Seems something like this product here would answer these issues pretty well. Handles solar as well.

Intelli-Charge DC/DC Solar Battery Charger 12/24 Volt 25 Amp Switchmode

That raises the voltage?

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Yes, it's designed to raise the voltage for the type of battery, in the case of AGM, it's 14.4v, at a max of 25amp charge, from a system that put's out much less voltage, so if your voltage is 13.4 or more, this will start charging the second battery. It also will accept solar panels and charge your second battery from the solar panel and the main battery at the same time. The only thing I see this not doing is backwards jump starting.

This is the smoke and mirrors that was referred to earlier in the thread. All this unit does is convert the already limited amps into watts. On top of that these coverters have reliability issues.

I don't see anything in the manual, the output voltage looks like it mirrors the input (except when input is higher, has mppt controller)

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I haven't really researched these at all, but from what I'm seeing, I don't see any reason why these would be smoke and mirrors. It's pretty easy to build a DC-DC charging circuit. These are not converters, this unit is a battery charger, instead of an input of AC 110v, these use a DC input, not much too it, simple circuitry.

With olm's law, you can do a lot of things with resistance, voltage and current, your simply trading a bit more current to boost the voltage up, but not by much and your alternator shouldn't have too much trouble with a 25amp charge, your headlights require almost that much to run, I would think even at idle you would be charging pretty decently, but I have no real world experience, testing any of these.

The brochure will show that the voltage output is dependent on what type of battery it's charging, in the case of AGM, it's 14.4. But it's going to vary the voltage somewhat during the charging cycle to top the battery off, get fully charged and not overcharge.

https://www.australiandirect.com.au/...DC25_Broch.pdf

This fuse definitely works for my application. I never plugged into shore power for the last 7 days and my fridge battery has stayed charged and operational. I drove 2 hrs Monday, 2 hrs Tuesday, 1hr Wednesday, and 1.5 hrs yesterday (Thursday). I'm very happy with these results. Additionally the last 3 days have been very hot and my truck has been parked outside in the sun with my fridge set at 37*.



Below is a picture from this morning.




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If you have isolated batteries, why is your starting battery not fully charged?

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Its a little low because last night I spent about 2 hrs cleaning the truck with the dome lights on, normally it's 12.4 - 12.5.

got my voltage booster in.
Running a 31agm, and was definitely not getting charged properly before.

Think i'm getting closer to whats needed to properly charge the agm now.

I am looking at buying one of these fuses to boost my voltage on my 2010 4runner. I have dual agm batteries. The site does not list the 2010 specifically, but lists a 2015. Is there something different? I noticed other 2010 Toyota models listed as well.


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I want to purchase the voltage booster for a AGM in my 2007. The website shows only the 2005 year for the 4th gens. Anyone know what would work with my 07 V-8? I contacted the company, since Australia doesn't import 4Runners they are unsure.

Check fusebox for "ALT-S" fuse. If you have one, then you will be able to use this voltage booster.

Rayofsi thank you for the info! I've got the Sequoia at work today but will check when I get home. I'm running 13.8 - 14.0 volts on the 4Runner, not enough to make an AGM work well and last.


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