Hi Everyone,

Could I get some guidance regarding the most favoured type of battery charger, maintainer and preferably one with a desulfating cycle suitable for a battery bank of 4 6V T105, in series and parallel for a 12V system with 440 amp. Also, a compatible, single use converter.

This is a new battery bank and charging system going into a vintage Prevost, 83, where I'm bypassing and removing the ancient inverter I think is getting pretty tired. The only appliances  "in use" running off it when the coach is rolling is the current fridge. I'm not interested in running multiple A/C units and will only occasionally be boondocking, likely at bus rallies. I'm strongly focusing on bypassing the need for an inverter at all and would prefer to just beef up my DC and utilize that more.

I'm a new RV'er and this is my first rig and I'm not especially technically fluent. Would appreciate any advice and feedback on getting the appropriate pieces to work with this new battery bank. I'm not looking for any combo units of converter/charger, I would like these specific units as designated to each job and to do it well.

Thanks so much.

Cheers !



Tags: How to Wire RV Battery Banks, How to install RV Battery Banks, RV Battery Bank Chargers, RV Battery Chargers, RV Dry Camping Battery Usage

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  1)  Say you don't want to run a big inverter to power an AC Compressor type of decent RV sized refrigerator (NOT a dinky college dorm size)  that will suck your four batteries dry long before an LP Gas fridge would ever come near depleting a 20# tank "SUBJECT TO SIZE AND TEMPERATURE AND LOAD" (mine could run weeks and weeks and weeks while dry camping on 20 # of Propane)

   2) You don't want to use a typical 2 way (LP Gas or 120 VAC Electric) fridge.

                         THERES A THIRD OPTION

 My buddy has a small solid state thermoelectric type of fridge in his RV that uses 12 VDC and not near the energy draw as a typical 120 VAC Compressor, and of course NO BIG BULKY INVERTER IS REQUIRED. They also waste energy themselves you know in the form of heat loss and you dont get the energy out the battery puts in (heat losses NOT 100% efficient)

 HOWEVER they do not have the cooling capacity as a 120 VAC Compressor type or an LP Gas RV fridge. His only has a limited temp delta it can cool to lower then the ambient temp, and I haven't seen very large units that are the size of my RV fridge.

 SO IT ALL DEPEDNS ON HOW YOU USE THE RV,,,,,,,,,,,,,,,,,, AND HOW LONG YOU WANT TO BE ABLE TO DRY CAMP WITH NO SHORE POWER AVAILABLE (and have a decent sized fridge),,,,,,,,,,,,,,,AND IF YOU WANT TO INSTALL A BIGGER INVERTER OR NOT besides a small compact unit for Computers and cell phone and camera battery chargers etc etc.

 With my four batteries storing 460 Amp hrs and an LP Fridge I can dry camp a long time and NOT have to worry much about the batteries, as LED lights and vent fan and water pump or furncace just dont use that much battery, while my LP tank can run the fridge, so I'm not drawing much out of my batteries to cool and freeze my food supply.

PS if you couple that with 200 watts of Solar Panels and a Charge Controller and also have an Onan back up 4 KW Generator (NO WAY Id travel without my Generator, its so handy) YOURE GOOD TO GO

 UNTIL YOU RUN OUT OF FRESH WATER OR YOUR HOLDING TANK IS FULL LOL Fresh water and holding tank capacity is the REAL limiting factor (NOT all these fridge choices and batteries and big Inverter talk) for extended dry camping in one location grrrrrrrrrrrrrrrr I carry 110 Gals of fresh water and me n the little woman can go 8 + days but that's about long enough at many places.............

 YOUR MONEY YOUR CHOICE, We report now you decide lol

 Best wishes n God Bless, let us know how you end up.

 John T  Electrical Engineer in Indiana

This link proved to be very valuable and useful. I learned something new today. Thanks John for passing along this link. I run 4 batteries and I admit, I was just streamlining the cables parrellel .(now adding rewiring battery bank to the To Do List).

  What's so great AND SURPRISING in that article is the current measurements in the simple straight ladder connection (and how much different they are) versus if they are hooked up correctly. I have mine I think their second best now but plan to buy some equal length new cables and balance them perfectly to protect that over $400 battery investment. That along with my Xantrex Truecharge2 Charger ought to yield me 8 + years I hope. My buddy has a Xantrex and he got like 9 years out of his batteries. Since I have BOTH Solar and its charge controller PLUS the Xantrex, I'm shooting for 12 yeas from my batteries  lol Wishful thinking butttttttttttt its the TOTAL NUMBER OF charge and discharge LIFE CYCLES that can in part limit a battery life BUT HECK MINE ARE LIKE HARDLY EVER RAN DOWN maybe they will last rest of my life???????? Of course, I'm sure batteries have been hooked the simple ladder way and still lasted for years no problem, however, better to be safe then sorry and why not do it RIGHT the first time which may well help, it cant hurt to wire them right I figure. To each their own choices is fine, but my old electrical engineers brain has convinced me of mine.

