Battery upgrade

Hi braintrust I need some help.

I found confusing pros and cons about fitting a new bigger battery into my other (Toyota) car.

Old battery was 12V 70Ah 700A

The new has identical physical size but rated as 12V 80Ah 740A

Some say it will slowly kill my alternator over time because it won't be able to keep up with the increased demand of charge capacity.
On top of this the oversized battery might never get fully charged due the low output of charging current.

Please advise

Hi
Nope, that's nonsense in my opinion and experience.
I Would happily fit that larger battery and do nothing with the charging system. It's fair to say that if your current battery is going flat with your use profile, then the larger battery is not going to help. In this instance you should look at a larger output Alternator or just drive around a bit longer.
I fitted a much larger battery on my Scimitar to improve the CCA starting, never damaged the standard Alternator. I also increased the cable sizes to the starter etc, so I kept a watch on cable loadings.
The ratings on your two batteries are very similar, 10AH more and 40 more starting, not much to worry about.
 
 

As above, larger battery will be fine and have a better reserve particularly if you have extra electrical devices such as lights, a winch etc

lt won't kill the alternator, it's designed to deliver charge as needed and the output is regulated so it will be fine.

lf it's (say) a 60A alternator it won't wear out any quicker delivering 60A than it would delivering 30A.

My jimny no longer got a 45Ah lead acid but a 70 Ah AGM Battery. Same original alternator
Has been great especially now with 10-15 degrees of the cold blue ones.
www.bigjimny.com/index.php/forum/8-my-ji...kuza?start=96#217746

My local motor factor sold me a replacement a while ago that was from memory something like 45ah and 320cca. It was alleged to be correct for my Jimny. 3 years later and it wouldn't cope with the radio on for 10 minutes without the engine. Went back to get a new replacement and this new one is also alleged to be the correct one for my Jimny but it's like 15ah more and about 80 more cca. Just because you have one older battery in don't assume it's the correct one if it's not the original factory fitted one.

Thank you all! New bigger one has been ordered!