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06-06-2021, 05:53 PM
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#1
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Silver Bullet
1986 34.5' Airstream 345
choctaw
, Oklahoma
Join Date: Mar 2006
Posts: 839
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Replacing the generator
I am having a hard time getting my 6500 Oman fixed. Has anyone pondered replacing the generator with batteries and 240Volt inverter? What would the cost be? How much battery would it take? How long would it last? I'm thinking if the generator was removed their would be lots of room for the batteries and inverter.
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06-06-2021, 06:49 PM
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#2
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Hi
Ok, the "easy* way to do 6KW would be with a 5KW Victron Multi Plus
https://shop.pkys.com/Victron-Energy...DC_p_2851.html
Seems to be $3,379. It also acts as a charger (which you *will* need).
5KW at 12V is a bit over 450A, even at 90% efficiency.
Simply to keep that going without nuking the batteries will mean at least 5 and more likely 10 100AH lithium batteries. They are about $900 each so $4,500 to $9,000 simply to get it running.
If you want to run full up for 24 hours, that will get you to 10,800 AH. You now are up to 11 batteries. Two days doubles that to 22.
Weight wise, the inverter is 75 pounds. The batteries are about 31 pounds each. You will have 300 to 650 pounds of batteries.
How long will you run full power? Who knows.... Run at half power and your 1 day batteries last 2 days. I would not go below 10 batteries for that size inverter ....
6KW replacement
https://www.norwall.com/products/Cum...6.0HDKAH-1044/
looks like it weighs 420 pounds. Cost $8K.
Generator is no bigger / no heavier and a bit cheaper.
Generator runs down and you need more diesel. Batteries run down and you either need shore power or a generator ( yes a couple KW of solar would also do the job, not going to fit on an AS ...).
Bob
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06-07-2021, 08:05 AM
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#3
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Hi
Thinking about this a bit more:
I'd bet that the generator replacement is a quick swap out. Pull one and the other drops right in. No change in wiring or anything else.
Putting in the inverter and batteries is going to be a *lot* of work. Rewiring this and rewiring that is only part of it. Sure, you can work for free for a month or three. Unless making up cables and welding supports is your hobby, I don't really see that as zero cost.
Bob
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06-07-2021, 01:02 PM
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#4
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Rivet Master
2005 34' Classic S/O
2006 39' Land Yacht 396 XL
north blenheim
, New York
Join Date: Sep 2012
Posts: 2,847
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I tried doing the inverter thing 20 years ago in the Snap-On truck, killed an alternator, cooked 8 batteries, and let some smoke out. A huge waste of time and money. When the truck was new it came with a Honda 6100, liquid cooled, 3600 RPM.....went through 3 of them.....junk. Switched to an air cooled Onan 6500, 1800 RPM, OK, but only lasted about 2600 hours, went through 2 of them, switched to an Onan 7500, 1600 RPM.....great got 11,000 hours out of her before she broke a breather pipe off the valve cover and set itself on fire. Replaced it with an Onan 8000 , 1600 RPM......still in use today with 7300 hours on it, had the 7500 rebuilt $5400.00 and kept it as a spare. The stainless steel box that I had built for the Snap-On truck cost $6,000.00 ......was well worth it. When I was going to switch the 370LE from a gas 460 engine to a 6.6 Duramax I bought an Onan 7500SD COMMERCIAL diesel 2cylinder which would have fit into the original 370LE compartment with a little modification. As it turns out I rebuilt the 460 and still have the new diesel Onan in stock ! Regards, Bob
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06-08-2021, 07:13 AM
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#5
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Silver Bullet
1986 34.5' Airstream 345
choctaw
, Oklahoma
Join Date: Mar 2006
Posts: 839
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Quote:
Originally Posted by uncle_bob
Hi
Ok, the "easy* way to do 6KW would be with a 5KW Victron Multi Plus
https://shop.pkys.com/Victron-Energy...DC_p_2851.html
Seems to be $3,379. It also acts as a charger (which you *will* need).
5KW at 12V is a bit over 450A, even at 90% efficiency.
Simply to keep that going without nuking the batteries will mean at least 5 and more likely 10 100AH lithium batteries. They are about $900 each so $4,500 to $9,000 simply to get it running.
If you want to run full up for 24 hours, that will get you to 10,800 AH. You now are up to 11 batteries. Two days doubles that to 22.
Weight wise, the inverter is 75 pounds. The batteries are about 31 pounds each. You will have 300 to 650 pounds of batteries.
How long will you run full power? Who knows.... Run at half power and your 1 day batteries last 2 days. I would not go below 10 batteries for that size inverter ....
6KW replacement
https://www.norwall.com/products/Cum...6.0HDKAH-1044/
looks like it weighs 420 pounds. Cost $8K.
