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Thread: VOLVO S80 CarPC Work in progress

  1. #91
    Maximum Bitrate rray's Avatar
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    Nice work, glad to see you still making improvements! TV is cool!

  2. #92
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    Some info mostly for my own needs (some kind of notes placed i a safe location )
    LCD+Controller board consumption - 0.3A
    PC consumption - 2.0-2.5A (0.17A in standby)
    GPS reciever consumption - 0.09A (may stay always ON...)
    I'm done with my notes

    What do you think - am I fine placing a 5A fuse for the PC, which NORMAL consumption is 2.0-2.5A (I really don't know what could be it's max consumption)?
    My worklog: VOLVO S80 CarPC

  3. #93
    Maximum Bitrate rray's Avatar
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    I added up the total possible for our motherboard (if you still are using the atom 2800), and it was 90W /12v = 7.5A. That's with everything full load. Usually you want about 3A for a screen. Don't count anything powered by USB, as that's part of the motherboard. So 10 amps would be more practical. A 5A may blow when you least expect it, and there may not really be a problem that it was protecting you from. Even if you had the 10A, almost any short would still be protected by the 10A fuse.

  4. #94
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    Thanks rray. I'm still with the Intel DN2800MT mobo. I like it - low consumption, no need of specific PSU's.

    (OldSpark, hope you'll read this post, hope, hope, hope)
    OK, in previous post I mentioned some powering things ... mobo - let's say 2.5A + LCD 0.3A + some other devices = 3A total

    I plan to control the PC's ON/OFF state by a bit different manner - car's alarm state. What I mean:
    1. When I unlock the car and the PC is OFF I'll send a PowerUP push to the mobo. (If the PC is already ON i wont send that push, because it will force it to shut down, which I don't want.)
    2. When I lock the car, it will wait for 20-30 minutes and then send push to the mobo to make it ShutDown.

    You'll ask me why - because you may stop to buy a pack of cigarettes wich will take you lets say 15 minutes. Do you really want to shut down and then ON the whole PC?!? Well in my everyday driving I stop at least twice a day for about 10 minutes (leave the kid at the morning, and pick it up in the afternoon).

    What ever, let's simply say that EVERY driving cycle the PC will stay ON for 30 minutes.
    PC consumes let's say 3A (it's less,. because only the mobo will remain ON), which means that AFTER every driving cycle I'll be consuming 1.5Ah.

    But what the he** wll happen if the PC for some reason refuse to shut down? - Hint: jump start

    OldSpark, I hope you're here, man.
    Solution: dual battery set-up with UIBI ! Everything is crystal clear here - how it works, why to use it, how to connect it. I've read every single post in all threats where "UIBI" is mentioned (not only in this forum).
    I got one of these heavy duty 12v 120A relay (hell it's big):

    The question is what kind of battery?
    I really don't want a big regular car starting battery. 1. It's big at size. 2. It's big at amperage for my needs (or I think so ...)
    Deep Cycle - cool. 1.5A which will be down every time, means that a 12V 12A battery would stay 85% full, and according to data-sheets of such batteries, this means ... a lot cycles

    OK, but in most data-sheets I read that they should be charged with 3-5A (depending of the manufacturer). I saw that you, OldSpark in one of your posts mentioned that many people use YUASA 12V 7A paralleled with their big starting battery, and they are ... still alive...
    May I place a YUASA NP 12-12 as a 2-nd battery, and how long would it last?
    Some batteries I've found and I'm able to buy here:
    GP12120 – 12 made by "CSB" - DataSheet
    Sunlight SPA 12V-12A - DataSheet
    YUASA NP 12-12 - DataSheet

    Which to choose? Or non of them? Then what type/brand? Or make/buy a charger? Help, man. I'll appreciate it.
    Last edited by VolvoCarPC; 09-17-2013 at 03:49 AM. Reason: Grammatic, sorry English is NOT my mother language
    My worklog: VOLVO S80 CarPC

  5. #95
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    What about YUASA YTX12-BS?
    I don't have a datasheet for it. I just know:
    Capacity:10Ah
    180 A (EN)
    Regular Charge Current 1.2A
    C.C.A.: 180A
    But it's cranking battery for bikes. So I don't know is it deep cycle or not (probably no, but without datasheet this can't be said).

    P.S. I found something, but it seems that it's not written by yuasa: YTX12-BS
    Last edited by VolvoCarPC; 09-18-2013 at 10:00 AM.
    My worklog: VOLVO S80 CarPC

  6. #96
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    The bike batteries will be (starting class) You could get a UPS battery of the same size as the bike batteries it is at least a deep cycle but it's not really as it is meant for high output for a short time a different type of deep cycle. So both are the size you would like but neither is really 100%. I chose the latter route and using the ups gizmo from mp3carstore http://store.mp3car.com/Mini_Box_pic..._p/pwr-041.htm it eliminates the risk of draining my starting battery when I just go to store or gas station. I have the input power from ignition power so when key is off it goes to backup till key goes on, everything is off when key is off and computer is powered down. Just a thought SNO
    Last edited by SNOtwistR; 09-18-2013 at 10:28 AM.

