High amp alternator

[big dave]

DaveK,

Before we continue with this dicussion, i suggest you explain to us what you want out of an alternator, and what type of equipment you are going to be running. Its kind of pointless to debate over a replacement alternator if the stock GM unit it capable of supporting the kind of use you desire, dont you think? Im sure its safe to say that the stock unit will supply you with enough juice to do what you want, have you thought about a second battery?

[sdnative]

I believe he is referring to the OEM alternator from a Toyota Sequoia, which is rated at 150A.

Sorry if it wasn't clear. What I am doing is swapping a 150A unit from a toyota seqouia into my landcruiser. Someone on a different forum custom makes a lower bracket to allow it to fit. Swap the pulley from my factory unit and everything else is the same. I can get a low mileage unit from a wrecking yard for about $100 (tested and with warranty of course). These units consistently test out at well over 150A, usually from the reports I've seen 160A -170A. Best of all, it's OEM toyota.

if it's an FJ Cruiser, I'd save the time and money - it's OEM unit is tested at 140A max output.

Maybe the FJ Cruiser, but certainly not the FJZ80. I'm guessing it's well under 100A

[cruiserlarry]

Sorry if it wasn't clear. What I am doing is swapping a 150A unit from a toyota seqouia into my landcruiser. Someone on a different forum custom makes a lower bracket to allow it to fit. Swap the pulley from my factory unit and everything else is the same. I can get a low mileage unit from a wrecking yard for about $100 (tested and with warranty of course). These units consistently test out at well over 150A, usually from the reports I've seen 160A -170A. Best of all, it's OEM toyota.

You are correct - I believe it was rated at 90A... so this should work out great (very tight clearance down where that OE alternator mounts - I don't envy your hands.... )

[DaveK]

DaveK,

Before we continue with this dicussion, i suggest you explain to us what you want out of an alternator, and what type of equipment you are going to be running. Its kind of pointless to debate over a replacement alternator if the stock GM unit it capable of supporting the kind of use you desire, dont you think? Im sure its safe to say that the stock unit will supply you with enough juice to do what you want, have you thought about a second battery?

Well............good question. Being a proponent of overkill, overall I need a couple of things. I) Reliability. The stock unit has gone about 100k and its hard to beat that. 2) High output. Since I use my vehicle battery for a variety of chores at camp, the quicker I can restore its charge, the better. I do not currently have a winch but the vehicle battery is used at camp for a variety of chores including all accessories which are powered by the inverter (lights, chargers, heaters, etc), the stereo, the DVD player, the ham radio, the PC, the 12 v frig, etc. With an Odyssey AGM battery, I can safely send large amounts of juice to recharge it. This means that an alternator with a greater capacity will do the job quicker.

The stock unit is supposed to put out 140A. If forced to purchase another, I would not have much to complain about. But, now that I have a choice, I'd like to see what's out there.

I have a second battery which, when the vehicle is not running, is used as a backup for emergency starting.

[sdnative]

Very nice! The wrangler looks like a quality product.

What are the cables for? When I upgraded mine, I had to replace the alternator to battery cable (and the fusible link with a huge fuse), but didn't have to touch the negative.

[cruiserlarry]

The increase in cable size allows for the more efficient transfer of power from the high output alternator to the battery. The factory 8 gauge charge wire in the H2 would melt under the 225 amp load the Wrangler alternator is capable of putting out. The negative (ground ) cable is upsized as well, as current travels from the positive to the negative - to get full current to the battery, the ground has to be equal to the size of the positive cable (this is true for any circuit, regardless of application).

In summary, the inline fuse is for protection from surging; the cables are to allow full charge current flow without a meltdown...

[sdnative]

I only replaced the cable from the alt to the battery. I used a 1 gauge wire with a mega-fuse and this holder from blue-sea (I love their products, but they are $$$$):



Since my alternator is rated at 150A, I used a 175A fuse. The 1ga wire is plenty big to handle the current.

I didn't replace my negative cable because the alternator is grounded through the case to the engine and through a large wire back to the battery anyway.

My next step is to replace the + and - battery cables and get some of those really cool terminals:

[cruiserlarry]

Most hi-output alternators have a separate ground terminal on them, for protection. Even with the case grounded, running a large gauge cable to ground the alternator won't hurt.

[taugust]

Like you, I wondered why it was necessary to replace existing cables, including one with a huge 250A fuse. I called their tech support and the best I was able to understand is that both the positive and negative cables and the fuse add a layer of protection given the significant increase in amps that the new alternator can deliver. The positive cable, I could understand, since the H2's cable couldn't have been more than 8 gauge (maybe 6). How they got away with that I'll never know. In their defense however, I have put over 110K miles on the rig and with the exception of a failing alternator, there have been no other electrical problems - maybe they do know what they were doing????

For the neg cable, the same added layer of protection explanation was offered.

Probably. but it brings to mind a situation that I observed about 5 years ago.

While exploring in Ocotillo Wells SVRA, I came across a large group of H2 owners, driving around and exploring as well. They looked like they were having fun. I left them at the Pumpkin Patch and headed back toward park headquarters. As I was returning, I noticed a column of black smoke rising up to the east of my position. i watched for a short time, then headed back, thinking it might be coming from outside the park. Later, near the headquarters, I was just about to head for home, when a small group of H2 owners arrived to use the restrooms. I noticed they were all looking at the screen on a mini camcorder. I walked over and asked what the group had been up to. They explained that they were new H2 owners out on a dealer organized run to teach them how to drive their new vehicles. I asked about the video and they showed it to me. It showed a brand new H2 on fire, and how it burned to the ground in about 10 minutes, out in the middle of the SVRA.

Apparently, there was some sort of electrical problem, as the driver reported seeing the dash displays flickering just before the fire started. They got out of the vehicle and it caught fire. Not one person in the group of about 20 vehicles, including the dealer driven vehicles, had a fire extinquisher. I always wondered what happened with the dealer and their liability. Important safety tip: ALWAYS carry a fire extinquisher.

[cruiserlarry]

You need to replace the negative cable when using a high output alternator for a very simple reason: electricity flows in a loop, and if one part of that loop has significantly less capacity or much greater resistance (usually one leads to the other) you risk overheating the weak link and causing damage to the alternator, cable, or in more severe cases, cause an electrical fire.

If you look at virtually any electrical device on the vehicle (or house, or plane, or boat), both the power and ground wire are of equal size; in some cases, such as high power 2-way radio equipment, both the negative and positive sides of the power cable are fused, as well.

Just because the original alternator is grounded to the engine by it's case, doesn't mean that it has sufficient ground for a higher capacity alternator that replaces it. You need to check the engine grounding straps or mounting points to see if there is a high enough capacity ground (usually not). Adding the extra ground cable (or oversizing the power cable and the ground cable) is just that much more assurance that you will not end up like that H2 in AB....