My "Stockton" Boost Device Installation

[klpauba]

In honor of Rick Stockton (rickst29), I'd like to share my installation of a device that he designed. It converts a TV's output going to the trailer (at the Bargman connector) to 24 VDC for more efficient charging of the Trailmanor battery (or batteries). What I'm showing here is half of the system -- the other half I'll share in the next few weeks as it requires a few modifications to the trailer. Rick's original discussions can be found by searching the forum for "boost" and using "ricks29" as the member id in the "advance search" link above. Better yet, just read all of his posts -- you'll learn a lot!

This system allows me to decide whether to charge the batteries more effectively from my TV (if it's cloudy or at night while I'm traveling -- or even at camp) or from my solar array with the flip of a switch.

I wired the DPDT relay so that, when the switch is in the "off" position, 12 VDC would be supplied to the Bargman connector -- for when I occasionally use other trailers where the higher voltage isn't wanted. Here's the schematic of the boost device, DPDT (Double Pole Double Throw) Relay, fuses and control switch I've installed in my TV -- a Chevy Traverse.

TV-Wiring--Scheme-B.pdf

NOTE: Items in bold below have been edited in light of the undersized 280W voltage doubler recommended before.

The voltage boost device can be found on ebay using the search string "voltage doubler 480W" (or "540 W" especially if you plan to use LiFePO4 batteries but you'll have to also change the detector relay). The relay can be practically any one that has a 12 VDC coil and DPDT contacts. Here's a photo of the components mounted on a small sheet of aluminum plate along with a close-up of the relay I selected:



In case I decide to get a new TV in the future, I decided to use some insulated disconnect terminals when I tapped into the original wire that supplied power to the Bargman connector. In this way, I could disconnect the boost device, remove it from the TV and plug the orginal wires together as if nothing had been installed before. Here, are the yellow disconnect terminals where I've spliced in the input and output from the relay (terminals 6 and 5 on schematic):




Before installing permanently in the lower console, I wired everything up for testing:



The fuse block in the upper right corner I added last year for an entertainment system. A wire that's switched on with the ignition drives a 12 VDC 30 Amp relay to energize the fuse block. The 1A fuse in the schematics protects the small white wire from the "boost" switch that energizes the relay. The large white wire is the ground wire and one of the large red wires supplies 12 VDC and the other runs to the Bargman connector.

Here's the voltmeter's reading when the "boost" switch is off:



And, when it's on (the control switch has the yellow LED shining):



I plan on finishing up the trailer wiring that will hook the supply line from the Bargman to the input of the solar charge controller. I will then be afforded more freedom in the way I keep my batteries charged for our boondocking excursions.

Feel free to ask questions and offer suggestions.

Thanks!

[klpauba]

All that's left is to wire two more relays in the TM that will automatically switch to charging from the TV if 24 VDC is present or, if not, from my (soon to be installed) solar panels. Here's the wiring diagram I've created for my battery charging systems:

Battery-Charging.pdf

[klpauba]

The Bargman "12V" line is disconnected from the TM electrical system and is only connected to the input side of the MPPT solar controller. When boosted by the TV to 24V, it appears to the MPPT as a 280W solar panel and it charges the battery more effectively than using 12V.

I thank you for mentioning it though. I'll modify the schematic to make it clear that the wire from the Bargman is disconnected from the other 12V wires (in the area located behind the refrigerator).

Originally Posted by Padgett

Mist admit I'd be concerned about putting 28vdc on the TM 12vdc system. 15v ok but not 28.

[rickst29]

Originally Posted by Padgett

Mist admit I'd be concerned about putting 28vdc on the TM 12vdc system. 15v ok but not 28.

I will prepare and attach a corrected diagram later tonight. There are three Relays within the Trailer. The "Detector Relay" power circuit is connected to a 12V Trailmanor lead, un-switched. On the output side, this lead becomes the "control circuit" for two other 5-pin Relays (with 12V coils), and then connects to Frame Ground - creating the voltage differential to activate both coils when 12V is present on the "control" wire.

The Bargeman "battery charge +" input is connected to both the "Detector Relay" Control, AND to the common POWER input of Relay "1A" (the missing Relay). When 12V is not present on Relay "1A" coil control, the common POWER lead is connected to a fused battery link. (The TM thus has a direct connection from Bargeman to Battery, through a fuse). But, when that Relay is switched - the alternate "POWER" path switches into the other connection.

