Car Batteries 101 : Testing & Charging/Maintaining Batteries

Cheers!

It seems pretty obvious but then most things are with a bit of thought .

The guy is on the right lines more than he thinks believe it or not.

But now for a little about keeping the batteries good and what kills them.

But what about the batteries? Can chargers really bring batteries back from the dead?

Yes & No. Mostly the latter.

With the batteries it is a case of how it has lived as previously mentioned. But with care batteries can last. My M3 amazingly is on its original battery and I know of a few cars that are as is a spare BMW battery I acquired. It’s 6 years old and is still in perfect health as a spare battery from almost day 1. A friend’s 2001 Focus is also on the original, but now dying battery. Have we been lucky? Not quite, as I shall go on to explain.

What tends to kill batteries is sulphation of the plates. That arises from two main causes

• Excessive Discharge Cycles
• Neglect

This is one reason why Taxis and commercial vehicles tend to have a limited warranty ; their batteries are constantly started and stopped and taking a hammering. As for neglect this is probably the biggest killer to most of us here, with some batteries taking it worse than others. Stop/Start batteries attempt to circumvent this by using AGM batteries but that is a discussion for another time.

When I say neglect I am referring to the batteries being discharged excessively. This could be from the car being stored and left, the car being left a while and only used on shortish trips, or it never receiving a true saturated charge if say the vehicle was flattened by accident. Of course, battery drains can contribute towards this.

Some batteries don’t take this as well. IME Gel batteries don’t and even some AGM/AGM based batteries don’t seem to recover well once they have been flattened excessively and then left without a proper recharge.

Once sulphation has started it needs to be caught. Not catching it in time will allow it crystallise which is what kills the batteries.
Of course, the solution is to ensure the battery is kept fully charged or as close as possible to on vehicles that do short trips or aren’t used much

It’s OK. I’ll drive the car down the motorway. That will charge it right?

Not quite.

Driving the car down a motorway for a while doesn’t recover a battery fully. This is because the alternator doesn’t always have the chance to and with more consumers in a car it can’t really. What it will do is give a surface charge to the battery and give the illusion of it being charged for a short while.
Lead acid batteries respond better to a slower charge


Surely that doesn’t matter? My fancy CTEK or similar charger can solve anything.

Erm, no.

A CTEK or other smart chargers cannot remove permanent sulphation. Once the damage is done, it’s done. It even says that in the depth of the CTEK FAQs and the manual.

What a smartcharger can do is keep whatever capacity your battery has left good, and prolong the life of that capacity; the error phases won’t say if the battery is any good, merely that it will accept a charge and/or to a semi-usable capacity of the battery. It can ‘bring back’ a small amount of capacity IME thanks to its fancy multi-stage process which can do a better job than an el-cheapo charger.

A pulse or other type of automatic charger will tend to give you most of the things the CTEKs can and charge a battery up almost as well, so you’re not losing out much to not having a smart-charger. As in to within 5% off a CTEK or another smartcharger can. A smartcharger can maintain a battery better admittedly I must admit and is safe in that respect.

I’ve probably missed something but that is about it.

So what can I take away from this?

A bit hopefully

• Always ensure the capacity of your battery is adequate for your car. Using the stock figures for your car helps here or similar.
• A multimeter will essentially show if your battery is completely shot. Not whether it is usable for your application. As said, I’ve had poor cranking situations with a 12.6V float on the battery. With other testers now being available cheaply it may be worth considering one if you have quite a few cars.
• Leaving batteries in a car unattended and unused is what can kill them. Also not correctly recharging a battery once the car has gone flat after say a bad alternator or leaving the lights on does not help.
• Having a semi-smart or smart charger can indeedy be beneficial, but it will not perform miracles. If you want that, watch a movie with them in.
It seems pretty obvious but then most things are .

As said I've managed to come to my conclusions from what I've experienced and seen others experience. However, I've done some reading and helped that aid my conclusions. One helpful site is this one below:

batteryuniversity.com

Chas, what perfect timing.

Up until recently, the '38 was used at least once a day during the week for the school run and sometimes more, but mainly all short distance, even if sometimes long in duration! This kept the battery in a good enough state to easily start the vehicle, but probably never properly charged it.

Now she's been promoted to weekend toy only, the battery probably needs a bit more consideration and, when left unattended the first week flattened over the inactive five days. Hence me suspecting it's not fully charged.

Last weekend, I stuck it on charge Friday evening and left it, on the 2A setting, overnight and Saturday morning, after which it showed >75% charged. Ran it out on Sunday then fired her up again on Wednesday until hot. All being well, I'll take her for a run on Saturday or Sunday, but again, probably not far enough to "fully" charge it..

Obviously there'll be some weekends when other things are happening, so it could sometimes be two weeks between runs.

As my charger is able to tell me about various states of charge I assume it to be at least semi-literate, if not actually intelligent.

So my question is this...

If I want to keep the battery in top condition, what's the best course of action? Just leave the charger on it? Hook it up on a Friday? Do nothing; suck it and see?

The ambient heat kills them pretty quickly anyway, so anything I can do to prolong the battery life is a bonus!

Thanks!

Don't mean to be difficult, honest, ChasR

I was getting around three years in Malaysia, but doing a lot of longer trips at speed, and around two years here. This one's probably due for replacement anyway as it's been over two years now, so I may do that, then set up a regime of regular charging over and above the weekend runs.

