Inverter to power battery charger

[ratfink56]

I have a 100ah agm house battery and a https://www.amazon.com/gp/product/B004LWVEKS/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1. Can I run a 400w inverter off my van battery to power the charger?

Electricity makes my head hurt... tia

 

[John61CT]

There are major energy losses converting from DC to AC.

Also converting AC to DC.

So chaining them together is not efficient.

What is the ultimate source of your energy in this scenario?

 

[Watch_Cowspiracy]

I'm not sure a typical van starter battery would be capable of handeling a 400 watt inverter. That product that you linked is designed to quickly charge your starter battery in place of a jump start from another vehicle.

I would suggest getting a solenoid wired by a professional to charge your house battery off of your starter battery.

Bob Wells has a video about it on his channel.

 

[Trebor English]

I have a 100ah agm house battery and a https://www.amazon.com/gp/product/B004LWVEKS/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1. Can I run a 400w inverter off my van battery to power the charger?

Electricity makes my head hurt... tia

The van battery is not a source of charging energy.  The alternator is but only while the engine is running.  That charger is only 3.5 amps so it needs many hours to charge the house battery.  This scheme will only work if the engine is running many hours.  

A more conventional approach is to run a fat wire from the alternator through a switch to the house battery.  The switch can be manual or automatic so the two batteries are connected only while the engine is running.  The fat wire permits much more than 3.5 amps when first connected.

 

[John61CT]

And any charging from a dino-juice source needs to take into account getting back to 100% Full - which is required for House bank longevity at least a few times per week - takes over 5 hours.

You may get to 90% in a shorter commuting drive, but still need solar or shore power to continue the remaining say 4+ hours.

 

[ratfink56]

I would be driving the van while using the inverter to power the charger. Sorry I did not make that clear.

 

[highdesertranger]

how often and how long do you plan on driving? seems like you are making this complicated. a solenoid and some wire to charge off the alternator will give you better results. highdesertranger

 

[DannyB1954]

You can use an inverter to power a battery charger that charges a separate battery. I do it all the time for my laptop, telephone, and cordless power tool batteries. The thing is it is not a 1 to 1 swap. Inverters are say 80% efficient, chargers are 80% efficient, so you will be loosing 40% of your energy through heat. The battery powering the operation needs to be either much larger in capacity than the battery being charged, or it will be dead before your second battery is charged.
If you are talking about charging your starter battery from your house battery, it is easier to jump start the vehicle from the house batteries and then let the alternator do it's thing.
If you have solar panels or wind generator and your house batteries are charged, you can just put jumper cables between the house and start battery and let the Solar controller charge the Starter battery as well. If all batteries are grounded to the frame of the vehicle, you only need one wire to connect the positives.

 

[John61CT]

Sorry, but much of that is sub-optimal, overly simplified or just wrong. Maybe I'll feel up to parsing through it in detail later, but it's not relevant to where the OP is at anyway.

 

[craggers]

Sorry, but much of that is sub-optimal, overly simplified or just wrong. Maybe I'll feel up to parsing through it in detail later, but it's not relevant to where the OP is at anyway.

I'm running a 20 Amp auxillary circuit with a on off switch on the dashboard,  to power my 750 watt inverter , which in turn will power my stanley smart charger to charge the coach battery when driving.  When dry camping I plan to get a small suitcase gas generator for charging.  I also plan to get a standard 100 watt solar panel and use it as a portable device.

 

[DannyB1954]

I'm running a 20 Amp auxillary circuit with a on off switch on the dashboard,  to power my 750 watt inverter , which in turn will power my stanley smart charger to charge the coach battery when driving.  When dry camping I plan to get a small suitcase gas generator for charging.  I also plan to get a standard 100 watt solar panel and use it as a portable device.

Using a 3.5 amp charger to charge a 100 amp hour battery is going to take forever. As HDR said earlier, install a charging solenoid So that the vehicle's alternator can charge the house battery. It will charge much faster especially if you use heavy gauge wire.

