Page 1 of 3 123 LastLast
Results 1 to 10 of 24

Thread: Reccomended Standby Battery

  1. #1
    Jesus Freak antimatter's Avatar
    Join Date
    Jan 2004
    Location
    California
    Posts
    4,545

    Reccomended Standby Battery

    Currently i use a sealed lead acid battery from a UPS.

    I am killing these batteries because i believe they are undercharged and overworked.

    I am looking for the best most rugged type of Deep Cycle battery that i can get that will withstand being deeply discharged and recover well.

    Currently with my driving habits i only get long periods (about an hour) of charging twice a week so it should be able to withstand a 250 ma standby draw inbetween these times and be able to recover fairly fast.

    Am i asking too much of a battery?

    I am hoping one of the heavyweights have something brilliant to add to my battery problem
    -Jesus- King of Kings Lord of Lords

  2. #2
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    878
    Just a quick reply, I could be wrong but IMHO (as you suggested) you’re asking a lot because of the small charge time.

    I described the problems I had with this and the battery I’m using in post 66, 67 of my worklog. I’m drawing around 320ma but even a constant 250ma over a few days with a short recharge time is going to be a problem for any battery.

    Have you accurately measured the charging voltage across the AUX battery in relation to the Main Battery. IE how much voltage drop do you have between the two and importantly, can the Vehicle charge system supply enough voltage to correctly charge a Deep cycle battery, which can be as high as 14.6v to 14.8v.

    Hopefully OldSpark will correct the voltages I quoted if I’m wrong!
    Last edited by Mickz; 11-15-2011 at 06:14 PM.
    Surface Pro 2 128GB portrait mode, Win8.1, Reverse camera, Dual 10HZ GPS RX's for Speed Display & Sat Nav, FM-DAB & Phone Modules, iDrive interface. T-Screen HVAC control, custom microcontrollers, microcode and FE. Previous Car-PC Project

  3. #3
    Jesus Freak antimatter's Avatar
    Join Date
    Jan 2004
    Location
    California
    Posts
    4,545
    The charging voltage is around 13.7 back where the aux batter is. Not sure exactly what the alternator is putting out. Maybe the problem is the 8g wire and the distance that i have in between the main battery and the aux battery. I have the Aux battery and isolator in the trunk.

    Maybe i should hook up a solar charger or something to supplement the charge from the alternator.

    Quote Originally Posted by Mickz View Post
    Just a quick reply, I could be wrong but IMHO (as you suggested) you’re asking a lot because of the small charge time.

    I described the problems I had with this and the battery I’m using in post 66, 67 of my worklog. I’m drawing around 320ma but even a constant 250ma over a few days with a short recharge time is going to be a problem for any battery.

    Have you accurately measured the charging voltage across the AUX battery in relation to the Main Battery. IE how much voltage drop do you have between the two and importantly, can the Vehicle charge system supply enough voltage to correctly charge a Deep cycle battery, which can be as high as 14.6v to 14.8v.

    Hopefully OldSpark will correct the voltages I quoted if I’m wrong!
    -Jesus- King of Kings Lord of Lords

  4. #4
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    878
    Yes, 13.7v is not really enough; I also have mine in the trunk and 4G cable would be the way to go especially as the battery gets larger and capable of drawing a higher charge current. Quite a few things to consider with charging current, charging time and heat etc if you let them discharge too far.

    OldSpark posted a really great link on batteries and charging which would be worth reading.

    I was thinking of suggesting a sola charger if you can get a decent large unit without breaking the bank.
    Surface Pro 2 128GB portrait mode, Win8.1, Reverse camera, Dual 10HZ GPS RX's for Speed Display & Sat Nav, FM-DAB & Phone Modules, iDrive interface. T-Screen HVAC control, custom microcontrollers, microcode and FE. Previous Car-PC Project

  5. #5
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    SLAs? You mean AGM?
    (Yes, AGMs are SLAs, but so to are Gels, and many refer to semi-sealed wets as SLAs...)
    And is you battery a stand-by, or cyclic?



    Rule of thumb - no more than 50% DOD (depth of discharge) for deep cycle batteries.

    UPS batteries are designed to be discharged VERY deep - eg, down to nearly 10V BUT at a fast rate (HIGH current) - BUT should be recharged ASAP and they may only last 6 cycles (ie, 6 days if once a day).

    UPS are not cyclic batteries - they are not for daily use. (Says I that has been using an undersized 11 year old 38AH UPS AGM battery for my main and only car battery for maybe 2 years - but that is recharged immediately after cranking (at up to 45A!). Besides, it's a Yuasa.)



    Get a bigger battery, but you must be recharge it fully at "reasonable" intervals.

