Adding a Battery

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WoodyP

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As a lurker over the last few months and a relative newcomer I was hoping that someone would help by asking the question to which I need an answer.

Being a bear of little brain, I thought it should be relatively easy to improve my battery power on the domestic front by adding another battery to take over as the start battery.
The current (sorry) set up is two 85 amp hour on a one two both switch, and I would like to link these together and have a new starter battery for my Beta 28 hp 1005. I presume this would give me 170 amp hours of domestic pleasure, light and warmth. (or about 80 ah in real money).

I just don't know how to link everything up, and what should join on to what.
How do I go about this? Small words please.
best wishes,George
 
Connect the 2 house batteries in parallel, and you will have 12v 170aH. Should be no issue at all. You may want to consider having a maxi fuse terminal junction box so that the cable run to the 1,2,off switch is single cable, and the maxi fuse to protect them.
 
WoodyP
There are two things to consider when adding an extra battery and these are how to separate them so that the starter battery is not normally used for domestic purposes and how to control the charging of the two banks.

I would suggest you have a look here http://www.tb-training.co.uk/MarineE09.html for some guidence.
 
I would suggest you fit a new engine battery system with new battery.
So you need a on off battery switch for the engine battery to the starter and engine electrics. seperate these from the 1,2,both switch.
Then connect a VSR vokltage sensing relay from the engine positive to the domestic system. You can get a VSR with 2 outputs these go to the +ve of each domestic battery via decent fuses say 40 amp.

...or if you get a VSR with only one output connect that to the common battery line of thye 1,2,both switch.

Either way the 1,2, both switch will switch domestic load to 1 o2 or both domestic batteries. In the former case with a 2 output VSR both domestic batteries will be charged any time engine battery is being charged. In the latter case with one output and going via the 1,2,both switch you will only get a charge to any doemestic if the switch is in the appropriate position.

So now when closing down turn off both the engine battery switch and the 1,2,both domestic switch or you can close down engine battery when camping or sailing.

Using this VSR you may get one which will permit emergency starting of engine on domestic batteries, if not make up a jumper lead to go from domestic to engine battery positive or fit another on off sweitch to do the emegency connection. Tape it up so it won't be operated by mistake.
good luck olewill
 
Easy ..... and lets observe the KISS principle ...

Disconnect the start battery from the system ... completely. Lift out battery. The connections will then go to the new battery which you will lift in.
Now find alternative home to old battery lifted out that is alongside old domestic battery .... fit in place. Now you need welders cable or similar heavy duty to connect +ve of this "moved battery" to the +ve of still in place domestic battery ... similarly -ve to -ve ..... so that the two old original batterys are now parrellel and add up to the 12V 170A/hr.

So now you have new battery on start and large capacity on domestic.

I have on purpose stayed away from any major changes such as booster / VSR / Diode systems etc. as I preceive from your question that you just want to change and add .... not get into serious electrical work.

To complete the above all is needed is space for moving battery, coupling both old battery's together and connecting new ...

As alternative to welders cable - which tends to be large diameter and difficult stuff to bend etc. - you could use old battery jump lead cable ... the terminals to batterys - use the clamp on screw together type ... I have used the quick release caravan type successfully as well ... so its not so difficult as some would make out !!!!
 
I did exactly this last winter.

Link up two existing batteries in parallel and leave them on battery 1 on the switch, and put the new battery onto battery two on the rotary switch.

When using the domestic bank there will be much less stress on these as they will not get so discharged.

Take care when linking the two in parallel that they are both good batteies - it takes one cell to reduce the capacity of a battery, but it also only takes one cell to reduce the capacity of now two batteries!
 
I've been watching this string as I am planning to do the same thing. May I ask a supplementary question? The two deep cycle batteries that I am planning to join in parallel for the domestic bank differ slightly in their capacity. I think one is 70 amp/hrs and the other 85 amp/hrs. I know that ideally they should be matching, so that charge doesn't leak to the smaller one, but is it a big deal and worth replacing an otherwise good battery?
 
Re: Adding a Battery ... forgive me answering ...

as long as both batterys are in good condition - makes no issue ..... go for it.

I am thinking of adding to my bank - and only have space for smaller battery .... so what ???? it will go in and be fitted ....... as I see it - it's on;y really like adding more individual 2v cells in a bank as a battery is anyway .....
 
Re: Adding a Battery ... forgive me answering ...

I fitted a Redflash - Micro Engine Start Battery this season - very small = very powerfull. The one I have is about the size of two housebricks and will comfortably start a 50hp diesel. Cost about 80 GBP. Totally sealed and can be mounted at any angle.
I got mine from Merlin have a look at this - Merlin Equipment
 
Re: Adding a Battery ... forgive me answering ...

I had a similar configuration (two start batteries with a 1-2-Both switch).
I replaced one start battery with an 8D house battery.
Later, I replaced the 8D with a bank of four 6-volt golf-cart batteries.
It has given me 10 years of trouble free service.
I have posted a wiring diagram at:
http://carlten.tripod.com/Electrical_system/electrical.html
 
I am in the proccess of adding another battery. SBC your solution seems to be easy so, today I went down to the boat to look at my options. I have 2 x 110ah batteries on a 1/2 and both switch I wanted to determine which was batt no1 and which was no 2. As the engine is out I put a meter accross the +ve and -ve starter motor cables, and disconnected 1 battery. When I turned the switch to position 1 or both, I had full power so, when I turned it to position 2 I was suprised to see I still had a small amount of power. Can anybody tell me if this is normal.
 
Yes everything was off, I can't turn the panel on as the wiring loom is disconnected from the engine. Judging by your reply I assume there should have not been any current there at all.
 
I would suggest that you have a "leak" somewhere .... allowing power across .... you may have a tracked switch ? any dirt or other basically shorting across the contacts inside ?

But really it's a matter of disconnecting as close to switch / loom as possible and then working back from there ... or start at battery end and work up ...
 
Thanks for the replies, by the two accounts I assume there is a problem albeit small, I hope. I will take off the switch and have a look.
 
I have a fairly simply split charging circuit diagram which I've used on my own boat for 3 years now with no problems. I only have an ordinary relay, rather than a voltage sensitive one, but the principle is the same and I don't see why you couldn't use the same circuit with a VSR.

If anyone would like a copy, PM me with an email address.
 
Thank you all for your spot on advice. SBC, you got me in one. William H, I think I know what your saying but it seems a lot of extra faffing about.
Best wishes,
George
 
I wondered when someone would mention Adverc. If he has a 250-300 ampH battery bank (2 domestics plus starter) how is his 35amp Hitachi (or whatever) alternator going to charge it? All three batteries will spend their (short) lives semi-depleted. It's more than just wiring them up you have to worry about.
 
Most charging regimes ...

Do not work at full amp rates ... most of the time they are much reduced rates ...

My standard 40 amp lucas on my Perkins copes admirably with my ~200 a/hr lot. How ? Because if the system is charged while moored - by whatever means .. solar / wind / shore etc. - then engine alt. only has to cope with keeping system topped up.
The only time I could see it as an issue - is if the batterys were depleted all down to serious levels ... but then charge separately via the battery switch ... not all together as one.

I would have no concern to add another battery into my bank and stay with existing system ... it works - despite so many experts who say it's not powerful enough.

I still like the KISS principle .......
 
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