top up battery bank from generator

System · August 2008

i want to provide electicity to my camp, after a quick research on this subject, solar electric is very expensive and required knowledge to maintain it once setup, misstake could cost a lot.

now i need to electric 24/7 to run lights, a efficient refrigerator, computer and small pump to pressurize water for toilet and shower.

i want to ease myself in to solar power by start very small to learn and minimize the cost when make misstake.

this is come to my mind.

10 kw LP generator to 1-2 hours to top up battery bank.
8 12v, 110 amp deep cycle battery.
1 inverter 2000-3000 watts
80-160 watt solar panel
1 charge controler
what ever else need to work with solar charger.

can some one lead me to link or site that specific to my need or give me advise to make it work (simple vacabulary please)

thanks

rplarry · August 2008

Re: top up battery bank from generator

boonwsun
Probably a little overkill with a 10kw generator, but too much gen is better than not enough. A Honda EU3000i would probably handle those loads and charge your batteries, plus they are not very noisy, a big advantage in a camp enviornment.

8-12v batteries would allow you to go with either 24v or 48v system, I would go with 24v because there are more DC appliances available in 24v than there are in 48v.

I would use a good inverter/charger, like the outback 3524.

As far as a charge controller, I like the mx60 but that may be more CC than you need, but would give you lots of room to grow your solar panel array.

Good solar panels can be found at sunelec (just do a google search) for less than $3 a watt, but they are blemished.

Shurflo makes good pumps in 24v and 120v, I like the 120 volt because of the ease of install, no DC wires to run.

Good luck with your system,
Larry

mike95490 · August 2008

Re: top up battery bank from generator

Your best bet is to run the genset in the morning, when batteries are low, and they can absorb a lot of charge from the generator. Then the solar can top them off slowly over the rest of the day. The 160W of solar is WAY too small for your battery bank, and will barely keep it trickle charged. You will be running 96% off your generator power. Either more solar, or skip it completely and spend the $ on gasoline.

If you are going to use a electric fridge, you will need an extra panel or three, while a fridge uses a modest amount of power, over the course of a day & night it will consume quite a lot of power. Pay the $$ and get the most efficient one you can.

The motor in your fridge will need a Pure Sine Wave inverter, which costs more than a mod sine wave inverter, but the motor will last a LOT longer, and consume less power.

Are you planning on 8ea, 12V batteries ? That is too many to place in parallel, have you calculated your loads to see if you need that much battery? Consider a 24 or 48V system if you need that much. Also, since nearly everybody kills their first battery bank, use cheap batteries to learn with, and next year, buy the expensive ones.

Here for battery sizing: (javascript required)
http://www.freesunpower.com/battery_designer.php

Here to read about wiring schemes: (diagonally)
http://www.smartgauge.co.uk/batt_con.html

System2 · August 2008

Re: top up battery bank from generator

rplarry wrote: »

Probably a little overkill with a 10kw generator, but too much gen is better than not enough. A Honda EU3000i would probably handle those loads and charge your batteries, plus they are not very noisy, a big advantage in a camp enviornment.

i choose the LP generator because we will use LP for cooking stove and a back up heater(toyo). lp can be delivery by gas company.

8-12v batteries would allow you to go with either 24v or 48v system, I would go with 24v because there are more DC appliances available in 24v than there are in 48v.

ok, it will be 24v.

I would use a good inverter/charger, like the outback 3524.

As far as a charge controller, I like the mx60 but that may be more CC than you need, but would give you lots of room to grow your solar panel array.

Good solar panels can be found at sunelec (just do a google search) for less than $3 a watt, but they are blemished.

Shurflo makes good pumps in 24v and 120v, I like the 120 volt because of the ease of install, no DC wires to run.

Good luck with your system,
Larry

thank you very much,
boon.

System2 · August 2008

Re: top up battery bank from generator

thanks Mike, great links, i know i have to do more reading before i can jump in to this project. I don't like the idea to have some one set the system up for me when some went wrong i will be in the dark don't know what to do.

thanks again,
boon.

mike90045 wrote: »

Your best bet is to run the genset in the morning, when batteries are low, and they can absorb a lot of charge from the generator. Then the solar can top them off slowly over the rest of the day. The 160W of solar is WAY too small for your battery bank, and will barely keep it trickle charged. You will be running 96% off your generator power. Either more solar, or skip it completely and spend the $ on gasoline.

If you are going to use a electric fridge, you will need an extra panel or three, while a fridge uses a modest amount of power, over the course of a day & night it will consume quite a lot of power. Pay the $$ and get the most efficient one you can.

The motor in your fridge will need a Pure Sine Wave inverter, which costs more than a mod sine wave inverter, but the motor will last a LOT longer, and consume less power.

Are you planning on 8ea, 12V batteries ? That is too many to place in parallel, have you calculated your loads to see if you need that much battery? Consider a 24 or 48V system if you need that much. Also, since nearly everybody kills their first battery bank, use cheap batteries to learn with, and next year, buy the expensive ones.

Here for battery sizing: (javascript required)
http://www.freesunpower.com/battery_designer.php

Here to read about wiring schemes: (diagonally)
http://www.smartgauge.co.uk/batt_con.html

mike95490 · August 2008

Re: top up battery bank from generator

Boon,
If we knew where you were (like Chicago?) placing this cabin, we could help even more, with array angles to place the solar at, mounting problems with snow, all kinds of stuff.

Are you planning for this to be in before winter, or next spring?

