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Post Info TOPIC: How many amps from generator?


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How many amps from generator?


How many 12 volt amps will a 2000 watt generator potentially provide to the batteries?

 

B



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Brodie Allen wrote:

How many 12 volt amps will a 2000 watt generator potentially provide to the batteries?

 

B


Watts divided by voltage = amps. 

However if the 2000 watt 240v generator has a 12 volt outlet, it will be almost a waste of time trying to charge a battery with it. The 12v output on generators is generally restricted to a nominal 12v to use as a power supply only. For battery charging a higher voltage is required. So you could leave it connected to a battery all day with little to no charge going in.

If not using the generator's 12v output you would need a mains battery charger connected to the generator & the current (amps) put into the batteries would be determined by the charger's capability.

 



-- Edited by Cuppa on Monday 28th of August 2023 10:11:37 AM

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thanks Cuppa but what I would like to know is how many 12v amps will be available to
the battery (given that the charger is big enough).

Ta.

B

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8 amps normally from the 12 volt outlet, and I have charged a  flat 4wd battery enough to start it after 2 hours running our 1kw genny.



 



-- Edited by Bicyclecamper on Monday 28th of August 2023 12:41:10 PM

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The Victron bluesmart IP22 30amp charger, you can put up to 10 in parallel.

 

So you could parallel 5, but probably better only 4 for a bit more of a safety margin. So 120amps should be enough.

 



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Brodie Allen wrote:

thanks Cuppa but what I would like to know is how many 12v amps will be available to
the battery (given that the charger is big enough).

Ta.

B


 Hi Brodie Allen

I have a Honda EU2i (2KVA) generator, with a dedicated 12 volt DC plug

I once measured 8 amps being produced, while charging a 12 volt AGM battery
As my clamp meter is only an el-cheapo, the real amps could have been a bit higher or lower

Also as it was a few years ago, don't take this as gospel chapter and verse, but I seem to recall that it was charging at about 13.6 volts

A normal 240 volt battery charger, will usually charge an AGM battery at around 14.4 volts

Hope that this info is useful to you



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Brodie as others have said, a generator pumping 12v into a battery is not a good solution. Even if the voltage is high enough (Tony Bev's post suggests not great), at 8 amps it is going to take quite a few hours.

A better solution is to plug a proper battery charger into the 240v socket of the generator. Choose one that puts out the right charging voltage and more amps (say 15-30 .... depending on the size of your battery). A battery charger reduces amps when the target voltage is reached and keeps the voltage constant until it determines the battery is fully charged.


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I think Brodie wants to know how much is going in to his battery via a generator 240V output (not the 12v) to input on the side of van connected to a 240v charger to battery.

As you would power up normally with 240V at a van park except using a gennie on the road.

That's how I read it anyway......cheers Bob



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2000 watts at 12 volts is 2000/12 amps So about 165 amps. In practice it will not be at 12 V but more like 13 to 14 so current will be lower than 165

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Brodie Allen wrote:

thanks Cuppa but what I would like to know is how many 12v amps will be available to
the battery (given that the charger is big enough).

Ta.

B


         As I said that will depend on the charger.

        Potentially your generator could run a charger up to around 150amps (+)  as Tony Lee has said.

        But of course the size & type of battery would also come into play.

        No lead acid  batteries I know of would accept a charge rate that high. Some Lithiums might, but they are not within my sphere of experience. 



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Thanks Tony LEE and Cuppa.

Didn't think we would ever get there.

Got the gist now.

B

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Hi all;
Most generators and their 12 volt battery charging capacity and all the ones i have seen have around a 8 Amp charge. What i have done in my own case is i have a Gentrax 240 Volt generator that is rated at 2Kw. Lightweight ?? and easy to move around when needed. I also have a Victron 12/30 3 Battery charger in my caravan that is capable of charging at a max of 30 Amps. I have two 220 Ah AGM batteries ( so 440 Ah in total @ 12 Volt ) and the Victron battery charger has no problems with chargeing the house batteries and the Generator has no problem with feeding the load demands of the battery charger. The other thing ( and this is why i choose Victron ) is the Battery charge has blue tooth capabilities ( along with the solar controller and smart bridge ) and i can check on my phone how the charger and battery voltage/charge current is going. When one day i change out my house batteries for Lithium the battery charger also has the settings for Lithium. I have never used the 12 volt outlet on the generator for charging. 8 Amps is a bit slow with large battery capacity.

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Cuppa wrote:

         As I said that will depend on the charger.

        Potentially your generator could run a charger up to around 150amps (+)  as Tony Lee has said.

        But of course the size & type of battery would also come into play.

        No lead acid  batteries I know of would accept a charge rate that high. Some Lithiums might, but they are not within my sphere of experience. 


