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Author Topic: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?  (Read 5037 times)

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Offline Bill Quick

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After purchasing three AGM deep cycle batteries (110 Amp Hour rating) to add to the three batteries I already have (totaling 300 Amp Hours among them) for a bank that totals 630 amp hours, I decided that I needed some other way to charge them up besides solar panels, given that SF can go two weeks under clouds at times during the winter months.

I just bought a used but like new Honeywell 1000 watt (900 continuous) inverter generator with a 120 volt output.

How would I set this up to charge the battery bank?  How long should I expect to have to run the generator to fully charge the bank?

I know, stupid questions, but that's why they pay me the big money.  ;D
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Well, you should only charge battery banks that have batteries of the same age and type.

Here is a link to a discussion of a guy with battery issues on his boat:

http://www.morganscloud.com/2011/02/10/eleven-steps-to-better-battery-life/

Read all his entries for some good info.

Yes, I'm a physician.  No, I'm not YOUR physician.  Nothing I say here is medical advice.

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Offline Bandit5

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I'm starting to think about a battery bank for the BOL, on the basis that a generator sized to handle motor wind-ups for the major appliances (especially fridge/deep freeze) is wasting fuel the 99% of the time that those appliances aren't kicking in to high gear.  However, just thinking about a battery farm makes me start thinking about PV again, even though I can't make the math work without assuming double-triple current electricity prices for most of the next 20 years... but, on the fourth hand, there's something to be said for being "done" with an issue and not having to worry about it (outside of solar flares).

Offline oldguy52

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Bill, Don't want to rain on your parade, but that 1000 watt inverter will not likely to be able to charge all those batteries as a bank. I assume (trouble, I know) that your inverter will work similarly to my Honda 1000. My Honda will run a 110 volt battery charger at 12v@6amps, any more will kick the breaker. 6 amps against 6 batteries that big is not a very meaningful charge.

Also, when we first got our travel trailer, we used our Honda 1000 to charge the battery by plugging the trailer cord directly into the genset and charging through the trailer's inverter. Shortly later I added a second battery (these are group 27's) and the genset could not handle the amperage required anymore. That was with 2 batteries, you're talking about 6.

I hate to say it but you're probably gonna' need something bigger for a battery bank that big.
O.G.

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Offline Bill Quick

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Thanks, folks.  This guy may offer a solution.  Anybody want to do a sanity check on what he says?

http://www.fridge-and-solar.net/gen_charge.htm

Here's a possible candidate for a battery charger:

http://www.iotaengineering.com/pplib/dls90spec.pdf

A less powerful charger:

http://sunelec.com/index.php?main_page=product_info&cPath=26&products_id=129
« Last Edit: March 03, 2011, 08:04:38 AM by Bill Quick »
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Offline razorbacker

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Looking at the price of deep cycle batteries leads me to ask...What happened to the price of lead-acid batteries?  I recently had to replace the battery on my Jeep and was depressed to note that I paid roughly 50% more than my last battery bought four years ago.

Back in the '60s we used to use those huge batteries from Cat dozers to power the lighting on our houseboats.  These big boys were about ten times the size of a car battery (and required two grown men to move them around easily) but held enough juice that the lights, radio, etc. could be used as needed during the night and recharged from a little homemade generator using a lawn mower engine and the alternator or generator from a car.

Offline Bill Quick

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Just to see if I am getting the basic principles right:

1. If my battery bank is 600 Amp Hours

2.  And I don't want it to go below 50%, or 300 Amp Hours

3.  Then I would want to be able to charge 300 Amp Hours as cheaply as possible

4.  So I could hook up a 30 Amp AC-DC 12 volt battery charger

5.  To a gasoline generator/inverter outputting 1000 watts AC

6.  And add 300 Amp Hours of charge to the battery bank over a period of 10 hours of genny operation?

Does that summary hit all the high notes correctly?

