The battery decides how much amperage it accepts at the voltage reaching the battery terminals.
If the current was constant, then voltage would keep climbing once at high states of charge, well above 1, and most 12v batteries at 77f are to remain under 14.8v.
Knowing HOW much amperage is flowing into the battery, at that maximum allowed voltage, is extremely revealing as to battery health and state of charge, as when new that amperage at constant voltage, will taper relatively quickly to the point the battery can be considered fully charged.
When older the battery reaches absorption voltage at a lower state of charge and the amps take much much longer to taper to the level where the battery can be considered fully charged, yet most chargers will still do their egg timer thing and throw the green light and Joe Q ignorant believes the battery is fully charged, when it is not. Ieven if JQI is aware the battery is not fully charged, and tries to restart the charger, often it just quickly switches mack to maintenance voltage and undercharged it remains.
The Ammeter will show joe Q ignorant that is bells and whistles charger is not living upto its marketing claims.
Jimmy Q ignorant will just continue to believe a green light has their best interest in mind.
Ignorance is bliss.
If you can do some simple wire joinery, add one of these, or similar, into the output leads of the charger. Unless it has a temperature sensor on a batteyr clamp, will not affect the operation of the charger:
Power Analyzer - JZCreater Watt Meter Power Analyzer, High Precision RC with Digital LCD Screen for voltage (V) current (A) Power (W) Charge(Ah) and Energy (Wh) Measurement 130Amps - - Amazon.com
www.amazon.com
This device will record amp hours the charger returns to the battery, allowing one to infer how discharged their battery was
It will record the maximum amperage the charger delivered
it will show voltage, and amperage, and do the calculation to display wattage the battery is accepting at that voltage.
These wattmeters are imperfect under about 0.4 amps, usually reading about 0.15 amps too little and under 0.2 amps might read 0.0 amps, so they become less useful on smaller batteries which will taper well below this number when held at charging voltages for long enough. The wattmeters vry pretty widely in how well they do at low amperage, I've had some be pretty respectable, some totally dismissable under 0.6 amps
There re some other shunted ammeters available, with a larger external shunt which can handle 50 or 100 or 200 amps, but few have chargers capable of this much juice.
I have 2 versions of the wattmeter linked above with 8AWG leads, and 45 amp Anderson Powerpoles connectors, and have started my 5.2 liter v8 engine through them.
the 1.4KW starter motor(output) requires nearly 1800 watts of input. I also have a 100 amp adjustable voltage power supply and these wattmeters and their 45 amp connectors see over 50 amps continuous for upto a half hour so far, without issue
I applaud interest in knowing how much amperage a charger is delivering to the battery, and the max voltages the charger is allowing, and for how long they are allowed. I wish more members had this interest and would share data about what their specific charger is doing and then there could be a consensus which charger is actualy capable of delivering the battery to high states of charge before throwing the green light and reverting to a float/maintenance voltage, where very little if ANY additional charging occurs. It depends on the health of the battery, but sufficed to say a older battery held at 13.2v float, is not going to do much if any additional charging.
Actual data is key to judging whether a charger is doing a good job or not, but for 95% a green light and dazzling marketing jibberish, is more than good enough.
