Inverter charging

[GeorgeTelford]

Hi Chip

a solar panel that will actually do any good is expensive and still unreliable.

I have not got the calculations with me (I am at a clients) but it was something like 1/2 hr with a genny (or running the engine as above) exceeded a whole days solar charging from an 80watt panel. (that was assuming a perfect Australian day for the panel.

[Chris C]

Chris why not look into a good solar powered charger that tops off ya battery during the day,,

Chip,

90% of the kind of camping I like to do is waaaaaay back in the trees where it's really pretty dark. A solar panel would be useless back in the forests. If I camped in RV parks where there was a lot of sunlight that would be fine...........but then I'd have AC electricity and not need any of this. Until I can afford a generator, I'll just run a battery charger off an inverter hooked into my cigarette lighter while I drive from one campsite to the next. I don't see why it won't work.

[mikeschn]

How long would it take to recharge your teardrop battery if you just started your car every morning and idled it?

Mike...

[Chris C]

I don't know.

[mikeschn]

Based on Q's response here:
http://tnttt.com/viewto ... 1967#51967

I looked up the Honda 1000eu on ebay. It seems the dc output is 8.3 amps.

So if you only used up 16 amps overnight, that generator would top off your battery in 2 hours.

So I wonder what the dc output of a car alternator is...

Mike...

[Chris C]

Okay, here's my actual situation:

I'll be running a C-Pap machine every night. It consumes 38 amp hrs in 8 hours of operation. I plan on having a deep cycle battery of approximately 105-120 amp hrs. As I understand it, it harms a deep cycle battery to be taken down past 50% very frequently. I'll have all the other "standard" DC items onboard, i.e. galley lights and interior lights. So I'll probably not be able to just idle the Honda for a little while to replace the loss. Seems to me if I'm going to be in camp for several days I'll really need a generator or second battery. But if I'm getting up each morning and moving on...........which is pretty much what I'm planning on for our first big trip this fall...........the Honda battery-to-inverter-to-battery charger-to-battery might be the way to go. That way I'll have anywhere from 5 to 8 hours of driving before using the trailer battery again.

[sdtripper2]

So I wonder what the dc output of a car alternator is...

Mike...

The alternator produces electricity and delivers this electricity to the battery and maintains a full charge at all times. If the voltage produced by the alternator goes above 13.5 - 14.5 volts, the battery will be ruined very quickly. It's the job of the voltage regulator to keep the output voltage between the 13.5 - 14.5 volt range.

Basic discription of the Charging system.

[SteveH]

So I wonder what the dc output of a car alternator is...

Mike,

It depends on the alternator, and the speed you are running the engine, but it is regulated at about 13.8 volts, and the current capacity ranges from about 60 to as much as 120 amps. Again, depends on the alternator...not all are the same, and none will put out rated current at idle speed.

[Chris C]

So, Steve, it seems that running a charger off an inverter from the Honda battery would deliver a more constant charge for the trailer battery, right?

[SteveH]

Chris,

Generally speaking, maybe ....the problems is as you remember from school, you cannot create nor distroy energy. Which means, considering no losses, the same amount of energy you put in the trailer battery will have to come from the Honda battery. First thing is you are discharging one to charge the other. Second, all electronic devises have inefficencies (read losses), so considering the inefficencies of the inverter and also the charger, you will essentially be wasting battery power. Even if you use the car's alternator to charge the battery, the ineffiency is running that realtively large engine (large for use as a generator) to charge the trailer battery. Charging with the alternator is only efficent if you are going to be going somewhere with the car anyway, and the alternator will charge the battery much faster than most any charger you will want to install or carry with you camping. Hope all this makes sence.

[Chris C]

But if I'm getting up each morning and moving on...........which is pretty much what I'm planning on for our first big trip this fall...........the Honda battery-to-inverter-to-battery charger-to-battery might be the way to go. That way I'll have anywhere from 5 to 8 hours of driving before using the trailer battery again.

Which is exactly what I mentioned I would be doing.

Yes, your comments make sense, but, as I mentioned previousely, I've had personal experience with what an automobile alternator does to a deep cycle battery........................and after replacing 3 in a 5 year period, I'm convinced automobile alternaters are for starting batteries, not deep cycle.

[GeorgeTelford]

How long would it take to recharge your teardrop battery if you just started your car every morning and idled it?

Mike...

Hi Mike

A car alternator without a smart regulator will never recharge the battery, see the links above re smart regulators look at the graph for alterantor only charging.

Steve H

Not if the alternator is powering the vehicle starter battery once the engine is running the starter does nothing.

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.

Regarding output look at the graphs again, as a batteries internal resistance changes the charge current drops rapidly, it rarely puts out more than a few amps except in the minute after starting.

All this is very hard to explain to electrical techies (I have even had to physically demonstrate to some to prove all this happens)

Hi sdtripper2

Thats all OK for vehicle system, not that good for a leisure (or deep cycle) situation, the system as described works for starter batteries that dont ever need to be fully charged and only ever supply a tiny ah for starting the vehicle. And note that that regulates the Voltage the ampage is only controled by thevariable resistance of the battery drawing the current.


Chris C

for CPap and that amount of current draw we need to design a better system.

I am about to go out, but I will sort exactly what you need later and I will guarantee that what I say will work exactly as I say it will.

and after replacing 3 in a 5 year period, I'm convinced automobile alternaters are for starting batteries, not deep cycle.

More evidence that what I say is right, if every ones got a few months I can explain every stage of what goes on in these systems

If you want, we should start a seperate thread just to discuss the system you need

[Chris C]

Sounds as if this is going to be complicated beyond my $ means!!! Why can't anything be easy????????

[madjack]

Chris, as you may recall we had a similar converstion about battery charging at Beaver's Bend...you saw the little smart charger we were using in the Alligator Tear...it was under 30 bucks at Wally World, combined with an inexpensive inverter you can charge the battery up to full for under 50 bucks doing as you suggested while driving...just another 2cents wortha thought on the matter...if you wanna upgrade that system then get the Deltrans unit which will probably hold up better but cost twice as much as the little B&D/Vector from WallyWorld
madjack
p.s. I would also investigate other types/brands of C-PAP machines for one that was not such a power hog

[Chris C]

Thanks, Madjack. Sounds like a plan. WalMart Smart charger, huh? No, I don't remember the conversation, but then I've slept since then. Will a 100 watt inverter run it, I wonder? As far as the C-Pap, it's my girlfriend's and she's not going to dump a brand new and very expensive machine and change brands so our trips will be more convenient. This is the one her doctor recommended for her specific symptoms and................well, I guess I'm stuck with it!