Battery question

Not sure if this is in the right place but here goes

Right the battery on my 2.2 Frontera is knackered so I need to replace it now the truck was brought with a mind to go further afield a little bit of overland treking next year.

Now the big question is do I replace it with a like for like battery I think it's a 65 amphr or go larger 85 or 110 one off or go small starter battery and a deep cycle leisure with a dual charging system.

Next question what sort of money could I be looking at ?

The main reason is I'm looking to get a small 12v fridge for the longer treks.

Go for a starter (like for like) and add a 110ah leisure battery as used in caravans and you can decide how much you want to spend on a charging system. If your alternator is doing a good job you can simply install a switch to isolate you leisure for when you need it most or switch to charge it or there are systems that control the charge and use of both batteries.
A std starter battery does not like being discharged too heavily hence the benefit of the leisure battery which will take multiple deep discharging.
There is a post on understanding batteries and the uses and capabilities.

I second that - go for a 2nd battery , switch or even a charge relay are not expensive to do a budget split charge system

Run anything to do with camping off the 2nd battery - even wire the cd/radio to it if you are going to use that in the evening. What sort of fridge are you looking at cos they are the expensive bit.

It all protects the ability to start the truck

Rich

Definately second battery, always keep the vehicle battery seperate.

One piece of advice I would offer is to get a multimeter, or borrow one, and measure the power consumed by the fridge. Tested many several years ago and they can consume considerably more power than the manufacturers figures which are measured in ideal conditions in a laboratory. This will give you real world figures to ascertain your battery requirement for the life or working time you need.

Personally I prefer the digital all singing and dancing split charging systems which have come down in price considerably, these will have several switched modes which will bring back the most discharged batteries, have anti-sulphating capability, and fully optimise the charging of your second battery and maintain it at optimum charge.

I will explain now my phone call has ended.

Basic systems consist of a high power switch and two wires between two batteries mounted close to each other. Many problems arise, you have to switch off before starting the vehicle and back on once the vehicle is running, this is inconvenient and can lead to problems. Forget to switch off before starting and you can damage the aux battery through starting, forget to switch on and the aux battery won't charge. If you switch on and leave it on once the vehicle has stopped you will discharge both batteries potentially.
With two batteries in parallel, of different capacities you will find one may overcharge (smallest capacity) and the largest battery may undercharge.

Blocking diode systems are just that, a diode; a diode only allows current to flow one way, but they have a volt drop across them of around 0.8-103 volts and this often prevents the aux battery from fully charging due to this volt drop as all car charging systems are machine sensed, basically the alternator senses the output and not the battery.

Basic split charging circuits consist of a basic high power relay, this is connected to the main battery and the aux battery, and the other terminals are connected to earth, and one is used to switch the relay on and off. This is achieved by using the feed wire back to the charging light as this switches on at a pre-determined voltage and not current output from the alternator. These are better, but basic, and suffer the same afflictions as the above, they cannot control the charge from the alternator and may overcharge one battery and undercharge another.

Voltage sensed systems are similar in principle to the basic split charge relay, but only work by using their voltage sensing capability, this is achieved by using high power MOFSET's, they can sense both the main and aux batteries power and split the charge according to how much charging each battery actually needs. Basically it biases charge to the main battery and when this hits a pre-determined voltage (generally around 13.2 - 13.5 volts) it switches charge to the aux battery as well as the main engine battery, thus splitting the charge on demand of each batteries requirement so no under/overcharging occurs.

Voltage sensed systems are the one to go for, quality systems from reputable manufacturers are readily available from £50-80 and are easily DIY fitted, many have optional display panels which give the state of charge of each individual battery, the charge rate of each individual battery, and some are programmable with a multitude of functions, and most have the option of LCD screens for even more display information.

Thanks all a voltage sensing system seem to be the one to go for.

Physically the standard battery tray will take a second battery as the standard 65ah is quite small.
I have one of those small 12v cold box things which I have used for a good few years which draws an amazing amount of current which is fine when traveling all day and turned off at night but leave it on dusk till dawn and the standard battery is flat as a pancake and may only just start the truck or it's jump leads not ideal.

As for a new fridge not sure what to go for most of the ones ive looked at at shows seem quite large and as its only really for a few beers, milk, a small amount of fresh meat and marg I think 30-35 litres would be big enough.
It doesn't need to be huge as I read in one of the magazines, milk comes in powder and meat comes in tins but it's nice to have fresh stuff even if it's only every other day.

If I could make another suggestion:

When I fit such systems I try to mount them on a plate next to the aux battery, if you swap vehicles or buy another vehicle all you need to do is disconnect the two wires from the engine battery and unbolt the plate to install in a second vehicle. If possible mount the system on an aluminium plate so it transfers heat from the unit more efficiently, and ensure it is electrically isolated where you bolt it to your vehicle to prevent electrolytic reaction between the aluminium and steel to stop your vehicle body rotting.