Boat Batteries Question

[Jean]

Consider a sailing vessel with 2 batteries, number 1 normal high current lead acid and the number 2 a low current leisure battery (both around 100 AH rated).
Vessel has a 3 position selector switch for number 1. number 2 or both. What switch position would you use to start the diesel engine and why?

 

[Guest]

I use the battery with the most charge in it for starting but then, both my batteries are the same.

 

[Guest]

It is possible that your 'high current' battery is a traction type and your 'low current' battery is a cyclic type.

Traction batteries (as in your car) provide very high current (hundreds of amps) for a short time - starting. The charge lost is then replaced by the alternator while the engine is running. Charging is therefore automatic and the state of charge is held at a fairly constant level.

Cyclic batteries, on the other hand, are designed to provide relatively low currents (say tens of amps) while supplying domestics, but conscious measures have to be taken to recharge.

The internal structures of the two types are different to provide optimim efficiency for their designed use, but a cyclic (low current?) battery of 100AH is quite capable of providing enough current to start a small yacht engine.

Which battery to connect to which switch position is a matter of personal choice. Mine is 1 for starting and 2 for domestics

 

[billmacfarlane]

It looks like you've got one specialised battery for the engine and one for domestic. The high current battery is specifically designed for giving out high currents for a short period of time e.g. to supply the high current needed for your starter motor to turn over I assume a diesel engine. The other battery sounds as if it's designed for giving out current to domestic appliances e.g. lights , instruments etc. I'd start the engine using the high current battery , then switch to the both position when the engine is running. When the engine is off use only the domestic battery. Assuming you've no blocking diodes , beware that if you've got one battery low , when you are in the "both" position , the batteries will equalise.

 

[VMALLOWS]

Re: post by achillesheel.

Your terminology is incorrect; a TRACTION battery is not the sort in your car.....that is an "Engine cranking battery".

A Traction battery is for repeated very deep discharges (after traction as in milk-float etc). It is ideal for 'domestic' use on boat but rather expensive (and heavy).

A leisure battery is somewhat inbetween, though I would put it more towards the
'car battery' side of the scale.

 

[ccscott49]

There is only one answer, use the engine start battery for starting the engine, then switch to both for charging. When you shut down the engine, switch to your domestic battery for the lights, etc. If you use the domestic for engine starting, you will greatly reduce its life, or even ruin it in a very short time. If you use the engine start battery for domestics, you will ruin it aswell. In an EMERGENCY you can use both batteries or the domestic to start the engine. If you do not have one, a charge splitter is a wonderful bit of kit, as is an alternator booster, "smart charger" system, especially as you have two different battery types. I do hope I've made sense, if you need clarification, you can contact me direct.

 

[Guest]

Having tried to use a Leisure battery to start a car one time - I would never do it again .... it ruined it ! I was stuck with a flat battery and it was only available battery at time.

I checked with a friend who deals in batteries and he confirmed that Leisure batterys are definitely up to starting anything except the easiest and shall we say 'warm engines'. If it has to crank for more than a few seconds .... bang goes the internals which cannot suffer such high current draws. They are designed for deep cycle domestic use only.
Now the high current job will suffer domestic use as long as it is charged regularly and well and never allowed to deep discharge.

So now I use two HD Car batteries and stopped using any leisure battery's --- giving me a choice of which to start the diesel and also allowing me to cycle my domestic also. I regularly charge, not allowing them to fall into deep discharge.

 

[ccscott49]

Isnt that what I said?

 

[kingfisher]

Never charge on \'both\'

1= engine battery
2= household
Both: only when each battery alone is to low to start the engine, or to switch from one battery to another.

Never charge with selector on both:
1) you will bleed one battery in the other
2) different batteries have different charge cycles. So you'll end up with one battery that is being overcharged, and another which isn't being charged enough

Example: engine batt is at 80 %, household batt is at 60 %. Your charger/generator/alternator will think they're both at 70 %. Say goodbye to the engine battery: it will cook itself to death.

In theory, you can use 'both' when you have to identical batteries, depleted to an identical level. But even then, the engine battery will run a different llife cycle than the household battery, so after a few months that won't apply.

