Power inverter to power charger?

leenscottfl

I have tried to get an answer to my question several ways, including asking a manufacturer. No results. So if I may I will throw it out here. The question is can you use a battery charger to power up your T@B battery using a power inverter connected to the TV? I know there are many variables but is the basic premise sound? If so how many watts would be necessary to power a 20 amp charger? Nothing like putting your ignorance out there for all to see, is there?

mawebb

First "can you use a battery charger to power up your T@B battery" yes, but the power converter built into the T@B is a battery charger, so the question is why would you need to use a battery charger?
Second "using a power inverter connected to the TV" well, yes, but rather inefficient as you need DC to charge your battery so why take DC, make AC, only to make DC again with the battery charger. Simply connect the TV to the T@B and it will charge the battery. This, however, is dependent upon how your charge line is wired. On my TV the charge line to the 7 pin trailer connector is only live when my vehicle is running.
The third question "how many watts would be necessary to power a 20 amp charger" cannot be answered that precisely as it depends on the charger (efficiency), but that being said to create 20 amps of charge, which is 20x12=240 watts which is about 2.5 amps @ 110V A/C.
So there you have answers, but I am guessing that they may not answer what your ultimate question is. If you can articulate what you wish to do, I might be able to give you a more relevant answer. e.g. How can I charge my T@B battery when parked, and not hooked up to shore power?
I will be happy to help if you can please provide the scenario you wish to address.

leenscottfl

Thanks for the knowledgeable reply mawebb. Like I said there is nothing like displaying your ignorance. Mine of course. I am new to using battery power in an rv but have been led to believe that to charge using the 7 way is a slow process and I am looking for a method that is fairly quick. It seems to me that solar is not a good choice because we don't hang around the campground and I don't want to leave solar panels out for the taking. As much as I dislike generators I guess a quiet one like the Yahama 2000 will be my best bet. As an old tent camper all this is a mystery to me.

Nomad

"I don't want to leave solar panels out for the taking"
Security depends a lot on where you're camping - If I'm in a campground with a host and get to know a few of the neighbors, everyone kind of looks out for everyone else so I leave my solar setup all the time. Almost everyone has solar deployed so your's doesn't stand out like a sore thumb.
Even out boondocking, I leave it setup if there's a lot of others around and they have solar too. About the only time I pack it away is if I'm boondocking in a remote area with not many others around.
I do have a security cable I run through the legs sometimes - Not so much as a deterrent cuz they could just break a leg but it would be more obvious they were up to something.
My generator is usually sitting out also but I have a pretty heavy carbon-fiber cable attached.
I do wish Zamp and others would build security attach points into their systems though.

ChanW

From my understanding, as long as your 7-pin plug is wired as it should be, ie: with the charging conductor at a reasonably large gauge (#10 or #8 I believe is large enough), then your TV's alternator should charge your Tab's battery at its maximum recommended current.

Charging it through an AC battery charger would not be more efficient, unless the charger had some kind of optimized charging curve, which is pretty unusual in an automotive charger.

An auto alternator will 'self regulate' depending on the need of the discharged battery. It will provide high initial current, for the first minute or so, reducing the charging current as the battery develops its charge.

wizard1880

Like Chan said. I have 8 gauge wires directly from the battery to my 7-pin. It measures 14.2v by the time it reaches the t@b, and a battery at 60% charge will be at 95% by the time I get home (2 hours driving). From what I understand, many factory wired 7-pins use 12 gauge or worse, and since they shut off when the car is off, they are wired thru additional relays in the car which add even more resistance. There are many other factors too, such as alternator capacity and voltage regulator output.

mawebb

Now that the need is better described I would upgrade your TV charge line to an 8 gauge conductor to minimize the voltage drop between the TV charging system and the T@B. If you change the battery isolation to an ACR (Automatic Charging Relay) such as those made by Blue Sea Systems, you can minimize the loss of the isolator. Note that an ACR is rated for up to 120 amps which far exceeds what the actual maximum charge current will be. Note that your T@B battery connection is fused at 30 amps. Using a charger, regardless of how powerful, can only charge a lead acid battery so fast. Typical fast charging of 70% will still take up to eight hours. Note that charging can only occur when the charge voltage is several volts above the battery being charged. Upgrading your TV charge line will provide good charging but only when the TV is running. 

