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dead batteries


Kismet

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7 minutes ago, Kismet said:

So if I start re charging them is there a smart way to test if they are actually recharging?

 Yes but you will need some 'equipment'.

It is not just a case of measuring the voltage, as leaving batteries flat means that their ability to holds 'amps' (capacity) is damaged, so you will need to do a discharge test.

 

Imagine a 5 litre bucket, it holds water (12 volts) and the amount is 5 litres (5 amps)

Now put 1 litre of mud in the bottom, it still holds water (12 volts) but the amount is now 4 litres (4 amps)

Now add another litre of mud, it still holds water, (12 volts) but the amount is now 3 litres (3 amps)

and so on.

Leaving a battery 'flat' allows the lead sulphate to sink to the bottom like mud.

 

Edit - not a true 'engineers' definition, but hopefully an understandable comparison for a non-engineer.

Edited by Alan de Enfield
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23 minutes ago, David Mack said:

The only alternative would be to borrow a fully charged battery from a fellow boater, put that in place of your start battery, and then with the switch set to whichever of the 1 or 2 positions connects only the start battery you should be able to start the engine. You can then switch to Both, which will recharge both the borrowed start battery and your domestic battery. You will need a few hours running to get a reasonable amount of charge into the domestic battery. If that works you could then stop the engine, remove the borrowed battery, put your charged battery in its place and put your old start battery in the domestic place. Then repeat the process to charge your second battery. You will now have swapped your two batteries, but I don't think that matters as they look to be identical.

When the engine is not running turn the switch to connect only the (new) domestic battery so that you don't run down the start battery.

Recharge with the switch set to Both. You will probably need to repeat this daily, so the sooner you can get the mains sorted, the better!

Just one thing to add, is to never move the 4 way switch through the OFF position while the engine is running as this can damage the alternator.

Jen

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9 minutes ago, Alan de Enfield said:

 

Edit - not a true 'engineers' definition, but hopefully an understandable comparison for a non-engineer.

Edited 5 minutes ago by Alan de Enfield

Really helpful Thankyou! Through this whole battery saga I really want to know about more about my boat electrics so hopefully in the future I am a bit more capable in sorting minor problems myself.. can anyone recommend any books / YouTube vids or anything else to get me a bit more clued up? 

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16 minutes ago, Kismet said:

Really helpful Thankyou! Through this whole battery saga I really want to know about more about my boat electrics so hopefully in the future I am a bit more capable in sorting minor problems myself.. can anyone recommend any books / YouTube vids or anything else to get me a bit more clued up? 

@Tony Brooks has a web site on boat maintenance based on the course he used to run. Has a section on boat electrics. Here.

Jen

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1 hour ago, David Mack said:

You have two batteries with a common negative and separate positive wires, so it looks like one engine start battery and one to run the domestic 12V stuff. This is not a lot of battery capacity to run without either frequent engine running or a permanent mains connection to recharge.

My guess is that the 1-2-both switch has been set to both, so that the mains battery charger keeps both batteries topped up. But the problem is that with the mains having failed, both batteries have supplied the domestic electrics until they ran flat. Which is why you can't start the engine.

Ideally you need to get the mains sorted so you can recharge both batteries. The only alternative would be to borrow a fully charged battery from a fellow boater, put that in place of your start battery, and then with the switch set to whichever of the 1 or 2 positions connects only the start battery you should be able to start the engine. You can then switch to Both, which will recharge both the borrowed start battery and your domestic battery. You will need a few hours running to get a reasonable amount of charge into the domestic battery. If that works you could then stop the engine, remove the borrowed battery, put your charged battery in its place and put your old start battery in the domestic place. Then repeat the process to charge your second battery. You will now have swapped your two batteries, but I don't think that matters as they look to be identical.

When the engine is not running turn the switch to connect only the (new) domestic battery so that you don't run down the start battery.

Recharge with the switch set to Both. You will probably need to repeat this daily, so the sooner you can get the mains sorted, the better!

 

Aim for this ^^^ but ....

