Advice on small automatic start/stop backup generator or off-grid ATS

[nestorint]

Hello.
I am new to this forum.
I live totally off-grid in the mountains.
My 24V system consist of:
- 2 x 360W solar panels
- 16 280-Ah LiFePo4 batteries (2 strings in parallel to get 24v)
- 2 x JK BMS
- Epever 150A solar charge controller
- 500W wind generator (not often use as not much wind at my location)
- 7500W petrol backup generator with electric startup that I turn on manually to charge batteries when there are no sunny days.
I want to make that my generator start automatically when batteries need to be charged. It's a simple generator with Honda engine 110/220V output and does not have 2 wire auto start.
I could use this generator but it's noisy and thirsty
Or I can get small 2000-3000W quiet generator with 2 wire auto start or without.


What you would recommend and which way is better?
I also seems can't find small generator with autostart
Or small generator takes too long time to charge batteries?

Thank you

 

[svetz]

Welcome to the forums!

...off-grid in the mountains... 500W wind generator... not much wind at my location...

Given you're in the mountains you might find that a tower fixes this, often the wind is sufficient with 30 to 100' elevation, but it can be very finicky and seasonal too.

2 x 360W solar panels, 16 280-Ah LiFePo4 batteries

If solar handles your normal daily needs and let's guess an insolation of 3, than you're consuming about 2 kWh/day (although in winter your insolation might be around 1, it varies seasonally). Your battery storage is 2x280Ahx24V = 13 kWh. Which at 2 kW per day is about 6 days of backup. You can use a tool like PVWatts to get the best panel size for your location.

At a guess, I'd say you were running out of power from no wind and not having enough panels. I'd look into that first as it might save you the noise and refueling of a generator. But, that's not what you asked about....

...can get small 2000-3000W quiet generator with 2 wire auto start or without.
[small generator with autostart] ...I also seems can't find small generator with autostart...

I suspect all you need is any generator with an electric start and automatic choke feature (the automatic choke is sometimes an add-on feature). Just wire the starter switch to also operate off a normally open relay connected to your low-voltage monitor. When the monitor triggers, the relay closes which triggers the autostart, which restores the power, which re-opens the relay. Duplicate for the generator off with a high-voltage cutoff. Check your BMS, it might already have the voltage monitors ready to use with relays (or not even need relays).

Or small generator takes too long time to charge batteries?

What's the c-rate on your batteries?

Let's say it's .5, then the maximum amps to charge a 280-Ah would be (280 x 0.5=) 140 amps. You've two strings, so that would be (2x140=) 280 amps and at 24V that's a (280 ah x 24V=) 7 kW generator. At the maximum c-rate of .5 it would take 2 hours (not including inefficiencies, it'll actually take longer). If you did half that rate with a 3.5kW generator it would take 4 hours, and so on.

 

[OzSolar]

I think you'll have a hard time finding a smaller generator that is 2 wire start "out of the box"

Here's a example of 2 wire start kit for a Honda.

Here's a list of remote start generators. that I found while looking the other day for another application. One of them may suit your needs.

Generally speaking I try to size a generator to be large enough to charge the batteries at the highest amps they can take plus the critical loads in the house.

 

[nestorint]

Welcome to the forums!


Given you're in the mountains you might find that a tower fixes this, often the wind is sufficient with 30 to 100' elevation, but it can be very finicky and seasonal too.


If solar handles your normal daily needs and let's guess an insolation of 3, than you're consuming about 2 kWh/day (although in winter your insolation might be around 1, it varies seasonally). Your battery storage is 2x280Ahx24V = 13 kWh. Which at 2 kW per day is about 6 days of backup. You can use a tool like PVWatts to get the best panel size for your location.

At a guess, I'd say you were running out of power from no wind and not having enough panels. I'd look into that first as it might save you the noise and refueling of a generator. But, that's not what you asked about....


I suspect all you need is any generator with an electric start and automatic choke feature (the automatic choke is sometimes an add-on feature). Just wire the starter switch to also operate off a normally open relay connected to your low-voltage monitor. When the monitor triggers, the relay closes which triggers the autostart, which restores the power, which re-opens the relay. Duplicate for the generator off with a high-voltage cutoff. Check your BMS, it might already have the voltage monitors ready to use with relays (or not even need relays).


What's the c-rate on your batteries?

Let's say it's .5, then the maximum amps to charge a 280-Ah would be (280 x 0.5=) 140 amps. You've two strings, so that would be (2x140=) 280 amps and at 24V that's a (280 ah x 24V=) 7 kW generator. At the maximum c-rate of .5 it would take 2 hours (not including inefficiencies, it'll actually take longer). If you did half that rate with a 3.5kW generator it would take 4 hours, and so on.

I live in Taiwan. My farm in the mountains 500 meters elevation on the hill. Wind gen tower sits on the 6m poll. But I am in kind of bay soo wind it is very finicky and seasonal.
When there is a sun it takes just about 3 hours to fill up batteries. Solar panels double-sided so even at little bit cloudy weather it pushing 4-5 amp.
But it's already 6 days of rain non stop, so 0 charging time.
My BMS settings on very mild side so to battery have a longer lifespan.
Do you think I can use this monitor? DSE3110 MPU Version Generator Engine Controller ?

