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Old 03-19-2018, 05:58 PM   #1
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Trickle Charge Battery For Power while Drawing on it?

Hi there,

I've read through a bunch of forums and I still don't have a solid answer to my scenario, though I think I know it.

I'm building a party bus and I wanted to run the stereo from the rear of my blue bird. I have 120 A/C power (from a genset) run under all of the seats and to the rear of the bus. I planned on using 2 stereo specific batteries to power the stereo system (head unit, 400 watt amp, 1200 watt amp) but I don't want to draw any from the existing bus batteries or alternator.

My question is, can I use a trickle charger, powered by the 120 outlet, to provide the continual power to the stereo system, and will it be able to keep up? I'm looking at using something like this https://www.amazon.com/NOCO-G1100-Ul...t%2Bpower&th=1

In theory, this is how laptops work...the wall charger charges the laptop, even when you're using it.

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Old 03-20-2018, 11:15 PM   #2
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Generally no, you can't.

Most battery chargers won't even switch on unless they detect a battery attached.

Presumably the equipment you want to run is 12V or you'd just plug it into the genset.

Why can't you just buy a 120V to 12V power supply to run it?
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Old 03-21-2018, 05:39 AM   #3
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look for an inverter/charger. its charge function will keep up with the biggest of stereo's. it will invert your battery power to 120 ac until you plug that inverter into shore power. when you plug it in the inverter it becomes a charger and will charge your batteries or keep them topped off.
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Old 03-21-2018, 08:08 AM   #4
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I have this, it will do what you want and power a bit more. $75 plus shipping if you're interested. It works, I just out grew it.

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Old 03-21-2018, 08:16 AM   #5
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my calculations show you will need a charger that supplies 13.3 amps to keep up with the stereo,
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Old 03-21-2018, 10:19 AM   #6
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my calculations show you will need a charger that supplies 13.3 amps to keep up with the stereo,
I am not sure I follow your math?

I=P/V

Max power = 1600 watts

Battery voltage 12 volts

I suspect that you may have slipped a decimal point. I come up with 133.33 amps. That would be peak load and you are unlikely to run the amps at full output for any period of time.

OP did not specify what the battery voltage is but I am assuming that battery powered stereo gear would be 12 volt.
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Old 03-21-2018, 10:20 AM   #7
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stereo

If I read it correct you plan on using a trickle charger connected to two dedicated stereo batteries to power your stereo, I assume you will use an inverter connected to the batteries to connect to the stereo.
If this is accurate you can power your stereo, but the 3.5amp charger will not work.
one amp AC is equal to about 10 amps DC.
Calculate how many amps Ac your stereo will use and them multiply by 10 for the DC equivalent. probably better to multiply by 12 or 13.
Make sure the charger can handle charging for the numbers of hours you need, some may need to rest and cool down after a few hours.
Unless you use bus bars you will probably want batteries with top and side posts to make all your connections.
DC wire diameter matters as well as how long the wires are, keep all DC wires as short as possible. You can find wire size calculators online.
Use only a real deep cycle battery, not a marine battery, not any battery that lists CCA.
Wet lead acid batteries will off gas while charging, you will probably want an AGM battery if you want to keep the battery inside the bus, make sure your charger is made specifically to charge this type of battery, most chargers cant properly charge an AGM battery.
Until we know the AC power draw we cant discuss proper battery size.
But on the other hand if you can power a trickle charger why cant you just plug in the stereo?
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Old 03-21-2018, 10:35 AM   #8
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i dropped a 3 in there my mistake
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Old 03-21-2018, 10:41 AM   #9
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Let's not get carried away with the apparent enormous power here.

Amplifiers rated at 1400W do not consume 1400 watts of electricity. Depending on how they are rated (RMS or PMPO), they could be consuming as little as 1/10th of that, even cranked up.

The 1400W figure is usually an estimate of the maximum, and fleeting technical capacity often only reproducible in a lab for a fraction of a second.

The true RMS output is considerably smaller, and even that is only for the maximum highs.

