The NorthStar AGM Battery + Voltage Booster Upgrade

For 3rd Gen, I'd put money the diode would go at the "10A ECU-B No. 3" fuse going to the Combination Meter- it's sensed there and communicated to the ECU along CAN.

 

There's no need for a fuse on a sense line. It's not providing any power. It's just being used to read the voltage output of the alternator, so current draw should be almost nothing.

Why they put a 7.5A fuse on the 2nd gen alternator sense line makes no sense, especially when guys are putting 1A rated diodes in its place without issue.

It's a possibility, but I was basing my guess on info from my WRX which is similar to the 3rd gens because it doesn't have a labelled alt sense line. There's a line that goes from the alternator straight to the ECM. If you depin it, the alternator runs full blast all the time.

 

If I have a standard car battery as my main and an AGM for my aux do you think upping the charging voltage for both will cause an issue? They are linked via smart isolator.

 

The higher voltage would likely cook your main battery. You'd be better off running a DC-DC charger to increase the voltage to charge the AGM.

 

Or just spend the same amount and double down on AGM

 

Just ordered the fixed voltage booster, thanks for the info.

 

This.

Wiring two different types of batteries together will not work properly.

 

I added an arrow to the line i'll interrupt once i receive the "booster".

Personally, I would be weary of removing the 10A fuse and replacing it with the booster which isn't capable of handling that much amperage since that particular ECU-b No. 3 circuit appears to be connected to the a battery source. Do you know how much amperage is getting pulled through there? I have no clue so I can't say.

 

Exactly, and since this scenario is COMPLETELY different than the ALT-S wire scenario I would DEFINITELY keep the fuse and actually consider the $50 Fuse/Diode from OZ.

 

Awaiting your results for sure....

 

Actually from my research that’s only really true if you wire them in parallel for use. Having and AGM and “regular” battery to charge via a smart isolator doesn’t impact a ton (they disconnect when the truck is off and the aux battery is being depleted). If they were wired in parallel for long term regular use, then your statement is accurate.

 

True. However, it's still not a good idea. The AGM will always be undercharged if you run the correct lead-acid charging voltage, which will shorten the life of the AGM. If you run the proper voltage to charge the AGM, the lead-acid battery will always be overcharged, which will kill it.

Either way you're better off running the proper voltage to each battery.

 

Also true, but there is a difference between a deep cycle charge and a float charge. My fridge use would put me more on the float side, so I think I'm good with a regular charging voltage of 13.6 while driving. If I were to be using the AGM for deep cycle use it might be a different situation.

 

That is what I intended to say, even though I did not articulate it.

Given the original post, he did not mention using an isolator, so I assumed he would be using a combiner such as a Blue Sea ACR.

Certainly, wired separately with a DC-DC charger, you can use any type of battery with any other type of battery.

For the record, I am running an Odyssey as my starting battery, with the diode from OZ to increase the charge voltage. My second (house) battery is also an Odyssey, running off of a CTEK DC-DC charger - with the higher charge voltage.

Both of my batteries are the same model, so that in the rare event that the starting battery croaks, I can physically replace it with the house battery, and be on my way.

 

Did you get the booster yet? Curious to see if it's a solution for us 3rd gen guys.

 

Nope. It's coming from Australia, so the shipping is rather slow. Wasn't a cheap date, either.. $102 by the time it gets to my door

 

Not cheap at all! Well keep us posted please.

 

Have been working with Northstar to warranty a 24F AGM and the guy I've been speaking with recommended the MK3 as Toyotas are notoriously low voltage for AGMs. Funny that I find this thread right afterwords...

 

Yep, same thing the NorthStar rep mentioned to me as well about Toyota’s being notorious for low voltage, even before I mentioned I was doing this for a Toyota.

 

Even with the MK3, I feel like I'd be a little low. I'm sitting right around 14V at 1500 RPM idle, so adding .5V would get closer but still seems a bit low. I guess better to be 14.5 than 14.0 though.