Fitting a second battery

[avebury]

All,

I'm sailing on a budget and would like to fit a second battery but cannot afford to get a yard to do the work for me. Has anyone done this themselves? (I'm sure you have) and equipment do I need to complete the job? Charging will be from an alternator. I would also like to fit a shore power connector and charge the batteries that way

Thanks all

 

[Tranona]

Quite straightforward. Assume you want to keep one battery for engine start and one for services with the option of linking both in an emergency. One way of doing this is to use a a battery switch cluster such as that made by BEP wehich also has a VSR to split the charge between the two batteries Merlin www.power-store.com can provide the information and make up a kit for you to install. For Shorepower you have a range from using a caravan type extension with a built in RCD from somebody like Towsure or installing a full shorepower circuit and a built in battery charger. Again Merlin or others such as Barden or Sterling can provide information.

 

[asj1]

Quite easy. Treat as two projects.
Most difficult part is finding somewhere to put the 2nd battery aand making up a box/platform to hold it.

Once you have done that then,

1) Connect negative on new battery to negative on old battery
2) Buy a battery splitter/ splitting diode.
3) discconnect the existing cable from the alternator to the existing battery and connect it to single terminal on (2) above
4) Connect the +ve terminal of each battery sepertaely to the 2nd and 3rd terinals on (2) above.

You now have two batteries with the charging split between them.

5) Now select a suitable master battery battery switch for the new battery. I would use an on/off one from BEP. Connect the positive of the new battery to this switch
6) disconnect the cable that currently goes from your switch panel to the old battery and re-connect it to the other side of the switch in (5)

You now have a two battery system and the two batteries are entirely seperate. The old one starts teh engine and teh new one does teh domestics The new one will charge as soon as you have the alternator on as the alternator is connected staright to the battery (vial the split charge diode) Some purists may not like this - but it works.

The job is almost done ! all that remains is to make a facility to join th batteries up for emergency starting. The simplest solution is to carry a jump lead and if the need ever arises you use the lead to connect the two +ve terminal together. you only need one lead the -ve is already connected up in step 1.

Oh put the new battery in a plastic battery box avaialble from most chandlers and quite cheap.

This is a simple wiring solution, there are more complex ways of doing it. The adverc website has wiring diagrams you can download.

Regards

 

[vyv_cox]

<<<< Oh put the new battery in a plastic battery box avaialble from most chandlers and quite cheap. >>>>

Before buying a battery box, better read this thread Bear venting of possible hydrogen and oxygen gases in mind.

 

[Tranona]

Andrew's system will work OK, but a battery cluster will provide all 3 functions, on/off for each battery, both parallel and split charging. If you use a bus bar for thes service battery you can also arrange an always on supply for items such as an automatic bilge pump, or the memory for a normal car type radio. If space is a problem, consider using a micro engine start battery such as Red Flash or Odyssey which are small, sealed and can be mounted in any orientation. You may be able to fit one of these and a decent size service battery in your existing space.

 

[reeac]

[ QUOTE ]
All,

I'm sailing on a budget and would like to fit a second battery but cannot afford to get a yard to do the work for me. Has anyone done this themselves? (I'm sure you have) and equipment do I need to complete the job? Charging will be from an alternator. I would also like to fit a shore power connector and charge the batteries that way

Thanks all

[/ QUOTE ]

You might want to consider adding a second leisure battery as opposed to a dedicated engine starter battery. That way you'll double your available amp.hours for services use. Of course you'll have to make sure that you keep enough in reserve to start the engine but presumably you've been doing this all along with your present single battery so you'll be used to this. I've been using the two service battery/no starter battery system for years with no problem although I must admit that I've just purchased a £30 jump-start cum inflatable pump power pack partly as an insurance against future battery problems.

 

[BAtoo]

Regarding the "budget" side of your question look at your local caravan shop where things will probably be cheaper. Lesure batteries from there generally cheaper & all you need. A quick google found a voltage sensitive relay for £25 ish from one caravan shop & even less on Maplin 40A one for a few ££. Battery chargers also from your caravan shop or motor spares - "inteligent chargers £50ish - or a cheaper one on a timer...
I did our 240V system using a "Garage Unit" from local electrical supplier - £20ish (IIRR) for a sealed box with ELCB & 2 trip fuses.

The "marine" tag coasts alot....

 

[maxi77]

I certainly have used the 2 service battery solution on my last two boats wth no probles, especially as I had alternator problems on one and had no problems provided care was used. Caravan shops are definitely better for batteries, and gas things too. A tip I picked up from my local caravan shop on gas bottles was if you need a new one go to your local tip and ask them for a discarded one, be prepared to pay a fiver but it is a hell of a lot cheaper than paying for a new one up front.