Second Battery Fault

[Wombat1]

Once again the debate over Diodes and DC-DC charger goes on.

I would suggest you get the second battery tested. Places like Battery World or even better still a good Auto Electrician will have the equipment to test the battery. (SOC,AMPS V's etc - When Loaded and Unloaded) If you go to an Auto Elecky get them to check the charger for the amp output and the volt output it is putting into the battery. Most good Auto Electricians will not charge you to do this, however might try to sell you one of their batteries if your battery is stuffed.

Standard alternators will only ever get your battery/s to only 80 to 90% of capacity (at best) and the best suggestion is to get a good multi stage charger to charge both batteries at least once a month.

As for your fridge there are a lot of factors to consider when it is running e.g. ambient temp, size of cabling to the 2nd battery, how hard it is running etc. All these factors will all effect the efficiency of the fridge and thus the time you will get out of your battery.

Personally I would go for best of all worlds, Diode, DC to DC charger and good multi stage charger. If you are eager there are some DC to DC devices that will also allow for Solar Charging Inputs and add extra security whilst away on your trips. (Redarc and Ctek) However bear in mind solar is dependant on daytime hours and other contributing factors.

I hope this assists a little and I hope this steers you in some direction, remembering to get the battery you currently have tested.

[sandman]

a. the fridge draws more than the suggested 2 amps b. the battery is stuffed or c. the dual battery system doesn't work well enough. The dual battery system is one ive never heard of its called "megatronics". Any suggestions would be appreciated. Cheers

a) You can put a multimeter inline and check the current to make sure the fridge doesn't have a fault. A 40amp fridge "should" be able to run for 2 days at a reasonable duty cycle when parked of course it will depend on how hot it is inside the car. I'm not sure as to what the lower battery voltage you should let the thing drop to before you need to disconnect however personally if the thing was heading lower than say 12V I'd disconnect, maybe its 11 but if you're into the 10v areana then there is a problem, its flat.

b) Battery could be stuffed as its not really holding its charge. Seriously if the thing is over 2 years old consider replacing it. I know there are folks that claim 5++ years out of their 2nd battery but I live in Alice Springs and lots of friends have 2nd batteries, tried AGM and the likes.....2 years.....

Oh one more thing, don't check the 2nd battery the night before your 3 week outback adventure, by then its all a little too late :-)

c) Everyone has an opinion on these ie: solenoid type, smart charging and dc-dc chargers. I had a redarc relay in mine and after the 2nd battery died after 3 years I went to a DC-DC charger. Its clear that the PRADO electronics dont provide the 14.5v you need for absorption, that's where the diode comes in to fool the incar electronics to drive the alternator voltage higher. Apparently people swear by them and it sounds like a simple idea. I shoved a dc-dc charger into teh engine compartment and I fully understand that after 55c things tend to fold back current wise, after chattign to Redarc we both agreed to see how it goes as an experiment. I have an air pipe from the front that funnels air up to the unit and that all works fine....

2nd batteries are a little like black magic, you can get onto a winning formula and when you win, stick with what you know. many others me included change batteries out every 2nd year and religiously charge them every 6 weeks....problem with extreme conditions out here in the NT, it tends to break things a lot quicker...thats why i drive a Prado :-)

[sandman]

I have a 2nd battery in my 2004 Prado. I have and have had deep cycle batteries in the thing, the latest I've tried is a marine battery to take the battering of corrugated roads. I've found I get 2 years out of my 2nd batteries no matter how nice I treat them. The last battery died 2 months ago after 22 months (had a 24 month warranty) so it was replaced free of charge.

I would HIGHLY recommend putting it on a battery charger every 4-6 weeks to top it up no matter how good your in car charger was. Last trip we did from Home (Alice Springs) through the Tanami to Broome and back, I took the 240v charger and popped it on when we had a powered site in Derby.

