start battery installation and wiring.....

[Roger_D]

start battery installation and wiring.....

I have two separately wired 110 amp wet cell batteries in a Sigma 38 and have bought an (expensive!) Odyssey starter battery(a PC1200 model ), which I am planning to wire up.

Having done more research, (and given that I have currently a 1-2-both-off Plastimo battery switch, which I am advised carries a high risk of failure) I am minded to set up the wiring to achieve a state where you can simply turn on the house and start batteries on arrival (via two separate switches), and turn them off when leaving the boat without too much risk of inadvertently losing charge.(having of course charged the batteries at some time in between)

Since I find myself with differing batteries (wet cell and AGM), the charging needs will differ. I plan to charge the start battery from the house batteries (to be one bank) via a serial charger, say the Xantrex Echo, which will start charging the start battery (and limit it to 14.4v) when the input voltage to the house bank exceeds 13 volts when charged by the alternator (it has an adverc controller) or indeed charged by a Sterling mains battery charger.

I would like the starter battery to be providing power only for cranking and have its own isolator switch. The house bank would serve everything else. There would be an emergency parallel switch, or if too difficult to fit, a pair of jump leads handy.

I understand that the output from the alternator would need to go to the house battery.

However, I am not sure whether the house or the start batteries should supply the alternator field and/or the engine control power (pre heaters warning light solenoid etc)
Given my lack of experience, and wanting to avoid expensive experience (the best kind, unfortunately)I would seek advice from the forum, as I may be over my head.
My plan would be to wire the alternator field and engine electrics from the start battery, but then would the house bank have to be on to the take the alternator output?, and if the house bank batteries failed, would you be able to run the engine with no alternator connection?.... Is it only switching off the load without disconnecting the field first a problem?

Is this wise or would it be better to have the engine electrics supplied by the house bank? Aaaargh I think discussion over a beer would be easier....but not possible..I will have to site the house battery switch in the middle of the main panel, (difficult to put it elsewhere) where it could inadvertently be switched off.
(Ps I have discounted the use of blocking diodes/or relay switches given the differing types of batteries)

Any advice please........(sorry for long post, but I tried to give relevant info)

 

[halcyon]

Re: start battery installation and wiring.....

Have you checked what charge voltages the battery manufacture recommends for the batteries, if so what voltages are recommended ?

Brian

 

[Roger_D]

Re: start battery installation and wiring.....

thanks, yes, the odyssey book of words quotes between 14.1 and 14.7, so the xantrex would do, but opinion for AGM batteries suggests 14.4 , I think

 

[pampas]

Re: start battery installation and wiring.....

BAD practice to energise the field from a difference source. May lead to disaster.

 

[Roger_D]

Re: start battery installation and wiring.....

Thanks for that, do you know the mechanism of the disaster? I note some 1-2-both-off switches have a "field disconnect facility" and claim to be able to turn off the battery without damaging the alternator when the engine is running.

 

[FlorealIII]

Re: start battery installation and wiring.....

You can keep the plastimo switch , connect the feed to starter relay directly and service with a switch . Connect the starter battery directly to the starter relay with a heavy switch . Install a second plastimo switch 1 connected to alternator , 2 to 220 volt transformer , 1+2 not in use . Connect feed to starter relay .
Now if you want to start , all switches off except switch from starter battery and second plastimo switch in position 1 . The motor panel takes power directly from starter relay !
The alternator will charge your starter battery . By playing with the switches you can charge whatever battery you like .
If all this looks complicated to you make a scheme and everything will be clear . This is how I solved all my starting and charging problems on my boat .

 

[FlorealIII]

Re: start battery installation and wiring.....

if you want to charge the house battery just turn the starter switch off and the first plastimo switch to position 1 . If you want to charge with transformer and no engine running , put second plastimo switch in position 2 . Then you can charge whatever battery you like with first plastmo switch .

 

[RestlessL]

Re: start battery installation and wiring.....

On the subject of battery switches, look at this. It is a dual circuit battery switch which can parallel the 2 circuits if needed. If I had known this was available last year I would have fitted one instead of 3 separate switches.

John

 

[Roger_D]

Re: start battery installation and wiring.....

Thank you. I was concerned about overcharging the AGM start battery, but note that the Adverc controller instructions say that the max charging voltage is 14.4, which is within the limit quoted by Odyssey, so perhaps I don't need a serial charger charging the start from the house.(except that it would be automatic). I will study your suggestions closely to understand them. Thanks again.

 

[halcyon]

Re: start battery installation and wiring.....

So both batteries overlap in there charge voltage requirement.

What does the alternator currently run at, regulate at ?

If recent it could be 14.2 / 14.4, so fits in with battery requirement.

