UMAX Ultimate RV Project - Electrical

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    Electrical System - Page 2 of 3

    An RV's electrical system is the heart of the RV in terms of comfort and having all the luxuries of home so we've put a lot of thought and testing into the sub-systems.

    The electrical system is based around a 4KW/8KW Peak MPPT Integrated Power System coupled to a 150AH 48V battery bank.

    4000 MW Electrical System 

    This system has the capacity to supply 15A  - Click on images above to enlarge.

    Main Cabin Switches

    Located in easy reach above bed.

    Cabin Main Switches
    The reason the below can be switched off is they can be too bright for sleeping and why use power lighting them if you're not in the cabin.

    -- There is a dimmer for the main downlights beside the switch.

    2 x volt meters True battery status is under no-load so while the green bars may go down wile say making coffee they should go back up afterwards. 

    660W Solar

    660W RV Solar Panels


    Charging 48V Battery Bank via Truck Motor Mounted 48/56V 5KW Generator 

    48V Generator mountedPrestolite_48V_alternatorMounted in place of bus A/C compressor (system removed) on truck motor.

    Use the truck engine to top up the 48V batteries or save the batteries during very heavy loads, very useful in winter. The engine does not use much fuel at 1000 RPM. 
    You avoid having to mess around with a generator.
    A factory modification was fitted to the generator (new regulator) increasing the maximum voltage to 56V as you need more than 48V to charge the bank.

    56V x 90A = 5040W (5KW) this would be the maximum possible, at "idle up" low engine speeds a lot less, but still more than enough for our needs.

    A0014420JB_curve Note graph is alternator RPM, not engine. We have taken this into account when sizing (54mm, 6 groove) ALT pulley.

    The more you deep cycle batteries the quicker they will need replacement, now you don't have to when the sun refuses to peek out from the overcast.

    Most people don't seem to mind a "car engine" running (or don't notice) but they do tend to get miffed over generators. We suggest that you start the engine to use loads 2+KW like the High Power Microwave for extended periods) without stressing the 48V batteries. 
    -- A 5KW generator allows you to run the engine for relatively short periods to get a massive charge into the 48V batteries.
    -- Especially helpful if camping with little sunshine. (Tip: Heat water while driving, leave AC fan on too if hot.)

    The 150AH (4 X 12V) 48V battery bank can cope with massive current drains, however it extends their life if you avoid this as much as possible. Not deeply draining AGM batteries (using the 48V alternator) saves money in the long run, the amount of diesel you'll use is minor.

    Faster Idle Speed for 48V Charging

    Both the 12V and 56V alternators perform a lot better at a higher RPM than idle.

    To get the RPM to the optimum for the 48/56V system turn on the truck's AC system. There is an override button so you won't actually be using AC, it tricks the trucks computer increasing the RPM. We found this to be the easiest way to get the RPM needed.

    Sunny or Driving a lot?

    You may not need the 56V generator so there is an isolator switch to the left of the main inverter. (Tip: Heat water while driving if using 48V alternator, next morning there will still be heat in the system so less load on the batteries, leave AC fan on also..)

    There is no point "generator" charging if there is a lot of sun. My advise to start to motor (idle up speed) for very heavy loads still applies regardless (the generator can supply several thousand watts to save the battery cycles).

    You may be thinking why mention 48V and 56V?

    You need more than 48V to charge a 48V bank. Peak or bulk charge voltage can reach 58V for a short time then drop back to the float voltage of 54.1V.

    Under no load around 51.9V is 100% charged.

    The 5KW alternator has been factory upgraded to 56V.


    PC Application

    IPS (Main Power Unit)

    Solar - Inverter status

    The same information and settings are available via the control panel on the main unit (red box) as on the PC application.

    The app allows you to change system parameters if needed, changes can also be made via the control panel on the IPS unit.

    Checking the two digital voltage displays inside the cabin (can be turned off via switch in switch bank below it) is the easiest way to keep an eye on state of charge. 

    Stay in the green as much as possible to extend battery life, avoid red and if possible stay out of the yellow zone too.  It's cheaper to spend a few dollars on diesel running the engine (thus 48V alternator) than replacing batteries because you were deeply discharging them too often.

    Example image above is mid afternoon, clear sky. If no charge is required and there is little load on the system the output from solar will decreases.
    Solar needs a load to produce maximum output, put another way you won't see 200W (etc.) if you don't need it.

    Best results are RV side onto the sun, so you'd put the door side parallel and use the Awning to shade the windows. (Put the RV key in a different place to prompt you to remember to retract the Awning before moving off).

    The Power System is designed with redundancy in mind

    If the inverter/solar or alternator system fails you can get by on the backup.

    If you've forgotten to turn off the 2KW inverter and flattened the cab/truck main battery (2KW inverter needs the motor running if your using it under heavy load) then you should be able to recover by pressing the button on the "Projecta" 150A switch to jump start from the main 150AH house battery which as a good rate of solar charging also.

    If you've flattened the lot we have a plan for that too, you can wait for some sun to charge the batteries or use the supplied Anderson jumper leads.

    Anderson Socket

    Located behind outside shower where you'll also find an isolation switch. 

    Note: If you want to use the 48V alternator while parked engine idle speed should be increased by turning on cab A/C. (Slow idle will not help much, a few hundred RPM makes a big difference to generator output, the optimal ratio takes into account normal operating RPM so as to not over-speed the generator. Bearings were also changed to higher speed versions.)

    There is a push button override switch if you don't require cab cooling (the normal situation).

    For very heavy loads you can increase idle speed to say 1100-1200 RPM via adjustable accelerator shunt.

    Backup Inverter

    A 2000W 12V backup inverter (white control box pictured below) is available for 240V power.

    The output can be routed to a point inside the RV.

    The engine should be running for higher loads (coffee maker etc.) because 10A @ 240V would draw around 160A at 12V this is the reason its connected directly to the main truck battery.

    You could flatten the truck's battery if you draw too much without the engine running.
    -- Truck 12V alternator can supply up to 200A.
    -- See jump start button.

    Tip: Leave engine running for a few minutes after use just to top up the truck battery.

    Also check out "faster idle for charging". 

    Switches and gauges  

    For high loads it's safer to have the motor running before turning on the backup inverter, and leave on for a few minutes afterwards to top up the truck's 12V system.

    Cooling the Power Systems

    The boot area containing the "power station" is positively pressurised by 2 X 240V fans when the temperature reaches the setting you've chosen on the digital thermostat.

    Set cooling fans temp

    Dual exhaust grills (with filters) are built into the boot lid.

    The filters are for cases when air may flow in the reverse direction (fans are off). If you were travelling very dusty roads it would be best to have the thermostat set such that the fans were on and achieving the positive pressure to keep all dust out.

    This dual fan system will also keep air flowing through the RV so on a hot day you can adjust the setting with that aim in mind if you'll be away from the vehicle leaving it locked.

    Tip: Park nose or tail into full sun to lesson cabin heat load or door side into setting sun with awing deployed to shade the sun from the windows.

    A note about the 48V Solar Panels & Fans and how to power off the IPS

    Once the system senses solar input, even a very small amount, the fan in the main inverter (IPS) will power up. If this is going to annoy you at 6AM on a sunny day then you'd simply trip the solar input breaker the night before. 

    If you need to power off the IPS, first trip all 240V breakers (unplug shore power too), then trip the 48V solar and finally the 48V battery bank.

    Note: Engine will still charge the batteries unless you trip the 48V alternator breaker.

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    Centre is main inverter, you can see the 12V house battery (48V bank is to the left out of view).

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