Looking to Upgrade DC system

Discussion in 'OnBoard Electronics & Controls' started by mydauphin, Feb 21, 2012.

  1. mydauphin
    Joined: Apr 2007
    Posts: 2,160
    Likes: 48, Points: 0, Legacy Rep: 575
    Location: Florida

    mydauphin Senior Member

    Presently I have a single DC system consisting of two 12 volt batteries connected in series to provide a 24 volt circuit and two 12 volt circuits. I have a 24 volt charger/inverter that connects to the two. I also have solar panels that charge one for the 12 volt batteries.

    I am looking to create 2 more similar systems on my boat, one for the engine room and one for the bow, and the original house. So I would have a total of 6 batteries making 3 banks of two 12 volt batteries. I hope you understand my diagram. Note: this is a large boat and my engine do not require electricity to start or run.

    My question are these;
    If two batteries are in series, does the weaker one charge the lower voltage one?
    When I parallel the 24 volt battery banks, would they charge/balance even each other?

    I guess the only way to check individual battery voltage is to disconnect battery from parallel?

    Anyway, any and all comments are welcomed. ;)
     

    Attached Files:

  2. pistnbroke
    Joined: Jan 2009
    Posts: 1,404
    Likes: 33, Points: 0, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    In series when charging the better battery would get over charged which reduces its life.
    always use matched batteries in both age and make and type..you will need to rate your alternators at 25A per 100AH of capacity . Multiple alternators are normal. If you have a 24v alternator then the 25A will charge 2 batteries as they are in series.

    If you parallel the three 24v banks then over time they will discharge one another BUT if its used ..ie charged daily or even weekly then should not be a problem . Batteries in parallel left for a long time is not a good idea ..depends on there conditon ..again should alll match for age .type etc

    Yes to check voltage you would need to disconnect but if you are looking for state of charge a hydrometer is better.

    I dont know how you are getting 12v but if its by loading one of the batteries you have in series to give you 24v ..bad idea ..this will result in an unbalanced re charge and short battery life ...

    The experts on house battery systems are at www.canalworld.net
     
  3. CDK
    Joined: Aug 2007
    Posts: 3,311
    Likes: 140, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    A small addendum to pistbroke's true words:
    There are 2 ways for batteries to show signs of age, loss of active plate surface or a low resistance path (or complete short) because of conductive sludge.
    During charging the first behaves like a good battery, but a much smaller one. The second draws the charge current of a much larger battery without ever reaching a fully charged state.
    Both are poor candidates for parallel or serial wiring unless swapping batteries is your hobby.
     
  4. rasorinc
    Joined: Nov 2007
    Posts: 1,849
    Likes: 69, Points: 48, Legacy Rep: 896
    Location: OREGON

    rasorinc Senior Member

    It ia better to connect all your batteries in a series for charging rather than 3 groups of two. You guys probably know all this but I post it for the electrical dunses like me.
    http://www.smartgauge.co.uk/batt_con.html The third method shown is the overall best for more than 2 batteries. my 2 bits.
     
  5. pistnbroke
    Joined: Jan 2009
    Posts: 1,404
    Likes: 33, Points: 0, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    re the above post ..it depends if you are doing constant voltage charging or not ...if its from an alternator its constant voltage so batteies in series other than 2x12v is not an option..if you are to put a high load on these batteries each 24hrs then you need a good engine driven alternator system to charge them and no no no no no diode split charging systems please !!!!

    A UK canal boat with say 600AH at 12v would run its engine/alternator 8 hrs a day to replenish the daily usage ....
     
  6. jamesgyore
    Joined: Sep 2011
    Posts: 101
    Likes: 20, Points: 0, Legacy Rep: 191
    Location: Melbourne

    jamesgyore Senior Member

    Wow, what a fantastic resource! Thank you.

    I've been lucky enough to pick up an obscene number of new batteries from a write-off Nissan forklift truck (one charge before I purchased them), which I know to be superior deep cycle devices.

    I was not sure how I might put them to good use on my boat, frankly I still don't, but your link has given me greater insight.

    With a little help, these batteries will not only serve as ballast with a secondary purpose, but the ridiculous amount of stored energy will satisfy every electrical mod-con with amps to spare with infrequent re-charging.
     
  7. pistnbroke
    Joined: Jan 2009
    Posts: 1,404
    Likes: 33, Points: 0, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Quote ....infrequent re-charging.

    Recepie for disaster .....
     
  8. Frosty

    Frosty Previous Member

    Bad batteries swell, yes swell,-- ie I mean gets fat.

    The outsides of the batt at the end is not flat.
     
  9. jamesgyore
    Joined: Sep 2011
    Posts: 101
    Likes: 20, Points: 0, Legacy Rep: 191
    Location: Melbourne

    jamesgyore Senior Member

    I there,

    How so? While I'm not quite done with my electrical needs calculations, I'm thinking 2~3 days to run down to about 75~80% before needing to think about charging.
     
  10. Frosty

    Frosty Previous Member

    That would be a life of hell if you were a battery. Imagine getting fed every 3 days and still having to plow a field.

    An Automatic battery charger will consiquently add years to a life of a batt.
     
  11. sdowney717
    Joined: Nov 2010
    Posts: 800
    Likes: 28, Points: 28, Legacy Rep: 274
    Location: Newport News VA

    sdowney717 Senior Member

    batteries that stay continually undercharged have shorter life.
     
  12. pistnbroke
    Joined: Jan 2009
    Posts: 1,404
    Likes: 33, Points: 0, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    if they never go over 13.6v about 6 months....
    discharge below 50% bad news
     
  13. BertKu
    Joined: May 2009
    Posts: 2,352
    Likes: 33, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    No, but you need to put 2 heavy type of Zenerdiodes made up from 4 x 2N3055 parallel and again another 4 x 2N3055 parallel for the bottom battery, which each is driven in the paralled base of the transistor with each a serial resistor of 10 Ohm and one 15 Volt 7815 regulator. In that way each battery will not be overcharged with a too high voltage , if one of the two batteries is weaker or older and thereby reducing the lifetime. I have batteries which are already charged for 8 years like that.

    Yes, and that would be bad. The best is in that case to use schottky diodes between de plus poles of the 24 Volt system. As explained in thread: "1or2 batteries by gadget300 go to the photo's in the last thread".
    No, if you use a shottky diode between the + poles, you can measure the batteries one by one, without disconnecting or stopping your gadgets connected.
     
  14. pistnbroke
    Joined: Jan 2009
    Posts: 1,404
    Likes: 33, Points: 0, Legacy Rep: 404
    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Jesus I Feel Ill all this diode parallel **** is all vespa scoota technology ..just get good batteies and wire them us in series parallel as required and sleep easy in your bed ....all this makes me feel quite ill .....
     

  15. BertKu
    Joined: May 2009
    Posts: 2,352
    Likes: 33, Points: 58, Legacy Rep: 223
    Location: South Africa Little Brak River

    BertKu Senior Member

    Untill a half year later , one of your batteries goes bad and you are happily charging two in series placed batteries. One faulty one and good one.Then I feel very ill, to see the other good battery also to go bad.
    Bert
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.