To make charging the battery a simple experience, I have a 50amp Anderson on the front bar that is on the 2nd battery. I've made up a short lead that the charger clips onto so I dont even have to lift the bonnet to charge when at home. if its easy you'll do it, if its a chore you will forget :-)

Pete

[peril]

I use one of these

http://www.powerwerx.com/digital-met...owerpoles.html


Michael

Alternate supplier @ $23.95 plus post, this is the original Turnigy brand retailer based in China.


http://www.hobbyking.com/hobbyking/s...dProduct=10080

[D4D]

The OP has described a situation that points to a stuffed battery.

Yup D4D's eat aux batteries, 2 years is about the right lifetime, Throw the battery away and get a new one, fit one of Leigh's V boosters, replace the 'megatronics' with a redarc or similar and give it a 240V charge once a month.

[Heath74]

Easy boys, lets just leave DCDC out of this for the moment. The OP has described a situation that points to a stuffed battery.

There are several reasons why it may be stuffed. Before he rebuilds his charging system, How old is the aux battery?

[D4D]

... but the theory is sound.

Unless the device is fitted under a bonnet

[peril]

OH I didn't suggest NOT to run a diode, presumption there me thinks, perhaps run both and all you can to help. Just pointing out the benifits from a correctly functioning DC-DC charger. Perhaps the industry still hasn't caught up with my imagination, but the theory is sound.

[D4D]

Yep lot's of hype about DC-DC chargers, installed under the bonnet they don't deliver. Even the install instructions suggest they won't put out full A or V above 55 degrees celcius.

[mjrandom]

Guys no need to start the diode vs DCDC charger debate here. OP post what is written on your aux battery so we can see what you are trying to charge. And any specs on the charger.

[peril]

The is some merit in the DC-DC chargers, I went looking for a system like this 10 years ago, but industry had not caught up with my imagination back then.

The DC-DC chargers can whack high current fast charge from a low current source. It boosts the voltage to +15v and thus can make the most potential out of your battery limited storage system. Normal car alternators will 'never' charge a battery to it's full potential as the voltage is just not high enough to reach a fully charged state, leaving most batteries only 90%, or even less.

If you run a high charge DC-DC charger you can charge your battery fully, making more from your limited space.

Plus you can charge a LOT faster than any generator (unless you have a special fast charge one)

Used in conjuction with a solar pannel system when the sun is shining and you can almost throw your genny away

[D4D]

While the "diode" trick does work I think you just cant go past a DC-DC charger....

Perfect if you're prepared to wait all day with your diesel genny running to charge your batteries...

[sandman]

While the "diode" trick does work I think you just cant go past a DC-DC charger....

[mjrandom]

I use one of these

http://www.powerwerx.com/digital-met...owerpoles.html

To keep an eye on current draw from the fridge. 13.5V worries me a bit if that is the reading with engine off and battery settled for a few hours. Most I have seen with a full battery is about 13V. Can you trust your multimeter? Andrew as usual is correct, best way to test is to charge with an AC smart charger then load it up until it drops to whatever the manufacturer says is the minimum voltage (this varies so google battery make and model).

This is from ABR Sidewinder's site and gives you an idea of state of charge

http://www.sidewinder.com.au/page167aaaa.html

Likely the battery manufacturer won't be happy if the battery drops below 12.2V. About 50% charge, so 55AH in your case. Fridge at 0C should run 2 full days at the moment. Less than that and the battery is on the way out. If you get the meter you can see exactly how many AH have been delivered.

Let the battery settle without charge or load for an hour or two then check voltages at each outlet and then with the fridge running.

Is the battery an AGM? I guess it is and you will need a booster diode to bump the alternator output to get a full charge.

I will drop a couple of threads here that will give you some more info when I get home, otherwise search PradoPoint+voltage+booster in google bad also Redarc isolator. Lots of good words. Is yours a D4D as well?

Michael

[Greenie]

I tend to agree with mjrandom in regards to the fridge drawing 4 amps while running. The current draw will increase as the battery voltage decreases and this is why volt drop can become an issue. My 40l engel in my rig will run for about 14 hrs in 40c weather until the batt (120AH) drops down to about 12.9v which is about as low as I generally let it go (have to look after these expensive batteries!!)

Greenie