Testing a Renogy 20A DC-DC charger with my 100AH Lithium camper battery.

[Anthony Hitchings]

My 2011 Jeep Liberty has a factory tow package with relatively small conductors from front to rear of the TV and only a 20A fuse in the +12V line to the 7-pin connector.

So the question was - what would happen if I try to use my 20A (rated output) Renogy DC-DC charger (which was bought 3 years ago, for a different reason)? Would it work at all, or would it blow the 20A fuse in theTV, or what?

The answer is:

1) Engine running at IDLE, 9.66V at the charger input, 13.6A going into the Li battery (battery was at 55% State of Charge).
2) Engine NOT running, start chargingat 8.81 amps into Li battery and 9.11 volts at charger input, but both declining steadily (not a realistic test).
3) repeated test (1) and got the same result.

DC-DC charger and the Li battery were outside the TV at the rear of it. This was a "lash-up" test using my 7-pin test harness.

So I do NOT NEED big wiring in my TV in order to get some useful charging when towing the camper - anything over 12A into the battery is OK for me because its likely a longish tow and the towing-charge is to supplement solar or what was left in the battery in the first place.

At age 72 I have no desire to run more wires in any car - so no wiring upgrade will happen. This arrangement works with all the standard wiring and fuses and relays etc in the Jeep - which is just fne.

Now I can focus on installing the DC-DC charger into the Aliner - it will be up front (inside) very close to the battery; along with the charge enable-disable switch.

Its fortunate that my DC-DC charger is the 20A model, I think that helped get a good result on a limited 12V suppply circuit circuit from the Jeep.

 

[Anthony Hitchings]

Installed:

The DC-DC unit is on the inside of the camper's front wall. It is mounted reversed left-right so that I can see the itsy bitsy status LED thru the cargo door (to the left). The trigger switch that makes the DC-DC unit turn on is located inside the cargo door. The switch toggle has a red LED in its tip, and the toggle cover will turn the trigger off if the cover is closed.

Except for one new packet of ring terminals, I used wiring and stuff that I had "lying around".

Still to be done is an anti-bump shield in front of the DC-DC unit and its nearby 12V fuse panel. The bumping would be from the levelling pads and wheel chicks that get stored in this cargo compartment.

FYI - the +12V from the Jeep Liberty TV goes only to this DC-DC unit - nowhere else.

 

[tombiasi]

Installed:

The DC-DC unit is on the inside of the camper's front wall. It is mounted reversed left-right so that I can see the itsy bitsy status LED thru the cargo door (to the left). The trigger switch that makes the DC-DC unit turn on is located inside the cargo door. The switch toggle has a red LED in its tip, and the toggle cover will turn the trigger off if the cover is closed.

Except for one new packet of ring terminals, I used wiring and stuff that I had "lying around".

Still to be done is an anti-bump shield in front of the DC-DC unit and its nearby 12V fuse panel. The bumping would be from the levelling pads and wheel chicks that get stored in this cargo compartment.

FYI - the +12V from the Jeep Liberty TV goes only to this DC-DC unit - nowhere else.

You are using 12 volts to make 12 volts?

 

[LilRed]

You are using 12 volts to make 12 volts?

These devices will step up the input 12v through voltage sags or cable loss to a “+12vdc” that actually matches the charge profile voltage (like 14v) of the battery, so yes.

Typical 3 stage charger:

• Bulk Charge: the first stage of charging in which a high voltage, high amperage charge is supplied to the battery(ies). This stage typically returns 70-80% of the depleted battery capacity. It ends when the battery voltage reaches approximately 14.6V
• Acceptance/Absorption Charge:once the bulk stage ends, that voltage (14.6V) is maintained while the charger slowly reduces the amperage being supplied. This stage returns the remaining 20-30% of depleted battery capacity and ends when the charging current has reduced to approximately 1% of the battery’s capacity (for instance, a 100 amp-hour battery would be fully charged when the absorption charge current is reduced to 1 amp)
• Float Charge: once the charging amperage drops to a defined target rate (typically down to 1% of the battery bank’s capacity), charging voltage is reduced (13.6V) to maintain the battery’s charge at 100% of its capacity.

 

[Anthony Hitchings]

You are using 12 volts to make 12 volts?

YES - we are taking a weakened 12V source - because of the long and small wires in the TV OEM harness, to step it up to charging voltage of the Li battery.

I have done this before, using a portable pair of small 12V batteries that I charged during the day from a rooftop PV on the car, and then later back at our Yellowstone campground I used the DC-DC unit to move the stored energy from the portable batteries to the camper's battery.

 

[Anthony Hitchings]

So to wrap it all up, I now have the following ways to charge my Lithium house battery in the camper:

1. Renogy solar system - any time that I have sunshine, at camp or while towing.
2. From the Jeep Liberty via the towing electrical harness and the DC-DC "charger", set to its "Lithium" option (and Type 2 battery).
3. On Shore Power, using the built-in Progressive Dynamics PD4135 "Converter" (not the Lithium model, but good enough in the real world).
4. On Shore Power, using my portable AC-DC Lithium battery charger.

 

[tombiasi]

So to wrap it all up, I now have the following ways to charge my Lithium house battery in the camper:

1. Renogy solar system - any time that I have sunshine, at camp or while towing.
2. From the Jeep Liberty via the towing electrical harness and the DC-DC "charger", set to its "Lithium" option (and Type 2 battery).
3. On Shore Power, using the built-in Progressive Dynamics PD4135 "Converter" (not the Lithium model, but good enough in the real world).
4. On Shore Power, using my portable AC-DC Lithium battery charger.

Just wanted to be sure I understood what you were doing.