  7. #97
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    Thanks for your reply SNOtwistR. I know it's easier when the PC is controlled by the IGN, but my whole conception is based on controlling it by car alarm state. I even made custom controller, so the battery confusion wont change my mind
    Hey, just ask your self - do we all make those CarPC projects because we want/need the end result, or because of the fun during designing and making process. And at the end for the feel you've made something unique just with your hands, head and some help from the friends here But not only "the thing that works" but "the thing that works exactly as I wont it to be"

    Back to the battery part:
    I know that cranking batteries are to give a lot of power for short period of time and then been mediately charged.
    Deep cycle batteries are for been slowly discharged and charged latter when possible.

    But the charging process is different, and that's the part that confuses me - OK, deep cycle battery is exactly for what I need, but I can't provide proper charging process.
    I can charge a cranking battery properly, but it's not designed to be discharged regularly.
    Oh, and the place is not much - normal car battery won't fit there.
    So what to choose?

    I'm happy hearing any advice, and I'm really very thankful for that.
    My worklog: VOLVO S80 CarPC

  8. #98
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    LOL - as if I'd know!

    UPS batteries are supposed to be VERY high discharge rates (ie, discharged to "end point" in 5-30minutes) but are usually not long lived - ie, maybe only a dozen cycles.
    And Yuasa may not be what they used to be since becoming Century-Yuasa - at least that's what my supplier intimated.

    Brand-wise I still hear Deka is good, as well as Kinetic (in the USA).

    Construction type... oh heck! It's the usual question.... is the rate of discharge & recharge is more important than depth (DOD etc)? IE - you might discharge a deep-cycle to 50% or 80% DOD but because the load current is so high, a cranker may well last longer (the current wrecks the Deep Cycler before the the excessive Depth Of Discharge kills the cranker).

    So, 3A from a ~7AH to ~12AH battery for 30 minutes. Assuming I still know how to read those specs...
    A 7AH should handle 3A for ~ 60 minutes so 30m should be ~50% DOD. For a 10AH or 12AH it's more like a 20% DOD.

    If you can fit the larger 10AH or 12AH, then I'd be tempted for a cranker. My reasoning: After 30 minutes it's around its "recommended" max 20% DOD (to 80% SOC) and it is less sensitive to high recharge (and discharge) currents.
    If 7AH maybe it should be a deep cycle but I'd still be tempted for a cranker assuming daily recharging, limited recharge time, and cheaper price.

    If deep cycles are similarly priced to "normal" (crankers) then I'd be more open to a deep cycle. (Usually deep cycle like solar & UPS are more expensive).
    And for some batteries it's hard to tell what they are - they may have a compromise on plate numbers ans hence fit both camps.

    And when I say "crankers", I mean "high current" and shallower discharge as opposed to a "deep cycle" at lower current.
    When I see small batteries capable of 180CCA etc I think of UPS batteries or many paper-thin plates that are simply for a "crank" but not much else (ie, if lights are on so is the alternator).
    { Maybe I should call them suicidals? But they are akin to UPS batteries. }


    So much depends on the usage profile. EG - how long between discharge & recharge (and at what temperature)?; a long limited-current recharge time?; high discharge (or charge) current relative to battery size?


    If the PC does not turn off... A battery protector aka low voltage cutout (aka a battery isolator that disconnects at a lower voltage - ie. 10.6V).
    Generally speaking most want UPS functionality - eg,- a low voltage sensor that sends a shutdown command with enough time for a graceful shutdown before the sensor isolates the battery. Or maybe hibernate etc.



    PS - I didn't answer anything did I?
    I can't help but think of Bill's Car and Deep Cycle Battery Frequently Asked Questions (FAQ) 11. HOW CAN I INCREASE THE LIFE OF MY BATTERY?
    Last edited by OldSpark; 09-21-2013 at 05:09 AM. Reason: PS...

  9. #99
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    Quote Originally Posted by OldSpark View Post
    PS - I didn't answer anything did I?
    WOW, you did. In fact I'm a bit more confused now ha-ha-ha.

    OK, it will be at lest 12Ah, because of the need of being discharged with 3A for 30 minutes. (I'll do my best to find enough place for 14Ah one, but ...)

    So what's left to be cleared in my head is cranker vs deep cycle.

