Trying to figure out a power system for this years ridiculous Burning Man project, wondering if you guys might be able to offer some thoughts.
I have a current draw for my piece of somewhere between 2 and 6 amps at 12v. (1.8amps of that is LEDs through a 5v regulator, the other is stepper motor draw so 3amps when engaged and 0 when off hence the wide range).
I have a generator which I can use to power the piece, but its tank only lasts about 8hrs and I’d like the piece to run day and night if possible. Now I could just get off my ass and fill it up 3 times a day, but that would be unpleasant, so I’m considering the following setup.
Generator -> 15A 12v Battery Charger -> 115ah Deep Cycle battery -> 30ft of 12awg speaker wire -> into the piece, 12v tapped directly for steppers, 5v 10A regulator for everything else (input range of 12-24v for the regulator so it should be ok when the charger kicks up the voltage).
That way when the generator runs out of the fuel the battery should be able to keep me going for a good few hours and I can fill up twice a day rather than 3 times.
Is there any fault in this logic? Anyone done this sort of thing before?
Exactly, pricey…$189, 3 batteries at $130 each…gets expensive, especially when we already have a nice little 1kw honda generator. And honestly I’ve seen 45w solar cells not achieve any substantial charge on the playa. Without lots of maintenance to keep the panels clean of dust they are considerably reduced in efficiency out there.
I use an Iota DLS-30 30 amp charger for deep cycle. Would be twice as quick as the 15 amp if you want to run the generator less. Iota seems to be the best bang for the buck in fully “smart” chargers, and have higher amperage models too.
You waited until now to design your power system? Eep.
What do you know about deep cycle batteries? Do you know not to let them discharge past 70-80% to avoid damaging the plates? Do you know the relationship between charge/discharge rate and energy output for your particular battery? If you don’t, you’ll be doing a lot of guesswork as to how long your battery will last.
A better option might be to just put a jerry can on a stand, cut a hole in the fuel cap for the generator, and run a hose between the jerry can and the fuel cap… Instant “extended fuel tank”.
Yep… Last minute with almost everything sadly. As you say I can just use the gennie and it solves all the problems which is why the power was the last thing for me to solve.
I did not know that about deep cycle batteries. I thought they supported much lower discharge levels?
Batteries can easily be discharged below 100% DoD (Depth of Discharge), and doing so will damage them. Many lithium cells will contain overdischarge protection circuits, but lead batteries with this feature generally aren’t available. Discharging to 100% will shorten the life of the battery compared with discharging to 50% or 30% (see the charts on your battery spec sheet to understand this relationship). For the week of Burning Man you could probably get away with 100% DoD, but the battery won’t be very healthy afterward and it’ll probably just need to be recycled straight away.
Discharging past 100% DoD is very possible without some kind of undervoltage lockout, and will definitely damage the battery – the metal plates will dissolve into the acid and precipitate as dust in the bottom of the cell.
If you’re turning 12 volts into 5 using a linear regulator, at 1.8 amps, more than half of the power is lost as heat in the regulator. Assuming the motors aren’t active much of the time, replacing that regulator with an efficient step-down converter should roughly double your battery run-time… or cut your battery size requirement in half.
