Generator size

[Booboo]

I am looking for a generator for battery charging in a RV with a Growatt 24V SPF 3000TL LVM and two 272Ah 24V LiFePO4 batteries.

60 amp charger x 24V = 1440 watts. Does that mean a 2000w generator is good enough.

It wouldn't be used very often and size and weight is a big concern for my selection. There are a lot of 2000w portable generators that are small and light.

 

[schmism]

An inverter geny seems like a good choice for your setup. Remember you can configure the growatt grid charge current to be 10-140a. So you have quite the range you can use to dial in what load the genset likes.

 

[MichaelK]

There are two separate issues here, the watts you need, and the watts the inverter is happy to accept. For my inverter, it "qualifies" the power being presented to it, in terms of voltage, amperage, frequency, and distortion. A smaller generator straining to meet a certain load may allow the voltage to sag or the frequency to fluctuate? Your inverter may look at the power and say "no thank you".

In the case of my own inverter, an XW+6848, I can alter the charging input, and it starts to complain about the quality of the power its getting at about more than 1/3 of my generator's stated capacity. I don't know how fussy your Growatt will be, but 3X the power needed is not a totally outrageous request.

Another Growatt user could chime in here, but from my practical experience, you need to go overboard with your generator's overhead.

 

[schmism]

and it starts to complain about the quality of the power its getting at about more than 1/3 of my generator's stated capacity. I don't know how fussy your Growatt will be, but 3X the power needed is not a totally outrageous request.

That's an issue with your genset govener setup. Generators do NOT like to run at low loads. Gensets should be sized to run at 75-80% of full load rating.

 

[MichaelK]

That's an issue with your genset govener setup. Generators do NOT like to run at low loads. Gensets should be sized to run at 75-80% of full load rating.

Hmmm, that's an idea that I might be able to check. What I might try the next time I try generator charging, is that I'll plug in a toaster oven too and see what happens. I'll get back on that later.

 

[schmism]

Hmmm, that's an idea that I might be able to check. What I might try the next time I try generator charging, is that I'll plug in a toaster oven too and see what happens. I'll get back on that later.

A DMM that can read frequency is best. Typically these systems are frequency sensitive. Under load check the frquency and adjust the full throttle setting so that its running at 60hz. (50 if your rest of the world)

 

[John Frum]

I am looking for a generator for battery charging in a RV with a Growatt 24V SPF 3000TL LVM and two 272Ah 24V LiFePO4 batteries.

60 amp charger x 24V = 1440 watts. Does that mean a 2000w generator is good enough.

It wouldn't be used very often and size and weight is a big concern for my selection. There are a lot of 2000w portable generators that are small and light.

Small ice generators are usually advertised by their peak rating.
Here is a fairly representative model that is represented as 2200 watts.

Westinghouse 2200-Watt Inverter Generator—iGen2200

Ultra-Quiet 52dB 2200-Watt Portable Inverter Generator—12-hr run time on 1.2-gallon tank—Easy Carry 46 Lbs & Parallel Capable—Ships Free

www.norwall.com

In reality its rated for 1800 watts continuous.

It should be able to handle your 60 amp charger but its pushing the limits.

If it was me I would go up to this level

Westinghouse iGen2500 Portable Inverter Generator — iGen2500

Ultra-Quiet 52dB 2500-Watt Portable Inverter Generator—10-hr run time on 1.2-gallon tank—Easy Carry 48 Lbs & Parallel Capable—Ships Free

www.norwall.com

 

[MichaelK]

That's an issue with your genset govener setup. Generators do NOT like to run at low loads. Gensets should be sized to run at 75-80% of full load rating.

This may not actually be the issue. What I'm finding in the real-world with my generator is if I try to charge at the desired Amp level, say 40A, the inverter will fail to accept the power. If I instead set the charge level at a very low level, say 15A, the generator accepts the power without complaint.

What I can then do is inch the charge level up every 10 seconds or so to 16A, then 17A, then 18A, all the way up to about 40A, and the inverter continues to accept the power. I can hear the load on the generator increasing as I do this. I can also see the amp measurement on the inverter going up.

Once I pass 40A or so the inverter drops the load, and I can hear the generator drop back to idle. This corresponds to about 36% of what my generator is rated for (6000W). I do have a meter that can measure frequency, so I can monitor that as I go through my routine next time.

To be honest, I really haven't made much effort about this issue because I'm overpaneled, and I have never had to use generator charging. I just do it so I can periodically run the generator.

 

[Steve_S]

I run a 24V Battery System. The Samlex EVO4024 has been programmed to charge the bak at 80A + to allow passthrough power while on Genset. The genset draws 25-27A/(2300-2700W) off the L5:30 (120V/30A) plug during charging. The wattage and amperage do float a bit due to 4 packs in bank and If there is passthough load. * The EVO's are 94% Efficient, where most Inverter/chargers are around 85-89% efficient.

BTW/FYI, most Inverter Generators are High Frequency Pure Sine so never run them close to their rated output and BEWARE of how their power ratings are evaluated. Quite often they will label it as 3000W but that is only for Max Surge Handling and NOT continuous output. It's a Marketing thing.