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Old 07-21-2017, 04:43 PM   #21
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Brand: Thor Motor Coach
Model: Challenger 37 GT
State: North Carolina
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Originally Posted by TyCreek View Post
If that Deka link I gave is your batteries... I'd call them the same. In parallel they should be ok since they're FLA. Again, "if" that link is a match and they're in good condition ... I'd think the added capacity is worth trying for awhile as it will likely make up for less than ideally matched parallel cells.

A series connection is where cell differences really battle in both the charge and discharge cycles. In parallel, FLA types are usually quite tolerant of some mismatch during the charge cycle. Just check for heat (especially for the first couple cycles) and learn your water consumption over the first few months or so to know how things are getting along.

There is such a thing as too big of wire or getting below internal resistance and that's not ideal. My rule of thumb that has worked well in projects, is size the series connection for max of the pair or a size bigger. Parallel output sized for length plus max total I might pull. Your 4K inverter in this case and it should give wire size recommendations in its specifications.
So these are actually 215 amp hour batteries not 75? So with the 4 - T105's at 225 amp hours that would give me a total of 665 AH about 332 usable?

Also the Aims 4000 watt (12000 watt surge for 20 sec) inverter manual doesn't list a wire gage for this unit. It only list the 24v 4000 watt and it is 1/0 gage. The Aims 12v 3000 watt lists the gage as 4/0. I think that is what is on there now I'm not sure, but its only about 1.5 feet so no biggie if I replace it.

Does the wire to the inverter need to be the same as the wire connecting the batteries together? I did use 1 gage for series and parallel connections, I'm hoping that will work, the longest run is 3 feet and that is only to connect the trojan sets with the deka (in an adjoining storage bin). All the rest of the 1 gage are the same length at 9".

This is the Aims inverter I will be getting PICOGLF40W12V120V

4000 Watt Pure Sine Inverter Charger



This is the batteries I got this off their web site

Part Num GC10
MfgCode EPM
Original Manufacturer OEM EAST PENN
Voltage (V) 6
Condition New
Group Size GC
Purpose START & DEEP CYCLE
20 Hr. (Amp/Hr) 215
Reserve Capacity (Mins) 395
Reserve Capacity (Amps) 25
Chemistry LEAD ACID
Terminal POST WITH STUD
Length 10-1/4
Width 7-1/16
Height 10-7/8
Weight 130.0000
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Old 07-21-2017, 06:13 PM   #22
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Where are you buying the trojan's from? maybe they will take your old ones on trade for two more?

or

maybe list your old but still good batteries on craigslist. Maybe not the best move financially but somebody that needs a battery will win, and you'll get a little bit of money towards what you really "need"
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Old 07-21-2017, 07:09 PM   #23
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....cut....

Also the Aims 4000 watt (12000 watt surge for 20 sec) inverter manual doesn't list a wire gage for this unit. It only list the 24v 4000 watt and it is 1/0 gage. The Aims 12v 3000 watt lists the gage as 4/0. I think that is what is on there now I'm not sure, but its only about 1.5 feet so no biggie if I replace it.

.....cut.....
Yeah, 12,000 watts is an incredibly high number to power from 12 Volts even for 20 seconds. Fortunately, I doubt you'll ever have to.

Allowing for inverter efficiency, you'd need around 1200 Amps or more going to inverter. That works out to "at least" 400 Amps per each of your 3 battery strings. And that's a lot for a deep cycle battery like yours.

Fortunately, 12,000 watts would be over 100 Amps of 115-Volt AC current, and I can't imagine how you'd even get close to that high except when a large air conditioner kicks in -- but that's only for a second or two. Still, if you plan to run A/C off batteries, wire size has to be large enough so inverter doesn't kick out on low voltage while A/C is trying to start.



This is a good example of why I think the 12-Volt RV house system will be upgraded to 48 Volts like many solar houses and now mild hybrid cars. The high electrical power demands of modern RVs is a bit much for 12 Volts to be efficient.
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Old 07-21-2017, 07:40 PM   #24
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Yeah, 12,000 watts is an incredibly high number to power from 12 Volts even for 20 seconds. Fortunately, I doubt you'll ever have to.

Allowing for inverter efficiency, you'd need around 1200 Amps or more going to inverter. That works out to "at least" 400 Amps per each of your 3 battery strings. And that's a lot for a deep cycle battery like yours.

Fortunately, 12,000 watts would be over 100 Amps of 115-Volt AC current, and I can't imagine how you'd even get close to that high except when a large air conditioner kicks in -- but that's only for a second or two. Still, if you plan to run A/C off batteries, wire size has to be large enough so inverter doesn't kick out on low voltage while A/C is trying to start.





This is a good example of why I think the 12-Volt RV house system will be upgraded to 48 Volts like many solar houses and now mild hybrid cars. The high electrical power demands of modern RVs is a bit much for 12 Volts to be efficient.

Right now I have a Xantrex XM1800 pro modified sine that powers the coach lights, TV's and Refrigerator, but not the plugs in the bedroom


I want to be able to run the microwave, coffee pot and hot plate, not all at once and only for short periods of time with out having to start the get and to power all the plugs in the coach for my wife's sound machine and iPhone chargers and so forth. I've also wanted to go to the pure sine inverter and after looking at all the specs, I keep coming back to the Aims 4000 12v 120vac.

