How to charge batteries?

scubieman · 02-01-2011, 01:21 PM

I would like to start boondocking, but when batteries get low how do you charge them? I have a travel trailer.

MtnGuy · 02-01-2011, 01:31 PM

You will need a generator. Just to charge them, a 1000 watt generator should do the trick. Get a quiet unit like a Honda or Yamaha....your neighbors will appreciate it.

If you are caught with low batteries without a generator, you can always hook it up to your TV while running.

rthrbelsewhere · 02-01-2011, 04:57 PM

Solar is another option, but I would recommend researching panels and controllers before you invest in one. Some of those large panels could run you the same price as a generator (if your needs require one that big), but some of the smaller ones are not too bad of an investment if you're looking to hold or slowly charge the battery(ies) throughout the day. Some friends of ours invested some bank into the system they have, they are camp hosts in Colorado from May - September. I think they are now running 3 large panels on top of their coach and they are able to work the entire camping season without having to fire up the generator. Depending on how many batteries and your daily usage, you may or may not need that much sun-generated daily power.

MtnGuy · 02-01-2011, 05:16 PM

Oops, I forgot about solar. Thanks, rthrbelsewhere.

rthrbelsewhere · 02-01-2011, 05:22 PM

Tag Team, mtnguy!

acadianbob · 02-01-2011, 05:59 PM

There are a lot of different interpretations of boondocking. If you mean a State Park without electricity, be aware that many states do not allow generators under any circumstances or any time of day. Wisconsin and Michigan both have this policy. If you REALLY mean boondocking,

, like National Forest Service or Bureau of Land Management, you can typically run a generator. Mtnguy X2 on the Honda/Yamaha. Nobody likes to listen to a generator that will wake the dead run for several hours. I hate to see people start their "work" generator in a campground. They are generally not designed to minimize sound pollution. OK, I'll sound terrible here and admit this is a generalization, but my experience is also that these are the people that leave the campground for an excursion while their generator runs.

I must be grumpy today.

scubieman · 02-01-2011, 07:16 PM

Well what I am getting at is and please shout out the wrongs in thinking this.

I want at least 400-450 Ah (aka two 6 volt golf cart batteries) I want to have a 2500 watt power inverter then I can plug the camper into and pretty much run the entire camper depending on use between 14 hours all the way up to ??. And the reason I want to know how to charge batteries is just in case I boon dock and they get low.

I want to skip out in generator because in the long run between getting a big enough and feeding it fuel and annoying people it maybe just as cheap to get a inverter and two golf cart batteries.

second reason to skip generator for a long trip say I stop to go out to eat or stop and eat at a truck stop/rest area. I can run the entire camper on a quick stop or if I get out and do a sit down I can leave the dogs in camper and run the A/C off the batteries.

Again please shoot me down if my ideas sound really dumb and out there.

**Herk7769** · 02-01-2011, 08:32 PM

Have you looked into how much a pair of 400 AH 6volt batteries Weigh? Let's assume that cost is no object.

Remember that stringing (in series) two 200 ah 6 volt batteries to get 12 volts, yields 12 volts at 200 amp hours capacity. (not 400)

Paralleling two 12 volt 100 ah batteries yield 200 amp hours at 12 volts.

Say you average 10 amps draw continuously while camping. (no AC; No microwave). TV, lights, fridge, furnace and water pump when needed.

200 ah will last 20 hours till dead. Since you should always recharge at 50 percent remaining for best longevity, that is a full recharge every 10 hours. It will take many hours of generator time to replace 100 amps, since the converter will dial back the charge rate as the voltage comes up.

Now you will not pull out 200 amps a day. Most likely it will be 60-100 amps depending on your needs.

There is an excellent article called "the 12 volt side of life" here on the forum. Boon docking is a hoot if you are prepared. I boondock for about 60 days a year. Boon docking (dry camping) at Patrick AFB as we chat. Will be dry camping for the next two months with two crappy 75 ah 12 volt Deka DC-24s and my trusty Yamaha.

scubieman · 02-01-2011, 08:36 PM

Doesn't two 6 volt 200 Ah batteries equal. '. 12 volt 400 Ah?

**Herk7769** · 02-01-2011, 08:38 PM

Nope.

