12v battery - can you charge without disconnecting?

[Llynyfan]

Hi folks, 

I know a lot of this has been covered and the answer may exist somewhere in the forum.

We've just returned from a weeks holiday and after a 7 hour drive, neither of us is up for spanners and the like. Our CHR has been parked in the garage, unlocked and with the thief sensor turned off...I hoped, I really did, but no, the Battery has lost enough that it wont start. All the pretty lights are on, but it wont start.

Having called out the recovery companies more than 4 times in the last couple of years, I was wondering if I could charge the Battery with it still attached to the car, so these guys can have a rest from rescuing Toyota Hybrid owners!

Any guidance much appreciated 😥

[TonyHSD]

Hi,

Yes you can do that with proper smart ( trickle) charger. Do not start the car with charger still connected, that is important. Just connect directly to the Battery terminals and leave it for couple of hours or until the charger shows your Battery is ready and fully conditioned. You can do that procedure once every two months if you don’t drive regularly or long enough. 
Regards 

[Cyker]

All the car electronics are designed to cope with charging current and voltages as they deal with that when the car is in use, so it's absolutely fine.

The only danger I can think of is if your area is prone to lightning strikes, but even then you'd have to be pretty unlucky for a lightning strike to hit your charging cable!  

 

[Llynyfan]

@Cyker I wouldnt put it past lightning to be that unlucky third this week!! 

Thanks for the advice, much appreciated 👍

[Roy124]

Sue, you have the answer regarding charging provided you have direct access to the Battery. 

What I have had done for a buried Battery is the have the CTEK charge cable hard wired and then plug the charger in as required. 

The other thing to consider is a lithium jump start Battery.  It is quite small but has sufficient power to start the system and get it into Ready mode. 

[Rhymes with Paris]

1 hour ago, Cyker said:

All the car electronics are designed to cope with charging current and voltages as they deal with that when the car is in use, so it's absolutely fine.

The only danger I can think of is if your area is prone to lightning strikes, but even then you'd have to be pretty unlucky for a lightning strike to hit your charging cable!  

 

There is a saying that lightening never strikes twice, but I think the man in the USA who was struck three times would beg to differ.

[Gray86]

I 100% recommend a CTEK MXS 5.0 trickle charger, I’ve used this on my Corolla, previous Auris, wife’s Yaris  dad’s 2.0 CHR and many other vehicles since purchase. Best £60 I’ve spent. It’s easy to use, and keeps your Battery in tip top form. Perfect if you keep your car garaged. On the 1.8 it just clips onto the Battery positive (red terminal) and the black clip onto an earth - usually a bolt on the suspension strut tower works well. As others have said you can hard-wire the connection in the packet onto the car so In future you just plug into the wire which takes seconds. Either way, it’s very easy, and will save you having to ever buy a new Battery, or being stranded. 

[Llynyfan]

Thanks @Gray86. I'll look at that as we are changing it soon. I needed some guidance on the here and now which I have, but certainly your solution is a must for the next car.

[Trewithy]

I also use a CTEK once a week just to ensure the Battery is well maintained.  I do this in the garage so the bonnet is left up but I lock the car.  I think it is advisable to always lock the car to ensure all the electronics are shut down to prevent, albeit small, current drain on the 12v Battery.

I also leave the front windows down an inch or two to ventilate in interior of the car and switch off the internal alarm sensor.

[Trewithy]

I should have added that I charge the Battery without disconnecting it.  The positive red cable from the charger goes to the red Battery terminal and the negative black cable I attach to a lug on the engine cylinder head.  I always lock the car, charging or not.  Never had a Battery problem.

[Hibird]

While charging a non isolated vehicle Battery can never be 100% risk free (but what is) charging using a quality modern charger with a sensible current for the type of Battery would more than good enough for me. However I have never had the need to do so on my CHR which has coped with 14 days in an airport car park twice this year although not so sure the previous Yaris would have been as happy.

[Llynyfan]

Didnt take long to get the Battery to a point where the car started, 30 min drive to make sure and we're back to normality. We're going to get a good trickle charger as recommended by members here and hope we dont find ourselves in this position too often in the future.

[JillG]

We had left our car while on holiday for 19 days with a solar charge attached via the diagnostic port as recommended by our local dealer. Started first time.

[APS]

Like so many others here, I can vouch for the CTEK. I've used it on everything from Prius, RX, CT, through my old cars, and the lawn mower. We have not been kind to it and it is left outside, connected when starting and running, wrong polarity. It is pretty much idiot proof (a good thing for me!). It still works like new. I've also had cheaper smart chargers. But, alas, I speak of them in past tense. Waste of money.

The only case where the CTEK does not work, is when you have a completely drained Battery. The CTEK needs to sense some voltage (tension) before it does anything. In these cases, you have to use an old fashioned analogue charger or another Battery to get a little bit of charge in the drained Battery. Then the CTEK can kick in and slowly get the battery back to normal. 

[Gray86]

4 hours ago, APS said:

Like so many others here, I can vouch for the CTEK. I've used it on everything from Prius, RX, CT, through my old cars, and the lawn mower. We have not been kind to it and it is left outside, connected when starting and running, wrong polarity. It is pretty much idiot proof (a good thing for me!). It still works like new. I've also had cheaper smart chargers. But, alas, I speak of them in past tense. Waste of money.

The only case where the CTEK does not work, is when you have a completely drained battery. The CTEK needs to sense some voltage (tension) before it does anything. In these cases, you have to use an old fashioned analogue charger or another battery to get a little bit of charge in the drained battery. Then the CTEK can kick in and slowly get the battery back to normal. 

I managed to resurect the Battery on a neighbours Mini which has been left for months over winter. It wasn’t totally flat (but not far off), the CTEK took most of two days to work it’s magic (with a recondition cycle in there too). Saved the guy a new Battery - worth the bottle of wine he gave me in return. Even EVs have 12v batteries, which may only last a nominal 5-7 years. I recon the CTEK will make batteries last much longer. My wife’s Yaris lives outside, and is 7 years old with only short trip usage. I don’t intend on buying another Battery for that car - and expect to keep it until it’s 12 years old. That longevity pays for the CTEK twice over 😀

[Big_D]

I swear by my Optimate chargers, which I use on my bikes. About four years ago, I took one of my bikes to the main dealer to have some work done. It was there for quite a while and when I went to collect it, I was told I needed a new Battery. They had it on their charger for a couple of days and claimed the Battery wouldn't hold a charge. They delivered the bike back to me (in their van), and I stuck it on my Optimate. Four years later I am still using the ssame Battery. Bike starts first time, every time. Exactly as Gray86 says.

On 9/15/2022 at 2:10 PM, Gray86 said:

That longevity pays for the CTEK twice over 😀

 

[O.W.L.]

Optimates are great. I have used them on all of my bikes & have never had a Battery die on any of them. I was even on the same Battery on a Rocket III after 12 years!

[Roger F]

As said a number of times c tek is great, A must on a modern car