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Thread: Battery Isolator choice!

  1. #1
    Who am I? HiJackZX1's Avatar
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    Battery Isolator choice!

    I finally bought the 0 gauge wire to link the front to the back (I needed 13 feet of it). I also bought another T block for under my seat. Here is how I thought about hooking it up. Does this look like it will work?



    The 2 T blocks are located under the driver seat. I would love to put the isolator under there also, but I know it will not fit. Is it possible to mount the isolator under the car? My SUV is very deep underneath, so I was wondering it would be ok to mount it under, maybe sealed inside a water tight case. What do you guys think? I am trying to keep from having to have double long runs of wire. With the setup I have pictured it would be one single run of wire, except for the wire going from both T Blocks to the fuse panels. Both of those are 4 gauge runs, which I have plenty of wire for.

    What do you guys think. Do I even have the isolator setup correctly in my mind?
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  2. #2
    Raw Wave
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    0G for camera & PC? Wow - hungry devices....

    What isolator - a relay off the charge lamp? Probably next to the main battery (AFTER the fuse which you haven't shown - not that you've shown the fuse at the PC battery end...) is best.

  3. #3
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    Quote Originally Posted by OldSpark View Post
    0G for camera & PC? Wow - hungry devices....
    that is what i thought at first, but his setup needs to be taken into account-- off the top of my head, there are 2-320w dc-dc's, 6-7 headphone amps(used to run off AA's--i assume around 100-200ma), and 6-7 screens(about 2A ea)...(though i know i'm missing at least a couple of things) so he is around 1,000w give or take with just the stuff i can think of..

    so, going off my handy-'lil chart:


    he could really get away with 4 ga, but with the way hijack adds stuff, 0ga is a nice overkill..

  4. #4
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    So 17A plus a max of ~750W if you run the dc-dc to the max, 750W => ~60A (<55A if charging)... hence <80A.

    So (say) a 100A relay with (say) 100A fuses at each battery end... Probably driven from the alternator light circuit.

  5. #5
    Who am I? HiJackZX1's Avatar
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    Not everything is run off of 0 gauge. Its simply the main line running from the front to the back. Everything that connects to to the 0 gauge line is 4 gauge. So the camera fuse panel, which will some day get 4 FLIR cameras and a second DQP, then the rear has the car pc, 8 screens, 4 amplifiers, two car PC systems, and the PSUs and 12V to 5V regulators.

    i will also say that I am upgrading the Alternator to a 260 amp version. Don't I have to buy the isolator around that?

    Ok, I was looking at the instructions for a PAC-200, thats what I will buy. I am going with the 500 amp version. They don't seem to have any thing in between 200amp and 500amp.



    So with the PAC-500, I can do what I want. I just need to make an enclosure to protect it.

    Now the only thing is, in the picture it has two lines running from the Alternator. Is that normal?
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  6. #6
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    What a coincidence - another diagram that I picked on (see here).

    That drawing incorrect (for most installations).
    Connect battery to battery with a fuse at each end (as that PAC-mob do in another one of their OTHER docs for the PAC-200 isolator).


    The isolator has nothing to do with alternators - it is fitted to keep independence between multiple batteries. (That is not only for cranking reserve etc, but also so when one battery collapses, it does not wreck the other battery - that for people that don't think it is acceptable to keep batteries paralleled.....)

    The cable and fusing size is based on the maximum load (except short-term peaks) PLUS the battery recharge current.
    I use self-resetting circuit breakers instead of fuses to handle high battery charging peak currents (eg, I have a 50A breaker; the (small 38AH) AGM battery will take 40A if it cranks the car (a 140A reduction starter for 5-10 seconds) which drops to well under 10A within one minute.


    You should consider a "normal" 30A relay off the alternator light that then drives the PAC relays. (Or to drive other "standard" ad separate relays for the loads assuming split load supply & fusing - ie, remote is using 0G etc.

    500A seem way overkill for what you want.
    Like I said - 100A should do....
    That gives ~20A minimum spare for recharging the 2nd battery.


    PS - in the 12volt link above, you may note my comment wrt the BC-12 (SPR-xxx kits) "But it uses a microprocessor - I suspect one of those quad-analog LM series.... . Yes - that refers to the LM set of integrated circuits - the "analog" chips that are probably used as "microprocessors"(sickly sic!).
    I love making fun of "smart isolators", "priority recharging" and all the other bullsh that sucks in the masses....

  7. #7
    Who am I? HiJackZX1's Avatar
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    Quote Originally Posted by OldSpark View Post
    What a coincidence - another diagram that I picked on (see here).

