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Old 02-23-2021, 01:07 AM   #1
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Gimme 12v

I want to charge a laptop while boondocking. Where are the 12v outlets? I'd like to plug in a small inverter or cigarette lighter charger. It's weird that there'd be USB outlets connected to the battery but not an outlet for charging a laptop, unless I'm missing something.

If I've got to put it in myself, do people usually wire it to the 12v side of the converter?
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Old 02-23-2021, 01:47 AM   #2
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I don't have your rig so this is only a guess.
The battery on towable trailers are for powering the brakes on the trailer. If you drain them while boondocking, you're not going to have brakes to tow it home. USB connections drain very little off the battery so you should have enough battery power on the way home.

You need a second battery, a generator or one of these to recharge your laptop https://smile.amazon.com/dp/B07S74MC...v_ov_lig_dp_it
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Old 02-23-2021, 10:39 AM   #3
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I had the same problem with 12VDC, my 2014 camper it did not even include USB charging connectors. I added a 12VDC socket to the water pump circuit. This maintains the laptop computer battery and allows charging phones, etc.
I seldom boondock, but have both generator and solar capabilities.
As far as the electric brakes on the trailer, (not on my camper). Unless I am totally misunderstanding the system. Trailer brakes sense braking from the tow vehicle, and apply brakes, using the 12VDC connection from the tow vehicles, all from the same 7 pin connector. Maybe a good backup system is to have a charged battery in the camper, but the 12vdc from the 7 pin connector is supposed to be maintaining the battery also.
My campers electrical system was a rats nest, I think there were 8 wires using one wire nut as the ground connection. I replaced that wire nut with a ground bus bar (from Home Depot). Some good practices on wire nuts is only 3 (maybe 4) wires to a wire nut.
Bob
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Old 02-23-2021, 10:49 AM   #4
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Quote:
Originally Posted by Bob414 View Post
I had the same problem with 12VDC, my 2014 camper it did not even include USB charging connectors. I added a 12VDC socket to the water pump circuit. This maintains the laptop computer battery and allows charging phones, etc.
I seldom boondock, but have both generator and solar capabilities.
As far as the electric brakes on the trailer, (not on my camper). Unless I am totally misunderstanding the system. Trailer brakes sense braking from the tow vehicle, and apply brakes, using the 12VDC connection from the tow vehicles, all from the same 7 pin connector. Maybe a good backup system is to have a charged battery in the camper, but the 12vdc from the 7 pin connector is supposed to be maintaining the battery also.
My campers electrical system was a rats nest, I think there were 8 wires using one wire nut as the ground connection. I replaced that wire nut with a ground bus bar (from Home Depot). Some good practices on wire nuts is only 3 (maybe 4) wires to a wire nut.
Bob
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Okay thanks. Did you just put two wires, one on each side of the pump, and hook those to the 12v socket? And how where did you mount the socket
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Old 02-23-2021, 11:41 AM   #5
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Two wires, if I remember right, one before the water pump switch (switch will not cutoff power to socket) and one to ground, but still fused on the converter (keep spare fuses). Check the connections before and after with a multimeter. I mounted the socket near the wall, under the table, outboard of the converter, just under the lip that the table sets on when stored. That is in the same area of the water tank and converter under that seat at the table.

Be careful. I do not warrantee or guarantee any results. DO AT YOUR OWN RISK!!!!

Bob
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Old 02-23-2021, 11:54 AM   #6
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Originally Posted by Bob414 View Post
Two wires, if I remember right, one before the water pump switch (switch will not cutoff power to socket) and one to ground, but still fused on the converter (keep spare fuses). Check the connections before and after with a multimeter. I mounted the socket near the wall, under the table, outboard of the converter, just under the lip that the table sets on when stored. That is in the same area of the water tank and converter under that seat at the table.

Be careful. I do not warrantee or guarantee any results. DO AT YOUR OWN RISK!!!!

