12 volt battery

[Almo1954]

The 12 volt yellow battery warning message displayed today and I had to switch off and on several times before the car would boot up as normal. Why does this happen ?

 

[Coulomb]

I'm guessing that the 12 volt battery was not charged. MGs don't seem to charge the 12V battery when parked, as other EVs do. If you don't drive the car for a while, or the battery is on the way out, or it's suffering in extreme cold, it might not have enough energy to run all the computers and get the car to Ready. Until you get to Ready, the 12V battery won't get charged (via the DC-DC) from the big battery.

Perhaps use an ordinary 12V battery charger overnight to really top up the 12 volt battery. Consider charging the whole car more often when it's very cold; the 12V battery should get charged at the same time as the main battery.

If you continue to have problems, it might be time to replace the 12V battery. The dealer can do this, or you can do it yourself. Perhaps consider paying a bit more up front and choosing an AGM replacement battery. They seem to do better in EVs than common starter batteries.

 

[Almo1954]

Many thanks for your reply.

 

[pollenface]

I frequently work away from home and my vehicles are left parked at home for a couple of weeks at a time.

I use a small solar panel to keep the 12v battery topped up on both my EV and ICE vehicles.

The hassle saving is beer worthy.

 

[Tim Green]

Where do you put the pv panel when using it to maintain the battery? Can it go on the facia under the windscreen, or does it have to be on the roof or whatever?
I use one for my old TD which is in a remote garage, and that works very well.

 

[pollenface]

On the dash is fine. I run the wires through a grommet under the dash to the battery. I disconnect the panel when home so I'm not looking at its reflection in the windscreen.

Whenever connecting solar panels to charge controllers always connect the battery first so the charge controller can detect the correct voltage.

 

[Tim Green]

yes, i am afraid my TD has to.live on the PV for about 6 months between October and April. As long as the battery is sound, it is no problem. The charge controllers are excellent.

 

[Coulomb]

I am afraid my TD has to.live on the PV for about 6 months between October and April.

For that length of time, that as a very rough guess, you should use a moderately substantial panel. I'm thinking 25W or so, not a 5 watt small one. The charge controller (MPPT) will be essential for that size of panel. I'm not familiar with what size of 12V panels you can get these days, and how large they are physically.

The alternative would be to disconnect the car from the battery, and use a smaller panel (still with MPPT for this length of time), but then it's not so convenient to leave the panel inside. It will of course need to be placed where it will get some direct sun (through the windscreen is fine) for at least part of the day. At least will be summer, assuming that are in the northern hemisphere.