Another Dual Battery Setup

[e60ral]

anyone needing more than 40A probably isn't asking questions about the basics

 

[Bumbo]

anyone needing more than 40A probably isn't asking questions about the basics

It’s just how I have my lighting setup… we do some night activities where we use some of that light for field use, so I wanted it off the LVD protected house battery.

I also wanted to simplify accessory wiring to a single fuse panel at the time. So my design did benefit from the higher amperage rating of the ACR.

As mentioned, just depends on the design, but with low amp load devices like fridges and radios, a DC-DC is an excellent option.

I have nothing against the DC-DC, I use them all the time, its just another method and a very good one.

 

[FLY_FISHING]

Hi guys, finally got my version of Dual Battery completed. So far I'm pretty happy with it, it was an experiment for me. So, I went a different route. I have a 16 4runner with a pretty new battery, so I didn't want to replace it just yet, and adding an additional AGM battery means that the AGM battery will not be able to be charged past 80 percent due to required voltage, so it will end up sulfated, which is bad.

So my solution was to go with a DC-DC charger to charge the additional AGM properly. I found this C-Tek that seems to work flawlessly. It was $210 dollars shipped, so for about the same price as a good solenoid, I got the charger. I purchased the Off Road Engineering mount and the Odyssey Group 35 - 65 Amp-hour battery. Shouts out to Off Road Engineering, first they told me it would be 2 weeks wait, but then the thing came in 3 days, so I was very happy with the mount, very good quality and it fits perfectly.

I got everything installed and immediately the battery charged fully. The thing about the C-Tek charger is it uses an intelligent charge to fully charge the battery properly, much better than an alternator charge.
This type setup is the Australians preferred setup.

So, for the Pros and Cons.

Pros.
The C-Tek charges the battery up at 20 amps, so it will never tax your electrical system more than needed and will not harm your alternator.
You will always get a 20 amp charge at idle, regardless of anything else going on in the vehicle. 65 hour battery flat will charge fully in 3 hours driving or idling.
The C-Tek charger acts as a battery isolator.
The C-Tek charger also will charge with a solar panel, which I plan to add next.
No need to add diodes to the vehicle and possibly cause other problems with higher voltage.
Ability to run both a regular lead acid and AGM battery at the exact same time.
Cheaper, only having to add one AGM battery is cheaper than adding two new AGM batteries and a diode.
No need to plug into an AC charger at home to top of the battery to prevent sulfation.

Cons.
The C-Tek charger only charges at 20 amps, so it's slower than an alternator charge at higher rpm. Although there are other model available for higher charge rates.
There is no battery solenoid, so reverse jump starting is not possible, although I carry a single cable in the engine compartment I can simply jump if needed, so it's not a big deal in the event a reverse jump is needed.
The charger takes up space in the engine compartment.

In the future I plan to add a solenoid to the mix to get the best of both worlds, where I can jump the two battery's to get a faster charge and reverse jump start if needed, but for now, this setup works sweet.

My fridge goes for about a day on the 65 hour battery, which combined with my generator and/or solar panel for recharging in the day is just about all I need.

what part number is that ctek?

 

[Airgazm]

Looks like the Ctek 250 dual I created this post with was discontinued. Looks like the replacement model is the Ctek 250SA. I only paid a little over $200 for mine, but now they seem to have gone up in price, like $250-$300

 

[Speedsurfer]

Great

Hi there, thanks for sharing this. I'm really interested in this because for those of us with new 4Runners with stock batteries it seems like a waste to toss a good battery. I've noticed that some other people mounted the CTEK near the front grill because they were concerned about the heat rating of the unit being left in the engine compartment. How is your unit holding up since the installation? Thanks

 

[Bk6418]

Has anyone looked into an external voltage regulator. I am still in the research and learning phase of these but they may be part of the solution. (The link is to a page to determine what charger you may need not a product.)

Selecting a Charging System | Balmar

Secondly I am under the understand that AGM batteries should not be brought below 50% with out risk of sulfation, hence lowering its overall life as well as "Amperage Hour" value. I believe the automatic "low-voltage disconnect are below this threshold but I could be mistaken. I believe it to be 12.1 volts state of charge (taken after 24hour of no load or Charge if you have time for that)

I believe these regulators are used in conjunction with your current alternator and produce the required voltage at the battery. Full disclosure, I am not an expert on this but I have done alot of research and schooling on the matter and if nothing else this will generate conversation.

