Best option to minimize wear and tear on large 10Kwatt generator used to power 100 watts of lights

beamguy · August 2016

We run an off grid camp that uses a large 10Kwatt generator to power lights in the lodge for about 4 hours a night during the summer. These days with LED lights we could likely reduce the power load to around 100 watts, so this generator seems to be overkill. It was just rebuilt a few years back for about $7000, and in a few years it will need to be rebuilt again. It would be nice to extend this lifetime using some sort of storage, with the goal to minimize the run time on the generator. So the requirements of this system are:

1) Minimize charging time by charging the batteries for as little time a day as possible. That means we likely will not fully charge the battery and accept the reduced lifetime.
2) We will only cycle the batteries maybe 100 times per year, then shut down for the winter. Ideally we would leave the battery in place for the winter.
3) There are too many trees for solar to be practical.

I was thinking we could do this with a 100 Ah 12 volt battery and a 50 amp 3 stage charger. We may only have the patience to charge the battery back up to 85-90% each day, so its lifetime will be reduced - question is how much. Is this a viable charging current - some companies like concord say yes and others say no.

Does anyone have experience with this type of problem that can offer advice?

Thanks

Dave Angelini · August 2016

I do this for a few camps up in the national park near me. You have to get the battery in doors in the winter and trickle charge it.

Marc Kurth · August 2016

I am an AGM guy, and I will respectfully disagree with Dave on this one, very narrow subject - and likely not ever disagree on other topics

Quality AGM's LOVE to be stored cold, IF you start fully charged going into storage.

The Moose cameras in Northern BC, the Alaskan Bear cams in Katmai National park, the Peruvian Condor cameras and the Orca cams off the coaast of Northern Maine, all stay in place "in cold storage" for the winter. I have battery systems that survive on buoys that survive winter in the arctic ocean, on mountain peaks, etc. etc..

Roughly -50 F measured at the battery, is about the lower limit of my hands on experience. Below that and I can only talk about theory.

Select the right AGM battery for the particular application and you can charge it as fast you want to - very hard and very fast. A 50 amp charge rate on a 100 ah battery will go from 50% capacity to 100% in about 3 hours, because of the natural taper of current draw. IF you need faster charging, you need to select your battery carefully, but 2.5C to 3C (250-300 amp rate on a 100 ah battery) is not out of the question. No, I'm not exaggerating and yes, again from filed experience.

Exotic stuff? Secret stuff? Heck no. You can buy it right here from our sponsor!

Others may disagree, but I can only speak from my professional experience. I am happy to share what I know, but it is narrow in scope compared to so many folks here.

Respectfully,
Marc

vtmaps · August 2016

beamguy said:

We run an off grid camp that uses a large 10Kwatt generator to power lights in the lodge for about 4 hours a night during the summer.

Regardless of whether you put in a battery & charger system, you really need a small generator such as the Honda eu1000. It would pay for itself in a year or two based on the amount of fuel it uses.

Quite a few folks here have both a large and a small generator.

--vtMaps

Dave Angelini · August 2016

No problem disagreeing Marc. I just use the flooded batteries and for this application the costco deep cycles are fine and even if you leave them out they are cheap enough to run one each season. I am testing some awesome Lion's now and they will change everything in my designs and others also.

I am assumming that they need the big generator to run the cooking loads at mealtime and so a small generator will not help with the prime task.

BB. · August 2016

You need to measure the loads to be sure (100 Watts of LED lighting is a lot--But not if this is for multiple buildings). A typical system with 2 days of storage and 50% maximum discharge would look like (note, with a battery+inverter, you can have motion controlled lights and low power walkway lights if needed--Always a justification for "more power"):

100 Watts * 4 hours per night = 400 Watt*Hours per night
400 WH 1/0.85 inverter eff * 1/12 volt battery bank * 2 days storage * 1/0.50 max discharge = 157 AH @ 12 volt battery bank

2x 6 volt @ 200 AH "golf cart" batteries would be a very nice fit. And for "seasonal usage" (cheap batteries, only expect a couple years of life), you could run the genset every other night.

A Honda eu2000i genset with a ~20-45 amp 12 volt AC genset would be nice fit (using 0.25 to 0.10 gallons per hour) running 4-6 hours per day(evening).

Use a nice MorningStar TSW 12 volt 300 Watt 120 VAC inverter (has low power stand by mode, and remote on/off input).

If you cannot get any sun for solar panels--Then you should take the two batteries home off season and put then on a good quality float charger or charge once per month on a regular charger (flooded cell batteries will not store more than ~1 month without recharging).

You could run 12 volt LED lighting--But I really like running 120 VAC--It is much easier to send the power longer distances without using heavy gauge wiring (and run cell phone/laptop chargers).

-Bill

beamguy · August 2016

The 10Kwatt generator is ancient history, the camp has been there for a very long time. The unit is the size of a car engine, and was last rebuilt a few years back for a large sum of money, and time, and aggravation. I think the motivation for rebuilding it instead of buying a new smaller generator was "It is run every day so we need something that is reliable", "we don't know if a smaller unit will run the well pump", "It needs to run from propane", and "we like to turn it on by flipping a single switch up in the lodge" rather than walking down the hill to the generator shack.

It seems that there may be much cheaper alternatives these days for propane fueled generators with remote start.

Johann · August 2016

Marc Kurth said:

I am an AGM guy, and I will respectfully disagree with Dave on this one, very narrow subject - and likely not ever disagree on other topics

Quality AGM's LOVE to be stored cold, IF you start fully charged going into storage.

