Batteries

[dawniewilson]

at the risk of sounding like a lubber...I have a question. With a house and start battery, do I need to switch off the start battery after starting the engine? When underway should I just have the house battery on? If both are switched to on the whole time is that a bad thing? I have searched the owners manual in vain. Hope to get a charge out of this post...

 

[cymeyer]

Hey Dawniewilson,
I will give you my opinion and let others correct me.
I always put both batteries on when starting. After the engine is off (hate motoring), I turn off one battery. That way, i feel I always have one charged battery for starting the engine.
Would like to hear other opinions.

 

[woodster]

there is tons and i mean tons of information on musings with maine sail on this subject ...be prepared to do a lot of reading and learning .......

 

[RickSegal]

I generally have both batteries on when starting boat (like cymeyer) and do not turn any off. Given the ability to monitor them and my easy power requirements, I don't believe I'd be getting a material power advantage but certainly understand peace of mind with one off just in case.
Fair winds!

 

[JohnVTX]

Both on when starting and charging. Under sail I switch to one.

 

[Ron20324]

+1 to John. I have three batteries, each with it's own on/off switch. I usually leave one off, so if one of the other two melts down and takes the third with it, I still have the one left for starting. After sailing and then motoring looking for an anchorage, I have all three on for a final charging and to use when running the windlass. Engine off, one battery goes off. I rotate the "off" battery usage.

 

[Davidasailor26]

there is tons and i mean tons of information on musings with maine sail on this subject ...be prepared to do a lot of reading and learning .......

Exactly. The answer will depend on exactly what your battery configuration is, and Maine's info should help you sort it based on that. One rule that would apply in general is that you absolutely do not want to disconnect a battery while the engine is running if that battery is the only sink for the alternator's current.

 

[seadaddler]

The problem with starting with everything on is you won't really know if
your backup start battery is in good shape and if lets say you are anchored out for a few days and some thing happens to the house batteries and the you go to use the start battery and it is dead or too weak to start?????.
My start battery is for start the Gen and Yanmar only with a cross over switch in case I need the house for starting and my solar charger charges the start battery and house bank.
Nick

 

[Gunni]

I leave my Beneteau engine battery in the off position ALL the time. It is simply an emergency start. All normal starts are from the house battery. The engine (and house) battery is connected to the charging system even when in the off position. Study the wiring diagram in your boat manual to confirm your configuration.

If you have one, the negative disconnect must be left in the on position anytime you have either house battery (positive) in use.

 

[Benny17441]

1) First determine what types of batteries you do have. Starter battery can sometimes be defined by type or by function. A true starter battery type has thinner plates, and it is designed to produce high but short bursts of power. These type are not adequate for deep discharge. Their size is usually rated in CCA (cold cranking amps) and are usually labeled as staring battery. On the other hand the house batteries are usually deep discharge type. These are designed to accept multiple cycles of charge/discharge. Their size is usually rated in Amps and labeled as deep discharge. (there is a third type marketed as a dual function, an in between hybrid). The thing is that in some boats the owner could have installed a deep cycle battery to perform starting functions.
2) Do not combine a starter battery with a deep cycle except in an emergency for a short period of time. Nothing drastic would happen but it is not good for the system or either battery. If both house and starting are deep cycle types then you can combine them.( preffered combination in a basic two battery system)
3) You do not have to switch the starting battery off after starting the engine; give it some time to recharge after that initial burst of energy.
4) If you have a two battery switch with 1,2,Both,Off just remember that only the designated battery will power the loads and only the designated battery will receive charge from the engine alternator. If you wanted both batteries to receive charge from the alternator you could use the Both selection if the batteries are of the same type. Think of electricity as water that will flow from a high point to a lower one. If you combine a fully charged battery with a depleted one the power will flow from the stronger to the weaker until equilibrium is reached. Consider that this may leave you with two inadequately charged batteries instead of having one fully charged.
5) Many, in a two deep cycle battery system, just use one battery to keep the second in reserve. They alternate the use with each outing to keep both exercised
6) If you have a true starting battery and a deep cycle then you can start the engine with the starting battery, let it recharge for a few minutes and then switch to the house battery. If you want to simplify things you could also just leave the starter battery in reserve and start your engine with the house battery and continue with it. Deep cycle batteries can easily start these small auxiliary diesel engines.
7) One tip. We usually carry an automotive type battery pack for emergency starting power in case we accidentally ran the batteries down.

