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SimilarIsland

On board charger amps (pull)?

18 posts in this topic

Does anyone know how many amps an MK345 (3 bank x 15 amps)Minnkota on board charger pulls on the 110v side? I'm trying to determine whether a Honda generator (5000 watts) will be enough to charge my batteries and another buddy's batteries on his boat. I couldn't find anything on the Minnkota HSOforum.

Thanks

SimilarIsland

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Your total watts would be 4950 if the charger would draw the max amount. The way to figure this out is PIE. Power= I current or amp x E voltage. 45 amps X 110 volts = 4950 watts.The problem would be if you and your buddy completely used up your batteries in one day the generator could only handle you for a while till you quit drawing max. amps.

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Thanks,

So the 45 amps at 12 volts just carries over to 110 volts?

I was hoping that the 45 amps @ 12 volts would have less pull than that at 110 volts.

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45 amps x 12 volts = 540 Watts

540 Watts/110 Volts = 4.90909 Amps

Is this correct?

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I'd say around 5 amps on the input side of the charger.

Using 120V as the standard voltage:

120VAC/12VDC = 10.

45A/10 = 4.5amps

You could use 14VDC too for "worst case" but it still isn't that much and the generator should handle it.

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You got it. Power is power, regardless if it's AC or DC. You may have to add in a little extra for the losses due to the transformer, etc, but your calculation is definitely in the ballpark.

We had an interesting thing happen the other day at work with a Honda generator and battery charger/inverter that may be related to this. On a piece of equipment we use a charger/inverter. What this does is takes 120VAC line power and charges a 12V battery. If the line power is removed (power outage), the charger turns into an inverter and pulls off of the battery that it had previously be charging, transforms it to 120VAC, and then powers the equipment to keep it running until line power is restored. We had to drop the line power so we connected the generator but the charger/inverter wouldn't change back to "charge mode" like it should after a three second delay. I didn't get a chance to look into it further but we are suspecting that the generator is putting out a square wave rather than a clean sine wave and the charger/inverter doesn't like it, so it stays on "inverter mode". Just a theory right now, but you may want to test your configuration to make sure the charger will function as you want it to.

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Great! Thanks.

One of my friends was also telling me to watch out when the generator runs out of gas. He thinks that's what blew his charger on the last trip.

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SI sorry about my bad math or just not thinking that your amps were on the DC side and not the AC side but it looks like you got it right.

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No problem, I was thinking the same way to start with.

It's nice to have this forum where we can put all our minds together.

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You got it. Power is power, regardless if it's AC or DC. You may have to add in a little extra for the losses due to the transformer, etc, but your calculation is definitely in the ballpark.

We had an interesting thing happen the other day at work with a Honda generator and battery charger/inverter that may be related to this. On a piece of equipment we use a charger/inverter. What this does is takes 120VAC line power and charges a 12V battery. If the line power is removed (power outage), the charger turns into an inverter and pulls off of the battery that it had previously be charging, transforms it to 120VAC, and then powers the equipment to keep it running until line power is restored. We had to drop the line power so we connected the generator but the charger/inverter wouldn't change back to "charge mode" like it should after a three second delay. I didn't get a chance to look into it further but we are suspecting that the generator is putting out a square wave rather than a clean sine wave and the charger/inverter doesn't like it, so it stays on "inverter mode". Just a theory right now, but you may want to test your configuration to make sure the charger will function as you want it to.

Depends on the Honda generator series. The ones with inverter technology should be as clean, or maybe even cleaner, than the AC power off the grid.

The non-inverter models may not be perfect sine wave, but unlikely to be square waves. Honda HSOforum has some pictures/representations of the waveforms from its various generator series.

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After posting I looked up the Honda generators and they are a square wave unless it's one of the generators in their "Inverter" series, which the generator in question is not. This would make sense as to why the charger/inverter didn't work.

It isn't a square wave in the classic sense, but it has stepped characteristics instead of a smooth sine curve. This chops off the peak and that is were the issues will happen as many sensitive devices depend on that peak to operate. I suppose it could be referred to as a modified square wave or maybe it's even a psuedo sine wave.

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On Rainy Lake we had a 1000 watt Honda generator. 2 boats had 2 bank chargers 20 amp total. 1 boat had a 3 bank charger that was 25 total amps. The 4th boat had a 1 bank 6 amp charger. We could plug a combination of any 3 boats in on most nights. It couldn't handle all 4 at once.

After one very windy day we could only plug in 2 boats if the 3 bank was one of them.

We ran the generator out of gas every night and had no problems with the chargers or batteries.

The 5000 watt generator should charge your 2 boats with a combined 90 amps easily.

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On Rainy Lake we had a 1000 watt Honda generator. 2 boats had 2 bank chargers 20 amp total. 1 boat had a 3 bank charger that was 25 total amps. The 4th boat had a 1 bank 6 amp charger. We could plug a combination of any 3 boats in on most nights. It couldn't handle all 4 at once.

After one very windy day we could only plug in 2 boats if the 3 bank was one of them.

We ran the generator out of gas every night and had no problems with the chargers or batteries.

The 5000 watt generator should charge your 2 boats with a combined 90 amps easily.

The chargers work on 120V, the 1000W generator is about 8.5 Amps at 120 volts.

Two 20 Amp (at 12v) chargers would be roughly 5 Amps @ 120V, probably closer to 6 when you count losses. Adding the additional 25 A (at 12 v) of the three bank charger would bring the 120 V load to 6.5 Amps theoretical, but likely closer to 8 or 9 Amps at 120 V considering losses. So, the math works out near perfectly with what you observed.

About the 5,000 watt generator, assume it will be about 4000w continuous. This means that it would support roughly 300 Amps of charging at 12 V.

4000W divide by 12 V = 333 Amps. Reduce that to account for conversion losses and you end up with being able to support about 300 Amps of battery charging current.

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I just got a power converter for my fish house and a 1000w generator- will da generator run the converter???

What do you mean by power converter, 120V to 12V?

Watts are universal meaning that 1000W at 120V is equivalent to 1000W at 12V. So, your 1000W generator would support a converter capable of putting out 1000W at 12V (~80 Amps) from the 1000W at 120V (~8 Amps).

There is some loss in the 120V to 12V converson so it won't come out exactly like that, but you get the idea how it works in general.

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Yeah, that's what I meant.. 120V AC from the generator through a converter to get 12V DC.

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