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January 2004  Battery management systems are roughly broken into two categories:
Battery MonitorsBattery monitors are very simple in the data collected, but can be quite complex in how the data is displayed to the driver. The data that is collected is typically:
Battery BalancersSince one or more batteries in a series string of batteries can get lower than the other batteries, it is important to ensure this weaker battery get extra charging. This will ensure logner life of the pack, as the weaker battery will drag down the life of the other batteries and kill the pack early. Battery balancers, a.k.a. equalizers attempt to adjust the charge going into the batteries. There are several types of battery balancers, each with their own technique: Shunt Type BalancerShunt type balancers go on each battery. If the voltage gets too high, the shunt activates and directs the current through a load to the next battery. Pair BalancersA pair balancer goes between each two batteries of the pack (so if you have 12 batteries, you need 6+1 balancers). A pair balancer works by checking the state of charge of its two batteries, and directing more charge to the battery than is lower. When all these are connected in a big string, the charger will eventually be shuttled along to the weakest battery. Problem with these chargers is with long battery strings, if the end battery is low, it will require each balancer to detect the condition, and pass the charge on through the series. Some have reported that the end batteries never get enough charge. Central ChargersCentral chargers detect when one battery in the pack is too low, and using a small charger will suppliment the weak battery. It continuously montitors the state of each battery and directs charge where needed. Commercial Battery BalancersPowerCheq Battery EqualizerThese are small units which are connected to each pair of batteries to equalize the batteries continuously. Web Site Zivan Battery "Smoother"BatOpt battery equalizerWeb SiteRuddman RegulatorsEd Ang's Battery RegulatorsWeb SiteAC Electric VehiclesWeb SiteLee Hart's Battery BalancerLee Hart's Shunt Type Battery BalancerHere is one possibility [for a shunt type battery balancer - ed]. Strangely enough, it is currently in my own EV, since I sold its Balancer to Rick Woodbury. Each battery has a regulator which consists of Solder a zener diode into each ring terminal where the wire normally goes. Solder a 6" piece of wire to the other end of the zener diode. Solder the flashlight bulb between the free ends of these two wires. Now you have the two zeners and flashlight bulb all wired in series. Fill the space between the zener and ring terminal with epoxy glue. Likewise, dunk the bulb and its wires in epoxy glue. This makes everything waterproof and acid proof, and helps conduct heat. The zeners get their heatsinking from the large ring terminals and battery posts they are bolted to. Put one of these circuits across every 12v battery. If the charging voltage exceeds about 13.6v, the zeners begin to conduct and the lamp lights. At about 15v, the lamp is fully lit and is bypassing about 0.5 amps. Use a photocell to detect the light being produced. When any of these battery regulators lights, the photocell sees it and either switches the charger off, or to a low-current trickle charge or float voltage setting. Badicheq?? BattPro?? References |