 John T 

My comments were not targeted towards someone wanting to run 8 days with no desire or means of battery recharge.  Not every RVer has such a need.   Options TO recharge to those that want to can be as simple as starting the engine once in awhile . . or an onboard separate genset . . . or a solar panel, etc.  All my RVs are setup to charge at a max rate of 80 amps @ 14 volts to the house batteries when I start the RV engine (no separate genset.

The Sundanzer  5.8 cubic foot chest refrigerator is the most amazingly effecient unit I've ever seen or used.   It will run fine with just a single 100 AH battery and a single 70 watt solar panel (in sunny areas).  I have one hooked to a 120 watt solar panel in the dark woods in the NY Adirondacks.  That's all it needs.  It runs on 5 amp-hours a day when not being opened and closed constantly.  Twice that if it is opened a lot. 

  Thanks John, that sure sounds like a neat little efficient refrigerator that can be powered with a battery and an Inverter (for those with a big enough Inverter and enough battery storage). Hey now that you added the 70 watt solar panel into the mix that can sure help extend battery life!!!! Of course, if you're also using battery power for  12 VDC lights and vent fans and furnace etc PLUS using battery power and a big enough inverter to operate the fridge you mentioned, your dry camp time is more limited (unless you run engine or genny to recharge batteries) versus what it would be if you powered your refrigerator with LP Gas.

  EXACTLY as you mentioned "Not every RVer has such a need." If you're one who fairly often spends  nights in commercial RV parks with electric hook ups, a battery and inverter powered fridge will do just fine. HOWEVER if you're like us and may spend a week at a time in say Utah or Colorado at a BLM or Natl Forest Camp WITHOUT ELECTRICITY  then a battery inverter powered fridge is out of the question so we opted for an LP Gas/120 VAC unit (actually we didn't opt, that's what was in it when we bought it). Heck if we didn't run out of water (maybe 8 days) using an LP Gas fridge which doesn't use up battery power, would allow us to stay till the cows come home lol


  IE   Consider a 3 way (LP Gas,,,,,,12 VDC,,,,,,,,,120 VAC) fridge!!!!

  A)  It can run on LP Gas versus precious battery power

  B)  RUN IT ON STRAIGHT 12 VDC (no inefficient Inverter even

        required, direct 12 VDC battery power, no AC

       Compressor motor to suck up battery power)

  C) Run it on 120 VAC when parked where electricity is available

 HOWEVER that's more expensive I'm sure then the neat little 120 VAC fridge you mentioned soooooooooooo its all about trade offs and as you indicated how a person uses their RV,,,,,,,,,,,,,,, and what they want to spend on a fridge (Bet your unit is wayyyyyy cheaper),,,,,,,,,,,,,,,,,and how long they want to dry camp without electricity.   HECK IM ABOUT READY TO GO BUY ONE LIKE YOURS AS A BACKUP LOL

 Thanks again for the info, if a person wants to go with a 120 VAC battery/inverter fridge your unit sounds great, if they want to spend the bucks for a 3 way (12 VDC, 120 VAC, LP Gas) that sounds greater as its the best of both worlds, we have a 2 way (LP Gas or 120 VAC) which suits us fine and allows us to stay dry camped days on end and longer then if we had to use our batteries to run the fridge also.

 VERY FUN CHATTIN WITH YOU I enjoy this, glad to get your good information, best wishes n God Bless you and your family and keep warm up there in New York brrrrrrrrrrrrrrr lol

 John T in also cold Indiana, but headed to Florida soon, wish we could meet up in our RV's sometime for fun n chat and maybe a cold adult barley soda beverage woooooooooo hoooooooooooo

Long story short - a 3-way non-compressor fridge uses a lot more electricity (when in electric mode) then a compressor fridge.

Also - a 3-way must be level, whereas a compressor fridge does not.   I find the compressor refrigerators much  more convenient for what I do. 

A typical 3 way absorption refrigerator used in 12 volt DC mode uses a lot more electricity then a compressor refrigerator running on 12 volts.    A 4 cubic foot compressor fridge will use, on average, 2 amps per hour @ 12 volts.   A 4 cubic foot absorption refrigerator (no compressor) will typically use 6-7 amps per hour @ 12 volts, on average.

