Battery wiring systems for multiple banks

Discussion in 'OnBoard Electronics & Controls' started by ScubaDude, Mar 29, 2011.

  1. ScubaDude
    Joined: Feb 2011
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    ScubaDude Junior Member

    I am in the process of trying to upgrade some of the wiring on our charter boat. Right now there are two Vovlo 4 cylinder gas engines, each of which has a starting battery. The starboard starting battery also serves as a house battery. To me that's not very good. Here's what I'm planning on doing (just for starters - no pun intended). I'm going to add a third (deep cycle) battery to act as the house bank and add one of BEP Marine's battery cluster devices to allow for easy emergency paralleling of the start batteries if necessary.

    BEP Marine makes two similar devices, one which they say is for twin inboards, with one VSR and the other which they label as being for twin outboards which has two VSR's.

    Here are links to the products in question:

    http://www.bepmarine.com/home-mainmenu-8/product-280/718-100a-twin-inboards-three-battery-banks

    http://www.bepmarine.com/home-mainmenu-8/product-279/717-100a-twin-outboards-three-battery-banks

    In the text of the Inboard model (with one VSR) they say:

    "The 718-100A is designed for twin inboard systems when it is not practical to have both engine alternators in parallel because of the types of regulators used on these alternators. "

    Can someone explain for me what it is about the alternators on the inboards that would make it "not practical" to use the system with them? How do they differ from those on outboards?

    All else being equal, it would have seemed to me better to be able to charge the house bank from either engine.

    I would also welcome any thoughts on the subject and any suggestions for other comparable products or solutions. I'm trying to end up with a reliable system without breaking the bank. (I looked at their motorized switches, which are nice, but not for three times the price of the manual switches.)

    Thanks for your input.
     
  2. Ike
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    Ike Senior Member

    Well this could be a long post, but I''l try to keep it short. Alternators (inboard or outboard) are good at "maintaining" batteries at their current charge level, but for keeping batteries fully charged you need a separate charging system. Also there is usually a difference between starting batteries and house batteries. Starting batteries are specifically designed to discharge a lot of current very rapidly, and recharge very rapidly. Housee batteries are usually deep cycle batteries designed to discharge slowly over much longer periods of time, and they take longer to recharge.

    This is not to say you can't use one or the other for each task but that is not what they are designed for. And if you want your batteries to have a long full life then it's best to do it right.

    To correctly charge batteries up to their max you need a 3 or 4 stage smart charger that doesn't just pour electrons into your batteries. It measure the state of the battery and adjusts the charging rate accordingly. See Batteries: Everything you need to know http://newboatbuilders.com/docs/BatteriesEverything.pdf and Batteries and Chargers http://newboatbuilders.com/docs/BatteriesandChargers.pdf
     
  3. michael pierzga
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    michael pierzga Senior Member

  4. pistnbroke
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    pistnbroke I try

    forget all this 4 stage ***p batteries have been charged for decades by car type alternators ....you can do all you want with a cheap $10 30 A relay ...coil goes from alternator warning light terminal to earth and the contacts join the two battery positives. it is advisable to put a 1n4005 diode across the relay coil ..the band end goes to the alternator end. Put a fuse near each battery connection.

    If you want get a simple VSR ....voltage sensitive relay 3 wires one to each battery and one to earth......

    Outboard alternators are usually under the flywheel often with shunt regulators and dont have a big output ..120w inboards are usually marinised vehicle types with proper voltage regulators .output 1400w ..two vehicle alternators can be put in parallel no problem ...and often are ...you will not charge your aux battery at over 25 A whatever you do or are told and most of the time it will be getting about 15 A
     
  5. BertKu
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    BertKu Senior Member

    Pistbroke, you better tell him, about the polarity of the diode. Otherwise he is wondering why suddenly the diode burns like a small light.
    Bert
     
  6. pistnbroke
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    pistnbroke I try

    I did .....the end with the white band to the alternator warning light connection.

    On most alternators this is not neccessary but some alternators have weak field diodes for for 5 c its worth it ...
     
  7. Roger G
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    Roger G Junior Member

    Another Option?

    I went an entirely different way when I started our rewire on our 1978 Sedan last winter. It is a simple system and works well for us but since I have found this forum with so many knowledgeable people willing to share information I thought I would offer up my solution for comment or criticism.

    Our new set up has one 27 series start battery wired to one battery switch that supplies power to both engines. This battery is charged by the stock 40 amp alternator on the port engine and powers nothing else. The theory here is that only one engine is ever started at one time. Standard procedure for us now is to start the port engine first. The boat did come with two start batteries and I could hook them up in parallel but there seems to be lots of juice to fire up the engines with just the one.

    Our house battery bank consists of four 6 volt Golf Cart batteries. They also came with the boat. I built the battery box with room for eight to upgrade when it's time to replace these four. These are charged by a new 140 amp alternator mounted on the starboard engine. All of the existing wiring to the old 40 amp alternator was removed and new cable run from the new alternator directly to the house bank positive bus.
    This bus feeds power to,
    -House Battery Switch that feeds power to the new DC Panel that powers everything that is not engine running specific.
    -The windlass
    -The 1750 watt Inverter with transfer switch and galvanic isolator for the AC side. (another story)
    -A crossover battery switch that joins the two banks in case of emergency.

