Organising new batteries/old space

[oldbilbo]

I'm looking for the best arrangement I can make with the constraints of limited space.

I've removed two old 110Ah 'wet' batteries from boxed-in positions under the quarter-berths P & S. One of these batteries still seems to hold a charge. T'other is dead and gone.

I've acquired 3 new AGM batteries, from two makers: 1 x 110Ah by Varta, and 2 x 66Ah by Optima ( prices were right ).

My normal electrical needs will be relatively modest.... with engine start, nav lights, occasional Autohelm, a Yeoman Plotter, limited internal lights, VHF, GPS.... and maybe some musak of an evening. All the lights will be LED.

I'll have engine alternator, 2 x 40w PV panels, a suitcase genset. Now and then I'll have need to run an inverter to power a 'breathing assist' machine when SWMBO sleeps on board.

I'll certainly need to do some carpentry to provide new secure stowages, and I'm not averse to buying more battery kit if warranted.

How might I best arrange and make use of what I have?

 

[Pete7]

How about selling one of the 66ah Optimas and buying another 110 AH Varta then using the two Vartas for the house and the Optima for the engine start. We also have a 220 AH house bank and probably use 20% an evening during the summer going up to 35% in the winter if the heating is on. You could have the Varta as the engine start and the two Optimas as the house but the Varta is a big battery and bit of a waste.

Pete

 

[Plevier]

Pete7 has a good scheme.
I really would not mix Optima and Varta as parallel strings as you suggested in another thread, they are just too different, even if the Varta is AGM.

 

[Pete7]

There is a fairly good chance they will end up linked together for charging, either by a VSR or a 1-2-0 rotary battery switch. However, I haven't found a problem with our Varta flooded lead acids and the Red Flash AGM starting battery. They have lived together happily for some years now.

Pete

 

[sarabande]

Both makes are deep cycle and can therefore be expected to take a battering from being used overnight when there is likely to be no charging.

It looks as if your power requirements will be much skewed to the domestic side, so I'd use the Varta as the engine battery (110Ahr and how many CCA?) and the slightly higher capacity Optimas as the domestic set.

Perhaps you could use the two Optimas as separate OR combined domestic batteries, and cane No 1 first, then swap to No 2 (with a fuller charge) OR use both combined. Charging could then be directed to all possible combinations:-

1 to all three at one time, or

2 to any one on its own, or

3 to the two linked domestics, or -conceivably -

4 to the engine and either of the domestics.


depending on the state of charge of each battery, the available charge amps, and the anticipated load or need for a reserve.


Are you planning to have an intelligent battery monitor to give you % state of charge ? That would essential to enable you to undertake sophisticated management.


Oh, and a set of jump leads as belt, braces, and string.

 

[oldbilbo]

......Oh, and a set of jump leads as belt, braces, and string.

Perhaps

Fork 'andles....

 

[lpdsn]

It looks as if your power requirements will be much skewed to the domestic side, so I'd use the Varta as the engine battery (110Ahr and how many CCA?) and the slightly higher capacity Optimas as the domestic set.

Or just get a dedicated starter battery that has been designed as such. Not as if they're expensive compared to deep cycle batteries.

 

[Storyline]

Or just get a dedicated starter battery that has been designed as such. Not as if they're expensive compared to deep cycle batteries.

Yes, it does seem a waste to use one of those nice AGM batteries for the engine start. Have always used a truck battery obtained from a place that does plant hire etc. Nothing special about them but seem to last for ages and always show a healthy voltage. The windlass is connected to it but we are careful to motor & charge it after lifting the anchor.

As already suggested why not use all three for domestic use, separated if they are not suitable to be connected together and then get a starter battery ? Seem to recall you can get physically small high cranking amp batteries if space is that tight. Makes more sense financially to me as those 3 AGMs should last a long time if not taxed too much.

 

[pvb]

Perhaps you could use the two Optimas as separate .... domestic batteries, and cane No 1 first, then swap to No 2 (with a fuller charge)

This is never a good idea. The batteries will provide more power, and last much longer, if they're combined.

 

[vyv_cox]

I use an AGM as a starter battery simply because it has such power for its size. I was able to mount it alongside the gearbox in an upright position but the beauty of them is that they can be in any orientation. I know of one AGM used for starting for the past 10 years. Red Flash 1100.

I fully agree with the others, the bigger the battery bank, the better. When my bank was 2 x 110 Ah the voltage after a night on the fridge was often 12.0 but with 3 x 110 Ah it is rarely less than 12.6 first thing in the morning in June/July. Deep cycling kills batteries!

 

[oldbilbo]

It's beginning to look like I should try for the following arrangement:

Port side - 1 x 110Ah plus 1 x 66Ah, each AGM ( due to having them ...and the space constraints )

S'bord side - 1 x 110Ah plus 1 x 66Ah, each AGM ( buy another 110Ah Varta AGM ...and the space constraints )

Buy another smallish AGM battery specifically for engine start, then find somewhere to mount it.... perhaps within the base of the revamped companionway steps-cum-navseat...? Maybe I could use the remaindered 110Ah 'wet' battery for that task, until it dies, then replace it with a smaller AGM thingy.

The 'start' battery could be engine-recharged routinely by preference, while the two 'services' banks P&S could be used separately or jointly, and kept charged/recharged via the two PV panels, mini genset, and/or engine selectable.

Is this too complex for a 'bear of little brain'....?

Thots?

 

[RobbieW]

I suspect that underlying a part the concern in mixing the Varta and Optimas is that, although both are AGM, they are slightly different technologies. The Optima's I'm 99% sure will be spiral wound batteries and the Varta's a more traditional plate type construction. I believe the charging regime for the two types to be different for best effect, I'd look into that before deciding on the mix.

 

[Storyline]

.....

Buy another smallish AGM battery specifically for engine start, then find somewhere to mount it.... perhaps within the base of the revamped companionway steps-cum-navseat...? Maybe I could use the remaindered 110Ah 'wet' battery for that task, until it dies, then replace it with a smaller AGM thingy.
.....

Not sure I would feel happy, in fact I would be unhappy using a nearly clapped out battery as a starter. Realise you also have the others as backup but we treat our engine battery with a great deal of reverence. Then do not have to worry about the domestics too much in case anything gets left on (of course try to look after them but not obsessively so).

If a nice small AGM (as per Vyv) is out of budget a truck battery is cheap.

 

[GHA]

Not sure I would feel happy, in fact I would be unhappy using a nearly clapped out battery as a starter. Realise you also have the others as backup but we treat our engine battery with a great deal of reverence. Then do not have to worry about the domestics too much in case anything gets left on (of course try to look after them but not obsessively so).

If a nice small AGM (as per Vyv) is out of budget a truck battery is cheap.

Bearing in mind even a nearly dead battery can still kick out a lot of cca..

From

http://batteryuniversity.com/learn/article/how_age_affects_capacity_and_resistance