In regard to the benefits of proper connections of battery banks? I suspect much is theory and not very meaningful in every day life. That is unless something is hooked up EXTREMELY poorly.  My one battery bank at home is 48 volts. Has eight large Rolls-Surette batteries all hooked in series.  On the 9th year and all is fine so far.   At my Adirondack cabin I've got 8 Trojan T-105 type batteries (actually Deka/NAPA 8144 equivs) hooked in series-parallel in  a somewhat hap-hazard way  and they are now 8 years old with no problems.  My RV has four Deka/NAPA 8144s hooked in series-parallel to make 12 volts and they too are 8 years old now.  On that setup - there are two pairs of batteries.  Each pair has a 12" cross cable for the series connection . . and the two pairs are connected by a 7 foot long cable for the parallel connection between the two pairs.   My point is - they have all made it to and surpassed the usual lifespans.  Only special care is they've always been "watered" and never left in state of discharge.  Also none were ever run down to more then 50% discharge and terminals were always kept clean.    The 48 volt battery bank is charged by twin Outback MX-60 chargers.   The 12 volt bank at my cabin is also charged by an Outback MX-60 charger.  The batteries in my RV are charged by the standard 18SI Delco alternator when running and with a Guest 2611A maintainer when parked.   Yes, my three battery banks are anecdotal but this is my "actual use" report and I've had no premature failures with any of the batteries.  In fact, I'm afraid they are all ready to start going at any time.  They are way past due. 

Also make sure you use proper size cables and dont crimp them they corroid alot and faster.inverter should close the your battery bank and have some type of ventalation if it is a larger one.good luck and keep them clean and they will last a long time.

    Good point there Mark Danieli,,,,,,,,,,,,,,, proper sized cables and connections and correct length where possible is certainly a good practice. Also, some of that anti corrosive battery terminal protection spray in the right places is a good idea. In the old top post  batteries I used BOTH the felt looking washers under the terminals PLUS the anti corrosion spray NOW THAT WORKED GREAT.


  HOWEVER, A VERY IMPORTANT THING  in my opinion as an Electrical Engineer of 40+ years,  is the Smart Gauges extensive engineering research and testing and best connection method for multiple batteries I will discuss more below. Another electrical engineers opinion, I prefer true deep cycle golf cart type of batteries versus the semi or quasi so called RV Marine Batteries sold at Wally World and other places. As far as theory, engineering, design, construction and intended use, for RV and dry camping, the true deep cycle is superior for the way I utilize my batteries. MAY NOT BE BEST FOR ALL, IM ONLY SAYING ITS BEST FOR ME yall do as you please, I'm ONLY trying to help, NOT TELL YOU HOW TO SPEND YOUR MONEY as those batteries aren't cheap. The reason I opted for an expensive quality Xantrex Truecharge2 Smart Charger and utilized the proper connection methods listed below, was to protect my hefty battery investment. Anything which helps keep my batteries better balanced and can better charge and maintain them and extend their life is the BEST WAY TO GO IN  MY ENGINEERING OPINION!! 


  Back to the previous discussion as far as choice of Refrigerators to use, be it a battery/inverter AC Compressor Motor or a 2 or 3 way (LP Gas, 12 VDC or 120 VAC) my bottom line which influenced my decision to run on LP Gas when dry camping is that (unlike an AC Battery/Inverter Compressor Motor Fridge) its NOT sucking so much precious limited battery energy which I use instead for Lights and Vent Fan and Water Pump and Furnace. If I was camped  off the grid for several days and had to use my batteries to ALSO run an AC Battery/Inverter fridge running a Compressor Motor, MY BATTERIES WOULD JUST RUN DOWN  WAY TO SOON GRRRRRRRRR  But different strokes for different folks and my choice may not be suited for others. If a person camps plugged in often, a Battery/Inverter powered AC Compressor Motor fridge isn't such a problem regarding dry camp time limitation. We choose to camp at a lot of National Parks or BLM or Natl Forest Campgrounds for days and days at a time WITHOUT ELECTRICITY so running my fridge on LP Gas instead of sucking my batteries dry running an AC Battery/Inverter Compressor Motor fridge is the only choice for me. One thing I like about an RV amonia absorption closed system fridge is the lack of moving parts and no bulky Compressor Motor, it just (for electric use instead of LP Gas)  has a small heating strip, be it 12 VDC or 120 VAC powered. Perhaps that explains why the vast majority of RV's on the road  use an amonia absorption fridge that can be operated on LP gas (don’t use up all your limited battery power), or in some cases 12 VDC or  120 VAC (heat strip) versus one that requires 120 VAC and has a Compressor Motor, you just don't see as many of those in RV's.


