Also the bubbles that come off the sodium carbonate when using a battery charger are hydrogen and oxygen are flammable so have a vent to remove the air or do it out side. Soda ash is not as strong as washing soda. Just FYI
. Sodium carbonate, Na2CO3, (also known as washing soda, soda ash and soda crystals, and in the monohydrate form as crystal carbonate) is the water-soluble sodiumsalt of carbonic acid.