AC charging a tow vehicle while driving

[wb9wb]

My question is more about safety.

PROBLEM :

I have found trying to charge a house battery (deep cycle/Marine) using the vehicle's alternator and an isolation transformer to be less than ideal. In a nutshell the alternator sees both batteries hooked in parallel as one battery. However they are different. One is meant to be slowly discharged and the starting battery quickly discharged. So the alternator doesn't deliver the proper amount of juice to the batteries because it sees the starting battery as being full.
Video explaining the problem ()


CURRENT SETUP :
I have solved this problem (see above) "cheaply" but running the battery to a 120AC inverter, then a trickle charger (https://www.batteryminders.com/1510-12-volt-maintenance-charger-desfulator-with-warranty) , and the 12VDC output of the trickle charger to the house battery inside my Jeep Wrangler. This model trickle charger hits the house battery with a higher voltage to wake it up and accept the charge much better than a straight DC charge from the battery isolator. Once the battery is topped off, the trickle charger continues to desulfate the battery. it seems to charge it in a fraction of the time that the DC method does, and doesn't really cost much.

FUTURE:
I'm wanting to get an off road trailer with solar, and battery setup on it, moving the house battery(s) from the Jeep to the trailer. I want to charge while driving using the same AC method as I do with currently. AC makes the trip/distance much better than DC with much less loss and cost in wire gauge. The AC inverter source will be treated like shore power while driving

QUESTION :
This is a safety question. AC can be deadly, keeping this in mind. Hooking up a run (25' 10/3 extension cord) from the Jeep to the trailer, securing it, breakers/fuse/GFCI etc. ,

Can anybody see a problem with this while driving?

thanks in advance.

 

[shade]

The charger you linked puts out 1.5A, and would take a very long time to charge even a modest capacity house battery once it was used as most people would.

Victron just released a product that would allow you to start from scratch with a much better alternator charge source for your house battery.

New Product: Orion-Tr Smart DC-DC charger - Victron Energy

The new Orion-Tr Smart DC-DC charger is designed for use in dual battery systems in vehicles or boats, where the (smart) alternator and the start battery are used to charge the service battery. The model range is suitable for 12V or 24V systems, and both lead acid and lithium batteries. Why do...

www.victronenergy.com

 

[luthj]

Any description or video that uses the word "Juice" is generally suspect.

The issue is that most alernators do not ouput much above 13.9V, if that. This is unsuitable for charging deeply cycled lead batteries. In addition, diode isolators will drop this another half a volt, making almost no charging. Relays work better with minimal voltage drop, but 13.9V is still too low. Add 20ft+ of wiring to charge a towed vehicle, and the charge current is next to nothing.

A fix is to use a DC-DC charger, and beefy wiring to keep voltage drops down. The DC-DC charger will take 13.X volts from the alternator, and boost it up to 14.X (or whatever its set to) for charging the house battery. By locating the charger near the battery to be charged, you can eliminate the impact of wiring voltage drops (within reason). There are several options on the market, and a 20A unit is a reasonable choice.

 

[dwh]

In a nutshell the alternator sees both batteries hooked in parallel as one battery. However they are different. One is meant to be slowly discharged and the starting battery quickly discharged. So the alternator doesn't deliver the proper amount of juice to the batteries because it sees the starting battery as being full.

That...is a load of hogwash.

The voltage regulator activates the alternator field coil as needed to maintain a specific voltage. The batteries each individually suck up however much power they can at that voltage and each battery's state of charge.

 

[wb9wb]

The charger you linked puts out 1.5A, and would take a very long time to charge even a modest capacity house battery once it was used as most people would.

Victron just released a product that would allow you to start from scratch with a much better alternator charge source for your house battery.

View attachment 545101

New Product: Orion-Tr Smart DC-DC charger - Victron Energy

The new Orion-Tr Smart DC-DC charger is designed for use in dual battery systems in vehicles or boats, where the (smart) alternator and the start battery are used to charge the service battery. The model range is suitable for 12V or 24V systems, and both lead acid and lithium batteries. Why do...

www.victronenergy.com

Thanks for the response. I will check it out. My only real concern is a low voltage DC run of 30 feet won't be very efficient. My current setup is only a few feet, but converting it to a high voltage AC run means little loss. I have a 100ah house battery and it tops off after only an hour on the charger. Granted I haven't discharged it deeply either.

