dual battery install (1 Viewer)

[dugsgms]

Getting ready to do my dual battery install...Here's how I was thinking of doing it, looking for input/opinions in case there's something I'm missing here. What do you all think?

 

[Overlandeffex]

Put all the grounds together.

 

[dugsgms]

Good call, was planning on grounding the aux battery to the engine block.

 

[bajaphile]

Maybe you're already planning on it, but adding 150amp circuit breakers per battery isn't a bad idea on the positive leads to the isolator.

 

[Granite Grinder]

And winch should be wired to crank battery. I'm not entirely sure why, but I have done a ton of research

 

[SmokingRocks]

Reasoning:

1. I wanted to keep my Aux battery (BATT 2) as a savior batter if things wen wrong for battery 1 & 3
2. This Set up worths THE BEST for solar charging.
3. 3rd Battery is to minimize the impact of 24/7 cycling on the main battery from the freezer and fridge
4. The relay between the main battery and 3d battery is dual sensing. Meaning that when the solar panels fill it up it will close the relay and charge the main battery. Then the savior battery
5. Winch on the aux battery isn't an issue as long as you are linked during the pull.

 

[dugsgms]

There seemed to be a lot of opinions on which battery to wire the winch to, all valid opinions but seemed to really depend on the particular configuration and particular conditions. Thats why I plan to add the Blue Sea 9001e switch, its a 1/2/1+2 battery switch. I figure it will give me flexibility on which battery I pull from as well as taking half the amperage load off the ACR while using both batteries to winch. I figure that with the switch I can pull from both batteries regardless of whether or not the ACR is closed(in the event of false switching due to voltage drop while winching), pull from just the aux in the unlikely event of a engine stall(deep water crossing) while not having to worry about not having enough juice to crank engine over after I'm back on dry land, have the ability to bypass the ACR in the event of a ACR failure as well as having the added bonus of not having a live wire running to the winch when not in use.

 

[JCruse]

I have a question. Why should we bring all grounds together?
I grounded my Aux battery to the fender and to the block, matching the layout of the stock battery, and also grounded one battery to the other with a 1 AWG cable. What is the benefit of adding more grounds?

 

[bajaphile]

Phase 1: Connect grounds
Phase 2:
Phase 3: Profit.

That's all I know.

 

[Qball]

This has just been delivered to my door.

 

[dugsgms]

I have a question. Why should we bring all grounds together?
I grounded my Aux battery to the fender and to the block, matching the layout of the stock battery, and also grounded one battery to the other with a 1 AWG cable. What is the benefit of adding more grounds?

You really don't need to have a single ground point, they way you did it is perfectly adequate. In fact, the additional ground wire in between the 2 batteries is redundant.

 

[SmokingRocks]

I have common grounds in the engine bay, interior cab, and rear cargo area that collect many grounds in each area and then take them to the frame. The frame is the biggest gauge wire you have. Running an 0 gauge wire to the rear is a waste of money.

 

[SmokingRocks]

Another thing I learned from experiance that I'll share with the group is to be mindful on which battery you run your accessories from.

If you are or are planning on running a solar panel on the roof then run ALL of your accessories (winch doesn't matter) from the main battery.

The reason is that as the accessories drain the voltage the solar panel will replace it. Once the main battery is filled up to float voltage and as long as the solar is putting out amps it will AUTOMATICALLY trigger the charge sensing battery relay. Note: The solar will always be tied to the main battery (if you want to utilize the charge sensing relay to automatically link both batteries when the main is up to float voltage)

So what happens if you have all of your accessories off the aux battery and you keep your main battery as the 'clean' / always charged battery?

1. The main battery is always at 12.8 and when the solar panel is generating charge it reaches float voltage very quickly
2. Your aux battery has been discharging while you are using your accessories and is at 11.8 volts
3. AS SOON AS the main hits float voltage the battery relay is triggered and links the two batteries
4. A large amount of current rushes into the aux battery from the main battery in an attempt to equalize the system that is now in parallel.
5. Since your solar output is likely 10 amps max (not 80 like your alternator) the main battery's voltage drops to less than float and trigger voltage as it sends current to the aux battery (relay trigger voltage is ~13.3V, Float is between 13.8-14.2V)
6. The charge sensing relay now senses the main battery is under the trigger voltage and disconnects the two batteries.
7. As long as the solar is putting out the main will reach trigger / float voltage very quickly once disconnected from the aux battery and the whole cycle repeats.

I saw this first hand in Moab, my buddy has a 100w panel flat mounted on his roof and the same dual battery system as me but wired all his accessories to the aux battery. On a sunny day in Moab the relay was cycling like every 30 seconds it was insane.

Now you could wire your solar to the AUX battery but it won't help the main battery unless manually linked. Or if you wanted to get creative with diodes you could turn the single charge sensing relay into a dual charge sensing relay (or just buy a blue see 7600) and put your solar panel on your aux battery.

I plan on running my starter cable to the AUX battery so that as long as the main battery has enough voltage to trigger the starter solenoid the starter will get the 12.8 volts from the AUX. Its better than draining the main, then linking them to start (pulls the cumulative voltage down).

This is my experience.

