How to Charge Truck Bed Camper Battery from Vehicle

Published 06/17/2019

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Redarc Smart Start Battery Isolator - 12 Volt - 100 Amp

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Bulldog Winch Rear Wiring Kit - Quick Connect to Terminal End - 3 Gauge - 16' Long

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Question:

Thank you for your thorough explanation. I just took the camper in yesterday to the dealer and they did electrical checks on the system and said everything was “up to spec.” They measured 13.4 V coming from the truck at the battery (although I thought I read somewhere that 14.4 was necessary to charge.) One of the things they brought up was that this new lance camper has a lot more gizmos drawing current even when everything is off such as 2 carbon monoxide monitors, smoke alarm, radio, tv, etc. So the bottom line is that you believe the truck’s alternator is capable of keeping the camper battery charged if it’s got sufficient current carrying capacity in the connecting wire. Correct? The reason I ask is I don’t want to spend all the money and take all the time and energy to do the wire upgrade only to find out that there’s just not enough output from the alternator to keep the camper battery charged.

asked by: Clarence

Expert Reply:

You are on the right track to answering your question of "why isn't the battery," being charged as the reason is that the charge circuit of your vehicle just can't carry enough amperage/voltage to keep the battery charged. The reason this is the case for your new setup is most likely because your new camper has a larger battery and/or has appliances that just draw more which uses more of the battery and the current circuit just can't keep up. So the wiring of the 12 volt charge circuit of your vehicle is going to be to thin and ran for too long of a distance to provide an adequate charge.

So the solution is to run a new charge circuit from your vehicle batter/alternator that can deliver enough amperage/voltage to keep the camper battery charged. To do this the new wiring will have to be MUCH heavier than what you currently have. So I recommend 3 gauge winch wiring witch quick disconnects. For that you'd want the part # BDW20025 for a 7-1/2 foot section that will wire to camper battery and then for the section that installs vehicle you'd want the 16 foot long section part # BDW20043. The quick disconnects allow you to easily disconnect the wiring if/when you remove the camper from your truck bed.

Now if you wanted a way to prevent the camper battery from accidentally draining the vehicle battery when it's not running you'd need to install an isolator. For that you'd need the part # 331-SBI12 and you'd be set.

expert reply by: Jameson C

Clarence

6/17/2019

Jameson C.

6/17/2019

Your alternator would have enough amperage to also charge the second battery as long as the circuit that connects the alternator to the battery has a heavy enough gauge wire like what I mentioned. If you look at the wire that connects the alternator to the vehicle battery you'll see that it's also very thick. Alternators rarely use their full capacity and most of the time the voltage regulator is pulling back the amount of amperage it charges since more power is produced that can be used.