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Author Topic: Batteries  (Read 452 times)
W1GIL
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Posts: 1




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« on: February 15, 2002, 07:56:20 PM »

I have several motorcycle batteries that I'd like to use for emergency power.
They are all 12v but of varying capacities (12-24Ah)

Can these be connected in parallel for charging and useage?
(I'll be drawing 18-20 Amps.)

I have received conflicting information and would welcome your input.
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WB2WIK
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Posts: 20542




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« Reply #1 on: February 18, 2002, 01:01:17 PM »

No, they cannot.  Batteries can be used in _series_ for both discharging and charging, since the (charge and discharge) limit will be established by the overall (total) series resistance of the cells used.  Unfortunately, they cannot be used in parallel because only the device with the lowest resistance will do all the work; the others won't do anything.

WB2WIK/6

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AG4GT
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Posts: 29




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« Reply #2 on: February 22, 2002, 07:00:22 PM »

I have 2 diesel trucks that have 2 batteries wired in parallel and they live together quite happily.  I must admit that we are talking about a discharge current of 10 - 15 times what you are talking about.  Normally, when you wire batteries in parallel, you need a small resistance between each one, 1 - 2 ohms but like I said, the 00 wire that connects mine defiantly does not have much resistance.

Give it a try.

Steven
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KC5JK
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« Reply #3 on: March 01, 2002, 03:40:52 PM »

Use a rectifier diode (such as those used in automotive alternators) to each battery (+) for charging, then switch them all into parallel for supplying a load (or exit each battery with another diode to feed the load, to avoid switching).  RVs and other vehicles do this for a single second (or auxiliary) battery, but the principle can apply to any number of batteries.  The diodes isolate each battery from the other(s), as if it's the only one.

(CHARGER)--->|---(+)--->|---(LOAD)

(duplicate for additional battery/ies as needed)
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