High Amperage Drain on Lead Acid Batteries 1700 watt kettle vs 400 watt coffee maker

With a 478 amp hour 12 VDC flooded lead acid battery bank, if I brew 1700 ml of coffee, this is the percentage of my battery drained for the same amount of coffee:

1700 Watt electric kettle: 11.5255% drained
400 watt: 3.720951% drained

I'm posting this because on a separate forum I am on, I am being lead to me not needing to go up to 24 VDC to power a 2000 watt inverter with a 478 amp hour bank, and the batteries are strong enough to push a 3000 watt inverter. I'm not really like what I'm seeing when I run the numbers. I'm sure there's errors in the formulas, but its close enough to get the point across.

I have been curious how much better it is on an inverter system to run a single cup coffee maker to make an equivalent amount of coffee from 1700 watt kettle. I was pretty surprised at how much keeping the wattages low with the single cup saves you versus just doing it all at once with the electric kettle.

My system I'm building has flooded lead acid batteries with a C20 of 478 amp hours so I calculated how the wattage devices used up a battery quicker than the lower watt devices. The 1700 watt kettle used 141 amps when turned on, and that uses stored energy up at the neat C1 Rate, so the battery could produce 143 amps. The 400 watt coffee maker used energy at 33 amps, or the C12 rate of 430 amps or 35.85 amps per hour. So to determine the percentage of battery use, I divided amp hours used by total battery amp capacity. Then what I did with that percentage of battery used is multiply that percentage of the C20 rate, to see how much was pulled out at that rate. With my 36 amps I expect in ideal conditions with my system, I used this to see how long it would take to charge the battery.

For the 1700 watt kettle, it will make 1.7 liters of boiled water that you then add instant water to. To make the same amount of coffee, it's 7.2 cups of coffee.

Single use coffee maker
478 C20 Rate
400 Watts of coffee maker
12 VDC Batteries
33.33333333 Amps for coffee pot
12 Hour Rate (C rating)
430.2 Total Amps at the C12 Rate
35.85 Amps per hour at the C12 rate
4 Minutes to brew a cup
236 ml per cup
1700 electric kettle ML
7.203389831 # of cups to kettle
28.81355932 # of minutes to brew 7.20338983050847 cups
16.00753296 Amps hours used at C12 Rate
17.78614773 Equivalent Amp Hours at C20 Rate
3.720951408 % of Battery used
36 Charging Amps
0.494059659 Hours to recharge

1700 Watt 1700 ml Electric Kettle Coffee Maker
478 C20 Rate
1700 Watt electric kettle
12 VDC Batteries
141.6666667 Amps for coffee pot
1 Hour Rate (C rating)
143.4 Total Amps at the C1 Rate
143.4 Amps per hour at the C1 rate
7 Minutes to brew a cup
236 ml per cup
1700 electric kettle ML
1 # Kettles brewed
7 # of minutes to brew 1 cups
16.52777778 Amps hours used at C12 Rate
55.09259259 Equivalent Amp Hours at C20 Rate
11.52564699 % of Battery used
36 Charging Amps
1.530349794 Hours to recharge

The table below I got from @sunking ‘s https://www.solarpaneltalk.com/forum...teries-and-you

Discharge Rate Coefficient
C Hour Coef Ttll Amps
1 Hour 0.3 143.4
2 Hour 0.5 239
3 hour 0.6 286.8
4 hour 0.65 310.7
5 hour 0.7 334.6
6 hour 0.75 358.5
8 hour 0.8 382.4
10 hour 0.85 406.3
12 hour 0.9 430.2
16 hour 0.95 454.1
20 hour 1 478
24 hour 1.05 501.9
36 hour 1.1 525.8
72 hour 1.25 597.5
100 hr 1.3 621.4

Some other issues, on the negative side, there is no loss accounted for and what could make this better than posted is if the solar panels are producing a lot of charging amps, the batteries won't drain as much.