Bob
Thanks. Forgot to ask, is your 12v socket just a cigarette lighter style port?
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Old 02-23-2021, 11:59 AM   #7
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Do you have a cigarette lighter charging cord and what are the voltage limits on the laptop?
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Old 02-23-2021, 12:00 PM   #8
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https://www.amazon.com/Power-Inverte...4099576&sr=8-6

https://www.amazon.com/Charger-HP-En...099734&sr=8-21
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Old 02-23-2021, 01:53 PM   #9
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Just a cig lighter socket. Small opening, and easy to acquire. I use a extension 12 VDC to a 12 VDC block that has 2 Cig sockets and 2 USB fast charging ports, sets on table which makes it easier to connect things.

I have an inverter for other 115 VAC loads, if necessary. I have a problem with the efficiency of inverter, they make heat which is wasted energy, unless you need the heat.

Bob
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Old 02-23-2021, 02:03 PM   #10
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Originally Posted by Bob414 View Post
Just a cig lighter socket. Small opening, and easy to acquire. I use a extension 12 VDC to a 12 VDC block that has 2 Cig sockets and 2 USB fast charging ports, sets on table which makes it easier to connect things.

I have an inverter for other 115 VAC loads, if necessary. I have a problem with the efficiency of inverter, they make heat which is wasted energy, unless you need the heat.

Bob
Sounds like a good set up. I already have the USB so I'll probably just go with the socket. I am also thinking about an inverter of the same size. Don't want to go bigger because of potential large current draws.
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Old 02-24-2021, 11:40 AM   #11
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Quote:
Originally Posted by Bob414 View Post
As far as the electric brakes on the trailer, (not on my camper). Unless I am totally misunderstanding the system. Trailer brakes sense braking from the tow vehicle, and apply brakes, using the 12VDC connection from the tow vehicles, all from the same 7 pin connector. Maybe a good backup system is to have a charged battery in the camper, but the 12vdc from the 7 pin connector is supposed to be maintaining the battery also.
You are correct about the normal operation of the brakes. However, the emergency break away system assumes the electrical connection between tow vehicle and trailer will be broken. The break away cable pulls the pin out of an electrical switch which then connects the trailer brakes directly to the trailer battery for full brake application. No trailer battery, no brake application after the break away pin is pulled. Trailer is free to roll where it wants.

Depending on the programming of the tow vehicle alternator, it may/may not charge your trailer battery through the 7 pin. Insufficient tow vehicle wiring will also limit how much current gets to the trailer due to voltage drop. On my minivan, I can get about 10 amps before voltage at the trailer drops below 12.9V (no charge to trailer battery). In my 1st A-frame, I had to run fridge on 12V because propane flame would blow out, and there was no automatic relight. That consumed all 10 amps. With the HW A-frame, the fridge relights on propane if the flame blows out so the 10 amps is available to charge the battery at a slow rate (13.6V is the best I see while towing).

just my experiences
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2008 Hyundai Entourage minivan
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Old 02-25-2021, 09:57 PM   #12
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Quote:
Originally Posted by Bob414 View Post
Just a cig lighter socket. Small opening, and easy to acquire. I use a extension 12 VDC to a 12 VDC block that has 2 Cig sockets and 2 USB fast charging ports, sets on table which makes it easier to connect things.

I have an inverter for other 115 VAC loads, if necessary. I have a problem with the efficiency of inverter, they make heat which is wasted energy, unless you need the heat.

Bob
Is the inverter you use a pure sine wave inverter? Got a link? Thanks
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Old 02-25-2021, 10:13 PM   #13
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Quote:
Originally Posted by Bob414 View Post
Just a cig lighter socket. Small opening, and easy to acquire. I use a extension 12 VDC to a 12 VDC block that has 2 Cig sockets and 2 USB fast charging ports, sets on table which makes it easier to connect things.

I have an inverter for other 115 VAC loads, if necessary. I have a problem with the efficiency of inverter, they make heat which is wasted energy, unless you need the heat.

Bob
A plain 12V aux socket such as you installed is better than a dedicated USB charger outlet. USB technology changes. It's easy to upgrade by buying a newer plug-in charger. Also, USB chargers can be a parasite load. Just unplug it to kill it.

Minimize the length of your DC extension to minimize voltage drop.
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Old 02-26-2021, 01:23 AM   #14
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A plain 12V aux socket such as you installed is better than a dedicated USB charger outlet. USB technology changes. It's easy to upgrade by buying a newer plug-in charger. Also, USB chargers can be a parasite load. Just unplug it to kill it.

