Charging - part 2

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mick

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If I carry a Halfords type charger for the odd time when I have access to shore power and use this to charge my (wet) batteries, can I leave the batteries connected, with caps on, while charging? Venting is into the engine space through extended plastic tubing from the wee holes on the side of the batteries.
 
Yes but probably not a good idea to leave it on longer than 48hrs or so unless its an automatic charger.
At least with wet batteries you can replace the water
 
Don't know if the charger you are using is safe on a boat. It's negative side will be connected to lots if boaty bits and needs to be properly (failsafe) isolated from the mains. Be very careful please.
 
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automotive chargers are not fully isolated and shouldn't be used if you want to hang on to your anodes.

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Could you explain 'not fully isolated'. Thanks.
 
We use a Halfords Automatic battery charger on a trailing mains lead and have not experienced any problems. However, we do not have an AC circuit on board.
 
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However, we do not have an AC circuit on board.

[/ QUOTE ] Importantly for the health of your anodes and other underwater bits you do not have the earth of your mains lead connected to them as you would/should with a proper shore power installation, nor presumably leave it plugged in all the time whether in use or not.

Worth checking any portable charger used on board to make certain that the negative side of its output is not in fact earthed, especially if you will be using for extended periods. If it is then that's a possible route from the shore earth via the battery negative to the engine and the anodes and the stern gear.
 
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Worth checking any portable charger used on board to make certain that the negative side of its output is not in fact earthed, especially if you will be using for extended periods.

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Vic, how do I check this?
 
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Worth checking any portable charger used on board to make certain that the negative side of its output is not in fact earthed [ QUOTE ]


Can you explain how, for the desk drivers among us please?
 
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Vic, how do I check this?
Can you explain how, for the desk drivers among us please

[/ QUOTE ] I meant no more than a simple check with an multimeter on an ohms scale. If the two are not connected then there will be an infinite resistance.
With it disconnected just check between the earth pin on the plug and the negative battery clip.
On reflection I'd be surprised if modern charger even had an earth connection, probably double insulated with just a two core mains lead.
 
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Don't know if the charger you are using is safe on a boat. It's negative side will be connected to lots if boaty bits and needs to be properly (failsafe) isolated from the mains. Be very careful please.

[/ QUOTE ]

Would you like to define ...... failsafe ?

Brian
 
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Most automotive chargers have their primary AC and secondary DC transformer windings electrically connected

[/ QUOTE ] I hope not. Potentially, as with an auto transformer, that would lead to a situation where the output was at mains potential relative to earth if the live and neutral inputs reversed. Too dangerous to contemplate as a posibility.
 
If you connect the primary and secondary windings you do not have a transformer.

What you are thinking of is when we take a centre tap of the secondary winding, and link this to 12 dc ground. The two other windings ends being taken via two diodes to produce the positive output. But primary and secondary windings are insulated.

You can replace the diodes with thyristors and a control circuit, to provide a regulated output. Or as we have done on later chargers, two schottky diodes and MOSFETs, produces a much cooler running unit, and does not need fan cooling.

Going back to original question, what is failsafe, sorry I just have an intreset in collecting definitions of marine failsafe systems.

Brian
 
If the maximum delivery voltage of your Halfords transformer is 13.6v or less, then yes, it's possible to leave it connected for long periods.

It's also safe if it's an 'intelligent' or multistage charger, which senses output voltage and switches to lower voltage charging once the battery is 'up'.

However, as other posts point out, earthing may be an issue.
 
Would you like to define ...... failsafe ?
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I expect he is referring to the fact that some elcheepo chargers are single wound where as one would expect double wound in a marine environment...

Beware as some 240/110 volt transformers offered in DIY emproriums are also single would and so not suitable for fitting to boats imported from the USA..
 
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