Help confirming assumptions on Sterling BB1260

marklg

Well-known member
The Sterling may get destroyed if the solenoid is left installed. The solenoid would short Sterling output to input. Sterling would not be happy.

You don't have to run a cable from Sterling input to chassis battery. The cable is already in place. Remove the solenoid and you got the solenoid cable to power the Sterling.
The existing cable is probably too small. I think it was AWG8 on mine. The Sterling has a listing for cable sizes. I would use the next bigger one than what they recommend.

I actually asked Sterling about the solenoid on at the same time, shorting the output to the input. They said it was not good, but shouldn't damage it right away. The undersized cable probably limits the current. I didn't take a chance.

Regards,

Mark
 
The Sterling may get destroyed if the solenoid is left installed. The solenoid would short Sterling output to input. Sterling would not be happy.

You don't have to run a cable from Sterling input to chassis battery. The cable is already in place. Remove the solenoid and you got the solenoid cable to power the Sterling.
Hi calbiker. I know you have an 07 Navion, so I really appreciate your post.

It's late and I've been looking at this stuff all day, so I'm impaired.

I'm very happy to eliminate the cole hersee and the dribble fart maintainer. I have a J model and I'm putting this B2B on the cabinet end immediatly to the left when entering the habitation area (below the sink but on the outside, not inside the cabinet). I figured that's 15 feet one way conservatively to the starter battery, probably 12 all done.

Winnebago's cable is a 1 GA SAE, J1127, 60V, Type SGX battery cable rated at 125C I'm pretty sure. Is this suitable for the 60 amp draw? I ask because of the cable, but also, isn't there a 40 or 50 amp fuse on this cable run?

The other vehicle specific question I had is, how does the DC loads to the motorhome occur if the existing red cable is redirected to input to the B2B unit and the B2B unit is off (vehicle is not running)? I don't yet have a clear understanding of how that existing Winnebago installed red cable feeds the DC load center under the refrigerator, so that the motorhome has Dc power when parked and the engine off.
 
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All that's fine. But if your Xantrex charger works well, your "converter" is also redundant.

Strive to simplify.

Those Crowns won't accept even 40A for long, forget 60, but going over does them no harm.

When you go LFP you'll be very happy for the B2B.

Yes it can pull from either alt, in fact given you're remote destinations might want to wire to be able to switch from either.

Rather than upgrading your alt in future, first buy a quiet inverter gennie, ideally runs off propane (your van is diesel right?)

Lots of flexibility in sources is key to off-grid van-dwelling.

Thanks. The load center Winnebago used in 2005 production on this rig is a Parallax that's was crappy. It's like $235 new today! I replaced the charging section with a direct replacement that added 3 stage charging, a new DC load center, but still no temperature compensation. But, but it will boost to 14.4 at least for 2-4 hours. In short, its hideous. Yes, I keep that AC breaker turned off. I can't image being disparate enough to use it, but it does cough up some marginally decent bulk charge, but that's it.

Yes, I'm diesel. I have a Honda 2000 inverter generator that's set up to burn petrol or LP gas.
 
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The existing cable is probably too small. I think it was AWG8 on mine. The Sterling has a listing for cable sizes. I would use the next bigger one than what they recommend.

I actually asked Sterling about the solenoid on at the same time, shorting the output to the input. They said it was not good, but shouldn't damage it right away. The undersized cable probably limits the current. I didn't take a chance.

Regards,

Mark

Mine is as shown in my other post: 1 gauge. I ran it real quick online; 15 feet, 60 amps, 13 volts, and got 1/0 cable @ 1.36% loss. I'm not sure what cable to use, but I'm thinking high dollar since it's going to be in the engine compartment. Maybe some Blue Sea stuff?
 

john61ct

Active member
how does the DC loads to the motorhome occur if the existing red cable is redirected to input to the B2B unit and the B2B unit is off (vehicle is not running)? I don't yet have a clear understanding of how that existing Winnebago installed red cable feeds the DC load center under the refrigerator, so that the motorhome has Dc power when parked and the engine off.
The wire running between the Starter / alt circuit and the B2B **input** is different from the output side where the House bank and loads are.

The House bank should be always-on the circuit wrt DC loads, except those fitted with LVC like many fridges.

A "master" LVC set to a lower voltage can help protect the bank as a whole.
 

marklg

Well-known member
8 awg??? NO WAY!

It's perhaps 1/0
Mine sure looks like 8. The two AWG 4s I ran are below. I had that around and two AWG 4s are about the same as an AWG1.

Don't be surprised by the crap they pull in wiring RVs.

I had to smudge the key for size comparison in the picture, just in case any of you wanted to duplicate it from the picture.

Regards,

Mark
 

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Mine sure looks like 8. The two AWG 4s I ran are below. I had that around and two AWG 4s are about the same as an AWG1.

Don't be surprised by the crap they pull in wiring RVs.

I had to smudge the key for size comparison in the picture, just in case any of you wanted to duplicate it from the picture.