 Hi just a couple of comments on this discussion if anyone is interested in further information.

A 2000W generator is rated for max starting output but the continuous rating is a lot less EG: "Honda EU2000i: Specification 2000watts starting 1600 watts running" 

If you had a big charger(or 4 ??) it would be less than 100% efficiency so the theoretical figure is reduced by say 25% and indeed the power factor might be lower than a small generator would like at high power too.

So I might say less than 100A at up to 14+ volts would be the max to expect a small generator to provide for a couple of hours charging, for a 2000W generator to survive. Just saying !

I have in the past built a few engine powered battery chargers for off grid friends using car alternators for 12V and 24V battery banks at 50A and DC welders at up to 200A @ 24V for a big system. Note real power is required to power them continuously for steady high amp charging, much more than 2000W.

Solar panels eventually took over from the engine powered (biodiesel) chargers as the prices came down.

Jaahn

 



-- Edited by Jaahn on Wednesday 30th of August 2023 09:00:57 AM

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As a general rule inverter generators are only for casual use. The max you should load up one (assuming it's a good brand) is about 85% of it's cont rating, so for my Honda 2.2 with a power factor corrected charger is about 90+ amps into my lithium (that figure is at the absorption set point). However for heavy use you'd be wise to stick to just ~60% of it's rating, so again for my 2.2 that is  60+ amps. Which is a typical size of many AC chargers. Most AC chargers are not good,  usually having a cos theta of just 0.7 to 0.9 no

Finally you should derate the gennys output by (going from memory) 3.5% per every 330m rise in elevation. At some point the unit will need to be re jetted or something for higher elevations.

 

Charging big lithium batteries taxes the generator as they must run hours and hours at full load. Petrol has about 9500wh/ liter, and only 17% of that energy actually makes it into my lithium battery since I want to get long life out of my unit.

 

The fastest you can safely charge a lifepo4 is about 1C for high density prismatics at 30 degrees C (0.7C is a safer beat). At temps below you risk damage (li plating) so the usual recommended rate is 0.5C down to ~5 degrees C, also at higher c rates you can't technically fully charge the battery with constant current alone and this is one reason why 0.5C is the usual blanket statement.

2C for specialized cells (mainly cylindricals), some brands go much higher... The king so far is NiCd followed by LTO then lifepo4 cylindrical like a123 and headway.

 

High recombinant AGMs have their limit primarily set by the design, too much current (that exceeds the removal rate of lead sulfate on the electrodes) gives rise to the gassing stage which can cause hydrogen and oxygen to be lost from the electrolyte and the shedding of active material (major capacity lose). Most top performance AGMs can usually take about 0.4C happily.



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StormCamper wrote:

As a general rule inverter generators are only for casual use. The max you should load up one (assuming it's a good brand) is about 85% of it's cont rating, so for my Honda 2.2 with a power factor corrected charger is about 90+ amps into my lithium (that figure is at the absorption set point). However for heavy use you'd be wise to stick to just ~60% of it's rating, so again for my 2.2 that is  60+ amps. Which is a typical size of many AC chargers. Most AC chargers are not good,  usually having a cos theta of just 0.7 to 0.9 no

Finally you should derate the gennys output by (going from memory) 3.5% per every 330m rise in elevation. At some point the unit will need to be re jetted or something for higher elevations.

 

Charging big lithium batteries taxes the generator as they must run hours and hours at full load. Petrol has about 9500wh/ liter, and only 17% of that energy actually makes it into my lithium battery since I want to get long life out of my unit.

 

The fastest you can safely charge a lifepo4 is about 1C for high density prismatics at 30 degrees C (0.7C is a safer beat). At temps below you risk damage (li plating) so the usual recommended rate is 0.5C down to ~5 degrees C, also at higher c rates you can't technically fully charge the battery with constant current alone and this is one reason why 0.5C is the usual blanket statement.

2C for specialized cells (mainly cylindricals), some brands go much higher... The king so far is NiCd followed by LTO then lifepo4 cylindrical like a123 and headway.

 

High recombinant AGMs have their limit primarily set by the design, too much current (that exceeds the removal rate of lead sulfate on the electrodes) gives rise to the gassing stage which can cause hydrogen and oxygen to be lost from the electrolyte and the shedding of active material (major capacity lose). Most top performance AGMs can usually take about 0.4C happily.


Thank you Jaahn,

 

I was interested in the total 12 volt amps that could be extracted from my little genny

should i have enough charger capacity to handle it. 1600 w @ 240v ac down to 12v dc =  heaps.

More than my 60a Projecta could handle anyway!!

 

b



-- Edited by Brodie Allen on Sunday 3rd of September 2023 12:37:41 PM

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