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HOW TO: Victron MPPT solar charge controller underneath the street side bed

John E Davies

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Remove the Zamp unit from over the stereo head - two input wires (from the roof), two output wires (to the battery) and the small temperature sense probe wires


Cut off any excess length and then splice the two sets of cables together and secure them. This little cable tie is good for making I.D. labels. Drag the temp sense cable down into the lower compartment, you can sell it with the used Zamp controller. It has a value of about $35 new. Add extra aluminum tape if needed to seal and secure the wall insulation.


The location I selected is a great spot for a big ventilation hole, an air intake for my Lithium Battery Box Powered Vent System , so I needed to add 1" thick HDPE spacers to let air pass through, using JB Weld epoxy, clamped overnight:


I made a mounting plate from heavy sheet aluminum, drilling holes to allow air to get to the bottom of the control unit. I originally planned to use the Oliver installed self reseting circuit breaker, but decided that an inline fuse would be more reliable.




The manual circuit breaker on the output wire is similar to the Oliver one installed across the gap on the DC bus. It allows you to disconnect the solar input by pressing the red button, and it is reset by closing the yellow arm back inwards::


This is the inline fuse, it is very nicely made and has heavy enough wire. It will handle up to a 40 amp fuse, I installed a 30 amp ATC one:






Victron SmartSolar Charge Controller MPPT 150/35 brochur:e 

Victron Charge Controller 150:35.pdf

This is pretty technical, it shows the Zamp roof panel charge curve, I added some data points showing where a lead acid and a lithium (LiFePO4) battery open cell voltage would appear. A lithium battery has a higher operating voltage, so a regular PWM controller is not as effective as a more sophisticated MPPT one that is able to alter both output voltage AND output current. A PWM unit is connected directly to the battery, and it simply switches on and off very rapidly to control the current. It is very crude, but inexpensive and reasonably effective under optimal conditions.


I grabbed these descriptions from solar website, I cannot remember which. It and the following one offer some interesting comments:



Temperature sensing charge control - the Battle Born batteries do not require (nor can they use)  this function, it is built in to the batteries' onboard Battery Management Systems (BMS). However, by installing the optional battery temp probe that connects to my Victron BVM-712 Smart bus, the VictronConnect app will connect using its Bluetooth network with this compatible "smart" device. When I look at the app screen, the battery temperature is shown on both the Solar page and on the Batteries page. That temperature reading is very helpful in monitoring the health of the batteries.

Settings: using the app you can alter a whole bunch of parameters. The important one is the charge absorption voltage. I set it to 14,.4 volts, a little lower than the Battle Born recommended 14.6 volts. I have read that a slightly lower voltage is healthier for those batteries, while not significantly affecting their actual capacity (percentage of charge). This is the same reason they recommend that they are not left continually "cooking" at 14.6 volts from shore power and a charger like my Progressive Dynamics one, it diminishes their life span.


John Davies

Spokane WA


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"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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  • 4 months later...
2 hours ago, Curious said:

Thank you for the detailed explanation and images. That is a very nice image of the back of the PWM charge controller. What did you place in the Zamp PWM hole after it was removed?

Thanks for the very kind words. It was tough to get that particular pic, being buried behind and on the wrong side of that 6” round access hole. I took a bunch of pics with my iPhone, blindly until one came out centered and in focus 😬




John Davies

Spokane WA

  • Like 1

"Mouse":  2017 Legacy Elite II NARV (Not An RV) Two Beds, Hull Number 218, See my HOW TO threads: https://olivertraveltrailers.com/topic/john-e-davies-how-to-threads-and-tech-articles-links/

Tow Vehicle: 2013 Land Cruiser 200, 33" LT tires, airbags, Safari snorkel.

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