Quote:
Originally Posted by Keith Wire
Hi Rick,
You said you were doing this one...
Could you explain how you are increasing the Tow Vehicle voltage from 12 to 24 volts?
I am assuming there is is a DC to DC Converter and you have tied it in the charge line after the Bargman Plug so the converter is located on the TM. Can you share the make and model of the converter you are using?
....
Thanks, Keith
|
Because the Booster can draw almost 40A on the "12VDC" input terminal (if the Solar Controller is charging batteries in "Boost mode", with high output current capability), we locate it inside the the TV. These provides two advantages. #1, current through the Bargman and TV wiring is cut in half dramatically reducing Voltage Drop and Power Loss in the TV and Bargman "Trailer Battery Charge" wires. #2, it allows the Driver to control use of the Booster, versus use of the genuine Solar panels, with the flick of a switch in the dashboard. (It's switchable at any time, including driving down the Interstate.)
Don't forget, a Solar Controller is
mandatory to avoid blowing batteries and TM equipment (which will blow up if the "24V" is put directly into the batteries or DC Distribution). The purpose-built Redarc and Ctek units contains both parts - an MPPT Solar Controller, and a Voltage Booster. They are installed in the Trailer only, and they cannot be switched off from the TV cabin. The Redarc and Ctek "trailer-only" devices pull up to 25A down the wires Bargman wires, causing much higher I-squared-R power losses.
So Built-from-scratch is better, if you have a high-power Solar configuration to use when the sun shines brightly. (I've got one). Another TM owner and I have WIP on this conversion, making this same upgrade on both of our Trailers (and Tow Vehicles). We put the 12/24 Converter in the Tow Vehicle, under the control of a switch in the dashboard. The switch scenario goes like this:
- Dragging any other Trailer: Leave the switch off (run the Bargman at "12V").
- Pulling the TM in excellent sunlight: Leave the switch off (TM Solar Panels do the work).
- Under clouds or Night Driving: Turn the switch ON.
- In a Boondock campsite, when Solar Panels haven't been helpful enough: Connect the TV Bargman to the parked TM, turn on the TV, then idle for 20-30 minutes with the switch ON. (Recharge the batteries in camp, using the TV as a 24VDC "generator".)
Parts In the TV:- One switch, which will carry only a low current. I will use this this one: http://www.ebay.com/itm/141816846277
- A high current, 4-pin Relay (disables the new wire from the battery, whenever the ignition isn't "ON"). This one is overkill, but includes an indicator light: http://www.ebay.com/itm/182033514542.
- Two high curent, 5-Pin Relays (12V coil). Like this one: http://www.ebay.com/itm/131374818673. There's two more in the Trailer, so maybe buy a 5-pack. (We only need 40A capability, but I love having the indicator lights.)
- And of course, the Voltage Booster itself. You want the maximum output current capability of this one to be AT LEAST AS BIG as the maximum input current of your Solar MMPT, so that it doesn't become overloaded and "fry" under high demand. This one is a good choice for "20A" Solar Controllers: https://www.ebay.com/itm/1-DC12V-Ste...l/332164334824. KL Pauba chose this one, and it also works: https://www.ebay.com/itm/DC-Converte...t/323331462886.
From the battery, a fat wire (#8 or bigger) goes through a new fuse or Circuit Breaker at 40A. That +12v wire continues through the power leads of the ignition-controlled Relay, and then continues into the first of two Relays being controlled by the "Zombie Switch". (The input "control" leads for both of these 5-pin Relays are wired together, from "Zombie Switch" output.)
Relay 1: the "power" output from the ignition-controlled Relay comes in on terminal 30 (This is #8 wire.) The coil "pulled in" (switch engaged) output lead (terminal 87A) goes to the Booster +12V input (this is also #8 wire). The "inactive coil" output lead (terminal 87) goes directly to the matching "inactive coil" terminal on the second Relay (terminal 87). This wire can be #10.
Relay 2: The "inactive coil" lead (terminal 87) connects from Relay 1. The +24V output of the Booster comes in on terminal 87A. Terminal 30 (the common "power" connector) connects to the Bargman "Trailer Battery Charge". These wires can all be #10, because the current from the "high-power" connection" has been cut in half (i.e., when the voltage was raised by the Converter.)
All 5 grounding leads ("control -" from all 3 Relays, plus two leads on the Booster device) go to TV frame ground.
When the ignition is on, but the Relay coils are not yet powered up from the "Zombie Switch", "trailer battery" current routes through the short "jumper" connecting the #87 terminals - bypassing the Booster. Trailer Voltage is "12V" (actually, a bit more than 13V at most times.) But when the "Zombie Switch" is turned on, the current path goes through the Booster input and output "+" terminals -arriving into the 2nd Relay at 24V. - - - - -
Parts in the Trailer:- A 4-pin (or 5-pin) Relay, with 24 Volt Coil. (Hint: Car alarms use these.) http://www.ebay.com/itm/380650078279
- * Two 5-pin high-current Relays, with 12V coils (same as used in the Tow Vehicle).
- A Solar Controller - MMPT is much better than PWM in this application.
In the Trailer, a special Relay is used to detect 24V, and it switches the other two "regular" 5-pin Relays. (In roughly the same way that the "Zombie Switch" controlled the two 5-pin Relays in the Tow Vehicle). This one:
http://www.ebay.com/itm/380650078279 It's a 5-pin Relay, but we use only 4 pins: a low-current jumper from the Bargman wire end (behind the Fridge); a coil "Ground", and a 12V power lead from the battery or load center into terminal 30.
According to the painted diagram on this one, we connect the switched 12V output power lead to terminal 87 (not 87A). This becomes the Coil "control" input for the other two Relays.
The 2nd Relay is a high-current 5-pin Relay, taking power from the Bargman (terminal #30) and switching it to either the Load Center on terminal #87 (coil inactive, Bargman Voltage running at "12VDC"), or a short "jumper" leading to corresponding terminal on Relay #2 (coil active, pulled in: #87A on both Relays).
The load center wire (on terminal 87 of the first Relay)
MUST also be shared with Breakaway Switch input power lead - the third wire which used to be in a wire nut with the Load Center <--> Bargman "Trailer Battery Charge" connection.
The Third Relay in the Trailer is similar to the second Relay in the Tow Vehicle - it chooses which of two "input" wires (87A or 87) will be connected to the #30, which is the "Solar Panel +" Input on the Solar Controller. One connection is from the Bargman, the other is from the genuine Solar Panels.