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Applying a potential across an alkaline battery

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jta

New Member
I have an application where a potential as high as 36V would be incident across 4 series-connected AA alkaline batteries.

If there is a high resistance (say 10k) in series between this connection, would this be sufficient current limiting (worst case 36V/10k = 3.6mA assuming 0 ohm impedance within the batteries) to protect the batteries?

My application does not permit the use of diodes to block current in any direction.

Thanks
 

Sceadwian

Banned
You can use a resistor but not a diode, how does that make sense? You really need to prevent that current from flowing, can you use a 100k resistor?
Despite what makers say you can actually recharge (a few times) alkaline cells, but their chemistry isn't stable under those conditions, so you get very few charge/discharge cycles and the capacity diminishes fast.
I don't have the hard fact to back it up but I'm going to guess that 3.6ma over a AA battery for any length of time would be very bad for the cell.

The one thing you don't mention is how often and for what length of time that voltage will be present, which is VERY important to answering your question.
 

jta

New Member
whoops, you're absolutely correct, I forgot to mention the duty cycle.

I'd estimate at worst 20ms every 20 minutes for a maximum of 10 cycles. So, pretty low.

Basically, the batteries plus the series resistance provides a small test current across a fuse used as a continuity check. A diode would become reverse biased giving a false 'open' as the 36V supply is applied to the fuse.
 

Mr RB

Well-Known Member
No it shouldn't. You'll have the same result from the resistor if that is so.

If the 36v causes the resistor to carry curren tback to the battery, there is no battery current going out to the fuse. In that way the resistor has the same effect as a diode.
 

Noggin

Member
I'm not sure I understand the circuit you have, but what if you put a diode in series with the batteries, but then something like the following

Code:
----B----B----B----B----D-------
|                               |
----------Z---------R-----------

Where B are batteries, D is a schottky diode, Z is zener, and R is a resistor. This would allow the batteries to not take a charging current and the zener would break down under the increased voltage and pass the current to avoid your open circuit detection. Hell, or just use NiMh batteries

(I REALLY need to install a schematic program, this is retarded)
 
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