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Old 02-03-2006, 12:12   #46
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Sean, my understanding of the way you want to run your battery/electrical system is that charging the batteries, and then taking them off the charger, will be a very direct and concious activity. It might even be part of a checklist in a operating log. If this assumption is correct, I don't think you would need to be overly concerned about forgetting to set an isolator switch to reparallel your batteries after charging. So splitting your bank to run on two chargers makes sense to me.

On the other hand, it seems that there could be a solution involving a relay that opens the connection between the two banks when the charger is turned on (activate relay), and closes it again when the charger is turned off (deactivate relay). This would make the whole thing automatic.

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Old 02-03-2006, 13:22   #47
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Yes, Mark...

Exactly. Daily, I will be doing a 2hr genset run, which will be used to run the AC compressor on the refer unit, charge up the batteries, and do some light housekeeping with items such as a vac or tools. This will be a daily ritual. I don't need everything to be automatic, since I am used to this type of ritual from my work on megayachts. I see this extra work as just another part of my job as a charter captain.

On occasion, we will use an electric toaster oven during a genset run for some meals that come out better with that dry heat. Of course, this will require a more staggered approach to turning on the electrical items, and may result in a 3 hour genset run.

At times, I will run the genset all day to bring the batteries up to full charge. I will try and coincide these genset runs with times that customers want to have the AC on all day at anchor. (this costs them extra)

So based on what you are saying, it seems like I could do the following:

1) Get a couple of 300-400AH rated batteries
2) Install them as batt1 and batt2 in my already configured system, which has a switch to isolate the 2 small house batteries I have in here now.
3) Hook up an Iota charger to each battery.
4) Turn the selector switch to either batt1 or batt2 to isolate them (??) This would then allow me to charge one of the two batteries without any load on it, and charge the other battery with the boat's entire DC load on it (which should be a minimal load at 5PM or so when I do my daily genset run).
5) When done the bulk phase, I would then turn off the chargers.
6) I could then return the isolator switch to "both", enabling a combined battery bank of 600-800AH to be discharged to a lower level, which is more efficient.

Seems a lot more simple looking at it as a checklist. This should work. Just have to see about that whole power correction factor issue. I sure would like to find a charger that will do that that won't break the bank. The efficiency involved would be tremendous considering the genset's waveform. (thanks again, Rick!)
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Old 02-03-2006, 13:27   #48
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Hi Sean,

I'll give you a few ideas. They are not inexpensive, though.
Check out:
Master Volt Mass 12/80 an 80A charger
Outback Power VFX2812 a 125A charger/inverter
Xantrex MS-3000 a (150?) A charger/inverter

All chargers sold into the Eueropean markets must be pfc (technically referred to as harmonic limited) in order to pass legal criteria for harmonic generation.

All chargers in the US will undoubtedly ultimately be "corrected" as well.

Because all switch-mode topologies lend themselves to being bidirectional in nature you get more bang for the buck when you buy an inverter/charger with this technology.

There are a few other chargers which you might consider...I'll get a few names after awhile.
Rick
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Old 03-03-2006, 16:19   #49
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Thanks, Rick.

Here is where I'm at right now based on everything I've learned on this thread, other threads in this section, and by talking to JackRabbit Marine over in Stamford, CT:

1) I think I understand from Rick's last post that most US chargers will already have PFC? The Iota may have it, but it is terribly inefficient.

2) The Iota 90 draws 20amps (AC Power), and I'll have 2 of them running. They draw the 20 amps "when the batteries are heavily discharged." Apparently, the 20 amp draw tapers off during bulk. That means during the bulk charge, 4.48KW will be required of my genset from time to time. This would leave NO power for anything else. I think this might mean they are NOT PFC? Terribly inefficient.

3) There is no way in the world I can run the genset less than 2 hours if I have drawn my max (250AH) out of the battery bank.

a. I will face an hour and 15mins charging time with the 90amp Iotas, but can't run the refer or any other AC devices during that time. I will also have to run the 10amp refrigeration compressor after the Iotas enter the absorbtion phase, resulting in another hour genset run.

b. I will face an hour and 40 mins charging time with the Iota 75s, but will be able to at least run a vacuum, tools or other appliances, except microwaves and toaster ovens. Then, I still have another hour of genset run time to do the refrigerator.

Some days, I will be able to get away with less, since this is all calculated for my max of 250ah daily draw. This includes things like having the entertainment center on for 3 hours, all halogens on for 3 hours, and computer on 8 hours for navigation. If I'm just sitting at anchor without customers, the draw will be much less.



So... the plan for now is to get twin Iota 75s, and hook them up directly to the batteries. I will isolate by using the existing battery isolation switch, as discussed before. One batt will have the house DC load on it while the other will charge without any load. When both make it to absorbtion, I'll turn off the chargers and crank up the refrigeration unit. I'll also put the battery switch back to "both" and maybe run my current 50amp charger to top them off a little more since the genset will be on anyway for the refer unit. During this phase of the genset run, higher amp appliances like microwaves, toasters, etc... can be run.

