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Boiling Batteries


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#21 island time

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Posted 01 January 2018 - 01:53 PM

Nope, battery is knackered, if it dropped to that with no load...
Replace it.
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#22 harrytom

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Posted 01 January 2018 - 02:20 PM

IT, what size would you recommend for a house battery that is primary used for lighting and fridge (waeco cfx 40)?

 

when not using yacht bring it home and trickle it??


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#23 wheels

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Posted 01 January 2018 - 05:43 PM

Was the battery size you had, OK for keeping everything running without discharging too far? If yes, then replace with the same size. I see that Supercheap are now stocking Optima. A very very good Battery. But damn expensive. However, so are most very good Deep Cycles, so the same capacity may not be a lot different between comparable makes. There are certainly cheap Deep Cycles out there. You certainly get what you pay for.

When not using yacht, do you have any form of trickle charging on board? such as a Solar panel? If not, then yes, take home and trickle.Lead Acid of any kind do not like sitting uncharged for any length of time.
Basically, as soon as a Battery starts to discharge, they start a slow process of dying. The greater the discharge and the longer it is left that way, the more the damage done. The faster you can restore the charge to full capacity, the faster you get it up away from the damage being done to the plates.
 


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#24 island time

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Posted 01 January 2018 - 06:20 PM

What wheels said.
Plus, what does the fridge draw. Plus how long does it run on an average summer day. We are after how many amp hours consumed each day. Then we look at recharge, and how you put those amp hours back. Then how many days you wish to run without recharge.
Remember that a lead acid based battery should not be reduced by more than 50%. Can calculate required battery size from that.
I can supply batts if you like, but as I said before, I'm not back until 19 jan
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#25 harrytom

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Posted 01 January 2018 - 06:30 PM

Thanks for the replies and advice.Will look at solar in the future,meantime will replace and bring home,not that much trouble to do.

no idea what fridge draws but very efficient unit. Waeco.


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#26 island time

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Posted 01 January 2018 - 07:31 PM

Measure it, what's it draw when it's on, how long does it run before switching off, how long gone till it switches on again...
You can do that at home.....
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#27 Chloe

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Posted 02 January 2018 - 05:08 AM

Thanks for the replies and advice.Will look at solar in the future,meantime will replace and bring home,not that much trouble to do.

no idea what fridge draws but very efficient unit. Waeco.

Your Model use's about 0.78amp per hour. 


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#28 wheels

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Posted 02 January 2018 - 06:09 AM

Even a little portable Solar panel for trickle charging would be fine on the boat when you are not aboard. Providing the battery is fully charged before you leave. They have no show of charging the battery, but can happily keep one topped up.

Re the 50% comment. It is important to understand that as soon as a LA battery starts to discharge, it also starts to deteriorate. The speed it does so increases with the depth of discharge. The 50% rule of thumb came about as a Sum of Battery Cost/length of life.  If you consistently discharge below 50%, then the battery will not last long. Replacement is expensive. If you never discharge below a few percent, the battery may last much longer, but you never really needed the capacity, so it was a waste of money. 50% is considered the best efficiency in Amps produced over it's life to Cost ratio.
Something to watch out for in Warranties when purchasing a cheaper Deep Cycle. They often on warrant a Deep Cycle for X many years providing the Battery has never been discharged below 20%. And that has to be able to be proven. For many boat installs, that is not possible, because only the really expensive regulators have that facility. So you need to ask the supplier what the Warranty entails and do need proof of discharge floors, or your warranty may be void.


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#29 Knot Me... maybe

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Posted 02 January 2018 - 07:52 AM

Plus how long does it run on an average summer day. We are after how many amp hours consumed each day.

Depends on how often it's opened but I'm very happy working on a 1Ahr average consumption. If it's just sitting there it'll be a less, quite a bit less, but 'in use' 1amp is a safe number to use. May spike a little higher if it's sitting in the sun with kids opening it every 10 minutes.

 

It draws around 4.5-5amps when the motor is running.

 

I have the same fridge and have been using it to help get the battery monitor synced to the battery.


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#30 island time

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Posted 02 January 2018 - 08:19 AM

OK, so a (very) rough calculation then, fridge 25 amp hour, lights say 3 hours, 3 amps total draw say 10 amp hours. That's 35 amp hours per day. So that's a min 70 amp hour battery - I'd go for a 100, provided it will fit in your battery box.
Also, consider your charging - the last 20 percent of charging takes hours. Many cruisers only ever charge to 80% for this reason, unless on shore power. The 100amp hour battery gives you that ability.
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