Batteries arrangement

[oldbilbo]

I'm puzzled. More than usually...

Y'see, I have some new batteries to install in my quite simple 27' sailyboat, and I can't quite make up my mind about an optimum arrangement. The previous setup was 2 x 110AH wet batteries, one each side in an under-berth box. One of those had died, while the other seems to have some life left, in that it seems to hold a charge for more than a day or two.

I've acquired 3 new AGM batteries, 2 x 66AH and 1 x 110AH.

There's a simple 1-BOTH-2-Off control, and I have several Key-type Connectors which I might fit, if so persuaded.

The 12hp engine drives a basic generator.

Loads are likely to be modest, as I'm replacing ALL incandescents with LED and I'll use self-contained battery-driven LED lighting for much of the night lighting need. There's no radar. I tend to switch off electronic nav gear when I'm not actuially using the info, including sounder when out of soundings, and GPS when I can see my posiiton on the landscape when I need to - apart from fog/rain/smirn/night.

I'll have two modest PV panels which I can use to help recover battery energy used, together with a small genset. So, how best might I arrange my battery layout re Services/Engine Start....... considering that I'm likely to need to change the containers/stowage arrangements.

 

[No Regrets]

Er, one 66AH for Start, the remainder for services?

The 66AH will start a 2 litre Diesel, so no problem with your Cement mixer engine

Or, if you like belt and braces, keep one 66AH for an 'Emergency' battery. I have such a thing, and the one time I used it, it was good...

Mind you I have no sails!

 

[sarabande]

I can't see a compelling reason for anything apart from the usual Engine - Domestic split.

If you want resilience for the engine starting, then the 2 66s go for the Engine side, and the 110 on the admirably economical Domestic side. However if you are satisfied that the 110 is not going to let you down, the Engine has the 110, with Domestics picking up the two 66s.

In that case, it might be useful to arrange for the 66s to be set up as Batt A and Batt B, and for only one of them to feed the domestic supply at a time. So if ever you flattened Batt A, you would still have Batt B left (say) to power instruments on a foggy finals approach while you sort out recharging Batt A.


Charging ... I'd prefer to charge Engine and Domestics separately with the PVs /gennie. Just in case of a diode or VSR failure while you were ashore, which conceivably could flatten all three if they are linked for a full 3 unit charge.


Your charging systems seem to have enough redundancy to allow you to do anything to any battery in any configuration, though.

(The last item in the electrical battle box is a set of jump leads )


EDIT
If a 66 will start the yacht engine with confidence, then an alternative is to have Batt A (66) as your prime engine starter, the 110 as the main Domestic one, and Batt B (66) as a backup for Engine OR Domestic. That might require some clever cabling and switching though.

 

[JumbleDuck]

As far as starting goes, it's the CCA (Cold Cranking Amps) rather than the Ah which matter. If one of your 66Ah batteries has the CCA grunt to start the engine I'd say use 66 for engine and 110+66 in parallel for domestic. If the CCA aren't enough, I'd flog one of the 66s and buy a suitable car starter battery instead.

For what it's worth, I have almost finished swapping to 60+60 domestic (no room for bigger) and a car battery for engine start. With the same parsimonious approach to power you take, and LEDs everywhere, I expect to get at least two weeks' normal use, including lots of overnights, without charging and I hope that the 100W of solar panels I have just fitted will keep up with all my normal use.

 

[oldbilbo]

I can't see a compelling reason for anything apart from the usual Engine - Domestic split.

If you want resilience for the engine starting, then the 2 66s go for the Engine side, and the 110 on the admirably economical Domestic side. However if you are satisfied that the 110 is not going to let you down, the Engine has the 110, with Domestics picking up the two 66s.

In that case, it might be useful to arrange for the 66s to be set up as Batt A and Batt B, and for only one of them to feed the domestic supply at a time. So if ever you flattened Batt A, you would still have Batt B left (say) to power instruments on a foggy finals approach while you sort out recharging Batt A.


