fridge or battery

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: fridge or battery

Hi again Tinkera, you need to give your battery at least 12 hours before taking a voltage reading because the battery will hold a surface charge for anything up to 24 hours but most will be close enough to their actual SoC after 12 hours to give you a fair idea.

Your switching voltages of your isolator are fine.

[tinkera Member Find all posts View Profile Close tinkera]

Re: fridge or battery

HI drive safe.Just saw your posts on charging rates ops: don,t want to kick that off again but I was interested in your post on cable sizes.Iam running electra ebs 821 from engine bay to behind 2nd row seats ,cant find any info on this cable to compare with your spec,s run vs no of batt,s etc.Tested alt charge today at idle 14.1v at crank 14v at AGM,S power out let.Does this mean the cable is correct :?: CHEERS TINKERA. PS Don,t want to be a pest thanks in advance.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: fridge or battery

Hi Tinkera, if your battery is fully charged then the voltage readings don’t indicate too much info.

Try putting your fridge or some other load on the auxiliary battery and see how much of a voltage drop you get then.

When it comes to checking voltage drop for a dual battery system, it’s best if this can be done when the auxiliary battery is low if you can get both the voltage and the current, you will get a very accurate idea of how well a system is going to work ( or not )

As to the cable, measure the diameter of the copper cable or of you can’t access the copper itself, just measure the diameter including the insulation and we should be able to give you a fair idea of what size cable you have.

Now as to being a pest. No such thing, these forums are for people like yourself, who want info and feedback to be able to do what you want and hopefully get the best results in doing so.

[tinkera Member Find all posts View Profile Close tinkera]

Re: fridge or battery

HI drivesafe thanks again the cable with insulation is about 5mm dia with the markings =0358m= on it it,s double flex CHEERS TINKERA.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: fridge or battery

Hi again tinkera, 6mm Auto is about 4mm, 6mm2 or 6mm Marine is about 5mm and 8B&S ( 7.9mm2 ) is about 5.5mm.

Can you tell me how long the cable run is from your cranking battery ( via your isolator ) to your auxiliary battery is?

[tinkera Member Find all posts View Profile Close tinkera]

Re: fridge or battery

HI Yeah suposed I should have surplied that ops: Yeah it,s about 3.8mts TINKERA.

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: fridge or battery

Thanks tinkera, if that’s the length and I’m assuming your battery is somewhere other than the engine bay, which is a good move for AGM type batteries, then if your cable is 8B&S, it really is at the borderline for the cable size needed.

If the cable is thinner than 8B&S, then while it will still charge the battery, if you ever decide to do some work on your electrics, try running 6B&S ( 13.5mm2 ) and see how much quicker you battery will change.

One more question and I should have asked this earlier, have you run both positive and negative cables to your auxiliary battery?

[tinkera Member Find all posts View Profile Close tinkera]

Re: fridge or battery

HI again yes I am running 2 MARATHON M12V90F AGM,S. in the cabin behind 2nd row seats .When I bought the cable to wire it the guy said use the double flex as he says he always runs neg from front to back so I did the same. CHEERS TINKERA

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: fridge or battery

well i plugged the fridge in again today to use it what do ya know it dont work again :evil: :evil: :evil: , all i get is an er2 message on the temp display, wont work on 12v or 240v so a quick google search turns up another fella who had the same problem and it turned out to be a thermistor, so its back again to waeco agent, wonder how it would go at gettin a new fridge off waeco this is starting to piss me off, i will keep ya posted. cheers samo

[tinkera Member Find all posts View Profile Close tinkera]

Re: fridge or battery

HI Samo.I think you,ve got good reason to be pissed and should get a replacement for sure BTW how old is it. :?: As I posted before the refridge guy I deal with is of this brand because of these sorts of issues ,randon faults showing up after bench testing ok.People coming back going crazy at him because trip was ruined as well as food.Like he says he can,t test for intermittent faults thats impossible.I hope you have some luck with the dealer. CHEERS TINKERA.

[samo Addicted PP Member Find all posts View Profile Close samo]

Re: fridge or battery

hey tinkera the fridge is only less than 2 years old, its under warranty and been back, this will be its 3rd trip to the waeco agent in 4 months, i will see what happens for a new 1 as its a version a and they dont make em any more, but as i said its giving me the shits, maybe i should have bought an, well i cant say it yet. cheers samo

[jarrah7rally Member Find all posts View Profile Close jarrah7rally]

Re: fridge or battery

As this post is so similar to my situation might as well add to it :

To give the scenario sent the folks away with the Prado for Easter long weekend. Upon return they complained about the dual battery system, auxiliary battery isn't charging - mmm Ok I said, and started thinking about it long & hard.

I asked what they did to get charge back into the battery oh we ran a wire between the main (start) battery & auxiliary battery and charged it whilst we were driving around abit (maybe 15-20 kms in one or two days) apart from this distance the fridge was in freeze mode the whole time - was powered @ home by mains until just prior to the trip.

Did some testing and discovered a blown fuse (suspect they blew it) when they connected the auxiliary battery in parallel to charge it, but now I have to ascertain what is causing the battery to drop voltage to low. I by passed the fuse holder on advice from auto sparkie (getting fuses are difficult being National Luna system.

data useful to know

National Luna dual battery kits DIY kit cables 6MM2 from memory -don't qoute me

Fridge engel 4amp maximum draw tested this on Sunday using a digital Multimeter 3 amp -old unit purchased around 1982-84 era - still younger than me I might add :roll:

Battery Amaron green top 12v80ah

Voltage whilst engine running 13.6 volts - after by passing fuse holder

Connected fridge up overnight on freeze mode

Voltage this morning 11.81 - 40% according to battery monitor

12.74 after driving to work 40 odd kms 3/4 hour drive

So begs the question with the fridge connected overnight will this overload the system, I suspect it is and with a 3 week trip up north soon don't want further issues whilst I am away.

Any info appreciated

Cheers

Dean

[drivesafe Senior Member Find all posts View Profile Close drivesafe]

Re: fridge or battery

Hi Dean, at 11.81v, your battery is actually closer to 30% SoC and at that level, it would have only taken about 15 hours, at the longest, to discharge an 80 Ah battery down to that level and this is only if your battery was fully 100% charged when you started and the maximum current draw from your fridge was exactly 3 amp.

If either your fridge’s current draw was just a little higher an/or the battery was anything but 100% charged, you are more realistically looking at about 10 hours to discharge your battery down to that level.

You say you had 12.74v at the battery after a 40 minute drive. Unfortunately, you need to apply a small load to the battery for about 10 minutes before you can get a more accurate voltage reading from your battery.

The problem is that when a battery is charged, no matter whether it be by a battery charger or an alternator, when you remove the charging source, the battery will have what is known as a surface charge.

You need to “BURN” this surface charge off before you can get anywhere near an accurate indication of the SoC of the battery.

A simple way to “BURN OFF” this surface charge, without putting to much of a load on the battery, is to get a small wattage automotive globe, say about 10w and connect it to the battery for 10 to 20 minutes and then, with the globe still connect, take a voltage reading.

In your case, your battery was probably only about 12.3v ( That’s a very rough guess ).

Next, if the cable is 6mm2, unless your auxiliary and cranking batteries are mounted side, that size cable is just way to thin and while you can still fully charge the auxiliary battery, it would take a hell of a lot of hours of driving time to do it and if the fridge is connect and running it would take even longer.

If your not sure of what the actual size of the cable is, measure the diameter of the cable, including it’s plastic insulation and post it up. Soon give you an idea of what it is.