Travel trailer battery/generator use.

Buddha.

Lurker
We are traveling to CO for the summer to work camp. We'll be staying in our new to us 2005 model 30' travel trailer. At our work location 110v electricity will be provided, at no cost. So that's a no brainer there, we'll be on shore power.

However we may be boondocking for a couple weeks beforehand and also after the summer season. The TT needs new batteries and I intend to buy two 6v golf cart style batteries that are rated 215ah each for a total of 430ah. We have a used Yamaha 3000iseb generator. Doing some uneducated research it seems that if I were to run the batteries down to 50% or so it would take hours for the generator to charge them back up. Which is inconvenient. Also I'm confused about how low of a voltage I can discharge the batteries to. When it says 215ah does that mean I can get all 215 ah out of it before recharge or is it more like half of that? I don't want to run the generator non stop.

Right now my best guess is to run the generator when using high load appliances such as coffee pot, microwave, hair dryer, air conditioning etc and hope that is enough to keep the batteries charged. Thoughts? Is it more economical to run the fridge of propane or off of the batteries and charged by gas generator?

Would a 200watt solar setup do much for me or no? I'm not looking to spend $1000+ on solar.

Edit:
If I discharge the TT batteries and then hookup the trailer wiring will it kill my truck battery? I've only got the one truck battery, of unknown quality.
 
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comptiger5000

Adventurer
If you plan to run the generator to power the high-draw stuff (and let it stuff a little power into the batteries while it's running), 200 watts of solar should do a pretty good job of keeping things charged up (provided you're somewhat careful with power use from the batteries).
 

dwh

Tail-End Charlie
Hooking batteries in series doubles the voltage. In parallel doubles the amperage. 2 x 215ah 6v in series will result in a 215ah 12v battery bank. Following the 50% rule will leave about 100ah usable capacity.

The 50% rule is all about battery lifespan. Take a deep cycle lead-acid battery down 20% and recharge and you might get 3000 discharge/recharge "cycles". Take it down 50% and you usually get around 1000 cycles. Take it down all the way and you'll get 300-500 cycles depending on who made it. It's a trade off. I'm the kind of guy who will ignore the 50% rule and just plan on buying new batteries twice as often. Batteries are disposable commodity items to me and I like new ones.

Yes it takes hours to recharge. Even with a top quality charger lead-acid batteries "absorb" slowly. The closer they get to full, the slower they absorb. Nature of the beast.

What voltage you go down to depends on what percentage discharge you can live with.

The 12v outlet on a portable generator is NOT a good battery charger. Good enough to put some amps in to get a vehicle started, pretty much useless for actual battery charging. The "12v converter" in most RVs is usually also crappy at battery charging. The right way is to get a good shore powered charger, such as Iota, and power it off the generator when shore power is unavailable.

But no matter what, it will still take hours (4-12 hours, depending) for a 50% drained lead-acid to absorb back to 100% full.

Running a propane fridge from 12v is an IMMENSE power hog. The 12v option is for when the engine is running, driving down the road, where technically you're supposed to have the main valve on the propane tank shut off (which no one ever does). If a 200ah battery bank ran a good size propane fridge for even one day it would be a miracle.

You will HAVE to run the gen for the high load stuff you have described - unless you've got a giant 2000w or 3000w inverter installed in your trailer to invert 12vdc to 120vac. Totally different then "converting" 120vac to 12vdc. Inverter and converter are different units. Converters are cheap. Big inverters are expensive. Most RVs do not have a giant inverter. Good ones can add a couple thousand to the price of the trailer.

But if you did have a giant inverter...you'd need a hell of a lot more battery. 200ah (100 usable) is no where near enough to run big loads from a big inverter.




Any amount of solar will help. A couple hundred watts is a good start. There is no such thing as "too much" when talking about chocolate or solar.

But you gotta park in the sun. Even spotty shade will cut the the output from the solar by anywhere from 30%-100%.
 

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Buddha.

