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Thread: Flat battery

  1. #41
    Join Date
    May 2001
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    ation, Loc: ation, Loc: ation.
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    16,714

    Default Re: Flat battery

    Sorry, another question. If I have two batteries in my house bank do I need a charger with two outputs thus charging them individually or a single output charging them as a bank? I believe the original setup was the latter.

  2. #42
    Join Date
    Jun 2011
    Location
    Volos-Athens
    Posts
    4,934

    Default Re: Flat battery

    Quote Originally Posted by petem View Post
    Sorry, another question. If I have two batteries in my house bank do I need a charger with two outputs thus charging them individually or a single output charging them as a bank? I believe the original setup was the latter.
    house bank implies that the batteries are connected together in parallel (so + to + and - to -) If so, you only need one output to charge them both.

  3. #43
    Join Date
    Apr 2011
    Location
    Boat- Western Med
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    5,461

    Default Re: Flat battery

    Agreed one 12 v out put to each bank not separate in this case two to each battery .
    Modern chargers normally have a few outputs to do independent banks ,
    Eg house , engine str , geny or what ever .
    Indeed they are all treated differently and can be at different stages @ diff times .
    Further more the engine outlet of the charger does the least work .
    This is because while running the pair of alternators should top up the lost charge from the two starts quickly.Theses days how ever modern EDC engines consume a huge amount of juice , feeding the ECU ,s and associating electrotwackerey to keep the thing running , so depending on the alternator(s) output sometimes via a split diode thereís not actually a great deal of spare juice available to get re stuffing the house bank after a extended period say @ anchor .The house bank(s) get there re stuff when @ the dock on charge or geny run @ anchor with the charger on .

    We have 2x180:aH for each bank ......house and starter .
    Fortunately full monitoring, so I can see how much discharged and when recharging ( alternator or mains / geny charger ) how much is being stuffed back in amp H .

    The OEM charger decayed to max out put 3/4 Ah from its 40 , my boat sparky fitted a 3 output 80 Ah .
    The 40 fitted the rule of thumb 1/4 of 360 ( 2x180 per bank ) , but he suggested an 80 , so I went with that and itís all been fine .

    For redundancy Infact we have a small 20 Ah Bosch motorcycle charger on the geny 60;Ah bat ( 400cc motor ) and turn the main chargers geny out line off .
    This is so if the main charger fails I can still start the geny or get power to it .
    We also have a 24 v to 12 v cross over switch to rob power from a either 24 v bank to start the geny .
    This set up in therory means after a geny start @ anchor we should be able to source juice from somewhere for a main engine start if for some reason we drain the house and thereís a fault with the engine bats ......very unlikely scenario .

    Happened once .
    So I started the geny and itís charger then waited 30 mins and while running started the main engines with the power and x over switches from the geny .

    My house where too flat to grab enough and the engine bats too low because they were knackered .....naturally knackered ie 5 y old etc and lost it after a day and night and 18 hrs @ anchor without the main charger from shore .
    Last edited by Portofino; 25-11-19 at 10:30.

  4. #44
    Join Date
    Apr 2011
    Location
    Boat- Western Med
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    5,461

    Default Re: Flat battery

    Regarding bat life and charger capacity .
    I,am no expert but thinking from first principles I suspect you get a better life if the time spent down low is minimal.
    So my theory with boats is not the actual number of discharges , cycles if you like or even the depth ......the 50 % theory .This theory goes along the lines of if they suffer a few , a handful of deep discharges then they are knackered .
    No it’s more the aggregate time down below a certain point .
    So a few down to less than 50 is the same in my book as hours sat at 85 % .
    Time down shortens the life .......there’s no good % down be it 50 or 15 % .
    So within the realms of physics and chemistry you need with modern none wet bats to re stuff ASAP with either the alternator(s) or charger ..........so bigger charger output as safely possible to minimise time down .

    So a day at anchor because our boat is all electric after say 4/6 hrs we start the geny and I put the charger on just to re stuff the house bats .
    40 mins an hour or so is all it takes .
    So 360 capacity I see initially 40 to 60 ah or going in and this tappers down to 3/5 very quickly in 40 mins .
    Engine hold there charge as zero / negligible drain when off .
    I think gel / AGM bats are more suited to rapid stuffing ......which is what we have ....no wet acids on my boat ,

    I know on here many go down the cheap wet acid route and almost consider bats a annual or biannual expense ......buy if you get the AGM or gel bats and figure out how to NOT let them stay down long ( sync the charger output to them ) it’s amazing how long they can last
    Last edited by Portofino; 25-11-19 at 10:51.

  5. #45
    Join Date
    Oct 2002
    Location
    Essex Bradwell UK
    Posts
    3,448

    Default Re: Flat battery

    Heavy rain, auto bilge pump, flat battery!

  6. #46
    Join Date
    Apr 2011
    Location
    Boat- Western Med
    Posts
    5,461

    Default Re: Flat battery

    Quote Originally Posted by omega2 View Post
    Heavy rain, auto bilge pump, flat battery!
    That’s my point your charger capacity ( at the dock plugged into shore power ) should be able to easily keep up the pump drain .......thus the bats don’t notice a % drop of any significance to shortening there life .

  7. #47
    Join Date
    Mar 2002
    Posts
    17,806

    Default Re: Flat battery

    Quote Originally Posted by omega2 View Post
    Heavy rain, auto bilge pump, flat battery!
    If I should find any of my bilges wet after heavy rain, that would already annoy me.
    But having enough water ingress to start an auto bilge pump would drive me nuts!
    In such case, it ain't battery draining the real problem to troubleshoot, imho.

  8. #48
    Join Date
    May 2001
    Location
    ation, Loc: ation, Loc: ation.
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    16,714

    Default Re: Flat battery

    Cringing as I write this.....

    Guys have checked my house batteries and there's no water in them*. They've added 9lt of water between the two and they seem to be holding charge. I'll know for sure when I have my swanky new battery charger that's on it's way to Spain.


    * Note to self, don't leave them for years without checking them.

  9. #49
    Join Date
    Feb 2015
    Location
    Conwy
    Posts
    4,335

    Default Re: Flat battery

    5 demerit points for brazen honesty.

    and as loosing so much water would only happen over time will effect capacity and voltage. Time to re-investigate your other issue

  10. #50
    Join Date
    May 2001
    Location
    ation, Loc: ation, Loc: ation.
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    16,714

    Default Re: Flat battery

    Quote Originally Posted by BruceK View Post
    5 demerit points for brazen honesty.

    and as loosing so much water would only happen over time will effect capacity and voltage. Time to re-investigate your other issue
    Funnily enough the other issue seems have gone away (at least for today) !

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