Charging batt while boondocking

[chopshop]

We will be boondocking this entire season. I have a honda 1k genny that I plan to use to charge the battery.

Question:
If I plan to use an off-board charger, will I need to disconnect the TT terminals from the battery prior to connecting the off-board charger to the battery?

[rwilley]

I never do.

[Terry]

I don't see where there would be a problem unless the battery is totally dead then I would disconnect first.

[David472]

To add to what Terry has said, by disconnecting the load from the TT first, you would have a faster charge rate (depends on how much TT load is there). If you don't care about the rate then don't bother to disconnect.

[Terry]

I should have elaborated on my post as to why I recommended disconnecting if the battery was low. Most battery chargers do not put out clean power - they generally have a rectifier or diode bridge which inverts the negative portion of the AC sine wave. When you charge a good battery, it will act like a big capacitor and smooth out the power. If you throw it on a dead battery you risk throwing bad power into the TT and possible damage to the electronics.

Illustration --

http://www.industrial-electronics.com/image/four-diode-full-wave%20bridge-rectifier_7-3.jpg

[clutch]

We used a similar generator , a Honda 650, and just plugged it into the trailer. We ran a tank a day through the generator, about 1 liter, and we always had power. We did that for right at 13 years with no problems.

[David472]

Terry,
There is a difference between a discharged battery, and a failed battery. A discharged battery will still filter any ripple in the DC voltage.

[chopshop]

We used a similar generator , a Honda 650, and just plugged it into the trailer. We ran a tank a day through the generator, about 1 liter, and we always had power. We did that for right at 13 years with no problems.

That was an option I was thinking about, but if I wanted to charge it faster, I would have to use an "off-board" charger, at least that is what I'm thinking. Thank you all for the information, once again, I am able to learn more from this site!:D

[Terry]

Terry,
There is a difference between a discharged battery, and a failed battery. A discharged battery will still filter any ripple in the DC voltage.

I was thinking of a battery where someone left it hooked up and it ran down to nothing. While it would lessen the dirty power but you would still have some ripple for a short time.

[cablerum]

That was an option I was thinking about, but if I wanted to charge it faster, I would have to use an "off-board" charger, at least that is what I'm thinking. Thank you all for the information, once again, I am able to learn more from this site!:D

If your trailer has a dual battery system you have another option. When you wire batteries parallel to maintain 12v you wire positive to positive, negative to negative and connect the TT to one of the 2 batteries. You have the option of running a positive cable from both batteries individually to the positive cable of the TT and the same with the negative. You can put an inline switch or fuse on each positive and negative cable from both batteries. This way you can isolate one battery from the TT while charging and still have one battery connected to run things. You will just have to charge your batteries separately. This way any concerns you have will be met and you don't have to shut things down while charging. But you would need a dual battery system.

If you are unsure how to do this yourself involve a professional cause wiring this wrong could damage things.

[David472]

I was thinking of a battery where someone left it hooked up and it ran down to nothing. While it would lessen the dirty power but you would still have some ripple for a short time.

Well Terry, the filtering ability of a battery is dependent on the internal resistance of the battery, not it's state of charge. Even if it's "flat".
As a lead acid battery ages and deteriorates, it's internal resistance rises. With rising internal resistance, you will gradually have a bit more ripple.
Don't believe me, then take your oscilloscope and measure the ripple with and without a newer but flat battery.
This principle is used in battery capacity testers currently on the market.

The OP will have no trouble leaving the TT connected to the battery while charging that battery with a generator.

[RoyBraddy]

I too like to camp off the power grid alot here in VA.

What I did was beef up my battery system on my OFF-ROAD POPUP trailer to include getting a good smart-mode converter/charger, added additional batteries and larger battery cables, converted lights over to LEDs, added PSW inverters to run my 120VAC items, added good battery monitor panel inside the trailer, and included good marine quality BLUE SEA battery switches, fuse blocks etc.

All of this was done to be able to survive the one day/night battery run running all the things we wanted to run. Then the next morning during breakfast we would run our 2KW Honda generator with the 30AMP Shore Power cable connected directly to the generator 120VAC using a "dogbone" RV30A-15A adapter (WALMART). We can re-charge our three GP24 Interstate 85AH batteries back to their 90% charge state in as little as 2-3 hours. I will do the same thing during the early evening meal and run the 2KW generator again for a couple of hours and this seals in the 90% charge state real good now.

We are able to run our HDTV using the OTA antenna and get full high deg HTDV, run DVDs, fans, inside/outside lights, momabear will use an electric blanket on her lap when it is a cool evening, I get to play with ham Radio toys, all of the trailer 12VDC items it needs to have all run just fine.

We are very successful doing it this way camping off the power grid. The next morning I am usually down to 11.9-12.0VDC on my battery bank before I start re-charging back up to the 90% charge state.

My 2KW Honda generator sits secured in the tail gate corner of my truck bed and I just pull it out onto the tailgate to connect the 30A trail shore power cable to it. My generator always stays in the back of my truck bed out-of-site. When not is use I have a hard plastic lockable "fold-a-cover" folding bed cover that completely hides my generator when not is use.

Been doing this now for over four years and we are very successful camping off the power grid. Have always made it back home and have never got dark on us back in the woods. What I discovered was it just isn't one thing you can do to make it work - has to be a system wide planning thing. This way also fits in very nice with the camp grounds that has generator restriction run times in place.

[tnchuck100]

My recommendation would be to let the generator power the 120V system of the RV. The converters in most late model RV's have a very good 3-stage charger. It will supply more charging current than the Honda battery charging output. That is 8 amp if my memory serves me right. In addition you need not worry about "dirty" power from an off-board charger.

[chopshop]

Well, our seasonal camping season has come to an end.........what a great year! All of our power needs went "without a hitch." We had (1) marine 27 group battery from Walmart, a EU1000 honda ginny along with a Black and Decker smart charger. The trio together worked awsome; never once did we run out of power. Thanks for all the input on this thread, it was put to good use! :)

[clutch]

I am glad to hear that everything worked out for you.