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Old 09-26-2011, 09:00 AM   #1
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1986 25' Sovereign
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Coverter & DC Electrical Load Qs

Having suffered a battery failure, I have decided to update my electrical system. In the process, I have a few Q's that I hope others can shed some insight on:

1. What is a realistic actual DC maximum load? I know that my furnace fan draws about 6 amps and I have switched over to LED lamps to reduce energy use; I guess that my real question concerns the refrigerator and pump. Has anyone measured what a Dometic refrigerator control board requires when it is operating on propane? My gut feeling is that the maximum draw for the DC systemwould be in the 15 or 20 amp range, I just don't know and would prefer to rely on some experience.

2. Goning along with number 1 above, What is the minimum converter size that I should consider? I currently have a 55 amp Intelipower (?) that is 7 or so years old - I added the "Wizzard" about 2 years ago to get multiple stage charging. It works very well and is a definite improvement over the much heavier Univolt. But my thinking is that "smaller may be better" - a lower charging current may be kinder to my batteries. Further, an overnight charge at 10 amps should bring even discharged batteries back up to a reasonable level. I don't really understand how the multiple stage converters work - even when I have been plugged in for a week mine ramps up to the higher voltage periodically. Can a newer converter ber set to just stay at the "float" level?

3. Can a converter be used without a battery in the system, that is connected on the "house" side of the battery disconnect switch?

4. My AS seems to have some sort of automatic circuit breaker on each battery's positive lead; are these necessary and what do they protect against?


A bit of background: After reading many posts here I have decided to go with 2 12 volt "deep cycle" (at least that is what they claim to have sold me) marine batteries. I was originally inclined toward series wired 6 volt golf cart batteries but decided against it because they would have required a modified battery box, weight and lack of ready availability. Also, the series wiring would have left no redundancy.

I am also installing a "4 way" marine switch in place of my battery disconnect. That way I can charge in parallel if I wish while running on individual batteries while dry camping. My wife and I spend a fair amount of time boondocking, separate batteries should give us some warning as to head for a "civilized" camp site.

Thanks for your help - time to go fix the rotted floor (ugh!) I found under the sofa when installing the switch.

Whit Nash rwnash@charter.net
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Old 09-26-2011, 09:13 AM   #2
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Originally Posted by rwnash View Post
Having suffered a battery failure, I have decided to update my electrical system. In the process, I have a few Q's that I hope others can shed some insight on:

1. What is a realistic actual DC maximum load? I know that my furnace fan draws about 6 amps and I have switched over to LED lamps to reduce energy use; I guess that my real question concerns the refrigerator and pump. Has anyone measured what a Dometic refrigerator control board requires when it is operating on propane? My gut feeling is that the maximum draw for the DC systemwould be in the 15 or 20 amp range, I just don't know and would prefer to rely on some experience.

2. Goning along with number 1 above, What is the minimum converter size that I should consider? I currently have a 55 amp Intelipower (?) that is 7 or so years old - I added the "Wizzard" about 2 years ago to get multiple stage charging. It works very well and is a definite improvement over the much heavier Univolt. But my thinking is that "smaller may be better" - a lower charging current may be kinder to my batteries. Further, an overnight charge at 10 amps should bring even discharged batteries back up to a reasonable level. I don't really understand how the multiple stage converters work - even when I have been plugged in for a week mine ramps up to the higher voltage periodically. Can a newer converter ber set to just stay at the "float" level?

3. Can a converter be used without a battery in the system, that is connected on the "house" side of the battery disconnect switch?

4. My AS seems to have some sort of automatic circuit breaker on each battery's positive lead; are these necessary and what do they protect against?


A bit of background: After reading many posts here I have decided to go with 2 12 volt "deep cycle" (at least that is what they claim to have sold me) marine batteries. I was originally inclined toward series wired 6 volt golf cart batteries but decided against it because they would have required a modified battery box, weight and lack of ready availability. Also, the series wiring would have left no redundancy.

I am also installing a "4 way" marine switch in place of my battery disconnect. That way I can charge in parallel if I wish while running on individual batteries while dry camping. My wife and I spend a fair amount of time boondocking, separate batteries should give us some warning as to head for a "civilized" camp site.

Thanks for your help - time to go fix the rotted floor (ugh!) I found under the sofa when installing the switch.

Whit Nash rwnash@charter.net
# 1. The maximum depends on what all you have turned on. You will have to calculate that since you have modified the system.

# 2. 55 amp converters are the optimum that you should use. They charge at a varying rate, so that overcharging is never an issue, unless the converter has a failure.

