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Title says it all really; can the 12v battery be trickle charged whilst connected to the car?

Bought a new battery for friends ICE car this morning, tested the voltage to make sure it hadn't drained in storage before being sold. Then thought to test the Volt's 12v battery as been meaning to check this for a while - it was 12.3v which seems a bit low even for a cold morning.

I know replacement is recommended at any signs of trouble - but as it's been behaving fine I'd rather have a go at trickle charging it first overnight to see if the rest voltage can be improved.

My charger is a Lidl smart charger (much the same as the far more expensive C-TEK chargers).

I reckon if I don't charge the HV battery at the same time should be safe (I belive MY13 cars can charge the 12v whilst charging the HV battery)? But wondered what others think?
 

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I can't think of any reason why it would be a problem. Even if you charged the HV battery while the 12v charger is on all that would happen is the battery voltage would rise until the charger shuts off.
 

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I can't think of any reason why it would be a problem. Even if you charged the HV battery while the 12v charger is on all that would happen is the battery voltage would rise until the charger shuts off.
I've also been a bit nervous of charging both at the same time, though I am more worried about breaking the dc-dc converter or my ctek. I'm probably being overly cautious; they should have backfeed protection.
 

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I've also been a bit nervous of charging both at the same time, though I am more worried about breaking the dc-dc converter or my ctek. I'm probably being overly cautious; they should have backfeed protection.
The DC-DC converter and the ctek will only see a dc source when connected and current can always flow from the 12v battery, if either is charging the 12v battery all that changes is the voltage which should not be a problem for either.
 

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12.3V seems ok really, if you have worries just 'start' it and the on board charging will charge it back up if there were any under charge. It's not like you have to drive it around the block like an ICE!

Just power it up for an hour or so, and lock the doors. You can do that on an Ampera.

If you feel you must, I would advise against any 'basic' charger. You should only use one that is designed to charge whilst the battery is under load. (Like the RSC 408 that I recommend people buy before all the NOS has gone.)
 

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Discussion Starter #8
12.3V seems ok really, if you have worries just 'start' it and the on board charging will charge it back up if there were any under charge. It's not like you have to drive it around the block like an ICE!
Well after driving home from work the voltage was 12.6, and after leaving it (off) for a few hours it was 12.5 (though it's impossible to get a 'fair' reading on this car because apparently if the headlights come on even with power to the car off (which they did because it was dark and they are set to come on when unlocking) it applies some DC-DC current to the 12v according to a post on the GM forum, so who knows what a true at rest voltage would be!). But yes I decided to simply leave the power on for half an hour as suggested above and keep an eye on it, using the cars DC-DC charger actually saves rather a lot off faff with extension reels etc, not really sure what I was thinking!

Though I almost had fireworks when I used a different multi-meter at home whose positive prong was inserted into the 10ADC socket - luckily i tapped it onto the old 12v battery I had in my boot from friends ICE car first to check I had the right setting - which I apparently didn't due to the flash and spot welding of a multi-meter pin to the battery terminal! Being as the meter is a cheapo and unfused, I calmly changed socket and went inside to find an ahem AAA battery :unsure: to re-test on, which (and no big surprise here), didn't erupt in a puff of smoke, but did confirm the meter still worked and was now set up correctly :rolleyes:

Rather pleased I didn't tap it on the Volt's battery first, as a short (albeit a very brief one) might not have done the electrics any good. My reward for helping someone swap their ICE battery I guess - otherwise I wouldn't have had an old 12v sitting in my boot on it's way to the tip to suffer the shock!
 

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It would make more sense to lift the boot floor and test directly on the battery terminals. If there are any loads on the circuits then you might see a lower voltage at the accessory socket than the battery itself.

Some time ago I linked to very cheap ebay volt meter you simply plug into the accessory socket. 99p each. I bought 4 myself! I think quite a lot of people here started buying them too after I mentioned it. Too cheap not to have one per car!

I do not believe the traction battery opens when the headlights are engaged, but I could believe it does if the headlights have been on for more than a certain time. There might be 'emergency' scenarios where it has been programmed like that.

But TBH your battery sounds OK. You start getting anomalous readings when they go away, one time excessively high over 13V open circuit, then next under 12V unloaded. I don't think you have any issues with yours right now, but worth getting the plug in volt meter and keeping an eye on it.

It is worth everyone anywhere with any EV the 99p it takes to get a plug in voltmeter. I can't explain why EVs are designed so badly that it does not warn drivers of deteriorating 12V batteries, but it seems the manufacturers want to hide this from us for reasons unknown!
 

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It is very poor of Vauxhall (GM?) that the software on 2012 cars were not upgraded to allow the traction battery to top up the 12v battery.

I guess that's what happens when you don't buy a Tesla.

Read recently that they will even upgrade the software on earlier touch screens to improve it.

Now that is a good company Vauxhall take note.
 
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