Anyone have an alternator diode collecting dust?

[CharlieS]

I was doing research on charging AGM starting batteries and it sounds like this diode that replaces to alt-s fuse is well liked to boost the alternator output.

I also saw that a bunch of people with 16+ rigs that don't have an alt-s fuse bought these and can't use them. Plus a few others of people that were skeptical about the mod that bought them and didn't install them.

I went to buy one online, and the lead times are long for HKB, and both of them charge an arm and a leg for shipping.

So, I wanted to check here first before I buy. If you have an alternator diode from HKB or DirtyParts collecting dust, and would be willing to sell it, could you drop me a line?

 

[RET2]

For the life of me I don't know where I saw it but there was a thread about FORD having such an item available over the counter at a cost much less than an import part?

 

[Markuson]

I was doing research on charging AGM starting batteries and it sounds like this diode that replaces to alt-s fuse is well liked to boost the alternator output.

I also saw that a bunch of people with 16+ rigs that don't have an alt-s fuse bought these and can't use them. Plus a few others of people that were skeptical about the mod that bought them and didn't install them.

I went to buy one online, and the lead times are long for HKB, and both of them charge an arm and a leg for shipping.

So, I wanted to check here first before I buy. If you have an alternator diode from HKB or DirtyParts collecting dust, and would be willing to sell it, could you drop me a line?

I have one...because I ended up adding the more costly, adjustable HKB unit. So I have the regular HKB diode/fuse unit now sitting idle.

 

[grinchy]

They are seriously very easy to build. But I guess that assumes you have a capacitor and add a fuse sitting around, a soldering iron and have soldered once or twice before.

 

[CharlieS]

Thank you. That'd be cool.

To be honest, I'm a bit inimidated by electronics, beyond simple stuff. I don't know a diode from a transistor from a capacitor. Soldering wires together is about the extent of my ability, unless I have detailed step by step instructions.

Given that, it might be safer for me to buy one.

I have a soldering iron, solder, fuses, wires and a mishmash of supplies and I suppose I could try to make one.

I've never done anything with a diode, and wouldn't know what to buy, where to buy it or how to make one of these things.

If no one has one collecting dust, I'm willing to try if there is a good step by step DIY. It'd need to have specifics though...

 

[grinchy]

I won't belabor the point, but here are some diodes that will work:
Ok. for some reason the amazon link won't work. Search up 20PCS 10A10 Rectifier Diode 10A 1000V R-6 Axial 10 Amp 1000 Volt


I had some in-line fuse holders from another project that I used. I'll go look on my build thread, I believe I took a picture of the final assembly; if not there it's on the diode thread.

I used a mini fuse as the carrier, it's a bit larger and easier to solder too. The hardest bit is exposing the leg of the sacrificial to solder too. That plastic is hard. If I had it to do again I'd use a dremel . . .

 

[CharlieS]

Could I use one of the add a fuse things to make this? That would keep a fuse in the circuit, and add a diode in line.

I would have to get the diodes you mention above, but I mocked it up with a piece of solder as a stand in for the diode. I think I read earlier today that diodes are directional? Which end goes on which side - stripe closest to the power source?

I'm not sure it is in the right place in the flow of power though. I think if I set it up like below, that would have the diode between the fuse and the load. Does that seem right?

As pictured below, the left side is the input of +,both terminals have continuity from the left leg of the add a fuse. On the right side, only the lower terminal has continuity from the right leg of the fuse. The upper terminal has continuity to the red lead.

 

[grinchy]

Builds - The Guzzler - 2009 LX570

How has your AHC held up with the mods and that many miles? Also, what’s your oil of choice and interval? Thanks! Beautiful LX!

forum.ih8mud.com

Here's the post and the note:
I used a Mini Fuse, 40 A as the body (not a LP mini, which is the regular fuse in the LX570). A Mini fuse inline holder as @619TOY did, and a 10 A diode. the hardest part was getting access to the blades on the sacrificial fuse. It took around 30 min start to finish.

For orientation, mine worked with the diode on the blade toward car front / battery. And the diode should show the band toward the fuse.

 

[george_tlc]

^ NOT capacitor! It is a DIODE that is required.

cheers,
george.

 

[CharlieS]

Ok, my electrical ignorance shows through here - what is the difference between different diodes. I've seen references to 1 A, 3 A and 10 A diodes on 'mud for this mod. Do they all work equally well? Google tells me the amperage rating of a diode is the amount of power that the PN junction can dissipate without damaging itself. So is it best to go with a higher amperage diode (the 10A). I don't understand the implications of using one or the other.

 

[grinchy]

Yeah they all will probably be fine. 10a probably the hardiest, but it isn’t too relevant in this use case

 

[george_tlc]

The diode is just acting as a voltage drop (nominal 0.7V at rated output current) that make the alternator think the battery voltage is lower than it is and therefore causing the alternator to output higher voltage.

Since this is a sense input, the current rating of the diode is not particularly important. A 1A diode would do fine. More importantly is the voltage drop (Vf) of the diode at low current (the sense current will be low!). That Vf is what will determine how much you are 'boosting' the alternator output. Also, the diode Vf WILL vary with current and also to some extent temperature. This is just a simple 'hack' to get the alternator to output slightly higher voltage to the battery.

There are also schottky diodes that have lower forward voltage (some are near 0.2V at low current). I'd suggest you pick up a bunch of diodes and then choose the one that gets your battery voltage near what you want it to be.

Of course the 'proper' solution would be a bunch more electronics to allow you to select exactly how much higher you want the alternator output voltage to be.

If you want to be foolproof, wire two diodes in parallel, with the bands opposite each other. Then it doesn't matter if you connect the 'boost circuit' backwards. And, don't pay the stupid ripoff prices that some folk are selling the diode based boosters for.

cheers,
george.

 

[fj4068]

I went to buy one online, and the lead times are long for HKB, and both of them charge an arm and a leg for shipping.

DirtyParts will send a PayPal quote for USPS as an alternative to the website's UPS pricing. They need your name, shipping address, phone and the email you use with paypal. There is a contact form on their website.

 

[fj4068]

@george_tlc,

Any chance you'd make a batch of plug-in alternator sense diodes for the 200/LX570 crowd?

The 80-series LED domes and sub tank relay I received from you are still working great, 13 years later...time flies.

 

[george_tlc]

Since I don't own a 200 series, I have no idea what the plug in solution would look like from a connector/etc perspective.

Electrically it's just a matter of inserting a diode in series with the alternator sense wire that I think terminates into a fuse in the engine bay. Doing that neatly is the challenge...

cheers,
george.

 

[RET2]

I found the thread finally on another forum. AGM BATTERY CHARGING - ALTERNATOR VOLTAGE BOOSTER. Might save a few $ and time.