Another 2nd battery bites the dust.

Hi, there are a few things you need to consider
1) do you have all batteries in series after the charger? What I mean is that your charger needs to be rated to charge the battery load you have. Eg. if you are charging 2x 200Ah batteries, it needs to be rated to 400Ah
2) Are you using identical batteries after the charger
3) considering using cascading charge .. this is what I would strongly recommend.

What I mean by this (and in my example I will use selenoids):

Your main battery is connected to selenoid 1 (for aux battery 1). The selenoid will let power pass to aux1 once main battery is fully charged.

A second selenoid (for aux battery 2) is connect to aux 1 and will start charging aux 2, once aux 1 is full

and so on.

The benefit of cascading charging is that you will get sooner a full battery. Meaning that charging will also faster.

Keep in mind that most appliences really work if the battery is charged > 12.06 V. If you are using all your power to charge aux1 and aux2 at the same time, and assuming that both are empty it will take you somewhere between 2-3 x longer to get into the 25% (12.06V) range.

Another benefit of isolating batteries is that if one breaks, you still can use the good one and the bad one will drain your good one.

Always make sure that you charge the main battery (usually a crank battery) seperatly from the aux batteries (usually deep cycle).

It is important to have identical batteries when you are charging in line because every battery has a different charging attributes.

Before introducing a new battery into the system make sure you have the old aux battery and the new battery fully charged seperatly. Don't put them in line and start charging. Before putting them together compare the voltage in full state (after letting it cool down for about 30 mins after fully charged).

Make sure that you charge the batteries isolated once every month with a good charger (eg CTek). The difference between charging with an alternator and charging with a good battery charger is that the alternator will more or less deliver a constant 14V something, while the battery charger will apply different voltage at different stages.

There are 'battery chargers' out there which just push out constant 14V. They are no good (well they work).

With the above isolators become important.

Hope this helps a little bit.
Regards,
Dante

Ok thanks Drive safe.

First of all I think we should forget about the extra batties in the trailer and just concentrate on the 2 in the car. I only say this because this problem with destroying batteries quickly existed a long time before I had the trailer.
I also always fully charge the trailer batteries with this charger http://www.sidewinder.com.au/product5.html the 15A unit.

1. Will do all the measurments of voltage today, although how far do you think you should have to travel before measuring voltage?

2. Using 10mm cable

3. No. I know I am bad and I have been meaning to run an earth from front to rear battery but have not done it yet. Rear battery is earthed to chasis.

4. Step-up charger....by this you mean the Arrid?? It was the 25A version. But it is not connected anymore.

5. So far I have only been doing base camping with the trailer. When we get to the campsite, I unhook the trailer and then do not hook it up again until we go home. We still do day drives in the Disco but the 2 big batteries in the trailer are never hooked up to the car until it is time to go home.


Hope that is enough.

I am still thinking it is the output voltage from the Alternator. And the Step -up chatger was just keeping things alive.


Thanks for the help

OK these are just suggestions at this time as you need to get your voltage measurements first so I can see better where the problem might be.

As far as using the chassis goes, this may be fine but the problem is and no matter how good it may look, there is no way of determining if the chassis is a good earth return when under load, like when trying to recharge a battery.

For starters, forget the step-up charger, anything less than a 50 amp step-up charger is a waste of time as your alternator can do it quicker.

If I were you Adam, get your hands on some 4G cable, positive and NEGATIVE and run the new cable to your rear battery. If you want to leave the earth straps in place, do so as there is no problem trying to improve the set-up.

The increased cable size will probably remove most of your problems but do your measurements first.

By the way, I was being a smart ass as I already knew you only had one cable to your rear battery from a post you did many moons ago.

Get your readings and we can go from there.

Cheers

As a reminder, the chassis on my D2 (not assuming earlier ones were built the same way) was not earthed until I installed driving lights and winch all with their own earth leads from the body or battery.

Quote:

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Originally Posted by Graeme

As a reminder, the chassis on my D2 (not assuming earlier ones were built the same way) was not earthed until I installed driving lights and winch all with their own earth leads from the body or battery.

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This might be a stupid question, but did you scratch away the paint before putting fasteners down?

Quote:

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Originally Posted by Dante

This might be a stupid question, but did you scratch away the paint before putting fasteners down?

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No, not particularly, although the bolt heads and spring washers would probably have bitten through any paint. I was not trying to earth the chassis and have nothing that relies on the chassis being earthed.

Graeme, is right. I don't think the chasis is properly earthed with an earth strap on the D2 like it is on the Rangie Classic and D1.

