Forum Discussion

ajriding's avatar
ajriding
Explorer II
Jul 21, 2020

SC power supply charging?

I have a little cargo-camper project I am working on...

I just pulled a DC power supply out of a 2004 Coachman class-c. I am not sure how it was wired exactly. There was a solenoid next to it so I assume when plugged to shore the camper would get DC from the power supply (13.4 volts at 55 amps max) and not the battery, but I assume the power supply would charge the coach batts too bc I have not found a proper batt charger in the camper. So, the solenoid would be an A-B switch, not on-off if I am correct.

I do not plan to spend money on a cargo trailer, but to just use what I have or not have, so no need to tell me about the expensive options..
If I want to wire this power supply into my batts, then how is it best done? Keep in mind I am above avg for electrical knowledge, so lets keep the musings to a minimum.

I do not want to just put raw 15 amps on the batteries while plugged in, but I do want to use the DC power and not the batteries while plugged in, and I would like a way to charge the batts too. I have solar, so very rare to need external charge, but when I do need it I want it there.

I could do a cheap charge controller, like a solar controller, which I have on the solar already.

How is the solenoid normally wired? Is there 120v shore power wired into the switch terminal of the solenoid? There are small wires going into it, at least 3 maybe more, going to it, not sure where they come from. So when shore is plugged in the solenoid would switch to Power Supply power.
I know how I wire the all DC auto parts store solenoids, but this one is much different...

Also, I have a class-c that I am parting out. Triton v-10 and trans have around 20,000 miles and I am selling all the interior components, keeping only a few for my little project.
  • wa8yxm's avatar
    wa8yxm
    Explorer III
    Jul 21, 2020
    What was the make of the unit you pulled.. I know some had a relay or solenoid ON THE UNIT not beside it. So I'm not sure what you got.
  • time2roll's avatar
    time2roll
    Nomad
    Jul 21, 2020
    If the thing puts out 13.4 volts you can just connect to the battery and run continuously. This is a float charge at best and will never hurt or overcharge the battery. Going to be a very slow charge to get you through lack of solar. No need for additional switching or regulation.
  • DrewE's avatar
    DrewE
    Explorer II
    Jul 22, 2020
    Usually a converter is wired directly to the battery (via fuses / circuit breakers as needed to protect against short circuits). Converters are designed to not overcharge the battery even if connected and powered for a long time. The converter is also probably capable of putting out a lot more than 15A DC: typically it would be rated around 40A to 60A or so. That rating is a maximum current; it's basically a voltage regulated supply and so will only supply as much current as is needed to maintain whatever output voltage it's set to. If it's a multistage converter--which I would not really expect--the output voltage setting will vary depending on what mode it's in, higher for the initial charging of a depleted or partly discharged battery and the lower to maintain a full charge.

    The solenoid is likely not directly related to the converter. It may be a battery disconnect solenoid, which is a single pole latching solenoid: apply 12V momentarily in one polarity to the control terminals to turn it on, and in the reverse polarity momentarily to turn it off. The control wires would generally go to a center-off DPDT momentary switch. It may also be a battery combiner relay that connected the house and chassis 12V systems of the motorhome together when the engine was running (to allow the alternator to charge the house batteries while driving), in which case it would be a continuous-duty single pole non-latching solenoid.
  • RJsfishin's avatar
    RJsfishin
    Explorer
    Jul 22, 2020
    Like was said, connect the power supply/charger directly to the battery. When unplugged the camper will be running off the battery, when plugged in the camper will be running off the power supply. No need to separate the power supply from the battery
  • ajriding's avatar
    ajriding
    Explorer II
    Jul 23, 2020
    Title should read DC, not SC, but I cant change that...

    Well, if I can leave it connected as a float charge all the time then I will not worry about it. So I will do that.
    I do want ability to recharge the battery, but with solar on the roof this is not a big thing.
    The only reason I plug in is to run the fridge and AC, but if I have power I will save the batts the added cycles now and use the converter for lights, charging phone and fans.
    It has a household plug, so I may just use that as an on/off method.

    I will have to get the name off of it. It is big, but not heavy. Does not seem to be a charger, just power.

    after looking again. looks like it will do 1/2 amp to 55 amps as needed. Charger and power source.
    I wired it all up today and used the heavy wires it came with and very close to batt.

    thanks
  • landyacht318's avatar
    landyacht318
    Explorer
    Jul 26, 2020
    I use an adjustable voltage power supply exclusively for plug in charging duties. Mine has a shunted ammeter/voltmeter amp hour and watt hour counter on the DC output, and some additional computer fans added to the casing.

    These fans and ammeter, would still run when there is No AC available, unless I disconnected the Anderson powerpoles.

    Now, I use a 50 amp 'Ideal Diode' so when I unplug from AC, I do not have to unplug the DC connector from the power supply. The ammeter and fans shut off instantly when I unplug from AC.

    The Ideal diode only loses 0.04 volts across it at 40 amps, as opposed to the 0.4v+ of a silicone diode, but even if there was a non negligible loss, I could just turn the voltage dial a little higher to compensate. I also parallel other power supplies/ chargers when 40 amps does not float my boat, and the Ideal Diode perhaps keeps the power supply happier.

    It's my opinion a adjustable voltage power supply yield vastly superior charging to automated 3/4 or 12 stage chargers( the 12th stage is fellating the proud smart charger/ battery owner), and they do not get confused when there is loads on the battery while charging.

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