The Moose cameras in Northern BC, the Alaskan Bear cams in Katmai National park, the Peruvian Condor cameras and the Orca cams off the coaast of Northern Maine, all stay in place "in cold storage" for the winter. I have battery systems that survive on buoys that survive winter in the arctic ocean, on mountain peaks, etc. etc..

Roughly -50 F measured at the battery, is about the lower limit of my hands on experience. Below that and I can only talk about theory.

Select the right AGM battery for the particular application and you can charge it as fast you want to - very hard and very fast. A 50 amp charge rate on a 100 ah battery will go from 50% capacity to 100% in about 3 hours, because of the natural taper of current draw. IF you need faster charging, you need to select your battery carefully, but 2.5C to 3C (250-300 amp rate on a 100 ah battery) is not out of the question. No, I'm not exaggerating and yes, again from filed experience.

Exotic stuff? Secret stuff? Heck no. You can buy it right here from our sponsor!

Others may disagree, but I can only speak from my professional experience. I am happy to share what I know, but it is narrow in scope compared to so many folks here.

Respectfully,
Marc

Here is a parts of a data sheet for a 75 ah AGM battery.

Shelf Life

(% of nominal capacity at 68°F (20°C))

1 Month 97%

3 Months 91%

6 Months 83%

Operating Temperature Range

Charge -4°F (-20°C) to 122°F (50°C)

Discharge -40°F (-40°C) to 140°F (60°C)

It also looks like per graph which I could not copy and post here that the self discharge is way way slower with colder temperatures.

This may be the type of battery that could be used year long and then fully charged before leaving camp for winter and leaving it unattended over fall/winter for a set time.

What is the current load and what kind of light bulbs are used right now?
It may take time to charge batteries, so you still have noise and fuel cost and wear and tear.
On the other hand, there are automatic start 12 volt output generators out there that can start automatically when the battery gets low and charge the battery with 12 volts directly or whatever your battery voltage is....no extra charger needed.

Johann · August 2016

beamguy said:

The 10Kwatt generator is ancient history, the camp has been there for a very long time. The unit is the size of a car engine, and was last rebuilt a few years back for a large sum of money, and time, and aggravation. I think the motivation for rebuilding it instead of buying a new smaller generator was "It is run every day so we need something that is reliable", "we don't know if a smaller unit will run the well pump", "It needs to run from propane", and "we like to turn it on by flipping a single switch up in the lodge" rather than walking down the hill to the generator shack.

It seems that there may be much cheaper alternatives these days for propane fueled generators with remote start.

It started out to be lights only that need to be operated and now we are talking about a well pump also. So another 1 hp or so or about another 800 watts per hour and up to 5 times or more starting surges.
What else will be powered with it?
Cell phones, heaters, emergency equipment, communications, small fridge for medications etc etc ?

There may be a reason why there is a 10 kw generator in place.

Need to know all the loads to give a valid correct advise.

Dave Angelini · August 2016

I pretty much knew there would be more loads than 100 watts from the systems I do up here in the park.
Just to do the dishes in a camp where people all show up for a meal. Hot water, pumps, an ice machine, and a big freezer that is shut off at night but runs from breakfast thru dinner.
Honda 7000i and DC lights for safty at night is all they need with a couple GC batts and a 40 amp charger.

beamguy · August 2016

Johann said:

It started out to be lights only that need to be operated and now we are talking about a well pump also. So another 1 hp or so or about another 800 watts per hour and up to 5 times or more starting surges.
What else will be powered with it?
Cell phones, heaters, emergency equipment, communications, small fridge for medications etc etc ?

There may be a reason why there is a 10 kw generator in place.

Need to know all the loads to give a valid correct advise.

I am not planning a "revolution" here, just an "evolution". We already have a power system that runs all these things, I just want to use it less. The well pump needs to be run for about 15 minutes about 4-5 times per day to keep the pressure up in the water system. This is about the amount of time it takes to charge the battery so the thought was to leave it as is for now. In the future we could switch to a 12 volt pump, increase the battery capacity and run it automatically from batteries. The refrigerator is a pretty new propane fueled model, so for now there is no need to replace it. The current camp manager does not use the microwave, so the only loads other than lights are 5-6 cell phone charger and the occasional person charging a full sized laptop. The last of these is optional (we sometimes try to forbid all electronics at the camp).

A few days a year people run power tools from the camp power, but those guys also have their own portable generators sitting in their truck that they can use.

The main concern is convenience. At the moment we have a switch on the wall to turn on the generator. We do not have to walk 100 yards to the shed to turn it on, we do not have to manually adjust the choke, or "prime" the system. We run off a 200 gallon propane tank, so we don't have to pour gas every other day. We pay for that convenience with a $10K system that wears out every 6-7 years. There may be cheaper alternatives, but the last time it wore out we could not find them.

And the biggest thing we are missing is anyone who understands the power loads who can make a plan that he is sure will work. In the absence of that we keep doing what we have always been doing.

jonr · August 2016

Sounds like if you replaced the well pump with a Grundfos SQ (no startup surge), you would be fine with a 1-3KW propane generator (autostart would be nice) and/or a much smaller inverter. This would be a big step forward.

My understanding (could be wrong) is that if fully charged/equalized once per month, lead acid batteries will do OK with partial charges. Perhaps in the Winter, you could get enough sun somewhere to use solar just to keep the batteries charged.

One thing that will extend the life of your current generator life is to let it warm up before putting load on it. Also consider installing larger pressure tanks to reduce the starts needed for water (lots of wear occurs on cold starts). Getting down to one or two runs per day might make a non-autostart generator (inverter based with propane conversion?) reasonable.

Best option to minimize wear and tear on large 10Kwatt generator used to power 100 watts of lights

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