**Herk7769** · 02-01-2011, 08:40 PM

When hooked up in series voltage is doubled, not amps.
When hooked up in parallel, amps are doubled not volts.

scubieman · 02-01-2011, 08:44 PM

GRRRRR.... that's hard to swallow

**Herk7769** · 02-01-2011, 08:47 PM

Lol. I am on my wife's iPad so I can't attach the PDF, but search the forum for the 12 volt side of life. It will explain it better than I can.

**Herk7769** · 02-01-2011, 08:52 PM

Bikendan posted the PDF in the 6 volt questions thread. With this goofy app I have no idea how to link the thread.

scubieman · 02-01-2011, 08:56 PM

I kinda started reading that understanding 12 volt batteries. The problem is that 200 Ah is not bad but if you can only drain 50% brings it down to 100 Ah then I would maybe get 8 - 10 hours of use which is still a buch. But not it's to the point do I dare just get a better generator. I need to know how much I am going to use the camper in 2011. No planned trips but do have trips in the works.

Also I have a family so full hookups will probably be the choose but I like sporting events which usually are no hook ups.

**Herk7769** · 02-02-2011, 08:57 AM

The "no hookups" situation is what I deal with all the time.

This is what I have learned: (I am sure others will have different opinions - this IS an open forum

)

1) If you plan on air conditioning you need a minimum of 3000 watts and the generator not running in economy. You will never be able to air condition on battery. (A Yamaha EF3000 or two Honda Ei2000 in parallel)

2) You need a 1500 or more watt inverter (remote control is a bonus) to watch TV on battery power.

3) No matter how big your generator is, you are limited to the Power Converter's ability to put amps back into the battery. That mount is determined by the battery voltage at the time. If it is very low the "fast charge" stage of the 3 stage center will squirt in about 15-20 amps but as the voltage recovers, the next stage will kick in to keep you from boiling your battery. The amps drop to about 9 amps. Then the final stage kicks in when there is about 10% to go, and it drops to 2 amps. It can take running the generator at idle ALL DAY to charge a very low battery. This is a power converter limit; not the generator.

4) If the battery is very low it is faster to remove it from the camper and use the DC charging port on the side of the generator. It will fast charge the batteries without the limits of the power center. You MUST watch them like a hawk to avoid boiling them dry or exploding them from too much hydrogen being trapped under the vent caps.

**Herk7769** · 02-02-2011, 08:29 PM

source for 400 amp hour 6 volt batteries:
Surrette S530 6V 400 AH Wet Battery Wet Batteries | CivicSolar

Note they weigh 117 pounds EACH and you will need two. That will give you 12 volts and 400 amp hours. It could also take 2 days to recharge them running the generator.

scubieman · 02-02-2011, 08:36 PM

Lou, you already made me cry about the Ah question, but now that I sit down and think about it ,it makes sense. I am unsure what to do. I thought about getting 3 12v batteries at about 75 Ah a piece. I don't know yet. Or just go the generator route. My ideas have changed.

**Herk7769** · 02-03-2011, 07:16 AM

Sorry I made you cry, but I am still wiping tears from when I found out about how dry camping works.

No matter which way you go, you will need a good QUIET generator. That will set you back a grand no lie. The Honda Ei2000s are great for topping off batteries. If you want air, you will need a 2400 (or two 2000s)(for a 13.5K AC) or a 3000 (for a 15K AC).

DO add a second 12 volt 75. It is only about 80 bucks and will double your capacity to 150 AH. That and the cabling is a 125 dollar upgrade.

OR

Dump the cheap a** 12 volt DC battery you have now for two 200AH six volt batteries in series. This will run in the 400 dollar range and only makes sense if you dry camp A LOT. My 150 AH tank seems to handle us ok as long as I can run the generator every day.

DO NOT buy a 500 dollar contractor grade generator. You will get tired of having to repaint your truck from the key strikes. If you stop painting it, they will pop your tires.

**Herk7769** · 02-03-2011, 07:27 AM

Sitting in dry camp now and using the data from the TM-2025...

No load: (Propane detector; Inverter on and charging phones; Fridge on Propane) -2.9 amps (Minus means current out of the battery)

Add TV; antenna amp: -13.5 amps

Killed generator last night at 8PM at 100% capacity
Watched 2 hours of TV and read using LED lights.
Battery bank this morining at 84%

I have replaced all lights with LED pads. Every LED in the camper on draws the same power as ONE two bulb incandescent and the camper looks like a circus tent.

Generator is running now to use the microwave. Recharge rate is 11.2 amps. So if you pull 18 amps or so for 3 hours it will take 4 hours of generator to replace that power.

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