system
Given the following post, respond as if you're commenting on Reddit:
human
Is it bad to use different brands of batteries in the same device?

For years my parents always told me never use different battery brands in electronic devices because even though they emit the same voltages, they are manufactured differently there are slight variations in voltages and this will cause them to leak. Now that Im older and moved out, plus it being the year 2011, very few of the devices I own use batteries. I was only reminded when I had only two fresh batteries left for the remote but they were of different brands. So is there a problem with this?
gpt
Electronics engineer here.

It depends a lot on how the batteries are used in your device (serial/parallel topology):

* if they're in a serial connection, the batteries most likely won't be affected (i.e. leak) but the device might or might not perform well, especially when at least one of the batteries is low. In a series connection the whole set of batteries is as "strong" as the weakest one in the set, so if one battery, being from another brand dies out quicker... you get it.

* in a parallel connection, unbalanced power supplies (that don't have the same output characteristics) behave really really bad (potentially hazardous); if we're talking about batteries they might heat up, leak, do some damage.

So basically, you don't need to know the intricacies of your device and how it uses the batteries; overall it's a good idea to have same-brand, same-model batteries of the same age, whenever possible.