« Last Edit: March 03, 2011, 01:56:31 PM by Bill Quick »
"You can get a lot farther with a kind word and a gun than a kind word alone."  --   Al Capone

Offline oldguy52

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"4.  So I could hook up a 30 Amp AC-DC 12 volt battery charger

5.  To a gasoline generator/inverter outputting 1000 watts AC"


No, it won't work. Your 1000 watt inverter will not run a 30 amp charger, no matter what the math says. It might run 8 amps, it won't run 10 amps. I have two battery chargers that I have tried to use with my 1000 watt inverter. One is 6 amp, the other is 10. If the charge on the batteries I'm trying to charge is down at all, the 1000 watt inverter will not run the 10 amp charger, it'll run the 6 amp charger fine. If you want to run a 30 amp charger I would expect you'll need a genset somewhere north of 3000 watt.
O.G.

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When one finds himself living in interesting times, it is prudent to become as uninteresting as possible.... Me, 2011

Offline razorbacker

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How do the folks at Home Depot and Lowes charge those electric fork lifts and power jacks every night?

I've been in the back rooms; they have this big old battery charging system mounted to the wall back by the returns clerk.  I was just never interested enough to ask how it worked.

Offline Bill Quick

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Probably off of wall current, Razor, which I could easily do, too.

The point of this exercise, though, is charging the batteries when wall current is unavailable.

"You can get a lot farther with a kind word and a gun than a kind word alone."  --   Al Capone

Offline razorbacker

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Probably off of wall current, Razor, which I could easily do, too.

The point of this exercise, though, is charging the batteries when wall current is unavailable.

Right.  I get that.  My point is, there is a way to split that power into usable chunks so as not to burn out the batteries.

Back when people let kids play with power tools and such, my father watched me make a couple of those 'B&S engine+generator+battery' setups without comment.  It was not a big financial deal; I had a junkyard of batteries to chose from and they were just scrap value anyway.  Finally he could stand it no longer and said, 'Son, they put those voltage regulators on cars for a reason, you know.'

The problem was not generating enough electricity, the problem was putting just enough power into the battery so as not to 'burn it up'.  I don't think it would matter how the electricity was made; it can come from a spinning coil of copper wires in a magnetic field, or it can come from sunlight on solar cells.

This is like my 'Aeromotor' posts.  I know that these windmill things were once used to charge battery banks to provide electricity to off-the-grid homes.  I've actually seen the remnants of such a system.  What I have never seen is a working system.

http://nebraskawindandsolar.com/history.aspx

Quote
In the 1970s many people began to desire a self-sufficient life-style. Solar cells were too expensive for small-scale electrical generation, so some turned to windmills. At first they built ad-hoc designs using wood and automobile parts. Most people discovered that a reliable wind generator is a moderately complex engineering project, well beyond the ability of most romantics. Some began to search for and rebuild farm wind generators from the 1930s, of which Jacobs Wind Electric Company machines were especially sought after. Hundreds of Jacobs machines were reconditioned and sold during the 1970

This is not a new quest.  We have generations of experience to draw from, and their failures and successes to guide us.  I'd guess that the answer is actually going to be some type of solar cell, but what type?




prepperjim

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I ran across a link to this charger in another forum:
http://www.amazon.com/exec/obidos/ASIN/B000JFLSL6/themousepad/

This looks like it might be good for your application.

To me, we need a way to get an initial charge into the battery when on the grid then maintain it via solar, wind or even bicycle power if the grid goes down. That is what I am striving for.

My goal is to have 300W of solar, some sort of wind power available (as if my wife would ever let me install it!) and 300 amp-hours of battery storage. Of course, the amount of energy available to me will be whatever can be generated via solar, but having extra storage never hurts to make it through the days without sun or wind. 300W really is not that much, but it will keep some lights on! 

Offline AuricTech

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #12 on: November 03, 2012, 10:41:14 PM »
As I begin to plan the construction of an off-grid permanent Casa AuricTech, this same issue of how to maintain power in case of extended poor weather has weighed upon my mind.  The best solution I've come up with is to have a transfer switch that would allow me to use a propane-fueled generator at night, when electricity use is lowest.  That would prevent draining my solar-powered battery bank when there is no available sunlight, thus allowing my battery bank to recharge fully when The Big Heat Tab in the Sky can shine upon my PV array.  8)  This solution strikes me as simpler than trying to use a generator to keep my battery bank charged in case of extended poor weather.