# 3. Never use a converter without a battery.

# 4. Those 12 volt circuit breakers are an "absolute" must. They protect the wiring from overloads in the case of a short. To remove them, would be hazardeous in the case of a short, as more than likely a fire would start.

Andy
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Old 09-26-2011, 11:04 AM   #3
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Quote:
Originally Posted by rwnash View Post
Having suffered a battery failure, I have decided to update my electrical system. In the process, I have a few Q's that I hope others can shed some insight on:

1. What is a realistic actual DC maximum load? I know that my furnace fan draws about 6 amps and I have switched over to LED lamps to reduce energy use; I guess that my real question concerns the refrigerator and pump. Has anyone measured what a Dometic refrigerator control board requires when it is operating on propane? My gut feeling is that the maximum draw for the DC systemwould be in the 15 or 20 amp range, I just don't know and would prefer to rely on some experience.
Fridge draw is negligible for converter sizing most of the time (less than 1 amp) with peaks as high as maybe 3a during ignition.

6a seems low for the furnace, though possible many draw more; mine draws almost twice that.

Water pump depends on the pump, stock one is probably no more than 10a but the newer variable speed ones can draw 15-20a.

The realistic max DC load will vary from trailer to trailer. From a design standpoint you would want to consider the situation where all the lighting (except closet and exterior compartment lights) is in operation, plus the furnace, water pump, and any 12v electronics you may have, such as a laptop, audio system, or TV. There's no way to know for sure aside from measuring it, but typically it's 40-60 amps.

Quote:


2. Goning along with number 1 above, What is the minimum converter size that I should consider? I currently have a 55 amp Intelipower (?) that is 7 or so years old - I added the "Wizzard" about 2 years ago to get multiple stage charging. It works very well and is a definite improvement over the much heavier Univolt. But my thinking is that "smaller may be better" - a lower charging current may be kinder to my batteries. Further, an overnight charge at 10 amps should bring even discharged batteries back up to a reasonable level. I don't really understand how the multiple stage converters work - even when I have been plugged in for a week mine ramps up to the higher voltage periodically. Can a newer converter ber set to just stay at the "float" level?
Batteries won't be damaged by excessive charge current unless you exceed 1/5 the amp hour capacity, so if you have two batteries that are 100 amp hours each you should be good up to at least 40 amps. Temperature compensated chargers sometimes charge at 1/4 the amp hour capacity since there is less risk of thermal runaway. I doubt if your setup ever exceeds 40 amps of charge current. You could measure.

Quote:
3. Can a converter be used without a battery in the system, that is connected on the "house" side of the battery disconnect switch?
It depends on the converter. Intellipower converters don't require a battery.

Quote:

4. My AS seems to have some sort of automatic circuit breaker on each battery's positive lead; are these necessary and what do they protect against?
They are there primarily to protect against a short in the wiring between the battery, the breaker/fuse block, and the converter. I would consider them necessary. Some other forum members have said that the fault current from a fully charged battery is enough to weld the contacts on the typical automotive-style breakers and have upgraded either to large fuses or to marine breakers. There are also some people who believe that the connection between the negative terminal on each battery and ground should be fused instead so that there is fault protection for the full length of the positive battery cable.
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Old 09-27-2011, 01:13 AM   #4
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Whit,
For a 25 foot unit I recommend a 45 to 60 amp converter/charger. With one battery, the 45 is fine, two or more I would consider a 60. Some go wild on the DC side with large battery banks and a 75 could be the answer but not usually. You would need to pull 4 AWG to go that high and most people that do it don't need to.
There is no "optimum" except Airstream only uses one unit these days and its the Parallax 55. Started with the 7455 a few years ago and now the 7355 power center. Both are single stage units that do not vary the voltage. Airstream has not jumped onboard with multi-stage charging yet for some reason. What you need is a multi stage unit. Iota, Powermax Boondocker, PDI all do this.
With a modern switching unit as with all modern converters (Including the Parallax) YOU DO NOT NEED a battery for them to work correctly. They have built-in filtering.
For the DC wiring, yes it should be protected from the battery and usually already is. Airstrem has always been good with fusing the battery leads. A fuse or resetable CB does the same thing.
This same concept applies to Vintage owners except they might also need a DC fuse board to complete the upgrade as older Univolts sometimes had them integrated into one end of the unit. Still an easy upgrade.
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Old 09-27-2011, 06:53 AM   #5
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Originally Posted by rwnash View Post
I added the "Wizzard" about 2 years ago to get multiple stage charging.
One point of clarification here - my understanding is that your converter had the multiple-stage charging all along. The Wizard just allows you to (a) see what mode it's in (via the blinkenlight) and (b) change that mode manually if you desire.

