Dual battery install on 2005 GMC Sierra with solar charge controller and power sockets in bed

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May 11, 2013
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Thought I would share some pictures and my procedures for a dual battery install. This is model specific but can cross over to many other makes and models. I have been on the injured list for over a year now and still disabled for the next season or two. This project would normally be a few days at the most. I did it in 15 - 30 minute stints so it took over a month with help from friends with battery lifting.

I'm getting to a point in my life to do some more mellow stuff like off the grid in my truck with some luxury. I have experience riding motorcycles and simple camping. I have a heavy background in my younger years in fabrication, temporary power, and generator field.

First off I think we all can agree that solar and lithium technology is advancing at an alarming rate. As with any project there are 100's if not 1000's of different ways to approach and achieve a project such as mine.

With that in mind I decided to go simple with room to grow in the future. For now I will be doing a basic ACR relay system with a pair of Group 78 AGM batteries fitted to factory trays under the hood.

The heart of the system will be my Mechman 250amp alternator.

First step was to remove the OEM ground system from battery. I have the GM RVC (regulated voltage control) which makes it tricky. I'm doing the big three with 1/0 (actually it's the big 6 depending on how you look at it).

Almost all the 05 -13 GM gas trucks have an RVC (regulated voltage control) system (exceptions are some of the HD and diesel trucks) . It measures ground current and adjusts alternator voltage and amps according to system demands . It consists of 2 wires. OEM grounds from battery are #2 to the block and a #10 to the front crossmember for the headlights. So my do around to get the best efficiency out of the system is to squeeze two 1/0 cables through the regulator. They just fit, barely. I had to install the lugs after sliding the cable through.

What blows my mind is the little dinky #10 OEM wire (orange one on the left) that goes from stock alternator tying into another small # 2 wire to the battery/starter.

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All other "big" grounds including the second battery will be going through a busbar. All battery to ground and power cables are 1/0. Start battery grounds: One to front crossmember, other to busbar. From the busbar to alternator to OEM block location to OEM chassis location, to top of block to aux battery. I spoke with the techs at Mechman and this is the very best way to get the most out of GM's RVC. Bottom line is every ground in the trucks system has to go through the RVC in order for it to work properly to regulate amps/volts to the batteries.

My first issue was a fitting problem with the Mechman alternator. The new alternator is clocked to fit 2 rectifiers (6 phase system) and 12 diodes. So this means the 2 pin plug is relocated in such a way that it hits the throttle bracket. I ended up lengthening the wire and cutting/welding the bracket. 1/16" 6013 rod and my little inverter welder did the trick. My truck is thankfully a manual transmission so I was able to chop out the automatic kick down portion of the bracket. The weld is not pretty having to do it left handed was a pain!!

Before:
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After:
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The Mechman is an outstanding upgrade from the OEM weak 145 max amp alternator. I have dealt with GM's poor alternators for many years. I finally bit the bullet and got one that should outlast what I have been using. For me it was simple math adding up amp pull on all the stuff I am currently and plan on using. The OEM 145 amps is barely enough to keep up with current system demands.

I compromised and went with a lower powered 250 amp model that puts out almost 200 amps at idle. Should be plenty for what I need. The 370 amp one is a beast and needs a smaller pulley to spin it up to get the amps. Mine runs on a stock size pulley. The positive post is in a different location which forces you to change out the wire to reach. The provided lug is 1/0 x 5/16 copper. I saved it but used my own 1/0 tinned copper lugs throughout my project

I also included a cheat sheet for anyone here that want's to know how to properly hook up one of these high output alts. The key is to at least do the "Big Three" and use 1/0 wire for all connections. Even with a stock alternator you will see a noticeable improvement in your charging system. . If you are running a new smart alternator and need high draw items such as winch etc, Mechman can customize an alternator with an external voltage regulator with voltage adjustment knob.

