I’ve noticed when people are using generators to power a tool or appliance, they always directly plug into the generator. Then the generator is burning fuel reguardless of consumption.

How can that waste be reduced? A simple approach would be to plug your tool into a UPS (uninterruptible power supply) which is then plugged into the generator. This would help capture some of the excess energy when you are not pulling the trigger on a drill. Correct?

Possible flaw in this thinking: lead-acid batteries can only be trickle charged. So putting a battery in series only captures a small slice of the energy waste. Better than nothing, right?

I’m asking because I may need to install a generator for a whole house, and it’s not just for incidents. It will run daily in an off-grid house. So I’m trying to work out how to keep the fuel burn at a minimum and also how to fully exploit the available energy when fuel is being burnt (which should generally be during low sunlight times).

(edit) The UPS idea could backfire. IIRC, some UPSs are designed to always draw power from the battery while charging it at the same time. This is a superior design because it ensures that your appliance gets clean power that closely resembles a sine wave. UPSs that directly power the appliance from the mains and only tap the battery when mains go down have the disadvantage of sending potentially quite dirty wall power with surges and brownouts to the appliance. I think the always-use-battery design becomes self-defeating if using the UPS just to avoid generator waste. Correct? Though I’m confused because I don’t quite grasp how a lead-acid battery can charge as fast as it dissapates energy… I would think the charging would be slower than the consumption and power to eventually be lost.

  • perestroika@slrpnk.netM
    2·
    5 days ago

    Some types of solar charge controllers and battery managers have the capability to start a generator.

    Steps:

    1. charge controller: raises or lowers GPIO pin (3.3 or 5 V, current: a few milliamps)
    2. relay board (needs 5V power): amplifies the GPIO signal and actuates a small relay
    3. small relay: switches 12V power to actuate the starter relay (current: maybe 1 amp)
    4. starter relay: powers the starter motor (12V, 10+ amps)

    In an ideal world, your generator is well designed and already contains the starter relay, and the charge controller has a relay board, so you get to skip steps 1, 2 and 4 and just run a “start signal wire” between the two units.

    Now, after getting your generator started, what you care about is load. The maker of the generator should have published a chart of efficiency vs. load. Too little load, and you’re wasting energy to overcome mechanical drag. Better stop the generator. Too much load, and you’re reducing the lifetime of your generator and risking accidents. Better reduce charging current.

    Regarding UPS: a typical UPS comes with a lead acid battery that is not intended to be deep discharged repeatedly. If you end up doing that, expect dramatically reduced battery lifetimes.

    If you’re new to electric circuits, your safest bet is probably an industrially produced LiFePO4 battery bank with balancing, alarm and emergency disconnect circuits built in.

    However, if you have a manually startable generator, you better just get a big battery pack and find out what the optimal load for your generator is (note: might depend on temperature and cooling). You would want to start the generator rarely.

    P.S.

    If you can’t find a suitable product combination, this functionality can be DIY-ed with a Raspberry Pi, analog digital converter, voltage divider and cheap Chinese relays. But then it requires some electronics skills.