I'll do this at about 4pm each day, to allow for AC power during dinner prep.

Seems workable. Anyone see any glaring holes in this plan?
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Old 03-03-2006, 19:59   #50
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Yes a big hole. Stick with the biggest charger you can run. The max current required is only at max discharge of the battery. The current slowly drops away as the battery charge rises. So you want to be able to sink in as much as you can through the entire charge period. You won't be asking the full 20A from the genset for the full 1 1/4hrs. Most likely it will be 30mins or less and the load should be down to half.
Absorbtion and float charge is of very little current draw, but will take sometime to reach the float stage. This can be many hrs. You may not need to worry about those stages till back at the shore power where you can leave the charger on overnight. I don't, I sink in as much as I can in the normal charge mode and worry about absorbtion at the marina.
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Old 03-03-2006, 20:04   #51
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Quote:
Seems workable. Anyone see any glaring holes in this plan?
The amount of current you can put into the batteries depends on the state of charge. When you first start charging, you will see the full 75 or 90 amps. After some time, that will drop below the rated output of the charger because you just can't put any more in to the battery.

Consequently, you can't say "I need 120 AH and have a 75 A charger, so 120 / 75 = 1.6 hours". The actual time to charge the batteries will be greater.

It's not really a glaring hole. The only way this affects your plan is that it will take longer than you expect to charge the batteries.

I characterized the charger performance shortly after I left to go cruising. I'm going to try to attach a graph of charge current in amps vs time in seconds. I got the data by writing down the value on the ammeter now and then. The red line is a partial data set. The green line is the whole cycle to fully charged. I normally run about 2 to 2.5 hours.

I didn't realize I still had this data set sitting around, or I would have posted it earlier.

b.t.w. I run two DLS-75 units on a generator rated for 4.2 KW. That is 35 amps at 120 volts, which is the size of the fuse.


Ok, I can't attach the graph because it is bigger than 1000 bytes. Here are some sample values from the full cycle:

time amps
0 157
7 106
32 70
58 49
83 39
99 35
124 35
152 24
181 18
202 15
241 4
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Old 04-03-2006, 01:54   #52
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Mark:

You can post a jpeg immage in your photo album.
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Old 04-03-2006, 07:13   #53
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Thanks, Mark.

This is truely helpful data. Especially owing to the fact that you are on the Iotas and a genset. So how much power are you putting back into the batteries on your genset run, and how large is the battery bank? If I can understand those figures, along with your graph (or data points) I should be able to extrapolate something to my own setup.

So far, I understand you have (qty2) 75amp Iotas, a 4.2KW genset, and run for a couple hours to charge. Do you have your other house AC loads on at that time as well? (Hot water heater, any other appliances?)

It's odd, but sometimes it seems gensets do better than anticipated. I remember picking up this 5KW genset and many people on the forum were saying it wouldn't power the 2 air conditioning units I have simultaneously. As it turns out... it powers both AC units AND all my house load without even a hiccup.

So could you fill me in on the rest of your setup? Batt bank size? Other AC loads running during charging? Also, what type of batteries do you have? I'm looking at flooded Trojan T-105s. But... they suggest a 14.4V charge voltage, and the Iota can only put out 14.2V.

Looking forward to hearing more. You have this setup working well, so you are an expert in a very unusual setup. Thanks for all the help so far.
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Old 04-03-2006, 15:20   #54
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Just remember Sean,it is not what the Gen will run, it is what is required to start. Soem loads take three times the current to get them going.Once they are going, they take little to keep going.
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Old 04-03-2006, 17:30   #55
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Alan Wheeler once whispered in the wind:
Just remember Sean,it is not what the Gen will run, it is what is required to start. Soem loads take three times the current to get them going.Once they are going, they take little to keep going.
I know... I think you were one of the supporters of my 5KW genset... saying it would indeed work??

Both ACs can start simultaneously.

It really all comes down to the initial load the Iotas generate. I'll make sure I can return them to downgrade if the geny can't handle the load. I'll start out with the Iota 90s. Sure hope Mark comes back with some info on his setup. I'm going to drop the $$$ on all this stuff next week.
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Old 04-03-2006, 23:35   #56
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So could you fill me in on the rest of your setup?
Sure:

The charging graphs are photo 1787 and 1788 - click on Photo Gallery and search for "iota".

These data sets represent two sample charge cycles that I monitored when I started cruising. It looks like I'm putting about 100 to 120 AH into the battery each time I recharge. Sometimes I discharge deeper than 700 AH, but that that puts me on the steep part of the curve, so it doesn't add so dramatically to the recharge time.

I usually stop the generator when the batteries get to about 800 AH or when the charge current drops into the 20-30 A range. (Both criteria occur at about the same time.) This isn't ideal for AGM batteries, but I can put in 100-or-so AH in 90 minutes and another 40 AH in another 150 min. You have to draw the line somewhere.

