12v Battery

CanJIm · April 5, 2020

My 12v Battery loses charge in about 12 days. Is this normal? I can\t tell if it's a Battery that's dying or a voltage drain which of course I can't detect. Solution currently is to drive it every week but is this normal? I'd appreciate any advice.

Gliderpilot · April 5, 2020

I've hooked up a 12W solar panel to my Battery to keep it topped up.

Bob99 · April 5, 2020

Hi James, there has been quite a lot of threads on here now since the lockdown about the 12v Battery. Quite a lot of people, me included, are charging it with a ctek charger. I just did mine over the last couple of days. If the car is idle for most of the time the alarm and entry system may slowly deplete the Battery. Going for a drive would only partially replenish it so to be safe a full charge would be best.

RgrWynne · April 5, 2020

If you can just leave it permanently on the car, I do, but obviously not forgetting to disconnect when using the car, which I have nearly done🤦‍♂️

Illogan · April 5, 2020

Just as Gliderpilot (post #2) is doing - I've now placed a solar panel on my dashboard, and have it plugged in (to the OBD2 port (beneath the steering wheel)) when parked up for long periods.

My Battery went flat in just 10 days prior to doing this!

CanJIm · April 11, 2020

On 4/5/2020 at 9:44 AM, Illogan said:

Just as Gliderpilot (post #2) is doing - I've now placed a solar panel on my dashboard, and have it plugged in (to the OBD2 port (beneath the steering wheel)) when parked up for long periods.

My battery went flat in just 10 days prior to doing this!

This sounds like a plan, but how do you hook it up to the OBD2 port?

CanJIm · April 11, 2020

Why can't I plug it into the accessory socket? Are any of them live with the power off and the car locked? Is there any way of turning one of the accessory sockets on?

Battery was flat again today after 6 days.

Herbie · April 11, 2020

23 minutes ago, CanJIm said:

Why can't I plug it into the accessory socket?

Accessory socket/cig lighter are only energised when the ignition is on, so no, you can't plug a solar charger in there. Most solar chargers come with a variety of connectors, one of which is an OBD2 plug like the one below:

Illogan · April 11, 2020

I bought one rather similar to the post that Herbie mentioned!

It works well

Keeling54 · April 12, 2020

I need to get one of those, have 2 C-Tech chargers but they are in my lock up 20 miles away. My Battery was destroyed after 4 days of no use.

ColinBarber · April 12, 2020

5 minutes ago, Keeling54 said:

My battery was destroyed after 4 days of no use.

Then it was well passed it's best and needed replacing.

Keeling54 · April 12, 2020

25 minutes ago, ColinBarber said:

Then it was well passed it's best and needed replacing.

It was only 4 years old, guess I have a massive drain somewhere.

Barry14UK · April 13, 2020

Assume correct Battery was fitted. I would think the 12v Battery should hold up OK for a couple of weeks without use if it was nearly fully charged to begin with. If it doesn't last this long the Battery could be failing or discharging due to a heavy drain somewhere in the system or even something like happened to me once on a different car where a light in the boot remained on. Best check it out with a multimeter.

flookyk · April 13, 2020

I know that the RX400 had problems with batteries draining if left unused for a couple of weeks or so but does anyone know how long the RX450h can be left unused before action needs to be taken?

Zotto · April 13, 2020

During these virus times I use my RX for 3-4 km. weekly, so after almost 2 months I decided to charge battery; accordingly with measured tension it was at about 20% of charge.

Barry14UK · April 13, 2020

9 hours ago, flookyk said:

I know that the RX400 had problems with batteries draining if left unused for a couple of weeks or so but does anyone know how long the RX450h can be left unused before action needs to be taken?

This will depend on the state of charge before car was laid up and how good the Battery is. It's not a bad idea to check with multimeter when car is about to be laid up and charge it to full. (If you have a CTEK or sililar smart charger, you can just leave it connected and forget it because it will keep Battery charged up as necessary). Otherwise suggest you check once a week initially. If Battery still shows reasonable charge you could leave it for a week and check again charging as necessary. So you can determine whether a fortnightly boost is necessary. With a good well charged Battery the figures obtained may mean you could extend to checks at 3 weekly intervals. You might be OK for even longer but I would not chance it without a solar charger or smart charger such as the CTEK. See what Lexus said which I posted under 'Alternative Battery' thread about Battery problems currently being experienced and their suggestion for running car at intervals. We are only considering charging our 12v Battery here. If the car is laid up for months it would be necessary to run the car to charge the traction Battery as I don't think there is any way an owner other than a specialist can charge that.