Disco 2 Replacing the air compressor with something more useful?

mad85 said:

The idea that i will only use the 2000w very rarely if I need to run a powertool. Normally i will use the inverter for something much smaller like a fridge or a laptop charger.

As someone mentioned cables from the battery to the inverter need to be much thicker than cables from the inveter to the appliance

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You would be better running a battery charger if the investor and using battery power tools, then you won’t need such a large inverter

Si Click said:

Good. Thank you, I thought I was not going mad.
"The DC amperage will be a lot lower than the AC as the voltage is a lot higher." made no sense at all.
I still think that draws of 100-200 amps is unsustainable on any off-charge lead acid or AGM 12V system without frequently killing the battery. Lead crystal or Lithium batteries might survive longer and give power for longer, but you are still talking minutes rather than hours to flat.

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Sorry,what I meant to say was "the DC amps will be a lot higher as the AC voltage is a lot higher". It was 6:30 in the morning but the rest of the statement is true - running the DC cables a longer route to the inverter is a bad idea.

so, sometime ago I had suggested a battery rather in the space taken by the now useless compressor ... so i went ahead and installed one...

I had to make a new mounting shelf which is tougher and wider which would accommodate my 80amp AGM battery from my old freelander 2. The battery is still in good condition but is not new and not good enough to run the freelander... obviously i wanted to test this system with an old battery before investing in another battery haha:



I have passed new cables in 50mm2 tot he boot area and connected the earth to the body through the body mount next to the battery. The battery will power a 1000W inverter, a fridge, various small led lights, some usb connectors and a water pump. To charge it, I am using a CTEK DC-to-DC charger which can take power from the l alternator but also from a roof mounted solar panel. I am doing a little panel to be mounted the boot, near the window:



When ready everything will be properly fused obviously with various cut off switches for different functions.

In terms of battery location, I have never hit the compressor in a hard way and was still in good condition, but in order to protect the battery i have designed a new guard made from 5mm steel which is bolted to the chassis and to the sliders:




I m pretty pleased with it so far, although i wont exclude the possibility that it gets f***ed in the future though haha... I do a lot of trails so I will be testing it in the coming weeks. If i see that it wont last i will go ahead and relocate to the boot area but I am looking forward to give this a try! Hope this is interesting fro someone

What stops it bouncing up and shorting on the panel above it?

good question obviously there is a mounting plate which is fixed by two bolts, one on each side. I have used 5mm rubber between this mounting plate and the battery and also between the battery and the body to that is it well insulated. The picture I have added was of when I was checking that the battery fits well.

oh, im also preparing a cover made from abs plastic (used to be a mixing tub) that should shield the battery from too much mud, much like the original dust cover on the compressor

mad85 said:

good question obviously there is a mounting plate which is fixed by two bolts, one on each side. I have used 5mm rubber between this mounting plate and the battery and also between the battery and the body to that is it well insulated. The picture I have added was of when I was checking that the battery fits well.

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Sets one's mind at rest. Was wondering if you had some kind of a plate or strap going over it secured at the bottom, but if there is the plastic ir rubber tub thing over it, that should do. Are you thinking of a jelly battery in the end as a normal one might send liquid out which might get you in trouble with a fussy MOT inspector or summat. Mind you I think you will need a sealed job as topping it up would be a pain!

yes, currently using agm, if it needs replacing, it will probably be another agm or a deep cycle one.

mad85 said:

yes, currently using agm, if it needs replacing, it will probably be another agm or a deep cycle one.

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Given the mounting orientation, avoid Flooded Lead Acid and stick with AGM or Gel

NPG said:

Given the mounting orientation, avoid Flooded Lead Acid and stick with AGM or Gel

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yes several advantages to using agm as a leisure battery, including ability to deep cycle, completely sealed and of course can be mounted sideways without issues.

You have a good setup there and power losses should be negligible, around 0.1W on the A/C and 25W on the DC @ 1kW. I don't know how things are wired exactly or if the CTEK charger provides automatic isolation but if not, I would consider a manual switch or even, a solenoid wired to the ignition that would disconnect the second battery from the charging circuit when the ignition is turned off. Well done.

thanks, yes the CTEK charger is a complete system and will also act as a cut off when ignition is off. The only time when I need to disconnect it or use an isolation switch is if I need to charge the starter battery. In that case the dc-to-dc charger will realise that the starter battery is charging and will start charging the second battery.

mad85 said:

The only time when I need to disconnect it or use an isolation switch is if I need to charge the starter battery. In that case the dc-to-dc charger will realise that the starter battery is charging and will start charging the second battery.

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The CTEK will probably wait for the SoC of the primary battery to be high enough before supplying current to the second battery. At which point it will start draining the primary battery slowly which would in turn cause the alternator's regulator to react and start supplying a charging current to the starter battery, in the belief that it is connected to a single battery. Like I said, I don't know how the CTEK works internally but if this is the case, you might be able to charge both batteries with an external smart charger if you leave the second battery connected.

And I can't help noticing how rust-free the underside of your vehicle is, probably thanks to the sunny weather in Malta

NPG said:

The CTEK will probably wait for the SoC of the primary battery to be high enough before supplying current to the second battery. At which point it will start draining the primary battery slowly which would in turn cause the alternator's regulator to react and start supplying a charging current to the starter battery, in the belief that it is connected to a single battery. Like I said, I don't know how the CTEK works internally but if this is the case, you might be able to charge both batteries with an external smart charger if you leave the second battery connected.

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Yes, the CTEK will detect the increase in voltage and starts to charge the second battery. In order to charge both batteries, the smart charger needs to be able to charge at a higher rate than the 20A the CTEK can charge the second battery at... in my case, my smart charger is less than that. So if i do not disconnect them, it will drain my starter battery if the second battery is not full.

NPG said:

And I can't help noticing how rust-free the underside of your vehicle is, probably thanks to the sunny weather in Malta

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Haha thanks, my car was actually imported from the UK a few years ago but when I bought it the first thing I did was to soda blast the underside to see what damage there was. Luckily it was only a little surface rust so it was only a matter of applying some good paint and making sure I replace any i scuff off while on trails. I also make it a point to wash it every time we go to the seaside, which is about every week year round