 

[Funner]

I like simple, so your diagram looks good except two things already mentioned. 1) Put your winch on the main battery. You don't want to winch off the auxiliary because it won't receive current from the alternator until and unless the main is fully charged in. Normal circumstances this could take several minutes or longer and could be detrimental to the house battery that's being killed by the winch with no input from the alternator. 2) fuse or circuit breakers as close to the positive terminals on both batteries on every line. Probably 10 amps would be enough for the lines feeding the inverter, 50+ on the main charging lines.

 

[landcrshr]

With the Blue Sea 7620, you can combine the two batteries manually. The 9001e battery switch would be unnecessary.

 

[SmokingRocks]

I like simple, so your diagram looks good except two things already mentioned. 1) Put your winch on the main battery. You don't want to winch off the auxiliary because it won't receive current from the alternator until and unless the main is fully charged in. Normal circumstances this could take several minutes or longer and could be detrimental to the house battery that's being killed by the winch with no input from the alternator. 2) fuse or circuit breakers as close to the positive terminals on both batteries on every line. Probably 10 amps would be enough for the lines feeding the inverter, 50+ on the main charging lines.

Thanks @Funner I intentionally left out the breakers to keep the diagrams easier to read.

When I winch I have the vehicle running (with hi-idle switched on) and I manually link the batteries. I've got 0 Gauge going between batteries with 100amp breakers at each end. 4 gauge wire heading back to the 3rd (Rear) battery, 50 amp breakers on each end and a Blue Sea 7600 dual sense isolator with manual override. The inverter is fused to the Rear battery and the solar input is direct to the Rear battery.

So when the rig is off and the fridges are running (off Rear battery) this is how charge flows when solar is active:

1) Rear Battery is getting more amps than its discharging, reaches float & Triggers Blue Sea 7600 links Rear to Main Batt.
2) Main Batt charges to float voltage & triggers dual battery relay, links Main with AUX "Savior" battery.

Solar--->Rear Batt--->Main Batt--->Savior Batt



When the rig is on this is how it flows:

Alternator--->Main Batt---@13.3V---> Savior Batt
Alternator--->Main Batt---@13.8v---> Rear Batt <~~~Solar Panel


Also note that I've only had my rear battery installed for a week, I've yet to see how the solar will handle floating / triggering relays for multiple batteries. It did do fine triggering the link from main to the savior battery though so I expect it to work.

 

[BulletHead]

I guess I'll ask the stupid questions.

What is your max winch load current?
What is the total current draw for other loads?
What size (AWG) are your cables?
Where are you placing the fuses exactly?

 

[Desert Dino]

There are basic things to remember
For 24/7 (cooler) you need a deep - cycle battery (DCB)
For starting the rig you need a high current output battery. NOT DCB
The fastest high current Charging device is only the alternator (but it can charge your DCB only 80%)
If you need the AUX bat to help winch trail lights you need high current cables and fuses.
If you want your battery to be 100% redundant for shaving then no loads should be connected to it and you need no need for DCB
I connected all my trail consumers to optima DCB with high current cables and fuses via an automatic system with 3 positions OFF (not connected) Auto and ON (constant connected for winching and starter help)
On top of that I carry booster for redundancy

 

[Desert Dino]

I am using industrial triple insulated welding cables

 

[SmokingRocks]

There are basic things to remember
For 24/7 (cooler) you need a deep - cycle battery (DCB)
For starting the rig you need a high current output battery. NOT DCB
The fastest high current Charging device is only the alternator (but it can charge your DCB only 80%)
If you need the AUX bat to help winch trail lights you need high current cables and fuses.
If you want your battery to be 100% redundant for shaving then no loads should be connected to it and you need no need for DCB
I connected all my trail consumers to optima DCB with high current cables and fuses via an automatic system with 3 positions OFF (not connected) Auto and ON (constant connected for winching and starter help)
On top of that I carry booster for redundancy

So lets clear up the misconceptions about DCB...

Deep cycles will, have been, and are currently used to start engines including big block motors without effort. If that battery has the CCA required by the engine it will spin it just as fast as a starting battery. Not as long perhaps, but as long as the CCA are present there is no difference since the starter cannot tell whether those CCA are coming from a starting, deep cycle or hybrid battery. The FACT is that all batteries at the beginning of their discharge curve start out the same. It is the battery design that alters the shape of the discharge curve. It is true that a starting battery is designed to deliver a high current for a specific length of time after which the voltage drops rapidly. At the other end of the spectrum is a deep cycle which will deliver a much lower current (test spec is usually 23 or 25 amps) for a long period (usually 2 - 3 hours for a group 24 - 27). That does not mean it will not start an engine. It also means that continued cranking on an "untuned" or "balky" engine that a deep cycle would not survive that treatment for any length of time. But it will not be harmed by a 3 - 5 second starter draw

Batteries such as the 2xpower Batteries plus (can't remember who the actual manufacturer is right now) DCB's are totally fine to be used as a starting battery. Mine have been flawless for 1+yr & 25,000mi. Based on the year the 1fz-fe CCA spec is 450-650CCA, most quality group 27 DCB's are rated at around 900CCA +/- 100 (the 2xpower 27 is rated over 950CCA), that is plenty to handle our engine.

So take the 'never used a DCB for starting' statement with a grain of salt.

It is MORE important to have all of your batteries the same type, capacity and in service date.