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Old 01-25-2014, 10:55 AM   #29
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If you use deep cycle batts, as the majority of us do, charging at a high amperage rate is self defeating! Deep Cycle batts are not to be charged like a start batt, but at around a C20 to C10 rate, or even below.

Anyone that thinks a high AMP charge is good for the DS batts, I'd suggest a little study. This is if we are talking wet cell batts like the Trojan's, or the like, in popular use.

If using newer style sealed batts, then a higher AMP charge (I understand) May be used.

But, in either case, if you don't really know much about battery's as used in an RV, there are numerous places on the Internet, and from professional, informed individuals/companies. Much better than mouth to ear information from individuals.

All IMHO

Ed
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Old 01-25-2014, 11:04 AM   #30
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Originally Posted by Ed-Sommers View Post
If using newer style sealed batts, then a higher AMP charge (I understand) May be used.
See the data below from lifeline AGM batteries.

The 27T batteries can take a charge current of 250 amps

The 8D size batteries can take charge current of 600 amps

For wet cells here is yet another reference that up to 25% of C is acceptable during the "bulk" phase.

"Maximum amperage that batteries can accept during the Bulk Phase of the charging cycle vary depending on battery chemistry: flooded batteries can accept a charge rate of up to 25 percent of C; gel batteries have a higher acceptance rate of as much as 30 percent; AGM batteries accept the highest charging amps"

http://www.westmarine.com/webapp/wcs...g#.UuPxS388KK0
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Old 01-25-2014, 11:33 AM   #31
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The research seems clear that modern day deep cycle batteries are perfectly happy with higher charge currents during the "bulk" charging phase than some people remember from the past. Of course, the charger should implement a modern 4 stage charging algorithm, and the charge amps taper off when the battery is not in the "bulk" phase.

This whole discussion came about from the idea of using a small portable generator to charge batteries vs. using the more powerful onboard generator. Fuel savings dictate that in this scenario it is more prudent to charge the batteries at the fastest rate they safely accept in order to minimize generator run time. When you are connected to shore power, you can set your charger to charge at a lesser rate if you want to, because you have no timetable to satisfy.

:-)
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Old 01-25-2014, 11:33 AM   #32
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I think the whole notion of more is better when charging is just marketing 'look at me' crap.

If you're camping and you're going to be somewhere long enough to deplete your house batteries what the heck does it matter if it only takes 4 hours to recharge them instead of 8 hours if you're not going anywhere for a few days?

I'd rather give them a longer slower charge, getter a better charge, and have the batteries last a longer time before I need to spend a pile of money to replace them.
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Old 01-25-2014, 11:35 AM   #33
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I think the whole notion of more is better when charging is just marketing 'look at me' crap. If you're camping and you're going to be somewhere long enough to deplete your house batteries what the heck does it matter if it only takes 4 hours to recharge them instead of 8 hours if you're not going anywhere for a few days? I'd rather give them a longer slower charge, getter a better charge, and have the batteries last a longer time before I need to spend a pile of money to replace them.
This whole discussion came about from the idea of using a small portable generator to charge batteries vs. using the more powerful onboard generator. Fuel savings dictate that in this scenario it is more prudent to charge the batteries at the fastest rate they safely accept in order to minimize generator run time. When you are connected to shore power, you can set your charger to charge at a lesser rate if you want to, because you have no timetable to satisfy.
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Old 01-25-2014, 06:43 PM   #34
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This whole discussion came about from the idea of using a small portable generator to charge batteries vs. using the more powerful onboard generator. Fuel savings dictate that in this scenario it is more prudent to charge the batteries at the fastest rate they safely accept in order to minimize generator run time.
Yes, I'm aware of that. However, I suspect that a 6k Onan QD genset is less fuel efficient than a 1k Honda genset.

That being the case, the little Honda is better from both a fuel efficiency and charging point of view.
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Old 01-25-2014, 07:24 PM   #35
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Yes, I'm aware of that. However, I suspect that a 6k Onan QD genset is less fuel efficient than a 1k Honda genset. That being the case, the little Honda is better from both a fuel efficiency and charging point of view.
Amps matter. I looked up specs for several inverter/chargers, and for them to be able to bulk charge at 160 amps, they require minimum 15 - 20 amps @ 120volts. The EU1000i maxes out at 7.5 amps.