Notice that the rate of charge is limited by the state of the battery, not the capacity of the charger, but that high capacity during the early part of the charge cycle takes quite a lot off the total charge time.

(I designed the system for 250 AH per day, based on a worst case power budget that included sailing 24 hours/day in cold weather. Nav lights and radio standby current really add up, as does the blower in the diesel heater. I also planned for solar/wind that could top up the batteries for the last 40-50 AH, but have not installed anything.)

The house battery is 4 of 210 AH Lifeline AGM batteries. Physically, they are mounted as two banks of two. The lower pair is mounted horizontally under the floor. The upper pair is mounted vertically in a (former) kitchen cabinet. Because of the physical separation, I have them separately fused and switched, but in practice I have a single bank of 840 AH.

I chose AGM batteries primarily because I could mount some on their end, and secondarily because they supposedly can be charged much faster than flooded cells. Lifeline says 20% faster recharge; this is toward the lower end of the claims I saw, but I suspect may be more representative of real world applications.

Flooded batteries are more tolerant of poor treatment, such as under or over charging. That doesn't imply you can just be mean to them. I had to replace my engine charging battery, I believe because the boat was delivered with the original charger set to the "gel" setting even though it had flooded batteries.

I have an Entec West 4200 generator, which puts out 35 amps. It has a transfer switch that either feeds two AC buses from two 30 A shore power cables or else feeds both buses from the generator output. One iota charger is on the house AC bus and the other is on the air conditioning AC bus.

I usually run the two Iota chargers with no other AC loads when I am charging from the generator. If I want AC power for another big load, I turn off AC to one of them. Normally, I will do this during the later part of the charge cycle when the battery charger can't make use of the full generator capacity.
For example, I once used both chargers for an hour, then used one charger and cooked a pie in the toaster oven during the second hour.

On my boat, AC is for the battery chargers, toaster oven, microwave oven, and (at the dock) space heaters. I can't recall ever trying to use a small AC load while charging from the generator.

b.t.w. The generator can run a 12000 btu and a 16000 btu air conditioner, as long as I start the bigger compressor first.
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Old 05-03-2006, 01:30   #57
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Life Saver...

Mark...


Thank you, thank you, THANK YOU!! You have saved me weeks and weeks of research, as well as probably a lot of $$ in making mistakes.

Don't have too many ways to repay you, but I'm looking for one....

It's interesting that we have nearly identical setups. The only difference is I don't have the Iotas yet, and I have just a slightly larger genset (rated 4.8KW continuous). Other than that... sounds like we have all the same gear.

Based on your data and description, I'm definitely going to pick up the Iota 90s and duplicate your setup. It seems to be working very well, and it's funny... I was even planning to have some room for solar too. I also calculated 250ah daily consumption as a maximum (radar, computer chart plotting, halogens on for 3 hours a day, entertainment center all items on 3 hours a day, etc... Typical days will likely see the same usage you see, as we will be just sitting at anchor.

Knowing I'll be able to replace the used energy in under two hours is quite a relief. I was getting a little concerned about roaring my genset for 3 hours in an anchorage. That wouldn't make for a good neighbor.

PS: I also have the twin 30 amp circuits (one for AC, one house) and will put an Iota on each as well.

Again... thanks so much for this complete and informative post. I'm glad to find someone else doing this type of thing. Proves I'm not QUITE as crazy as once thought... ha ha ha
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Old 05-03-2006, 23:26   #58
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You're welcome to my data. I know even the most rudimentary data from a real installation can give you valuable clues, even though you can't count on it to accurately predict your own results.

I wouldn't say we have identical systems, but there is some expected similarity that falls out of the similar requirements.

As a Soviet general once commented about similarities between Buran and the Space Shuttle, "I can't comment on the specific design, but I can tell you that the laws of physics are the same in the United States as they are in the Soviet Union".

Of course, Buran is so similar the Shuttle that we know some engineer was told "build me something like that", and it probably wasn't because the Soviets wanted to launch KH-11 spy satellites for the NRO.

The only thing I wonder about is the 90 amp charger vs the 75 amp charger. Since the charge rate is dominated by the battery, I wonder if you will be able to make use of the extra capacity. That depends on the acceptance rate of the battery bank you install.

The good news is that a 90 amp unit won't mind if it doesn't have to work to full capacity. It isn't like a diesel engine that gets crud in it if you don't put enough load on it.

As for repaying me, don't worry about it unless you know a source for a magic wand that installs hoses and attaches them to pipe barbs. I really could have used one of them today.
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Old 11-04-2006, 16:12   #59
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As a follow up post, everything is working very well now with two Iota 90 chargers hooked up to 450AH (@12V) of Trojan T-105's. Thank you all for helping me to select the proper equipment at a price that didn't break the bank. I am very satisfied with the setup.

I wired one Iota 90 into each of my 30amp circuits. This allows me to run both chargers and turn on an item or two during bulk charging on either 30amp circuit. More flexibility than having them both on one circuit.
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