NASA battery monitor

Regards accidentaly selecting 'off' - yes it would blow the alternator - that's why you would be careful not to! On 'both' the charge would generally go to the battery that needs it most beacuse there will be a greater resistance to charge from a fully charged battery.
 
Although reverting to a 1-both-2-off switch will solve your battery charging problems, if you are like the majority of people it does give you other potential problems, and doesn't solve others. When I was using one, I was always forgetting to switch to both when the engine was running, or forgetting to switch to 1 when the engine was stopped. If you don't switch to one battery only when you stop the engine (at anchor for instance) you can end up with flat batteries and no means to start the engine.

If the batteries that you have are wired so that one 120Ah battery is engine start and the other is just domestic, then your new battery monitor should be set to 120 Ah capacity.

If you persist with your standard alternator, the batteries will be effectively and fully charged only when you are plugged into the mains, unless you motor for hours on end. Traditional machine sensed alternators are good at running a cars electrics and putting the 1 or 2 at the most Ah's back into the battery from when the car was started. They are not good at recharging half discharged batteries.

I strongly commend you to think of putting the £30 that you are thinking of spending on a 1-2-both-off switch towards a smart alternator regulator. It doesn't have to be fitted right next to the alternator. Ours is a metre or two away. They are so small, that I can't believe that you haven't room for one. The smart alternator regulator can be wired to sense the battery charging voltage 'at the battery', and so force the alternator to compensate for the split charging diode voltage loss. Furthermore, it will transform the performance of your alternator, and force it to charge the batteries at the fastest rate they will accept charge. We have used one for the last six years on the last two boats, and wouldn't be without one now.

There are various makes: Sterling, Adverc, Merlin etc. Pay your money and take your choice - they all work reasonably well. Be careful if you phone Sterling asking for advice, the man can be a bit caustic, but the products work.
 
So a smart device like Sterling's Alternator-to-battery-charger product would work correctly with a machine sensed alternator?

S.
 
1 - both - 2 is absolutely fine ....

No problem with any of those 3 settings at all .....

Just make sure you don't switch to OFF

I agree with others that a smart regulator is way to go if you are not able to get shore power etc. and need max charge from engine .... but I have also been on 2 boats that have fried batterys with them.

My preference would be to go for a VSR set-up which will not have voltage drop, will allow engine start battery to top up before clicking in domestic etc.

You say that shore power is appearing on your pontoon shortly - well a lot of your worries will then disappear - but then of course the question is shore power supplied charging !!

Contrary to some excellent sound advise on here .... I kept mine simple with the car charger from timed shore power ( 2hrs a day for 5 out of 7 days a week) through a £7 maplins charge splitter to both batterys. Once disconnected the maplins splitter does not have back leakage between batterys ... so it's left in place. I then revert to normal 1-B-2-OFF switch and standard engine alternator. So far no trouble ....

But that is my system - and as I only use my boat for small amounts each year in UK - suits me fine .... if I was to be out each weekend - then I would seriously consider adapting the system ... probably VSR as said.

Have a PM chat with Halcyon - might be a good idea ?
 
Re: 1 - both - 2 is absolutely fine ....

VSR will work as well - but I have seen a couple fried, just like you have seen batteries fried by smart alternator regulators. Perhaps the smart regulators were set up badly, or people forgot to check the electrolyte levels? When batteries are being charged hard, they do lose more water than people are sometimes used to.
 
Re: 1 - both - 2 is absolutely fine ....

Harlequin does have a good 3 circuit charger which trickle charges when batteries are full. I am hoping for shore power, or failing that maybe a temp berth for a week that has shore power to get the batteries back up to full charge.

Looks like I will have to save up and buy a VSR. I nearly bought one, then thought nah... I will try the cheaper option first.

In the meantime, Once on shorepower, I will have to re-wire my battery charger so that it charges both of the engine batteries as well.

The previous owner wired 1 circuit to the gene start battery and 2 circuits to the domestics when they are connected in parallel... /forums/images/graemlins/confused.gif

I will change it so that each starter battery has a circuit and the domestics have a curcuit. I might then do what you do with a small car battery on a timer just to keep the gene battery topped up.

Steve
 
Re: How about this instead

This looks like a good product if it does what it says it does on the tin... at nearly £100 though you are getting halfway to the price of one of the sterling alternator-to-battery-charger units.

I wonder how they both compare...

S.
 
Re: How about this instead

I was considering this for my little yacht because my charging capacity is limited, outboard and solar panels . I had first looked at diodes but realised the volt drop would reduce my batteries capacity and life. I'm also attracted to this type of system due to its simplicity.

Ian
 
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