Novice needs help with battery problems!

Other than the voltage reading Liam there is nothing that I know of that will tell you how much charge is left in a battery. You could get it tested with a battery tester, which puts it under drain for a short perios and indicates its health but not its state of chargedness.

Even the voltage is a poor indicator of the battery's amount of charge left.

I would be using a battery charger to charge it rather than driving around trying to charge it, one with am ammeter in the charger so you can see the level of charge the battery is taking.

If you're having trouble charging in the van when driving re-check all your connections its seems like you've got a dry connection somewhere and the charge isn't getting thru, or check the voltage of the alternator when its running at fast idle, you should have around 13.8 to 14.2 volts.

The engel, although you haven't mentioned the size, should run for a couple days off a fully charged battery and you dont mention what you mean about lights but it should do 2-3 hrs of the 12v fluoro light at nite no trouble along with the fridge.

Good luck

Liam


Buy yourself a Multimeter. About $20 or less from Dick Smith or alike.

Either your alternator isn't charrging properly or your battery is stuffed


Cheers

I always thought two way fridges used a heater element. If this is the case then you should be using the gas alternative. The Engel I am familiar with uses a compressor and much less energy.

The best way to check for remaining charge is to use a specific gravity (hydrometer?) Voltage is a good indicator but can lead to false expectations. you can buy one for a couple of dollars these days.

If the battery is on the way out you can get it to read full voltage after a charge but the capacity will be way down.

If the car is sending a charge to the battery you will get 13.8 volts on the system with the motor running.

Please correct me if I am wrong on any of these points.

Owen

An engel fridge is going to be drawing anywhere from approx. 2.5 amps up to 3.5 amps when running (the newer models are more effecient whilst the older models use the higher end)

So lets use an average of 3 ah for a rough estimate. In a 24 hour period in temperatures of say 30degC maybe running 70% of the time (as a fridge not a freezer) 3ah X 24 hours x 70% = 50ah

In actual fact these figures are probably at the high end of the use so in reality you may only use 30ah ( 2.5 X 24 X 50% = 30ah)

Without knowing the capacity of your battery the question cannot be answered but if you can find out your battery details you can use the abve for your own calcuations.

If you had a deep cycle battery of 100ah capacity then without taking the battery below 30% you should get (using the above figures) 1.4 days (at 50 ah in 24) or 2.3 days respectively. If you have a cranking battery as the fridge then you have the wrong battery type for prolonged use as an accessory battery.

As for the battery SOC as other members have stated battery voltage is an indication of SOC only. If you put a multi meter on the battery whilst the engine is running and you get a reading around 13.8 volts (or approaching this) then the second battery is getting a charge but as to how much you wont have a clue without a measurement of amps going in

If there is a dry joint or incorrect cable size to the second battery then it will only be receiving a trickle charge as against the alternators capacity to charge and you may never recoverer the second batteries charge from low down.

Liken it to water out of a garden hose...small hose = reduced flow of water. Larger diameter hose = greater flow of water (less volt drop and increased amp flow)

usually if your battery runs down quickly and is hard to re charge it is stuffed

any auto electric place should check how much charge your battery is getting as well as load testing your battery (probabally the best way to check a batterys health) for free or small charge

- unfortunatly for you it is Easter

my money would be on
70% stuffed battery
20% stuffed alternator
10% other problem such as wiring

get it to a sparky for not much you can quickly better isolate your issue

Liam,
How old is this "large marine/rv battery" ?

I will suggest the battery is beyond it's useby date!
The easy thing is to take it to a battery retailer and have it checked out as suggested above.

Mainey . . .

Ithink Bungarra gave a very accurate description of what takes place and how much current draw the fridge is using. The only thing I would add to that is remember a full deep cycle battery takes a fair bit longer to recharge than a cranking battery, so it is not advisable to run the battery "flat".It also is a great help if you know the condition of the battery and how many amp/hours it is.

Hi,

Thanks for the replies guys, that gives me some more info to work from! The battery I have is a 73Amp/hr battery and I assume it's an older model Engel so I'd get less than 24hrs before the battery would be at 50% charge - that's if it was good in the first place!

There is a battery charging unit in the van called a LEAB, little white box which runs when I'm connected to mains power or a generator... (read on)

I'm in Kalbarri so options are limited but I did buy a small external 850W generator and a battery charger (a pretty basic one I hadn't heard of a 3 stage battery charger at the time - what is it exactly?). The charger I got has a high charge and a trickle charge facility and it shows what amps the battery is drawing as it is charging. It claims it will fully charge a "normal" car battery from flat in 2.5 hours on the high setting and says that it is safe to trickle charge a battery for 7 days.

So here's what I've been doing - I disconnect the aux battery and start my generator. There is no draw on the aux now so I hook up the battery charger and put in on the high charge and run it like this for an 2-3 hours over the past few days. Fridge lights etc. are running off the generator during this time. However now I'm worried about a whole heap of other things!

1. Is it safe to recharge a battery this way in the van? Should I take it outside and do I need to open the caps of the battery when charging? Gases etc. etc. there's very poor ventilation, it's under a seat and there's just a 2 inch dia hole in the floor.

2. Am I overcharging the battery? Should I just leave it on trickle instead? I've still no way of knowing when it is full or how close to being full it is. Maybe I should give it an hour of high charge then reconnect the battery (generator still running of course) and let the LEAB finish the job?

Don't know how old it is but in my ignorance I've flattened it twice already myself - nice one ;)

Interestingly I was at a campsite the first night after buying the charger and had mains power so I charged it on high charge over night, when I reconnected the aux in the morning the LEAB unit had a green light on for the first time ever indicating I guess that the battry was full.

Do you think what I'm doing is a good idea and more importantly safe?

I will pick up a multimeter the first chace I get and probably a new battery as well ;-) I turn the fridge off at night now and only run it for a few hours during the day and keep the bluddy door closed - then like I said I disconnect the aux, start my generator and recharge the aux battery off the charger I bought which seems to be more powerful than the LEAB but I wonder about the issues I mentioned above

Liam