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I did above and beyond and upgraded the OEM ground wire to 1/0 and did one to the stock location at the block (next to starter) and one to the alternator body. Using the busbar enabled me to use a whole bunch of 1/0 to ensure a good ground. Anyone here who has owned a GM truck knows that the electrical issues can be frustrating. Most are grounding issues from poor factory grounds. This pretty much eliminates them.
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ollie

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So now it is decision time on component configuration to the panel. Started off with cardboard. It was a little tricky due to wires and heater core plumbing. I am building this with future repairs in mind.

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I got the aluminum plate all laid out and ready to mount. It took me a few hours just for the fact I'm no longer working in a fab shop. Not bad for hand held jigsaw to cut, hand held cordless drill for holes, and vice to bend. The mounting plate is super solid!! I did some preliminary filing and radius work. Final smoothing and fit after components are mounted.
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Carefully mounted everything to the panel. I broke out my 60 git drill attachment disc and gave it a nice brushed finish. Pretty darn happy with the results. With this COVID crap going on I have had to make do with some connectors by folding up the stripped ends of the wire to get a tight fit in my size 10-12 AWG connectors. It has been a real challenge not being able to go to the electrical shop or hardware store for small bits and pieces.
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ollie

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Well I got er' done!! Let's just say it took over a month to do. No right arm function and bad knees means very painful to work. 15 minutes here and there finally saw it finished yesterday.

I am amazed at the features of the Victron and Blue Sea products. Also I got a really nice stand alone 50 watt solar panel for home charging. I am very happy with the function and projected reliability of this system.

Both the Victron Smart Battery Sense and Solar Charge Controller are bluetooth and interface with each other. It properly charges the batteries and keeps them topped off when truck is parked.

The Blue Seas ACR is fully automatic and disconnects batteries so your vehicle start batter will always have enough voltage to start the truck. I installed the Contura switch on the panel because I don't see myself using it that much. I just keep it in auto position.

So let's talk about the plugs in my bed. I ran #4 AWG ground and power wires directly from house battery to a distribution block in a pocket in front of bumper under the bed. Then have each of them inline fused. I have a marine grade voltage monitor, 12 volt 30 amp marine cig socket, double mini 30 amp Anderson socket, and double USB 5 volt 2.7 amp quick charge sockets. I decided against having a power switch as the parasitic draw is just a few milliamps if that.

A quick note on the Anderson plugs are my configurations for charge vs power sockets. For safety I stacked the Anderson connectors on top of each other for my charge pigtail that comes out of the front bumper. This insures a solar panel cannot be plugged into the Anderson sockets in the back (they are side by side).
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ollie

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For batteries I went with simple group 78 Deka Intimidator AGM start/deep cycle batteries. They are the same battery the Sams Club sells under the Duracell logo. They are manufactured by East Penn Mfg. I got mine through Rock Auto for about 160 bucks each.

The battery tray is a OEM part for the Diesel trucks. All the GM trucks have space for a second battery. They use a much smaller H6 battery. The group 34/78 fits just fine.
 
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Be sure to never disconnect charge controller from battery when it is still connected to a solar panel in direct sunlight.

It might not instantly fry the controller, or it might. The more current it was passing when disconnected, the more likely it gets damaged.

Job well done. The Mechman 6 phase alternators are drool worthy.
Do monitor it for excessive heating(220f+) if Idling with it making 100+ amps for 10+ minutes.

Be sure to regularly retorque the screws compressing the stranded wires in the charge controller terminals.
I really despise this compress stranded wire under screw type of terminal. Even if one has ferrules and the proper crimper for them, the screws still loosen up.
 
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Nicely executed project!

Was the main point of this project to efficiently charge house batteries while driving? I know a lot of people are disappointed to find out that the alternator did basically nothing to charge their RV batteries, even after driving for hours.
 

ollie

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Joined
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Messages
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Be sure to never disconnect charge controller from battery when it is still connected to a solar panel in direct sunlight.

It might not instantly fry the controller, or it might. The more current it was passing when disconnected, the more likely it gets damaged.