Thank you

 

[newbostonconst]

I suspect all you need is any generator with an electric start and automatic choke feature (the automatic choke is sometimes an add-on feature). Just wire the starter switch to also operate off a normally open relay connected to your low-voltage monitor. When the monitor triggers, the relay closes which triggers the autostart, which restores the power, which re-opens the relay. Duplicate for the generator off with a high-voltage cutoff. Check your BMS, it might already have the voltage monitors ready to use with relays (or not even need relays).

Not a great option....when the generator runs out of gas it will just keep cranking...or with any problem like not start, bad plug, low oil....it will just keep cranking.....there are some generator controllers that can be bought to protect against this but likely finding a generator with all the work done is best.

 

[svetz]

I live in Taiwan.

What a view! Gorgeous photo, thanks for posting!

When there is a sun it takes just about 3 hours to fill up batteries. Solar panels double-sided so even at little bit cloudy weather it pushing 4-5 amp.

Since you get power even when cloudy more panels might still help. From running your numbers it looks like your insolation is around 6 when the sun does shine which is really impressive!

But it's already 6 days of rain non stop, so 0 charging time.

Pity that when it is non-stop rain there's insufficient wind. Do any of your fields flood during the torrential downpours? Could you make them flood or pond the water? If so, and the plants can stand it, could you dam/funnel the water and use hydro? This version needs a > 8m drop, but there are a lot of different types...

But I am in kind of bay soo wind it is very finicky and seasonal.

With the bay there should be a sea-breeze and land-breeze nearly every day... I bet the layout of the terrain surrounding your farm is naturally deflecting the wind. In fact, that location might have been picked for a farm just because it's a low-wind spot. Ironic?

... My farm in the mountains 500 meters elevation on the hill. Wind gen tower sits on the 6m poll.

6 meters is probably too low of an elevation, I bet there's a lot of wind higher up. Where I live there are elevation maps that show average wind speeds at various heights, I'd have to go ~10m to get enough (but I don't have a 4k meter mountain range being me). I'm not sure how you could measure it... possibly someone will have ideas? A bluetooth wind speed meter attached to a kite or balloon? Put a vane on it so it always points into the wind?

Do you think I can use this monitor? DSE3110 MPU Version Generator Engine Controller ?

I couldn't tell from reading the link if it would work or not. There are a number of instructables and youTube videos around converting a generator to autostart. I haven't done it, but agree with @newbostonconst above that something built-in would be superior for the reasons he listed. Possibly you can find one of the generator controllers he was talking about.

 

[nestorint]

What a view! Gorgeous photo, thanks for posting!


Since you get power even when cloudy more panels might still help. From running your numbers it looks like your insolation is around 6 when the sun does shine which is really impressive!


Pity that when it is non-stop rain there's insufficient wind. Do any of your fields flood during the torrential downpours? Could you make them flood or pond the water? If so, and the plants can stand it, could you dam/funnel the water and use hydro? This version needs a > 8m drop, but there are a lot of different types...


With the bay there should be a sea-breeze and land-breeze nearly every day... I bet the layout of the terrain surrounding your farm is naturally deflecting the wind. In fact, that location might have been picked for a farm just because it's a low-wind spot. Ironic?


6 meters is probably too low of an elevation, I bet there's a lot of wind higher up. Where I live there are elevation maps that show average wind speeds at various heights, I'd have to go ~10m to get enough (but I don't have a 4k meter mountain range being me). I'm not sure how you could measure it... possibly someone will have ideas? A bluetooth wind speed meter attached to a kite or balloon? Put a vane on it so it always points into the wind?


I couldn't tell from reading the link if it would work or not. There are a number of instructables and youTube videos around converting a generator to autostart. I haven't done it, but agree with @newbostonconst above that something built-in would be superior for the reasons he listed. Possibly you can find one of the generator controllers he was talking about.

Yep. That is probably good idea to put more panels so it will draw more electricity during cloudy days. Town where I live in Northern Taiwan use to say there are 200 rainy days a year. But weather changing slow every year. Less typhoons and more sunny days.
I will to lift up anemometer higher off the ground and see if there are more wind.
I even built hydro generator from old washing machine but since we share our water needs (coming from mountain spring) with neighbors it's not easy to get enough water flow into my territory and closest place I can install hydro generator on the way of water stream coming down the mountains is at least 500m away.

Thank you for compliment on location. It gives me inspiration and energy for the whole day only glance at it in the morning. When air is not hazy you can see fishing boats in the ocean

 

[nestorint]

I think you'll have a hard time finding a smaller generator that is 2 wire start "out of the box"

Here's a example of 2 wire start kit for a Honda.

Here's a list of remote start generators. that I found while looking the other day for another application. One of them may suit your needs.

Generally speaking I try to size a generator to be large enough to charge the batteries at the highest amps they can take plus the critical loads in the house.

Thank you for a generator setup tips and list of auto start gens!

 

[nestorint]

Let's say it's .5, then the maximum amps to charge a 280-Ah would be (280 x 0.5=) 140 amps. You've two strings, so that would be (2x140=) 280 amps and at 24V that's a (280 ah x 24V=) 7 kW generator. At the maximum c-rate of .5 it would take 2 hours (not including inefficiencies, it'll actually take longer). If you did half that rate with a 3.5kW generator it would take 4 hours, and so on.

Is it also limited by a battery charger?
My battery charger while powered my 7500W generator never shows more that 10.5amp while charging batteries (switched to "lithium battery" position

 

[svetz]

Is it also limited by a battery charger?

Yes

 

[nestorint]

Yes

"What is a maximum safe current I can charge LiFePo4 batteries?"

Manufacturer replied to me: Maximum support 280A, standard charge and discharge 140A