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Thread: Critique my electrical diagram please

  1. #11
    Didn't know that about photobucket. Haven't been too active on forums in a while. Sucks that they went that way. How that that hasn't distracted from the intention of this thread at all.

    Should be attached below. Added a fuse on the DC out to the fuse box as suggested but it's not shown on this version of it yet.

    I've got experience with this on motorbikes (the missing dude thing was an oversight) but on this the equipment is a lot more expensive so looking to just manage with an inverter/charger. I read Dave Orton's and other inspired blogs. Just wonder if that complexity can't be mitigated with a design like this.
    The diodes could be replaced with switches too but like I said that would add a margin of error. I also like relays but would need a switched power arrangement which I can't think off.

    I take the point on Xantrex and will look into it a bit more.

    Sent from my SM-N920W8 using Tapatalk
    Last edited by tmotten; 12-03-2017 at 06:17 AM.

  2. #12
    Join Date
    Mar 2010
    Jämte i exil
    If I am correct the ”M” indicates the truck alternator??
    You might omit the diodes (diodes are seldom a good idea in battery charging circuits) and the ”shore-gen” transferswitch.
    Connect ”DC charge” direct to battery. Unless the inverter also serves as a B2B charging controller, Connect alternator direct to battery, but thru your favourite type isolation relay.
    But, rather than connect from alternator, usual practice is connect at truck battery. Usually works out shorter distance & does not require another fat conductor on alternator terminal.
    Last edited by Verkstad; 12-03-2017 at 06:42 AM.

  3. #13
    Join Date
    Nov 2010
    Middle of Nowhere, Outer Skin of Space Ship Earth, 1 A.U. from Sol, Outskirts of Milky Way.
    The error in the diagram is the separate "DC in" and "DC charge" connections to the inverter/charger.

    There is only one DC connection on an inverter/charger.*

    There are two AC connections, "AC in" and "AC out", but DC has only one connection - "battery".

    As I said, the DC connection can be either...

    In (drawing power from battery and suppling power to AC out (operating as inverter))


    Out (drawing power from AC in and supplying pass through power to AC out and to battery (operating as charger))

    ...but not both at the same time.

    So as Verstad just more or less said - the diodes and manual transfer switch won't work.

    Hence Orton's dual inline inverter setup - one "inverter only" (fed by engine battery) to supply AC to a second "inverter/charger" so the inverter/charger can operate in battery charger mode to charge a house battery.

    But that dual inline inverter setup is a bit goofy if you ask me. The rationale behind that setup is based on a couple things, one of which is outright false.

    The first reason behind Orton's dual inline inverter setup - which he mentions on his page - is that you aren't supposed to mix different lead-acid batteries when charging. This is false. Lead-acid batteries have to be identical (type, size, brand, age, etc.) if tied into a full-time battery bank. If only tied part-time during charging, they don't.

    The second main reason for that setup is so that the charger section of the second inverter can do a better job of charging the house battery than simply charging the house battery from the alternator via ACR or split-charge relay. Well, that's a good reason. However, I don't think it's a good enough reason to justify the added complexity. The "alternator->engine battery->relay or ACR->house battery" setup is simple, reliable, proven and automatic, and will get the house battery charged. Eventually. If you drive enough hours.

    And there's the rub. One of the reasons for Orton's setup - again stated on his page - is to limit the load on the alternator. So you can charge from the alternator and it will take a long time. Or you can feed a good charger from an inverter fed by the alternator to get a more precise charge to the battery, which should take less time. But if you limit it too much, it won't save enough time to make the whole complex rig worth the bother.

    Ultimately, Orton has other reasons (supplying various AC loads), which might justify the complexity of the dual inline inverters, but I wouldn't go about it the same way...

    If the second inverter (from the house battery) is big enough to supply the AC loads from the house battery, then I would just rig it to do that all the time.

    Then the only issue to be solved is charging the house battery. The most common way to do that is either, A) a split-charge relay, B) Automatic Connection Relay (ACR; split-charge relay with a brain) or, C) B2B (battery to battery) charger.

    The B2B will do the most precise job, and cost the most. If it's big enough, it will even do it faster. But lead-acid batteries are not precise electronic devices. They are sloppy chemistry experiments in a plastic box. Great precision in charging normally isn't required.

    *[There are of course exceptions to every rule. Some inverter/chargers do have additional DC connections. Commonly they might be for something like "solar in" or "battery bank #2". But none have the ability to both suck battery power and push battery power simultaneously.]

  4. #14
    Thanks for the review. Looks like I overestimated the inverter/ charger's capabilities. That sucks. Could have sworn it had a secondary DC output but guess not. Maybe a bad time of year to design this. :-(
    I understand what you're saying. I do like the idea of providing a decent charging profile to the house battery. I may have to rethink my AC needs though.
    I see CTEK offers a DC system which looks interesting also.

    Sent from my SM-N920W8 using Tapatalk

  5. #15
    Let's try take 2. I've decided to get rid of AC needs and keep it simple. I do like the idea of those Sterling chargers though so I've added that.
    Not sure if I'm providing too many fuses. Might be able to get rid of the one between the switch and the battery.

    Sent from my SM-N920W8 using Tapatalk

  6. #16
    Good call. Copied without editing. That unit is only rated to 10A I believe.

    Sent from my SM-N920W8 using Tapatalk

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