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Shore power seems to be draining my starter battery.


purple8

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Nearly two years ago, with the boat sat on a slipway in a boatyard for a few days, we used shore power on the boat only to find out that once put back in the water the engine battery was too low to start her up.

We got it going and forgot about the whole thing.

 

Now we live on a mooring and we have shore power. Each time I go to start the engine the starter battery is again too low to do it and needs charging with a battery charger.

 

Now I know I could get an expensive new bit of kit that would charge the batteries all from the shore power, but I was wondering if anyone could just explain to me why this is happening. Never a problem when we were continuous cruisers, but now an issue.

Thanks in advance for any help

?

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Maybe your starter battery is knackered and is self discharging.

When you are using the engine to charge your leisure batteries then the starter battery is also charged.

When you are on a land-line then you are not starting the engine, not charging the starter battery and as it is a bit 'poorly' it id flattening itself (quite normal)

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6 minutes ago, Alan de Enfield said:

When you are on a land-line then you are not starting the engine, not charging the starter battery and as it is a bit 'poorly' it id flattening itself (quite normal)

 

^^^^This is it^^^^

 

When you never run the engine, the starter battery never gets charged. So it is probably totally goosed (technical term) from chronic under-charging.

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a usual set up these days on shore power is as mine that charging goes to both the domestic and starter batteries. You seem not to have that but it could be done quite cheaply.

1 minute ago, purple8 said:

First time it happened is was sat for only two days. Now it's more like two weeks.

Worried about replacing with a new battery and somehow draining it when plugged in?!?!

 

Have you any monitoring equipment to see if you have a drain anywhere?

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9 minutes ago, purple8 said:

First time it happened is was sat for only two days. Now it's more like two weeks.

 

 

Oh I see.

 

9 minutes ago, purple8 said:

Worried about replacing with a new battery and somehow draining it when plugged in?!?!

 

Well at the risk of seeming unsympathetic, you have two options. 

 

1) Buy a new battery, blind, and hope

or 

2) Get some sort of monitoring or measuring device and find out if something is draining it. 

 

I don't think anyone can tell you on a discussion board why it is doing it with any certainty. Only point out all the possibilities. Your best bet is to find someone with, or buy for yourself, a DC clamp meter. They cost about £35 and are an excellent investment.  Clamp it round the starter battery negative cable and it will tell you if there is any significant current draining from it.  

 

My gut feeling is the starter battery is just very old and expired. How old is it?

 

 

 

Edited by Mike the Boilerman
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Colder weather won't help either. Most car starter batteries get replaced at this time of year because the car won't start, been OK in summer but unknown to the owner 'only just OK'. Now oil is colder it needs more amps to crank the engine, colder engine takes longer churning over or heaters on for longer, all are harder on the battery.

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13 minutes ago, ditchcrawler said:

Disconnect the starter batter completely  ie. take the battery cable off the battery post and see if it still fails to start the engine after 2 weeks

This is the sensible idea and also the cheapest. If it fails to start after two weeks not connected to anything its broken with a capital F and you need a new battery.

Then fit a VSR cost about £30 and that will connect the batteries together (provided you fit it the wrong way round ;) ) and allow one charger to do all batteries

 

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As above, but adding use of eyeball mk. 1. Is there anything, apart from the starter motor and engine panel, connected to the battery? Any automatic bilge pumps, clocks (although I wouldn't expect one of them to make much difference) etc.?

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Ok great idea. I will disconnect it and see what happens in a few weeks or less. Only a bilge pump running off it extra to the starter, and that's hardly ever in action (luckily). 

And yes the battery is old. It's been on since we got the boat so 2yrs +. But could be 20yrs ?

Prob a new battery job tbh

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Over the winter I connect the shore power to keep the batteries charged up, it was only this spring I was told this does not include starter battery.  The starter battery went flat after 6 years.

 

I have been told that to keep the starter battery charged over the winter to connect it to the leisure batteries using an appropriate thickness of wire but Loddon has suggested using a VSR.

 

My question is, can I connect the starter battery to the leisure batteries over winter or to do this do I need a VSR? Or do I do nothing and replace the starter battery every 6 years?

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1 minute ago, GinJer said:

My question is, can I connect the starter battery to the leisure batteries over winter

Yes.

Just use standard 'car' Jump-Leads.

If both batteries use the same 'negative' then you only need a single (red) Jump-Lead to connect across both of the positives (starter battery and leisure battery bank)

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1 minute ago, GinJer said:

Thank you, that's exactly what I wanted to hear, but what is a VSR?

As I understand it a VSR or Voltage Sensitive Relay will bring into circuit a second battery bank when the voltage in the first bank has reached a set value. This allows you to charge the leisure batteries that have gone down with overnight use before topping up the starter battery which will not have dropped much.

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1 minute ago, GinJer said:

Thank you, that's exactly what I wanted to hear, but what is a VSR?

A Voltage Sensitive Relay.

Is connected between your alternator and your batteries.

 

Used for charging 2 separate battery banks.

It charges one, then once it gets to a pre-set voltage it 'opens up' and starts to charge the other battery as well.

 

Some folks will have it so that it charges the starter battery 1st, on the basis that if you have a fully charged starter battery you can always start your engine.

Others prefer to have it charging their leisure battery bank 1st and then switching over to the starter battery.

 

It can be wired up either way.

 

 

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17 minutes ago, Alan de Enfield said:

A Voltage Sensitive Relay.

Is connected between your alternator and your batteries.

Just to correct a VSR is connected between two battery banks and not the alternator.   The alternator is connected to one of the banks.   The advantage of a VSR over a split charge relay (which only connects the banks if the alternator is running), is that a VSR will connect when anything is charging either bank, so Solar, Battery charger, alternator, hamsters, etc. can charge both banks.

Edited by Robbo
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