So I was asked in another thread about battery chargers. Given I have some design experience in this field and given I hear so much fluff circulated about chargers I though I would put a few through their paces.
I will add more detail at time goes by, but I though for now I would just post up some thoughts on 2 chargers, the CTEK the most people rave about, and a lesser known company called GSL electronics which is an aussie company.
First let me start by saying this. Battery chargers need only operate in 3 modes, constant current, constant voltage and float. Anything else is marketing drivel and snake oil. The major mode that sucks people in is desulphation, and this is questionable at best. If you battery is suffering from irreversable desuplhation that can't be resolved through normal charging the the battery is stuffed. You may extract limited life out of it, but dont rely on it for anything critical. And lets make a point here, keeping your beer cold when camping is critical..
So the three phases of charging are Constant Current, Constant Voltage and Float. Sometimes people use other terms, like Bulk charging, maintenance etc. Constant current is the first stage, where your charger is suppling as much energy as possible to the battery. When it does this, the voltage may be below your standard 13.8 (depending on battery chemistry) that you normally see. Once the battery has consumed a certain amount of energy, it will draw less current. Once this happens, your charger voltage will rise to the voltage you would expect to see when charging, this is called constant voltage mode and is the second stage. After some time in constant voltage mode, your batttery will become fully charged, and in this mode its drawing next to no energy from your charger. When the charger detects the current draw has dropped below a certain amount, it should lower its voltage to a float voltage, which is less than the constant voltage mode. The idea here is simply to supply enough energy to overcome the battery's own internal losses and keep your battery fully charged.
When I test, I am looking for several things,
How I test. I use 4 instruments typically. A DC load tester, a DC powersupply, a voltmeter and an oscilloscope. In subsequent posts you will see some pics of some of the gear. Given I am currently waiting on DA for my shed its all a but limited. Most of my test gear is still packed in boxes from the move and I only have notes from the tests I have done on the gear so far.
I will end this part here, and my next post will a very summarised version of the CTEK, followed by another post with the GSL. Just goint to go off and cook dinner now!
I will add more detail at time goes by, but I though for now I would just post up some thoughts on 2 chargers, the CTEK the most people rave about, and a lesser known company called GSL electronics which is an aussie company.
First let me start by saying this. Battery chargers need only operate in 3 modes, constant current, constant voltage and float. Anything else is marketing drivel and snake oil. The major mode that sucks people in is desulphation, and this is questionable at best. If you battery is suffering from irreversable desuplhation that can't be resolved through normal charging the the battery is stuffed. You may extract limited life out of it, but dont rely on it for anything critical. And lets make a point here, keeping your beer cold when camping is critical..
So the three phases of charging are Constant Current, Constant Voltage and Float. Sometimes people use other terms, like Bulk charging, maintenance etc. Constant current is the first stage, where your charger is suppling as much energy as possible to the battery. When it does this, the voltage may be below your standard 13.8 (depending on battery chemistry) that you normally see. Once the battery has consumed a certain amount of energy, it will draw less current. Once this happens, your charger voltage will rise to the voltage you would expect to see when charging, this is called constant voltage mode and is the second stage. After some time in constant voltage mode, your batttery will become fully charged, and in this mode its drawing next to no energy from your charger. When the charger detects the current draw has dropped below a certain amount, it should lower its voltage to a float voltage, which is less than the constant voltage mode. The idea here is simply to supply enough energy to overcome the battery's own internal losses and keep your battery fully charged.
When I test, I am looking for several things,
- Ripple current that is bad for batteries.
- Will the charger supply its rated current in constant current mode.
- What is the voltage in constant voltage mode.
- When does the charger switch to float mode.
- What is the float voltage.
How I test. I use 4 instruments typically. A DC load tester, a DC powersupply, a voltmeter and an oscilloscope. In subsequent posts you will see some pics of some of the gear. Given I am currently waiting on DA for my shed its all a but limited. Most of my test gear is still packed in boxes from the move and I only have notes from the tests I have done on the gear so far.
I will end this part here, and my next post will a very summarised version of the CTEK, followed by another post with the GSL. Just goint to go off and cook dinner now!
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