Generator is no bigger / no heavier and a bit cheaper.
Generator runs down and you need more diesel. Batteries run down and you either need shore power or a generator ( yes a couple KW of solar would also do the job, not going to fit on an AS ...).
Bob
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Thanks Bob. Was just doing a search for 'modified sine wave inverters'. I can buy a brand new generators cheaper ( https://www.norwall.com/products/Cum...-70HGJAB-6756/ than one of them babies. Got a guy that says he can fix my generator. Been waiting 2 months for that to happen. Seems no one can/will do anything in a timely meaner.
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06-08-2021, 07:38 AM
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#6
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Rivet Master
2005 34' Classic S/O
2006 39' Land Yacht 396 XL
north blenheim
, New York
Join Date: Sep 2012
Posts: 2,847
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Depending on what’s wrong with it if you get the parts we can pull it out at the get together and I’ll rebuild it for you…..about 3 hours on a picnic table….I have the tools…….dammmmmmm did I just offer that ??? Regards, Bob
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06-08-2021, 08:39 AM
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#7
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Keen amature
1975 20' Argosy 20
Chestfield
, Kent
Join Date: Mar 2014
Posts: 3,534
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Love seeing numbers quoted that relate to lead acid/AGM/ or LiFePO4 that mimic those form factors. $500 will buy to 320ah (4s)/250a BMS (Daly), $900 for 640ah (4s2p)/250ah.
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06-09-2021, 07:57 AM
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#8
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by martin300662
..... $500 will buy to 320ah (4s)/250a BMS (Daly), $900 for 640ah (4s2p)/250ah.
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Hi
As long as you don't mind the resulting fire, that sounds like a great way to go. Yes, there are documented cases of folks doing this sort of thing and having their RV go up in flames ....
Bob
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06-09-2021, 09:17 AM
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#9
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Keen amature
1975 20' Argosy 20
Chestfield
, Kent
Join Date: Mar 2014
Posts: 3,534
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Quote:
Originally Posted by uncle_bob
Hi
As long as you don't mind the resulting fire, that sounds like a great way to go. Yes, there are documented cases of folks doing this sort of thing and having their RV go up in flames ....
Bob
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Yes, this can happen. No it wont happen, if you do it properly.
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06-10-2021, 07:03 AM
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#10
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by martin300662
Yes, this can happen. No it wont happen, if you do it properly.
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Hi
Just how much do you *know* about the internals of that eBay BMS?
Bob
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06-10-2021, 07:15 AM
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#11
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Keen amature
1975 20' Argosy 20
Chestfield
, Kent
Join Date: Mar 2014
Posts: 3,534
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Quote:
Originally Posted by uncle_bob
Hi
Just how much do you *know* about the internals of that eBay BMS?
Bob
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The specs are published, which is why I 'quoted' that specific BMS, not 'any old BMS'.
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06-10-2021, 08:16 AM
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#12
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Silver Bullet
1986 34.5' Airstream 345
choctaw
, Oklahoma
Join Date: Mar 2006
Posts: 839
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Well good news! The guy finally got to the generator. He replaced everything that should have been replaced that hasn't ever been serviced and the reason it wouldn't run is it has a broken intake valve spring. None in stock but they're going to make one. Glad I didn't try to get Oman/Cummins to work on it again. Without electronic to hook their scanner to they have no idea what to fix. That lessen only cost me $700
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06-10-2021, 03:07 PM
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#13
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Airstream Driver
1994 30' Excella
1992 35' Airstream 350
Austin
, Texas
Join Date: Feb 2002
Posts: 5,224
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Quote:
Originally Posted by uncle_bob
Hi
Thinking about this a bit more:
I'd bet that the generator replacement is a quick swap out. Pull one and the other drops right in. No change in wiring or anything else.
.....
Bob
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Unfortunately that is not the case. The new cummins /onan generators come in a housing that do not fit the classic Motorhome Generator compartment. The fuel and power supply is on the left instead of the original right.
The modifications required vary from coach to coach, the mid coach compartments being the most difficult to extend.
Currently there is no drop in replacement RV generator available.
__________________
1994 30' Excella Front Kitchen Trailer
1990 25' Excella Travel trailer
1992 350LE Classic Touring Coach
AIR #13
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06-11-2021, 05:54 AM
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#14
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4 Rivet Member
1984 27' Airstream 270
West Chester
, Ohio
Join Date: Jun 2018
Posts: 498
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I think we got lucky on our 270. It was built with the optional gen set Kohler 7k. It may have required a bigger compartment, so size-wise the new Onan dropped in with air and service holes cut out of the bottom
Connection wise, it was not a drop in, requiring an extension to the 12v line and wire harness to new control panel
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06-11-2021, 06:54 AM
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#15
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by martin300662
The specs are published, which is why I 'quoted' that specific BMS, not 'any old BMS'.