    This system has worked well for us but I don't hear of others that do it this way so I thought I would ask. Roger
     
  8. pistnbroke
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    pistnbroke I try

    All you are saying is that you have two alternators ..one charges a single start battery for both engines and the other charges the house battery ....easy but think of this .....when the house battery is charging the other alternator is doing nothing .....you could use both to charge the house battery and hence charge it faster ..common canal boat practice in the UK ......you should rate your charging system at 25 A per 100AH of house battery capacity to charge in the shortest time......if you want to do this let me know you carnt just put a switch in its best automatic...
     
  9. BertKu
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    BertKu Senior Member

    Yes, that could be done, but one should measure the output voltage of the regulators, If they are varying in the way I have tested a number of them and to my horror are varyng from 14.25 to 14.65 Volt, instead of 14,4 Volt, it still does not help you very much. Provided both alternators are nearly equal in the regulating voltage, you are right. It is a better option. ( a few millivolt could be absorbed in the cable resistance)
    Bert
     
  10. pistnbroke
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    pistnbroke I try

    if any regulator is below 14.4v you should change it ......but they do not need to be a matched pair as during the bulk of the charging of a house battery the voltage is below 14.4v so neither are regulating....When the voltage rises the one with the higher voltage regulator setting will have sufficient capacity to top off the batteries.
    Two critical things for charging are reg 14.4v -14.7v and a capacity of 25 A per 100AH.
    HOW TO DO IT
    There are two methods but I dont like putting all the alternator output through one diode...so remove the rear cover from the starting alternator and attach 3 wires of 4 mmsq size to the three output wires of the Stator ..bring these out of the alternator and connect to a three phase rectifier bridge rated above the output of the alternator ( cheap on internet) and connect the output of the bridge to the house battery. The house alternator just connects to the house battery as normal. The point of this is that if you try to just connect the alternators to the house battery the starting battery will discharge into the house battery defeating the object of always having the starter battery charged....now please dont argue about it that is how its done on hundreds of canal boats in the UK and has been very successful in reducing charging times ....
     
  11. BertKu
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    BertKu Senior Member

    There are a few comments I like to make. If everybody jumps off the Eifel Tower, I may not jump also, unless a good reason is provided.

    On the one hand I hear you, which make sense, if all the parallel connected batteries are from the same manufacturer and approximately the same condition. However, the last 10 years there has been an extra effort to improve the Lead batteries, either because of the cost of lead, or just other reasons like low maintenance.

    What I understood from the fellow at the Laboratory of a Lead Acid Battery manufacturer, that with adding other materials like Nickel etc. or a modified chemical liquid or gel. the Charging Voltages per cell varies now between 2.30 and 2.40 Volt per cell. i.e. 6 cells means 13.80 Volt and 14.4 Volt.

    If one goes to the shop and buy a battery, I bet you, that the fellow who sells you the battery has no clue, whether it requires 14.4 Volt Charging Voltage or 13,8 Volt or somewhere in between.

    Only the automotive or diesel generator manufacturer knows the facts and therefore I concluded that the KIA with the gel battery needs a lower charging voltage then my Old Colt Diesel which probabbly had 10 years earlier an old fashioned 14,4 Volt Charging required battery under the bonett. The KIA may need only 13.8 Volt. Because the Colt battery was exchanged and replaced by a gel type of battery, I blew the battery when driving at cruising speed for 1200 km and blew the battery.

    No wonder that the Automotive manufacturer insist on origional parts. And also no wonder why the modern batteries don't last anymore. Half of them are not matched to the regulator no longer. I want change my regulator, I will investigate what Voltage is required for charging the present battery I have.

    For the rest of your reply, I intend to agree (except batteries placing parallel)
    Some nice information was attached in the other thread.
    Bert
    Bert
     
  12. pistnbroke
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Most of the modern vehicle alternators are controlled by the ECU ...goes up to 14.4 and then drops back to 14.1 or2 ...no adjustment possible ...I am talking alternators for boats or cars with internal regulators ....
     
  13. Frosty

    Frosty Previous Member

  14. pistnbroke
    Joined: Jan 2009
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    Location: Noosa.Australia where god kissed the earth.

    pistnbroke I try

    Well frosty its What ARE you talking about .....I was replying to bert about his point on battery charge voltage ...this is now ECU controlled on most cars and has been for a few years ..they use 8 diode alternators you know ..no field diodes ...are you saying you are not up to speed on this ...

    How are you on CAN BUS vehicle wiring ...

    So what are you talking about .....
     

  15. ScubaDude
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    ScubaDude Junior Member

    First of all, thank you everyone for your comments, answers and links. I've learned a great deal... which means that I have more questions. First I'd like to state what I think I've come to understand. Would someone point out if I'm way off base any of these please.

    The first point I take away from this is that the charging voltage is critical for whatever batteries one has, both in terms of getting as much energy into them as they can hold at any given point in time and also with a view to maximising their working life.

    Next is that in an ideal world, a 3 or 4 stage charging system would be best.

    Next is that in the real world, it is likely that I can keep both my starting and house banks reasonably well charged and get reasonable battery life with the regulated alternators that I have on the engines (provided that their output is correct for my batteries).

    Questions that remain in my mind: In the two VSR distribution cluster referenced in post 1, if both engines are running, is the house battery indeed being charged from both alternators?

    The SmartGauge system does look like a great piece of kit. Am I correct in how I read their schematics that this system in and of itself does not provide emergency parallel capability. So I would need to add at least one switch to combine the batteries if I installed that system and also wanted to be able to do have emergency parallel capability, correct?
     
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