I will do some more research on this product, thanks again for posting.

 

[wb9wb]

That...is a load of hogwash.

The voltage regulator activates the alternator field coil as needed to maintain a specific voltage. The batteries each individually suck up however much power they can at that voltage and each battery's state of charge.

So your are saying that Andrew White (in the video ) is wrong and there is another reason that my DC charging using a dual setup / battery isolated failed to maintain a proper charge during my 3,000+ mile trip this summer? Each day the battery voltage dropped, 13.2, to 12.9, to 12.1 towards the end.

please advise

 

[shade]

Thanks for the response. I will check it out. My only real concern is a low voltage DC run of 30 feet won't be very efficient. My current setup is only a few feet, but converting it to a high voltage AC run means little loss. I have a 100ah house battery and it tops off after only an hour on the charger. Granted I haven't discharged it deeply either.

I will do some more research on this product, thanks again for posting.

30' of copper 2AWG would only yield 2.41% voltage drop.

Voltage Drop Calculator

Voltage drop calculator to choose what size wire or cable based on amps, distance and voltage. Marine wire cable amperage and ABYC allowable amps per cable gauge.

www.genuinedealz.com

 

[luthj]

Voltage drop matters less with a properly installed DC-DC. Even at 10% drop (13.9-1.39 = 12.5) most will continue to work properly (some will need a ignition trigger as opposed to a high/charge voltage trigger). That 10% efficiency drop plus about 10-20% in the charger will be the same or less than the inverter-charger approach.

 

[wb9wb]

I apologize for using the slang "Juice" What you described is exactly what I have experienced. Little to no charging at about 13 Volts from the dual battery isolator This is with only about 5 feet of 1/0 AWG. I have no intention of trying to run 25 feet of this to a trailer using DC. My new setup using AC trickle charger setup (described above) works fine.

My original question was about the safety.

 

[wb9wb]

the charger I'm using pushes out about 14.4 volts initially then backs off once the battery becomes charged.

 

[luthj]

No reason to apologize, mostly referring to youtube videos that confuse the subject.

As far as safety, you need to use a properly protected wire run. It MUST be color coded different than the other wires in the vehicles. Ideally marked at both ends (120VAC). Do not use solid wire, you must use stranded in my view.

You must use a fuse or circuit breaker near the inverter/source.

There is no reason to ground this type of system, so the neutral can remain floating from the chassis.

If you will be using this setup with plugs that may get wet, an ELCI style breaker may be called for.

 

[shade]

I have a 100ah house battery and it tops off after only an hour on the charger. Granted I haven't discharged it deeply either.

If that's true, you've only taken 1.5Ah out of the battery. Unless you're only charging cell phones from it, I have a suspicion that the house battery isn't being fully charged.

 

[wb9wb]

No reason to apologize, mostly referring to youtube videos that confuse the subject.

As far as safety, you need to use a properly protected wire run. It MUST be color coded different than the other wires in the vehicles. Ideally marked at both ends (120VAC). Do not use solid wire, you must use stranded in my view.

You must use a fuse or circuit breaker near the inverter/source.

There is no reason to ground this type of system, so the neutral can remain floating from the chassis.

thank you. this is exactly what I was thinking about doing.

 

[shade]

http://www.genuinedealz.com/ - Very good prices on high quality wire.

 

[wb9wb]

If that's true, you've only taken 1.5Ah out of the battery. Unless you're only charging cell phones from it, I have a suspicion that the house battery isn't being fully charged.

I mainly use it while camping with a CPAP. Which draws about 1ah. Once the trailer is configured I will end up drawing more amps but will also add batteries and perhaps an 8AMP charger from the same company (provided the inverter can handle it).

Its the AC charging a tow vehicle will driving concept I was worried about. The actual AC charging while driving (Jeep) works fine.