[Wanderlost]

@nworker That is an awesome setup! I've been looking at doing a dual battery system and this has me heading this direction. I'm a a HAM too and know the benefits of LiFEPOs as well.

It's been a couple months. In hindsight, what would you do differently at this point?

Also, where did you get the battery connectors to connect the 4 battery terminals? Are they just copper strap with some electrical tape?

 

[Kilo Sierra]

So I have a couple questions as I'm putting this all together:

I noticed on your installation you mentioned you were using a Renogy 40A DC/DC charger and then later you mentioned (if you had to do it again) to use a 20A charger. Just wondering if that was intended or just a mistype?

I looked at the specification of the batteries themselves and they mention not to charge if the temp goes to or below freezing. Here in the Northeast it can routinely get below this in the winter. I'm wondering it there is to switch the charging off with a simple switch/relay, or should I consider using a manual battery switch to keep it from damaging the batteries on vehicle warm up?

 

[nworker]

@Kilo Sierra I found the batteries don't take anywhere near 40A to charge so the 20A version is adequate.

Yes, LiFEPO4 batteries are susceptible to damage when charging below freezing. In So Cal that is not a problem, so I have not looked at an in-depth solution. I have run across a couple of solutions to add a temperature sensor for low temp lockout, but again I have not done anything more that a cursory exploration.

 

[Kilo Sierra]

@Kilo Sierra I found the batteries don't take anywhere near 40A to charge so the 20A version is adequate.

Yes, LiFEPO4 batteries are susceptible to damage when charging below freezing. In So Cal that is not a problem, so I have not looked at an in-depth solution. I have run across a couple of solutions to add a temperature sensor for low temp lockout, but again I have not done anything more that a cursory exploration.

Found a recommended Smart BMS w/ Low temp cutoff. I'm pretty sure this is what I will incorporate into my setup. Also, here is a link to Will Prowse's page of recommendations.

 

[Kilo Sierra]

Ok, so I'm starting to acquire some of the equipment I need. I found some decent battery terminals to clean up the battery wiring from KnuKoncepts, but I was wondering what Amp inline fuses you were using from the battery to the DC/DC charger, and then out from the aux battery out? Planning on going with the 20 Amp or 25Amp DC/DC charger w/ the MPPT included.

I noticed from some drawings a 60 Amp fuse, but just wanted to make sure.

 

[nworker]

Yes, I used a 60 amp fuse next to the front battery as my just in case it shorts life saver.

Have you done the build?

 

[Kilo Sierra]

Yes, I used a 60 amp fuse next to the front battery as my just in case it shorts life saver.

Have you done the build?

I'm actually a couple of inline fuse holders away from having everything ready. Am currently considering some options.

Deciding between routing of the 4 Gauge wires, between the outside and going through the firewall. Living in the northeast, I'm thinking of reducing exposure to salt and garbage. I did buy the waterproof plastic pieces that another member used on some of their projects if I have to drill through the firewall.

I bought the Fortune Batteries and the dimensions are a little different, and the BMS is a board style (with temp gauge and bluetooth) so I'm currently staring at my removed tray figuring out the best way to lay it out back there and not have any risk of shorts. I also went with a 20A dc/dc charger. I also picked up some distribution BUS bars to make things easier as I add the fuse box, compressor, etc. as the build progresses.

At the same time I'm waiting on a RR 270A alternator to arrive as that will be my next project after this, as well as a cargo box and installing Timbren Bumpstops.

 

[Kilo Sierra]

Almost finished. Mockup and testing.

 

[nworker]

Almost finished. Mockup and testing. View attachment 128748

How did it go? It looks great so far.

 

[eighty]

I was under the impression that LiFePO4 cells didn’t like to be on their flat side

Thundersky Cell Orientation | V is for Voltage electric vehicle forum

visforvoltage.org

Have you experienced any performance degradation?


Sent from my iPhone using Tapatalk

 

[Kilo Sierra]

How did it go? It looks great so far.

Great! Just came back from Vermont Overland where I used the system for four days. I have 2 12v Outlets and 3 dual USB outlets tied into a Blue Sea fuse box, as well as my Viair compressor wired directly to it. Eventually will get a fridge setup. Currently researching and planning a solar charging system for it.

I did drill some more holes into the tray for more airflow. Other than a few wires coming loose at the outlets due to all the offroading, the system worked flawlessly.

Note: This was before I zip tied down all of the cables.

 

[nworker]

I was under the impression that LiFePO4 cells didn’t like to be on their flat side

Thundersky Cell Orientation | V is for Voltage electric vehicle forum

visforvoltage.org

Have you experienced any performance degradation?


Sent from my iPhone using Tapatalk

No noticeable performance degradation. Just go back from a 10 day over landing trip in Northern California being chased by lightning induced wildfires. The setup performed flawlessly.

 

[chazz]

HUGE thanks to @nworker for inspiration and research on this. I just wired in a similar setup. The main difference in my install is that I’m not looking for a a second battery or even a backup for winching. I just need a house battery that charges from the solar on my rooftop tent and/or the alternator. This is to power my fridge (a Dometic CFX3 75DZ). So I did not need to route a huge pair of Cu wires to the front. I just ran one #6 alternator line which I brought up under the rear seats rather than directly into the storage tray. Much easier to seal with a 9/16 hole and a grommet plus some 3M 5200 quick dry. See picture below. Even with all the electrical hardware in there, I still have just enough room for most of my recovery gear.

