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Old 05-08-2017, 10:41 AM   #1
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AC Charger + alternator

What happens if I run the AC charger (via generator) at the time as the main engine alternator? Both of which would be connected to the same battery banks.
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Old 05-08-2017, 11:36 AM   #2
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What happens if I run the AC charger (via generator) at the time as the main engine alternator? Both of which would be connected to the same battery banks.
Generally, except when the batteries are very low, whichever has the higher voltage output will do most of the work. Nothing will blow up.

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Old 05-08-2017, 01:15 PM   #3
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Nothing is gained , unless the batts are on different strings so the alt sees one batch and the charger the other.
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Old 05-08-2017, 01:24 PM   #4
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Depends on the settings of the alternator VR and AC charger. If its just a run of the mill engine alternator, it will drive the voltage up to around 14.5 volts. The A/C charger will drop down to standby.
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Old 05-08-2017, 01:37 PM   #5
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Depends on the settings of the alternator VR and AC charger. If its just a run of the mill engine alternator, it will drive the voltage up to around 14.5 volts. The A/C charger will drop down to standby.

The more common scenario would be having the solar panels connected & charging while motoring ( I think ) As stated, depending on the settings, one or both will drop down - off.

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Old 05-08-2017, 01:40 PM   #6
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Thanks for the replies, "nothing will blow up" is exactly what I wanted to see.

My generator battery is charged by the AC charger, no stater or other means of DC power on the plant. If I need AC when underway, I need to keep the AC charger active to supply DC for the generator battery. But that means the AC charger is also feeding the other banks. Wanted to make sure I'm not damaging the other banks or alternator having both active occasionally.
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Old 05-08-2017, 04:35 PM   #7
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Depending on the "intelligence" of the charge sources, it IS possible you will parallel doubled-high-amps on the circuit.

This won't IMO harm the batteries, but do make sure the wiring infrastructure, connections, fuses etc can handle the maximum Total current + some headroom margin safely.
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Old 05-09-2017, 06:33 AM   #8
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Also you have the option of an automatic battery combiner that will send charging current to the generator battery when the engine battery is being charged by the engine alternator. Eliminates the need for the ac charger while underway.
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Old 05-09-2017, 06:47 AM   #9
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My generator battery is charged by the AC charger, no stater or other means of DC power on the plant.

No alternator on the generator engine?

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Old 05-09-2017, 07:48 AM   #10
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Multiple charging sources will in some way share the load. Not equally but in reltion to their regulator settings. They will not put out double the current except under exceptional circumstances as batteries have a charge acceptance rate that will limit current into the battery regardless of the capacity of the chargers.

Yes, nothing will blow up. It is common for people to run engines and generator with the inverter left on all the time.
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Old 05-09-2017, 08:18 AM   #11
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I have an old Raritan charger-converter. When the engine ignition is turned on, a sense wire from the old charger turns off the charger output. So when engine is running, charger output is off and engine alternator charges the battery. Raritan charger has 2 sense wires so monitors 2 engines ignition power. But I think if one engine is running it turns itself off to all 3 of its DC charging banks.

If the battery volts drops too low on a start, DC output come on to give starting boost.
It is just an electronic transistor circuit switch in the charger that turns on or off at a preset voltage bias.

Charger circuit designers must have decided such a circuit is not needed as all the other posters don't mention one in their chargers.

A charger -converter concept is no battery power is used when charger-converter is plugged into AC power. All it does is charge the batteries and powers house loads. Of course if I turn on the Inverter and run a big load, the charger-converter wont keep up the volts on its own, so battery power is used.
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