Chinook Power System Upgrades

The Chinook was now comfortably parked in the driveway, awaiting the next adventure.  It was time to evaluate the electrical features of the RV.  I have had bad luck with batteries in the past.  Often it seemed that my rechargeable batteries died from lack of use more often that they were worn out.  So, I assumed I could optimize the battery life by keeping the Chinook plugged into shore power.

Since I don’t have a 30 AMP outside receptacle, I bought this “Camco 55223 15M/30F AMP PowerGrip Adapter” form Amazon, so I could plug the 30 AMP shore cable plug into a regular 15 AMP outdoor receptacle outside the garage.

The next step was to replace the plug on the shore power cable, which had started to separate from the cord, and had electrical tape providing a little extra insulation.  I bought this nice “Camco 55283 30 AMP Mini Replacement Male Plug with PowerGrip Handle” from Amazon:

https://www.amazon.com/gp/product/B007HFT034/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

Replacing the Shore Power Converter Charger with a 3-stage controller

I left the Chinook plugged in, assuming the batteries would stay topped off in good shape.  WRONG!  After about a week, I checked the water in the batteries, and every cell was low.  It turns out the stock Shore Power Converter/Charger (Magnatek 7345) was overcharging the batteries, causing the electrolyte to boil off.  This was a common problem from the RV electronics of that vintage.  Modern charging devices have smart controllers that regulate the charging current to optimize charging and protect the battery from overcharging.  These controllers are “multi-stage” controllers, typically 3-stage.  They sense the battery voltage and regulate the charging current based on the battery needs.  When voltage is low (showing below 80% charge), the charger provides “bulk charging”, which sends the full rated current (45 amps, in my case) at the highest charging voltage.  When the battery is charged to 80%, the charger switches to the “absorption” stage, which provides a steady charging voltage with diminishing current, until the battery reaches full charge.  This prevents the battery from overheating (and boiling out the electrolyte).  When the battery is fully charged, the charger will switch to a “float charge”, where voltage is applied at minimal (trickle) current, maintaining the battery at full level without damage to the battery.  The Magnatek Converter Charger was a single stage charger, with performance comparable to Stage 2, which is not only a slow charger, but overcharges when left on continuously, which is really bad for the batteries long-term life.

After some research on the Internet, I found that there are some relatively easy upgrade options that eliminate the problems of the 2000 era Magnatek charger.  Because these chargers were so common, products were developed that were “plug and play”, so they could be installed in the Magnatek box, without requiring any re-wiring of the circuits or mounting of new hardware.  I chose the Progressive Dynamics PD4645 45 Amp Charger Converter (with built-in Charge Wizard).  The wizard is controller microcontroller circuit that produces the 3 stage charging behavior.  I was able to find an open box PD4645 at Amazon for about $160.  The normal price is about $200, but this is really a necessary upgrade for anyone who still has an old Magnatek single stage charger.  There are other upgrade solutions, but this was the simplest fix that required the least rework of the existing wiring.

https://www.amazon.com/gp/product/B002OR2FIW/ref=oh_aui_detailpage_o08_s00?ie=UTF8&psc=1

Installation of the PD4645 was straightforward with the good detailed instructions provided.  The old 7345 electronics are removed from the bottom of the power box, and the new PD4645 electronics are installed in its place.

Only slightly more daunting was the replacement of the fuse card for the 12V circuits with the new Progressive Dynamics card.  The only hiccup in my installation experience was the large 12V charging wire and ground needed to be a little longer to connect to the new fuse card.

 

If I had known in advance, I would have loosened the strain relief and pulled a couple of inches out from under the cabinet, but I had already replaced the electronics and didn’t want to start over.  Instead, I managed to “stretch” the wire enough that it barely made it to the circuit board terminal.  You can see the red wire barely reaching over the back of the new fuse card.  One other minor issue was the size of the refrigerator DC wire (thick red wire coming up from the bottom.)  This wire was a little too big for the terminal, so I separated the copper wire coming out of the insulation into two twisted pieces and inserted the wires like a fork into the terminal.

