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12vdc Electric System

January 2005

Electric Power Project

Last year I installed a solar charging system.  Now I'm continuing with the upgrade of our electrical system to include 4 new batteries, relocation of battery compartment, installation of a 1500 Watt inverter, new dedicated battery charger, and another solar panel.  For a review of what's been done so far click here

I'll admit (before anyone accuses me) that I've been a "piddler" the last few weeks.  I've been doing small parts of the project over time rather than working steady on it and knocking it out quickly.  Several reasons for this: 

  1. I do have a business to run!  No, we're not retired, and yes, we need to work to support this lifestyle.

  2. I'm trying to do things as economically as possible, so I wait for good deals, shop for bargains, install one item then see how it works before moving on to the next one, etc.

  3. I don't want the motorhome to look like it's being remanufactured right here on the site :-).  The park we're in doesn't want you to do maintenance on site.  Now in my opinion what I'm doing isn't "maintenance", it's just a little project, kind of like a hobby.  It's not like I'm changing the oil or doing a brake job!  Still, I don't want to be a nuisance to my neighbors by running drills, sawing, etc. all day long.  So I do it in small bites. 

Coming into 2005 here was our situation:

  • Solar charging system installed and working well

  • Two older Interstate 2200 batteries (same size as Trojan T-105)

  • 1500 Watt true sine inverter, but running only small loads with #6 wire (temporarily "installed" where the old 800W had been)

  • Intellipower 9000 converter/charger that originally came with the coach

Here's what I've done so far (as of January 14th)




My Christmas present to myself, 4 new Concorde Lifeline AGM batteries.  These are model GPL-4C, 6 volt, 220 amp hours.  This set in series/parallel gives me 12 V and 440 AH.  I installed them in the forward storage compartment on the driver side.



In this photo, you see the install is in progress.  Still need to tie down two batteries.  Misc parts laying around, etc.  All this has been taken care of now.


I went with the AGMs for several reasons.  Safety, easy installation, zero maintenance, fast charging, 5 year warranty, etc.  They're not cheap.  These were about $165 each (list price is about $235).  I could have used Trojan T-105's instead and saved a few hundred dollars, but then I'd have needed to build a sealed, ventilated compartment, and I'd need to do all that maintenance for the next 10 years (checking water level, adding water, checking specific gravity, replacing pants and shirts ruined by battery acid, etc.).


Note:  Although I installed these in an un-vented compartment some people say this should never be done, even with AGM batteries.  For certain is should NOT be done with standard flooded cell batteries, because flooded cell batteries WILL gas when you charge them.  Here's the document from Lifeline that convinced me this was ok with AGMs:


If you decide to use AGM batteries there are a number of benefits; however, you need to understand one negative.  They can be damaged by overcharging (too much VOLTAGE).  In contrast to their current handling ability (they'll take as many amps as you can throw at them) you can't let their charge voltage get too high on a regular basis.  For this reason you don't want to "equalize" them.  Equalizing is a process where the voltage on a fully charged battery is elevated above normal charging level and held there for a measured period of time.  It's done routinely with standard Flooded Cell batteries, but should only be done with AGMs rarely, as directed by the manufacturer.    


No, they're not as sensitive as gells.  You can ruin a gel cell battery in a day!  But if you spend a bunch of money on AGMs and just treat them like regular flooded cell batteries you'll shorten their lifespan.


Maybe more important (and potentially dangerous too) you may cause them to "gas" by overcharging (over voltage).  This is an especially bad thing if you installed your AGMs inside the living space, or in an un-vented compartment.  They're not supposed to gas under normal conditions, but if you overcharge them they may.  Yes, Lifeline batteries are the safest batteries made, but you should still be careful


 I'll refer you to the links below for general information on charging stages, bulk, float, etc.  :


Links for information on RV 12 volt systems, Batteries, Chargers, etc.


Overall RV 12 volt systems


Battery Types


Battery Charging





Since I bought the "top of the line" batteries you'd expect me to have a Xantrex Prosine 2.0.  Not so.  Those are about $1900 and I have to conserve money someplace, so the inverter is one of the areas where I'm going "bottom fishing".  I researched and purchased an AIMS 1500 pure sine inverter.  You can buy them several places, but I used  Unlike other stores they actually answered the phone, were knowledgeable of the product, and were pleasant to work with.  (Added note:  I no longer recommend the AIMS inverter.  Keep reading to learn why)


So I paid about $475 for this inverter (made in Taiwan by the way, NOT in China).  It seems to be working fine so far.  I'll report back later on its durability. 