Therefore the charger will need to be programmed to cut the charging current WAY BACK if it's only powered by the little EU1000i....and then the batteries will take much longer to charge.....meaning the little generator has to run for a much longer time.

The big Onan also has inverter technology, so it only runs at the RPM required for the load.....however in this case, the charger is programmed to deliver its maximum charge amps....which charge the batteries much quicker.....and the Onan completes it's task with much less runtime than the little honda. End result is no (or very little) cost savings from fuel between the two scenarios.

Here is an analogy..... If you want to move the furniture and belongings in your house you could use your pickup truck and make like 15 trips -OR you can use a semi-tractor trailer to move it all in one load. I will bet you that the one semi-tractor trip will use less fuel than your pickup truck making 15 round trips to do the same amount of work.
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Old 01-25-2014, 07:45 PM   #36
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Regardless of the DC capacity of the charger/converter, the flooded lead acid battery won't accept much more than about 10% of it's rated capacity as charge current. A 400A-hr bank would charge initially at about 40A...which would load up the genny (regardless of it's rating) at about 700Watts / 5.8A Ac. Also, almost 40% of the charge time is at a much lower current as the battery passes 90% state of charge. You can safely stop the charge at this point as long as you do a full charge every 2-4 weeks (and equalize twice a year).


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Forgot to add that the fuel savings are significant vs the Onan. Onan is about 0.5 to 0.6 gph (gallons per hour) with up to about 1/2 load and around 0.9 to 1.0 gph at full load. If it's running at all it is using at least 0.5 gph

The Honda 2000 will use about 0.15 gph running normal loads in my RV - one TV/lights/refrigerator(RV type) and RV charger/inverter set to high charge rate.
Exactly what I was talking about, and exactly my experience.

A 1k Honda will charge the batteries completely on 1 gallon of gas, the Onan will burn far more.

My C has a 4k Onan built in, aside from the huge difference in noise between the two, the 1k Honda charges the house batteries far more efficiently than the Onan.

While I understand your example, it seems a more appropriate example would be, my pickup is more efficient getting 50 pounds of groceries than a tractor trailer.
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Old 01-25-2014, 09:01 PM   #37
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Exactly what I was talking about, and exactly my experience. A 1k Honda will charge the batteries completely on 1 gallon of gas, the Onan will burn far more. My C has a 4k Onan built in, aside from the huge difference in noise between the two, the 1k Honda charges the house batteries far more efficiently than the Onan. While I understand your example, it seems a more appropriate example would be, my pickup is more efficient getting 50 pounds of groceries than a tractor trailer.
Are you using the same charger in both scenarios ? What size and capacity battery bank? How many hours is each generator running?

The only way your example wins in favor of the honda, is if your battery bank is small, your charger is of low capacity, and or your batteries are not drained very much.....which all makes sense when you say you have a class C RV

The charger is charging at a slow rate (because it is a small charger) and your Onan is a fixed RPM (non-inverter) generator....meaning the extra amps from the Onan are getting wasted.

BUT

If the battery bank is large - say eight 6 volt AGM type batteries (combined 800 ah capacity) and say the charger is capable of 160 amps in the bulk phase, and the generator is a 7.5k Onan quiet diesel with inverter technology, then it is far more efficient to use the big generator for a couple of hours......the honda running at its max load would run far longer and consume more fuel in the process.
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Old 01-26-2014, 08:10 PM   #38
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Are you using the same charger in both scenarios ? What size and capacity battery bank? How many hours is each generator running? The only way your example wins in favor of the honda, is if your battery bank is small, your charger is of low capacity, and or your batteries are not drained very much.....which all makes sense when you say you have a class C RV The charger is charging at a slow rate (because it is a small charger) and your Onan is a fixed RPM (non-inverter) generator....meaning the extra amps from the Onan are getting wasted. BUT If the battery bank is large - say eight 6 volt AGM type batteries (combined 800 ah capacity) and say the charger is capable of 160 amps in the bulk phase, and the generator is a 7.5k Onan quiet diesel with inverter technology, then it is far more efficient to use the big generator for a couple of hours......the honda running at its max load would run far longer and consume more fuel in the process.
I think you need to read the specs on the Honda. It has a 0.6 gallon tank and will run at it's rated load for 3.8 hours on that much fuel.

