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Will a battery with larger capacity cause damage?

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Volvo Repair Database Will a battery with larger capacity cause damage?

Post by tjai »

My S60 had a 800ccc battery (replaced by AAA) and it's been in the car for almost 3 years now. However over time I've had a few issues with computer of the car (Power seats not working, passenger side a/c not working; both these problems were computer/software related). The mechanic tells me that the battery being a larger capacity than the recommended is what is causing this issue in the car as the higher voltage causes the computer to have these brain fades, and went ahead and replaced the battery with an OEM battery. However on thinking back I am wondering would the car not have any voltage protection or surge protection preventing such issues with the computer? Is it that the computer starts having issues after years of usage or is it really the battery that can cause such problems.
Any pointers/comments/opinions would be very helpful !!


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Post by jimmy57 »

Don't enter into investments on the advice of that mechanic.
A defective battery could have had bearing on the problems but the capacity of the battery is not an issue. Battery voltage is not different for larger CCA batteries. Other than the weight and cost penalty the larger battery is always the best as far as performance goes. The capacity of the battery has nothing to do with the voltage once the engine starts. Then the alternator is the source of voltage when engine is running unless the electrical loads are greater than the output of the alternator. In that case the battery contributes amperage to operate things. Engine idling with most things in car on is the only time this woud occur. A larger battery which suffers a much lesser discharge doing the engine cranking and actually will give a more stable voltage as a rule. The larger battery would not suffer as much discharge and voltage depression starting the engine so the voltage in electrical system would be at normal level much sooner after the engine is running.
I would suspect a faulty alternator to be the contributor to the problems if there is any contributor.
Some things do fail so the modules having issues after years of use is the most likely answer.

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Post by precopster »

To further add to that argument if you put a far larger battery in the car than 800CCA (as long as you can devise a way to fit it and it is a 12V battery) and as long as the current draw of your electrical system is not exceeding it's capacity you would enjoy far greater life and voltage stabilisation than with a smaller battery.

The rule of thumb with CCA rating of batteries is buy what you can afford (and fit) but be sure it meets the minimum rating for your vehicle.
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Post by fazool »

Reaffirming what's already been stated: I have spent some of my engineering time specifying and designing products which utilize rechargeable batteries. The batteries have only three characteristics that essentially matter:

1) Physical size, dimensions, location and type of connection
2) Nominal voltage rating of the battery (in your case it's 12v)
3) Stored electrical charge "capacity"

In small batteries (Li-Ion, NiCad, etc) this capacity is measured in mAh (milli-ampere-hours) meaning "at the rated voltage load, how much current can be drawn out of the battery and for how long".

For example, a small 5v battery with a capacity of 2000mAh can run 5v load feeding it 50mA for 40 hours or 1mA for 2000 hours. Some sensitive batteries limit the upper current draw as well (for example a 2000mA draw would be too much current so it uses a protection circuit internally to prevent that)

But car batteries pre-dated all that rating stuff and everything was 12v. The only thing that mattered was how many amps could the battery pump out to crank the starter motor (called cranking amps). Since it was highly temperature dependent, they started advertising cold cranking amps because a battery in Minnesota in February will produce less output power than a battery in Arizona in July. Because the battery charge is not consistent this is actually a "burst" measurement of a full battery.

Its not a perfect measurement of battery capacity (as in a simple mAh rating) its actually a straight max output current amount (pure amperage). Now.....to *get* that much current (in amperes) coming out of that type of battery, you need to build up a heavy charge capacity. You see, at very high currents, the capacity bleeds off VERY fast, so a small capacity battery can squeeze out 100amps but only for a fraction of a second then it starts losing power. So, to get that current output (amperes or in a car's case "cold cranking amps"), you need to have a high capacity battery.

The mathematical model for electrical power is the same as for hydraulics and easier to visualize:

If you have a water tank (like your towns water department has - they trickle fill it so its a tall elevated tank), the HEIGHT of the tank provdes the potential for powerful blast (like voltage). The higher your water tank the more pressure out your pipes. Thats the same model as voltage.

The LARGER the tank, the more the tank can hold, the more capacity and the longer it can run.

But....here's the tricky part....

The bigger your pipes, the more water can flow through them (current in amperes).

Now, if your shower is a 12" big pipe and really uses lots of water (or think of a fire hydrant etc), it will really dump lots of water quickly.

Similarly, if your starter motor draws lots of current (in amps) it will use lots of that stored battery power quickly.


To combat this (and unlike cell phone batteries, etc.) and because of the old fashioned rating system and because car batteries are more interested in short-time big bursts of power (vs. the small draw long trickle of cell phone or laptop battery), the mAh rating is not used. Instead, they say "how much current can my battery fully provide until it runs out".

Back to the water tank analogy:

If you KNOW you are going to open your fire hydrant to put out a fire.....how big of a hydrant can you run off of your water tank until it runs dry?

Its a stupid question and doesn't take into account - how dry is dry, how much water do I need, etc.

Well the CCA is a stupid ranking too. It means how many amps can I pump out in a burst. But it doesn't tell you how LONG that burst is or for how long it can maintain that (is it a 1 second burst? Or ten 2 second bursts?)

But, the fact is, in order to maintain that amperage the industry standardized on : CCA is how much current the battery can pump out continuously for 30 seconds, before its voltage drops below 7.2V

So like a water tank, as you dump water out, the level goes down, making the power and pressure weaken.

So CCA is a combination of output *AND* short term capacity.

(sorry long winded I know)

So, your battery is 12V.
Your battery physically fits and it connected.
The *ONLY* other parameter is how much charge the battery can provide and for how long.

Your mechanic was completely wrong in telling you that you overpowered the system because of your CCA rating. If the battery was defective and putting out 16 or 17 volts then maybe you could damage something, but sensitive circuits have voltage protection circuits and regulators (which is why they can run anywhere from 7-15 volts).

He is either mistaken or dishonest or just making crap up because he doesn't understand basic electricity.

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Post by tjai »

Hi All,
Thank you so much for the explanations, went back to my bigger better and the car is running fine.
Appreciate all the help !


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Post by CountryBum-kin »

The only problem I ca see by installing a higher capacity battery is it may put more load on the alternator.

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Post by jimmy57 »

No, farm tractors with two HUGE batteries often use a 35 amp alternator. The alternator feeds battery, not the other way around.
A larger battery will take longer to recharge if it gets weak but the voltage regulator controlling voltage level by nature regulates current into battery for charging.

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Post by Nikkivii »


I realized this post is over 6 years old, but I registered (I don't even own a Volvo) just so I post to say thank you for your easy to understand explanation. Also, I find it amusing that you brought up Minnesota winter. It was -55°F, with windchill, last night and my 3 year old Diehard Gold battery left me stranded. I was researching about using a bigger, more cca battery when I stumbled onto this thread. Now to messure my battery compartment and off to finding the BIGGEST battery it could fit. Thanks again!

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Post by Rattnalle »

These cars will fit rather large batteries since the same fittings are used in all of the models and there are diesels with fuel and battery powered heaters in the lineup that require large batteries. They will also work with AGM for higher cycling resistance and charge receptivity.

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Post by abscate »

Wind chill has no effect on batteries, it is strictly the absolute temperature that determines performance

Wind chill is badly overhyped to tell eyeball views on the media.
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