 

[jhguth]

50% is the rule of thumb for normal flooded batteries, AGM is probably about 80%. Generally the AGM batteries used in this kind of context are dual purpose batteries where they have good deep cycle (that's what deep cycle means, able to be greatly discharged) but with sufficient cranking amperage to also use as a starting battery.

That doesn't mean that AGM escapes the effect of cycling a battery deeper reducing the number of lifecycles, it just means that you can discharge it a lot more and still have more lifecycles than a standard flooded battery.

The highest low voltage shutoff for my fridge is 11.8V, on my battery 11.8V is about 50-55% discharged. In my case I only have a single battery so I generally use the highest setting for peace of mind (even though the truck starts up normally when I use the medium setting, which I do use in some specific situations). Since my full battery is 110Ah that means I have about 55-60 usable Ah of capacity for my fridge at that shutoff level.

The bigger risk for sulfation with an AGM battery would be not properly charging it, if it's not fully charged for a long period of time you will get sulfation which will reduce capacity and lifespan, which is why it's important to properly charge the battery or at least do regular maintenance charging.

 

[missionman]

I have a lil input here . .
I have 2 Weize 105ah LiFePO4 batteries in my 4runner in parallel being charged by a Victron Orion XS 50 amp 12/12 dc to dc charger.

starter is connected to my parallel batteries directly. These batteries are both starting batteries powering a winch, a high powered stereo and some bus bars.

I have no "AUX" battery or anything like the auto industry dual battery start/aux combo. I have a plain parallel bank for everything. Its better this way and make WAY more sense.

Orion has no diagrams for my setup but i need the Orion XS to set a specific charge voltage to not trigger BMS cut offs on one battery so i keep batteries charged at 99% and charge them individually every 3-6 months so BMS can maintain calibration, then i balance them manually and reconnect my cables in parallel. Hes my diagram. all LiFePO4 batteries charge to FULL at different times.

You dont want to charge with your alternator. that will cause voltage mismatches, unbalancing, overcharging, etc - youll destroy your LiFePO4 system or lithium bank and its got nothing to do with each battery having BMS over voltage protection. Im talking about one battery reaching full first at say 14.2 volts while the other keeps going to 14.5 or 14.6. This will destroy your parallel bank. therefore under charge your bank. Set your bulk and absorption voltage to 14.0v and float to 13.5 or so. Some even input 13.8v for bulk and absorption. Weize themselves recommended the 13.8 v charge with Orion XS to address the unbalancing fight of parallel LiFePO4 batteries. This is how you charge to 80%, 85%, 90%, 95% or 99%. you can fine tune your SOC based on your bulk, absorption and float voltage.

So you use a Victron Orion XS 50 amp. Why 50 amp? To not OVERWORK your stock alternator (130A). and you set your absorption voltage to 13.9 or 14 volts so you only charge them to 99% or so. Only charge them to 100% individually every 3-6 months. It is necessary to charge them full every so often but NOT at the same time or youll end up unbalancing them.
My batteries were of the same batch, one ending in 063 and the other ending in 064. Battery A has 0.08 more capacity than battery B. hope this helps someone! God bless yall!

 

[gordonp]

starter is connected to my parallel batteries directly. These batteries are both starting batteries powering a winch, a high powered stereo and some bus bars.

I have no "AUX" battery or anything like the auto industry dual battery start/aux combo.

In the 1990's, I too paralleled my dual batteries (in FJ45 V8-Land Cruiser pickup). Both batteries were the same (flooded acid) chemistry, and rated the same capacity. It worked. And a high-amp contactor was simple, when I wanted to separate or combine the two.

But not now - these days, I use a RedArc controller between my main (house) battery, and my AUX. Initially, they were different chemistries (flooded lead-acid from Tahara, AGM from Energizer/Costco) and different capacities - absolutely, they could not be paralleled for long-term charging (i do have a self-boost contactor for starting with a dead MAIN battery, allowing short-term parallelling). Since initial installation, both MAIN and AUX are now AGM, but different capacities, different uses, and I'm sure are aging differently. They are best with their own, separate, charging circuits.