Dual alternator kit for the Ram Promaster announced

[avanti]

Originally Posted by booster

I only ask because the loom reduces the ampicity a whole bunch, just like conduit. I think your current will drop fast enough to take care of it, though. The charts list a 10 minute heat up window, and that is very conservative, I think.

Yes, but 3/0 is still OK @270A even when derated for conduit. 1/0 would suffice for ampacity (which is what the conduit derates). The choice of 3/0 is driven by voltage drop. So, I don't have to depend of the conservativeness of the specs.

The "rules" that I have seen recommended that cables be fused on any end that has a potential current feed, so with the alternator on one end and the batteries on the other, you could feed from both ends. If the wire shorts, there will be no protection from the alternator current. Our Roadtrek was even fused on both ends of the only 80 amps each way OEM setup.

Hmmm. You may be right. Certainly if there is a battery on each side, both ends must be protected. But I located several sources that specified no fuse at the alternator. I think the reasoning was that a shorted battery is like a burst dam, but a shorted alternator is likely to quickly fail. BUT, your comment caused me to dig deeper, and I now see that they ABYC E-11 spec does indeed specify alternator-side protection. Guess I will upgrade.

BTW: I really like this fuse system from BlueSea:



Cheaper, smaller, and much easier to install than T5 and satisfies ABYC interrupt requirements. I use them on my batteries. I will just add one to the output terminal lug of the alternator.

[booster]

I really like that fuse holder, but I didn't see it listed in the fuse holder and fuse area on the site. Got a part number?

The calculators can get real dicey when you start to have the deraters, because they are add ons that aren't part of the normal wire rating, so they can be very arbitrary.

I don't know which one you have been using, but I tend to like the Blue Sea one. On it, like most, you put in volts, amps, length, and it spits out wire size. You can also add the derating factors like conduit. But--it has another field that has to be filled in if the conduit derating is used, and that is the time. If it is 10 minutes or less, you get the same rating as if the conduit wasn't called out. Above 10 minutes and you get the actual derated amperage.

On that calculator, I got 270amps for 3/0 and at 10 minutes, and I got 210 amps at any time over that for 3/0.

[avanti]

Originally Posted by Boxster1971

Now I'm worried that the measly 4 gauge wire Airstream installed to charge the house batteries form the Sprinter won't be adequate for my planned 400 Ah AGMs.

Well, if you are charging from the OEM alternator, you are just getting the table droppings from the Sprinter system, so I doubt that the size of the battery bank is the determining factor. I was lucky to ever see 80 amps from the alternator of my 2014 I4. You are probably safe. However, you will get significant voltage drop, I think, so an upgrade certainly wouldn't hurt.

BTW: The eBay seller ACDCELECTRICPARTS is a good place to shop for wire. They often have "end of spool" remnants of extremely high-quality cable at great prices. I got a 24' piece of really great 3/0 for $75:

UL 10070 3 0 AWG Black 600V CSA High Flex 6783 Strand Audio Cable Wire 24 Feet | eBay

[avanti]

Originally Posted by booster

I really like that fuse holder, but I didn't see it listed in the fuse holder and fuse area on the site. Got a part number?

They are called MRBF Terminal Fuse Blocks. BLuesea #5191:

https://www.bluesea.com/products/519...k_-_30_to_300A

[booster]

Very nice, thanks. They look to be a Buss item, made up of 3 Buss parts.

Waytek has all the Buss parts to build them for about 1/2 the price, and the replacement fuses are much less.

I think these will save me a of hassle and space.

[avanti]

Originally Posted by booster

I think these will save me a of hassle and space.

Yes, here's what they look like on my battery:

F1.JPG

Thanks for the Waytek pointer.

[avanti]

So, I just drove around the neighborhood adding 20% to SOC. When I got home, the 3/0 cable wasn't even warm to the touch. I am not worried.

[booster]

Has the amperage started to taper yet?

[avanti]

Originally Posted by booster

Has the amperage started to taper yet?

It bounces around quite a bit, so it is kind of hard to tell for sure. It is a hot day so I suspect that it is responding the alternator temperature sensor to keep it cool, as well as engine speed (these were winding, hilly roads). I occasionally saw it dip below 200, but it was averaging well above that. The Trimetric can be set to show rolling averages. I may try that at some point. I did not check whether it left bulk mode (which you can tell from the Balmar display in the engine compartment).

