Another inverter question

[Fred Cook]

Still trying to get my head straight on the Xantrex XC 2000 Inverter/ Charger that’s is supposed to arrive soon. Quuestions:
1. Will the inverter power both electrical legs in the coach?
2. If it does power both legs then why is there only one 12/2 wire coming off the circuit panel leading to the inverter as input and one 12/2 wire leading away as output?
3. I have heard some say they use the inverter at night…. How long will it power your electrical needs while boondocking before the batteries go dead?
4. And…. If the batteries do go dead, how would you be able to start the generator to recharge them?

Hopefully these questions don’t seem too dumb to answer.

[Richard Davis]

Fred
The inverter is powered from one leg of the main electrical box (usually a 30 amp breaker).  It's output usually goes to a sub-panel of breakers to power downstream items (microwave, TV, some outlets).  I installed a residential fridge in my Monterey powered from the inverter and my wife and I both use CPAP machines.  In a 24 hour period we will use between 150 and 200 amp hours of battery power.  That requires a battery bank of about 400 amp hours (4 six volt golf cart batteries).  You NEVER want to allow your battery bank to be depleted below about 50 percent state of charge, since that will damage lead acid batteries.  If your house batteries get depleted to the point they will not start the generator, the battery boost switch allows connection to the engine starting batteries.  Hope that makes sense.
Richard
p.s. Lead acid batteries have a full State of charge when they sit with no load at 12.6 volts.  They are at 50 percent state of charge at 12.0 volts. 

[Fred Brooks]

    Fred,
Richard answered all your questions, The only comment I have is that I believe your generator is started by the chassis battery and not the house for the reasons you stated. Fred

[Fred Cook]

Thanks very much guys. This helps out a lot! Just one more question though, the manual for my coach indicates four 6-volt house batteries required.  However what I have is two 12-volt interstate batteries. Is there any problem with that?

[Eric Maclean Co-Admin]

Fred
The biggest difference is that the two 12volt batteries will not likely have the reserve capacity of the four 6 Volt's
Hence the number of amp hours of useable battery capacity is higher with the four six volt units.
It all about the number of plates and surface area of those plates inside the battery ( rule of thumb the heavier the battery the better the battery)

[Joel Ashley]

Fred, I think the guys pretty well answered your questions.  I’ll back them up.  The inverter charger and some house circuits get power via one 30 amp leg coming off the 50 amp circuit breaker/fuse main box that runs to the inverter.  Your coach may be somewhat different than mine, but see the photo below of the flags I added to ours early-on when I was trying to understand it myself.

Knowing how many amps each inverter-sourced device uses can help;  add up the amps of the ones that run overnight, multiply that by the hours they might be on, and make sure that number doesn’t exceed the total amp-hour rating of your house battery bank.  For example, any lights left on might each use 1amp per hour, a hydronic unit’s pumps and igniter use some… but use direct 12 volt off the batteries.  They still add into the amps use equation. 

An electric heater left on low overnight might go 800-1200 watts (~10 amps/hour) via the inverter.  Our RV fridge plugs into one of the 50 amp Main’s circuits, not the inverter’s leg, so it goes to propane when off the grid.  People with residential fridge conversions must use their inverter circuit for that, and count its amps into the overnight mix.  Our gas fridge means I don’t have to.   

I put small white labels on some 110v appliances, like the coffee maker and microwave (10amp @) to remind me how many amps each uses, for calculating all-day consumption, so I don’t approach too closely the 12v (50%) battery status red zone, before running the generator.  As Eric noted, you’re best off with four or more 6 volt deep cycles than your two 12 volt ones.  And when adding up amp use, remember that batteries suffer if you allow them to go to 50% charge, i.e. 12 volts;  12.8v is actually full charge, despite the batteries’ moniker of “12v”.  Older batteries won’t have the total amp-hrs of new ones either;  as Eric mentions, the plate surface counts… but it’s reduced by sulfur deposits with age

It’s likely your generator starts off the chassis 12v set of batteries, as ours does and like Fred says.  There are some coaches that have house set generator starters, a few switched over by previous owners for their own reasons.

Joel

[Richard Davis]

Fred
Your two 12 volt batteries are likely inadequate to do much with the inverter.  If they are not true deep cycle batteries (most likely are not), they will not last long as an inverter battery bank.  I would suggest you do a bit of research on deep cycle batteries if you are going to replace them.  In my case, I prefer AGM batteries over flooded batteries since I detest having to deal with the corrosive issues of flooded batteries, and I do not like having to check and fill the liquid.  AGM batteries also charge faster and provide power longer since they do not waste as much energy as lost heat.  Of course, they are a little more expensive than flooded batteries.  Lithium batteries have become very popular, but they are even more expensive.  I did not go lithium because my 17 year old charging system does not have lithium parameters and I would have to deal with the issue of not being able to charge lithium batteries direct from my engine alternator.  I actually chose four 12 volt deep cycle AGM batteries at 155 amp hours each for my battery bank of 620 total amp hours.  They are the biggest battery I could fit 4 of in my battery tray.  You may not do as much boondocking as I do and would not need as robust a battery bank.  The least expensive approach, and probably the best bang for the buck, are the 6 volt flooded golf cart batteries (you would need 4 of them to give you 400 amp hours).  They run about $100 each at Sam's club.  In perspective, I paid $350 each for the 155 amp hour AGM batteries.  Good luck with your continued learning curve.
Richard     

[Joel Ashley]

Consider four of the Full River 6v AGMs, at 224ah each, as I put in our ‘06 Monty.  Shop around for price as they don’t come cheap, and there are other brands of similar quality.  Full River is a California company but I think the product is built in Asia.  However they monitor their build quality closely.  Mine have been in about a year and not a hint of corrosion anywhere, especially not on my long-suffering tray.

Example dealer:  https://www.batterysystems.net/dc224-6-fullriver-6v-224ah-gc2-sealed-lead-acid-agm-battery

Joel

[Fred Cook]

Thanks to all. I received my inverter/charger from UPS last night and will install it today. My next battery purchase will be four 6-volt batteries.

[Richard Davis]

Fred
Since you currently have 12 volt batteries wired in parallel, you will have to recable your system to install the 6 volt batteries in series-parallel.  That's two sets of two batteries.  Two 6 volt batteries in series (+ to -) will will give you 12 volts.  Then the two sets wired in parallel (+ to + and - to -) will keep it at 12 volts but double the amp hour capacity.  Aren't batteries fun?
Richard

[Fred Cook]

Fred
Since you currently have 12 volt batteries wired in parallel, you will have to recable your system to install the 6 volt batteries in series-parallel.  That's two sets of two batteries.  Two 6 volt batteries in series (+ to -) will will give you 12 volts.  Then the two sets wired in parallel (+ to + and - to -) will keep it at 12 volts but double the amp hour capacity.  Aren't batteries fun?
Richard

Yep, gonna be lots of fun! Lol. I got the inverter/charger installed today and it works fine. The 12 V batteries I have in there now only lasted about a minute before inverted kicked off. I looked on the battery and each batter is 88 amp hour. I suppose that’s OK for now since we rarely ever Boondock. But I would like to have 120 V while driving down the road which should not be a problem as long as the alternator is charging the batteries.