what voltage are you seeing now?

Good to know, I am also interested in the actual voltage you are getting.

I ordered one because I have noticed the low voltage on my Scanguage for some time...and because I am running out of things to buy for my truck #theendisnear

going to double check with a real meter tonight..

previously was going by voltage being shown by idatalink maestro into my kenwood.

i was reading 13.2 idle most of the time.. think 13.8 while ~1500k rpm before voltage booster . seems super low?

but read 13.6 idle and 14.2-14.4 while ~1500k rpm. need to check at the battery to see if its actually higher then what my kenwood is showing me. Still a bit low but it definitely boosted a bit.

My OBD2 reader always shows about .1V lower than measuring with a voltmeter, yours may be the same. My voltmeter isn't a nice calibrated one though, so the meter could be wrong.

Your before measurements are in line with what I see, idle about 13.3 and 13.8 max.

14.2-14.4 would be perfect for my battery

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My scanguage shows that I get low 14's at initial startup for a few minutes and then drops to about 13.6 any other time I look at it.

hopefully this $70 part can help. I was planning on adding a second batter later this year.

Is anyone who is running the voltage booster seeing a noticeable difference in gas mileage from the increased alternator load?

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Nope, but my fridge battery doesn't need charged.

@Sleeter , thanks for the link.

I've been doing a bit more reading and we don't know what type diode the HKB uses.

You look to be getting .3 volt difference. Most diodes will drop .6. Not sure why that is basically 'halfed'.. but it doesn't actually matter.

You basically need about .25v more and your system would be ideal. You would be getting 14.4 to the AGM and your meters would probably come up to 12.6.

With diodes if one is giving you say .25 then two in series should give you about .5

So... 12V -----|--- 11.75 -----|---- 11.5 <<< that's two diodes in series.

Now the thing is all diodes are a little different and all operating conditions different.. So everyone gets variances and we are talking about a 1/4 volt.

Not sure if you did that "Big 3" wire mod or not, but if not, you might get another 1/4v by better wire and cleaned up connections.

IOW, with your HKB, you have crossed the threshold to the point it's charging the AGM but you are still just a little short of what the AGM wants to see as ideal for maximum performance for the system.

The problem is again, you can't just stick another diode in because it could drop too much voltage and say it dropped .75V might create and over-charging situation and damage both your Batts.

So it's a matter of getting the right combination of parts. In your case you might be down to wires and clean connections.

Thanks. Let us know if you come up with a better solution. Additionally the inline fuse skims off some V but I can't remember how much.

My issue was my AGM battery was not charging, now it charges... Mission accomplished. I do have Big 3 cables on standby for this winter when I get some free time, then I will upgrade.

Will do. I'm going to run this by some EE designer types I know. I just need to get all my facts lined up so they can see the whole picture easily.

Has anyone put the 320 Amp Alternator from this site yet? http://www.qualitypowerauto.com/item...ta-4Runner.htm

Also, will solar panels solve the AGM charging problem with a stock alternator?


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[QUOTE=JDM4LO;2731894Also, will solar panels solve the AGM charging problem with a stock alternator? [/QUOTE]

Basically anything that puts 14.4 volts ( or whatever the manufacturer recommends ) into the battery will work.

So yes, solar can be another solution. $2 worth of diodes is a lot cheaper and takes up less space though.

Woa woa, tell me more about these $2 diodes. I just spent $70 ordering that HKB fuse from Australia.


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It's all over the Internet in many forums and YT vids.

that 'fuse' you speak of is a regular fuse with a diode attached in series. Looks like this......


-----|--~~~

The fuse facilitates placing it in the circuit. The Diode drops voltage when placed in the circuit by it's physical nature. We are basically using what has most often been considered a negative aspect of the diode(voltage loss when inserted in circuit ) to solve a negative created by Toyota ( voltage regulation too low for AGM ).

They are used everywhere in electronics and have been forever.

In this scenario the voltage drop fools the Toyota electrical scheme into thinking it's too low, and it continues to deliver more voltage.

There is a threshold that needs to be crossed for the AGM battery. This diode voltage drop 'trick' basically facilitates crossing that threshold.

It's not a one size fits all perfect thing though.

Silicon diodes ( most common these days ) drop about .6V. It's just the way they are.

So for instance if you had a 12V circuit and needed to power a 9V device.

You put 5 diodes end to end dropping .6 each and you have 9V.

+12>>> --|--.--|--.--|--.--|--.--|-->>9V

So this 1 Diode 'trick' for the 4R just happens to get us inside that AGM window. Maybe you get 14.1, 14.2, 14.3, or the ideal 14.4. What we don't want is to go over 14.9.

So whatever we fool Toyota with it adds back. We fool it with .6v drop, it adds that back. So if we had 13.5 before, now we have 14.1 and the AGM says ok, I can deal with that.

All this is very coincidental and convenient at the same time. Not all diodes are alike. If you put an LED in there. It might try to drop 2Vs. That is their nature. Each color has a different drop from about 1.5V to 3.5V. Still a diode, just a different kind.

So it seems like we need like a Silicon diode and half. Well no such thing. But... there are Germanium diodes.. older and not as common these days.

They tend to drop -less- voltage. So if we could find the right combination of silicon diode ( 10cents ) + a Germainum diode ( $2 )in series. Maybe we could get .8 or .9 volt drop. Now that 13.5 from Toyota would jump up to 14.4 or the ideal AGM voltage. AND.. it would still be in safe range for everything else, and it would still be fused as normal.

So the trick is to find just the right diode pair for your truck. There are a million different diodes out there and they do publish their specs but it's for a specific temp / volt / amp. So a diode that specs on paper at 1V might measure .7

But this is what everyone is doing and most people are fine with being 'close and good'. No matter if they are doing it for 4W or Audio or whatever.

I'm just trying to find a way we could have a tuneable setup to dial in that extra or lesser .25 volts to create as close to ideal for the AGM. Otherwise you still aren't getting your complete money's worth from it.. unless you condition it from time to time with something like that CTEK.

Unfortunately the part we use to do it is a finicky part. You can have a bag of the same part and many different results.

But even with just two diodes we have a lot of options.

Silicon - S
Germanium - G

S --- works for a lot of people, not ideal
S + S --- too much voltage - will ruin system
S + G --- could work and maybe be ideal
G + G --- could work and maybe be ideal
G --- likely too little change to meet AGM needs

Only issue is a lot of trail and error. No one size fits all.

If we could get a 14.5 MAX and maybe drop into 14.2, I think that would be a good range based on results I have read from many people.

I see. But as of yet, no complete diode solution for sale or DIY kit for the 5th gen 4Runner?


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