Regards,

Mark
I'm not smart enough to duplicate the key. :smirk: That's some funk on those terminals. My 2006 Itaska Navion's cable is marked well. It's gauge. I have some remarkably detailed Winnebago diagrams to study tomorrow.
 

calbiker

Well-known member
Say Mark, what type of vehicle is that? Doesn't look like a '07 Winnebago.

No one would install 8 awg in there. It conducts 80A. It's a battery-to-battery connection. SOC and cable resistance is what limits current through that wire.
 

marklg

Well-known member
Say Mark, what type of vehicle is that? Doesn't look like a '07 Winnebago.

No one would install 8 awg in there. It conducts 80A. It's a battery-to-battery connection. SOC and cable resistance is what limits current through that wire.
It's a 2007 Great West on a 2006 T1N chassis. They did. I don't think they used larger than 8 AWG in any of the 12V wiring in the coach. Someone added an inverter / charger with inadequate wiring too. I put in four 100AH LiFePO4s, AWG 1/0 to each, combined to one AWG 4/0 to the inverter / charger. AWG4 to almost everything else I added.


Regards,

Mark
 
This vehicle is basically a weekend motorhome application, but it's great for South America, since there is no ULSD down there. This 2006 burns the old diesel. For security and comfort reasons, we wanted a "live inside", not "live beside" vehicle. Hence, we're building this into an "overland lite" vehicle, because I'm not ready to get into the crazy money "live inside" overland vehicle market ($150-$400K).

It had a 3.6Kw Onan LP generator and an 13,000 btu AC unit on the roof, which I removed. The gennie compartment has no bottom with the Onan out, so I fabricated a steel tray to hold my Honda 2000 that I already had. I put a 600cfm weather proof fan behind the gennie to allow it to be run while in the compartment and stay cool. There is an aftermarket stainless, flexible hose and adapter that's welded to the Honda's exhaust, to allow exhausting behind the vehicle.

I converted the ignition red power input to the Onan into an additional shore power cord, so now I have shore power on both sides of the vehicle. The Hutch Mountain LP conversion kit (not shown) plugs into the LP gas grill quick connect that I installed, so I can run a grill off the old LP line, plus optionally burn LP in the Honda. I plug shore power into the Honda when running, then on the other side of the vehicle in the shore power compartment, plug that shore power into the "generator" receptical, then the vehicles primary AC/DC load center is energized, so I have AC everywhere. In this mode, the Xantrex charger unit in the inverter/charger would function.

I call this space my "garage".
 

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calbiker

Well-known member
I got something similar. I ordered the Winnebago without the Onan. It was too heavy. Saved 100 lbs (and $2000) with this Yamaha 2800. I was concerned for ground clearance and chose this model as it is the shortest I've found. Also got a DIY propane fuel conversion (seen on the left). No fan. Been working OK for 12 years. Though I don't use it much. Just to operate the microwave.
 

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I got something similar. I ordered the Winnebago without the Onan. It was too heavy. Saved 100 lbs (and $2000) with this Yamaha 2800. I was concerned for ground clearance and chose this model as it is the shortest I've found. Also got a DIY propane fuel conversion (seen on the left). No fan. Been working OK for 12 years. Though I don't use it much. Just to operate the microwave.
Sweet setup. I didn't have a fan, then an experienced mechanic at a Honda power systems dealer came out and looked at my rig. I wanted my compartment sealed due to the dust and mud, etc. He said the fan would be a good idea and he had done one like I was planning in a trailer he used for servicing race cars.

Do you run the generator with the compartment closed while driving?
 

calbiker

Well-known member
A fan is a good idea when operating the generator for longer periods of time. Do you use a 120V ac fan? That's ideal as it automatically turns on & off with generator operation.

I don't operate gen while driving. I just use it for lunch or dinner to operate the microwave for up to 5 minutes duration.

Regarding cable sizing. The cable from chassis battery to Sterling isn't that critical. It could have 3% voltage drop. Sterling current output isn't affected.

It might be 60 A at 14.7V, or 882W.

Sterling efficiency might be 90%. Therefore the alternator needs to supply 882W * 1.1 = 970 W *if* cable resistance is zero. If cable line drop is 3% then load increases to 970W * 1.03 = 1000 W. If you used cable that has 1% line drop, the load is 980 W.

If the alternator outputs 13.7V, then:

with 3% cable, alt current is: 1000 W / 13.7 V = 73 A
with 1% cable, alt current is: 980 W / 13.7 V = 71.5 A

Hardly any difference. Alt needs to supply 1.5 more amps with 3% cable.

That's why I mentioned it's OK to use existing cable.

On the other hand, the cable from Sterling to house battery is critical. That loop (combined pos and gnd cable) should be kept to 1% line drop.
 

marklg

Well-known member
A fan is a good idea when operating the generator for longer periods of time. Do you use a 120V ac fan? That's ideal as it automatically turns on & off with generator operation.

I don't operate gen while driving. I just use it for lunch or dinner to operate the microwave for up to 5 minutes duration.

