Inverter

[Ray & Cece]

Will be traveling for 3 days with 2 overnight stops at camp Walmart, then will be in a campground. I have a 2800 watt inventor with 4 6V batteries. Last spring we did basically the same thing and killed the batteries the second night, I hade the inverter on all the time. Should I leave it off while traveling and turn it on at night to bring the refrigerator to temperature?

[Bobi, Dick and Ruby McKee]

I would think it would be just the opposite. Leave it on while traveling so the vehicle can keep the charge up and turn it off in the evening.

[TurnerFam]

if you have a generator, use it to keep the batteries charged, when/if the batteries need it(usually an AGS AutomaticGeneratorStarter, if you have it, can do this automatically) whether you are driving or are parked.

[tenbear]

I would turn the inverter off when it is not being used. The batteries should charge whenever the engine is running, whether the inverter is on or off. With the inverter, and any other unnecessary electrical loads off, there should be more power available to charge the batteries.

Most RV refrigerators run on propane and do not require 120VAC. If you have a residential refrigerator, it probably does require AC power. I don't know how long it would stay cold with the door closed and no power.

[Techn0]

Leave it on while are traveling. The alternator along with the BIRD will charge your house batteries. When you stop for the night, you can leave it on for a while. but before you go to sleep turn it off. When you get up, either run your generator or run your engine and turn the inverter back on.

I would also double check your energy draw as you may have more items running including parasitic electronic devices draining your batteries. Also, ensure you keep your batteries healthy by topping them off every month. You may want to calculate your amp hour capability of your batteries vs your requirement to ensure your batteries can handle what you are requiring of them.

[Ray & Cece]

I apologize for not giving more information. I have a Mobile Suites 5 wheel with a residential refrigerator (AC only).

[Chance]

Originally Posted by Ray & Cece

I apologize for not giving more information. I have a Mobile Suites 5 wheel with a residential refrigerator (AC only).

May also help others help you if you mention whether you have a generator, and if so, its size.

[Ray & Cece]

I do not have a generator.

[hardinkr]

Originally Posted by Ray & Cece

I do not have a generator.

I have the residential refrigerator like you but only have two 6 volt batteries and a 1500 watt inverter. We always travel with the inverter on to keep the fridge cold and when parked without shore power it stays on also for the same reason. The only time we pulled the batteries down enough to cause the inverter to shut down was once when we used the lights and vent fans for several hours to keep us cool. Since then we are careful to simply open windows, keep the fans off and use as few lights as are absolutely necessary and the batteries lasted all night. I also have two Honda 2000 watt generators that we can use if we absolutely have to watch TV and or run one AC unit or fans during the night. If we don't need the air conditioner we only run one of the generators and it will run idle all night using about one gallon of gas to keep everything charged and running.

[Chance]

If this is something you do on a regular basis, you may also want to consider solar. It's more expensive than a portable generator but may be more convenient -- may be a good match for your type of need provided you don't need to run air conditioner.

[fotofx]

The residential fridge draws the most power when it is cooling down. You should have it cooled down prior to running it off the inverter for best performance.

[here4now]

The residential fridge will also use a good bit of power during the defrost cycle, which usually occurs at night.

[hsb1993]

If stopped at a Walmart, buy a bag of ice and wrap it in a trash bag to prevent leaks. Put it in the fridge and turn off the fridge at the breaker. Fridge will stay cool and the inverter will still be available for whatever else it is wired to supply.

IMO, a 2000w inverter generator (pick your brand) in a necessity for situations like this in electric heavy rigs.

[Cummins12V98]

Spent the night at WM one time and the Frig was at normal temps in the am and we have a 1,000 watt inverter. Ran the slides in and furnace etc off the batteries with no issue.

[GeorgiaHybrid]

Don't count on your tow vehicle to provide much of a charge to your house batteries driving down the road. The 12 to 14 gauge wiring at that distance will be like having a trickle charger on the system at best. Your best bet to re-charge the batteries is either hook up every other night, use a generator when needed or a good solar system.

You can extend the run time of your batteries by flipping the breakers in the INVERTER breaker box that do not need to be on. I normally turn off everything except the fridge and can go for several days this way with just occasional use of the pump for toilet and sink water use and a little LED lighting usage.

Remember that if you opted for the large inverter system, the TV's, microwave, satellite, refrigerator and most other 120 volt AC items are wired into your inverter. Even when they are turned off, they are drawing amps from the system to be able to "quick start" when you turn them on. This parasitic draw can kill your batteries in a hurry.