    Let me give some more info here:
    This car is driven every single day. I should be tied to a bed in a hospital so that there is more than 12 hours not drive the car
    In most cases max calm time for the car is 10 hours at night. 22:00 - 08:00.
    BUT, the car is sleeping outside and the climate here is bad: 40 C (104 F) at summer and -15 C (5 F) winter.
    Good thing is that the 2-nd battery will be in the trunk. The main battery is there, too and I do my best to make the cables as short as possible. They will be about 80-90 cm (30-35 inches).

    OK. lets say I've almost decided the battery will be YUASA YTX14-BS (it's cranker 12Ah).
    I got a 12V 120A relay.
    Cable length between the batteries will be 1 meter (for easy calculations)

    What size the fuses should be? (60A-80A ?) main battery -> fuse -> relay -> fuse -> 2-nd battery, where the fuses are as close to the batteries as possible.
    What cable gauge should be? (10-16mm ?)

    Why I think for 60-80A fuse - the relay is 120A and it is the only thing I should protect here, so 40A over the fuse sounds good for me. (Sounds good, no theory at all here, I'm just thinking)
    Well if the fuse is 80A, so the cable should be able to carry that load with no probs, right. Using this calculator for 120A with 1m cable it gives me 10mm (7 AWG) with 4% loss. But If I put 3% loss it calculates 16mm (5 AWG).

    BUT, how a human been could calculate what is the maximum float between the two batteries in the worst case scenarium, when the main battery (72Ah standard cranker) is fine, but the second battery is totally flat, the car has just been started and the alternator's k/l line has just closed the relay between the two batteries?
    I've been searching many nights about this with no answer at all. If I knows this max float I should be able to place proper fuses. Knowing the fuses size I've found a table linked from OldSpark for cable gauges, so that would be clear, too.

    Thanks for helping me.
    My worklog: VOLVO S80 CarPC

  10. #100
    Raw Wave
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    I presume that by maximum float you mean current. [ "Float" refers to the float voltage used after a battery is fully charged - ie, charge at 14.4V and when full, drop to ~13.2-13.6V to stop it discharging. At float voltage, a battery has a (small) float current, tho "float current" has also been used as the "fully charged acceptance current" when still at 144V (or 14.2V or 13.8V). ]

    The max current into a battery is related to the difference in voltages & the battery's internal resistance - ie, Ohms Law V = IR => I = V/R.
    Say the flattery is 10.6V and it has an internal resistance of 20mR (0.02 Ohms) and it's being charged at 14.4V. That implies a charge (or acceptance) current of (14.4 - 10.6)/0.2 = 3.8V/0.02A = 190A.
    BUT a battery's internal resistance increases with its state of discharge. (Quoted internal resistances aka ESR (Equivalent Series Resistance) are for fully charge NEW batteries at whatever temperature (typically 25C or ~75F).
    Hence it is near impossible for us mere mortals to calculate the actual recharge current of a discharged battery.
    Plus, when a recharge current is (initially) very high, the battery's internal voltage increases rapidly hence reducing the voltage difference and recharge current.
    After (say) 30 seconds of cranking on my Yuasa UXH12-38 (38AH UPS battery) I'd measure up to 45A initial recharge current (from 14.2-14.4V) but that would quickly drop to under 10A within about 30 - 60 seconds. (Using normal 10% of AH rules, that UXH12-38 should not have been charged at more than ~4A, else maybe 8A if using a 20% of AH max charge current rule. 45A is over 10x the "max" charge current (using 10% AH; or over 5x if using 20% AH), hence my UXH should have been most unhappy. However I used it for about 3 years. (It's a UPS battery with 10 year design life. I got it when it was replaced after 5 years (as part of typical UPS "preventative maintenance" battery replacement at half its lifespan {assuming no excessive use} but I did not start using it as my car's cranker until it was 10 years old.)

    I am now vague on the exact nature of "maximum" charge currents. Obviously the 10-fold over-current did not do much damage to my UXH. And while I can see how such damage may be very dependent on battery quality (and Yuasa were excellent quality) and various chemical blah blah dependencies, I can also se that it may not be much different to normal component ratings - ie, they can tolerate high transients for short periods. Relays and fuses can typically tolerate 10x their rated current or higher for short periods. It's usually an issue of thermal overloading - relays and fuses can take many seconds to heat up in response to the power dissipated (ie, thermal inertia). And batteries would have a higher thermal inertia (especially wet cells with liquids which can also "boil off" some of the heat).


    I reckon in your case I'd be tempted to suck it and see.
    If it were me and it were several years ago, I'd start with a 7AH battery. 7AH because they were under $50 whereas a twice as big 12AH - 15AH would cost ~3x as much. But that ~15AH - 18AH range had since dropped significantly in price - probably due to the huge increase in production for small UPS systems, emergency (car start) battery packs, electric wheel chairs, golf buggies etc. Prior to that the 7AH was the most common as used in torch and alarm applications (and early emergency crank packs).
    If I needed more than 7AH I probably would have paralleled 2 (or more) 7AH BUT that would be under the proviso that I isolated them when not in use. But for me that was/is no problem as it would only cost me a $3 30A relay plus some wiring and switch(es) else some simple circuity as opposed to the > $50 - $80 spent by those using "commercial" battery isolators (ie - voltage sensing types aka cough cough smart isolators).

