Regard dc to dc charger Etrailer

[skiman]

I see Etrailer is carrying a dc to dc charger for maintaining trailer battery charge. Fixes the lack of charging with today's funky allternators and poor wiring. Good tutorials as well.

https://www.etrailer.com/dept-pg-Bat...V-BCDC-ManufSP

Redarc Charger not Regard - darned auto spell correct

[Brian B-P]

I had looked at Redarc products for two applications:

1. trailer battery charging
2. charging a 24 volt device from a 12 volt vehicle.

In both cases it appears that they have a great product, but like every other brand in this specialty market it is very expensive, and I wasn't willing to pay that in either case.

These units that eTrailer is carrying are really nice, handling both solar panels and the tow vehicle. Since it would replace an ordinary solar charge controller, this looks like a great option for an aftermarket solar installation with added charging-from-tow-vehicle functionality.

[sclifrickson]

I don’t understand how these things work or solve the vehicle charging problem. Can someone break it down for me, or point me to an existing explanation suitable for sometimes-dummies?

[rubicon327]

Originally Posted by sclifrickson

I don’t understand how these things work or solve the vehicle charging problem. Can someone break it down for me, or point me to an existing explanation suitable for sometimes-dummies?

As I understand it the Redarc is wired directly to the tow vehicle battery with heavy gauge wire and can send adequate charging amps to the trailer battery regardless of what the tow vehicle alternator may be doing. This may have significant value to those that prefer to run a refrigerator on 12V on the road but have issues depleting the batteries. Santiago added one of these on his system that ran a Nova Kool compressor based fridge.

From the manufacturer/etrailer page:
"This charger connects directly to your battery, rather than pulling power from your vehicle via the trailer connector. This is to ensure that it's able to fully charge your auxiliary battery. A standard 7-way trailer connector is limited to 10 or 15 amps of current, which will not be able to fully restore a battery for use. But this charger can transfer up to 40 amps of current to both charge and maintain your auxiliary battery.

The BCDC1240D is a three-stage, 12V DC-DC battery charger that operates from an alternator input of 12V or 24V and a 12V nominal solar panel input. The input voltage of the BCDC1240D can be above, below or equal to the output voltage making it ideal for charging an auxiliary 12V battery where the distance from the main battery may cause a significant voltage drop. The BCDC1240D is also designed to isolate the main battery from the auxiliary battery, to avoid over-discharging the main battery. The Dual Input In-vehicle Battery Chargers also feature a Maximum Power Point Tracking (MPPT) solar regulator. The unit will always take as much power from the solar input as it can before supplementing that power, up to the maximum rated output, from vehicle power input."

The etrailer page linked also has a very good explanation at the bottom of the page.

[sclifrickson]

So this would require a separate and dedicated, disconnectable wire between tug and trailer, yes? And which side would one mount it on? Trailer side to reduce voltage drop from the charger? And why on this green earth are these doodads so expensive?

[rubicon327]

Originally Posted by sclifrickson

So this would require a separate and dedicated, disconnectable wire between tug and trailer, yes? And which side would one mount it on? Trailer side to reduce voltage drop from the charger? And why on this green earth are these doodads so expensive?

Yes, this is what Santiago did: "I connected fused (60amp) 4 AWG welding wire housed in plastic ribbed loom to rear of truck. There it went into an Andersen-120 2 pin water tight connector with tight water resistant rubber cover on truck and trailer side. This sends 40 amps to the trailer's DC to DC 3 stage charger."

As per Redarc: "It is important to ensure the charger is mounted as close as possible to the battery being charged (auxiliary battery)."

Considering the quality of construction and all the features I don't really see it as all that expensive. One has to ask themselves how this really helps them though. If your fridge doesn't work real well on 12V anyway then what are you trying to accomplish? Remember Santiago had a 12V compressor fridge. Nothing else should really be draining your batteries when going down the road and the vehicle charge line should at least maintain the charge. Many owners also already have solar charging the batteries while going down the road (Santiago did not, but had future plans to possibly add, but ended up selling the trailer). Personally I would possibly only add something like this if I was going to commit to a very robust aftermarket solar installation as Brian suggest above, but if you have enough solar input to an adequate charge controller the tow vehicle charging issue becomes kind of moot (except for maybe very cloudy/rainy days and traveling at night).

I'm sure there are more experienced electrical guys on the forum that can chime in about the merits of adding something like this or not. Sanitago had very specific purposes for adding this and he apparently didn't nail it perfectly on the initial install saying later: "Looking back, I should have used a 100 or 130 amp DC to DC charger for quicker charges from the engine." He had a big battery bank, but even so I don't know who makes a DC-to-DC charger with that much output. Redarc doesn't.

[Brian B-P]

Although a separate connection could be used, there is no need to use anything other than the standard 7-pin towing connection... at least with the 25-amp model. The point of the DC-to-DC charger is (as identified above) that it can boost voltage as required, so it overcomes the problem of voltage lost to resistance in the tow vehicle wiring. The eTrailer page says that the 7-pin connection can only handle "10 or 15 amps", which is not true if it is wired properly (but would be true if it has undersized wiring). I believe that a 40-amp (or even larger) unit would be appropriate only with a separate higher-capacity connection.

This is the manufacturer's U.S. web page for the 25-amp unit linked above:
DUAL INPUT 25A IN-VEHICLE DC BATTERY CHARGER
Neither the brochure nor the manual say anything about a dedicated connection which is separate from the normal towing connection.

When looking at wiring for this unit, keep in mind that the target audience (which is mostly in Australia) is not people with travel trailers - it is people running an auxiliary battery in the 4WD vehicle that they use for camping, mostly to run refrigeration units. It's suitable for a travel trailer (or as the manual says, "caravan"), but that's not what the documentation describes.