Using a bigger battery than a car was designed for?

It'll be fine

If the car needs a new battery, then yes.

The alternator will fully charge the battery, and will then balance the discharge.

If the larger battery is, say, 50% discharged, it will take longer to replace that 50% than if the smaller one was similarly discharged. It will still get to the same state eventually.

Of greater significance than the battery A/hr rating is firstly its physical properties. Will it fit the tray? Will the leads reach? Are the terminals the correct type?

Secondly, is it the right type for the vehicle? Many modern cars are designed to use calcium technology batteries. These charge to a slightly higher voltage. The consequence of this is that you can use either a standard lead/acid or a calcium battery on an older car designed originally for a standard battery, but you should not use a standard battery on a car intended to use a calcium one.

Chris

No - that would be like saying you need a bigger pump at the filling station to fill a bigger petrol tank. The alternator will just take longer to charge a bigger battery than a smaller one - if both are in a similar state of discharge.

If it will fit physically, it will likely be fine.

The only criterion that matters is will it fit the battery compartment without any modification to the leads or clamp. If it does there's no reason not to fit it. Advantages in having a larger capacity battery, is that the car is more likely to start in very cold conditions, or after being parked for say 2-4 weeks. Unlike older cars, the standing time, (when it fails to start because the battery is flat) in a modern car with immobilisers, alarms etc, is greatly reduced. Mike.

The car and battery will not be damaged. I have a the largest battery possible fitted to my car as it is a diesel. It is much easier to start in the cold weather. No problems charging it up either. My alternator gives off the typical 14v. With a smaller battery it has a limited capacity, so if you do need to keep turning over to start, it would run down like mine did. You can also make a very old battery work again by getting some stuff from the chemist called EPSOM SALTS. Then buy some deionised water from ASDA. Mix the epsom salts in to the water as it is heated to fully dissolve it. Pour it in to each cell and use a standard charger. Once charged, connect a headlight bulb up and let it discharge, then charge again. Now you can use a Smartcharger on it. There is no need to throw old batteries out. Just remember BIGGER is BETTER. It also depends on the make of battery, some are better than others.

I have been playing around charging car batteries from a current regulated Lab PSU. An alternator typically can provide up to 100 Amps however a battery will never take more than this to charge for a significant amount of time.Therefore the current limiting to protect the alternator from over heating is not likely to be much of an issue It depends therefore on how you drive the car to some extent, however it will probably be fine.

I agree

mr p used his keyboard to write :

You would have to increase the charging voltage significantly to get an ordinary car battery to accept anything even close to 100amps. The best I have ever managed on a 14v limited supply is 15 to 20amps even on a high capacity battery which is completely flat. That is how the big rapid chargers as sold to garages worked - they would output 20 to 30 volts, rapidly putting a charge in, but the battery had to be carefully and constantly watched.

It will be fine, providing the voltage regulating circuit on the alternator is working correctly - and you would soon know if it were not.

A high initial charge is reduced early to protect the battery from overheating - not the alternator. Some high powered ones are water cooled. But alternators have to be capable of supplying high currents continuously to power all the gismos on modern cars.

IMHO it would make sense to have a temperature sensor inside the battery - you could then cut down the charge current at the latest possible point. As is done with the better cordless power tools, etc.

And if it wasn't, the bigger battery would be more a help than a hindrance.

Chris

Use it. Shouldn't be a problem. It's common practice with the classic Minis I drive, where 038 is the standard spec but many of us use 065,

My daughter has an 04 C2, which recently had issues with the battery light coming on. After a new alternator, new coil (because Citroen said it was faulty), new battery, the light still came on. Citroen's final suggestion was "fit a bigger battery", which we did and the fault has not recurred since.