can I just attach my battery charger to the 12 volt socket and charge from there
- Thread starter dylanwinter
- Start date
VicS
Well-Known Member
There are two considerations.
First and foremost the safe current carrying capacity.
Secondly for 12volt circuits the voltage drop caused by the resistance of the wire itself becomes of concern for cables longer than about 1 metre. The longer the cable the higher the resistance and the greater the volts drop
ostell
Well-Known Member
I'm working on how to connect the charger to the batteries directly without having to go through the main switch and not disturbing the locker lids etc.
I was thinking along the lines of a polarised plug/socket arrangement. Was originally considering using the DIN mains plugs that computers use as they come in a variation of types but I may end up in something like a 15A round pin mains socket, one for each battery. I can then also plug in the solar panels when I leave the boat. WIP
I was thinking along the lines of a polarised plug/socket arrangement. Was originally considering using the DIN mains plugs that computers use as they come in a variation of types but I may end up in something like a 15A round pin mains socket, one for each battery. I can then also plug in the solar panels when I leave the boat. WIP
JumbleDuck
Well-Known Member
I'd strongly advise not using anything which is used anywhere, or which has been used anywhere, for AC mains. Sod's Law is remorseless.
johnalison
Well-Known Member
Our boat came without its battery charger, which was pre-arranged so that the agents at home would fit one. In the meantime, we charged the batteries with a small charger via a cigarette-lighter socket. I was reassured by having a PhD in electronics on board. We did occasionally clip to the batteries but that was very awkward.
One problem is that you end up with an exposed live terminal from the charger. Providing one is careful this shouldn't cause difficulties. I would never consider it for a permanent installation though.
One problem is that you end up with an exposed live terminal from the charger. Providing one is careful this shouldn't cause difficulties. I would never consider it for a permanent installation though.
Of course you can, but is it wise not knowing whether the socket can carry the charging voltages.
Wouldn't it be wiser to run a pair of cables with at least a 50% safety margin of the maximum current your charger is likely to produce to a convenient position, to which you can connect your charger.
You only have to do the work once, whats the problem?
Iliade
Well-Known Member
Cigar lighter sockets are unreliable tat which will eject a plug just far enough to break contact at the slightest opportunity. Also the wirng to the plug must be considered useless until you have checked it.
Furthermore, the crocodile clips supplied with most chargers get rather crotchety after any length of time on a boat. I'd suggest looking here: http://www.maplin.co.uk/c/cables-and-connectors for something more to your liking and then run a dedicated cable to connect to it when it arrives.
Furthermore, the crocodile clips supplied with most chargers get rather crotchety after any length of time on a boat. I'd suggest looking here: http://www.maplin.co.uk/c/cables-and-connectors for something more to your liking and then run a dedicated cable to connect to it when it arrives.
blackbeard
Well-Known Member
Indeed so. Though they do vary a lot (from bad to worse, some might say).
Back to OP - I regularly do this, have not had a problem although I would not leave a charger unattended. My charger gives a max of 8 A and socket is fused 10 or 15 A. It seems that quite a lot of kit intended to run off these sockets take current of this order. The wiring of mine is, I think, adequate for the job. Wouldn't know about anyone else's.
nimbusgb
Well-Known Member
As VicS has mentioned, voltage drop between the socket and the batteries will pretty much ensure that you never get a full charge on the batteries. If your charger is seeing 13.8v at the socket chances are that the battery is getting 13v or so. ( test with a good multimeter at the charger and at the battery terminals )
ostell
Well-Known Member
I don't think the old 15A mains plugs would be a problem. Both the chargers I have are short circuit/no circuit protected. Plugging a mains powered device into 12V shouldn't be a problem. I'm still looking for a suitable alternative though.
William_H
Well-Known Member
Not actually so. The current that goes into a battery is very much dependant on voltage (at the terminals of the battery) Now if you are puting 10amps into a battery and suddenly introduce say 1 ohm of ressitance into the wiring then ohms law suggests the voltage will drop by 1 volt. However that 1 volt drop will make a huge difference to the current accepting ability of the battery in a non linear manner so that current will drop so reducing volt drop. In effect the resistance of the leads will limit current into the battery so increasing the time to fully charge the battery but it will fully charge eventually.
Old style battery chargers had a range of resistance that can be selected to limit max current. Later really cheap chargers relied on built in resistance in the transformer to limit current.
Consider that a 10w solar panel has effectively a resistance of 40 ohms within itself. Which is the same as a low resistance current source in series with 40 ohms. Yet this can still fully charge a battery given enough time and sun. Vastly more resistance than any wiring from a mains charger to the battery via the ciger lighter type socket.
So yes low resistance wiring is good but it doesn't matter as much as you might imagine. ie nothing like the problems of resistance in a mast top incandescant lamp where resistance directly reduces the lamp voltage and power. good luck olewill
aquaplane
Well-Known Member
If you are fitting a bulkhead socket and proper cabling to connect the lead to the boat, why not fit a socket in the locker with the batteries and leave the charger in there plugged in permanently? I would have a Garage Consumer unit between the inlet and the sockets, the lower breaker for the charger and the higher breaker for the sockets.
Run a different flex to another socket for all the other stuff, or even a socket up forward and one aft.
Run a different flex to another socket for all the other stuff, or even a socket up forward and one aft.
JumbleDuck
Well-Known Member
Still very widely used in theatre lighting setups. Murphy rubs his hands together, grinning nastily.
Thistle
Well-Known Member
I have a small portable solar panel which is pretty much permanently connected like this to a dedicated cigar lighter socket. Keeps the battery nicely topped up. I do much the same in a caravan with the same result. In both cases the wiring to the socket is at least as heavy as the wiring from the panel.
ghostlymoron
Well-Known Member
One disadvantage is that it will only charge the house battery. You may want the engine battery charged as well and be better served by a charger having 2 outputs so that you can charge both.