    Whilst a smaller battery might be ok for the discharge, it might require a longer charging time.
    A bigger battery can accept higher current & hence recharge in a shorter time. Plus since it only discharges maybe 40% rather than 60%, it will last longer.



    What you describe is what cracks me up on car audio sites. Yes, the battery does this or that, but for how long? (As in lifetime, not discharge time.)
    Luckily audio forum people are prepared to spend big on batteries, & often.


    Batteries are a compromise.
    What ages them is the combination of higher discharge current, higher recharge current, over-voltage, higher depth of discharge, higher temperature, more frequent use and the number of recharge/charge cycles.
    Now and again they require maintenance - eg, a high voltage or high-current recharge to blow away sulfation etc.

    UPS batteries are designed for high discharge rate & high DOD, but NOT for many cycles.
    Solar batteries are designed for long discharge periods with relatively low recharge rates and high DOD.
    Deep cycles are low current but high DOD.
    Crankers are for cyclic use, high current, low DOD. (So why to audiophiles want deep-cycle for voltage dips??)
    Alarm batteries are "stationary" aka non-cyclic and can be similar to UPS batteries bit with a lower discharge rate (current).

    And on it goes.
    There are only two main types of battery construction - namely crankers (high current) or deep-cycle. But there are many flavors... And then whether AGM, gel, or flooded/wet (for lead-acid batteries).



    As to voltages, it depends on the battery.
    The norm is not to exceed 14.4V long-term, but that assumes typical 12V vehicle batteries.
    Some require higher - eg, Optima, and Mickz' example.
    [ To combat sulfation (which occurs when a battery is not fully charged), voltages >14.4V are used. Hence probably why deep-cycles are higher - it's a compromise voltage - it might be better to use a higher voltage for desulfation (reconditioning) and then drop to normal 14.4V to limit gassing. ]


    What is the best battery depends on the combination of discharge and charge availability, and desired lifetime.

    Keep in mind that if a Deep Cycle says it's good for 80% DOD, it will last probably 3x longer if only taken to 50% DOD.
    And any "hot" battery will last twice as long if 10°C cooler, or 4x as long if 20°C cooler etc.


    BTW - yet again, download the Car and Deep Cycle Battery Frequently Asked Questions (FAQ) 2011 zip (updated October 9, 2011) from s19. It's probably the best info you will find for "battery basics".
    Last edited by OldSpark; 11-15-2011 at 08:15 PM. Reason: spellinks...

  6. #6
    Jesus Freak antimatter's Avatar
    Join Date
    Jan 2004
    Location
    California
    Posts
    4,545
    I am not sure what type of battery it is (AGM) etc. And it seems though it is a standby battery it is more cyclical and regular use battery

    I do know that I have to have something that can be inside the car. It looks like of the types you listed that a solar battery may be best but I am not sure they are a "sealed" type battery

    Thanks for the advice on the larger battery. That makes sense. I would be happy if I got 1 year out a battery (longer would be great)... currently I am only getting 3 months.
    -Jesus- King of Kings Lord of Lords

  7. #7
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    Can you indicate what sort of drain (250mA?) for how long, and then what charging for how long - eg. 1 hour car drive or 2 hours with 800mA charger).

    I might be able to size a suitable battery, though that's largely a "theoretical" sizing based on whatever specs I can get.
    There can be a large variation between "theory" (though that's usually conservative - you might get away with smaller/cheaper) and the practice is tricky - ie, alternator may have 30A spare capacity, but the battery only accepts 5A and "dropping" lower ), and then my out of practice "practical" battery skills.

  8. #8
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    878
    Just remembered something about my system that OldSpark made me remember.

    The charging voltage in my vehicle is primarily governed by the state of the main battery. This is a computer controlled charging system that knows when the AC, lights etc are on and adjusts the output accordingly. What I found was in day time driving the charge voltage can drop back very quickly and appears to be mainly determined by the current consumption of the Main battery.

    So even thought the AUX battery may be low in charge, because the current drawn by the smaller AUX battery is minimal compared to the total System, the available charging voltage can drop to around 13.8 very quickly. I feel the vehicle cranking battery charges a lot faster than the smaller and most likely more depleted AUX.

    With a battery in the trunk or cabin and even with a relay bypassed isolator (minimal voltage drop) and heavy wiring you may still not have sufficient time to charge that AUX battery correctly before the charging system cuts back.