I didn't buy the remote control for $24.  Instead I bought a momentary contact switch from Radio Shack for $2.95 and a 12 foot phone cord for $3.75 and made my own.  It has no indicator lite to tell me the inverter is running, but that's OK, I saved almost $18.


As the following photos show, I installed the inverter with a 200 amp inline fuse and a PERKO switch as a cutoff. 


Added Note:  This inverter has failed and was replaced with a different inverter. 




Notice the fuse and fuse holder.  Here's where I saved some money again.  A Class T fuse and holder cost at least $65 (at West Marine in Key West, FL they were about $100 for the set!).  I decided to go with an ANL fuse instead.  The fuse holder was about $50 and the fuse $18.  So, I bought two 1/4 inch power posts for $7 each and installed the fuse between them.  Total cost $32.  Yes, it's a slower blow, but a 200 amp ANL will give me adequate protection.  Yes, I could have ordered on the internet and saved even more, but I didn't want to wait for delivery.




Link to more information on Inverters



Buying from the web


While on the topic of buying from the web here are a few comments:  I buy from the web often.  I've been buying and selling on the web for a lot of years (eBay etc.) and I believe you can get some great bargains there.  However, sometimes I'll just not want to wait an extra week or so for the parts, so I'll buy locally.  Also, when it's a project like this one where I'm "feeling my way" along I like to look at and touch the parts.  Easier to return local too if you get the wrong thing. 


In the future, if I rewire this whole thing (and I might do that) I'll likely buy online and get top quality wire/cable for not much more than what I spent on the cheap stuff here.  And that brings us  to wire and cable...


Wire and Cable


Purists and perfectionists will gasp and scold, but I used cheap wire from Home Depot for most of this project.  Yes, good old stiff-as-a-broomstick THNN copper stranded wire.  Several reasons for this.  First, I was making several runs of 3, 5, 10 feet etc. and didn't know exactly how much wire I would need.  AWG 1/0 at Home Depot was about 95 cents a foot.  In contrast 1/0 Boat Wire at West Marine was about $7.00/ft.  I could have bought welding cable for about $3.00/ft. back in Tampa, but couldn't find a source here in KW and didn't want to drive back to the mainland.  If I do this all over again, I'll know exactly what lengths of wire I need, and I'll buy bulk wire, bulk connector ends, etc.  With careful shopping online, I could likely do the whole job with Marine Grade wire for just slightly more than I did it this time with the cheap stuff.


Here's a interesting discovery.  When budgeting I had failed to consider how much cable ends, fuses, etc. would cost me.  If I add up all the miscellaneous parts (cable ends, fuses, fuse blocks, etc.) it comes to about $200.  Surprise! 


A note about crimping big cable.  Some will say it needs to be soldered too.  I've talked to several battery people who say that at large sizes (#4 and larger) a good crimp is stronger mechanically than soldering.  Also soldering big cable requires a lot of heat and can easily melt the insulation.  So, crimp it good, and use a good shrink wrap made for battery cables (they are lined with hot glue) that will really seal the connection in. 


If you're near a West Marine, Batteries Plus, or other battery or boating supply, ask them if they have crimping tools for customer use.  West Marine in KW does.  They have bench crimper, vise, hacksaw, cable cutters, etc. and as long as you're buying some parts from them they'll let you use it.  I carried in my own cable and bought a few items from them (fuse, power posts, a couple of connectors, etc.) and they were very happy to let me use their crimper.


One more wiring comment; a benefit of moving my battery bank is reduced wire length from my solar controller.  I was running #6 wire about 30' from controller to batteries, now it's about half that, maybe 15'.  This is good, and will reduce voltage drop since I'll be pushing more amps when I add a 3rd 120W panel in the next couple of weeks.  Better yet would be #4 wire, maybe when I upgrade at a future date.


Battery Charger


My coach ...for those of you who don't know, that's what we RVers call our Motor Homes ;-) was built in 1995 (1996 model) and came with an Intelli-Power 9000, 65 amp Converter/Charger.  Nice size charger you'd say?  Well, all is not as it seems.  These old converters (Intellipower, Magnetec, etc.) may be RATED at XX Amps, but don't provide that amount of current to your batteries.  They were intended to provide DC voltage when you're plugged in, and to keep your battery charged.  I put a clamp-on DC Amp Meter on my battery cable.  I never got more than 14 amps measured charge current, and usually closer to 8 amps when batteries were around 80% charged.