That connection hooks into the second Relay, on the "connected when coil IS powered" switched power lead. As Kevin's diagram correctly shows, the "common" power lead goes to the Solar Controller, and the lead "connected when Coil IS NOT powered" goes up to Solar Panel "output "+".
- - - - -
When the GMC Tow Vehicle isn't connected, and when the GMC (or other "TV") supplies only 12-15 volts on the Bargeman "Battery Charge +" power lead, the "Detector Relay" doesn't connect the 12V TM supply line to the "control circuit" output wire - the "control circuit rests at zero volts (TM Ground), and the 5-pin Relays Coils are not powered. The "unpowered" State is: Bargeman "Battery Charge" (Shared lead) connects to a battery terminal through Relay "1A", and "Solar Controller PV +" (Shared lead on Relay 2) connects to the genuine Solar Panels.
- - - - -
But now Kevin flips the switch. The Bargeman Voltage goes up to 24V, and the "Detector Relay" makes the connection, putting 12V power on the "coil control wire". Relay 1A disconnects the battery (activating "24V Bargeman Power" into Relay 2); and Relay 2 switches the Solar Controller "PV + input" from the "genuine Solar Array", over to the "24V Bargeman Power" connector.
- - - - -
For a very short time (while the coil of Relay 1A gets "pulled in"), the battery might be connected at 24V. But the battery can absorb that power for a short time. (It is therefore important that Relay 1A be reliable.) On Relay #2, it is also possible to have "24V Bargeman power" connected to Solar Controller input for a short time, before high voltage actually becomes present on that wire. Zero input power results at the Solar Controller.

Because the hold-in Voltage within a "24V" Relay, after it has switched, can be less than 12V, the Tow Vehicle switch (back to "12V mode" might not cause the TM to switch back. (The genuine Solar panels don't get connected, and the Solar Controller receives only "12V" from the Tow Vehicle.) To force switch-back, just disconnect the Bargeman Adapter at the "TV" hitch for a moment, and then plug it back in. (Or simply turn the "TV" off for a moment.)

[klpauba]

@rickst29, you are correct and thanks for taking a look ... here's a corrected schematic:

Battery-Charging-REV2.pdf

[rickst29]

When we "cut" the original Bargeman-to-Load-Center connector, we need to keep the Break-Away powered from the battery or load center. An older diagram shows this a bit better:
The "12VDC Bus" connects to the Load Center using one of the 30A "DC supply-side" terminals (reaching the "Battery +" terminal through the existing battery connection); it could also be powered by running a fused line back to a "+" Battery Terminal.

I did not implement exactly as show in this diagram either. In my 2619, the "Bargeman 14/28 VDC" wire goes all the way to a project box beside the MPPT Solar Controller (it's about 15 feet long and it's contained in wire wrap, for protection and also to prevent confusion with anything else). All three Relays and related wire connectors are within the project box. I used the old lead for "Bargeman Battery +" to reach the load center to directly connect the Load Center and Break Away.

[Larryjb]

I'm wondering how taxing this system would be on the stock alternator of the TV? I haven't looked into it beyond this thread, so it could be that my concern is not well founded.

[rickst29]

Originally Posted by klpauba

In honor of Rick Stockton (rickst29), I'd like to share my installation of a device that he designed. It converts a TV's output going to the trailer (at the Bargman connector) to 24 VDC for more efficient charging of the Trailmanor battery (or batteries). What I'm showing here is half of the system.... <snip>

A couple of issues WRT to current-handling in your diagram. Here is a better Diagram, with two fuses. Just like a household circuit, the power consumer at the end of the circuit (the MPPT controller) needs to have the lowest current draw; a fuse have the next lowest "current capability", and everything in between (Boost Converter, Wires, etc.) needs to be more capable. We actually want two fuses, and the setup requires #6 wire for 4 wire segments under the hood.

The "voltage doubler" Boost Converter (or, in my case, a regulated 24V-output Boost Converter) needs to be BIGGER, in power and current capability, than the maximum demand which the MPPT controller may create. A Trailer Battery String (12V) with a 20A output limited MPPT Controller could deliver up to 20A @ 14.4V for a short period.(288W delivered into the batteries.)

But the MPPT controllers are not 100% efficient. If we SWAG 90% efficiency, we need to provide about 320W of input to meet the demands of that Controller. Next (working backwards, to the Boost Converter): Voltage drop occurs on all the cables. From a 24V Booster like mine, in the TV, Voltage drop occurs on all the cables: With wire losses of (perhaps) 1.5V, 22.5V * 14.2A is required to satisfy the Controller. Another 20-30W of Booster load must be provided at the Boost Converter,

We're now at 350W (Boost Converter Output). The Boost Converter also has an efficiency cost (perhaps 10%), and should probably not be run at more than 80% of capacity. Applying the 80% capacity rule first - we need a Boost Converter capable of at least 460W. Finally, applying the 90% efficiency SWAG second, we almost 490 watts of power coming into the device at ~13.5V. FOR A 20A MPPT CONTROLLER, THE BOOST CONVERTER MAX POWER MUST BE 480W OR GREATER, NOT 280W. FOR A 30A MPPT CONTROLLER, THE BOOST CONVERTER MAX POWER SHOULD BE 540W OR GREATER, NOT 280W.