System2 · August 2008

Re: top up battery bank from generator

i building a camp on Graham lake in Waltham, ME.
the cabin will start in this fall, and hope to have the solar electric system up by next spring/summer.
i have no problem increase the size of the solar panel, just don't to make an expensive misstake.
i have been reading from the link you send, it help to build up my confident a bit more.

mike90045 wrote: »

Boon,
If we knew where you were (like Chicago?) placing this cabin, we could help even more, with array angles to place the solar at, mounting problems with snow, all kinds of stuff.

Are you planning for this to be in before winter, or next spring?

mike95490 · August 2008

Re: top up battery bank from generator

In winter, be sure you keep your batteries fully charged:

http://www.powerstream.com/SLA.htm

A fully discharged battery freezes solid at about 0°C, a fully
charged battery freezes about -40°C.

The coulometric charging efficiency of flooded lead acid batteries is typically 70%, meaning that you must put 142 amp hours into the battery for every 100 amp hours you get out. This varies somewhat depending on the temperature, speed of charge, and battery type.

Sealed lead acid batteries are higher in charge efficiency, depending on the bulk charge voltage it can be higher than 95%.

pdxr13 · December 2012

Re: top up battery bank from generator

By your list, it sounds like you have some budget, which is good.

8 batteries is a reasonable thing, given need for "electric 24/7" but 8x 6v batteries in series to make 48v nominal has a bunch of electrical efficiency as well as cost advantages. You will need a good box for the batteries, vented, with a sloped lift-up lid so that you can easily reach all the terminals for watering and checking the connectors. The box should be insulated against cold and heat, perhaps below grade. The advantage of AGM or gel (I know, I know, gels are hated) is that they don't gas and can be indoors sharing your heated space. Surprise: they cost more, but if you get 10 years of low-fuss they might be worth it.

Try to avoid battery models heavier than 80#, because you, or someone, will have to lift them at some point, or provide a crane/access. 80# is a 2-man lift, yes, MEN who will be able to lift in and out of vehicles, tote to the site (with wheels!), and safely/gently place them in to their box, and after go for beer not ibuprophen/DTM and hot-packs. Find these men and treat them right.

Running a camp/cabin on 120v AC from a high-quality inverter, with some DC-DC converter backup for emergency lighting, might be just right. EnergyStar appliances are a balance between inexpensive and efficient, and with more money you can get TierIII Energy Star for really-good efficiency. Refrigeration is a relentless load, so spending more and getting the smallest acceptable refrigerator will help the whole system work well. I do fine with a 4 cubic foot refer and a 6 cubic foot freezer, but more freezer might be important for a hunting camp where you are going to wrap & freeze meat.

Lighting with LED is not a big load. Even reasonable flat-screen LED display/TV is not a huge load. Some big plasma TV's are like space heaters (~1000 Watts on and 150W standby!): AVOID on a battery-system! Class-D switching audio amplifiers are (or can be) thrifty with power, and when driving efficient horn-loaded speakers are plenty loud.

Your mention of a 10KW genset leads me to think that the purpose of the battery and inverter is to save money/fuel and wear on the genset: good thinking! An Outback inverter like a VFX3648 (or 2) can provide "almost" the same kind of power as a generator, with the exception of running a welder. Don't run welders from expensive inverters, use the genset. These type of inverters have high-current chargers that can accept lots of generator input power and rapidly charge the batteries. There will probably be a minimum run-time for the generator (enough time to get warm + some minutes like 30 minutes), so you will want to look into that and coordinate a schedule that works for you, the battery bank (maybe 40% discharged?), and the generator (big loads: pump water, run clothes washer, electric water heater, tools, welder, etc.).

Your proposed solar panel array is too small. A 500#, 300A@48v (14.6KW/Hrs to 100%DoD) battery bank needs at least a 5% panel system to trickle charge the bank. Let's call that 800 Watts (real) in December which might be more like 2KW in panels measured at STC. With these panels working, you will still run the genset once a week or so, in the winter.

Might as well get an Outback charge controller, so that it can talk to the inverter/chargers and use the same Mate.

Commentary: The generator will be best used to "Bulk Charge" the batteries, while the solar system will be best used to "top up" the battery bank. This means that when your battery is 50% discharged, the generator can run for a couple hours and get the batteries up to 85% charged, then turn the genset off and let the solar panels work all day.

Did I mention that copper is kinda expensive since 1999? Running a 48v system helps with this.

This kind of system is not a first-time DIY install. This is a job for a skilled solar contractor who happens to have 20 years of experience with happy customer lists. Owner can DIY the system maintenance (clean panels, clean terminals, oil/filter changes, monitor system, etc.) once everything works.

Cheers.

mike95490 · December 2012

Re: top up battery bank from generator

pdxr13 wrote: »

... An Outback inverter like a VFX3648 (or 2) can provide "almost" the same kind of power as a generator, with the exception of running a welder. Don't run welders from expensive inverters, use the genset. .....

Why is that ? Why not run welder off inverter ?

Vic · December 2012

Re: top up battery bank from generator

Hi Mike,

Well, I am with pdxr on this ... Would never even consider running any welder from MY inverters. Have a cheezy loud genset just for that purpose. Realize that a MIG welder may be easier on the inverters than a stick welder, but would not want to expose $6-7K in inverters to that kind of current profile.

Long ago there was a thread here from someone who blew up his inverter/s doing welding. He wanted to know where in the specs it was written that one should not/must not run welders from that certain brand of inverter. Several of us suggested that it might just be common sense.

Just my opinions ... this is a bit of an old thread. Good luck with the new OG place, Vic

top up battery bank from generator

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