question

robtig1 avatar image
robtig1 asked

Need to limit the charging draw into a bank of lead acid batteries

The application is - I have a 5th wheel trailer, and I have added 380 Ah of lead acid batteries (weight isn't really a concern). 400 amps of solar, and a Smartsolar MPPT 150/35


What is a concern is, I will attach my 7 pin trailer wiring, and it will begin to charge the trailer batteries off of the 10 gauge wire that goes through the wiring harness, and I assume, governed by a 25 amp or so fuse. I suspect this load will blow a fuse if my batteries are low, since that wiring isn't intended to manage the level of load I would put on it.


I don't need fast charging - we drive for hours. The truck alternator is a 120 Amp, and I also don't want to put a heavy load on it.


So… is there a device that will limit the draw so I can essentially cause my batteries to charge slower, say at a max of 20 amps, or even 10, and not worry about overloading my vehicle.

battery charging
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1 Answer
kevgermany avatar image
kevgermany answered ·

Use an Orion DC:DC charger. The first two numbers in the model number are input and output voltages, the third number is the max charge current.

Mount it as close to the house battery as possible.

Input current is normally very slightly higher than output current if input/output voltages are the same. Base you cable calcs on this with a reasonable margin. Also check for voltage drop on the input side. If there is a significant drop due to long cable run, this will increase the input current proportionately and cause heating.

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