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Hi
The spec sheet on that BMS is very brief. Since they come from all over, it's never quite clear if you have a legit version or some sort of "clone". Given the source, clones are unfortunately a common thing. There's a *lot* more that goes into that BMS than a simple spec sheet.
Bob
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06-11-2021, 06:55 AM
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#16
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by PeterH-350LE
Unfortunately that is not the case. The new cummins /onan generators come in a housing that do not fit the classic Motorhome Generator compartment. The fuel and power supply is on the left instead of the original right.
The modifications required vary from coach to coach, the mid coach compartments being the most difficult to extend.
Currently there is no drop in replacement RV generator available.
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Hi
That complicates things a bit.
Bob
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06-11-2021, 07:23 AM
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#17
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Keen amature
1975 20' Argosy 20
Chestfield
, Kent
Join Date: Mar 2014
Posts: 3,534
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Quote:
Originally Posted by uncle_bob
Hi
The spec sheet on that BMS is very brief. Since they come from all over, it's never quite clear if you have a legit version or some sort of "clone". Given the source, clones are unfortunately a common thing. There's a *lot* more that goes into that BMS than a simple spec sheet.
Bob
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Understand and don't disagree Bob, but to me that is part of due diligence.
I would not buy a mainstream brand from what is supposedly 'their manufacturer' in China/overseas. But I would happily buy a unit from source (DALY is a Chinese brand and you can buy from their own store), if that technology is supported with QA/specs and proven in the field. Equally I would not buy, even a branded part (a good example is the DALY Smart BMS), based just on QA/specs are there are numerous reports of the 'smarts' failing. As I say you have to do your due diligence.
In the same way as you have to understand the likelihood of the MH breaking down each time you go out, and the minimal survival rating with involved in a crash, user assumes risks but that means user understands risks, and makes an informed decision.
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06-11-2021, 09:09 AM
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#18
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Half a Rivet Short
2017 30' Classic
2022 Interstate 24X
Carlisle
, Pennsylvania
Join Date: May 2017
Posts: 15,684
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Quote:
Originally Posted by martin300662
Understand and don't disagree Bob, but to me that is part of due diligence.
I would not buy a mainstream brand from what is supposedly 'their manufacturer' in China/overseas. But I would happily buy a unit from source (DALY is a Chinese brand and you can buy from their own store), if that technology is supported with QA/specs and proven in the field. Equally I would not buy, even a branded part (a good example is the DALY Smart BMS), based just on QA/specs are there are numerous reports of the 'smarts' failing. As I say you have to do your due diligence.
In the same way as you have to understand the likelihood of the MH breaking down each time you go out, and the minimal survival rating with involved in a crash, user assumes risks but that means user understands risks, and makes an informed decision.
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Hi
My only real point is that some (but not all) manufacturers design their batteries from the ground up. (Maybe in house, maybe another way). They do a full up design on the BMS to be sure all of the grubby details get taken care of. I used to do that sort of thing for a living, there are *always* a lot of grubby details. If you simply buy a generic BMS, you have no way of digging that deep into it.
Bob
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07-06-2021, 07:21 PM
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#19
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Silver Bullet
1986 34.5' Airstream 345
choctaw
, Oklahoma
Join Date: Mar 2006
Posts: 839
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Well don't think the battery pack is for me.
Now the bad news. NO SPRING!!! I may be able to get a spring made for somewhere around $200 or more. Went to talk to the guy who's working on it and he wasn't there and no one else knew a thing about it. Do anyone that still works for a living ever show up to work anymore?
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07-28-2021, 12:47 PM
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#20
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Silver Bullet
1986 34.5' Airstream 345
choctaw
, Oklahoma
Join Date: Mar 2006
Posts: 839
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I gave up on getting the 6.5K generator fixed. Parts are no longer available.
Not going with batteries and inverter.
So!!!! I ponied up $$$$ and bought the last 7Kw generator in the USA. I just hope it'll fit.
Getting 'overnight' ended up taking over a weeks to get here.
Took the old off the base plate put the new on the base plate then jacked it into the compartment and IT FITS!!!!! Then back out to cutting holes in the base plate for air inlet,oil filter access, exhaust. Bolted it to the base, jacked it up, put the bolts and it's in. Sounds so easy but it was not!
Thought I may need to remove the sound proofing on the back and/or the baffle on the door but it fit with about 2 inches side to side and front to back.
Now to figure out the old wires to the new. All will need a couple more feet as the old came in on the right and the new comes into the generator box in the lower left.
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