Speaker loudness, and what the amp can drive is more a function of impedance and sensitivity.
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Old 03-21-2018, 10:51 AM   #10
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Quote:
Originally Posted by bubb, the real one View Post
If I read it correct you plan on using a trickle charger connected to two dedicated stereo batteries to power your stereo, I assume you will use an inverter connected to the batteries to connect to the stereo.
If this is accurate you can power your stereo, but the 3.5amp charger will not work.
one amp AC is equal to about 10 amps DC.
Calculate how many amps Ac your stereo will use and them multiply by 10 for the DC equivalent. probably better to multiply by 12 or 13.
Make sure the charger can handle charging for the numbers of hours you need, some may need to rest and cool down after a few hours.
Unless you use bus bars you will probably want batteries with top and side posts to make all your connections.
DC wire diameter matters as well as how long the wires are, keep all DC wires as short as possible. You can find wire size calculators online.
Use only a real deep cycle battery, not a marine battery, not any battery that lists CCA.
Wet lead acid batteries will off gas while charging, you will probably want an AGM battery if you want to keep the battery inside the bus, make sure your charger is made specifically to charge this type of battery, most chargers cant properly charge an AGM battery.
Until we know the AC power draw we cant discuss proper battery size.
But on the other hand if you can power a trickle charger why cant you just plug in the stereo?
wrong! ac and dc amps are the same, its a unit of measurement.
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Old 03-21-2018, 12:16 PM   #11
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wrong! ac and dc amps are the same, its a unit of measurement.
They are the same, but for an equivalent power you need a lot more amps at 12V than you need at 120V, hence the much bigger cables and their associated losses.
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Old 03-21-2018, 03:46 PM   #12
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They are the same, but for an equivalent power you need a lot more amps at 12V than you need at 120V, hence the much bigger cables and their associated losses.
that is incorrect sir, if a radio uses 5 amps on ac power it will use 5 amps on 12 volt or 24 volt that don't change. line loss does affect dc current more than ac absolutely, but it don't use any more. you need a bigger wire to get that 5 amps there.
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Old 03-21-2018, 04:35 PM   #13
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Originally Posted by superdave View Post
that is incorrect sir, if a radio uses 5 amps on ac power it will use 5 amps on 12 volt or 24 volt that don't change. line loss does affect dc current more than ac absolutely, but it don't use any more. you need a bigger wire to get that 5 amps there.
Learn something new every day don't we Twigg.........

I am going to have to track down that Ohm guy and straighten him out....

I guess it really isn't "Easy as P=I*E"..... Sorry, I couldn't help myself.
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Old 03-21-2018, 05:58 PM   #14
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Pretty sure amps = Watts/volts. A = W/V. A cable is rated for a certain ampacity, but the actual energy used is the wattage. 1200 Watts at 120 volts is 10 amps. 1200 Watts at 12 volts is 100 amps. That’s why we are all running 2/0 awg to our inverters, but 12 awg to our appliances. The higher the voltage the lower the amperage for a given wattage
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Old 03-21-2018, 05:59 PM   #15
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that is incorrect sir, if a radio uses 5 amps on ac power it will use 5 amps on 12 volt or 24 volt that don't change. line loss does affect dc current more than ac absolutely, but it don't use any more. you need a bigger wire to get that 5 amps there.
You may want to rethink that ... or not.
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Old 03-21-2018, 05:59 PM   #16
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Learn something new every day don't we Twigg.........

I am going to have to track down that Ohm guy and straighten him out....

I guess it really isn't "Easy as P=I*E"..... Sorry, I couldn't help myself.
Apparently Ohm's Law is fake news
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Old 03-21-2018, 06:08 PM   #17
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that is incorrect sir, if a radio uses 5 amps on ac power it will use 5 amps on 12 volt or 24 volt that don't change. line loss does affect dc current more than ac absolutely, but it don't use any more. you need a bigger wire to get that 5 amps there.
You're grossly incorrect. A 1kW load will use just 8.33 amps at 120v, but will use 83.33 amps at 12v. Voltage = Amperage x Wattage. Amps = Watts/Volts. Might want to brush up on your education before you start correcting people who know what they're talking about ...
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Old 03-21-2018, 08:27 PM   #18
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Quote:
Originally Posted by superdave View Post
that is incorrect sir, if a radio uses 5 amps on ac power it will use 5 amps on 12 volt or 24 volt that don't change. line loss does affect dc current more than ac absolutely, but it don't use any more. you need a bigger wire to get that 5 amps there.
While it is true that a given appliance will draw the same wattage whether powered from a 120v source or a 12v source, the amperage drawn from the power source will be different according to the voltage of the source.

For example, your radio that draws 5 amps at 120 volts (600 watts) will draw 50 amps from a 12 volt battery bank (also 600 watts) through an inverter. This ignores the power draw of the inverter itself.

Watts is "true power" (doesn't change with voltage) while amps change with the voltage of the system.
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Old 03-21-2018, 08:49 PM   #19
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well when my fridge is on 3.1 amps ac it draws 3.1 amps dc on my 24 volt system. that's just reality. try again
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Old 03-21-2018, 08:51 PM   #20
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You're grossly incorrect. A 1kW load will use just 8.33 amps at 120v, but will use 83.33 amps at 12v. Voltage = Amperage x Wattage. Amps = Watts/Volts. Might want to brush up on your education before you start correcting people who know what they're talking about ...
back at ya
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