Thoughts, anyone?
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Offline Suburban

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #13 on: November 04, 2012, 09:27:52 PM »
Thanks, folks.  This guy may offer a solution.  Anybody want to do a sanity check on what he says?

http://www.fridge-and-solar.net/gen_charge.htm

He obviously is from a part of the world where mains power is 240 volt 50 Hz.  For us in the USA most of his comments still apply as long as you understand that our mains power is 120 volt 60 Hz.  Chargers in our part of the world are designed to run on nominal 120 volt 60 Hz power.

The Xantrex (one of the better brands of inverters and chargers) TrueCharge he mentions has now been replaced by the TrueCharge2 which has a number of advantages over the average charger.  First, it has multi-stage or "smart" charging which lets the battery charge most of the way at a very high charge rate, and then automatically slows down as the battery reaches full charge.  Second, because it is "power factor corrected" it is an easy load for a generator to drive.  This is a particular issue for inverter generators, which can't deliver momentary surges of power a lot higher than their nominal maximum power output.  Last, this charger is UL Listed, which means it has passed the UL safety testing and will not burn your house down or cause the batteries to explode.

UL Listing, by the way, says nothing about how well a given product works, only that it will not kill you or burn your house down.  UL stands for Underwriter's Laboratory and was founded by insurance companies trying to determine what products were safe to let their customers use.  As long as you understand that UL Listing is not a rating of "quality" you will do fine.

Here's a possible candidate for a battery charger:

http://www.iotaengineering.com/pplib/dls90spec.pdf

I do not think that is a good candidate.

1) It has an "inrush current" of 40 amps.  That means it would need a generator with a 4800 watt or higher surge rating to start the charger.
2) It has a maximum current draw of 21.8 amps.  That means it should be used with a generator with a 2616 watt or higher continuous power rating.  Your little generator is too small to drive this charger.
3) It is not UL Listed.  To me that is a red flag that there is something about this charger that may not be totally safe.

A much better choice would be the 20 or maybe 40 amp versions of the TrueCharge2 charger.  Your generator with a 900 watt power output should be able to easily power the 375 watts needed by the 20 amp TrueCharge2, and might even be able to power the 750 watts needed by the 40 amp TrueCharge2 depending on how good a job of controlling the inrush current the power factor correction circuitry does.


Offline Suburban

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #14 on: November 04, 2012, 09:52:48 PM »
Just to see if I am getting the basic principles right:

1. If my battery bank is 600 Amp Hours

2.  And I don't want it to go below 50%, or 300 Amp Hours

3.  Then I would want to be able to charge 300 Amp Hours as cheaply as possible

You want to charge as fast but no faster than the batteries (hopefully identical) can accept.

4.  So I could hook up a 30 Amp AC-DC 12 volt battery charger

A charger that is delivering a charging voltage of roughly 15 volts at 30 amps is outputting 450 watts.  A modern switching type charger will have an efficiency of roughly 80% so an input power of 563 watts is needed to deliver 450 watts out.

Your battery bank is 600 amp/hours which means a charge rate of 20 hours (nice safe charge rate) means a charge current of 30 Amps.  With most batteries you do not want to exceed a charge rate of around 10 hours or in this case a charge current of 60 amps.

You can charge at full rate until your batteries are at about 80% of full charge.  After that the charger rate needs to slow way down.  So with a 30 amp charger you will be able to charge a full rate for roughly 6 hours (from 50% charge starting point until around 80% charge) and then the smart charger will start slowing down the charge rate to protect the batteries.  It may take an additional 6 to 10 hours to fully charge the battery bank.

5.  To a gasoline generator/inverter outputting 1000 watts AC

With a quality charger, you can probably charge at a maximum rate of 30 or 40 amps using your generator.