Obi-Wan

 

[bryantee]

Re: Never charge on \'both\'

I now use semi traction batteries,developed for use on lorries which have both high starting loads,and domestic loads.tailgate loaders.kettles .lights etc.They are cheaper than full traction.and seem to be a middle of the road way out.comments please.See advercs site on Exide batteries

 

[charles_reed]

Re: Never charge on \'both\'

Never is one hell of a long time - I'm always suspicious of comments containing such absolutes. >.

If you have a splitting diode on the charging circuit, there is no reason why you shouldn't charge on both.

In fact many experienced liveboards successfully do exactly the opposite to the perceived wisdom and get 8-10 years out of their batteries.

Mixing different types of batteries (lead/calcium with lead acid) is perhaps unwise, but the biggest drawback of any system using the standard in-alternator regulator is that the batteries will never (there I've said it) achieve full charge.

I've three batteries one bog-standard lead acid (always on), one deep cycle lead acid and a lead-calcium battery.
On long sails (over 12 hours) or at anchor I use, alternately, one of the two batteries reserving the other for starting.

The last standard always-on battery did 11 years and was only ditched because one cell wouldn't accept full charge on conditioning.
The deep-cycle battery is relatively new at 5 years old and now holds 108% of rated charge.
the lead-calcium, despite the claims made for it by GM has always been a dog - being reluctant to give its amps, taking time to come up to voltage and needing charging for twice as long as the others.

I also have an Adverc smart regulator, a 3-way splitting diode, a wind generator and 85 (nominal) watts of solar power.
I also have an electric fridge, a computer, hi-fi and lighting.
Below 45degrees latitude, and with a working breeze (>10 knots) during the summer I don't need to start the engine whilst at anchor.

If there is no breeze the two batteries last 50 hours before voltage drops to <12.5.

1 hour of charging at 1200 rpm gets the system voltage back to 14.2 (I've a 90 amp alternator).

My reading of the situation is that before doing anything else it is necessary to replace the standard regulator.
It would be desirable to fit a splitting diode.
It may be necessary to have a larger alternator - if so wiring and belt-drive probably will have to be beefed up.

Meanwhile charge one battery at a time to full charge (use an hydrometer to test) and don't bother about any differentiation between batteries.

 

[Guest]

We have a similar viewpoint, but not 100% ...... as I do use a 'Car battery' for domestic ... infact I run a inverter of iit as well !

I have a Halfords cheapie charger fitted to a On-off-On switch, having each battery connected to a side of thge switch, so I can flick charge from one to the other when alongside, I have the standard bog A-Both-B-Off battery switch and never seen need to fit anything else ... I do w/end cruising with max's of 4-5 days and not had problem. My batterys are HD Diesel rated 100 A/hr jobs from the local Tyre and battery dealer.

I will fit sophisticated systems when I need 'em ... until then I enjoy reading others views on them !

Cheers
Nigel L

 

[ccscott49]

I am a liveaboard, my boat has a large power requirement, two fridges, lights a freezer on 1.8kw inverter and stereo etc. I have twin engines, the port engine charges the engine starting battery bank of 24 volts 210 ah. this is all it does, so I use standard truck lead acids, 4 of them. The starboard engine charges the domectic batteries through a sterling smart charger, they are semi deep cycle, 315 ah 24 volt, 6 batteries. I only use the engine start for that purpose, they are 8 years old and in excellent condition,(semi sealed) the domestics take a fair hammering and are 10 years old and also in prime fettle (semi sealed, magic eye) I also have a genny 4kva with smart 60a 24 volt charger with splitter, which is also on shore power. No solars, the boat is too power hungry no wind genny not very good in med. I get two days before running genny or engines in the med on my domestics. I think my system works quite well!

 

[Guest]

QED ...... there's me as a lowly w/end lad surviving on lead acid car battery's ..... and a liveaboard surviving on a bank of lead acid car battery's
Can't get better than that !!!!!

Actually - I am considering a third battery to isolate out some parts of the boat domestics or navigational crap - and that may be a Caravan shops Leisure battery ........... it's an idea that's been floating, (forgive the pun), around my head for a while. I don't need it, but would be nice !!!!!

 

[ccscott49]

Nigel, I got mine form Exeter battery services, £30 for a 105 ah, semi traction, semi sealed magic eye, made in south africa and excellent.