Wife - who is an ex-battery person - does not reckon much to your main battery leads.  Find a bit of wire, a knife and a spare 12v bulb (from an out of the way light fitting?).  Sellotape/insulating tape bared ends of two bits of wire to the contacts on the bulb then scratch the top of battery posts to create a silvery patch.   Make sure the mains are in no way connected then touch your Heath-Robinson test bulb across the battery (maybe wait for daylight again ?).  If you get fat sparks/bright light that battery ain't bugg flat.  Glimmer = flatish.  Zilch = flat.  If you do get something try scratching at various places until you get nowt - that's where the problem is.

Alternatively, have you thought of plugging into someone else's bollard.  That's what someone used to do to me 'til I got a lockable plug?.

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When your mains supply is restored switch the charger on, after about half hour switch it of and try some 12v lights, this will tell if the batteries are actually being charged. After that check swirtch the charger on again .Leave the big black switch on both for now.

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28 minutes ago, roland elsdon said:

Or go to screwfix and buy a meter. ( other shops are available but currently full of   probably  infectious people with  children buying useless Xmas crap that screwfix would not indulge)

I doubt Screwfix/B&Q/Toolstaion etc. will list a clamp type multimeter that can measure DC amps so I suspect that now Maplin has gone it has to be an online purchase.  You need a DC amp scale up to 200 amps + to measure the charging current so AC only amp sales is no use to your. A voltmeter reading will with a bit of understanding allow you to infer roughly how discharged the batteries are but to see when they are charged you need a DC ammeter BUT you are unlikely to use it when charging via the charger because long before they are fully charged the charger will have reduced the voltage.

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14 minutes ago, bizzard said:

When your mains supply is restored switch the charger on, after about half hour switch it of and try some 12v lights, this will tell if the batteries are actually being charged. After that check swirtch the charger on again .Leave the big black switch on both for now.

Agreed, but once they are hopefully fully charged change the switch to a position where you can't start the engine but all your lights work. That way if the mains trip out again  you should be able to charge via the engine as long as you put the switch to both (say)  every weekend so the charger charges both for a while. When cruising only put it to both while the engine is running (but don't go through OFF).

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6 minutes ago, Tony Brooks said:

I doubt Screwfix/B&Q/Toolstaion etc. will list a clamp type multimeter that can measure DC amps

https://www.screwfix.com/p/kewtech-kt203-ac-dc-clamp-meter-400a/4048p! 400A DC and AC capacity. Expensive though.

Edited by Jen-in-Wellies
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Just now, J R ALSOP said:

And don't forget to check the electrolyte level in the batteries.

But take great care with any liquid on the caps - its acid and will make holes in any cloths it touches, it can sting a bit on your hands. On no account get any in your eyes.

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4 hours ago, Alan de Enfield said:

 

 

The problem you are going to have is that there is insufficent space there to install any more batteries. If you intend to cruise then you will have problems as you will possibly destroy a single battery in 1 day's usage by making it so flat it cannot recharge.

 

If you are simply going to stay in the marina then there is no problem to keep the batteries as they are and 'live off the battery charger'.

If you are planning to use the boat for cruising you will need to get 'someone in' to sort out where you can out a decent sized 'doemestic battery bank (probably at least 4 batteries). many liveaboards will have 6 or more. 

 

Come back when you have got your leccy reconnected.

 

AFAICT Plenty of space to the left of the batteries for 2 more and maybe 3?

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On 27/11/2020 at 19:14, DHutch said:

Hopefully the OP is not still sitting in the dark!

electric back! all 12v stuff also working.. now just to work out how much life my batteries still have in them... thanks to everyone for comments and help

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29 minutes ago, Kismet said:

electric back! all 12v stuff also working.. now just to work out how much life my batteries still have in them... thanks to everyone for comments and help

Great news, thanks for reporting back.

 

As a very rough totally unscientific guide turn your charger off/disconnect shoreline and see how long it takes for the voltage to drop to say about 12V or a pump stops working or the lights get dim/go out. That will give you a very rough idea about how long the batteries will supply you from fully charged when you are away from a shore line. If it discharges overnight then you need new ones before you stop using the shoreline. Be aware that if you smell rotten eggs near your batteries or if bright metal stats tarnishing you are in danger from the fumes and the batteries have failed big time. Turn the charger off imidiately. if you find just one battery is hot or smelling you can just isolate that one so you still get some electricity pending getting the new ones.

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