6.  And add 300 Amp Hours of charge to the battery bank over a period of 10 hours of genny operation?

I think 12 to 16 hours would be better to plan on.

« Last Edit: November 04, 2012, 10:06:48 PM by Suburban »

Offline Suburban

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #15 on: November 04, 2012, 10:04:01 PM »
No, it won't work. Your 1000 watt inverter will not run a 30 amp charger, no matter what the math says. It might run 8 amps, it won't run 10 amps.

Inexpensive battery chargers have a brute force power supply that can require an inrush current to start them that is many times what the running current is.  I suspect that is why your inverter generator chokes on running the 10 amp output charger.  Probably an old fashioned noisy generator would fare better since it is better able to deliver a huge current surge for a split second to start the charger than an inverter generator can.

Better would be to use a higher tech charger than does not require a massive current surge to get started.


Offline Bill Quick

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« Last Edit: November 05, 2012, 12:47:41 AM by Bill Quick »
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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #17 on: November 05, 2012, 07:22:31 AM »
I used to have Trace at the old house, and put Xantrex in the Estancia. 
The better brand these days seems to be Outback...

Xantrex (formerly Trace) used to be quite good....over the last 10-15 years though, they've gotten pretty consumer grade, and not in a good way.

After a couple of very expensive failures (including a runaway charger that fried a battery bank) I replaced the Xantrex with Outback.  So far, so good.
Yes, I'm a physician.  No, I'm not YOUR physician.  Nothing I say here is medical advice.

Do I treat Glocks like I treat my lawn mowers?  No, I treat them worse.  I treat my defensive weapons like my fire extinguishers and smoke detector - annual maintenance and I expect them to work when needed

Offline Suburban

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #18 on: November 05, 2012, 12:03:29 PM »
What about this one, Suburban?

http://www.progressiverc.com/media/PM3Manual.pdf

http://www.progressiverc.com/powermax-pm3-45.html

Hmmm...

The HTML page says:

"A great entry-level power supply, the PM3-45 offers enough power at 600 watts and 45 amps to run all but the biggest chargers, or it can even charge lead-acid batteries directly!"

In other words it is a power supply and is intended to drive a battery charger, although it could be used as a very basic charger by itself.

The pdf manual by contrast says this is a 3 stage battery charger.  The pdf manual says this is UL Listed which is good. 

It also says it is registered with the FCC as a "Class B digital device" which is intended for use only on commercial environments and not residential.  A Class A digital device is intended for use in a residential setting.  The difference is in how much radio frequency (RF) garbage the device emits which interferes with radio and TV reception.  Class A devices do not emit as much RF garbage as Class B devices.  So this device may interfere with RF communications (radio, TV, ham, CB, cell phones, etc.) near it.

The steady state power draw of this unit is too high for your generator.  The manual says it needs 9.5 amps of 120 volts as power input.  That equals 1140 watts, and your generator is only rated for 900 watts.  The smallest model in this line with 35 amp DC output requires 7.4 amps of 120 volt AC input or 888 watts which is right at the maximum power of your generator.

The biggest problem, however is that there is no mention of either power factor correction (which is more expensive to make) or the amount of inrush current it draws.  Since your generator can only deliver peaks of 1000 watts or 8.33 amps at 120 volts, you must find a charger that has a maximum inrush current at startup of under that amount.  It seems highly unlikely that this charger would work with your generator.


Offline xtron

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #19 on: November 05, 2012, 05:22:41 PM »
if you can live without the electricity for a while (and if the batterys are near dead, you have no choice).....you could disconnect the batterys from the bank and charge them one at a time...labor intensive,(kinda) and time consuming, but better than being without till the sun comes out and recharges you.

Offline Bill Quick

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Re: How Do You Set Up A Generator to Charge a Bank of AGM Deep Cycle Batteries?
« Reply #20 on: November 05, 2012, 08:37:30 PM »
I think I'm going to go with the Xantrex Truecharge2 40 amp. 
"You can get a lot farther with a kind word and a gun than a kind word alone."  --   Al Capone


 

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