    This is the reason I went to the trouble of having a single button Hibernate at the end of the day’s driving, instant on (auto sleep) during the day and resume from Hibernate 1st start of the day. Since doing that and limiting the discharge time I have not had a problem charging the AUX with low driving times.
    Surface Pro 2 128GB portrait mode, Win8.1, Reverse camera, Dual 10HZ GPS RX's for Speed Display & Sat Nav, FM-DAB & Phone Modules, iDrive interface. T-Screen HVAC control, custom microcontrollers, microcode and FE. Previous Car-PC Project

  9. #9
    Raw Wave
    Join Date
    Nov 2009
    Posts
    2,118
    Mickz - your second para is interesting....
    "...charging voltage ... primarily governed by the state of the main battery..." & "a computer controlled charging system that knows when the AC, lights etc are on and adjusts the output accordingly".

    That's what regulated systems have been using for decades - even the old external electro-mag regulators since alternators began appearing in the 1960s (before that they were dc generators, though they are still regulated).


    I often ask people if their system includes current sensing (especially for those {cough cough} "priority charging systems".
    If it is not monitoring current, how can the system possibly know how much current is being drawn, or if the battery is full?
    Lets ignore "intelligent" chargers for the moment. And that may include your computer controlled charging system - maybe it is truly "testing" the battery state, but few in-vehicle charging systems and battery isolators do despite their claims to the contrary. (CAVEAT - but times are changing, and I'm an Old Fart that may need some updating! But I am referring to established products that have since dropped their misleading claims.)


    The "load sensing" claims are understood with TWO bits of info.
    (1) A battery charging system is a "constant voltage" system.
    (2) As loads increase, the voltage decreases so the alternator increases its (current) output to restore to the voltage set-point (and vice versa) - that is (Voltage) Regulation.

    Hence why traditional alternators (voltage regulators) have no current sensing - they merely sense the voltage (and vary the rotor current to compensate).

    And there the story ends.

    ...except for some things....
    "Computerised" regulators may simply be digital equivalents to traditional analog regulators, but it is possible that they use pulse-techniques to determine battery condition - or maybe even data sampling and comparisons. (Could the former be hazardous or noisy for modern electronic accessories??)

    The voltage set-point was traditionally 13.8V - the "theoretical" charging voltage for a 6-cell = 12V lead acid battery. (Hence the traditional 13.8V spec-rating for 12V loads.)
    But (in the 1980s?) that voltage was increased to a max of 14.4V, or typically 14.2V, as they found the batteries would last longer. (Despite slight gassing and higher charge current, the "reconditioning" of the battery meant longer life than that lost through the added "damage". IE - the slight sulfation of car batteries was largely removed with the increases charging voltage.)


    Elsewhere I have written how batteries have a "rated" maximum charge current. Yet this is probably exceeded by most vehicles - ie, all the spare alternator capacity can be used to charge the battery. I have seen my 38AH AGM battery charge at 45A, and that is slightly more (LOL!) than the usual 4A or 8A maximum allowed based on normal battery specs. (Hence aren't we breaking the battery specs and voiding their warranty?)
    What limits all the spare alternator capacity being used is the internal resistance of the battery. (My alternator probably has 75A spare capacity.)

    But that apparent over-current isn't all to bad. After all, the batteries last for years. (I get 6-8 years from my normal wet batteries, though they'd probably only accept ~20A due to their higher internal resistance (typically twice that of AGMs) - but that still exceeds their typical C20/10 or C20/5 = 40AH/10 or 40AH/5 = 4A or 8A max charge current.)

    Why isn't that over-current so bad?
    That high current helps blow away sulfation. (My battery supplier reckons at least 20A is needed after a typical car battery is flattened.)
    That high current (40A) only lasts for tens of seconds. It is well under 10A within one minute.
    In such a short time, the battery hasn't enough time to heat up (or gas) which is the big killer. (Maybe if the plates warped from the high current, but is that a heat issue too? Surely it's not an electro-magnetic attraction - lead is non-magnetic?)

    Plus specs are typically condensed. They are simplified for typical consumption, hence have typical use and long term specs - ie, charge currents & voltages for batteries, though specs are similar in "abridged simplicity" for almost any device. (Alas I recall LED discussions!) Specs are generally not "rigged" for extra sales. (Well not here - they'd be fined or sued, else go broke under warranty claims.)



    Alas I sort of digressed. Again.
    I guess I'm trying to impart that old "Batteries are more of an art than a science" philosophy. (Though that art IMO becomes "science" when you can start quantify expected behavior given enough conditions - and the plethora of info that colors the basic science.)

    And again I try to impart an understanding of batteries. If some basics are understood, they aren't too complicated.
    Mind you, that's a big ask. There was a (big?) time difference between my "knowing" of things and the later "understanding" of them - ie, where it became intuition and pictorial rather than a set of V=IR formulae!