    But today, I'd look at the newer costs. I might still try with a 7AH even if a 10AH or 14AH etc was the same price in proportion. By that I mean that (say) the $35 for a 7AH I consider expendable whereas $70 for a 14AH etc is not so insignificant. [ But yes, I realise the strain might break the 7AH whereas a 10AH or 14AH might cope... And that twice as big battery means LESS THAN half the strain since batteries are not "linear" (eg, see how their relative capacity increases with decreasing discharge current, or how a lesser current has a greater (than proportional) effect on increase life. Ah yes, a battery is more of an Art than a Science (unless you understand enough of the science LOL!). ]

    Incidentally, there should not be a difference between deep cycle and high-current (crankers) wrt time between charging - ie, sulfation rate is the same per unit time but is dependent on SOC (the greater its discharged, the quicker the sulfate forms). And soft sulfates become hard after about 7 days (harder to remove; may become permanent). But sulfation is more relevant to wet/flooded cells since (soft) sulfates can be bubbled off with equalisation etc voltages (above 14.4V), but AGMs do not have that luxury. (Hence why AGMs "should be" recharged ASAP after a discharge. Once an AGM "fails" due to excess flattening (and storage), it cannot be recovered.)

    LOL (not!) - the latter is a reason why you should pick the battery suited to the job - ie, the bigger the better, especially if it's going to sit a day at 80% SOC etc (ie, a 12AH would be about half as discharged as a 7AH, hence slower/less sulfation etc).


    About relay 7 fuses & cables... YAY - you know about the TWO fuses - one at each battery (power source) end.
    If it were mere cabling, being so close together you could omit the fuses if you had PHYSICAL protection (ie, no chance of a short).
    But to protect the relay, yes, fuses. Then again, a 120A relay is pretty robust and unlikely to see any currents near its rating... (No, I'll leave that. Let's stick to "automotive convention".)
    You know the drill - fuses to be rated equal to OR LESS THAN the (lowest) rating of relay or cable.
    Cable-wise, I like to design with less than a 0.5V drop, though that's for high current lights etc. For batteries, one has to consider that although greater than (say) 13V will charge a battery, by convention 13.8V is needed to "fully recharge" a battery, but greater than 13.8V (eg, up to 14.4V but often 14.2V) is needed to reverse sulfation (at least in typical automotive situations).
    But many forget that as the battery charges its current decreases and hence the cable's voltage drop and hence the battery will (hopefully) eventually see a high enough voltage.
    Design-wise I might assume the minimum current is the load (in your case 3A) plus the battery's float current, so 5A total. (2A is probably way excessive, but using a general statement that float currents of typical (big) car batteries can be up to 2A - even though they are usually 1A or less...)

    So will your "aux" battery see greater than 13.8V with 5A thru the cable? (Don't forget the ground path.)
    Since your main battery is also in the trunk, what voltage does it see?
    If you have a single-wire (D+) alternator, it should see less than 14.4V - ie, the alternator output voltage which will be 14.4V or 14.2V etc LESS the cable drop from the alternator (which varies with load - which is merely the recharge current(s) assuming the car loads are taken from the alternator).
    If you have a 2 (or more) wire alternator - ie, it has the Sense (S) terminal which connects to the main battery's +12V terminal - then you should have 14.2-14.4V etc (the alternator's voltage may be (much) higher to keep the battery voltage constant).
    If you have an older "sensing" type set to the old 13.8V or it's below what it should be, it's easy to boost its output voltage by 0.3 - 0.7V or more by inserting diodes in the Sense line. (Schottky diodes for ~0.3V; silicon diodes for 0.6V - 0.7V.)


    Re fuses, if you use 50A or larger I don't see problems. I doubt that a 20AH or smaller battery could take anywhere near 50A recharge current...
    If you used smaller, then you may have seen my self resetting circuit breaker recommendation. That came about after my UXH or wet-cell (~40AH) "aux" battery plus a max 8A load would occasionally blow the 30A fuses I had. Though I could have used some plug-in ATS 30A self resetting CBs (the largest made in the ATS blade fuse package), I used a pair of 50A self reseters - the largest "cheap" self-resetting CB (< $10) with a small size with threaded posts and weatherproof. (I use a 60A else 140A relay and a dual-conductor (+12V & GND) cable that is more than copious.)


    I could go on, but it's nearly 04:30 and my bottle is finished, and I need to sober up (BEFORE I install mum's new digital TV...).

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