On boats, most high draw devices like fridges for example have some sort of cutoff device that prevents the battery being drained like that. When the background voltage drops to a given level...usually 10.5 volts; the device switches off. I've never bothered with the Pis, because their draw is minimal compared to the fridge and freezer...However; I found a link about the subject which you might find interestingI read about the comparison. If the battery is 12 volt and the output is 5 volt, surely the regulator could let the battery run down to almost nothing before the voltage drops below what could be converted to 5 volts. Probably about 7 volts.
The actual power output to the devices is less than 2 * 5 volts * 3 amps. The Pi 5 runs happily on a Pi 4 3 amp supply when there is no NVME or USB disk plugged in. Lets say 30 watts. Before conversion, 12 volts by 3 amps. The specs for both batteries say more than 6 amps is easy. At what point would they fail to the point where they could not deliver 3 amps?
And recharges? SLA at 500 * once per week is more than I need. I can see the point of Lithium 3500 recharges when it is once per day in my irrigation system.
http://www.reuk.co.uk/wordpress/electri ... ith-ne555/
However; as you say for your needs you might be fine just charging it once a week and hoping for the best...maybe twice to be sure...The important thing is to let a 12v lead acid battery drop below 10.5v.
Statistics: Posted by kip_the_elder — Mon Jul 07, 2025 9:40 am