Sunday, Nov 18, 2018 at 11:31
Also with respect you need to do some more research, on how chargers actually work and stop relying on the mistruths in the glossies. the Redarc and ctek bulk charge stage as you refer to it is nothing more than the charger protecting itself from overloading. For the 20A redarc charge it is set at a maximum of 20A for the 30A version it is 30A , for a 40A charger it will be 40A etc, the charger will maintain that current till the charge current drops below the maximum current setting allowed, it will then revert to constant voltage charging. There is nothing smart about that it is just a protection stage of the charger now called absorption stage to make the charge seem smart. Yes you can use the charger to limit the charge if needed, and some chargers allow you to set the current, but why would you buy a 40A charger then set it to 20A?
The absorption stage is a constant voltage charging stage same as used by an alternator which brings the
battery to certain stage of charge in a safe way, ie the current reduces and the voltage is held at a fixed voltage to prevent excess heat being generated in the
battery. This stage does not fully charge the
battery, it only continues till a predeterimed current level is reached. As far as I have seen the current level is the same in all settings of the redarc chargers, the only thing that changes is the max voltage, I don't see any fancy algorithms in use specific to certain chemistries. Same for ctek chargers. Same for the Enerdrive units to you can set the maximum charge voltage, the charge current and when it stops charging. Changing the chemistry only changes these settings if you call this a fancy charging algorithm then so be it. Mind you different charger manufactures have differing opinions of what are the best setting for different types of batteries, they can't even agree on that.
As above the absorption stage does not bring the
battery to full state of charge, it cant, the
battery is being forced charged at high rate, even if it contnued till the charge current dropped to zero the
battery still wouldn't be fully charged, as soon as the charge voltage reduces the batteries internal resistance will drop and it will start charging again. Your graph above clearly shows this, you can see where the SOC continues to rise once the charger switches to the float stage. As you like quoting the web here is some info of the web for you to absorb:
"Stage 2 | Absorption Charge
Smart chargers will detect voltage and resistance from the
battery prior to charging. After reading the
battery the charger determines which stage to properly charge at. Once the
battery has reached 80%* state of charge, the charger will enter the absorption stage. At this point most chargers will maintain a steady voltage, while the amperage declines. The lower current going into the
battery safely brings up the charge on the
battery without overheating it.
This stage takes more time. For instance, the last remaining 20% of the
battery takes much longer when compared to the first 20% during the bulk stage. The current continuously declines until the
battery almost reaches full capacity."
"Stage 3 | Float Charge
Some chargers enter float mode as early as 85% state of charge but others begin closer to 95%. Either way, the float stage brings the
battery all the way through and maintains the 100% state of charge. The voltage will taper down and maintain at a steady 13.2-13.4 volts, which is the maximum voltage a 12 volt
battery can hold. The current will also decrease to a point where it's considered a trickle. That's where the term "trickle charger" comes from. It's essentially the float stage where there is charge going into the
battery at all times, but only at a safe rate to ensure a full state of charge and nothing more. Most smart chargers do not turn off at this point, yet it is completely safe to leave a
battery in float mode for months to even years at a time."
The other point to note is batteries don't need three stage charging, they were and still are happily using single stage chargers ie your car
battery. It is quite slick how the manufactures of chargers have sold the limitations of their products as being beneficial for the
battery, chargers need the first two stages to work. The third float stage is really only required if your going to have the charger connected 24/7. As for the desulphation and pulse charge stages, they are gimmick stages and can be put into the same category as electronic rust protection systems.
Batteries both in the past and present have been quite happily charged using basic single stage float chargers, most large commercial installations using lead acid batteries still do it this way with
battery banks that cost hundreds of thousands of dollars.
This is not adding anything useful to the discussion, it is just the usual VSR versus DCDC charger debate which has already been done to death, if you want to spend heaps on a device that others few it any advantages them go for it.
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