Lurker
If you plan to run the generator to power the high-draw stuff (and let it stuff a little power into the batteries while it's running), 200 watts of solar should do a pretty good job of keeping things charged up (provided you're somewhat careful with power use from the batteries).
Thanks

The 12v outlet on a portable generator is NOT a good battery charger. Good enough to put some amps in to get a vehicle started, pretty much useless for actual battery charging. The "12v converter" in most RVs is usually also crappy at battery charging. The right way is to get a good shore powered charger, such as Iota, and power it off the generator when shore power is unavailable.
How do I use something like the iota battery charger when the trailer's big 30amp cord is already plugged into shorepower/generator? It seems like something would get overloaded with the camper's charger and the iota both trying to charge at the same time.
 

DaveInDenver

Expedition Leader
How do I use something like the iota battery charger when the trailer's big 30amp cord is already plugged into shorepower/generator? It seems like something would get overloaded with the camper's charger and the iota both trying to charge at the same time.
The Iota is the 120VAC-powered charger in this case and would replace whatever is in the camper. It would be there certainly on regular shore power but it would likely also sit between generator's 120VAC supply and the battery, assuming Iota says it's acceptable to do so.

What he's saying is standard chargers installed in campers are not much good and typically the 12V supply on a generator (if you use that) isn't much better at actually charging a battery.

The only time it would not charge the battery would be on solar. It's OK to leave Iota chargers connected to the battery with 120VAC not present but they do add to the load so while on solar it may be better to disconnect it just to remove an unnecessary drain while boondocked.
 
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Buddha.

Lurker
The Iota is the 120VAC-powered charger in this case and would replace whatever is in the camper.
Of course, I should have figured that out.

So I'll replace the batteries and the battery charger. It'll probably take as much time to find it as it will go change it.

Thanks.
 

Bbasso

Expedition Leader
Solar is a great addition, even if it's only job is to keep the batteries topped off when away. But in your case, 200 w would be the min I'd bother with. It is a worthy investment.
Just be sure to get a mppt controller much bigger then your current needs, so in the future you could add more panels and still be within the scc limits without an additional cost.
 

Buddha.

Lurker
So we've been in the trailer for a couple weeks now and I finally checked into the type of battery charger I have. It's an Intel power 9100. It looks like if I buy thier "charge wizard" controller for $25 it will charge my batteries in four stages. This would be an improvement.
 

DiploStrat

Expedition Leader
Caveat: I do not own a Progressive Dynamics converter. (But I have friends who do.)

The "Charge Wizard" will improve the charging profile, but my friends note that the Charge Wizard goes from bulk charge to float without spending any time in absorb. (Their charts confirm this.) The Progressive Dynamics line is aimed at reducing water consumption for people who plug in at a campsite every night. Not the end of the world, but should you decide to replace the converter with a better charger, look for one that has a reasonable absorb stage.
 

Buddha.

Lurker
Thanks, good to know.
My charger is the lowest rated available, something like 30-35amps. If I buy a new one in the future would I be overloading anything if I stepped up to thier 50amp model? Would this charge the batteries faster?
 

DiploStrat

Expedition Leader
Thanks, good to know.
My charger is the lowest rated available, something like 30-35amps. If I buy a new one in the future would I be overloading anything if I stepped up to thier 50amp model? Would this charge the batteries faster?
If I were spending money on new gear, I would not buy Progressive Dynamics - there are brands that I like better, but YMMV.

To your other question, it depends. On what? Read here: https://cookfb.files.wordpress.com/2016/09/battery-charge-slides.pdf

Nobody wants to read a massive tome, but the subject can be a bit complex. It depends on the size of your battery bank, how many amps you use between charges, and a few other factors. As a practical matter, you would probably see the difference between a 35A charger and a 50A charger. But even with a 100A+ charger, you will probably find that your actual charge rate hovers around 50-60A most of the time.

N.B. All of these comments are for lead acid only. LiFePO4 is different.
 
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