Batteries!!!! need new ones. Info please

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tonkatoy87uk

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We currently have 2 start batteries (motorcraft calcium plus 95ah/780a linked through the 1, 2 both switch and 1 house battery ( no name 100ah 800a) which has its own isolation switch in the cabin. All 3 are liquid acid batteries. All the lights, pumps etc are all wired up to the 2 start battery bank which are holding up well and have only gone flat once due to something being left on. The house battery on the other hand dies pretty quick when the engine is off. Which has all the nav gear wired to it, which other than the raydar is a very minimal draw, (raymarine a98)
They are installed on a fishing boat which gets the odd nights fish and with winter coming up the lights are going to be on alot etc.

The seperate banks are wired up to a split charge relay and from what I can tell one side is the single house and the other side is the twin start


I'd like all the nav, vhf, nav lights, deck,cabin lights, plugs,etc all to be on the house and start to just be on its own.
Engine is a Mercruiser 4.2d inboard and wont start on one battery.

What batteries would you recommend and how should the isolator switch and split charge be wired? I'm also looking at putting in some solar panels too but have no idea what to get.

The most that we are on the boat is 2 tides.
help would be much appreciated.

thanks Jon
 
You would be correct to get everything off of the engine batteries, except the engine (obviously).

A simple on/off switch for the domestics is also correct. If you could add a second domestic battery that would be better.

Best choice with the engine batteries would be to wire in parallel and connect them to another on/off switch. You could add a 3rd for emergency use if a battery/bank fails or goes flat.

The VSR will have a negative connection and two positives, each positive goes to the positive connection on each bank, or the battery connections on the isolator switches, whichever is more convenient.

There are lots of decent lead acid batteries around, i'm sure you'll get a different recommendation from everyone that replies. I've found these to be reasonably priced and reliable : https://www.batterymegastore.co.uk/hankook-xl31-leisure-battery.html

As for solar, as much as you have space for usually works, but given the use of your boat you might be OK with a 100w panel wired through a controller. Quality solar panels tend to last a very long time, so i would avoid cheap and nasty Ebay panels.
 
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You can get away with a surprisingly small starter battery if you keep everything else off it. It need be no bigger than the battery to start an equivalent engine on shore. Then put the rest of the effort into the domestics to cover everything else.
 
PaulRainbow said:
Best choice with the engine batteries would be to wire in series and connect them to another on/off switch
Click to expand...
In series? gosh, I would never have thought of putting 24v across a 12v starter motor just because the motor was a little sluggish to start. i would be looking at why the engine needed 2 batteries in parallel to start. A "lazy" starter perhaps? or dirty wiring connections (faulty earth connection) or a dodgy solonoid. Never would I dream of putting 2 batteries in series unless it was a 24V system
 
PowerSlapper said:
In series? gosh, I would never have thought of putting 24v across a 12v starter motor just because the motor was a little sluggish to start. i would be looking at why the engine needed 2 batteries in parallel to start. A "lazy" starter perhaps? or dirty wiring connections (faulty earth connection) or a dodgy solonoid. Never would I dream of putting 2 batteries in series unless it was a 24V system
Click to expand...

Fingers faster than brain, i meant parallel of course.

That said, It's a big engine, it'll need some amps to start it. Doubt very much it's a solenoid. Could be the batteries are down a bit though.
 
PaulRainbow said:
Fingers faster than brain, i meant parallel of course.
Click to expand...
I knew that, but I am sure there are some who might try series connecting to see if it improved their starting. i still think trying to find why it takes 2 batteries in parallel to start the engine would be my first course of action. It is after all only a 4.2 Liter lump :)
 
PowerSlapper said:
In series? gosh, I would never have thought of putting 24v across a 12v starter motor just because the motor was a little sluggish to start. i would be looking at why the engine needed 2 batteries in parallel to start. A "lazy" starter perhaps? or dirty wiring connections (faulty earth connection) or a dodgy solonoid. Never would I dream of putting 2 batteries in series unless it was a 24V system
Click to expand...

