24V Battery Amp Wiring Help

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If you check the podzuma schematics, he charges his 12v battery pack with a diode and resistor.

Now, I have 2 12v 7.5ah batteries in series for this amp. If I put 2 12v accessory jacks in series, what kind of things do I need to change in order to charge my 24v battery pack instead of this 12v circuit.



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a battery should not be charged faster than about 10% of its ah (amp-hour) rating unless the manufacturer has some other charge rate listed, many times on the side of the battery these charge ratings wil be listed.

now then if the batteries are completely discharged they may very well draw much more current than 10% thus overheating the battery leading to and explosion at worst or depletion of the electrolyte.

a battery take current at a varying rate depending on the type of batteries you have.

what kind of batteries are they, lead acid, lion, nicd, nimh ?

during the first 80% or so the battery should be charged at a constant current and then at a constant voltage, current limited, of course that depends on the battery chemistry.

basically a batteries resistance changes as it charges.
ok is there any information on the sides or top as to the suggested charge rates?

charge voltage maximum should be 13.6 to 13.8 per battery and a series current of around 750 to 1000ma, if you have no manufacturers
information to be safe.

at full charge do no exceed 28v and limit the current at 750 to 1000ma

an lm317 with a heat sink in current limiting would work well, us heat sink.

it might work well with your power supply if the open circuit voltage doesn't exceed 37 volts to the lm317.

this looks like a good circuit with formulas, i haven't verified them,


this is a simple way, there are many more complex exotic circuit with programmable algorithms, like the uc3309 or mc33341.....

look up the batteries on the 'net to see if you can find spec's
Problem for hemos is that a good Lead-acid battery charger circuit is probably more expensive and complicated than he would like to see.

There are dedicated chips from Texas Instruments (Unitrode), Maxim and others -- but I have used the TI and MXIM chips -- they sense voltage, current and temperature. I would guess you can build a very good charger for about $20. Here's an old application note from Unitrode on their '3906 chip:
If you're working with older or salvaged batteries (and even if you're not) you might want to look at a battery charger that has desulphination circuitry. If I understand it correctly, it's a high-frequency pulse that vibrates the molecules of accumulated gunk on the plates, knocking it off and giving better life. Old batteries that no longer charge conventionally can sometimes be brought to life with one of these.

I've had good results from this one:


And as someone above noted, you just need to rig up a switch so your batteries are in series when using them, and in parallel when charging them.

You can connect them in series(similar made battery preferably). You can use the circuit shown here but you may need to change a few components to get about 28-30Vdc output. Charging current limit to 120mA.


I am thinking of building a 2 series 12V batteries power supply to get 24-30Vdc and then use CMoy circuit to obtain the centre tap +/- 12-15VDC to power the LM1875 module.

Someone reported good results(smooth highs) with battery powered LM1875. The LM1875 modules will drive the upper midrange/ tweeter.
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