I researched chargers online and settled on an Iota 55 amp charger.  Iota web site  Then I Googled to find a good price.  I paid around $170 for the charger including shipping.  Not bad.  Iota Chargers are also sold by many other outlets, including Arizona Wind & Sun and


This charger will NOT replace my old converter.  Why you ask?  One reason is that I intend to use it as a dedicated charger only.  The old converter will continue to do a fine job of making DC when we're plugged in to shore power.  Also this charger's float voltage is 13.6v and that's too high to float my AGMs.


Continued below...  To read about our Solar charging system click here.  And here's a Link to More Information on Battery Chargers


Update, January 19


Battery charger is installed.  Project is "operational" but still a few "loose ends" to tie up.  Need to install plywood base under inverter and bolt it down.  Also need to run a 120vac line back to the shore power jack (so we don't have to keep using an extension cord) and tidy up cables, use a few wire ties, etc.  Here are pics of the system:



Here's the "power center", takes up one large compartment



Manual control of battery charging


You'll notice that I didn't order the "smart charge" controller to go with this charger.  That's because it doesn't have an appropriate setting for my AGM batteries.  So I'll manually control the charging of my batteries by using this bulk charger when I'm cycling the batteries on a regular basis.  This will usually be dry camping, and using the generator to augment solar on cloudy days or when usage has been heavy.  There are several good charging systems that can be set to automatically manage AGM batteries, but they are much more expensive in a comparable size, and I'm trying to save a few hundred bucks. 


When I'm boondocking (camping without hookups, no electric power, water, etc.) I'll be using the batteries continually.  They will never "float", so my Solar charger will be set at 14.2 volts (with automatic compensation for battery temperature).  When I run the generator, the Iota charger will also be set to 14.2 volts.  


Update on LED Lighting

January 21 2005


Last year we purchased a variety of LED lights from SuperBright LED's (link to earlier story).  I promised to report back our findings.  Here's what we've discovered:


Where LED's work well

  • Task lighting, such as a reading light.  They draw very little current, stay cool, and give plenty of light to read by when aimed directly at the book.  We've found a 24 LED or 30 LED bulb works best.

  • As a "Night Light".  We have a 24 LED flat PC Board "bulb" in a standard fixture where our hallway connects to the kitchen.  This we leave on all night and it's bright enough so we don't trip over the cat. :-)

Where LED's don't work well

They're very poor for general lighting.  Why are they good for reading, but not general lighting?  Because general lighting requires broad, overall illumination.  In contrast, a reading light is focused. 


Here's some further reading on the subject from They had previously recommended LED's on a broad scale, but after additional research now only recommend them for specific tasks.  Long but worth reading

Greatest Surprise - and a big disappointment 

We had expected very long life, since it is claimed that LEDs will burn for 20,000 hours or more before failure.  I'm not sure if it's a quality control issue, design issue, or what, but we've experienced failure of 2 out of the 5 LED "bulbs" that we purchased in less than 3 months ago.  In each case several individual LEDs have gone out, usually in groups of 3.  First it was our 30 LED bulb that started to fail after only a month.  Now our 24 LED model has 5 that don't illuminate.  They have a 1 year warranty, and SuperBright did replace the 30 LED bulb (we're sending the 24 back next week).  Given their high cost, this failure rate is a big disappointment.

So, what are we using for lighting?  For general light we bought three Thin-Light brand 16w DC Fluorescent fixtures for the kitchen and living room areas to replace 2-bulb std 1141 fixtures.  Now we get double the light, with fewer total amps. Another change we made in the bedroom was to replace one of the 1141's in each double fixture with 67's. The 67 draws about .6 amps, about 42% of the 1141. Nice soft light. We can set them for 67's only when boondocking, and both bulbs when hooked up.


Another update, by the end of 2005 all the LED's purchased from Superbright, including the warranty replaced bulbs, had failed.


Update:  The reason for failure was likely high voltage from battery charging.  The LEDs weren't suitable for an application like this.  Installing with a small voltage regulator at each fixture would have probably worked.


Electrical System Project Update


AIMS 1500 inverter failed, replaced with Samlex S1500


Several months ago our "bottom fishing" experiment with AIMS inverters came to an end.  I was trying to save money by buying a really low-end inverter.  It never performed up to par.  It had an unstable frequency output, interfered with the TV, wouldn't run the digital display or touchpad on the microwave, etc.  Eventually it just died.  So, rather than continue the experiment I returned it on warranty to and upgraded to the Samlex CoTek S1500 pure sine inverter. 


The Samlex was $650, about $175 more than the AIMS.  It has a clean, stable output, it's smaller, and it works flawlessly.  The only thing that would make it better is a sealed case (like a marine version) so I wouldn't have to worry about opening the bay in the rain.



If you want to learn more about 12v power for dry camping visit here:  RV Electrical Power for Dry Camping