Minimize the length of your DC extension to minimize voltage drop.
USB a parasitic load going from 12v to 5v? What's the amperage draw?

I'm considering installing a panel with 2 usb ports, a 12v socket, a battery monitor, and an on/off switch. Will the on/off switch prevent drain?

I actually don't need the usb ports as I've already got a couple, but I like the battery monitor that comes with this. Would it be better to just put in a 12v socket and then battery monitor somewhere else?
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Old 02-26-2021, 08:58 AM   #15
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Originally Posted by nanewnanew View Post
USB a parasitic load going from 12v to 5v? What's the amperage draw?

I'm considering installing a panel with 2 usb ports, a 12v socket, a battery monitor, and an on/off switch. Will the on/off switch prevent drain?

I actually don't need the usb ports as I've already got a couple, but I like the battery monitor that comes with this. Would it be better to just put in a 12v socket and then battery monitor somewhere else?
I couldn't say how much that parasitic load is. Maybe immaterial by itself but multiple parasitic loads add up. The importance depends on your battery capacity and expected needs.

If you're adding the on/off switch inline yourself and it's on the only source of 12V, yes, it will prevent the drain. But, if it's incorporated into the panel you buy, I cannot say. Probably, but dunno.

As for the "battery monitor", it's probably just a volt meter. That can give an indication of voltage level but is an inaccurate and misleading indicator of state of charge. You can get an accurate voltage only with no load on the battery for about an hour, at which point the voltage will have settled.

I used to have one of those but learned they're not worth much. A better approach is an actual battery monitor that continuously measures current into and out of the battery. They vary in cost from $45 to >$200. Each price range has its proponents and detractors. I have the cheapest version and am satisficed with the accuracy and functions.

$45: QWORK Battery Monitor Voltmeter Ammeter


$130: Victron SmartShunt (No display. Connects to phone app by Bluetooth)

$206: Victron Energy BMV-712 Smart Battery Monitor (Has display and possibly additional features.)
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Old 02-26-2021, 10:36 AM   #16
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If you're adding the on/off switch inline yourself and it's on the only source of 12V, yes, it will prevent the drain. But, if it's incorporated into the panel you buy, I cannot say. Probably, but dunno.

As for the "battery monitor", it's probably just a volt meter. That can give an indication of voltage level but is an inaccurate and misleading indicator of state of charge. You can get an accurate voltage only with no load on the battery for about an hour, at which point the voltage will have settled.
Chris, the installation of a 12V/USB port is in a pop-up camper. The only hidden loads are the CO/propane alarm, the stereo (if no kill switch installed), and the fridge control board (only on HW pop-ups, and only when fridge is turned on).

I find with the similar electrical system of an A-frame, that the minimal 12V loads do not affect the voltmeter estimates of battery SOC. I installed a $7 voltmeter for that purpose on my A-frame - and it works remarkably well. After set up for dry camping, the voltage is 12.6V for fully charged batteries. Each 0.1V decrease is equal to about 10% SOC, so 12.1V is 50% SOC - and time to recharge. Normal usage is about 10% SOC/day, sometimes a little less.

To enhance my dry camping, I did install a kill switch on the stereo and on the fridge fans (140ma total draw). The OP should have little difficulty establishing whether or not the embedded switch shuts off the USB outlets. Even if the switch doesn't, the idle draw of a couple of 5W USB ports should be well under 100ma, and probably under 30ma.

Fred W
2019 Flagstaff T21TBHW A-frame with Costco/Interstate 210AH GC-2s for 4+ nights dry camping without recharge
2008 Hyundai Entourage minivan
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Old 02-26-2021, 12:18 PM   #17
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I stand corrected. I still recommend installing 12V sockets instead of USB chargers. They're easier to upgrade by just buying a new plug-in charger as technology changes.
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Old 02-26-2021, 01:22 PM   #18
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Thanks all for your input, much appreciated.

As far as getting a pure sine wave inverter, I'm looking for something in the 125-150W range. Anybody have any suggestions?
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