13.8 Volt Power Supply to Battery

kocha44

kocha44

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Good afternoon on this very windy day,

I am looking into how to charge my batteries using shore power. I have a starter battery (1) and a leisure battery (2), but would like to top up the leisure battery with shore power. I have a 10W solar panel to top up the starter battery which seems to be sufficient in combination with proper engine charging. As for the leisure battery connection to shore power, I was told by someone in the same marina a 13.8 volt power supply would work.

Does anyone have any experience in this area? If so, any clarifications on how this should be connected / done would be much appreciated.

Thank you in advance,

K.
 
13.8V is roughly right to 'float' charge a battery.
It will keep it topped up, but if the battery is much discharged to start with, it will take a long time to charge it, perhaps a week.
IMHO, 13.8V is actually on the high side for permanent, long term 24/7 floating, I prefer either about 13.4V or a regime of float charging only about 1 week in 3.
I have 3 motorbikes and move the charger around every week or so in the winter.
Seems to work for me.

No doubt people will argue the detail.
 
lw395 said:
13.8V is roughly right to 'float' charge a battery.
It will keep it topped up, but if the battery is much discharged to start with, it will take a long time to charge it, perhaps a week.
IMHO, 13.8V is actually on the high side for permanent, long term 24/7 floating, I prefer either about 13.4V or a regime of float charging only about 1 week in 3.
I have 3 motorbikes and move the charger around every week or so in the winter.
Seems to work for me.

No doubt people will argue the detail.
Click to expand...

Thanks for the answer. I am looking more for solutions to connect and charge with shore power when we are actually going from marina to marina, while using appliances, TV, charging computer, phone etc without having to worry. Would a 13.8V be the right solution as discharging will not be an issue if we are on the boat all the time when using this solution?

Thanks.
 
Surely the simplest solution is a purpose built battery charger? The dedicated marine ones are expensive but if you are prepared to connect and disconnect it manually, then you should be able to find something at a reasonable price from Halfords which has a reasonably intelligent charge controller built in and will work to maximise your battery life.
 
You can't just use a 13.8v psu (eg a CB radio psu) - it will be overloaded trying to charge a flat battery and either blow a fuse or overheat as there is often no built in current limiting. (A discharged battery will take as much current as it can draw from a charger so chargers have current limiting capability equal to their stated amperage.)

You need a battery charger, whether you go for an automotive basic one, a more advanced multi stage one, or an overpriced marine one is upto you.

Motorhome chargers are a good alternative usually without the 'marine' price hike. After my expensive Sterling triple output charger blew up (& took my vhf with it) I switched to a 30amp Voltcraft one.

http://www.conrad-electronic.co.uk/...cid-Battery-Charger-Station-For-12V-Batteries

It supports different battery types and can act as a psu to power 12v gear when on shore power.
 
ianj99 said:
You can't just use a 13.8v psu (eg a CB radio psu) - it will be overloaded trying to charge a flat battery and either blow a fuse or overheat as there is often no built in current limiting. ........
Click to expand...

Fair comment.
A lot of supplies are current limited, and the current drawn at 13.8V is often surprisingly low.
The resistance of the wires will knock it down further.
You do want a fuse though!
It's a nuisance if you blow the internal fuse of a supply.

If all you need is float charging during the week, float chargers are cheap.
A 1 amp model will float charge a lot of battery
If you want to power a lot of 12V stuff while alongside, you need a much higher current solution which will cost more.
 
lw395 said:
If you want to power a lot of 12V stuff while alongside, you need a much higher current solution which will cost more.
Click to expand...


He does, he's marina hopping so will need power whilst berthed and to charge the battery for use when on route.

He'll have to work out how much power is required when tied up and add another 20-30% at least of the battery capacity for charging, so could be looking at a substantial charger of at least 30amps. (the ah rating of his leisure battery is stated.)
 
ianj99 said:
He does, he's marina hopping so will need power whilst berthed and to charge the battery for use when on route.

He'll have to work out how much power is required when tied up and add another 20-30% at least of the battery capacity for charging, so could be looking at a substantial charger of at least 30amps. (the ah rating of his leisure battery is stated.)
Click to expand...

