Generator sizing to handle equalization for FLA bank

[Riley5781]

Hi guys -

As I continue to design my off-grid cabin, i want to ensure my generator & inverter will be large enough to handle the equalization charge (and also of course run the cabin to some degree at the same time).

My battery bank will be a 48 volt 430AH setup of 6volt (Rolls S-550) batteries.
The inverter likely a Conext XM 6048 6KW invertor/charger

I am leaning towards a 6500 watt 120/240 volt gen-set

Will this be large enough to equalize the battery bank?
when doing so, I can reduce the load in the house to just a few LED lights if needed.

[Raul]

I got the s480 , 375a@c/20. My gen is 2200w and the inverter charger capable of 30 charging amps. I have limited the charger to 3/4 and only equalise at the end of absorb , that way leaves me with spare power from gen to the loads.
I think a 3kw gen will be enough but it depends how much of that will be used for the loads during equalisation.

[Sunking]

Equalization has nothing to do with Generator size. The size of the generator is determined by how much maximum load the generator has to carry. The correct size of the Generator = [Load + Charge Rate] x 1.25.

In other words if the connected load of say 3 Kw (your lights, fan or whatever is expected to be running), plus say a 5 Kw Charger you need a minimum 10 Kw generator. The charger is sized to charge the battery at maximum allowable charge rate for your battery to minimize fuel burn.

EQ is just a voltage set point in your charger and has nothing to do with the generator size.

OK so here is your numbers. You have a 6 Kw Inverter with an 80 amp built-In battery charger operating into a 48 volt 430 amp hour battery right. So if you figure 3 Kwh of lights and gizmo's running and a 48 volt 80 amp charger (4 Kw) you will need a [3 +4] x 1.25 = 8.75 Kva minimum generator. So now you go shopping for a 10 Kva genny.

Easy peazy

[Raregift2000]

Hi ,I do solar install for clients mostly designed by the seller. I have a 20 kva system with 2 x 10 kva victrons , 3 x 5 kw sunnyboys and 60 panels. battery back is 48 v 3200 ah. there is also a 20 kva single phase stand by generator.
I have set the generator to run at 52 hz to cutt out the sunnyboys , client is arguing that they should sync and one could have the combined charge. I have been told this is not possible and can damage the alternator. Can you plse shed more light on the subject.

[Mike90250]

I'll have to add to this. Sunking's formula used to be correct. But nowdays, the generators - even industrial units, are not rated by full load. I had been running my Robin/Subaru/Hatz diesel genset at 90% of rated load, and at 50 hours, when the frequency regulation drifted out of the range I could allow the inverter to accept (68Hz)
I was told the alternator was "overheated from overload". it had been run in a open shed in <60F weather. Not conditions normally associated with overheating, Additionally. I've discovered that it has very little reserve for poor power factor loads, so I'm now limiting it to 70% of rated cont power, which for a 3Kw genset (3.3Kw for 10 min) starts eating into my capacity for charging my 48V 800ah bank. I can still do it, but slower. And with my older 3K genset, I can run the water pump AND charge batteries, but the Robin/Subaru/Hatz diesel can't do much charging with a pump motor running before Power Factor issues take effect.
Old generators = robust
New generators = much less robust.
Fortunately, out of my 3 gensets, the newest is the least used,
XW6048 inverter charger
The Conext XM 6048 6KW invertor/charger has adjustable charge amp rates (you should get the ComBox to program and monitor the inverter with)
55Vdc @ 45A =2475 watts
Only you know what your loads are going to be, if it's cloudy and raining, you likely won't be running the 3 ton air conditioning.

Battery charging is un-forgiving, you are pulling a constant power for hours. Not like running a construction site where you have a big saw that runs for 4 minutes and then it's off, letting the genset cool down

[Riley5781]

Thanks guys, this is helpful. I'm struggling to balance the costs of the cabin build with doing it right.
I'd like to put off the cost of the generator for a couple of years and try to get by with my honda 3000 watt but I don't think it will cut the mustard.

[Sunking]

I'll have to add to this. Sunking's formula used to be correct. But nowdays, the generators - even industrial units, are not rated by full load.

Mike I have no problem with what your are saying. I am trying not to over kill it too much. Multiplying x 1.25 is 80%.