MPPT for truck, alternator/solar

[Bluejets]

I cannot have the cranking battery for my truck die. It's either an isolator or diode to prevent ANY discharge leaving me stranded in the middle of Ocala National Forest. I will use this truck to camp with the family, to the beach, and still drive to work and park in a secure lot(hospital).
I'm not optimizing the charge of the battery if the alternator only puts out 13.9, this is why I thought I could use a mppt charge controllerto bump up the volts to 14.8 .

The aforementioned diodes were to isolate incoming charge controllers, not to give any discharge protection.
As debe says if you need that then you have to follow his direction.
However the range of discharge would tend to be rather small given a cutout of 13v.
Nothing is going to boost the output from the alternator except for alternator regulator changes or sense changes.

 

[kellys_eye]

A properly working vehicle alternator will output 14.2-14.4v on-charge. 13.8V is the off load voltage of a fully charged battery.

Without knowing the internal structure of the charge-controller commenting properly on isolation diodes etc is speculative - no harm in adding them!

Using an MPPT device guarantees the output is 'good enough to use' regardless of the input (to an extent) but if you ignored the MPPT effect, charging the battery is a simple matter of paralleling all source voltages but using isolation diodes on each.

This way only the device with the largest output voltage will charge the battery - no switching required.

All you're 'adding' is the MPPT function to ensure the wind/solar sources are up to requirement but putting one of those on each source doesn't change anything in respect to 'diodes' - BUT, the device you suggest using doesn't reveal (to me) what arrangements it has for source isolation. Diodes may already be included.....

Split-charge diodes (as they are otherwise known) aren't excessively large or expensive:

https://sterling-power.com/products/split-charge-diodes-70-200a-2-3-outputs

so on a system with (say) a solar panel, alternator and battery, you could add an MPPT to the solar panels and connect the output of the alternator to one split-charge diode, the solar panel (via MPPT) to the other diode and the diode common to the battery/load.

IMHO the MPPT-controller you suggest is a step to far. For one, it's a single source for failure (i.e. if it goes wrong it takes out all your charging sources bar the alternator) and it introduces unnecessary complication. Separate units would be preferable (to me) and I probably wouldn't even bother with a wind source. A decent sized battery - even if you have to parallel up and remotely fit the extra - would be far more convenient.

Properly sized (i.e. do your maths!) you should never be short of power and, for emergencies, a small petrol-powered genny (a 750W inverter-generator) would get you out of any sticky situations.

 

[debe]

The Redarc isolator is a Voltage controlled Relay, commonly used for charging extra batterys in a RV environment. Its very unusual to use isolating diodes in these situations these days. You will get far beter advice on these systems on Caravaning Forums here in Australia. Most caravaners/RVers here use these types of systems with Solar & charging from vehicle altenator. And there is no need to split the systems with Diodes, The feed from the altenator & the Solar system are quite happy both feeding the battery at the same time. Have never had any problems with my setup where the solar panels on my van are feeding the battery at the same time as the vehicle altenator.

 

[debe]

The Orig poster doesn't say what year & what the vehicle is. Newer vehicles have so called smart altenators that are controlled by the Engine computer. They enitialy charge at 14V + then drop back to 13.8V, so you canot afford any voltage drop through Diodes.

 

[Blackout]

The Orig poster doesn't say what year & what the vehicle is. Newer vehicles have so called smart altenators that are controlled by the Engine computer. They enitialy charge at 14V + then drop back to 13.8V, so you canot afford any voltage drop through Diodes.

My truck is a 2016 Toyota Tacoma. I was hoping to find another solution than the Redarc isolator and Redarc dcdc charge controller as they are quite expensive. Thanks Debe for your input.

 

[debe]

Some of the Smart altenators will increase there voltage with the lights on, worth checking. Also the Negative lead you run to the Auxilliary battery should be connected to the vehicle frame near the battery, not the battery terminal. As the lead from battery to frame is part of the load sensing for the ECU. This may help in increasing the alt voltage as the ECU senses the extra load to charge the Aux battery.

 

[kellys_eye]

Older alternators should NEVER be used without a load connected as the output can rise beyond safe levels (in an open-circuit). The Redarc device is unknown to me - does it load the alternator output to maintain regulation or does it actually 'disconnect' leaving it floating?

 

[debe]

The Redarc device is just a voltage controlled relay, which when activated connects the positive terminal of the vehicle battery to the Auxiliary battery. It doesnot disconnect the Altenator.

 

[Blackout]

Older alternators should NEVER be used without a load connected as the output can rise beyond safe levels (in an open-circuit). The Redarc device is unknown to me - does it load the alternator output to maintain regulation or does it actually 'disconnect' leaving it floating?

https://redarcelectronics.com/collections/in-vehicle-dual-battery-chargers

 

[Blackout]

The Redarc device is just a voltage controlled relay, which when activated connects the positive terminal of the vehicle battery to the Auxiliary battery. It doesnot disconnect the Altenator.

They also have a calculator to get the correct size charger for accessories.

https://redarcelectronics.com/pages/dual-battery-selector

 

[Blackout]

The Redarc device is just a voltage controlled relay, which when activated connects the positive terminal of the vehicle battery to the Auxiliary battery. It doesnot disconnect the Altenator.

They sell both isolators and chargers. I can get an isolator, but wanted the most efficient (mppt) charger and questions arose if a wind/solar dual input charge controller is the same just rebranded as Redarc. Thanks

 

[debe]

I would not be keen to use that Wind/Solar MPPT unit. Your altenator is capable of supplying more current than that unit is capable of, & its not designed for use with vehicle altenators. Also the Wind side of that unit uses that large resistor as a Load dump. Not exactly what the vehicle altenator needs.

 

[debe]

http://caravanersforum.com/viewforum.php?f=111 If you join this forum (its free) & ask questions you may get some answers.