Sometime in the not so distant future I will add solar, but for now we are only going to be dry camping 1 - 2 nights in a row and will be driving during some of it so that will help with charging.

I can't imagine ever going over the 4000 watts, or even coming close to it. Its just that the 4000 is not much more than the 3000 watt is, so why not go bigger! I am not going to have the AC's connected to the inverter, they will stay strictly on gen or shore power.
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Old 07-21-2017, 07:52 PM   #25
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I don't think you need to worry about surge amperage. Use appropriate wire for your max continuous use. I hope you don't plan on really running max draw on that 4K Watt inverter because that's well over 400A (plus inefficiencies) from your battery bank and would be pretty severe duty. If so ... go back to using/shattering the 75ah rating reference for all 3 sets and add more batteries! Do you really want/need 4K or did you just happen across one for a deal you couldn't refuse?

Use a wire gauge calculator or chart to determine size.

I see there's some posts since I started typing ... lol ... same points FWIW... I've run those devices quite fine individually on 1800 pure sine inverters. Bigger/more watts is not always better ... think right tool for the job.
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Old 07-21-2017, 08:11 PM   #26
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Inverters are most efficient at or near rating ... so you really want to pick one that operates there ... sometimes 2 is better than one big one. Ever wonder why some solutions have 2 2K's instead of a single 4K? My guess is because the "normal" use would put the 4K in a very inefficient part of its operating range. https://www.e-education.psu.edu/eme812/node/738
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Old 07-23-2017, 12:02 PM   #27
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Inverters are most efficient at or near rating ... so you really want to pick one that operates there ... sometimes 2 is better than one big one. Ever wonder why some solutions have 2 2K's instead of a single 4K? My guess is because the "normal" use would put the 4K in a very inefficient part of its operating range. https://www.e-education.psu.edu/eme812/node/738
That is good to known I will check into to that, when I started out, my challenger wouldn't make it more than a few hours with out the batteries going into alarm with just the refrigerator running. The dealer replaced the batteries and it did get a little bit better but not much. I finally just turned off the alarm and let it do what ever. Plus it is a modified sine wave and causes trouble with several things in the coach.

With keeping my end goal in mind, 400 watt solar on the roof, inverter big enough to run all but the Air, and as big of a battery bank as space and money (thats a biggie) would allow, I am doing this in steps as much as possible but only want to do this once and not have to change anything to add the next step.

The inverter I'm looking at is the Aims 12v 4000w. The specs looked good and it is only a few dollars more than the 3000. My only reservations on it are:

1.The 25w it takes to get out of standby mode, will my LED lights be enough to always have power? Will my fridge be enough? If nether are on will the plugs for the phone chargers still work? Will leaving it in the ON mode keep everything powered 100 % of the time or just make more noise, even with little or no load?

2. According to the reviews ( which I haven't found many) it seams to be a little noisy. I know that is kind of subjective but it will be installed in the front storage bin where the Xantrex is now. (under the sofa). (A side note I think the Xantrex 1800 is kind of noisy itself, anybody know how that compares to the Aims?)

As far as the batteries, My thinking on this is to get as many of and the biggest ones I can which for now is the T105's. The 20 hour rating of the Deka's are 215 amp hour, I don't think that will cause any trouble but I may change them out anyway and sell the Xantrex 1800 with them.

Everybody has given a LOT of really good info on here and I really appreciate all of the good advice, it has really been a good learning experience for me. (Hopefully when I'm done I'll still remember how to start the engine! LOL)

Thanks
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Old 07-23-2017, 04:21 PM   #28
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Originally Posted by TyCreek View Post
Inverters are most efficient at or near rating ... so you really want to pick one that operates there ... sometimes 2 is better than one big one. Ever wonder why some solutions have 2 2K's instead of a single 4K? My guess is because the "normal" use would put the 4K in a very inefficient part of its operating range. https://www.e-education.psu.edu/eme812/node/738
Data curve on efficiency is similar to what I've seen before. Maximum efficiency is shown at 30% of rating, but remains excellent (by my expectations) all the way from 10 to 100 percent.

For larger loads like microwave, hair dryer, coffee maker or electric hot plate the 4,000-watt size does not appear "too" large to me, since 1,300 ~ 1,500 watts would place load right at expected efficiency peak.

Smaller loads like refrigerator or TVs which could be under 10% of inverter rating (400 watts) will no doubt be less efficient, but I wonder how the "weighted" efficiency will suffer when larger loads are averaged in.
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Old 07-23-2017, 05:59 PM   #29
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When I take a guess at typical and described use, I'd guess the majority of the day a 4K inverter would be serving well under 200 watts AC for the fridge (<5%'ish). That's the power side where inverters fall off the efficiency curve. You DON'T want to run there for extended periods of time! For higher continuous use loads (>500W) I agree the 4K would likely be fine but then that type of consumption is outside the OP hints so far (as I see it). That is why I made the 2 inverters comment, one to optimize constant load and another for everything else.

Example: A new 95% efficient 1500W inverter with pure sine could reduce the existing constant AH consumption by roughly 20% or more (compressor losses due to modified sine and low max efficiency of existing inverter). When an inverter operates efficient, it is usually quieter! The continuous power loss adds up fast and adds cooling fan noise. Complete the system capability by adding another inverter for those intermittent needs (whatever size) for, reduced wire requirements, keeps noise to a minimum and allows maximizing battery capacity.
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