What it is, is an electrical bus - power flows through it this way and that.
Originally Posted by Basement Yeti
Like the bus bars in a regular house breaker panel. Power comes to the bus from the electric company, and is pulled from the bus by the loads.
Now imagine that same thing, but you connect a battery UPS to it. If the utility power is available, it supplies the loads and charges the battery in the UPS. If the utility power goes off, the UPS supplies power to the bus. The loads never know the difference.
That's how it works. The battery is connected to the bus, the inverter/charger is connected to the bus, the fuse box is connected to the bus.
Even if you use big fat wires from the inverter/charger to the battery, and then smaller wires to the fuse box, they are still going to be connected together at the battery, and thus will become a single "12v bus".
When the charger is running, it's keeping the bus at a higher voltage than the battery (higher voltage is like more pressure), so power flows into the battery until the battery gets to the same voltage and the pressure is equalized.
If you turn on a load while the battery is charging, the load will pull down the voltage of the bus, but the charger will supply power to keep the voltage up, so power flows from the charger to the bus to the load. Loads actually because at that point, the battery is also a load.
The Prosine's charger can supply up to 100a to the bus. So if you have a 30a load pulling from the bus, only 70a would be available to flow toward the battery.
Now say you connect a 150a load. The Prosine can only supply 100a, so the load pulls the bus voltage down and the charger can't hold it up, as soon as the bus voltage gets below whatever voltage the battery is at, power will then flow from the battery to the bus. The charger will supply 100a to the bus, and the battery 50a and the 150a load won't know the difference.
When the charger is off and something pulls power from the bus, the power flows from the battery to the bus since the battery is the highest voltage supply connected to the bus.
It's sort of similar to an air compressor. The pump is the charger and the tank is the battery and the air hose is the load. Whatever you use will pull down the pressure. If the pump is running when you start using your paint gun, the air will come from the pump and the tank will stay topped off. If the pump's not running, the air will come from the tank.
If you start using your 1" airhammer and it pulls more than the pump can supply, then everything the pump can supply will get used, as well as some from the tank. When you let off the trigger, the pump is still running, only now its output is flowing toward the tank.
When the Prosine is in inverter mode, it's pulling power from the bus, inverting it and supplying its 120vac outlet.
When you supply shore power, the battery charger fires up to supply power to the bus, the transfer switch moves the 120vac outlet from being connected to the inverter, to being connected to the shore power, and the inverter just sits there waiting.
The 12v loads never know the difference as long as -something- supplies voltage to the bus.
Last edited by dwh; 02-18-2011 at 06:49 AM.
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