Battery bafflement...

[Reptile Smile]

Hi all,

Forgive this appallingly newbie-ish question.

I lived for the last 3 years on a hundred year-old lifeboat, and found the electrics a constant source of befuddlement. Having sold this boat, and now moved in with my wife, I'm wanting to buy a trailer sailer.

I have to admit to understanding the electrics even less in this situation. On a 20' trailer sailer, how many batteries are there likely to be? In delivering power to the VHF, lights, depth sounder, etc, what recharges the batteries?

Most seem to have external outboards on brackets, so it seems hard to believe it's from the outboard, but I don't see a lot of other option.

I figure I must be missing something - can anyone help me understand?

Cheers

 

[GrumpyOldGit]

Lots of sailboat o/boards have a 12v charging socket that you can wire into the battery or you could just stick a solar panel on. Either way you should be able to run nav lights and sounder overnight on a charged domestic 80ah without too many worries.

 

[duncan99210]

Welcome to the forum. Never had a trailer sailer but I did have a outboard on a bracket (Honda 4hp) that had a socket so that you could take power off to a battery when the engine was running. Also know some folks who take the battery home with them to recharge it. however, if you're going to be more than one or two nights on board, then you'll either need a take off from the engine or a solar panel or 2. In a few moments, someone who's tackled the problem before will be a long to tell you just how to go about it.

 

[AngusMcDoon]

> On a 20' trailer sailer, how many batteries are there likely to be?

A single battery of about 60-100 Ah would be typical for a boat of that size.

> In delivering power to the VHF, lights, depth sounder, etc, what recharges the batteries?

Reasonable charging from outboards starts with engine power outputs of 8hp. Below that it's usually nothing more than a lighting circuit.

Another option is a solar panel of about 20 Watts output. The fully flexible ones are most convenient on a small boat.

 

[Bav32]

If you're doing a lot of "trailing", might be worth considering fitting the extra battery charge socket ( as used by caravans) and charge up the boat battery from the car alternator whilst on the move.

 

[Frankie-H]

Even trailer sailers stop sometimes. Fit a good quality marine battery charger for use in marinas , on shore supply and when you are parked outside your house.

When you are sailing remember that all the power you use must be replaced by 150%

If you only have 1 battery, which also starts your engine, be very careful not to flatten it.

 

[SAWDOC]

If you only have 1 battery, which also starts your engine, be very careful not to flatten it.

Outboard !

 

[VicS]

Outboard !

I dont actually trail and sail but I have small sailing boat

I have a single 60Ah leisure battery .. the outboard is rope started so no need for a starter battery.

Charging from the outboard is hopelessly inadequate unless its run for many hours at a good speed.

I have a small solar panel. Its only 5watts but it keeps the battery topped up between weekend outings
If I'd had the space I would have fitted a 10 watt one.

If I were to go off for longer than a week I would consider a larger "suitcase" solar panel to supplement the existing one and/or the ability to connect to shorepower and run a battery charger.

I do use an autopilot almost all the time I am sailing. That is probably the biggest drain on the battery.

I am not often out at night so don't need a lot for nav lights. The outboard supplies enough while motoring. For sailing I now have an LED tricolour.

The VHF only takes much current when transmitting ... I dont remember when I last transmitted !

the echosounder does not take much but anyway I only switch it on to use it then switch it off again.

I only use the minimum of cabin lighting ... I am thinking about changing to LED lights ... perhaps.

My anchor light is now a separate battery powered LED lantern ... I used to use a paraffin light.

If you trail home after sailing you can recharge the battery at home. I used to take the battery home several times per season before I fitted the solar panel but it's not now necessary.

 

[William_H]

Small boat power

I have a 21ft trailer sailer. I have a small wet NICad battery around 10AHor less demonstrated on test. It is charged by a small solar panel about 5w. You would need 10w in UK.
If all your lighting is LED you will find (or at least I did) that the VHF drawing 300ma (1/3 amp) on receive is the greatest current drain.
A said most o/b motors are useless at battery charging. Mine gives about 1/3 amp into the battery when running at cruise power.
Ultimately much depends on your usage. Will you sail a lot at night? Will you camp on the boat for long periods?
I have on order 10X NiMh D cells rated at 11AH. I am going to fit these in a plastic box and try them on the boat. Certainly light enough to take home for recharge. NiMh and NiCad are happy to be completely discharged and hold their voltage to the end so you get effectively a lot more AH than a lead acid where you should not discarge past 50%.
Any way for your new boat batteries will be the least of your worries. Trailer towing car rigging unrigging will get your attention. good luck olewill

 

[barnaclephill]

, how many batteries are there likely to be? In delivering power to the VHF, lights, depth sounder, etc, what recharges the batteries?

One battery of about 60 to 80 Amp/hours is normal and adequate.
Some of the next question depends on how long you'll be out each trip, but for normal weekends/one-week-holiday type situations, a 10 to 20 Watt solar panel will do for what instruments you quoted. I'd go for 20 Watts.

The VHF won't be on too much (at least in transmit mode), and lights are usually only 3 or 4 hours of an evening here (but at 50ish degrees north, you have longer days/less nights in the summer). Duration of the depth depends on the coast you're on and experience - mine draws about 3 Watts with the light on or about 1 Watt unlit, and is usually on all the time in an area of dramatic depth changes, but on a gentler, steadier lake situation, then it ain't used much, but it also depends on your familiarity with the area.

The solar panel will have a +ve and -ve wire, usually red & black, and go to the battery simply that way. For 10 Watts you won't need a regulator. For 20, get one next season. Wiring from the battery to the instruments will be simple and there will be books in the library for that, but it's as simple as the solar panel, but add a fuse in one of the lines. LED lamps will help reduce electrical consumption, and have a candle for ambiance or emergency as well. Besides your normal emergency equipment.
In essence, 60 to 80 A/hr battery and 10 to 20 W solar panel as others advised. I've lived onboard in holiday mode for 2 weeks at a time on a 40 Watt panel, but that is with some laptop use, and music on most of the time, etc.

 

[Billjratt]

If you really are trailer -sailing, fit a pair of leads from the light board electrics and charge while you drive - like some caravans.