    I think it was you (Mickz) that thanked me or was rapt at my previous linking to Bill Darden's Car and Deep Cycle Battery Frequently Asked Questions (FAQ).
    I still reckon read Bill rather than me for battery theory. I just try to tailor his gamut of info into plain English for a given situation. (Though his English is IMO far better than mine!)
    Bill probably answers & confirms some of my assumptions or suggestions from above & elsewhere. [But again, if we differ, please let me know. PM me if needed.]


    Poo, where were we?
    Charging with an aux battery...
    Assuming a relay-connected battery, then excluding (fuses & relay & ground and) cable voltage drops, both batteries see the same charge voltage.
    They then accept current based on their own internal resistance (which decreases as the battery charges).
    And as they charge, their charge-current drops until they reach their "float" current (ie, when fully charged) which may be up to 2A but can be as low as 10mA or 100mA etc.
    At 10mA to 2A, voltage drops along the distribution path should be negligible (ie, ground, relay, fuses, cables). ERGO - all batteries can be fully charged. (That's a point missed by many that get sucked in by expensive dc-dc converters or aren't clever enough to reduce cable etc resistance to aux batteries.)

    If the above batteries also have loads hanging off them, the load current must be factored in to the distribution voltage drops, but that's where fatter cable comes in.
    Plus for the main battery, loads are effectively taken from the alternator or or fuse box, not from the battery terminals themselves. And since alternators usually sense the voltage at the battery +12V terminal, the main battery gets its proper set-point voltage (ie, alternators with S or Sense inputs - NOT single-wire D+ alternators, and ignoring ground voltage drops between the alternator and battery).
    [ For those that read a recent thread involving diode isolators, that is one reason they are no longer used. The diode voltage drop depends on the current to each battery, and some loads must be connected to a battery - not the alternator - otherwise the engine won't start and will stall if the alternator fails. Incidentally, at great risk to myself, I established that our Police use relays to interconnect their dual batteries, and that relay is controlled by their Delco Memcal (ECU). I have yet to confirm ambulances etc, but some looked at me funny when I mentioned diode isolators - ie, like "how old is this old fart!?". ]


    So given a low voltage loss relay or direct connected multi-battery system, and copious alternator capacity, the time to recharge any battery is determined by the charge voltage, the depth of discharge, and its internal resistance.

    Should I have put that last line first? (LOL)
    Last edited by OldSpark; 11-16-2011 at 03:49 AM. Reason: Improved reading.

  10. #10
    Maximum Bitrate Mickz's Avatar
    Join Date
    Sep 2009
    Location
    Australia
    Posts
    878
    Yes I agree with what you are saying, however my definition of sensing when the lights are on/off etc is having the CPU know what parts of system are responsible for the current being drawn. This is easy to tell without having to measure each circuit as that information is already available to the CPU.

    In older systems (in least in my old cars) the regulator only knew that current was being drawn and “attempted” to maintain a set voltage. This new system can reasonably calculate which parts of the system is drawing current.

    Would this not allow a designer to more intelligently control the charging system to help control long term overcharging and allow short term high charging to be kept within limits based on a rough estimation of what parts of the system are actually drawing power? Or is it simply not worth trying with the batteries we currently use in motor vehicles?

    The system in this vehicle has a 110A alternator @ 13.5v and an ELD device to measures current, I assume most new vehicles would do this?

    Your point about cable loss and taking into account the equipment current (PC) if mounted near and on the AUX battery feed is so true and as you say, often overlooked. Something I have bought up before with say 7A charge and 5A for the PC, the resulting 13A is enough to drop an easy 500mv to 1v or more across undersized relay contacts, fuse holders, connectors and cables and I would think would prolong the AUX battery’s ability to charge correctly by some considerable margin.
    Surface Pro 2 128GB portrait mode, Win8.1, Reverse camera, Dual 10HZ GPS RX's for Speed Display & Sat Nav, FM-DAB & Phone Modules, iDrive interface. T-Screen HVAC control, custom microcontrollers, microcode and FE. Previous Car-PC Project

Page 1 of 3 123 LastLast

Similar Threads

  1. Laptop car PC, Power killing battery when on standby
    By mcoutlawz in forum Power Supplies
    Replies: 4
    Last Post: 01-07-2009, 01:49 PM
  2. laptop standby -> hibernate on battery doesn't work
    By dazman2 in forum How to Power a Laptop
    Replies: 8
    Last Post: 10-06-2008, 08:05 AM
  3. wiring SLA battery as standby (S3) power
    By ~docfx~ in forum Power Supplies
    Replies: 17
    Last Post: 10-26-2006, 08:16 AM
  4. Replies: 3
    Last Post: 08-04-2004, 05:52 AM
  5. Will leaving Windows in Standby drain battery?
    By slffl in forum Power Supplies
    Replies: 34
    Last Post: 08-03-2004, 10:57 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •