dry docking and charging

[guscampag]

I have a small travel trailer and have set it up with (2) 6-volt batteries for drydocking. When I arrive to a destination and the batteries are fully charged, we do not use much electricity and the batteries will remain charged for about 5 days. I will then charge with my 3000 Watt Champion Inverter Generator. The problem is that even after running several hours and the gauge showing a full charge, the batteries will only last about a half day and need recharging. I don't understand what is happening here. Any insights would be greatly appreciated!
thanks.

[ssthrd]

My setup.

[bpounds]

As a dedicated boondocker for many years, I've written several times about how to manage generator battery charging. Rather than write more stuff, I copied and pasted from past discussions. I have solar now and rarely have to pull out the generator, so it was better for me to look up old posts.

Couple points that are not in the below posts - make sure your water heater stays on propane. Turn off the AC switch if it is dual heating. Same with your refrigerator - run it on gas only. You want all that charging juice to hit the batteries, not running appliances that are more efficient on gas. Lastly, all I ever did was plug the trailer shore power cord into the generator. I never carried a separate battery charger.

Past posts.
6/2012
Depends on how discharged they are. And the key thing is to not let them discharge any more than necessary. So if you're going to boondock for several days or more, you want to run the generator every single day, starting on the first full day of camp. It is better to keep the batteries topped up, than it is to let them deeply discharge and then try to bring them back. I usually schedule between 1 and 2 hours per day for generator charging. That will keep me up around 90 percent. The last 10 percent takes a very long time to recover, and is an inefficient use of the gen.


6/2012
I've learned that the key to boondocking with battery and generator, is to charge for 1 or 2 hours per day, beginning on the very first day. Don't wait until you need to charge. It is better to keep the batteries topped up than it is to try to bring them back from a deep discharge.

This is also why solar charging works so well, but that is another topic.


It will take a long generator run time to fully recharge batteries. I'm talking 24-48 hours. Not realistic.


9/2011
I've found that in practice, I can get through a week of dry camping very nicely by running the generator between 1 and 2 hours per day. That keeps me in the 90% range. It is that last 10% that takes so much time, and you don't need to try for that. And it is important that you start charging that on the very first day, so the batteries don't ever get too low. It will seem like you don't need to charge on day 1, but it is important that you start replacing the used amps. If you have to run a heater overnight, that really uses the juice and you'll have to extend the genny time. But if you don't have a quality converter or standalone charger, you will fall further behind each day.

[ajriding]

Yes, solar.
The generator is really just for running the AC when boondocking, otherwise leave it home (unless there is no sun where you are). The solar will do the bulk of the work.

[2oldman]

guscampag wrote:
Sounds like my best bet is to go with a couple of solar panels..

You haven't answered any questions.

[Boon_Docker]

2oldman wrote:
OP is gone.

I didn't see him leave. :B

[guscampag]

Sounds like my best bet is to go with a couple of solar panels. I was thinking about doing that but didn't think I would really need them since I had the generator. Renogy 200 W suitcase panel is on my list.
Im only have the 1/3 - 2/3 "battery gauge" and I think I have a cheapo convertor. Hopefully I won't need to change these right away. The suitcase panel comes with a Voyager controller. I have (2) of the 6 volt Trojan batteries which are very new.
thanks for all the suggestions.

[2oldman]

OP is gone.

[Lwiddis]

"Is that still true for GC2? I understood them to be able to go a lot lower."

Your choice how low you go, philh. The lower you go the fewer cycles you'll get. See the Trojan cycle chart at

https://www.trojanbattery.com/products/deep-cycle-flooded/signature-line-flooded-2/

Cycle to a 60% discharge you'll get 1,000 cycles.
Cycle to a 40% discharge you'll get 1,500 cycles.

[Lwiddis]

"I have no idea if the performance that I have seen is typical,.."

ssthrd, sounds to me that you have a very adequate solar system doing what it is supposed to do.

[ppine]

If you have conventional wet cell batteries, you never want to run them down. Use your charging system every day and keep them up.

[ajriding]

While the gen is putting a 12DC charge on the battery whatever DC charge gauge you are reading will read full, this is because the generator is putting full voltage on the battery and the gauge sees this as a full battery, remove the generator and your battery will go back to only a partially charged voltage and this will show on the gauge, but sometime there is a "surface charge" that will sit on the battery, some kind of electrical mystery, but that surface charge will go away after just a very short time of using lights, within minutes.

The generator probably only provdes very minimal DC power (amps), so will take a very very long time/ multiple tanks of gas to recharge two low batteries.
Better to plug a good battery charger into the AC plug of the generator and charge the batteries off the charger.

Solar is really the way to go. You batteries will last a year or two longer, maybe 3 or 4 years longer since you are hard on them running them down like you described. 100 watts will suffice and 200 watts is plenty. They key here is the charge controller (takes current from the solar panels and controls what goes to the battery). MPPT is what you want not the $20 ebay one, but at least $50 range will do. 20-30 amp model is enough for what you describe. You batteries will be topped off nearly all the time.

[philh]

Vintage465 wrote:

And a real gauge, make sure you don't take your battery bank down lower than 60%.

Is that still true for GC2? I understood them to be able to go a lot lower.

[ssthrd]

This year we have been boon docking quite a bit, and so we picked up a couple of 130 watt solar panels to look after our two Trojan T105 6v golf cart batteries. They work great for me. We have to chase the sun a few times a day, but no big deal.

We have been usually down to 70% or so when I check the battery controllers in the morning, and it only takes a few hours to get them back to 100% again on a nice clear day. Mine even charge on cloudy days, but of course not nearly as well as on a sunny day.

I have a 2000 watt gen/inverter for those nasty days. We were set up for 14 days, and used the generator only once initially to get things going. We also have a couple of small 100 watt USB inverters to charge our electronics in the trailer.

The beauty of these solar panels is that they automatically stop when the batteries are 100% at which point they go into a maintenance mode similar to a battery tender. Just have to check the water level in the batteries now and then to make sure the plates are covered.

I have no idea if the performance that I have seen is typical, but I sure am happy with the results for our purposes.

[Lwiddis]

Daily full recharging is best for deep cycle batteries, not what you are doing. An adequate solar system would eliminate the generator use almost every day.