A different fix for AGM charging

I mean, from the looks of the GM part, it is a 1 amp diode, so it would stop passing current before the fuse rated at “5 amp” goes…

 

So just turn the tap itself 180 degrees?

Here’s what I got currently…

 

Which begs the question of why then is it recommended that the charge rate of an AGM is 14.4-14.7 (iirc that’s actually the recommended rate printed on my X2) while the OEM rate is set for wet batteries at 13.5-13.7 so why wouldn’t I regulate the charging system to meet the battery manufacturer’s requirements?

This is all new to me so I’m sincerely asking because I also find it odd that if meeting this manufacturer’s charge rate requirements why then would this be such a polarizing issue to the degree that it has spawned cottage industries marketing “Voltage Boosters for AGM Batteries”?

 

Could this be why the GM diode is listed and advertised as being a “Multifunction” diode?

Cause I haven’t found an answer to that question yet either.

 

^^^^^This!

 

Because you're confusing the saturation voltage of "wet" batteries as 13.5-13.7. This is incorrect.

 

Yes. This was pointed out to me immediately following my OP but I’ve since used a routing diagram suggested to me in post #8 which I pictorially executed in post #10

No. I’m not confusing saturation voltage I’m just stating the recommended charging rates from the manufacturers of both types of batteries.

 

Ay carumba...

14.4-14.7 is the saturation voltage for AGM. You go above that and you enter the hydrogen cycle and begin driving grid corrosion of the positive plates. 13.5-13.7 is the bulk charge voltage for "wet" batteries.

Yes, you were confused but you shouldn't be now.

 

LOL I’m in the Ay curumba phase now as well because why then are so many seeking to achieve exactly that charge rate with AGM’s by conjuring up these contraptions known as “Voltage Boosters”?

I’ve been an aerospace machinist cnc programmer going on 38 years in the industry now but admittedly don’t know squat about automotive electronics but I could be marked extra confused now however I do appreciate your attempt to explain things

 

Found a few other ones for sale and dug into several “AGM Voltage Booster” threads on the interwebs. The circuit is simply the voltage sensor for the alternator - the output of that circuit is what the alternator is seeing as the measured output voltage. So by running that through a rectifier diode that will drop that voltage by a certain amount, the alternator sees a reduced output and increases the output until it sees what it is expecting to see.

As I understand it, a zener diode would actually increase the voltage in that sensing circuit.

 

i mean that works too. The just puts the diode before the fuse.

 

The way you have it is how they are sold and should work, mine was that way for a few years. Due to the loop of wire added to the packaging vs. combining the diode with the tap body like the one linked earlier you could flip both the tap and diode 180 degrees if possible as suggested. This will fuse protect the added loop of wire in the fuse box. A fuse and diode are two different things, every available booster I’ve seen retains the fuse component…

*I removed the booster after replacing 2 batteries, proper charge every few weeks and battery has been happy for 2+ years*

 

so two questions…

Q1: so all this “voltage booster” rig for AGM batteries stuff is a bunch of unnecessary malarkey? (Note: “yes” is an acceptable answer that will not be contested)

Q2: If I elect to toss this voltage booster rig and just allow my AGM battery to deplete and recharge as necessary can I just hook my smart charger up to the battery without disconnecting it and let it charge while still connected or is it recommended to remove the terminals?

 

Depends on on everything was done, i was treating it like an external voltage regulator.

but alas, I’m far too lazy to explain…youtube vid explains far better than I

https://youtu.be/XhQqtdTlRus

i recall using zeners directly in the voltage regulator of certain alternators to tune output voltages, as well as using them to smooth out sensor signal outputs to prevent over-voltage conditioning when installing things like aftermarket turbos….

 

A rectifier diode has a forward bias voltage drop when conducting - typically 0.6ish volts. The boosters with a switch have two rectifier diodes for low and high output. Without seeing the board, my guess is that it flows through one or both diodes to drop the control signal. Since the low output charge goes from 13.6 to 14.2, and high to 14.8 (roughly - there are going to be losses), it matches that thought.

A zener is used to regulate voltage and can be used as a crude means, say to drop logic levels, or as overvoltage protection. These are likely not zeners but now I want to try. The closest I have on-hand is a 12 and 13V.

 

https://www.tundras.com/threads/a-different-fix-for-agm-charging.124049/#post-3177335

Looks,smells and tastes like a basic rectifier diode..

 

Yeah, I saw that (thanks for the sacrifice). My explanation just backs up your pic.

 

Cruising on the highway at 80ish I was getting 14.4V with the diode

 

@BiggHertz just made this whole thing way easier, especially if you already have the GM diode. Just need two add a fuse taps and splice their leads together:

 

So on one hand we have folks whipping up diode rigs to attain 14.2-14.4V alt output and then we have the other camp saying BTDT and went back to just hooking up a charger every so often with claims of longer service life and yet after have another camp that just pulled their fuse, stuck in the diode and lived happily ever after.

Mark me “still confused” and calling the manufacturer

 

The answer is "yes"

 

So as it turns out there is no X2Power Customer Service number because the X2 is exclusive to Batteries Plus which led me to their CS number and after being greeted by Teresa she got my name and battery model along with my question then put me on hold.

5 minutes later I hung up.

Guess I’m just going the charge it route by putting the 5amp fuse back in its rightful place and toss the other crap.

if nothing else it’ll give me piece of mind

 

Get yourself a smart charger and hook it up to the battery once a month. It won't overcharge and will keep your AGM battery in good shape. And, you won't have to be an electrical engineer to figure it out.

 

Which manufacturer?

 

This is what I was understanding as well. It would seem that using the zener would require putting it somewhere else in the circuit/system for it to generate the desired effect.

 

After reading all these threads i will stick with a lead acid battery in my truck. Don't see where AGM will benefit me in anyway.

 

Great question so? In trying to get through to Northstar’s customer service the phone was answered by Alpine Power Systems who then gave me the number to Northstar’s Tech Support.

 

If nothing else there's a marked reduction in corrosion.

 

So here we are about 2 months into it and I finally took a moment to hook my smart charger up to check things out and as I suspected?…I didn’t even need to plug it in.

I suspected that I wouldn’t need to plug it in because the needle on my dash voltmeter pretty much stays at a touch over 14 volts and despite the fact that I have a 20L AstroAI freezer/fridge (I leave plugged in and comes on every time I start the truck) my X27 battery is fully charged without charging it up once a month.

My most sincere thanks to those of you who walked me through wiring up my own fuse protected diode.