[Boxster1971]

Originally Posted by avanti

Well, if you are charging from the OEM alternator, you are just getting the table droppings from the Sprinter system, so I doubt that the size of the battery bank is the determining factor. I was lucky to ever see 80 amps from the alternator of my 2014 I4. You are probably safe. However, you will get significant voltage drop, I think, so an upgrade certainly wouldn't hurt.

BTW: The eBay seller ACDCELECTRICPARTS is a good place to shop for wire. They often have "end of spool" remnants of extremely high-quality cable at great prices. I got a 24' piece of really great 3/0 for $75:

UL 10070 3 0 AWG Black 600V CSA High Flex 6783 Strand Audio Cable Wire 24 Feet | eBay

Thanks! If you only get 80 amps from the Sprinter system I can now understand another reason to add a second alternator.

Good tip on wire from eBay seller.

[booster]

Originally Posted by avanti

BTW: The eBay seller ACDCELECTRICPARTS is a good place to shop for wire. They often have "end of spool" remnants of extremely high-quality cable at great prices. I got a 24' piece of really great 3/0 for $75:

UL 10070 3 0 AWG Black 600V CSA High Flex 6783 Strand Audio Cable Wire 24 Feet | eBay

Interesting on that cable. Looks to be PVC jacket and fully tinned? I couldn't see a brand name on the pix or country of origin, was it marked?

It also says it is the extra flex, which is really nice in tight spots, but I have tended to stay away from it in long underbody stuff because it can be almost too bendy and require lots of support, especially with all the weight of big cables. Of course I have not had it in 3/0, so that might not be an issue. Did you get any sag out of it using it underbody?

[avanti]

Originally Posted by booster

Interesting on that cable. Looks to be PVC jacket and fully tinned? I couldn't see a brand name on the pix or country of origin, was it marked?

It also says it is the extra flex, which is really nice in tight spots, but I have tended to stay away from it in long underbody stuff because it can be almost too bendy and require lots of support, especially with all the weight of big cables. Of course I have not had it in 3/0, so that might not be an issue. Did you get any sag out of it using it underbody?

That stuff is a dream. Made up of a zillion tiny tinned wires. Incredibly flexible for 3/0. Yes, it was labelled. Had you asked a few days ago it would have been easy . Right now, I can only see the following fragments:

3/0 AWG (backwards-RU) AWM 10070 1050??? …. LL59358

The flexibility made it very easy to route. I did not find it any disadvantage. Just used a bunch of tie-wraps--it mostly followed other cable bundles.

The ad said that this stuff retails for $12/foot!

[archeogal]

I'm putting this in this thread because it relates to exactly what you are discussing, as much as I can understand of that, which is very little. But, I need your help. We purchased a GreatWest Van/Sterling 2015 Promaster this May, shortly before Great West closed. We have problems with the solenoid charging the coach batteries, and cannot get any factory help, so wonder if your collective experience and wisdom may help us.


The second solenoid, which some shop guys are calling a battery switch, is causing problems. It sits up front under the hood, installed by GWV to charge the coach batteries. We have 2 AGM batteries beneath the floor in the rear. We are about to replace that solenoid for the second time in 4 months. First one was declared inoperative and replaced in June, because the coach batteries did not recharge while running the engine. The second was declared inoperative in September. It, or something, causes the 20 amp fuse that sits right next to it to blow. We have now replaced that fuse at least 3 maybe 4 times. That is making us nervous.

The solenoid may never operate, or only operate sometimes. During a couple of sunny days it is difficult for us to tell when the batteries are being recharged from the solar panel (one 100 watt panel), and when from running. It seems unlikely,though possible, that we happened to get 2 bad solenoids.

Two different RV mechanics now have told us that the wiring in this van is very strange. It was likely among the last vehicles off the GWV factory line, and may have been either hurriedly or incompetently wired (lots of other things on this vehicle clearly were done in a hurry, or by inexperienced people). So, we want to find a shop who can look at the problem over all, and do serious rewiring if necessary. We are not knowledgeable enough to do it ourselves. Any suggestions for a RV repair place that is good at electrical problems? We'd love to find one in the Northeast, as we live in Massachusetts, but are heading cross country to the west coast in a month, and will stop anywhere along the way, including making long sidetrips out of our way, to get this problem really fixed. In the meantime we have no choice but to rely on campgrounds with shore power most of the trip, which is a bummer. We will appreciate any suggestions.


FYI, I am posting this same thing in a different thread, in hopes that other RV owners who are not DIYers may be helped by the suggestions of the community.