This becomes the power demand on the "12V" circuit under the hood. #8 wire, fused at 40A, would barely handle this. It should be built with #6 wire, fused at 50A, and with a more capable Relay (I used 80A DPDT Relays everywhere.) "Boost" Output, running at about the current of the Input, can be #10 wire fused at 30A, as your TV was originally equipped.

Summary: You need to have TWO fuses of different size, a much more powerful Boost Converter", than we indicated in post #1, and #6 wire for the high-current legs from battery into the 50A fuse, from fuse into the Booster input terminals (+12V), and from Booster "Input Ground" back to battery "-" (or the frame),.

[rickst29]

Since the "little booster" overheated and went to heaven at the the worst possible time for you, I upgraded my own booster to this one. And I've run it hard with no problems: https://www.ebay.com/itm/DC-12V-Step...-/362154954611. This is adequate for an MPPT solar Controller with 20A maximum output.

new edit with full explanation, 5/7/2019: The "power draw" on the Booster actually occurs from the MPPT Controller, and not the batteries. Working upstream from a "20A maximum output current" controller, running Boost mode @14.6V (those GC2 batteries can be charged higher than 14.4V), we have about 290 Watts from the MPPT, into the battery string. On the input side of the MPPT, with efficiency perhaps as low as 93%, it will try to demand about 325W. Let's assume 6% more power loss through all the wires, connectors, and switches reaching back to the Converter output. Your theoretical maximum power draw is now about 325W. The "480W" model has lots of extra headroom, and runs cool - where the little old one blew up.


New edit: "36V" Upgrade for 30A MPPT Controller, 5/15/2019 and 9/5/2019

But for me, things have changed. My new battery )LiFePO4) would actually LIKE 30A input, and Boost charging at 14.6 Volts. I've upgraded my controller into a new Tracer "BN" (just like yours, but with 150V input Voltage limit and 30A output current limit).

In my configuration, that MPPT output is now 438 Watts. At 93% efficiency, the input side is trying to consume 471W. Add the wiring losses which occur before reaching the MPPT input, and my "demand" from the Converter is probably a bit uipwards of upwards of 500W. I've just upgraded my Converter from the 24V-20A model, ordering the same device in version 36V-15A. That's good for 540W, and has a safety margin of about 10%. My new Voltage Booster is this one: https://www.ebay.com/itm/DC-12V-Step...-/311671280849. It is matched with a new 36V Detector Relay, I bought this one: https://www.ebay.com/itm/DC-36V-40A-...e/273843936462.

Because this is a 5-pin Relay, and the "power" leads can handle 40 amps, I can use only a single relay (instead of the old scheme with one "detector" Relay and a different "switcher" Relay). The "Common" power connector goes into the MPPT. The "NC" power connector (default, when the Relay coil has not been activated) connects the genuine Solar panel "+" lead. (That's the black wire which goes through the Circuit Breaker, before reaching the Relay.) After the Circuit Breaker, the incoming Bargeman cable is actually split - it goes into both the "Coil +" connector AND the "switched Power" connector.

Another 3-way splitter converts Solar "-" (another fat black wire) into 2 white wires: One for the Relay's "coil -" terminal, and the other into the MPPT Controller "Solar -" terminal. (The "Solar -" and "Battery -" leads are interconnected within the MPPT controller; negative grounding.)

With a 5-pin Relay available and usable, the Trailer wiring is super-simple. But whenever the TV provides only 12 volts, the Bargeman "Trailer Battery Charge" is totally disconnected, offering no power to the Trailer. It only works when the "Trailer Battery Charge" from the Tow Vehicle is running at 36V.

[klpauba]

I've upgraded my (blown) booster to 480W. It worked flawlessly on my recent TM trip.



To the left is the vehicle ground lug (the hex-shaped thingy used when jumping the battery). Next to it is a 30A self-resetting fuse, then the big relay (200A but it was readily available) and a 50A self-resetting fuse. The device with the four shrink-wrapped wires tucked down below the ground lug is the 480W 12V-to-24V boost device. I have the relay coil wired to a vehicle wire that is switched on when the vehicle is running. In this way the booster is always running when the vehicle is running -- I no longer use the switch in the cabin as it was something I would inevitably leave on when the car wasn't running.

My controller showed 268W flowing into the battery when I first hooked up for the trip (the state of charge of the battery was in the 90's but I don't remember the exact number). That's probably more than my 300W solar panels can supply on a nice sunny day!