Are we talking about something like this http://www.screwfix.com/p/ring-rcbt30-30a-charger-and-jump-12-24v/37237?kpid=37237&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&kpid=37237&cm_mmc=Google-_-Shopping%20-%20Car%20and%20Van-_-Shopping%20-%20Car%20and%20Van&gclid=CjwKEAjw96aqBRDNhM6MtJfE-wYSJADiMfggxaPPxxZV_AExtGvbkpxiAwVRkCkThqDGfBuSW6vKBRoCYSDw_wcB, which is then to be connected to the regulator prior to going to the battery?

Thank you in advance, really appreciate all your input on this.
 
kocha44 said:
Are we talking about something like this http://www.screwfix.com/p/ring-rcbt30-30a-charger-and-jump-12-24v/37237?kpid=37237&cm_mmc=Google-_-Product%20Listing%20Ads-_-Sales%20Tracking-_-sales%20tracking%20url&kpid=37237&cm_mmc=Google-_-Shopping%20-%20Car%20and%20Van-_-Shopping%20-%20Car%20and%20Van&gclid=CjwKEAjw96aqBRDNhM6MtJfE-wYSJADiMfggxaPPxxZV_AExtGvbkpxiAwVRkCkThqDGfBuSW6vKBRoCYSDw_wcB, which is then to be connected to the regulator prior to going to the battery?

Thank you in advance, really appreciate all your input on this.
Click to expand...

That's a powerful charger which you simply need to connect to 240v shore power and then connect the output to your batteries.

However, you might be able to manage with a smaller one, both amps and physical size, which might be slightly cheaper, depending upon your power usage on the boat although the one you have found looks like good value for a 30A charger and will be powerful enough to cover eveything you might use.

Just check that if there is a power outage, the charger will come back on when the mains resumes. Some of the cheaper Halfords ones do not re-start themselves.

Richard
 
That Ring charger (Ring RCBT30 30A ) looks like a traditional 'brute-force' charger to me. It weighs 11Kg and is probably a traditional transformer-and-rectifier design. (No specific details on any of the sites selling it, or Ring's own site).

It may well not have any regulation of the output voltage, which could climb quite high if left on, and might then 'boil' the batteries. Great for pumping lots of power quickly into flat batteries - and occasionally a way of reviving otherwise completely dud ones - but not the best way to treat good batteries in the long term.

(I hope I am wrong and am misjudging the product .... but take care).


Edit: You say in your post: "which is then to be connected to the regulator prior to going to the battery?"

What regulator are you referring to?
 
Last edited:
VicMallows said:
That Ring charger (Ring RCBT30 30A ) looks like a traditional 'brute-force' charger to me. It weighs 11Kg and is probably a traditional transformer-and-rectifier design. (No specific details on any of the sites selling it, or Ring's own site).

It may well not have any regulation of the output voltage, which could climb quite high if left on, and might then 'boil' the batteries. Great for pumping lots of power quickly into flat batteries - and occasionally a way of reviving otherwise completely dud ones - but not the best way to treat good batteries in the long term.
Click to expand...

You've just reminded me of a close shave the owner of a very nice yacht had some years ago. It was shored up in the yard and he'd connected a similar garage type charger to his house batteries and just left it running for weeks. I went aboard to disconnect the mast wiring and was met with two very hot & smelly batteries. Completely ruined them of course. So by all means use this type of charger but do not leave it running unattended.
 
VicMallows said:
That Ring charger (Ring RCBT30 30A ) looks like a traditional 'brute-force' charger to me. It weighs 11Kg and is probably a traditional transformer-and-rectifier design. (No specific details on any of the sites selling it, or Ring's own site).
Click to expand...

Hmmmm ... Vic might well be right. I had assumed that the Ring was an intelligent charger but it does seem very cheap for a 30A charger so I suspect it is not.

Look online for chargers made by Ctek - they are reliable, intelligent and do not shut down on power failure. More expensive than the Ring one but for the above reason.