Regarding cable sizing. The cable from chassis battery to Sterling isn't that critical. It could have 3% voltage drop. Sterling current output isn't affected.

It might be 60 A at 14.7V, or 882W.

Sterling efficiency might be 90%. Therefore the alternator needs to supply 882W * 1.1 = 970 W *if* cable resistance is zero. If cable line drop is 3% then load increases to 970W * 1.03 = 1000 W. If you used cable that has 1% line drop, the load is 980 W.

If the alternator outputs 13.7V, then:

with 3% cable, alt current is: 1000 W / 13.7 V = 73 A
with 1% cable, alt current is: 980 W / 13.7 V = 71.5 A

Hardly any difference. Alt needs to supply 1.5 more amps with 3% cable.

That's why I mentioned it's OK to use existing cable.

On the other hand, the cable from Sterling to house battery is critical. That loop (combined pos and gnd cable) should be kept to 1% line drop.
From my measurements, the input to the Sterling is more like 60-65A, the output is more like 47A. The newer Sterling (green stripe) seems to handle low alternator voltage better. The efficiency is more like 80% with alternator voltages in the 13.3-15.5V range.

Regards,

Mark
 
From my measurements, the input to the Sterling is more like 60-65A, the output is more like 47A. The newer Sterling (green stripe) seems to handle low alternator voltage better. The efficiency is more like 80% with alternator voltages in the 13.3-15.5V range.

Regards,

Mark
Calbiker, John61ct and Mark and others,

Thanks for the "real world input". Sterling's specs are incomplete it seems, because they say the BB1260 is 12v input at up to 60 amps and output is 12v at up to 60 amps; yea, right. No efficiency is provided making you all's data really good. I've seen a 25% safety margin used for protecting solar chargers, so 60 x 1.25% = 75 amps. Don't know fi this application would be different. But Sterling says a 60 amp output, then calls for a 100 amp fuse. Confusing to a novice like me.

John61ct recommended Bestboatwire.com for cable, so I'm doing the tinned, UL1426 cable with a 105C rating (BC5-W2).

Thanks for the cable input calbiker. I'm going to crawl under and pull some cable loom along the same path and get a real good distance estimate on the Sterling to chassis battery run. I'm guessing installed it's 11 feet one way. The Sterling to house battery is only about 4 feet one way. I prefer to run new cable between the sterling and the chassis batt, rather than reuse the existing 1AWG. The existing one has open ended lugs, is 13 years old, and has the solenoid to be eliminated in it also.

With the sizing tool: http://www.bestboatwire.com/wiresize
Please check my inputs
Sterling to chassis batt: 11 feet one way, single conductor, 12V, 60A. Result: 1AWG is a 1.4% voltage drop.
Change above to 70 amps = 1.63% drop.
Sterling to house batt: 4 feet one way, single conductor, 12V, 60A. Result: 1AWG is a .51% voltage drop.
Change above to 70 amps = .59% drop.

Unless you guys say no, I'll get enough 1AWG to wire it all. I plan to use the bolt on 100 amp fuse in my PDC at the Sprinter's chassis battery and one of these holders with the same fuse between the sterling and house batts: https://www.amazon.com/gp/product/B004T1VYLA/ref=ox_sc_saved_title_3?smid=ATVPDKIKX0DER&psc=1

Per John61ct's comments, I'll update the install diagram to tomorrow. I still must confirm how to eliminate the existing 1AWG cable Winnebago installed, which includes the boost solenoid shown on the drawing I posted.

There is a "battery disconnect" solenoid next to the "boost solenoid". Subject to confirmation, I believe I'll be eliminating the old cable from my house battery back to the disconnect solenoid. This eliminated section will include the boost solenoid (and the 5 amp Tric L Start chassis battery maintainer). This will leave the old 1AWG cable from the chassis battery to the motorhome's DC load center in place, which includes the battery disconnect "kill switch" solenoid.

I do not suppose there will be a "kill switch" on the Sterling's connection to the chassis battery. I may have to pull a terminal off or remove the fuse; not sure.

Next step: post revised install diagram.
 
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calbiker

Well-known member
You can't derive converter efficiency from just looking at input and output current. Efficiency is calculated from:

% efficiency = 100 * [1 - (power out / power in)] = 100 * [1- (Vout * Iout / (Vin * Iin))]

My gut feel is that efficiency is greater than 80%. If the Sterling is outputting 900 W at 80% efficiency then it is consuming 180 W. It would be getting very hot!

Something is wrong if a 60A rated Sterling is not outputting 60A into a depleted battery. Either the Sterling is defective or the cable between chassis battery and Sterling is too small. The line drop would be so large that the Sterling input voltage drops below its minimum specked value.


From my measurements, the input to the Sterling is more like 60-65A, the output is more like 47A. The newer Sterling (green stripe) seems to handle low alternator voltage better. The efficiency is more like 80% with alternator voltages in the 13.3-15.5V range.

Regards,

Mark
 
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Thanks for the formulation calbiker. I had math beyond calculus so the numbers get right to the point without all the babble. ha ha
 

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