you shouldn't discharge most batteries that much). You won't be seeing big currents from one lead acid battery to another, if they have equal amount of cells and no cells are shorted due to aging. This doesn't happen,-you need to use the 'Donor' car's battery to supply start current.

The person you helped could then start his car,drawing start current with impunity. If this was not the case,when you applied the jumper leads,there would be a blinding flash,it would instantly charge the flat battery,they could disconnect,& the 'Donor' car could drive away. This 'resistance' limits the current flow into the battery when you are trying to charge it. OK,it's not a real resistor,but an external circuit sees the energy used in converting the battery's internal chemical state from discharged to charged (or vice versa),as power dissipated,implying the presence of resistance. When the battery is flat,we can draw it with a greatly increased value of internal resistance.

#BATTERY STATUS IN PARALLEL CONNECTION SERIES#

If you draw the equivalent diagram of a battery,it consists of an ideal battery,in series with its internal resistance,drawn as a resistor. Batteries don't store an electric charge directly-they convert the charge into a chemical relationship between the internals of the battery. (2)Capacitors have an extremely low internal resistance. If you try LiIon, LiPo type and exceed the charge current limit by 5x or 10x, trouble is in the horizon and perhaps imminent.īatteries don't work like that! If you parallel a charged & uncharged capacitor in parallel,what you described does happen,because:- (1)Capacitors actually directly store an electric charge. SLA's and lead acid in general is a lot more forgiving. When you exceed that by significant amount, damage is not just possible but probable. In fact, all batteries has an upper limit of charge current.

Now if you are dealing with the 'deep discharge' kind, their design is not to handle large rush of current but instead trying to get as much capacity out of the battery as possible. Between your contact resistance and internal resistance, I doubt most car battery can deliver 200A to the other battery for long. Since even a very small car would need 200+ amps to start, so car battery design is designed to deal with large currents. The bigger the difference in SOC (state of charge), the bigger the rush.

So, when two car batteries get together, current from the one with more charge 'rush' to the one with lower charge. Car batteries are 'high discharge' instead of 'deep discharge' (aka marine batteries in the USA) - high discharge meaning they can discharge high current but usually doesn't discharge a lot (ie: not discharging deep) - once the car got started, the battery stop discharging and begin charging.

Battery status in parallel connection