Son’s car has been parked up for a couple of months and surprisingly now has a flat battery. Anyone recommend a booster pack?

New battery, if its gone flat it will never be reliable again.

Every time I’ve tried a booster pack it didn’t work. Jump start it off another car or take the battery out and charge it with a normal charger.

There’s a type of booster that is a power capacitor. Connect it to your existing battery (even a dead one provided it has enough to do something) and it charges the cap. Then dumps it back in one big lump. They are small enough to live in the car. Not tried one myself but the vids I’ve seen look promising.

I looked at this previously and decided removing the battery and just charging it (or charging in place), with our antique battery charger made more sense, than spending £100+ on a device I might use once every few years..*

K
New battery, if its gone flat it will never be reliable again.

Is this comment based on science? Anecdotally, my car has a habit of draining the battery, so that a warning is displayed on the media system if left for any significant length of time, but happily charges back up and works fine with the auto-stop/start. I had thought I’d needed a new battery when it first happened but I’ve had it 4 years now and still the same battery.

*PS: If you in a hurry, as above, just jump it from another car.. a good set of leads is much cheaper

my car has a habit of draining the battery, so that a warning is displayed on the media system if left for any significant length of time, but happily charges back up and works fine with the auto-stop/start. I had thought I’d needed a new battery when it first happened but I’ve had it 4 years now and still the same battery.

So your anecdote exhibits a non reliable battery and somehow that discredits the fact that a full depleted battery is subsequently significantly less reliable than a non depleted one….. I’ve been nursing a fully depleted battery since the first wave of covid and my car didn’t move for many months charging every month or so….. If finally had complete failure last month even my fancy charger can’t revive it.

Is this comment based on science?

A low car battery can be recharged. A deep discharge will almost certainly kill it.

Is this comment based on science?

Looks like it…

Battery Basics

Wow I asked him to confirm it, or flesh out the comment, like Cougar did…
I’m not discredit the theory with an ANCEDOTAL comment.
As always STW, at it’s best

Welcome to the forum. We eat biscuits and know things.

😁

New battery, if its gone flat it will never be reliable again.

Is this comment based on science?

Yes. Lead acid batteries are metal dipped in acid, and normally that causes corrosion. In the case of lead acid batteries only the charge on the plates prevents that. So if your charge drops below about I think 10.5V (can’t remember the actual number) then the corrosion process starts, called sulfation. Small amounts can be reversed by charging up, but once it gets bad it can no longer be.

The damage to your battery depends on how long it’s been left at low voltage. I had a battery drain problem on the Passat, and I fixed it but the battery would still drain after about a week. It was because it was simply losing its charge. If I drove every day, no problem, but the battery was still technically buggered.

If you aren’t guaranteed to drive every day though you will need a new battery otherwise it just won’t work that well and you’ll always be worrying about starting it on a cold morning.

https://www.costco.co.uk/Tyres-Automotive/Car-Maintenance/Chargers-Jump-Starters/Energizer-9000mAh-Lithium-ion-Polymer-Car-Jump-Starter-Model-50806A/p/269663

I have one of these and it has successfully jump started my 3.0l Touring even when just over half full.

Yes. Lead acid batteries are metal dipped in acid, and normally that causes corrosion. In the case of lead acid batteries only the charge on the plates prevents that. So if your charge drops below about I think 10.5V (can’t remember the actual number) then the corrosion process starts, called sulfation. Small amounts can be reversed by charging up, but once it gets bad it can no longer be.

That’s only true if it’s only charged IN the car where the likely max recharge voltage is 13.5-14v. Using a plug in battery charger with a higher max charge voltage over 15v will recondition the battery and recover a lot of the performance from the plates.

https://www.costco.co.uk/Tyres-Automotive/Car-Maintenance/Chargers-Jump-Starters/Energizer-9000mAh-Lithium-ion-Polymer-Car-Jump-Starter-Model-50806A/p/269663

I have one of these and it has successfully jump started my 3.0l Touring even when just over half full.

Hmm, so thats a 9ah battery with pretty thin looking leads. I assume that extra box is some sort of protection/capacitor/trickery. .

Impressive. Tempted to pick one up as my car sometimes leaks electricity. At present I keep it on a battery conditioner, so technically it’s a plug in hybrid.

I know many people who use the LiPo jump packs. They seem to be amazing given their size.

