Inverter charging

[madjack]

...Chris, the charger in question was a 6 amp 3 stage smart charger manufactured by Vector and sold under that and the B&D brand name...I think it was around 27 bucks and change...the 100 watt inverter is probably too small, I have a 500watt inverter I paid about 20 bucks for at Sam's Club..also by Vector...I wasn't suggesting dumping Fran's C-PAP, just looking for a portable model...my step dad had one that ran offa battery pack
madjack
p.s. the converstion, was one of several we had in the couse of the weekend....

[Chris C]

We had conversations?

[SteveH]

Jack,

Chris has said:

It consumes 38 amp hrs in 8 hours of operation.

If it consumes 38 amp hours, with a 6 amp charger it would take at least 6.3 hours of driving with the inverter and charger running to recharge the teardrop battery. If you have the inverter/charger system running while the Honda is not, you may not have enough battery power left in it to start it again.

[Chris C]

Steve, Steve, are we on the same page here, m'boy? I said I'd be driving 5 to 8 hours while charging the battery and Madjack agreed that was the way to do it. Nobody ever suggested charging the trailer battery without actually driving the vehicle at highway speeds. So, are we all on the same page now?

[Chris C]

Madjack, do you think a 175 watt inverter would run the charger you mentioned?

[tdhombre]

I have a deep cycle 12v battery in the teardrop and hooked up a 110v -> 12v trickle charger to charge up while connected to "shore" power. OK for short trips but on our Mexico trip we were going to be gone longer than the battery charge would hold out. Sooooo.....

I acquired a 400w inverter to run my laptop, and boom box that does 12v, 120v, pumps up tires and jump starts engines. It has the ability to be charged either with a 110v connection or a 12v connection. Soooo......

I ran 10 gauge red/black (fused, of course) from the alternator input of the fuse block of my truck, ran them into the back of the truck box (just inside the tailgate) and hooked them into a 12v power adapter - you know - one of those cigarette lighter things. So......

Now I can plug the inverter into the truck's 12v and let the alternator charge the inverter while driving down the road. BTW, it seems to take a couple of hours or less to recharge the inverter. Then....

I figured I could do the same for the 12v battery in the teardrop so I wired up a cigarette plugin on a pigtale, matched up the red/black and wired them into the battery in the teardrop in parellel with the trickle charger. NOW.... when the teardrop needs topped off, I just plug into the source in the truck and, after an hour or so of driving, the 12v battery charged up (assuming that I can trust me voltage regulator dial in the cab).

I also have a 110v extension cord in the teardrop that I use when 110v is available. In Mexico, however, the electricity is dicey and is upward of 130v in places. So, charging it off the truck alternator was a good alternative to have.

Works for me!

One word of caution - the cigarette plugin on the teardrop is "hot" since it is wired directly to the "+" and "-" posts and can short out and drain the battery. I made an insulator out of plastic 1/2" pipe that the plug fits into to prevent that.

[GeorgeTelford]

Hi Chris


I didnt want to rush it earlier, for that amount of charge 5-8 hours driving isnt going to cut it. A definate 8 hours would do it (we are talking invertor/charger here, with a smart reg 5 would fully charge no problem, but we are getting ahead here,lets spec this right.

To specify a system that will NEVER let you down I need some specific info from you.

How many consecutive days do you want to be out for? nights?
Will you be driving every day? without fail?
How many hours ( I Know you said 5 to 8 but will that be every day you are camping?)

What other equipment do you want to power and for hour many hours?

Have you got a maximum budget in mind for the electrical system?

I can show you how to make a manual regulator that will really boost charge the system for less than $5 and your time, but you have to be the brain that moniters the charge, would you consider timing it and altering a small potentiometer to mimic a staged charger? or would you rather spend $ 85 and have it fully automatic?

[GeorgeTelford]

Hi Dave

are you talking about one of thn power source jobbies with a small onboard battery? the battery is typically 17 AH, as a back up power supply 17 ah even if fully charged aint gonna last long at all.


I hate hearing topped off, it implies that you are putting the last little bit of charge in to totally fill the battery, reality nothing could be further from the truth. A standard alternator will not get the starter battery much above 70% even if you drove all day, I could explain what happens but most people just cannot understand it.


assuming that I can trust me voltage regulator dial in the cabNo you can't, thats not what its there for.

It works for you simply because you have no great power needs, Chris needs 40-50 Ah per day minimum, way different to what you are using.

[madjack]

Madjack, do you think a 175 watt inverter would run the charger you mentioned?

Chris, I don't know the input on the charger and it is hard mounted so I can't see the plate on back to get that info...I have the manual somewhere if I can find it I will see. However, the inverter you mentioned puts out just over 1 amp (175w divided by 120v) and is still probably too small
madjack

[Chris C]

Hi Chris


I didnt want to rush it earlier, for that amount of charge 5-8 hours driving isnt going to cut it. A definate 8 hours would do it (we are talking invertor/charger here, with a smart reg 5 would fully charge no problem, but we are getting ahead here,lets spec this right.

To specify a system that will NEVER let you down I need some specific info from you.