So all you need are two isolators and a bi-directional relay system, with link start option. Allows simple isolation, automatic charging, engine battery charge if you fit a solar panel on domestic battery, and remote battery linking for engine start.

Brian

 

[Tranona]

Re: start battery installation and wiring.....

Ditch the Off 1 2 switch and install a BEP Marine Battery Switch Cluster with a VSR. This will give you separate switches for each bank and a parallel plus splitting the charge between the two banks. Available from Merlin www.powerstore.com page 7 in their catalogue (among others). They will provide you with instructions for wiring and fittings etc to suit your installation. Very neat, does exactly what you want.

 

[VicS]

Re: start battery installation and wiring.....

[ QUOTE ]
Any advice please........(sorry for long post, but I tried to give relevant info

[/ QUOTE ] You have asked a long and complex question to which there is probably not one correct answer but a number of alternatives to consider. The replies so far indicate that.

I suggest that you get yourself a good book on the subject. "The 12 Volt Bible for Boats " is one which is always recommended and at around £15 is not expensive.

Once you have ordered that and are waiting for it to arrive you could do worse than look at the TB Training "Boat electrical notes" HERE

 

[William_H]

Re: start battery installation and wiring.....

Regarding emergency starting....you mention a pair of jumper leads.
The negatives of all batteries should be connected together. So you might as well do this with heavy starter current wire.
That means you only need one jumper lead. However you can not connect the jumper lead for a start with real safety because you could get a spark at the positive terminal of either battery (the last to be connected) So really the best bet is an emergency start simple contact switch which is remote from both batteries. (the spark can cause battery hydrogen explosion, rare but very dangerous).

Alternators tend to fail when there is power for the field current but no load. The alternator may be machine sensed in that output voltage of the alternator is sensed by the regulator often physically built into the alternator. One would expect that the regulator would sense this voltage and regulate the output even with no battery.
However anecdotal evidence indicates that the alternator diodes can still be killed by excessive voltage. Of course if the sensing is remote and disconnected then the regulator will try to get the output voltage higher but does not sense it has gone higher. In this case it is easier to understand the alternator diode failure.
Hence the wisdom of disconnecting the field supply at he same time as disconnecting the battery.
(bottom line I dunno why alternator diodes die with no load)

it is usual to run all the engine power requirements (gauges heater and alternator field from the start battery. This is probably because the engine is supplied with a suitable switch (incorrectly called ignition switch) and so when you shut down the engine you turn off the engine type power.
Of course the alternator field power and sensing could come from the house battery. You could feed the engine start battery with a diode which would reduce the charge voltage by .7 volt (or a Schotky diode about .2volt) an elegant way to avoid overcharge damage of the engine battery. However that would leave the diode susceptible to trying to carry starter motor current from the house battery to the starter. You would need a VSR to make this connection only when the engine is running and house battery is being charged. A VSR is a relay which only makes contact when the supply voltage reaches over 13volts ie only when battery is being charged.

An elegant but expensive solution might be to connect the engine start battery in the normal way with alternator charging it at its preferred voltage.
You then fit one of these new battery to battery chargers. (Sterling I think) which takes power from a standard charging system at 13.75 to 14 volts and boosts the voltage to 14.4 or so with a smart charger controller so the house batteries are charged in the best way possible.
Have a simple on switch or 1,2,both switch for the house system completely seperate from the engine except for the charger and an emergency start switch.

good luck olewill

 

[Roger_D]

Re: start battery installation and wiring.....

Thanks, I had seen them, but did not realise their function!
looks a possibility & would be less risky in terms of turning off the wrong thing.

 

[Roger_D]

Re: start battery installation and wiring.....

Thanks too for this. I have seen much opposing opinion written about diodes vs VSRs by agents/manufacturers ie voltage drops, heat generation, buzzing (hunting), overcharging etc etc and initially I wanted to avoid them, however I will reconsider.

 

[Roger_D]

Re: start battery installation and wiring.....

I bought Nigel Calder's tome (mechanical & electrical manual) from where I have gleaned much of this. I will look at the "bible".
Thanks

 

[Roger_D]

Re: start battery installation and wiring.....

Much advice from down under! Note your comment re jumper lead(s) & dangers. Thanks too for your note on field wiring & explanations & normal practice for wiring engine power & on Shotkey (low voltage rop) diodes (I expect they are expensive.)

With the house bank being the main supplier to the boat & the starter providing a relatively small amount of energy (provided the engine starts!) I was considering the alternator supplying the house bank, with a battery to battery charger supplying the start from it. (ie the Xantrex..cheaper than the Stirling)

Anyway, now much now to consider and many thanks to you all for your responses. /forums/images/graemlins/smile.gif