Richard
 
VicMallows said:
That Ring charger (Ring RCBT30 30A ) looks like a traditional 'brute-force' charger to me. It weighs 11Kg and is probably a traditional transformer-and-rectifier design. (No specific details on any of the sites selling it, or Ring's own site).

It may well not have any regulation of the output voltage, which could climb quite high if left on, and might then 'boil' the batteries. Great for pumping lots of power quickly into flat batteries - and occasionally a way of reviving otherwise completely dud ones - but not the best way to treat good batteries in the long term.

(I hope I am wrong and am misjudging the product .... but take care).


Edit: You say in your post: "which is then to be connected to the regulator prior to going to the battery?"

What regulator are you referring to?
Click to expand...

I am referring to the battery regulator which currently connects the solar panel (10W) to the battery, preventing it from overcharging. The person who mentioned the power supply apparently connected it to this very regulator prior to charging his battery.

I think you made a valid point stating the product I mentioned looks like a brute-force charger. I don't see regulation of output voltage on this model either. Is a manual voltage output type preferable or would something like this http://www.ebay.co.uk/itm/FULLY-AUTOMATIC-5-STAGE-MARINE-BATTERY-CHARGER-12V-30A-/141043954256?_trksid=p2141725.m3641.l6368 be a good option?

Thanks.
 
kocha44 said:
Good afternoon on this very windy day,

I am looking into how to charge my batteries using shore power. I have a starter battery (1) and a leisure battery (2), but would like to top up the leisure battery with shore power. I have a 10W solar panel to top up the starter battery which seems to be sufficient in combination with proper engine charging. As for the leisure battery connection to shore power, I was told by someone in the same marina a 13.8 volt power supply would work.

Does anyone have any experience in this area? If so, any clarifications on how this should be connected / done would be much appreciated.

Thank you in advance,

K.
Click to expand...

You don't say how much capacity you have in your house bank, but if you only have one this suggests that a 30A charger is way overkill as there is no way a single battery can absorb that amount of amps.

If you really want reliable shore power charging then there really is no substitute for a proper multi stage and multi outlet charger either the caravan type already suggested or for a little more money a "marine" charger. For up to 250ah capacity a 20 amp charger is more than enough for the type of usage you are talking about. If you get a multi outlet charger you can charge the engine battery as well, although start batteries if only used for engines rarely need much charge so all your charge when on shorepower will be going into your house bank.

You don't have any high current users in your list such as a fridge or 240v appliances running through an inverter, so probably the easiest way to be independent for overnights is to increase your battery capacity. Do an audit of how much AH you would expect to use between charges from the engine and that will give you an idea of how much capacity you need and whether you actually need a second charge source.
 
kocha44 said:
Good afternoon on this very windy day,

I am looking into how to charge my batteries using shore power. I have a starter battery (1) and a leisure battery (2), but would like to top up the leisure battery with shore power. I have a 10W solar panel to top up the starter battery which seems to be sufficient in combination with proper engine charging. As for the leisure battery connection to shore power, I was told by someone in the same marina a 13.8 volt power supply would work.

Does anyone have any experience in this area? If so, any clarifications on how this should be connected / done would be much appreciated.

Thank you in advance,

K.
Click to expand...

You do not say how many amps your 13.8 volt power supply is rated at. Presumably you have this Power supply on hand. It will work and give you some charge. As said however witha large battery and small power supply you could overload it. A resistor in series will limit the current. Something in the range 1 or 2 amps will possibly help. One amp will drop 1 volt with one ohm so you can see it will limit max current. As current falls the voltage drop will be less. However for normal operation with reasonably charged batteries the power supply will put some charge incurrent reducing as charge improves. But it will also provide current directly for lights etc over night. be very aware however that services you run need to draw less current than the power supply is rated at.
Generally if the power supply is what you ahve then give it a go. An amp meter in the pwer supply would really give you an idea what is happening. If you are considering buying a power supply then a charger might be a better bet. good luck olewill
 
I would second the suggestion to buy a Ctek charger and install it permanently on the boat.
A charger of this type is perfect for your application.

If connected for long periods to a marina power supply you might need to keep an eye on your anodes or consider fitting a Galvanic Isolator.
 
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