New deep cycle battery?

Hi Judo and as Garry posted, the 12.6v would mean the battery is being charged as a fully charged battery has a rested voltage of 12.7v.

So the 12.6v cut-in ( cut back ) is designed to allow the battery to have some of it’s used capacity replaced before the fridge starts drawing power from the battery again.

Your battery may need nothing more than a good charge, so try that first before you do anything else.

Now to that voltage drop. The 0.2v drop at the battery is fine but that 1.0v drop at the fridge is huge for such a small load.

You need to check out your wiring and see why you have such a large voltage drop.

I suspect it is, as others have posted, undersize wiring.

Hi,

Totally agree with Drivesafe.

I have a 40l Primus that has performed faultlessly when plugged into the ciggy lighter in a Ford Courier or running off the mains.

Went away with it plugged into the RR ciggie lighter and it would behave exactly as you describe yours doing. Voltage was fine (13, way above set cut out of 10.5).

Was thinking warranty on the fridge but checked it out with the old power sources and it ran fine.

Came to the conclusion that the voltage was accurate but the wiring in the RR to the ciggie lighter is not heavy enough to deliver enough amps.

Do the wiring first and see how you go. Battery may be fine.

DL

Well I kept myself busy yesterday...

I purchased some 8 AWG wire as jaycar didn't have any 6 in stock. Ran a lead from the aux battery under the cabin carpet into the rear of the Disco making it as short as practical. Put Anderson plugs on that and shorten the 16AWG fridge lead.

I also made room for a bigger aux battery just in case. Relocated the PAS reservoir and battery separator. So little room to move stuff.... I hope my measurements are right, coz I've only left a few mm space!! She'll be right mate! :D

OLD wiring stats:
Rear plug open circuit: 12.35V
Rear plug with load: 11.2V

NEW wiring stats:
Rear plug open circuit: 12.38V
Rear plug with load: 12V (0.8V increase! :) )

On the old wiring, I could only get my fridge to run for 2 hours, I have no idea how the previous owner used the plug for anything. Fridge successfully stayed cold overnight after being on for 14 hours. :D So that's a big win and I'm confident my wiring issues are behind me.

In terms of battery capacity / needing a new battery:

Fully charged (just from driving around with alternator) checking voltage on battery terminals:
Battery open circuit: 12.4V
Battery with load: 12.2V

14 hours of fridge running used 263 watt hours of power. 22A @ 12v. Battery is rated at 82AH.
Battery open circuit: 12.0V
Battery with load: 11.7V
The indicator light on the battery was red meaning "recharge now".
Based on these voltages, I'm thinking the battery is circa 25% remaining. I.E. Almost flat.

So I'm thinking the battery is still less than in good condition?
I'm thinking a 100AH+ new deep cycle battery would mean I could run the fridge for 24 hours without running the battery too low.

Judo,

Amazing what a difference decent wiring makes! Did you do the negative run back to the aux battery too?

How much driving around did you do? You might need more than a couple of hours to get the AUX fully charged. It's probably worth putting the AUX on the charger overnight and then retesting.

cheers
Paul

Quote:

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Originally Posted by OffTrack

Judo,

Amazing what a difference decent wiring makes! Did you do the negative run back to the aux battery too?

How much driving around did you do? You might need more than a couple of hours to get the AUX fully charged. It's probably worth putting the AUX on the charger overnight and then retesting.

cheers
Paul

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Yep, negative run back to aux battery. I assume you're hinting that I could chassis earth the neg in the rear of the Disco. I hadn't considered that actually. What are the pros/cons to doing that for a rear socket and running a fridge?

Chassis is the equivalent to a massive wire?
Less than regular voltage with interference maybe?
:confused:

2 weeks ago I did 300kms freeway driving. A few runs around town since. Maybe not the same as a trickle charger, but must be pretty close to charged?! In fact, that reminds me - I did a 10min trip last night, so the battery even got a short burst of charge during that 14 hours of fridge running.

No, just wanting to make sure you HADNT used the chassis!! Cable negative is better option. :)

If you haven't used for a couple of weeks I'd expect the charge would be down. Not sure what the self discharge rate is on lead acid it's in the range of 5-20% per month. Worst case you might have lost 10% charge in 2 weeks. Depending on how low the battery was, it could take up to 4-5 hours driving to fully recharge.

Hi Judo and as OffTrack already covered, your driving time is not enough to charge the batteries and a low battery can take up to 10 hours of constant charging before it reaches a full state of charge.

This does not mean putting the battery on a charger until the charger goes into FLOAT mode.

The battery still needs to remain in FLOAT mode for up to 10 hours to get the battery fully charged.

Righto - I'll get the charger out tonight and leave it on at least overnight, maybe 24 hours or more....until I drive next... Then re-run my fridge test.

However, all this talk (by me) of a new larger capacity battery almost has me convinced I should get a new one anyway. :D :D A little more talk and I'm there. Although with my existing battery at the level it is - lets say 80% if properly charged - I would probably keep it and take on any long camping trips as extra capacity. If it gives me another 10-15 hours on big trips for another year or two it's worth hanging onto...

Just don't tell SWMBO we don't really need a new battery. Buying new stuff is fun. :cool:

Quote:

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Originally Posted by Judo

Righto - I'll get the charger out tonight and leave it on at least overnight, maybe 24 hours or more....until I drive next... Then re-run my fridge test.

However, all this talk (by me) of a new larger capacity battery almost has me convinced I should get a new one anyway. :D :D A little more talk and I'm there. Although with my existing battery at the level it is - lets say 80% if properly charged - I would probably keep it and take on any long camping trips as extra capacity. If it gives me another 10-15 hours on big trips for another year or two it's worth hanging onto...

Just don't tell SWMBO we don't really need a new battery. Buying new stuff is fun. :cool:

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You really should think about one of the Traxide isolators if you don't have one installed. They are seriously good bit of kit.

Because they run off both batteries down to about 50% SOC it really boosts your run time. The other advantage is you tend not to discharge the aux nearly as far so it doesn't take as long to recharge to full.

cheers
Paul

Supercharge batteries have a product called an "All rounder" ...it's a deep cycle (105AH) and starting battery. standard terminals for big lugs plus separate threaded terminals for aux. stuff. I bought 2 for a Cape trip a couple of years ago as deep cells for camper trailer connected to a Traxide magic box. One now sits up front (P38) as the starting battery. They've been very good. Best news is that I got a 'very' sizeable discount on the RRP because I told the bloke I was an AULRO forum member. One of our number who was/is in Sales at Supercharge managed to put this 'benefit' in place three or 4 yrs ago! It's worth checking. Also don't forget that any 100AH deep cell in reality has only 50% of that capacity before it needs a recharge....