 

[Roland5048]

I have four 6v. golf cart batteries for the house, (#1 on the sel. switch) and one 12v. Group 24 for starting, (#2 on the switch). I always start on 2 then switch to Both for the 45 min. motor down the river. Switch over to 1 when sailing or when the motor is shut down. Repeat the process when motoring back up the river. I've always believed that it is not good to start the motor using the deep cycle batteries but that may now be 'old school' thinking after reading Benny's post.

 

[Benny17441]

I've always believed that it is not good to start the motor using the deep cycle batteries but that may now be 'old school' thinking.

Marine deep cycle batteries are not designed to produce a strong surge of power but in practice they have been proven to be very capable of starting the small auxiliary diesels without seemingly any negative lasting effects. In small 2 battery banks many are willing to compromise any small negative effects for the ability of having a second compatible battery that they could combine or isolate depending on the circumstances. Some have relegated a true starting battery to just a back up status to be used in an emergency and just operate from their house bank. These are not really true "deep cycle" batteries as the real ones would not perform well in a boat because of movement as they like to sit still. You can think of the marine ones we use as a higher grade of a dual purpose batteries which also include the ability to crank a starter without significant damage. So you are combining the battery banks for two 45 minute stints on every outing. Going out you will have a fully charged house bank but coming back you may likely have a partially discharged house bank. When combining two battery banks you are basically creating a larger single battery bank and it is the combined voltage that will drive the regulator to the alternator. Instead of combining the banks for 45 minutes I would recharge the starting battery for 10-15 minutes and then switch to the house bank. You have two banks of very different size with a voltage differential and the voltage regulator will respond to the needs of the larger bank irrespective of the state of charge of the smaller one. Perhaps your power usage is light and whichever way it is done is inconsequential but I would rather keep the starting battery isolated with adequate charge than throw it in the pot with hungry cannibals.

 

[Jongleur]

I am shocked, I say, shocked, that nobody
has brought up this:

http://www.go2marine.com/product/24...-si-series-automatic-charging-relay-7610.html

You can leave your switch on house all
the time, knowing that you are keeping
a reserve battery charged and isolated,
so that if/when you fully discharge or
ruin your house battery, you can switch
over to the reserve battery to start your
engine and get home (and fix the problem).

Works a treat.

 

[seadaddler]

I was wondering also why no one was talking about the ACR or even a echo charger,
I really did not like keeping track of who's on first and who's on second and think
the best way to not make a mistake is with the ACR or echo type and never have to change anything.
Nick

 

[Benny17441]

I am shocked, I say, shocked, that nobody
has brought up this.

It is a relay switch that costs $85, that is why.

 

[Gunni]

The OP's Beneteau DC charging system is designed to charge both House and Starter batteries regardless of disconnect position. Doesn't need that relay device.

 

[Maine Sail]

The OP's Beneteau DC charging system is designed to charge both House and Starter batteries regardless of disconnect position. Doesn't need that relay device.

This is not the typical Beneteau wiring I regularly see. The load side of the two red switches (engine starter and DC panel side of switches) are bussed together and the alternaotr feeds this side of the switch. The battery side of the switches go to the two separate banks. If both switches are on, both banks charge. If one switch is off only one bank charges.

The biggest issue I see with Benetea/Jenneau battery switch wiring is folks killing both banks because they don't realize that when both switches are turned to the ON position the banks are in parallel and you can kill both banks. Most owners incorrectly assume the engine/switch/battery bank is isolated from the DC panel/battery bank but not if both switches are left in the ON position.

For some Beneteau or Jenneau boats I will install an ACR or Echo Charger and just instruct the owners to use the house bank for everything leaving the start switch OFF (so they don't forget and leave it on). On a number of boats boats I have re purposed the negative switch (not supposed to be there by safety standards anyway) and turned it into an emergency parallel switch. This removes the parallel jumper between HOUSE and ENGINE switches and gives true isolated starting and house loads all for the cost of a DC neg busbar abd about 16" of wire... Most then choose to install an ACR or Echo to automate charging both banks behind the scenes.

 

[Gunni]

Yep, both House and Engine batts charge on either alternator or shore charger irregardless of battery switch position. Only the house has temp regulated shore charge. When you kill your House battery, turn off the House switch, and turn on your Engine battery. Go-juice! Could not be simpler.

 

[Jongleur]

Maine Sail:

Thanks for chiming in.
The ACR system is awesome. I'm sure it
can save a lot of people a lot of heartache.