It's been done though. Early versions of the Watermota Seapanther. 12 volt starter motor. 2 x 12 volt batteries. In series for starting, in parallel for charging.
 
I'd start by looking up the recommended battery size for starting your engine. (Should say in the handbook). Then fit a Volt Sensing Relay to split the charge from your alternator. Wire up as instructions with VSR. Use separate isolators for Start and House battery banks and a crossover.
Solar probably not necessary on a motor boat IMHO.
 
"I would never have thought of putting 24v across a 12v starter motor just because the motor was a little sluggish to start".

I am certainly no expert but everyone I've spoken to (incl. auto sparkies) say there is no problem. My Diesel Fitter B-I-L says they did it for 20 years in their Caterpillar service workshop and it never gave problems.

Instrumentation may be a problem but my Tachometer is 12V or 24V, Rudder angle 12v /24v, Water Temp Gauge 12V/24V and Oil Pressure 12V/24V.

I don't know about Fish Finders, Chart Plotters etc but I imagine they would be available in 12V/24V. Radios are definitely 12V or 24V

Clive

Clive
 
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thanks for the replys. What size and type of house battery would be needed ??

they are wired parrallel but run individually througb the 1 2 both swith. it has to be set on both for it to start
 
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tonkatoy87uk said:
thanks for the replys. What size and type of house battery would be needed ??

they are wired parrallel but run individually througb the 1 2 both swith. it has to be set on both for it to start
Click to expand...

I am certain there would be experts here who could advise but I am about to install x2 AGM 135AH batteries because they are the biggest I can fit. (My fridge/freezer prefers 24V)

Clive
 
Just to be crystal clear about the engine batteries, although the starter motor would work on 24v (we used to regularly jump start stubborn starters (mostly old Fords) by connecting a jump start battery in series to give 24v), i would not recommend doing with the OPs starter batteries because all of the other circuits that are setup for 12v.

Series was a mistake, i meant to say parallel.
 
You mean I shouldn't jump start the guy's BMW over the road with 24V next time he has a flat battery?

Seriously I will be starting my 12V starter motor with 24V and all the instruments will be 24V on my diesel powered boat.

Clive
 
Size of house battery is hard to estimate with the info you've given but I'd start with about 100ahr and fit another if it keeps running out. I find anything bigger à bit awkward to handle.
The pukka way is to do an energy audit of the kit youve got fitted and how long its going to be in use as a first estimate of battery size but remember to consider how it's go in to be charged.
 
Going to be on 90% of the time & when dark etc and engine off

40w deck lights
30w cabin lights (dont need to be on all the time)
25w Nav lights port/starb/anchor
30w Fridge
30w running 8w standby JRC 1000 raydar
15W Raymarine a98
7w Standard horizion gx2200e vhf ?
50w Diesel heater

As and when needed but for longish periods

600w Window heaters (traveling/when engine is on most likely)
200/300w Search lights
50w Front deck lights (for when man upfront lifting anchor)
30w AFI 1000 x3 window wipers (traveling/when engine is on most likely)

SHORT Burst
2x Bilge pumps
1xShower pump
1x deck wash pump


What type of battery would be the best for above ? Ideas on models and type of acid battery ?
 
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Height is not an issue other than fitting into a battery box. We already have 3 full sized battery's, I've probably got room for 1 more if needed.
 
please see edited post above for the list of power consumption


Need to know what types of batterys would suit. It would be a house battery and wouldn't be needed for engine start.

what ah/cold crank values would I need to be looking at ?
 
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Hi try using this spread sheet
https://www.emarineinc.com/pdf/vessel/Vessel_Energy_Usage_Estimator.pdf
convert your wattage to amps and determine how you will meet you energy needs
remember that 50% is the max you should be bringing your batteries down by ,so you will need to compensate this with more batteries
what batteries to use
is up to you ,space and weight all come into play , as well as type I would suggest reading the pros and cons of these before speding your pennies
AGM
LEAD ACID
LITHIUM
in comparison I have 6 110Ah marine leisure batteries for my house and 2 90 ah heavy duty cranking batteries for my starter although my whole system is 24 volts
this runs everything on boat
 
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