deep cycle batteries

i have been looking at deep cycle batteries,what would be best. will be running a barfridge through an inverter. would a 100amp hr suffice in a caravan will not be connected to the car battery charging will be via generator

thanks ross
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Reply By: Battery Value Pty Ltd - Friday, Jun 04, 2010 at 16:40

Friday, Jun 04, 2010 at 16:40
Hello mongrel,

if it's a small 240VAC fridge, it'll probably use somewhere between 0.4 and 0.8kWh per day.
You get a good indication of this if it's fitted with an energy rating sticker.
A 12V 100Ah battery would be just within range. Albeit it might struggle a bit at the higher end of 0.8kWh/day.
That is, if you only recharge once per day.
If you recharge twice in the morning, and evening, things look much better.
It might be feasible to put 2x100Ah battery to work, because then the recharging times are shorter, not only because your max peak charging current can be twice as high. The absorption stage is also shortened if the battery gets discharged less.
For the fastest high current recharging times, select pure lead/tin spiral wound AGM technology which allows for the quickest recharging times.
Pure lead/tin also can stand PSOC conditions a lot better than any other alloy.

Have a look in my profile to find out more.
Any questions, just fire away.

Best regards, Peter
AnswerID: 419542

Reply By: Tenpounder (SA) - Friday, Jun 04, 2010 at 16:40

Friday, Jun 04, 2010 at 16:40
Hi there. It's a bit hard to reply without knowing the power requirements of the bar fridge. But let's estimate that it draws about 1 amp at 240v (ie 240W). That's about half way between a caravan 3 way fridge and a 240v household small fridge.
Through an inverter, assuming the inverter is 80% efficient, that equates to 24 amp at 12v draw on the deep cycle battery. So a 100 AH battery would be down 50% (ie flat) in 2 hours and beyond repair in 3 hours!!
Unless I have stuffef the maths, then I suspect your idea may need revisiting, or else you'll be running the genny most of the time, which isn't nice for you or anyone around you.
AnswerID: 419543

Follow Up By: Tenpounder (SA) - Friday, Jun 04, 2010 at 16:56

Friday, Jun 04, 2010 at 16:56
If Peter is right (and I'm not saying he isn't!!), then a bar fridge will draw about 0.1amp average at 240v. If so, then you should be OK for around 20hrs. So it really boils down to getting an accurate figure for the power requirement of your fridge, all all the commnets so far have stated.
Good luck
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Follow Up By: Battery Value Pty Ltd - Friday, Jun 04, 2010 at 17:27

Friday, Jun 04, 2010 at 17:27
Hello Tenpounder,

a good quality AGM lead/calcium/tin battery can give you 500 cycles at 50% DOD.
And around 250 cycles if you discharge it to 100% (10.5V cutoff).
AGM lead/calcium/tin cycle life

To achieve this AGM advantage over flooded lead acid, you have to fully recharge before the next discharge session.
Otherwise, you're subjecting the battery to PSOC conditions (partial state of charge) which negatively influences cycle life.
Pure lead/tin have the best resistance to such kind of demanding operating conditions.
I suppose meanwhile you've looked into your anticipated power figures one more time ;)

Best regards, Peter
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FollowupID: 689735

Follow Up By: paulnsw - Saturday, Jun 05, 2010 at 07:48

Saturday, Jun 05, 2010 at 07:48
The document 'AGM lead/calcium/tin cycle life' is dream time figures of the mushroom toads. Those figures may be obtainable in the battery manufacturers laboratory but would never be attainable by users in the field.

If you managed to get 50% of the published figures in actual use using commercial battery chargers you would be doing well.
If you discharged the battery to 100% if you managed a 100 cycles you would be doing well.
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FollowupID: 689790

Follow Up By: Battery Value Pty Ltd - Saturday, Jun 05, 2010 at 08:13

Saturday, Jun 05, 2010 at 08:13
Paul,

you may have noticed that I stated the conditions for achieving these figures.

>>>>you have to fully recharge before the next discharge session.<<<<<<

Subjecting the battery to PSOC conditions will negatively affect cycle life.

The great majority of VRLA batteries are subject to PSOC conditions for various reasons. Solely relying on the alternator for charging a battery which is used in cyclic applications is one of them.

Note that I don't suggest to discharge any battery to 100% DOD on a regular basis.
A 50 to 80% figure is much more manageable not only in terms of improved cycle life but also in terms of charging times, using a quality multistage battery charger.
The long 'tail end' of the boost charging process (absorption stage) with high voltage/low current charging requirement can be facilitated by solar or other low power sources.
This helps to cut down generator run times if applicable.

Best regards, Peter

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Follow Up By: paulnsw - Saturday, Jun 05, 2010 at 20:28

Saturday, Jun 05, 2010 at 20:28
Peter Battery Value the claims made in the PDF file are completely unattainable in the field using a standard commercial battery charger
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Reply By: fugwurgin - Friday, Jun 04, 2010 at 16:52

Friday, Jun 04, 2010 at 16:52
Hi Ross
an inverter is a very innefficient way of running anything let alone a fridge that will be no doubt running non-stop. To answer your question, i would suggest hooking up your fridge to the inverter (i would get it to running temp on 240v first), put an amp meter between the inverter and the battery and measure how many amps are being drawn, then wait for the compressor to kick in and measure it again. The answer may surprise you as it will probably be quite high. A 100amp hr battery in theory deliver 100 hours of power at a current draw of 1 amp. I am under the understanding to protect the battery that you shouldnt drain it by more than 50% SOC (state of charge) which i believe is around 12.1 volts. i am also under the understanding (someone will correct me if im wrong) that therefore this halves the running time to 50 hours (based on a 1amp draw). Different battery types have different levels of tolerance to this, usually the dearer you go the better the tolerance. But knowing the amp draw and the intended run-time of the fridge would be required to answer the size of the battery required.
I would only guess but the fridge may draw up to 6-10 amps when the compressor kicks in, this would not give you much run time. Also will your inverter handle the fridge at full power ie compressor going in terms of its constant wattage (not peak)
The generator is also a very inneficient way of charging your battery especially if it is under load at the time when you are charging it (unless you switch to running the fridge straight from the genny whilst you charge).
I would personally consider a solar panel to keep it somewhat topped up during the day, then the genny wont have such a big job to get the battery up to full.

