217 replies to this topic

[rando]

Thanks! I hadn't seen anything like that. I was looking at much more expensive 12v-12v chargers.

 

I'm guessing I'd need an MPPT controller then? Also, have you found a good way to cut off charging at low temperatures?

 

You would need an MPPT controller to use a DC-DC converter.   I ended up going without a temperature cutoff as my charge rates are usually < 0.05C and always less than 0.1C   But if you want to add one, these could be used:

https://www.ebay.com...OgAAOSwSlBY00uU

[rruff]

Found this regarding alternator charging: http://forum.expedit...e-Pop-up/page23

 

 

"The first key, in my case, was to disable the trucks (2010 Frontier) clever alternator management system. I'm not totally clear on what the alternator is doing, but it is supposedly optimizing battery charging and saving gas by not constantly keeping the alternator under load. I imagine other newer vehicles have similar systems these days and options for disabling may vary. For me, I pulled a 20A fuse under the hood labeled "Alternator/Horn". This lets the alternator behave in a good old fashioned dumb way - pushing current to anything that will take it (in this case the camper battery).

I believe there is still an alternator protection circuit built in to keep the alternator from overheating - not positive on this though.

My wiring is double 6ga for the positive from the truck battery (+) to the Victron Cyrix Li-ct battery combiner. (-) is 4ga to the body of the truck close to the camper. When I start the truck, the combiner closes (connects the batteries) as expected. Charging ramps up quickly to almost 70 amps. After about one minute, the charging rate slowly drops to about 40 amps at idle and about 50 amps at higher RPM. After a few more minutes it settles in between 30 and 40 amps. This slow drop may be the alternator protecting itself, not sure. Either way, this is great - I think my alternator is rated at 120 amps so much time at 70+ amps would likely fry it. I did one real deep discharge and the alternator put 90ah back in to the battery with no apparent problems."

[buckland]

Just finished reading. Wow. This is definitely something I would love to do. I have two AGM which equals 110lbs. I have the 165 watt solar panel on the roof. I have a lot of learning to do as I am a basic level electrical knowledge person though just enough to do my own solar and batteries. Soldering them together will be one of the challenges. I have just converted to a side dinette and so have two separate battery boxes for the current AGMs. This is inspiring thread and eventually I hope to make it happen. Thanks for the great write up.

[rando]

Besides being a bit time consuming, the soldering part really isn't at all challenging and gets much faster as you figure out a routine.  With your woodwork skill I am sure you could come up with a slick way of assembling them into a custom sized pack. 

 

As I mention before, I have no idea how many cells the guy on ebay has, so if this interests you, you may want to purchase the cells soon.   

[buckland]

Just checked and he still has them.... price is $180 for the 120 but the shipping was $56. Guess that is the way it goes.

This knowledge base is also a couple steps past my comfort zone ... but that is okay if i can learn as I go (slowly). My AGM batteries are 6 years old .... so might as well test the depth of the water with both feet.

PS woodworking is one skill I have but electrical is not.... In my trade I can say "I don't make mistakes.... I'm just not done"

Won't burn the house down either!  This has been great info and I probably will give it a try!

[rruff]

Maybe a better solution to increasing alternator voltage. http://www.fjcruiser...tml#post6206809

 

You can also buy fuses that do the same thing: https://www.hkbelect.com/

[Vic Harder]

From the iH8mud forum:

https://forum.ih8mud...booster.503895/

 

Detailed post cut and pasted from there below.  IF you do this, make sure you know the consequences.  This will change how your alternator works.  I still think the C-Tek D250S is the better solution, as it only affects the voltage going to the camper batteries, not to the whole truck.

 

 

 

"The generally accepted range of volts out of an alternator for charging is between 13.8 volts to 14.6 volts. On some newer vehicles, (2009 onwards) the manufacturers are electing to us ECU controlled alternators to aid fuel economy and emission figures. Once the starting battery/s reach sufficient charge to start the vehicle (usually around 80%) the alternator drops to a supply voltage of around 13.2 volts. 

 

The minimum voltage to charge a wet cell lead acid battery effectively for optimum performance is 13.8, calcium/calcium sealed maintenance free lead acid is around 14.2 and for flat plate fully sealed agm, gel or spiral wound agm the voltage needs to be 14.4. 

 

So far, the vehicles that I know for certain with these alternators are Toyota LC200, all 70 series and prado 150 series. Toyota started using these alternators around 2009/2010.

 

So using these diode's to trick the alternator is only needed if you are wanting to use one of the newer technology batteries that require 14.2 or 14.4 and your alternator is only putting out 13.8 or less. If you are achieving voltages of 14.6, count yourself lucky to have a perfect charge voltage. Over 14.6, you will cook your batteries.

 

My only concern with these Alternator Voltage Booster diodes is that some of them require you to replace the 7.5 amp fuse with the diode and the one I tried about 12 months ago did not blow even at 20amps.

 

Instead I elect to find the wire that runs between the fuse and the alternator and cut and solder a quick connector in. This allows the ability to replace the diode(built into the quick connector) with a simple jumper wire, returning the vehicle to standard but most importantly retaining the factory 7.5amp fuse."

[rruff]

I still think the C-Tek D250S is the better solution, as it only affects the voltage going to the camper batteries, not to the whole truck.

 

It appears to have an automatic charge system (rather than programmable) and is not designed for lithium. Or am I misunderstanding?

[rando]

If you already have an MPPT charge controller set up for your lithium batteries - then a simple DC-DC 12 -24V converter and a couple of diodes seems like the way to go.   No need to mess around with your alternator output, far cheaper than a DC-DC charger and uses the correct charge profile that is already programmed into your MPPT charger. 

[Vic Harder]

If you already have an MPPT charge controller set up for your lithium batteries - then a simple DC-DC 12 -24V converter and a couple of diodes seems like the way to go.   No need to mess around with your alternator output, far cheaper than a DC-DC charger and uses the correct charge profile that is already programmed into your MPPT charger. 

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