Job well done. The Mechman 6 phase alternators are drool worthy.
Do monitor it for excessive heating(220f+) if Idling with it making 100+ amps for 10+ minutes.

Be sure to regularly retorque the screws compressing the stranded wires in the charge controller terminals.
I really despise this compress stranded wire under screw type of terminal. Even if one has ferrules and the proper crimper for them, the screws still loosen up.

Thank you!! The charge controller is hard wired to fuse box and fused at the controller and box. Charge controllers hook up to the battery first and disconnect from the battery last. It's the way they all work as far as I know.

I'm not concerned with excessive heat from the Mechman. My system is not large enough to tax the alternator at idle.

I used OX-800 for the connections and strain relieved all the wires going into the controller. I did not use ferrules as the wire is captured in a small "box" if you will. For the type of wire and application ferrules would not work all that well. Compressing stranded wire under a screw terminal works really well with the right type and size of wire. I always max out the size of wire that will fit. That way you don't have loosening issues.

The wire is very beefy Temco 10 AWG solar wire which is stuffed in and pretty tight even with the screw all the way open. I re-torqued them a few times after couple of heat cycle and they are staying tight.

Nicely executed project!

Was the main point of this project to efficiently charge house batteries while driving? I know a lot of people are disappointed to find out that the alternator did basically nothing to charge their RV batteries, even after driving for hours.

Thank you Sir!! This alternator will have no problem charging both the house and start battery to 80% pretty quickly. It's that last 20% that takes a longer time and where the solar panels come into play. I also notice a lot of RV's using wire that is sized too small. That will really effect charge time and rate as well.
 
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I'd be interested to know how many amps are being pushed to your house batteries while driving if you have an amp clamp to measure the current with. Especially after driving for 20 minutes and the starting batteries have had a chance to be topped off.
 

ollie

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I'd be interested to know how many amps are being pushed to your house batteries while driving if you have an amp clamp to measure the current with. Especially after driving for 20 minutes and the starting batteries have had a chance to be topped off.

That is actually a fantastic idea. I'll have do try that. I have the capability since one of my amp meters is bluetooth. To do a good test I will have to drain the house battery down and then see what I'm getting for charging amps. I already know the trick to pushing more volts into the batteries. With the RVC system you simply turn your headlights on and the voltage goes from about 13.4-13.6 to 14.7-15.3 or so.
 
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If you find that the house batteries are not pulling as many amps as you would like, a DC-DC buckboost type unit like on this page could help immensely. The main problem is the DC voltage drop you get over ~60 feet (round trip) of charging wire. The alternator maybe putting out 14.5 volts at the post, but by the time the current gets back to the house batteries, it may be under 13.x volts due to resistance losses, which will limit the charge rate quite a lot. A DC to DC converter boosts the voltage back up to the appropriate level.

 
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Very nicely executed, wonderful job. im not sure the big amps from the alternator will be fully utilized unless you were to run an inverter and some moderate load off of it. In my travel trailer, the discharged AGM seems to pull up to about 25 amps at 13.5 volts when hungry. any thoughts on a permanent mount for that PV?

ive found the “Lensun” brand PV on Amazon to be good for camper shell top mounting. They are marginally flexible and contour to the mild curve of the shell. I glued them down with silicone caulk and screwed them in on the corners. I noted a couple of days ago a 2.4A charge in daylight with effectively 110W of panels. The charge control I installed does an equalizing charge every 30 days. The truck starts quickly every time. I just upsized the factory battery to an H8, so not as much on reserve as what you’ve got. On days where I might telework from the vehicle with an inverter for the laptop, “don’t care.”

hey I’m sorry about the injury. That’s really hard - you persevered well and I hope you heal up. Don’t work past your limit, it’s tough.

m
 

ollie

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Thank you Meep. My plan is to get a suitcase 100 - 200 amp setup and a soft shell for camping for two or three day stints. I'll be powering up a electric cooler, compressor, laptop, some lights, and a few small items. Not too overkill.
 
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