As for rescuing batteries I’ve had to do this on cars and bike before. I’ve used both expensive ctech and oxford chargers for this but I’ve also used a middle of lidl special. They’re all equally effective and so long as its not dead-won’t-light-a-lego-street-light-dead then they can usually be recovered. Keep them nice and warm and they can be up and running in a day.

Using a plug in battery charger with a higher max charge voltage over 15v will recondition the battery and recover a lot of the performance from the plates.

Smart chargers with a ‘repair’ function can improve batteries but it’s not guaranteed, and you don’t necessarily get full performance back.

I have a titchy lipo pack and it is fantastic, but it won’t start a car with a really dead battery. It basically provides enough kick combined with whatever juice the car’s battery can provide. And mostly that’s all you need so it’s very useful. Mine got a real workout during lockdowns, everyone in my street knew I was always working on cars so I became the Car Starter Guy.

Definitely agree that a battery can be killed by discharge but it’s not a given ime. I’ve brought back several to perform perfectly, including the one in my car now. Any decent modern charger can do more than old school chargers or charging it off the alternator. (I’ve also got an ancient motorbike smart charger which seems perfect for reviving really dead batteries)

For really starting anything, you just want another car battery. Next time you replace one, keep it, put it on a trickle charger. Nothing better.

Never tried to recover a totally flat batter. But I used to keep my motorbike battery connected to an Optimate 3 trickle charger over winter (when it was off the road).

My other top tip – wear ear defenders when changing car batteries – swapped one for a neighbour (medical student with no tools) and holy crap, as soon as I connected the new one the alarm went off and with the bonnet open and my head in the engine bay it was flipping loud – set my tinnitus off for days…..

I could not recover my leisure battery to more than about 11.9V with a smart charger.

I have a titchy lipo pack and it is fantastic, but it won’t start a car with a really dead battery.

I also have one and never had any joy with it. I suspect if your battery is damaged rather than simply lat it doesn’t give you a lot.

I have a CTEK 5 which has a repair function to clean the lead part of the battery. Been using it for many years on many cars and it keeps everything running well. With COVID we didn’t use the cars, I charged them overnight every couple of months and they are still running.

Not sure how it will do on a dead battery but worth a try.

Cheers all – borrowed a mates charger and the battery doesn’t seem to be taking the charge – the car needs an MOT and TBH I’m wondering if it’s worth fixing – a 2006 VW which has served us well for the kids to learn on and then drive as teenagers won’t be worth a lot!

Dependent on the charger type and the size of the battery, they can take a long while to charge. A normal 12-14v charger will take up to 80hours to charge a 110amp battery. A16v charger will do it in about 5-6hours.

I have one of these and it hasn’t failed. Mind you, a replacement battery would be significantly cheaper

https://www.halfords.com/motoring/battery-maintenance/jump-starters/gb40-1000a-noco-jump-starter-721898.html

I have a titchy lipo pack and it is fantastic, but it won’t start a car with a really dead battery.

This is a fact of life, working where I do – back when we had over 3000 vehicles on site, some for months, using a jump-pack was a several times a day issue. I had one car that just wouldn’t start, we had to get a breakdown truck in, when he checked the battery, it had 3.5volts in it… 😳

We were trying to charge a block of metal. He did get it started, enough to get it the hell off site and someone else’s problem.

It wasn’t unusual to have two jumppacks and a set of leads from something with a diesel engine trying to start a car in one of our storage areas at one time. Thankfully, we have nothing like that number of vehicles on site anymore.

Peugeot 208’s are a bit problematic at the moment, as soon as the battery drops below about 12.3 volts, the cars won’t start, and these are new cars, from the factory. Some do sit around for a while, waiting to be consigned to a driving instructor, but we have lots of Fords, other Peugeots, Seats and Vauxhalls, and none show the same problem. As the cars are being pulled and valeted ready to be dispatched to a driver within a day or so, they get a mains charger attached, to avoid any embarrassment!

Most of the “known” brands have a warranty of three to five years for a car battery, less if it’s a taxi or similar, because of the number of charging cycles that any battery will stand.
Keep the battery topped up with a decent charger to avoid sulphation which could tear your warranty up
Time and charging cycles will kill batteries, if you get more than five years reliable service in all temperatures for £15 pa for a standard battery then you can’t be too annoyed 🙂

a 2006 VW which has served us well for the kids to learn on and then drive as teenagers won’t be worth a lot!

I sold mine at that age for 1400 and I got done. No point scrapping a car for the sake of a new battery.

Yeah, ops choice obvs but I’d sling a battery on it and put it in for an MOT. Prob cost less than a full tank of fuel….