All being said, solar looks like it could be your best bet for battery charging when parked. 

leenscottfl

Thanks for the responses! And thanks to all who make this forum possible. As a first time RV'er I have found answers to questions I didn't even know to ask. Yeah I do believe solar is in my near future. I guess nothing is easy. Now comes the task of choosing who to go with. Fortunately there are volumes of posts addressing that project. Thanks again guys.

Michigan_Mike

One thing missing here or that you haven't given us is what your power needs and consumption will be or require in your T@B unit.  There are various ways to supplement your power and you might even look at adding an additional battery or a larger battery to your T@B.  You could add a couple of AGM batteries inside your trailer (in a bench area) and depending on what you run in the T@B, this would allow you added power.  And in conjunction with a solar panel you could charge both batteries.  The AGM batteries are sealed units and do not give off any gas vapors as wet cell batteries do.  I had a friend who converted over to the AGM batteries and he built a slide rail drawer into a bench and could easily access both batteries when needed.  

The real issue or question here and that you need to ask yourself is "how often will you be boon-docking and off the grid?"  Many folks ask these questions on both forums (how can I charge up my battery, etc.) and many seldom camp away from shore power.  If you will be camping remotely the majority of the time you need to consider the above.  But for short duration periods (e.g., an over night or one day camping stop) you can probably survive without an additional battery or even solar.  Solar isn't cheap and many individuals buy the panels and never use them enough to justify the investment.  But on the flip side if you do end up considering a solar panel they do make the flexible panels that can be mounted flush to the surface of the trailer and allow you to charge continuously and without having to set up a portable panel.  

The more you travel and camp you will develop an energy usage pattern and have a better feel as to what your actual needs and requirements will be over time.  You will also figure out ways to conserve power and balance out your consumption whether it be by charging the battery via the tow vehicle while traveling, supplementing your usage via a solar panel or via a small generator.  Generators are handy, but also require fuel and carrying a gas can around or propane.  As far as safely securing a solar panel, I use a cable on mine and lock it to either my trailer or a nearby tree, etc.  The bottom line here is that if someone wants something bad enough they are going to find a means to take it.  And as noted, most individuals you camp with are honest and will look after your camp site while you are away if you take a few moments to meet people, talk to them, etc.  I leave my 80 watt Zamp portable panel out when I am away and have never had any issues.   

leenscottfl

Thanks Mike. We typically like to camp in cooler weather to avoid the crowds. We rarely go out for under 3 weeks and up to 3 months. we have always happily camped in tents and plan to use our T@B as a hard sided tent, cooking and spending our waking hours outside. Since we typically stay in one place 3-4 days so with our lifestyle I don't think we will have any real power issues. Moving day is recharge day. And if we do run out of juice we know how to live without it. BTW I ordered a digital readout meter like I think it was you who posted a pic of to help me keep up with what my status is. Having said that I will still probably get a Zamp. You use an 80 watt but 120 is recommended. I guess you find your 80 adequate?

Michigan_Mike

I do use an 80 watt Zamp and power up my trailer lights, ARB refrigerator, CPAP, charge up my iPhone/blue-tooth speaker and TV.  If you plan to add a battery down the road you might want to upgrade to the 120 watt panel, but you'll need to calculate your energy usage or figure out what your bare bones electrical needs will be.  A solar panel really does nothing more than charge up batteries and the larger unit means that it will charge faster than the smaller panel is all.  I have had my 80 watt Zamp panel for around 4 years now and recently upgraded to their enhanced solar charge controller and noticed that it made a big difference in my charge rate.  I have been very happy with the Zamp panel and the ease of use, along with the portability factor.  It goes wherever my trailer goes and has been a plus in supplementing my electrical needs and usage therein.