ABM - Advanced Battery Management Exposed
In 2003 we authored a paper discussing the technology used by various manufacturers in the rectifier (AC to DC portion) and inverter (DC to AC portion) sections within UPS. At the time some manufacturers were using 1970's technology in their rectifiers and keeping mum about it. It was an issue because old rectifier technology was slow but newer and common inverter technology is fast. We referred to the old technology as turtles and the newer technology as rabbits. (Note almost all manufacturers do use rabbits today for inverters, surprisingly many still use turtles in their rectifiers.)
The rabbit inverters fed the load but also have to be fed by either a rectifier or a battery. Better manufacturing design uses rabbits as rectifiers for a perfectly matched overall system. Others still use turtle rectifiers to feed the rabbit which does not work and the result is the rabbit inverter needs feeding from both the rectifier and the battery during normal operation. Further complicating the problem with turtles was that they also have to feed (charge) the battery and their slow performance harmed batteries (technically by higher ripple currents, AC into a DC system). Think of the slow turtle as having to toss large chunks of food at a time whereas a rabbit rectifier can provide many small bite size pieces of charging food to the battery. Both may supply the same amount of food but bite size pieces are better for the battery.
Surprisingly now more than a decade after that paper some manufacturers still use turtles for rectifiers. The turtles still kill the batteries prematurely. Knowing their design is limiting battery life, these manufacturers found a marketing fix. Let's turn off battery charging as much as we can and claim it adds efficiency! To have a good marketing name they called it Advanced Battery Management.
Well, problems present them self from an engineering view.
- 1st, battery manufacturers found from warranty claim research that the concept of cyclical charging was harmful and produced sulfation and lost capacity. Cyclical charging was considered abuse!
- 2nd, the battery is virtually never fully charged nor fully available as the user would want. Perhaps their 5 minute battery drops to a minute or two of reserve time after not being charged for up to 28 days.
- 3rd, the claim of saving energy was determined to be in error too. There is no energy penalty to be saved from. Once the battery in a quality UPS is charged, the charge current drops to virtually zero as the full charge voltage is present. The energy claim was errant. In actuality the float charge system uses very little current over time but the every 4 week cyclical ABM recharge concept uses lots of current during each recharge and may in fact be less efficient a process over the long haul!
- 4th, is that the UPS design with the slow 1970s turtle rectifier is constantly seeking help from the batteries to feed the rabbit inverter. The batteries wear out prematurely when that occurs.
The odd thing is that with a bad rectifier design that damages batteries as they are charged it may be better for the battery to just turn off the charger. However with quality IGBT charging of better designed UPS systems we see batteries routinely lasting 5 or more years (at times, 7 to 9 years in our experience). Also, having battery manufacturers consider your "Advanced Battery Management" technique as abuse, producing damaging sulfation can't be good for the end user.
In summary if one wants extended battery life and performance, a UPS with an IGBT charging system is required. If one merely likes the sound of having Advanced Battery Management and is willing to pay thousands of dollars for early battery replacement then selecting an ABM system would meet that goal.