    That drawing incorrect (for most installations).
    Connect battery to battery with a fuse at each end (as that PAC-mob do in another one of their OTHER docs for the PAC-200 isolator).


    The isolator has nothing to do with alternators - it is fitted to keep independence between multiple batteries. (That is not only for cranking reserve etc, but also so when one battery collapses, it does not wreck the other battery - that for people that don't think it is acceptable to keep batteries paralleled.....)

    The cable and fusing size is based on the maximum load (except short-term peaks) PLUS the battery recharge current.
    I use self-resetting circuit breakers instead of fuses to handle high battery charging peak currents (eg, I have a 50A breaker; the (small 38AH) AGM battery will take 40A if it cranks the car (a 140A reduction starter for 5-10 seconds) which drops to well under 10A within one minute.


    You should consider a "normal" 30A relay off the alternator light that then drives the PAC relays. (Or to drive other "standard" ad separate relays for the loads assuming split load supply & fusing - ie, remote is using 0G etc.

    500A seem way overkill for what you want.
    Like I said - 100A should do....
    That gives ~20A minimum spare for recharging the 2nd battery.


    PS - in the 12volt link above, you may note my comment wrt the BC-12 (SPR-xxx kits) "But it uses a microprocessor - I suspect one of those quad-analog LM series.... . Yes - that refers to the LM set of integrated circuits - the "analog" chips that are probably used as "microprocessors"(sickly sic!).
    I love making fun of "smart isolators", "priority recharging" and all the other bullsh that sucks in the masses....
    HAHAHAHA, thanx for that link, that is too funny. So the 500amp is over kill, so to feel safe I am going with the 200, which is still over kill, but still enough to put me to ease.

    You lost me with the 30A relay. Doesnt the ignition control the PAC?
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  8. #8
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    If you want to use the "Ultimate Intelligence Battery Isolator" (Patent Pending C22), then the charge lamp controls the relay (PAC).
    That is the best system for normal battery isolation where typical alternators (with charge lamps) are used - there are no voltage threshold issues nor switching delay issues....
    (Systems without typical rotor regulation require voltage or other sensing - eg, bike & marine systems with permanent-magnet & "stator" type alternators.)

    Most alternators charge lamp circuits will energise a typical relay, but it depends. The older (external) mechanical voltage regulators will supply several amps, but electronic regulators may be limited... Most single-wire D+ or multi-wire alternators with the L (charge-lamp) terminal will supply 0.5A to 1A.
    (I say circuit because the D+ or L is both an input and an output.)

    Only very modern alternators with EMS interaction may have problems, but there is usually a charge lamp that can still be tapped. (It's really a NOT-charging lamp.)

    And if powering a relay is a problem, then a cheap MOSFET capable of passing 100A can be used (eg, a $3 MOSFET that takes a few micro-Amps to pass 50A - 150A etc.)

    But for those that like it simple and mechanical, stuck to relays.

    The PAC relays may take over 1A to energise and that might strain the alternator (ie, it's voltage regulator).
    Hence use a smaller relay connected to the charge lamp, and that relay can switch other relays.... eg, a 30A relay can switch (say) 10-30 PACs to isolate 10-30 batteries, or switch one PAC that switches 200-500 other PACs etc.
    (That's just the same as using a more expensive "smart" isolator to power another relay(s) because the smarty doesn't have enough capacity - ie, to boost an 80A smart isolator to 400A, have the smarty power a 500A PAC instead of the load. Suppliers however prefer to sell you the same sensing circuit with a bigger relay so they can charge you proportionately more - eg, if an 80A smarty costs $80, then a 400A smarty could reasonably cost $200 or more even though it's only a bigger relay costing <$40 extra.)

    Anyhow, enough product assasination.
    But likewise you could have one 15A or 30A "charge lamp" relay up front that switches other relays - eg, one 30A relay for each dc-dc PSU, one 30A relay for the other loads. Buy 5 standard 30A relays and you have one as spare.
    Different if it was ONE load that required the 70A or 100A (I never recommend paralleling switches/relays for capacity without meeting various conditions)...
    But there are many cat skinning methods....



    PS - The main drawback with the "Ultimate" isolator is if the alternator is still charging properly but dips below 12.5V etc. Although that is still the max power output "to the system", it may not leave you with a independent cranking battery.
    However that is a rare occurrence, and most reasonable people have an in-dash voltmeter for such purposes.
    The far more common occurrence for voltage sensing "smart" isolators is the unwanted switching during dips or transients, else the delays to keep the connection (which may be undesirable when cranking), or the removal of surface charge (eg, 13.7V to 12.7V) or the flattening of both batteries to disconnect voltage (12.5V? 12.8V? 11.5V?). Their switching voltages and respective delays require careful consideration. But bovinepoo about "priority charging" required no consideration whatsoever! (Besides, why limit or delay total battery power? LOL!)