Bulk charging with a 15 amp AC circuit will give you bulk rates of over 100 amps to your batteries and is much more efficient than trying a 12 volt charging circuit. That can be done by everything from a small gas generator to an onboard APU in my case mounted to the tow vehicle.

[Chance]

For less cost than solar or generator, you may be able to install a charging system off truck alternator. You can make it as simple or as sophisticated as you want. Depends on budget and skill.

If you can fully charge batteries during the day while driving, the battery bank should be able to run fridge overnight with ease.

Just another option to consider.

[GeorgiaHybrid]

Originally Posted by Chance

For less cost than solar or generator, you may be able to install a charging system off truck alternator. You can make it as simple or as sophisticated as you want. Depends on budget and skill.

If you can fully charge batteries during the day while driving, the battery bank should be able to run fridge overnight with ease.

Just another option to consider.

Chance,

Assuming you want no more than a 3% voltage drop and roughly 30 feet of wire from the alternator to the battery back (mine would be a LOT more than that) you would need at least a AWG 4 gauge wire to make this happen. that s the main reason most don't try to charge with 12 volts of DC, the voltage drop is horrendous even over short distances.

You can go with a 6 gauge wire at that same 30' distance but the voltage drop approaches 10% at that length which leaves you without much in the way of a charge as the normal 14.2 volt bulk charge rate will drop to 12.8 volts (-1.4 volts).

That is the main reason the +12 volt lines on the trailer umbilical will not do much to charge the house batteries while driving down the road.

[Chance]

Originally Posted by GeorgiaHybrid

Chance,

Assuming you want no more than a 3% voltage drop and roughly 30 feet of wire from the alternator to the battery back (mine would be a LOT more than that) you would need at least a AWG 4 gauge wire to make this happen. that s the main reason most don't try to charge with 12 volts of DC, the voltage drop is horrendous even over short distances.

You can go with a 6 gauge wire at that same 30' distance but the voltage drop approaches 10% at that length which leaves you without much in the way of a charge as the normal 14.2 volt bulk charge rate will drop to 12.8 volts (-1.4 volts).

That is the main reason the +12 volt lines on the trailer umbilical will not do much to charge the house batteries while driving down the road.

I'm not following your logic. You're implying choices are either you charge at bulk rate (however much you assumed -- guessing 60 Amps based on your numbers) or you do nothing and let the batteries run down over three days?

In a case like this, are you not actually trying to keep batteries from running completely down rather than keep them totally charged? You can always get them back to 100% later when you hook up at next campground.

This is not a steady-state problem but a transient one -- it varies with time. We have to think about what actually happens over time much like with a solar system.

When you first start out with trailer battery-bank fully charged, the battery voltage should be high enough that you wouldn't get much current. But as the refrigerator depletes battery capacity and voltage drops, the 4-gauge or 6-gauge cables would start to flow current based on voltage differential.

Any current you get during the day while driving will be that much less that comes out of batteries. If you only get 20 Amps for 8 hours that's 160 Amp-hours each day. In 3 days of driving that's nearly 500 Amp-hours. And if you look at voltage drop at 20 Amps it's not that high.

By the way, I just picked 20 Amps from alternator to trailer batteries out of thin air. It could be much higher depending on system design. As you approach the end of trip and batteries are down to 12-volts, still high enough to run inverter, the amount of current that a 30-foot-long 4-gauge battery cable will flow from 14 Volts to 12 Volts should be much more than 20 Amps. A lot more. Even at 40 feet of cable length, the amount of current should far exceed 20 Amps.


In any case, battery cable is "relatively" cheap last time I looked. You can still buy a lot of battery or welding cable for $100. Obviously you'd also need connectors, fuse, switch, etc. I'm not saying it would be the best choice for anyone, just another option to consider.

[RustyJC]

Our Mobile Suites has a residential fridge, 1500 watt inverter dedicated to the fridge, 2 each 6 volt batteries and a 220 amp alternator in the truck. We can (and have) travel 10 to 12 hours and still have plenty of battery power to run the jacks and slides. From my perspective, that's good enough for what I need it to do.

Rusty

[Chance]

Yeah, it's the 3 days in a row without shore power or generator that makes the OP's requirements a tough one to meet.

Just shows we all have very different needs. Fortunately there are often various ways to solve problems.