Coddy Posted February 20, 2005 Report Share Posted February 20, 2005 Hi Adam Just catching up on messages. One thing would worry me about your diagram is the lack of in line fuses for the 12v socket and bilge pump. I personally would add an inline fuse, easy to work out maximum current used when everything is switched on, on the main feed to the switch fused panel. Don't forget to carry spare fuses in your tool kit, just in case. Coddy Quote Link to comment Share on other sites More sharing options...
Adam F Posted February 20, 2005 Author Report Share Posted February 20, 2005 They both have independant switches which have internal fuses...just didnt log the detail on the diagram...thankf for your concern though. I carry about 20 spare fuses in BW's toolkit, differing sizes. AF Quote Link to comment Share on other sites More sharing options...
Newboy Posted February 20, 2005 Report Share Posted February 20, 2005 I thought the battery to engine cable (starting cable) will need to be a minimum of 100+a, just to handle the CCA. I would use the 30 as a minimum for equipments. Never hurt to up it to 35 or even 50 as the cost differnce would be minimal over a few meters. Quote Link to comment Share on other sites More sharing options...
Bob F Posted February 20, 2005 Report Share Posted February 20, 2005 I've added a cable size table to the article, and below is a cable size calculator and AWG to mm converter. http://www.radiomods.co.nz/powercablecalc.html The amended Battery article is attached. cheers BF Quote Link to comment Share on other sites More sharing options...
Coddy Posted February 20, 2005 Report Share Posted February 20, 2005 Hi Bob Why did you not connect the 2nd battery to the switch? On most wiring diagrams I have seen for the change over switch has the Red lead from the outboard to the common and the +ve lead from each battery to terminals 1 and 2. You can then start/charge the engine by selecting whichever battery or both you want. Regards Coddy Quote Link to comment Share on other sites More sharing options...
Paul J Posted February 21, 2005 Report Share Posted February 21, 2005 All good info guys, i too am looking at this at the moment. Iwould really like to move the batteries up under the centre consol of my boat but the leads at the moment are about 3ft short. The total run would be about 10ft from the engine. Will this work? or is it to far? Paul J Quote Link to comment Share on other sites More sharing options...
Newboy Posted February 21, 2005 Report Share Posted February 21, 2005 Not an expert, but I'm sure the longer the lead, the bigger the losses of voltage it would be. On SH, the cables are about 6'. Or how about leaving one battery at where it's at present and move the second battery to the front? i.e., outboard---> 3' cables ---> battery 1 ---> 7' cables ---> battery 2. At least engine pulls in enough power. Quote Link to comment Share on other sites More sharing options...
Guest Guest Posted February 21, 2005 Report Share Posted February 21, 2005 Not an expert, but I'm sure the longer the lead, the bigger the losses of voltage it would be. Which is a fair statement. You can get round this by using a cable with a greater cross section. There is a great book out called the 12 volt Bible. Explains what you need where and the ways to lay things out. I've found it invaluable for a few little jobs I've done over the last month or so. Quote Link to comment Share on other sites More sharing options...
petesnr Posted February 21, 2005 Report Share Posted February 21, 2005 I have two batteries on my boat, one straight off the engine and the other several feet away in the cabin wired in parallel. Basically it doesn't work as a safety back up for starting the engine as the cables to the second battery are too thin leading to such a voltage drop that the starter motor will not spin fast enough to throw out the worm and engage the fly wheel. Most discussions with outboard dealers have suggest that one good battery is more than enough on a small boat to start the engine and run the electronics however if you spend much time transmitting on the VHF when the engine is not running then you do run the risk of draining it--it may drain 12amps transmitting. If you also have a bait pump running all day you can see that your margin of reserve is diminished even more. If you have different size or length of cable to each battery then one may get more of a charge from the engine than the other. If you then have the batteries connected together the weaker charged battery may take charge from the better charged one when the engine is not running leaving you without enough to start the engine..There are several solutions. A blocking diode or a voltage sensitive resistor may prevent discharge from one battery to another. If either is fitted it needs to be connected correctly. Simpler solutions include using mobile phones or hand held VHF for routine conversations, taking a spare charged battery to power bait wells, switching off plotters and sounders when anchored etc. If you do connect a second battery use seriously thick copper cable!! Quote Link to comment Share on other sites More sharing options...
Paul D Posted February 21, 2005 Report Share Posted February 21, 2005 There is a good voltage drop calculator here :- Voltage Drop Calculator They state for a DC system you dont want to go over around 2% If I assume 100 A for starting the engine ( Reasonable ? ) then with 1 AWG size wire ( 110A ) and a length of 10 FT this gives 2.7% voltage drop. Off now to find out how much current a 50HP outboard uses when starting and the min voltage it can hack ! Quote Link to comment Share on other sites More sharing options...
Newboy Posted February 21, 2005 Report Share Posted February 21, 2005 Also like to add is that if both battery are on charge by the alternater from the outboard, the good battery WILL always get most of the charge unless a electronic router/selecter is fitted. Quote Link to comment Share on other sites More sharing options...
Adam F Posted February 22, 2005 Author Report Share Posted February 22, 2005 I have 2 batts...(im sure all of this has been covered before - Ill see if I can find the post). One is under the transom, the other is over 12 feet away in the console. They both are wiried into a battery switch which is in the middle of the transom. I simply used the voltage calculator (above) and then bought sufficiantly thick battery wire to negate the drop in voltage. It actually wasnt as think as I thought. This system works perfectly and I would recommend it to anyone. Paul - if you want a hand give me a shout. Adam Quote Link to comment Share on other sites More sharing options...
duncan Posted February 22, 2005 Report Share Posted February 22, 2005 hence the use of a 2 way switch to ensure the starter battery is always topped up before moving on to the aux. we seem to be starting to repeat previous threads here - but it's always god fun! Paul (J) I wouldn't have any qualms about sticking the batteries under the seat - the runs aren't going to be that long and your engine isn't going to need much in the way of CCA really - you could even hand start that surely? Normal battery cable will be fine. I would get a couple of new batteries (matching) from Macro and keep the receipts (3 year warante) then alternate the one used as aux each trip. link to the 12v handbook is 12v handbook it's a big pdf file and if you are going to download it (recommended) then push the button and go off to make some rigs / coffee. I've checked the link today. I don't think the club should hold the link in any reference area though. Quote Link to comment Share on other sites More sharing options...
Adam F Posted February 22, 2005 Author Report Share Posted February 22, 2005 Much is covered here: http://www.pbsbac.co.uk/forum/index.php?sh...&hl=2nd+battery and here: http://www.pbsbac.co.uk/forum/index.php?sh...1453&hl=battery and here: http://www.pbsbac.co.uk/forum/index.php?showtopic=610&hl= and here: http://www.pbsbac.co.uk/forum/index.php?showtopic=502&hl= ... you could say we could write a book on it! Quote Link to comment Share on other sites More sharing options...
shytalk Posted February 22, 2005 Report Share Posted February 22, 2005 have a look at merlin equipment in cabot lane they do battery switch clusters with voltage sensetive relays good kit and simple to fit i ve just fitted one on tiger lily Quote Link to comment Share on other sites More sharing options...
Coddy Posted February 24, 2005 Report Share Posted February 24, 2005 On my 165 I have x2 batteries. One is under the steering console and the other is sited on the seat inside the cabin along side the steering console. This was set up by Warrior when the boat was purchased. I have not had any problems with overheating wires or anything. I have just to add the change over switch and add some more switches so that I can add lights to flood the back of the boat for when I try night fishing when the warm summer nights come along! Regards Coddy Quote Link to comment Share on other sites More sharing options...
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