Charging ... I'd prefer to charge Engine and Domestics separately with the PVs /gennie. Just in case of a diode or VSR failure while you were ashore, which conceivably could flatten all three if they are linked for a full 3 unit charge.


Your charging systems seem to have enough redundancy to allow you to do anything to any battery in any configuration, though.

(The last item in the electrical battle box is a set of jump leads )


EDIT
If a 66 will start the yacht engine with confidence, then an alternative is to have Batt A (66) as your prime engine starter, the 110 as the main Domestic one, and Batt B (66) as a backup for Engine OR Domestic. That might require some clever cabling and switching though.

I'm tempted to revisit the idea of sweeps, and a pressure paraffin Tilley lamp. THAT I can understand......

Oh, I forgot to mention an unmentioned 'power need'. Music, offshore. When no-one else is around, 'Thunder and Lightning Polka' and '1812 Overture' as loud as I can project, esp. in the night, to say nothing about Gilbert and Sullivan at top vol! That's going to consume a few ergs.....

 

[Gwylan]

I'm puzzled. More than usually...

Y'see, I have some new batteries to install in my quite simple 27' sailyboat, and I can't quite make up my mind about an optimum arrangement. The previous setup was 2 x 110AH wet batteries, one each side in an under-berth box. One of those had died, while the other seems to have some life left, in that it seems to hold a charge for more than a day or two.

I've acquired 3 new AGM batteries, 2 x 66AH and 1 x 110AH.

There's a simple 1-BOTH-2-Off control, and I have several Key-type Connectors which I might fit, if so persuaded.

The 12hp engine drives a basic generator.

Loads are likely to be modest, as I'm replacing ALL incandescents with LED and I'll use self-contained battery-driven LED lighting for much of the night lighting need. There's no radar. I tend to switch off electronic nav gear when I'm not actuially using the info, including sounder when out of soundings, and GPS when I can see my posiiton on the landscape when I need to - apart from fog/rain/smirn/night.

I'll have two modest PV panels which I can use to help recover battery energy used, together with a small genset. So, how best might I arrange my battery layout re Services/Engine Start....... considering that I'm likely to need to change the containers/stowage arrangements.

Junk the 1,2,3 all flat switch!

110Ah for engine starting on discrete circuit

2x 65Ah for the domestic, paralled up.

VSR or diode to share out whatever the alternator can output.

Get a battery protector, stops the battery voltage falling below preset level - put in the music system circuit. Then you can be loud as long as you have the energy.
http://www.maplin.co.uk/p/kemo-12v-dc-battery-guard-n81ql

Have a set of jump leads on board in case you need to use everything to get the engine started

 

[causeway]

1x66 for the engine, the rest in parallel.

You'll get the most out of your domestic bank if you're never getting below 60 percent or so. Although I doubt you'd get that far anyway!

 

[William_H]

The first thing to do is to mount the 3 batteries. However you might find it easier less hassle to just fit 2 in the existing boxes.
I think it desirable to be able to switch any or all 3 on at any one time. So simplicity is a switch from each pos to the common bus. Heavy wire to the starter solenoid and heavy wire connecting all negatives. A really good system would then have a VSR to connect all positives to the alternator output when engine is charging. That would be an auto system or just rely on you remembering to turn all batteries on after engine is started. Then just use one battery at time for domestic to ensure you keep one for engine start.
Note it is important to occasionally check that each battery alone will start the engine.
However with a simple low domestic load system many people end up just turning all batteries on for engine start charge and domestic discharge and seem to get away with it for a long time. Simply because the total paralleled batteries are so big.
Regarding solar charging. I would use a small panel relative to the battery size and simply use 3 diodes mounted at the pos battery terminals to charge all batteries even when turned off and with no regulator. if you think you need a regulator get one designed to feed 3 batteries independently. I think a 10 w panel would be fine with no regulator. Possibly up to 30 w if feeding all 3 batteries.
good luck olewill