Technically, there’s no limit, but there is at least one caveat… No two batteries will have EXACTLY the same terminal voltages. That means, even for two batteries hardwired together, the slightly higher-voltage one will end up ‘charging’ the slightly lower voltage one.

We would strongly discourage anyone from connecting batteries in series or parallel applications, if the batteries are not identical in age, size and type. Different brands of batteries can have different charging and discharging characteristics, with some accepting a charge or delivering current faster than others.

two batteries

No, you can’t connect batteries of different Ah in series with a good result. However you can connect batteries of different Ah in parallel using diodes. As stated already you should only connect batteries of same type/age/brand in series.

Connecting batteries of different voltages in parallel primary (disposable) batteries – they are not designed to take a charge and so the lower voltage battery is likely to overheat, it may leak or bulge and in extreme circumstances where the voltages are very different, it may explode.

Any number of batteries in parallel is for all intents and purposes just one battery cell. Just make sure they’re at the same voltage when you connect them to each other, so that they don’t try to uncontrollably charge each other. Easiest way to do this is to just make sure they’re all fully charged.

Two Batteries in Parallel, One Charger Batteries connected in series strings can also be recharged by a single charger having the same nominal charging voltage output as the nominal battery pack voltage. The purpose of this wire is to balance the voltage drop evenly across both batteries and each wire during charging.

Charging time will be the same as charging a single battery. Charge more than five batteries by connecting one 12-volt battery charger across each battery in the series, as if each battery were the only one being charged. Charge all the batteries at the same time. This will damage the batteries.

One basic configuration for charging batteries in series is to connect the positive charger output (in red) to the positive end of one of the batteries. Then, connect the negative end of the battery to the positive end of the next one, and continue to do so for the rest of your batteries.

So, if you have two 12V batteries wired in series, then 2x12V=24V. To create a 24V system using two 12V batteries, you would wire the first battery’s “+” positive terminal to the “-“negative terminal of the second battery.