Automatic generator stop-start

[Capt. Ray]

I have a small 3.5kW diesel genset with remote panel that has preheat, start and stop buttons.

I would like to build or buy an AGS that will start the generator automatically when 24v House bank hits 50% State-of-Charge (SoC) and stops the generator when the batteries are charged within 80% SoC. If I can't get that sophisticated, programmable voltage setting would do.

I am not advocating this for extended periods away from the ship, but my batteries and solar don't quite allow me to run refrigeration all night, the refrigeration is crude and can not be set to power down on low voltage. Sometimes I wake up in the morning and find the batteries are too low. I have already gone as far as I can with extra insulation etc.

I don't have enough money right now to buy more batteries or solar panels, so if I can rig up a little $50 - $100 commercially available AGS that has programmable SoC or voltage sensing and has three relaty outputs (Preheat, Start and Stop), that would be perfect.

Have any of you tried this?

[skipperpete]

Putting a low voltage disconnect relay in the refrigeration power circuit might be an easier option, then in the morning you could manually start the genset to charge the batteries. I intensely dislike autostart gensets, they can be very risky things to live with, the upside is that they sometimesdon’t have long service lives. Folks get so used to autostart they neglect the simple procedure of dipping the oil, checking the coolant and belts and visually witnessing the exhaust water flow and instead rely on the auto shutdown to prompt checking the oil level etc…. Not a good idea.
3.5kva seems a bit small for a 97’ yacht.

[Capt. Ray]

None of your suggestions work for me. I know what I need for my refrigeration and the power of the generator suits my usage just fine, I don't need your criticism. Why waste your time making suggestions that do not address my question?

[Jammer]

https://www.donrowe.com/Magnum-Energ...me-ags-s-r.htm

Supports preheat and should do everything you want. They're over your budget a little at $229.

[skipperpete]

Originally Posted by Capt. Ray

None of your suggestions work for me. I know what I need for my refrigeration and the power of the generator suits my usage just fine, I don't need your criticism. Why waste your time making suggestions that do not address my question?

Have a nice day Captain Ray, hope you find the answer to your question.

[SailingHarmonie]

I don’t have time to design a circuit for you, but I can assure you that if you can sort the hardware and programming issues, the concept works. Many batteries monitors have a programmable relay you could use to initiate the process, maybe feeder a series of simple time delay relays to operate the cycles needed.

Our generator has been on auto start for years. The only time I manually start it is for maintenance or testing. Our generator’s controller is designed to accept a simple relay closure to trigger its external run function, and that is done by our Victron Cerbo.

I found that starting the generator worked fine with a SOC trigger, but that didn’t do well to stop it. Instead I stop it when the current acceptance drops to a specific value.