I'll see what make the charger is when I get home, but I'll bet it's not very bright!

Useful thread!

Actually, given that a new battery is only a phone call and twenty minutes away, I'm going to see how long I can make this one stretch.

It was fine this weekend, so I'm going to try it with a charge every four weeks or so.

With an Optimate 4 you can leave it in the car, as long and you don't use the recondition mode or the 18V one which may be the same thing. Given the modules etc. modern cars have I'd be tempted to leave the battery in . IIRC those have a CAN-BUS mode which is handy for this. Going to 16V is good but it's not something I'd use on a battery often unless it is fully flat ; it's great for getting more life out of a battery since it allows for the acid/water to be remixed and stratified but it can cause water loss due to how it does it, even if it is controlled; it affectively separates to the water into oxygen and hydrogen with controlled boling(ish) so that the mixture can become useful again. CTEK themselves say not to use the mode much (1 a year on a good battery) unless it is fully flattened).

With your E90 you have an additional problem. You may well have the Intelligent Battery System, aka. IBS (don't go sniggering now!). If you swap out the battery it's advised to get the new battery, preferably a new one, coded to the car. BMW do this and the iCarly app with the right OBD bit can do this, albeit at £100 but it can diagnose and code your car too and much more.

Failure to not code the new battery can play havoc on the battery life. Basically, BMW made the IBS so that it could vary the charge rate to the battery as it got older and to help a little more with the emissions in general.

The solar chargers seem to be a mixed blessing. I know of a number of people who have binned them, but the odd person who has sworn by one, but you are talking over a week in terms of letting it charge for those few rare cases!

The cold one is relatively simple to explain and it is one that is influenced by a few factors. But batteries can be a little like humans when things get cold .

1) Batteries discharge more when they are cold. This is one of the reasons why its is recommended to store batteries cold, as with the higher discharging they are more suspectible to sulphation.
2) The cold temperatures reduce the effective CCA of a battery which doesn't help. Conversely hotter temps can increase the battery CCA, to a point
3) Batteries which are discharged are more susceptible to freeze. A fully charged battery can go down to -50 degrees Centrigrade. A fully flat one? -5. That is down to the chemistry of a battery and what the electrolyte becomes when flattening (sulphation) takes place.

It is said cheaper batteries don't have as good an acid mix for the electrolyte which seems to be more common these days unfortunately, as one ex-battery manufacturer bloke said here.

As I said earlier, a car will generally only give the battery a surface charge, especially when the battery has flattened, rather than actually fully charging the battery up.

Of course, a frozen battery can cause further damage to a battery.

4) Battery size. I know of tons of people who fit a lighter battery to save weight and say "12V is 12V right?" yet forget power is derived also from current In a semi-discharged state thanks to the cold and probably never seeing a charger this will affect things even more. Like most things, do people really think the manufacturers whacked in a big battery just because they could?

What I'm basically saying is keep the batteries charged during winter if they are going flat or the very least ensure they are fully charged at the start of winter and at the very least match the battery that the manufacturer supplied with the car ; I know Halfords suggests a smaller battery for my dad's car than what Ford supplied it with ; Ford changed the battery spec it seems depending on the spec of the car. I'm sure they do the same for my M3 ; most of their batteries don't match the Ah rating of my battery, which is the original dealer battery going by the date stamps.

We use that Sealey tester at work, and it's not far off a fancy Midtronics tester. Again, they are a guide but not conclusive as you say . Nowt wrong with a Maypole charger either ;they were one of the first people on the scene.

The battery in my current (no pun intended) daily is now 19 years old so I reckon I’ve nearly had my money’s worth out of it.

A few things I’ve learnt over the years....

My CTEK charger is great for topping up batteries but I don’t leave it on maintenance charge for too long. Better to connect it up either overnight once a month or for 30 minutes a day.

A handy bit of kit for resurrecting very flat batteries is a 400Ma gell cell charger. Cheap as chips and great for priming batteries that show very low voltage.

Batteries contain magic imps that obey no laws of physics or chemistry. They can work fine at 8.00am and then all escape by 9.00am. They will usually time their escape to coincide with the most inconvenient moment.

As far as fitting a big battery to improve functionality goes while a good idea this is just not possible in many modern cars as the battery cradle is too small. When I say modern I'm referring in particular to my wife's 1990 Ford BG Laser. The battery cradle in that thing is tiny. I recently (last winter maybe) replaced the battery in that just to be sure it would start for her every time. The battery I removed (now five years old) is still a good spare that I would use in my own car if necessary but I don't need the bs I'd get if her car wouldn't start even just once.
As to winter killing batteries I have always believed that at least part of the issue is the higher usage of electrical things in winter, in particular lights and wipers. In summer a dodgy battery may be fine as it is only required for starting and gets a chance to at least half pie recharge while driving. In winter, with lights on constantly when driving, this doesn't happen. This seasonal variation will be even worse for you folk in the UK cos you're further north than I am south.

I'm looking for a decent charger to sort out a few of my car batteries. My main need is to have something to top them up so I have been looking at the Ctek MXS 5.0, the Noco g3500 and a GYS FLASH 6.12.
There are various reviwews on the Ctek and Noco but I can't find much out about the GYS one.

Can anyone offer any info about them ?