Timeline for What would prohibit replacing six 1.5V AA cells with a number of parallel wired 9V cells?
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| Nov 14, 2022 at 16:22 | comment | added | Roland | The final warning applies also to series connection. If one of the batteries is kind of bad, it will be burned up by the other, stronger, batteries, and this will happen both in series circuits, as well as in parallel circuits. In series connection, the weak one might see voltage reversal. | |
| Nov 14, 2022 at 15:56 | comment | added | Chris H | @Justme series also means you avoid the possibility of a dead short if one is put in backwards | |
| Nov 14, 2022 at 8:49 | comment | added | Peter - Reinstate Monica | @Justme Sure, don't mix empty and full (but also, as discussed, do not mix them in serial either!). In parallel, the cross-charging (and dis-charging) at least goes in the right direction. | |
| Nov 14, 2022 at 8:21 | comment | added | Justme | @Peter-ReinstateMonica If you have ever used battery operated devices with user changeable batteries they almost always have them in series. It is simpler for the designer and user. You are right, series connection will reverse charge the most empty battery but only when current is drawn. With parallel batteries, they always redistribute charges when inserted, so different batteries are hard to match. Imagine mixing full and empty NiMH, balancing currents could be huge. | |
| Nov 14, 2022 at 2:56 | comment | added | pcdev | You could add power diodes when connecting the batteries in parallel to prevent cross-charging, but then you get slightly higher loss, however in a pinch it would work. But then who's ever been in a pinch such that they can afford to slap five 9V batteries + 5 diodes on something but not 6xAA's? :D | |
| Nov 13, 2022 at 19:34 | comment | added | Peter - Reinstate Monica | And serial charging then overcharges the low-capacity victims so that they deteriorate quickly, increasing the capacity difference and leading to escalating damage. I remember the advice "if you must stack them in series, at least cross-mesh as much as possible" or the like. | |
| Nov 13, 2022 at 19:32 | comment | added | Peter - Reinstate Monica | Interesting part about the advice to not use batteries in parallel. I'd have thought that because the voltage is a chemical constant, the voltages of similar batteries are pretty perfectly equal to begin with. Under load the voltage will certainly drop below any charging voltage, so that "cross-charging" should not be an issue at all. By contrast, there are substantial capacity differences even between similar batteries which damages the lowest-capacity ones in a serial chain at low charge, which is why I would avoid serial use. Where am I going wrong? Do you have a reference? | |
| Nov 13, 2022 at 1:30 | vote | accept | eSurfsnake | ||
| Nov 11, 2022 at 21:38 | history | edited | Justme | CC BY-SA 4.0 |
added 672 characters in body
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| Nov 11, 2022 at 21:22 | history | answered | Justme | CC BY-SA 4.0 |