Lockdown battery troubles, ideas please

[Ormy]

Due to covid lockdown I'm barely using my car at all. Once per week to drive to the local supermarket which is less than a mile away. Consequently the battery is barely being charged and keeps going flat. Getting the car started when I want to use it is not a problem, I've already bought a jump starter thing (one of these) which I can charge in the house and use to get the car started.

The problem is that the battery is draining so low that it is starting to set the alarm off, sometimes in the middle of the night.

I don't want to be regularly driving around wasting petrol for the sole purpose of charging the battery.

If I could attach a trickle charger that would be problem solved however I do not own a garage or driveway, it would mean trailing wires across a residential street, not a long term solution.

I considered removing the battery each week and bringing it in the house to be charged, but that means the car would be unprotected by the alarm and the dashcam while the battery was inside, not acceptable to me.

My current idea is to buy a second battery, a large deep-cycle caravan battery, charge it in the house and then once charged put it in the car boot and connect it to the car's main battery, this will charge the main battery and keep the car alarm and dashcam running. I would take it out one night per week to charge and then put it back in the boot. I already have thick wiring from the car battery under the bonnet to the boot for my subwoofer/amplifier so wiring would be easy. Main car battery is 60AH so I'm thinking to buy a caravan battery with at least double that.

I'm not too bothered about the cost of a large second battery, a high capacity 12V battery is a useful item to have around for powercuts and emergencies so the general utility would be worth the cost for me.

Has anyone got any other/better ideas?

 

[nvingo]

You can get a solar panel car battery charger - one example on Amazon (there are less expensive ones) that might be all you need.
It only has to overcome the natural drain due to memory/alarm circuits and battery self-discharge.

 

[aVdub]

Solar panel trickle charge should do.

 

[Aerojon]

How old is the current battery..

 

[Delvey]

How old is the current battery..

This

Solar panel trickle charge should do.

And this

 

[Ormy]

Battery is 2yr old AGM (Exide EK600). The car is a 20yr old hot hatch (MG ZR), 1.8L petrol, but I went overkill with an AGM battery and uprated alternator to get longer durations of parking mode recording on the dashcam (Viofo A129 duo) and for the most part it worked.

When I had this exact problem during the first lockdown I bought 60W of solar and a voltage regulator. 2x10W panels are wired in permanently to the battery (with blocking diode to stop the battery discharging through the panels at night) on the parcel shelf and I have an additional 40W panel I can lay on the dash and connect when needed.

60W (combined) is the maximum they put out under absolutely perfect conditions of direct sunlight, averaged across days/nights and cloudy days it was just about enough to overcome the drain of the alarm and dashcam (which together require a constant draw in the region of 5W ish at a guess), it worked great through the summer and then I went back to daily work in October so there was no more issue with battery drain.

Back to working from home in January and now the days are shorter, angle of the sun lower, constant condensation or frost on the window above the panel etc etc the solar panels are not even close to keeping up with the drain long-term.

So I guess I only need a solution that will last till April and then the solar panels will be viable again.

 

[AMc]

Could you power the dashcam independently with a powerbank or similar?
5W seems a lot of static drain but my dashcam only works when the ignition is on so I've never needed to worry about it.

 

[Delvey]

So the dash cam is on permanently?

 

[Ormy]

Yes. The dashcam has a low power parking mode that records time lapse footage constantly at 3 frames per second. Parking mode automatically engages when the ignition is turned off and normal 30fps recording resumes when the ignition it turned on. There is a 11.8v cut-off on the dashcam so that it cannot drain the battery completely.

 

[Aerojon]

Thing is,car batteries(lead acid) don't like being discharged,this will decrease the batteries life as the plates start to sulphate..So anything below 12.4volt..

 

[John7]

He's installed an AGM battery which is not as sensitive to discharge state as convention LA.

 

[John7]

OP, in your situation I think I'd go with the secondary battery to take the strain off the AGM. It's not a particularly high capacity battery for continuously running a camera and alarm system, together with starting the car and powering a high power stereo system!

 

[Ormy]

Thanks for the responses everyone.

I have bought a proper car battery charger (Rohr DFX-150) with a de-sulphating reconditioning feature, along with a 130AH deep-cycle caravan battery (of the lead-calcium type). Combined cost £150-ish.

Once these arrive the new battery will be fully charged overnight and put in the boot to power the car (dashcam and alarm). The main AGM battery will be brought inside and the charger's reconditioning/desulphating function will be used and then the battery given a full charge.

As John7 points out AGM batteries are less sensitive to low states of discharge but the voltage did fall to around 9 or 10 volts at one point last month so I'm hoping the desulphating will restore the majority of its original capacity/lifetime.

The general procedure moving forward will be to leave the main AGM battery in the car at all times and charge it by fully charging the larger capacity caravan battery inside the house then transferring it to the boot to run the car systems and charge the main battery. After 24-48 hours the caravan battery will be returned inside to charge again. This will be repeated once per week until daily usage of the car resumes.

 

[Ormy]

It's not a particularly high capacity battery for ... and powering a high power stereo system!

This is probably not relevant but just to be clear, the power amplifier and its supporting 1Farad power capacitor are both isolated from the battery by a relay when the ignition is off so the self-discharge of the capacitor is not draining the battery. If the system is ever being used without the engine on I turn the volume right down, I never listen loud unless the engine is running so as not to drain the battery. It's not a super loud competition system anyway, the fuse between the battery and the capacitor is 40A, and the amplifier can draw a max instantaneous peak current of 80A from the capacitor. I also have a voltmeter permanently mounted on the dash so I can constantly monitor battery voltage and verify that the alternator is charging.

 

[Delvey]

Thanks for the responses everyone.

I have bought a proper car battery charger (Rohr DFX-150) with a de-sulphating reconditioning feature, along with a 130AH deep-cycle caravan battery (of the lead-calcium type). Combined cost £150-ish.

Once these arrive the new battery will be fully charged overnight and put in the boot to power the car (dashcam and alarm). The main AGM battery will be brought inside and the charger's reconditioning/desulphating function will be used and then the battery given a full charge.

As John7 points out AGM batteries are less sensitive to low states of discharge but the voltage did fall to around 9 or 10 volts at one point last month so I'm hoping the desulphating will restore the majority of its original capacity/lifetime.

The general procedure moving forward will be to leave the main AGM battery in the car at all times and charge it by fully charging the larger capacity caravan battery inside the house then transferring it to the boot to run the car systems and charge the main battery. After 24-48 hours the caravan battery will be returned inside to charge again. This will be repeated once per week until daily usage of the car resumes.

Would of been cheaper to install a CCTV camera and unplug the dash cam when not in use

 

[nvingo]

Would of been cheaper to install a CCTV camera and unplug the dash cam when not in use

I'm guessing OP isn't guaranteed to park in the same spot every time:

...If I could attach a trickle charger that would be problem solved however I do not own a garage or driveway, it would mean trailing wires across a residential street, not a long term solution.

 

[Aerojon]

don't charge car battery inside ,as when being charged hydrogen gas is produced..