That's 6 hours and 20 minutes on one gallon of gas. A 6k Onan QD genset burns 0.4 gallons per hour at half (3 kW) rated load, or 2.5 hours on one gallon of diesel. Never mind the price difference between gas & diesel, we're just talking volume here.

Are you saying a 2.5 hour 'bulk charge' will do the same as a 6.66 hour charge at a lower rate?

I suspect the batteries would like lower charge for a 266% longer charge at a lower rate better.
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Old 01-26-2014, 09:33 PM   #39
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I think you need to read the specs on the Honda. It has a 0.6 gallon tank and will run at it's rated load for 3.8 hours on that much fuel. That's 6 hours and 20 minutes on one gallon of gas. A 6k Onan QD genset burns 0.4 gallons per hour at half (3 kW) rated load, or 2.5 hours on one gallon of diesel. Never mind the price difference between gas & diesel, we're just talking volume here. Are you saying a 2.5 hour 'bulk charge' will do the same as a 6.66 hour charge at a lower rate? I suspect the batteries would like lower charge for a 266% longer charge at a lower rate better.
3.8 hours = 228 min

228. X
------- = ------
0.6. 1

0.6X = 228

X = 228/0.6

X= 380

380 minutes / 60 = 6.33 hours

900 watts / 14volts = approx 64 amps. ( most generators cannot sustain their max rated output continuously. 800 watts would probably be more representative of real world)

64 amps bulk charge x 6.33 hours = 405 amp hrs. Using honda


If the charger can supply 160 amps bulk charge rate x 2.5 hours = 400 amp hrs Using Onan


The Onan is hardly breaking a sweat, but the little Honda is running at max load......in this scenario it's even.
If I'm right that 800 continuous watts is more realistic for the Honda, than it's easy to see the Onan wins.
If I pick a charger capable of even higher charge rate, the Onan wins by a greater margin.

Not hard to see that the lifespan of the little Honda will be shortened by constantly running at wide open throttle,
and not really any fuel savings.
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Old 01-27-2014, 07:08 AM   #40
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First: forget the 12 volt jack on the genny, not worth the time it takes to hook it up.

IF your converter is a plug in model.. I would plug JUST IT into the Honda and use an inverter to run Televisions and such.

If you need more (Say microwaving) Fire up the Onan or whatever other generator you have for that.

I'd love to do that using my Genrac 1000. but alas. it grew legs and walked off.
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Old 01-27-2014, 07:30 AM   #41
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If the charger can supply 160 amps bulk charge rate x 2.5 hours = 400 amp hrs Using Onan

If I pick a charger capable of even higher charge rate, the Onan wins by a greater margin.

160 amps from a stock inverter/charger? Really? I can't recall seeing many over 100 amps, and even then not by much. I certainly can't find any online.

We were talking about the unit in a persons m/h, not some hypothetical 'we can build this' exercise.
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Old 01-27-2014, 08:15 AM   #42
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160 amps from a stock inverter/charger? Really? I can't recall seeing many over 100 amps, and even then not by much. I certainly can't find any online. We were talking about the unit in a persons m/h, not some hypothetical 'we can build this' exercise.
When I started my research, I looked up some sample units and worked from "real world" numbers.

The first link I went to is for the Magnum ME series inverter/chargers.

Look at the specs below. The ME2512 can charge at 120 amps and the ME3112 can do 160 amps.

From Xantrex, the Freedom SW 3012 can do 150 amps, and the Freedom 458-25 can do 130 amps.

From Tripplite , the RV3012OEM can do 140 amps
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