  FINALLY   As far as proper multiple battery connections, in my opinion as an electrical engineer, the Smart Gauges website I posted above is an excellent resource. I have taken the liberty to copy/paste  one of their findings which indicates the EXTREME IMBALANCE that takes place with an incorrect connection VERSUS the DRASTIC IMPROVEMENT in balance which can be achieved by one easy simple wire swap. NOTE This is NOT ONLY THEORY, but data and results (see below and their article) and is MOST SIGNIFICANT (like day and night) as their research indicates. As I think I mentioned before, sure it can still "work" fine if wired incorrectly and last for years, but if properly balanced it doesn’t take an engineer like me to understand ITS MUCH MUCH BETTER TO WIRE THEM TO ACHIEVE IMPROVED BATTERY BALANCE. In my lifetime electrical engineering career I ran across countless Billy Bobs and Bubbas (you know, the ignorant untrained non professionals who wired their house while drinking a case of beer n by golly it still works and they are now experts lol) and tried to explain that while their method still "worked" the proper engineered method was safer and can work even better.


NOTE their article shows like 4 ways to wire multiple batteries, while the first simple improvement YIELDS THE MOST DRAMATIC IMPROVEMENT IN BATTERY BALANCE.  I STRONGLY suggest anyone who has multiple batteries to AT LEAST make the first simple easy correction if not already in place. Your batteries will thank you lol. Of course, I'm NOT telling anyone how to wire their own RV, feel free to do as you please, I'm ONLY here to help. But, if anyone has hard engineering data and studies and research and measurements (NOT a few mere antecdotes) that can PROVE there's yet another superior method (besides the 4 they show) that achieves even better balance, please take it up with them NOT ME,  I'm sure they would be glad to hear about it.  




From the Smart Gauge Website I provided: That below is the ABSOLUTE WORST LADDER METHOD. Note the severe imbalance (NOT just theory and certainly NOT insignificant ).  Hey, even if it weren't as major, anytime I can make an improvement or do something RIGHT THE FIRST TIME or better, my electrical engineers brain thinks why not do it the better ?????? If you prefer another connection method, that’s fine by me, feel free, I wont argue with your  choice, right or wrong.



The bottom battery provides 35.9 amps of this.
The next battery up provides 26.2 amps.
The next battery up provides 20.4 amps.
The top battery provides 17.8 amps.


So the bottom battery provides over twice the current of the top battery.


                                      NOW  THAT SOUNDS PRETTY MEANINGFUL AND SIGNIFICANT


 I prefer all the batteries  in a multiple battery bank to be balanced, why NOT do it that way when its so darn easy to achieve?




 John T in Indiana   Retired Electrical Engineer of over 40 years and still love it, understand it,  and glad to help my fellow RV'ers. God Bless all here and thanks so much for all your  help and opinions.

Awesome link!

Learned a lot from the easy to understand diagrams.

I only have room for 2 batteris right but the principal is the same.

Thank You!

John- you forgot to mention how much energy an inverter uses to supply the compressor style refrigerator with AC. A 3000 watt inverter draws about 2 amps with NO load- nothing turned on. The surge to start a motor is considerably higher than its running current. The DC current an inverter uses is 10 times the current the AC appliance it supplies (12 versus 120) so the cables going to an inverter  need to be 2 to three times the size your engine starter cables are. A 3000 watt inverter requires 250 amp capable wire or it will get hot.Any inverter should have these specs so make sure to get large enough wire. I have 3 100 watt panels 4 deep cycle 6 volt and a 2500/5000 inverter and the DC wire for the inverter is 0 guage (about 3/4 inch wide)


 Good evening Ron, Sorry, Im not sure what I mentioned and where, I post on so many electrical topics here lol, but I sure know and agree with your good point that any electrical device, be it an Inverter or Converter/Charger IS NOT 100% EFFICIENT as there are heat losses i.e. the pure "electrical" energy you get out is LESS then the pure "electrical" energy you put in, because some of it is lost as heat energy. The device does NOT create or destroy energy ONLY change its form, what goes in comes out one way or another, but not all of it may be in Amps x Volts as some goes to heat losses.

 Of course, watts is volts x amps, so at only 12 volts there's a lot more amps (for identical wattage) necessary then if you were operating at say 120 volts.

 Love sparky chat, thanks for your inputs

 John T

I've found an RV electrical distributor and shop that is nothing short of terrific. Best Converter www.bestconverter.com. I contacted them with an urgent need for a replacement panel/converter and they had it to me at the best price and in time to save our trip. If you need information about anything RV electrical just drop them an email and their tech support will call back in person. This sounds like a commercial but I can assure you I am real. My '95 Itasca Suncruiser worked great for our trip to Yosemite and central California thanks to them.


Ed Atwater

Silverdale, WA




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