Too good to be true dual batt setup?

[wrcsixeight]

Luis, in your photo with the solar panel on the ground, You would be very surprised how much panel amperage is reduced by even the small amount of shade provided by the grass at the very bottom.

I have a battery monitor which hooks into my charge controller. It will tell me what the MPPT charge controller is receiving from the panel, as well as the output, after it has done it's DC to DC conversion thing. It also counts amps into and out of the battery, and many other functions.

I have noticed a 1.5 amp drop when there is a thin line shadow from a single power line. Some panels are more tolerant of partial shading, but most are affected greatly even by the smallest shadows.

When using battery voltage to interpret battery state of charge, one must take into account surface charge. After driving at night, my voltage will read 13.3 or higher for upto 2 hours after the engine is shut off.

A simple voltmeter would indicate a fully charged battery. My Amp hour counting battery monitor might show that I'm only at 85% SOC despite the 13.3 volt reading.

For a voltmeter to be accurate at all in determining state of charge, the battery should be removed from any charge or discharging sources for hours before taking a reading.

 

[dieselcruiserhead]

That is the biggest advantage of the Luna IMO, the gauge.. You can get gauges from camping and RV places though...

 

[Poorboyota26]

http://www.pirate4x4.com/tech/billavista/dual_battery/my_dual_battery_setup.htm

Here's a very simple but slightly unattractive solution. I saw lots of these type setups while serving in the USCG - they work very well.

I'd hate to have to ever trouble shoot that jeep!!!!!!!:Wow1:

 

[Rbertalotto]

The next step up in service and complexity over the simple relay would be a relay that senses when the starting battery is fully charged and waits until then to connect the 'house' battery to the alternator. They're known as "Voltage Sensing Relays" or "Automatic Charge Relays."

 

[Pskhaat]

Do FORD or GM trucks have a separate part # for the relays or always connected?

 

[mwfish]

No matter if you go with a simple system or a more complex system size matters. Use quality wire, of proper size, and keep an eye on the voltage drop. Depending on what battery(ies) you are using you will need 14.2, 14.4, or 14.6 from the alt in order to return charge to the battery(ies).

 

[ldivinag]

I've been doing this for about 10+ years in my FZJ80. The solenoid closes based upon the Toyota OEM "Alternator Good" signal (asserts once the alternator is producing sufficient power).

The solenoid can also be closed (batteries connected) from a switch inside the cab for auxiliary starting.

any chance of pix of this "good signal" thing?

got like a diagram or something?

thanks...

 

[esh]

I bought a dual gauge like below off ebay.com.au. Works great. Has a backlight I need to temper with some tint film, but otherwise no issues. It is barely smaller than a 2-1/16 gauge.

The manufacturer site has all kinds of voltage displays and electronic gizmos finished or DIY. They have some meters with pot-adjusted high/low alarms.

For a voltage sensing relay, I got a BEP 300 amp marine unit. It has a switch for auto/off/combine and has a connector to allow a wired remote switch. Has massive amp rating- 300 continuous, 1250 cranking. You can find them under $150 on ebay from time to time.

 

[AxeAngel]

I'd hate to have to ever trouble shoot that jeep!!!!!!!:Wow1:

It would take hours to trace where all those wires go. He needs to clean up those wires a bit.

My bluseas ACR and remote switch will be here next week. Will take detailed pics and create a How:To for all.

-Sam

 

[CJCA]

http://www.pirate4x4.com/tech/billavista/dual_battery/my_dual_battery_setup.htm

Here's a very simple but slightly unattractive solution. I saw lots of these type setups while serving in the USCG - they work very well.

I can't believe he mounted it on the dashboard. :Wow1:

I used a Cole-Hersee switch years ago for dual batteries, but I mounted the thing under the hood.

 

[AxeAngel]

Anyone know where I can get those battery monitors or similar like the NL kit.

Prefer one panel that shows the voltage of both batteries.

Thanks
Sam

 

[JeepTreeHouse]

I was in my local NAPA talking dual battery setups when one the guys asks me outside to look at his nicely restored bronco. He is running a simple heavy duty relay with remote on from his primary battery's positive to his deep cycle. He turns the key and she starts to charge. Cuts off the truck and the connection between the batteries is broken and he runs his accesories off the deep cycle. Says he has had it this way for years and works fine. Realy and wires cost about $80 and he has a set of jumper cables in case he needs to jump the primary. Worse case he can swap batteries.

Is this too simple? I like the idea and certainly don't need an led pandle and digital switch if this will work.

Thoughts?

So this way, with two dis-similar batteries, ie a standard and a deep cycle, will be fine with each other all the time when the truck is running? since with this simple selinoid they will be always connected when the key is in the on position correct?

 

[dzzz]

Dissimilar doesn't matter as much as the voltage at each battery.

Automotive deep cycle are more tolerant of higher voltage now out of necessity of living with a regulator/alternator designed for starting batteries.

Realistically with one regulator/alternator the voltage is not going to be ideal. But usually not so bad that the deep cycle will have a greatly shorter life. An inexpensive safe system will never full charge the deep cycle. Or may not even charge it at all. A solenoid/switch based system may expose the deep cycle to too high voltage, but the battery does get charged.

The gold standard is two alternators with three stage regulators that are set up for the specific batteries. But in a vehicle with just two batteries (as opposed to two battery banks) there's little reason to go for the super primo solution.

Personally on an expo vehicle I would replace both starting and house (when old) with Odyssey/Sears Platinum and tweak the max voltage as necessary.

It not safe to wire a switch that can cut off both batteries from the alternator. A switch should simply take the house battery in/out of the charging circuit. The starting battery should always be in the circuit.

 

[wrcsixeight]

In an Ideal world, both batteries when paralleled by the solenoid would be the same age,make, manufacturer with exactly the same length and thickness wires from alternator to battery.

There is not usually a problem with a non ideal situation, but you should check the voltage on the second battery with the engine running at idle and at higher rpms.
Sometimes issues can arise where one battery continually gets overcharged and the other under charged. You will overestimate the amount of current making it to the second battery, so anytime you have access to the grid, you should plug into a regular charger to top it off. The fatter the wire you use from the solenoid to second battery the more effective your alternator will be, and the ground wires must be equally fat or there is no benefit.