I got the Wizard with my Intellipower converter in 2008 for the B190, but I don't think I ever used the button. It was nice to know what mode it was in though, and kind of amusing to see it in storage mode while I'm out camping.
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Old 09-27-2011, 06:57 AM   #6
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Hi Bob,
Yes, it is fine to use our converters as a power supply without a battery attached. The IQ4 will not sense a battery voltage so it will simply remain in the float stage, (13.6v).

Let me know if you have further questions.

Jay Settlemyre
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IOTA Engineering Emergency Fluorescent Ballasts, Emergency Lighting Inverters, and AC/DC Power Converters
1-800-866-4682 ext 160

-----Original Message-----
From: Robert Crosse [mailto:xxxxxxxxxxxxxxxxx]
Sent: Thursday, August 25, 2011 10:51 AM
To: John Kehm
Subject: IOTA IQ4 question

John,

I have recently purchased an IQ4 55a as an upgrade for our Airstream Classic. My question..Is it safe to use the IOTA to supply 12v when the batteries are removed during storage? I always insulate the the cables so no possibility of a short.

Bob
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Old 09-27-2011, 09:56 AM   #7
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Thanks everyone for the replies. I was removing rotted floor yesterday afternoon; about turned the corner and will start replacing it today.

I realize that current draw is very trailer specific - I guess I'll have to invest in an accurate DC meter and spend the time to sort it out. We don't have any electonic toys (other than a radio) or inverter and I have been replacing lights with LEDs. Also, have removed compartment lights after one was left on accidently - new motto: "If it is not there, it con't break or cause trouble" But it looks like my wiring and dual batteries will be adequate for my needs.

My question about converter size was propted by two factors. First, I thought that I might need to replace it to get a smarter unit and second, that I needed a smaller unit to avoid over charging. I opted for 75 AH size 24 batteries as they were a little lighter and more common - also the original batteries were satisfactory until they failed. (Somewhere I read that you did not want to go over AH/10. ) I really don't understand what the "Wizzard" is doing all the time - I may leave it just for amusement. So, bottom line I'll probably keep the 55 amp Intelipower until replacement is otherwise indicated.

My "converter alone" question was prompted by my "4 way swithch" installation; I plan to install the converter output to the "common" terminal along with the "house" load from the circuit panel. Normally at least one battery will be connected - I wondered what would happen if an error was made and the batteries were turned off while the trailer was on shore power - I don't want to burn up some expensive circuit boards, nor do I want to design/build some complicated two switch interlocking system.

My unit has a circuit board panel behind the sofa - thus all the loads are protected. While I have not had any problem with the "battery breakers" I was wondering about removing them as part of the rewiring for the 4 way switch; i.e. to eliminate some wire length, extra terminals and something else to go wrong. Base on the advice offered they will remain; if relacement is indicated in the future I'll investigate marine fuses or breakers.

Again, thanks for all the help and advice. Hope to get the old girl back on the road in time for fall colors in northern Michigan. Time to mix some epoxy and have at the floor!

Take care,

Whit Nash
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Old 09-27-2011, 10:40 AM   #8
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One point of clarification here - my understanding is that your converter had the multiple-stage charging all along. The Wizard just allows you to (a) see what mode it's in (via the blinkenlight) and (b) change that mode manually if you desire.

I got the Wizard with my Intellipower converter in 2008 for the B190, but I don't think I ever used the button. It was nice to know what mode it was in though, and kind of amusing to see it in storage mode while I'm out camping.
Depending on model. The 9100 series needs the Wizard to be multi stage. The 9200 series has it built-in. Be careful with the mode button selection. PD even recommends you leave it in automatic for optimum battery life. I can't tell you how many people have complained the wizard ruined their batteries when in fact the owner was responsible. There is a time and place using the manual button (ie generator operation) but not often.
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Old 09-28-2011, 07:17 PM   #9
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Depending on model. The 9100 series needs the Wizard to be multi stage. The 9200 series has it built-in. Be careful with the mode button selection. PD even recommends you leave it in automatic for optimum battery life. I can't tell you how many people have complained the wizard ruined their batteries when in fact the owner was responsible. There is a time and place using the manual button (ie generator operation) but not often.
Thanks. I wasn't aware the 9100 series was that way. I have to say that my experience with the 9260 was excellent, and I miss it in our new trailer. I'll be putting another 9260 in our new camper as soon as possible...especially since our current converter is dying.
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