How many consecutive days do you want to be out for? nights?
Will you be driving every day? without fail?
How many hours ( I Know you said 5 to 8 but will that be every day you are camping?)

What other equipment do you want to power and for hour many hours?

Have you got a maximum budget in mind for the electrical system?

I can show you how to make a manual regulator that will really boost charge the system for less than $5 and your time, but you have to be the brain that moniters the charge, would you consider timing it and altering a small potentiometer to mimic a staged charger? or would you rather spend $ 85 and have it fully automatic?

George, as you know, I don't even have a trailer yet, so some of your questions I can't answer difinatively. I think the longest trip I can forsee right now might be two weeks........so 13 nights in the teardrop. Probably not driving every day..........maybe every other day. And my guess would be anywhere from 3 to 8 hours on driving days. Sometimes less. Can't possibly give you a "without fail" time. Also, we've planned on trying to stop by a "sissified" campground every third of fourth day so we could hook up the AC and charge the battery and have access to bathroom facilities instead of a privacy tent. So it's really all sort of "iffy" right now. I'm not against buying an inverter to hook to my battery and running a battery charger off that..........along with connecting to AC every now and then in an RV park. Hate to put you to all the trouble to design something I really don't need. But thanks for the offer. My big question right now is how large an inverter do I need to run a 10amp, 3-stage charger?

[PaulC]

10amp X 120v = 1200 watts. If you reverse the calculation this is what you end up with. 10amp is a very flexible figure, it refers to max output at any one time not continuos output. To cover MY butt I carry a 1000w inverter with me all the time. One thing I think has been missed in all of these suggestions is how to transfer the power from the vehicle to the trailer while you are mobile. The size of cable, plugs(Andersen type) etc will also add to the overall cost. For simplicity I carry a 650w generator that has an in built single stage charger. It's only a cheapie at $98.00AUD but keeps me charged up.
Cheers
Paul.

[GeorgeTelford]

Hi Paul


Cable size is a weird one look at the nearest 3 core 13 amp mains flex and then look at three pces of 10 amp automotive cable, notice something?

Its pretty easy to transfer the amount of mains power we are talking here, either use mains cable or use the 12v that would go back to the trailer anyway and run the invertor & charger in the tear.

Using the genny, a couple of things come to mind, you would need to run the genny for hours if you are using the 12v side (oft the genny) to charge, especially the amount of power Chris needs. Using a few hundred dollar charger would speed the process up, but that would still be better if run when travelling.


Chris

I Will run the Math later but its easily doable and not that expensive (especially if you do a campsite day regularly as mentioned)

[SteveH]

Steve read the links I added above a standard alternator is not a good charger in fact it is an extremely poor charger, its a power supply thats its Job. it just happens to replace the tiny amount of charge lost when starting a vehicle battery doesnt ever get above 65-70% charged.

George,

You are probably right that an alternator is not the best charger, but I just read on the net there are an estimated 15 million new cars sold every year. That number does not include trucks, or motorcycles. I would estimate that every one of those 15 million cars has both a battery and an alternator. With the exception of parts failures, all of those 15 million batteries stay charged.

The RV industry has been charging the batteries in towed RVs with the tow vehicle alternator ever since they have been in existance. Must work.

Chris has said he needs approximately 40 AH of batteries per day, so why not just say 40 X 2 = 80 amp hour (don't want to take the battery all the way down) + another 30% ( for alternator ineffiencies) = 104 amp hour battery. I know there are batteries that big and bigger available. With just a big battery and the alternator in the vehicle, the job can be done with no other equipment. Like others on the board here, I subscibe to the KISS principle.

[Chris C]

Steve,

I'm the electrical illiterate here, so here's how I see it based on all I've read and heard:

In the first place, there are many batteries available in the amp/hr range I need. (105-120) Both in auto and in deep cycle batteries. For use in a teardrop, where one often consumes much of the reserve before recharging "fully", a deep cycle has been recommended. In fact, George has just about convinced me I need a traction battery. An automobile battery functions well as long as it stays almost "topped off", which is what the alternator does. It keeps the battery at about 70/75% most of the time. The battery thrives in an invironment of being always ready. On the other hand, a deep cycle is just that! A battery that is designed to be dragged down into it's depths before being recharged.........and it does it well...............if the correct charger is used. There are specific chargers which are to be used with those batteries............and they don't include automotive alternators.

So that's what I've been told. If I'm incorrect, would someone please straighten me out?

[SteveH]

Chris,

I agree 100% that you need a deep cycle battery, and a big one...maybe two. The alternator, however, does not know what type battery it is charging. Nor does the deep cycle battery know what is charging it. It simply puts out 13.8 to 14.2 volts and the battery accepts the amount of current it will based on it's state of charge.

The thing is, an alternator will deliver up to it's rated output for hours on end, and if that is 120 amps, so be it. The charger you are talking about is only 6 amps, but will maintain that current till the battery is peaked. With the alternator, your battery will be recharged to the point of the alternator's output voltage, much faster, assuming the wiring is of sufficent capacity.