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Old 16 March 2015, 08:04   #11
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The thought of two batteries crossed my mind, how do you charge both?

Bring one home and charge it? or have them setup that while engine is running they both charge simultaneously?
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Old 16 March 2015, 11:26   #12
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Having them in parallel will charge both simultaneously (acts as a single double size battery.) You can also wire them through a battery switch (Off-A-B-Both) which will allow you to run and charge off either battery or both (never run on off - you'll fry the charging circuit on the motor.) Or you can get a device that fits between batteries such that you run off A, but the charge will make it to B if the voltage at A is higher than B (you'll still need a switch to be able to run off B if A is depleted, I think.)

In a small boat that's not going miles offshore and spending long times with motor off and accessories on, a dual battery setup is probably pretty close to overkill. Equipping for every possible failure will quickly overwhelm your available space (and wallet.) Depends on your intended use, of course.

jky
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Old 16 March 2015, 13:31   #13
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Originally Posted by Dirk Diggler View Post
We obviously went to different schools, as that's a 1st for me. :-)
I suspect we did! Although its not a school of thought I use myself but it won't take too long searching here to find those who do. And not just here:electrician says vhf should go straight to battery [Archive] - Yachting and Boating World Forums

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Would you suggest putting a switch on the depth sounder and bilge pump?
Yes. You definitely want a switch on the bilge pump (even if it is auto) they can munch batteries quite quickly. I see no reason not to have one on the sounder too - in which case you'll be as well with a little panel of switches.

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And depending upon size of Rib even for a one engine set-up you may want two batteries,
I'm guessing going from the OP's level of question and the sort of electrics he's talking about its not a big rib.

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The thought of two batteries crossed my mind, how do you charge both? Bring one home and charge it? or have them setup that while engine is running they both charge simultaneously?
You can set up as Boris/Jky are talking about, with switches or fancy automated devices - but (i) its something else to go wrong; (ii) you probably don't need it [with two batteries and no switch you'll only be marginally less likely to end up the proverbial creek with no paddle anyway - as you can still run both batteries dead and probably will get little warning that one is on its way out]. However if you only have 1 battery it is a good idea to learn how to pull start your engine (its possible with surprisingly big engines!)
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Old 17 March 2015, 05:32   #14
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I suspect we did! Although its not a school of thought I use myself but it won't take too long searching here to find those who do. And not just here:electrician says vhf should go straight to battery [Archive] - Yachting and Boating World Forums
Lol, that's just a load of comments on a forum, which as we all know doesn't make it sound advice.

I can see the benefits of wiring the VHF directly to the battery switch, via a fuse of course, but it's not something that I would do myself. I think rummaging round the engine compartment of a 40 foot cruiser looking for the VHF fuse isn't really the way to go, or even having to pull the jockey seat apart on a 16' rib is a no no. Also, if you decide that's the correct way of wiring, then how would you tackle a twin battery installation, or a twin rig set up.
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Old 17 March 2015, 07:12   #15
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Lol, that's just a load of comments on a forum, which as we all know doesn't make it sound advice.
Thats why I described it as a School of Thought not "good practice". The problem with wiring to the isolator switch is if the wiring starts smoking - first thing you'd want to do is kill the power to everything via the big red switch. Of course you can turn that on its head and say if the radio wiring starts smoking and you have no isolator wired in...
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Old 17 March 2015, 08:24   #16
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Yes two batteries are always a good idea, when I bought my rib it only had one battery so I installed a second battery with a simple switch unit to switch between batteries (I have a better set-up now) anyway heading through entrance of Poole Harbour the original battery dies, electronics switched off then engine started to fade and died, a simple switch to second battery saved my bacon.
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Old 13 April 2015, 12:16   #17
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Hi

With the fear of igniting a dispute as others may well have other views, I have done rigging from scratch and rewires on about half a dozen boats now and this is what works best for me.....Batteries, I go for two (75AH a piece) I don't use the normal switch arrangement. I use one of the batteries as my working battery and the second one sits as "backup only" cabled in parallel with a switch on the +ve cable bypassed with a high current rectifier diode for charging the backup so you can forget about it. At the console end, -ve (ground) bus-bar and a 6 or 8 way blade fuse box (less than a tenner on ebay), tie the inputs of half of them together and you get a string of fused outputs for equipment. I'm always wary of hanging things of "ignition control" in case I fry something expensive and the easy way round this is to power things like fuel gauge, nav equipment. sounders through an "accessories" switch powering the other half of the fuse box.
I also put a ground strap onto the "A" frame so you only need to run one wire for the lights and it provides an accessible ground for anything else that you fit at the transom end.
As I say others will have other ideas but this format works for me.
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Old 13 April 2015, 15:45   #18
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I also put a ground strap onto the "A" frame so you only need to run one wire for the lights and it provides an accessible ground for anything else that you fit at the transom end.
I believe you want to be careful about running current through structural metal on boats. Current flow greatly enhances the chances of electrolysis.

Better to put a small terminal block back there for your remote ground point, and keep all the current going through wires.

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Old 13 April 2015, 16:27   #19
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Might be the case if was the +ve side but, if anything, having it connected as an anode should help prevent corrosion, bear in mind your outboard will be sitting at the same potential. Dissimilar metals of fittings or accessories on the "A" frame is more likely to cause rust and "in theory" the frame, being grounded, (frame>battery terminal>outboard case>water) should improve the performance of any radio aerial mounted on it. Now.......lightning ?....... that's a whole other can of worms.
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Old 15 April 2015, 12:05   #20
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Might be the case if was the +ve side but, if anything, having it connected as an anode should help prevent corrosion, bear in mind your outboard will be sitting at the same potential.
Has nothing to do with polarity or potential; has to do with the fact that current is flowing through it.

I understand outboards use this same system that I said to avoid; they, however, take great care to protect from damage from that (take a look at how many sacrificial anodes are on a typical outboard.)


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Dissimilar metals of fittings or accessories on the "A" frame is more likely to cause rust and "in theory" the frame, being grounded, (frame>battery terminal>outboard case>water) should improve the performance of any radio aerial mounted on it.
For the latter, Perhaps. Radio theory was something that was always FM to me (that's F*%&ing Magic, not frequency modulation, BTW.)

My point about electrolytic metal corrosion is not that it would occur; rather that current movement through the metal(s) accelerates it. Using a terminal block prevents current movement through the metal, so no downside there.

You can still daisy-chain the grounds to your devices on the frame and reduce the number of wires through the frame that way.


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Now.......lightning ?....... that's a whole other can of worms.
Personally, I always figured that (lightning strike = I'm dead).

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