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Topic: 300 amp Delco 40si alternator/isolator/cabling upgrade (Read 2309 times) previous topic - next topic

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #25 –
Quote from: TulsaTrent –
One thing i noticed from the graphs is that the alternators were based on an idle speed about 2000 rpm, and go up to 8000 rpm. Newer Foretravels may be different, but mine idles about 800, with fast idle at 1200 rpm. I haven't paid that much attention to my tachometer, but it seems like my cruising speed is about 1600 rpm. The new alternators do not seem to reach their peak rating until about 5000 rpm.
 
I am not sure how this applies to our Foretravels, but it sure seems we would not really generate 350 amps, for example. Or is there something I am missing here? Don't get me wrong, brushless certainly seems the way to go, and you seem to have found the best prices out there. Just wanted to point out you may not be able to achieve the rated amps in your Foretravel.
 
Trent
Trent:

I was wondering the same thing and wanted to check the RPM after putting in the 40si. I ordered this Digital Tachometer from Amazon a couple of weeks ago and took some measurements on my Delco 40si alternator. At 650 RPM engine idle the alternator was spinning at approx 2000 RPM so the engine shaft/pulley ratio is 3 to 1. So this means at 1800 engine RPM (highway speed) the alternator should be spinning approx 5400 RPM which puts it near the maximum rated output on the graph.
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Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #26 –
Quote from: TulsaTrent –
BTW, I noticed that your two upgrade systems specified a lower isolator rating than the alternator ratings. I am sure it is supposed to be higher. Unless you are implying that your alternators will never run at their rated outputs.

Trent:

I think the SurePower 300 amp isolator is heavy enough for the DelStar 350 amp alternator, and here is why:  It would be rare to run continuously at the full rated current of 350 amps (that is almost 5000 watts of power). The more usual case will be occasional intermittent current at that level, say when house batteries are low after dry camping. Diodes have intermittent (peak) current ratings several times higher than their continuous current ratings, and intermittent over-current won't damage them.

If one wanted to be very conservative, you could go with the more expensive PowerLine 400 amp isolator.

For the PowerLine 400 amp isolator, the company says their isolators are designed to supply the full rated current to each battery bank. For the 400 amp isolator that would be a combined current of 800 amps, so the PowerLine 400 amp isolator should be able to easily handle the 435 amp DelStar alternator, as current will be split to each battery bank.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #27 –
Quote from: TulsaTrent –
Have you had enough experiences with 4/0 cable to discuss the differences between standard, welding cable, and marine grade 4/0 cables? It seems like standard 4/0 may work from batteries to the bus bars and possibly from there to the isolator. But any more complex routing would definitely benefit from more flexible cable.

How about the price differences? Anybody know how the prices compare for, say 50 feet of the three types of 4/0 cabling?

Trent:

I have only used the untinned copper super flexible welding cable.

Here are the approx prices I have paid:

4/0 - $6.00 / ft
2/0 - $3.20 / ft
2    - $1.50 / ft

I think Don (Acousticart) has used the tinned marine cable, maybe he will chime in...
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #28 –
Quote from: Chuck & Jeannie –
EDIT:  DANG!  Brett beat me to the draw by <1.0 minute.
Yeah, but now they both say four hours.  :D
 
Trent
Trent and Jean Eyler
2000  U295  4003  WTFE  ISC  350
Build#5603 MC#17385

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #29 –
I used 4/0 marine cable and I "fondled" some 4/0 welding cable. I wasn't able to compare them side by side, but my feeling was that the welding cable was a bit more supple than the tinned marine cable. However, I found the marine cable quite workable and though more money (Bay Marine Supply's price at the time with a slight discount for frequent buying was $8.90 per foot), I just liked the idea of the tinned cable being basically corrosion proof in the RV application. There was apparently some high resistance in the interconnecting link between the original two chassis batteries. Replacing that short piece (actually doing away with it because I replaced the 2 red tops with one 8DAGM O'reilly battery), made all the difference in starting without boost. All of the other original cabling was still functioning just fine. But since the inverter upgrade (Magnum MSH3012M) called for 4/0 cabling, I felt obliged to replace all of the house battery cable and so opted for the more expensive marine cable because that is what made me happy :)) .
Don
Quote from: prfleming –

I think Don (Acousticart) has used the tinned marine cable, maybe he will chime in...

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Don & Tys
1999 U270 3602 WTFE #5402
Xtreme Stage 1 w/Headlight, Step Conversion, etc.
2009 Honda Fit Sport with Navi
Freedom is NOT "just another word for nothing left to lose"... with apologies to Kris Kristofferson

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #30 –

Alan Ferber at Bay Marine Supply is a Forum Commercial Member and will give forum members 10% off just for asking. Nice guy to talk to on the phone as well.

Amazon has Ancor marine 4/0 tinned cable for about $10.75/ft including shipping. For some reason Black is more expensive than red.

Amazon.com : Ancor Marine Grade Electrical Tinned Copper Battery Cable :...

Bay Marine has 4/0 Marine cable for about $8.10 /ft.  Looks like HD ends are reasonable too. Assembing the cable is $4.00.  Not sure about shipping but it is $8.95 on most orders.

Custom 4/0 gauge marine battery cable

WireNCable has 4/0 welding cable for $4.31/ft.  100 ft appears to ship free. Not sure what Class K means.  EPDM cover. 90°C (194° F)

4/0 Welding Cable Class K

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Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #31 –
Quote from: Roger & Susan in Home2 –
Alan Ferber at Bay Marine Supply is a Forum Commercial Member and will give forum members 10% off just for asking. Nice guy to talk to on the phone as well.
Yes, I called Bay Marine Supply a while back to check on something. Alan asked "what are you working on?"... We talked for about a half hour...

Quote from: Roger & Susan in Home2 –
WireNCable has 4/0 welding cable for $4.31/ft.  100 ft appears to ship free. Not sure what Class K means.  EPDM cover. 90°C (194° F)
I wasn't sure either, here is a good explanation. Has to do with the stranding. Class K is next to the finest wire used.
Peter and Tammy Fleming
1991 U300 GV 40 - Sold, owned for 4 years
Downsized to Roadtrek Popular 210 class B

Re: 300 amp Delco 40si alternator/isolator/cabling upgrade

Reply #32 –
Here is another source that has both tinned marine cable and welding cable.  Welding cable has 2007 strands.  Both are rated to 105°C

4/0 AWG UL Approved Marine Grade Tinned Copper Boat Battery Cable Rated 600...

Welding cable is about $5/ft.  Marine cable about $10.  Maybe marine cable in the engine bay and battery connections in there. In the bays maybe welding cable, more flexibility, less external environmental issues.

Roger

Roger Engdahl and Susan Green
2001 U320 3610 #5879 (Home2) - 2014 Jeep Cherokee or 2018 F150
Hastings, MN