If you had the spare money, i would reccomend a small 12v\240v compressor fridge such as a waeco, engel or ARB (just examples), a 100ah battery and perhaps consider hooking it up to the car to charge whilst you drive via an isolator. i know that wasnt your question, but my opinions are free, and if you dont like them- i have others!

good luck with it!
AnswerID: 419547

Reply By: Maîneÿ . . .- Friday, Jun 04, 2010 at 17:20

Friday, Jun 04, 2010 at 17:20
Ross,
Is there a reason why the battery won't be connected to the vehicle for charging when your traveling ??

As others have said you have to know the fridge power draw befor an answer is given, unless you want guess work replies.

Maîneÿ . . .
AnswerID: 419551

Reply By: dbish - Friday, Jun 04, 2010 at 18:44

Friday, Jun 04, 2010 at 18:44
Hi Ross, Iused an 80L bar fridge in my van & ran it of a 240V inverter when travelling it pulled 12Amp of the battery. When stoped used a generator till we went to bed then switched it off till morning. Eventualy went to a Waeco 80L upright fridge which draws 6Amp of battery, much more eficient & more than happy. Only using an N70ZZ battery on van A frame & charged buy vehicle altenator or battery charger if 240V avalable. Daryl
AnswerID: 419569

Reply By: paulnsw - Saturday, Jun 05, 2010 at 07:51

Saturday, Jun 05, 2010 at 07:51
Ross the only practical way to power the fridge on 240V while travelling would be to have a 600W (minimum) sine wave inverter in the vehicle and run 240V across to the fridge in the caravan. The sine wave inverter would need to be connected to the vehicle battery using a Redarc SBI12 Battery Isolator. Attempting to power the 240V fridge any other way would be a short term disaster.
AnswerID: 419605

Follow Up By: Maîneÿ . . .- Saturday, Jun 05, 2010 at 08:36

Saturday, Jun 05, 2010 at 08:36
""The only practical way to power the fridge on 240V *WHILE TRAVELLING* would be to have a 600W sine wave inverter *IN the VEHICLE* and run 240V across to the *FRIDGE IN the CARAVAN*""


* NEVER, EVER DO IT THAT WAY . . . grrr


The inverter MUST be in the vicinity of the FRIDGE and a BATTERY and ALL items should be IN the CARAVAN or in the vehicle.


You CAN'T SAFELY run 240 Volts from a vehicle back to a caravan.
Attempting to do as posted is LONG TERM disaster as is death.

Maîneÿ . . .
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FollowupID: 689798

Follow Up By: paulnsw - Saturday, Jun 05, 2010 at 20:26

Saturday, Jun 05, 2010 at 20:26
Mainey perhaps you may enlighten members with your professional qualifications. Mainey what are your professional qualifications?

Of course you can safely run 240V from a vehicle to a caravan.
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FollowupID: 689883

Follow Up By: Lex M (Brisbane) - Saturday, Jun 05, 2010 at 21:11

Saturday, Jun 05, 2010 at 21:11
Paulnsw what are your professional qualifacations?
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Follow Up By: Lex M (Brisbane) - Saturday, Jun 05, 2010 at 21:16

Saturday, Jun 05, 2010 at 21:16
Maîneÿ

I hate to admit it but I agree with you.
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Follow Up By: Maîneÿ . . .- Saturday, Jun 05, 2010 at 21:18

Saturday, Jun 05, 2010 at 21:18
So are you using the words "while travelling" to mean when stationary ??

I would not use the terminology "only practical way to power the fridge on 240V while travelling would be to have"

I would have stated "only practical way to power the fridge on 240V while CAMPING would be to have"

However, I do still have concerns about having the 240 Volt inverter and battery situated in the vehicle away from the fridge situated in the caravan, even when stationary.
Reason is because the 240 volt cable has to run out in the open between 2 vehicles (car and caravan) as you have posted 'a 600 Watt inverter is in the vehicle and run 240V across to the fridge in the caravan'
I can only believe the cable goes out from, and into the 'vehicles' via a window or door, so yes, I do believe it's dangerous.

As I've said, the inverter, battery and fridge should all be in same vehicle.

You would not be able to power the fridge on 240v when it's in the caravan and stationary at a camp site, and you have gone for a drive in the vehicle, because the inverter and battery has obviously been taken away with the vehicle.


Lex,
Thank you :-)

Maîneÿ . . .
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Follow Up By: paulnsw - Sunday, Jun 06, 2010 at 07:07

Sunday, Jun 06, 2010 at 07:07
This post has been read by the moderation team and has been moderated due to a breach of The Trolling Rule .

Forum Moderation Team
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Follow Up By: ModSquad - Sunday, Jun 06, 2010 at 09:34

Sunday, Jun 06, 2010 at 09:34
Despite all the cautionary messages that have gone before some people are still trying to start an argument and bloat the thread with lots of woffle. There are lots of good replies and information that evolve from these very interesting topics so why can't we all try a bit harder to keep things on topic without the agro.

Threads have been going good lately, so lets keep it up.

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