Now what size is 4G cable? Being a sparky I work in mm2. All cable and fitting I buy from my local auto elec, not from supercheap or autobarn. I am pretty sure the cable I bought which runs between the batteries was rated at 120A as I remember he worked out what size I should use for the 4.5m run. Can I at least see what voltage I am getting at the far end of the cable before I replace it?
But I do agree with you on the negative. I will put a cable in as that way at least it eliminates at least 1 potential problem. (nice electrical pun there)


I took a couple of initial readings today on voltage, but I really need to disconnect the rear battery before I can get accurate readings.

On start-up I had 14.56v at alternator
After 30 min drive I had 13.98v at alternator and 13.96v at main battery and 8.51v at rear battery.

Rear battery is obviously stuffed, although I would have thought I would have the same voltage as the front battery if the battery controller was linking the batteries.

It will have to wait till Wednesday when I will have time to remove the rear battery and see if controller is working.

Hi Adam, 4G or 4AWG or 4B&S are all the same size and are usually available from auto elecs but the square mm size is 21mm2.

This is fairly thick cable but it will allow you to charge the rear battery and the trailer batteries without too much of a voltage drop.

If you are only going to be charging the rear battery then you could get away with 6B&S, which is 13.5mm2.

Next where have you got the SC80 mounted. I remeber your old controller was mounted in the rear near the rear battery.

If the SC80 is up front then that sort of voltage drop, even with a stuffed battery can only be down to too small a cable and/or a bad earth and at a guess is the reason for the stuffed battery, it was never getting charged properly.

A bit of advice on cable amp rating, this is not the working current that is going to be travelling down the cable, this is the maximum current the cable can handle before the insulation starts to melt.

This may sound like double dutch but the actual current that will be carried is based on a number of factors and the thickness of the cable is only one, the supply voltage ( alternator voltage ) is another, the load at the other end is one more but the length of the cable is probably the most important factor in a high current 12 volt circuit and remember that the length of cable will be 4.5m x 2, positive and negative.

Once you disconnect the rear battery, and you only need to disconnect one terminal to get a reading, for safety reasons make sure it’s only the negative terminal. With the negative terminal disconnected, you should get a voltage reading at the rear battery’s positive terminal that is the same as the reading you will get at the cranking battery’s positive terminal after you have disconnected the rear battery’s neg terminal.

I wouldn’t be surprised if all the voltage readings rise after you disconnect the rear battery.

Cheers.

Adam, i have the same setup as you, minus 1 battery, i only have 1 battery in the camper and a second in the car, i also run the Arrid Twin charger in the trailer powered via an Anderson plug from the (and here's where mine changes) main battery via the ignition, NOT from the second battery.

I keep my second battery in the car seperate and controlled by my Traxide SC-40 and so far without problems.

My suggestion would be to try it my way run the Arrid in the trailer to the main battery via the ignition, this way it could tell if it's the alternater that's the problem and it won't cost anything to try, or you could take it to an auto elec.

Oh and get another battery other than the Blue top, maybe a Trojon, Fullriver or Supercharge AGM Deepcycle ONLY.

Just a thought.

Baz.

Quote:

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Originally Posted by drivesafe

Hi Adam, 4G or 4AWG or 4B&S are all the same size and are usually available from auto elecs but the square mm size is 21mm2.

This is fairly thick cable but it will allow you to charge the rear battery and the trailer batteries without too much of a voltage drop.

If you are only going to be charging the rear battery then you could get away with 6B&S, which is 13.5mm2.

Next where have you got the SC80 mounted. I remeber your old controller was mounted in the rear near the rear battery.

If the SC80 is up front then that sort of voltage drop, even with a stuffed battery can only be down to too small a cable and/or a bad earth and at a guess is the reason for the stuffed battery, it was never getting charged properly.

A bit of advice on cable amp rating, this is not the working current that is going to be travelling down the cable, this is the maximum current the cable can handle before the insulation starts to melt.

This may sound like double dutch but the actual current that will be carried is based on a number of factors and the thickness of the cable is only one, the supply voltage ( alternator voltage ) is another, the load at the other end is one more but the length of the cable is probably the most important factor in a high current 12 volt circuit and remember that the length of cable will be 4.5m x 2, positive and negative.

Once you disconnect the rear battery, and you only need to disconnect one terminal to get a reading, for safety reasons make sure it’s only the negative terminal. With the negative terminal disconnected, you should get a voltage reading at the rear battery’s positive terminal that is the same as the reading you will get at the cranking battery’s positive terminal after you have disconnected the rear battery’s neg terminal.

I wouldn’t be surprised if all the voltage readings rise after you disconnect the rear battery.

Cheers.

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I'm using sparky wire to as i'm one. i'm using 35 square mm from main to 120a relay then to 2nd battery never had a problem with it