 

Once the new 3-stage charger was installed, my shore power problems

were solved.  I could new leave the Chinook on shore power indefinitely without endangering the batteries.

The charging system could be optimized further (e.g. running bigger shorter cables) but the PD4645 is already a huge improvement over the OEM charger.  Additional gains would much less significant requiring a lot more work.

Replacing the Solar Charge Controller and adding Solar Panels

Now that the shore power system was upgraded, I turned my attention to the solar panel charging circuit.  For a test, I turned on the 12 V system with only the parasite loads (LP leak detector, smoke alarm, etc.) and disconnected from shore power.  The batteries tripped the low voltage disconnect within a single day!

The single panel was not even supplying the needs of the parasites.  Clearly some improvement was needed.  The Chinook was very high-end in its day, and was an early adopter of solar panel power.  The only problem was the limited technology and high cost of solar components back in the year 2000.  A solar panel was an option on the Concourse, and consisted of a single 50 Watt panel with a single stage charge controller.  The circuit was rated for about 7.5 Amps, but 2 or 3 Amps on a good sunny day was more likely.  The good news was the size and shape of the Siemens 50 Watt panel was ideal for the roof of the Chinook.  I saw an example on the Internet of a Chinook with two panels instead of one, which was probably a special order option.  Since many owners were converting and upgrading their solar system (not the planetary one), I reached out to see if anyone wanted to sell their old panel.  I found a seller and paid about $150, which I thought was a reasonable cost to double the solar capacity without too much fuss.  I installed the second panel directly behind the first and wired it in parallel to the first panel.

The upgrade worked so well, I looked for a way to increase capacity more, without sacrificing roof access.  I found a small flat 50 Watt panel that fit nicely on top of the air conditioner.  Adding the third panel in parallel gave me 150 Watts, without restricting access to the usable roof space.

 

The three panels together can produce enough amps to overload the 7.5 Amp fuse in the original wiring so I replaced with a 20 Amp.  The system could be optimized by running bigger wires, but in real life, the existing wiring is adequate for the three relatively inefficient panels.

The last problem with the original solar design was the stock solar charge controller.  This charger was even less efficient than the Magnatek shore power charger.  It provides only a steady trickle charge which came on when the batteries were low and turned off when the battery was charged, if ever.  I searched far and wide for a replacement controller that would fit in the same location without messing up the wall.  Lo and behold, a controller now sold by Coleman was a perfect fit and costs less than a hundred bucks.   (Perfect fit on the outside, that is.  I did have to grind the cutout about 1/16″ to make the opening big enough.) Here is a link to the Amazon item:

https://www.amazon.com/gp/product/B004RCX91E/ref=oh_aui_detailpage_o09_s00?ie=UTF8&psc=1

The new controller provides a full 3-stage charging algorithm, along with a readout of current and voltage, so you can monitor the input of the solar panels.  The improved controller was just as important as the additional capacity in terms of upgrading the solar performance.

After adding the panels and replacing the controller, the Chinook is now self-sufficient in the driveway for indefinite periods.  I now leave the 12 Volt system switched on continuously, with the solar panels continuously topping off the batteries with absolutely no fluid loss.

This setup also works well for us on the road.  We tend to drive most days, so the batteries get a recharge from the alternator, in addition to the solar panels.  We put the refrigerator in DC mode for driving so we don’t have the propane active for safety reasons.  (Update: Running the refrigerator in DC mode proved to be a huge waste of power.  If we parked for an hour, the refrigerator would deplete the entire battery running on DC.  One day we forgot to switch to DC mode, and were surprised to find that the refrigerator was colder than it typically was after a long drive.  Not only did DC mode drain the batteries, it did a very poor job of cooling!  Now we just turn off the refrigerator while driving and keep the doors closed as much as possible.  Then we plug in or turn on propane as soon as we stop.  We also keep a few bottles of water in the freezer, which makes the freezer work like an icebox when the power and propane are off.)   We have sufficient power to get us through a few nights without hookups.  We could probably go for longer periods, but we like to hook up periodically so we can dump and replenish our water supply, and it’s nice to have the coffee maker available in the morning.