  9. #9
    Who am I? HiJackZX1's Avatar
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    Quote Originally Posted by OldSpark View Post
    If you want to use the "Ultimate Intelligence Battery Isolator" (Patent Pending C22), then the charge lamp controls the relay (PAC).
    That is the best system for normal battery isolation where typical alternators (with charge lamps) are used - there are no voltage threshold issues nor switching delay issues....
    (Systems without typical rotor regulation require voltage or other sensing - eg, bike & marine systems with permanent-magnet & "stator" type alternators.)
    I dont think my alternator has a charge lamp because the PCM (ECU) is what controls that and even regulates the voltage. The new alternator will have the charge lamp and a small little piece that tricks the PCM into thinking it is still controlling the alt, but its actually the alt controlling itself.

    Most alternators charge lamp circuits will energise a typical relay, but it depends. The older (external) mechanical voltage regulators will supply several amps, but electronic regulators may be limited... Most single-wire D+ or multi-wire alternators with the L (charge-lamp) terminal will supply 0.5A to 1A.
    (I say circuit because the D+ or L is both an input and an output.)

    Only very modern alternators with EMS interaction may have problems, but there is usually a charge lamp that can still be tapped. (It's really a NOT-charging lamp.)

    And if powering a relay is a problem, then a cheap MOSFET capable of passing 100A can be used (eg, a $3 MOSFET that takes a few micro-Amps to pass 50A - 150A etc.)

    But for those that like it simple and mechanical, stuck to relays.

    The PAC relays may take over 1A to energise and that might strain the alternator (ie, it's voltage regulator).
    Hence use a smaller relay connected to the charge lamp, and that relay can switch other relays.... eg, a 30A relay can switch (say) 10-30 PACs to isolate 10-30 batteries, or switch one PAC that switches 200-500 other PACs etc.
    (That's just the same as using a more expensive "smart" isolator to power another relay(s) because the smarty doesn't have enough capacity - ie, to boost an 80A smart isolator to 400A, have the smarty power a 500A PAC instead of the load. Suppliers however prefer to sell you the same sensing circuit with a bigger relay so they can charge you proportionately more - eg, if an 80A smarty costs $80, then a 400A smarty could reasonably cost $200 or more even though it's only a bigger relay costing <$40 extra.)

    Anyhow, enough product assasination.
    But likewise you could have one 15A or 30A "charge lamp" relay up front that switches other relays - eg, one 30A relay for each dc-dc PSU, one 30A relay for the other loads. Buy 5 standard 30A relays and you have one as spare.
    Different if it was ONE load that required the 70A or 100A (I never recommend paralleling switches/relays for capacity without meeting various conditions)...
    But there are many cat skinning methods....



    PS - The main drawback with the "Ultimate" isolator is if the alternator is still charging properly but dips below 12.5V etc. Although that is still the max power output "to the system", it may not leave you with a independent cranking battery.
    However that is a rare occurrence, and most reasonable people have an in-dash voltmeter for such purposes.
    The far more common occurrence for voltage sensing "smart" isolators is the unwanted switching during dips or transients, else the delays to keep the connection (which may be undesirable when cranking), or the removal of surface charge (eg, 13.7V to 12.7V) or the flattening of both batteries to disconnect voltage (12.5V? 12.8V? 11.5V?). Their switching voltages and respective delays require careful consideration. But bovinepoo about "priority charging" required no consideration whatsoever! (Besides, why limit or delay total battery power? LOL!)
    OH BOY, when you get started I get so confused. Could I be really silly and ask you to draw what you mean? Like how it should all be connected. I think what you are trying to say that if I use the isolator the way its pictured, when I start the car, the fact that the isolator switches on, then adds the second battery to the mix, will suddenly strain the alternator. That I am understanding, its the use of other relays that I dont get. PLEASEEEEEEEEE Draw it for me!
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  10. #10
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    Confused? As with all my posts, re-read and review.
    They tend to be "tutorial", not simple.
    Many reckon they click after a few reads, and more clicks after much later review.


    If your new alternator has a charge lamp, you should be ok.

    Newer alternators still regulate themselves, it's just that the EMS may signal it to reduce output to provide better acceleration. They can do that with newer voltage-independent ignitions (CDI etc) at the expense of more greenhouse gases.