 

[craggers]

Using a 3.5 amp charger to charge a 100 amp hour battery is going to take forever. As HDR said earlier, install a charging solenoid So that the vehicle's alternator can charge the house battery. It will charge much faster especially if you use heavy gauge wire.

I won't do a vehicle alternator battery isolator circuit,  my 20 amp stanley smart charger is rated at 450 watts so my 750 watt inverter should power it fine from a 12 volt dc auxillary circuit.

 

[John61CT]

OK I've been asked via PM to clarify my WTF response above.

These are just general principles, do some searching past threads then ask specific Qs for details.

Again, for the sake of efficiency, do **not** put AC inversion in between a DC charge source and a DC consumer load. You lose a lot more than 20% each step, those published efficiency specs are BS, easy to check the different scenarios with current draw meters, confirm for yourself.

While driving you may not care about efficiency, but

If your vehicle alternator is perfectly capable of charging your 12V House bank **directly** with say 100A available, why would you want to charge it more slowly?

You should never be drawing from your vehicle Starter battery, and no one sane would even think about charging Starter from House.

When drawing from your House bank, you should be **very** concerned about efficiencies.

Most screen devices and cordless tool makers have 12V "car chargers" available, and if not they aren't difficult to rig from inexpensive parts.

You should be charging all your batteries at once when a charge source is active, never just charge House and then charge secondary batts off that later.

The combining circuits between Start and House should be automatic, not manual, and forget about jumper cables except in emergencies.

No one has "wind power" in a van.

You should always run equally heavy gauge +/- wires back to the source for any serious circuits, do not rely on chassis for negative return.

Do not rely on any existing wires for heavy loads like charging, put in heavy gauge wires properly crimped and fused at the source.

A 20A circuit feeding a 750W inverter is not enough, just do the math.

And:

And any charging from a dino-juice source needs to take into account getting back to 100% Full - which is required for House bank longevity at least a few times per week - takes over 5 hours.

You may get to 90% in a shorter commuting drive, but still need solar or shore power to continue the remaining say 4+ hours.

Obviously your rig your choices, but at least understand when you're cutting corners, other people's setups may have more stringent requirements.

Laying out the details of **your** situation will help us advise you.

Let's keep this thread for OP's context, if you want to ask about any of the above wrt to your setup, best IMO to start a new thread.

 

[craggers]

OK I've been asked via PM to clarify my WTF response above.

These are just general principles, do some searching past threads then ask specific Qs for details.

Again, for the sake of efficiency, do **not** put AC inversion in between a DC charge source and a DC consumer load. You lose a lot more than 20% each step, those published efficiency specs are BS, easy to check the different scenarios with current draw meters, confirm for yourself.

While driving you may not care about efficiency, but

If your vehicle alternator is perfectly capable of charging your 12V House bank **directly** with say 100A available, why would you want to charge it more slowly?

You should never be drawing from your vehicle Starter battery, and no one sane would even think about charging Starter from House.

When drawing from your House bank, you should be **very** concerned about efficiencies.

Most screen devices and cordless tool makers have 12V "car chargers" available, and if not they aren't difficult to rig from inexpensive parts.

You should be charging all your batteries at once when a charge source is active, never just charge House and then charge secondary batts off that later.

The combining circuits between Start and House should be automatic, not manual, and forget about jumper cables except in emergencies.

No one has "wind power" in a van.

You should always run equally heavy gauge +/- wires back to the source for any serious circuits, do not rely on chassis for negative return.

Do not rely on any existing wires for heavy loads like charging, put in heavy gauge wires properly crimped and fused at the source.

A 20A circuit feeding a 750W inverter is not enough, just do the math.

And:


Obviously your rig your choices, but at least understand when you're cutting corners, other people's setups may have more stringent requirements.

Laying out the details of **your** situation will help us advise you.

Let's keep this thread for OP's context, if you want to ask about any of the above wrt to your setup, best IMO to start a new thread.

I was think'in,  Cheap RV Living  .....     I have a Cigar Lighter Circuit  and a open slot in my old savana van fuse block for another 20 amp circuit I could put in paraelle for a total of 40 amps when driving.