Decreasing amp draw of an electric element

[AZJoe]

I don't have enough room to add two more batteries and redo my entire system (everything else works great), so I decided to order an Atwood combination propane and electric 6 gallon water heater and replace the electric element with a 1000 watt version on place of the 1500 watt. I can use the electric more during the day or when I'm plugged in and gas at night if the 1000 watt is still too much for my system.

[jflorey2]

The water heater is a 120vac unit with a 1440watt heating element that is proprietary and can not be switched out with a lower wattage unit. The water heater is set up on a shore/off/inverter switch to toggle between running off of the ambilical power or off of battery backup.

You don't need AC for such an element. Consider a boost converter that will boost 12V up to (say) 60V. That would give you 1/4 the wattage (and 1/4 the draw from the battery.) You could also run it on 12V but then you'd get 14 watts, which I assume is too low for your purposes.

Arrange a relay so that when shore power is available it switches back to AC.

[Sunking]

I'm having problems trying to run a small electric watet heater with a 2000 watt pure sine wave inverter. The inverter is supplied by six 6v golf cart batteries wired in series parallel. If I switch over from shore power to run the load off of the inverter I have voltage drop and after about 45 seconds the voltage drops below 12v and the inverter powers down. .

So what is the problem? That is what you asked for using 12 volt toys trying to do real work. There are no 6-volt batteries that can supply 75 amps for any meaningful amount of time without excessive voltage sag. It would have to be a 6-volt, 250 pound. 750 AH battery.

Couple that with undersized wire that is too long and poor connections and you planned for failure. 12 volt systems should be no larger than 500 watt anything, You are asking a 12 volt toy to do the work of a 48 volt system.

Here is what will work and what you should have done to start with. Buy 2 more 6-volt gold cart batteries for a total of 8 wired in series to give you 48 volts. It will require a minimum 2000 watt solar panel, 40 amp charge controller, and a 2000 watt 48 volt Inverter.

There is nothing wrong with your batteries other than the way they are being used. You are trapped inside a 12-volt toy box. Your idea of reducing voltage is NOT GOING TO WORK.

[PNPmacnab]

You could use a transformer. Half the voltage would be 1/4 the power. Your element is 10-11 ohms. A common 24V 250W buck transformer would reduce the voltage to 100V or 1,000W to your element which the inverter might like more.

[AZJoe]

I'm having problems trying to run a small electric watet heater with a 2000 watt pure sine wave inverter. The inverter is supplied by six 6v golf cart batteries wired in series parallel. If I switch over from shore power to run the load off of the inverter I have voltage drop and after about 45 seconds the voltage drops below 12v and the inverter powers down. The batteries are rated for a 75amp draw (individually and I'm doubting they stack). I know that I'm trying to draw too many amps in a short period of time.
The water heater is a 120vac unit with a 1440watt heating element that is proprietary and can not be switched out with a lower wattage unit. The water heater is set up on a shore/off/inverter switch to toggle between running off of the ambilical power or off of battery backup.
My original solution was to install a beefy enough dimmer switch intended for indoor grow houses and I was not thrilled by the idea of the switch overheating. After I ruled that out, I decided after talking it over with my brother with HVAC/electrician/engineering background to opt for an infinite switch like you would find on an electric stove top rated for the maximum draw of the water heater. I will make a custom enclosure and wire it between the inverter and the power source selector switch. It should limit down how many amps are drawn by the wafter heater down to about half (or the best settling that makes the batteries and inverter happy) and when I switch to a regulator plugin, I get the full 1440watts.