    As to "extra strain" on alternator(s) - no, that is not what I am saying. And that's all bullsh anyway. (LOL- if extra stain were an issue, modern alternators would NOT be controlled by the car's EMS. It is such a blatant contradiction...! But it's crap anyway - there is less alternator strain with bigger batteries. And only crap else specialised alternators are not self limiting.)


    The fault with the pic above is that the 2nd battery is wired to to/thru the alternator.
    Compare that to another PAC pic which should be exactly the same - but isn't - and is correct, and hence demonstrates the plethora of contradictory information out there (in this case by the same people! Which is the latest - and hence maybe corrected version...?)
    Namely - from my link above:


    The other diagram's power connection is a joke - except for voltage sensitive loads (like pre-HID lights from the alternator) or perhaps where the alternator exceeds peak load demands, or for SPL competitions (but then why have the 2nd battery?).
    (Power connection meaning the heavy alt-battery-battery.)


    The other difference is merely the different triggers or controller.
    This last one uses +12V from a voltage sensing circuit (the PAC BG-12) instead of +12V from your diagram's "Accessory" (or other +12V switch).
    That depends on how you want to control the isolation...
    If it were manual control like IGN or ACC, I'd prefer a manual switch from (battery) +12V. But that's me - I decide when I want what - eg, my HU is powered from the battery - not via IGN or ACC.
    But for automated control - like when the car is charging - I use the alternator's charge-light output. Simple! And ironically usually the simplest & shortest cable run - ie, from the alternator to the isolation relay near the main/cranking battery. No wires from the cabin etc.

    I could use a voltage sensor, but why add a device that is attempting (ha!) to tell when a car is charging when the alternator itself tells you that?
    And the alternator tells you when it is charging irrespective of whether your system is 10V or 13.8V.
    If you stall and restart, there is no cross-connection if the battery is still above its off voltage (whether 12.8V or 12.5V etc) or its disconnect timer is still ticking away. (Paralleled batteries for cranking is advantageous, but that's another issue and has other solutions.)
    And if some transient dips your voltage (eg, amp peaks, stop lights, flashers), the isolator will not disconnect because it dips below (say) 12.5V and has no disconnect timer.
    Not that I think the use of the charge light circuit instead of a more failure-prone voltage sensing "smart battery isolator" is the issue in this case..... (Marine and bike hijackers will not be entertained.)


    All that is required is a charge-light output, or an "is_charging" signal.
    Find out what current that circuit can supply when charging (eg, at 12V or the alternator's output voltage). If that can drive the relay (PAC-xxx) as well as any other loads (like attached electric fuel pump relays), then no problems.
    Older alternator charge-lamp circuits typically sunk (grounded) at least 1A for a 3W (250mA) charge-lamp plus a few other "tested" dash bulbs (eg, brake fault, low fuel, over-temp) - not that that meant they could source (supply) +12V at similar currents, but most could.
    Otherwise any signal that goes high (+12V or +5V etc) else low (GND) when the alternator is charging will do - a FET (MOSFET) that only draws uA (if that!) can be used.
    In almost every case, an add-on circuit should be cheaper and more reliable than a voltage-sensing isolator. (Reliability is ito of both simple circuitry AND no need for voltage thresholds, hysteresis and delays under differing circumstances)


    Forget the multiple relays if that is too complicated. Assume instead a single isolator that connects the auxiliary battery(s), the isolator being close to the main battery (after the fuse) with a single feed to wherever. (EG - aux battery with its fuse in the cabin or boot/trunk or trailer.)

    Assume that isolator to be a PAC-200 or other $20 140A to 250A continuously rated relay.

    Provided the alternator's "charge light" else "is-charging" output can energise the isolator, no problems. Otherwise a MOSFET else smaller relay may be needed to buffer the main isolator's coil.
    (MOSFETs that conduct over 100A with milli-Ohm ON resistances with energising currents of uA (as opposed to 60-250mA or more for relays) can cos under $3. How does that compare to a relay?. But in any case, for such FETs to turn on a relay is no problem!)


    I'd have to search for diagrams - I may have posted an updated version on the12volt.com.
    Otherwise a simple equivalent is...

    where:
    Ignore 87a.
    87 & 30 go to respective fuses of each battery (instead of IGN & Pump).
    86 is the charge lamp terminal (Reg means the alternator's voltage-regulator charge-lamp terminal/circuit)
    85 is GND as shown.


    Aha! aka At last! From the12volt.com's power inverter (last post).


    That is the same as the "relay only" schematic above, but I've started using the "relay" picture because many think the "circuit" diagram is too complicated. (Usually for those with a preference for "(just) do as I say (don't bother understanding)".)


    Dang - and there it is .... the adapted simplicon....


    That's it - bed time!!!

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