Also, the Victron stuff costs a bit more but it is really slick. Nice app/ interface.

Here is a vid of the solar.

Letting the fridge run all night put the battery at about 95% of full in the morning but it charges up quickly once the sun comes up.


Here’s the alternator wire coming through the floor pan under the rear seat (passenger side). This is super flexible multi strand in silicone insulation.

I used 1-3/8” grommets to get the wires into the tray. One is the single #6 alternator wire. The other is the #10 circuit powering my cooler
.

You can see the MPPT solar controller at left and the alternator controller at right. The batteries and battery controller is at center. The battery pack is held in place with aluminum angle on 3 sides bolted thru the plastic tray. The wood block keeps it from moving fore and aft.

Victron energy DC-DC (alternator) Bluetooth charge controller.

Victron energy MPPT Solar Bluetooth charge controller.

Lynx LiFePo4 100 amp hour prismatic battery with included Daly Bluetooth battery management system (BMS).

 

[nworker]

I like the grommets. Nice looking installation.

I love the Daly BMS with Bluetooth, which provides great information regarding the health of the batteries.

@chazz What was your total cost of the setup?

 

[chazz]

@nworker,
As you can see from the video, I have neglected putting a new roof on my detached garage. I don’t know that the cost of the solar, batteries, wiring and control hardware would’ve paid for that new roof but it might have come close. The solar installation was quite expensive due some some custom fabricated parts, a lot of 80/20 and copious amounts of stainless steel hardware from McMaster. There were also many trips to the a local marine chandlery (one advantage of living in a beach town). All in, including some mistakes and course-corrections it was probably around $2100.

It’s funny but when I bought our dual zone multi voltage fridge/freezer, I thought that would be the bulk of the expense. It did not turn out that way. Getting a fridge is really just the beginning.

 

[JosephKC2]

I owe @nworker a shout too. It took me almost two years to get up the learning curve, but I finally got there. Installed my LiFePo4 aux setup last month.

Made a few changes to the design.

Used a common negative (chassis ground) for everything. Got the idea from the wiring diagram for the Renogy 50A DC-charger/MPPT. I decided this should be the preferred method for Xterra’s after reading in another thread that our alternator current is controlled in part by a halls sensor on the battery negative. Using the chassis ground allows the vehicle CPU to see the DC-DC charger load, and adjust the alternator output. That was the intent anyway. So I have 1x 4AWG running from the battery to the rear tray. This will allow me to run the Renogy 50amp in the future if I need it.

Overkill Solar BMS with Bluetooth which is sized to run most of my DC circuits simultaneously. This BMS allowed me to use a custom charge profile, and hopefully extend battery life. It also provides a low temperature cuttoff. I used a positive bus bar in the tray area so that I would have easy access to all of the circuit breakers. There is a negative bus bar in the wheel well that is tied into the chassis ground connection that I made. 150 amp main breaker (130 amp BMS + 20 amp charger).

Other Circuits:

• 80 amp breaker for 700 watt inverter (for electric blankets)
• 60 amp breaker for the 50 amp Anderson plug (for smittybilt air compressor)
• 20 amp breaker for the cigarette lighter receptacle (powers the fridge)
• Pending 70 amp breaker for power line to front dash fuse box (more lights please).

I was planning on using a shunt to estimate battery capacity, but that is completely unnecessary with the Overkill Solar BMS. It has a shunt already, and provides an awesome amount of battery performance data. Worth every penny.

I bench tested all of my components for a couple weeks before installing. I bought these LiFePo4 cells on ebay for $275. They took two months to arrive from china. One of them is a little swollen, but I pulled 98 of 100 amp hours in a .1C capacity test using the full cell range (2.5 to 3.65v).

This is a huge step up from the Jackery 500 setup that I ran last summer. I am happy to have the extra power and the extra space. Never could have done this without the forum support. Thanks everyone!

 

[campisi]

Hey @nworker and @JosephKC2, @chazz .... anyone have thermal issues in that tight trunk space? Any need for some kind of venting?

 

[chazz]

@campisi, sorry for the delay. With this forum busted so it doesn’t give you notification of updates I just don’t check back here as often.

In answer to your question, I don’t know how I would be aware of elevated temperatures. I certainly hope not because in addition to the batteries and control hardware I have recovery gear. It’s all packed in there pretty tightly. But I have never seen any evidence of heat. I was just in there yesterday actually wiring in a new circuit.

 

[nworker]

@campisi, sorry for the delay. With this forum busted so it doesn’t give you notification of updates I just don’t check back here as often.

In answer to your question, I don’t know how I would be aware of elevated temperatures. I certainly hope not because in addition to the batteries and control hardware I have recovery gear. It’s all packed in there pretty tightly. But I have never seen any evidence of heat. I was just in there yesterday actually wiring in a new circuit.

Yup my compartment has remained cool throughout.

 

[Tonkatoy]

This thread is full of great information, thanks to those who took the time to show and explain their projects. I am wanting to put a battery system in the rear storage area like many of you have, the purpose would be to run a fridge, maybe some camp lights and run a charging station for camera/drone/dewalt batteries. The main use for the vehicle is trips to take train pictures in hard to get to spots, but I will be moving alot, so there will be plenty of oportunity to charge the system via the alternator, mostly I just need it for overnight stays. Does anybody have a recommendation on amp hours? I was thinking about two 23 amp hour batteries from Dakota, that seems like it would be enough juice for overnight. Thanks