Target carrier (3 Viewers)

[RUSH55]

Put your batteries in the center of the truck and all your wire runs are shorter

Actually considering doing this - perfect place to put a battery box under the back seat.
But anyways... very interested in what you come up with here Mack. BTW, were you thinking about using a solar panel at all while the engine is not running?

 

[GLTHFJ60]

I've been talking to Jim a bunch, so that's what I'm doing. Hopefully by the end of the week I'll be able to finish it up and do a write-up in my thread.

Jim is the man. IMHO he's a pioneer in lithium power banks in off road trucks.

 

[J Mack]

perfect place to put a battery box under the back seat.
But anyways... very interested in what you come up with here Mack. BTW, were you thinking about using a solar panel at all while the engine is not running?

LiFePO4 batteries the way I’m buying them are almost perfect for mounting them in available spaces in the cab of a 55 or a 60 in Johnny’s case, you need 4 cells (Nominal Voltage: 3.2v per cell) and can configure them to lay flat @ about 1.5” tall if you were mounting them under a seat.

This is the specifications for the 100ah cell that Johnny used:
Minimum Capacity: 100ah
Nominal Voltage: 3.2v per cell
End-of-charge Voltage: 3.65v per cell
End-of-discharge Voltage: 2.2v per cell
Max Continuous Discharge current: 200A (2C)
Max Discharge Surge: 500A under 5 seconds
Standard Charge current: 50A (0.5C)
Max Charge current surge: 100A (1C) under 10 seconds
Charging Temperature: 0 to 50℃
Discharging Temperature: -10 to 50℃

Dimensions: Height 11.5″, Width 5.25″, Thickness 1.5″
Weight: 5.85lb per cell



So as you can see a small lightweight battery with a true 100ah capacity that easily tucks into an available space is going to be about perfect for a second battery in a camping rig.

Solar would also be cool if you plan on base camping for a day or two at a time with your rig, like I keep saying about our hobby there really isn’t a wrong answer if we are all out here in our garage having fun building our vision of the perfect pig.

 

[fj55-100]

amen

like I keep saying about our hobby there really isn’t a wrong answer if we are all out here in our garage having fun building our vision of the perfect pig.

 

[J Mack]

So as you can see a small lightweight battery with a true 100ah capacity that easily tucks into an available space is going to be about perfect for a second battery in a camping rig.

I know I’ve posted about this before but no one has time to back through this debacle of a build thread so I’ll post this again for context to the above comment.

Lead chemistry batteries like the current AGM that we all use are derated about 50% for their “usable” amp hour rating, LiFePO4 batteries have closer to 100% usable amp hour rating. These aren’t exact numbers but close enough for this conversation and planning usable amp hour for your camping needs.

A popular battery for a second battery in a camping rig is the Group 31 AGM 12 volt boat and RV battery, the specs for that battery, Weight: 75 lbs, Length: 12.91 in, Width: 6.77 in, Height: 9.25 in and it has an advertised amp hour rating of 100 amp hour. It would take two of those batteries to get “true” 100 amp hour and that package size configured in its smallest size would be 13” X 13” 9.25” and weigh 150LBS. The LiFePO4 batteries like Johnny is using configured in their largest configuration would be 11.5” X 5.25” X 6” and weigh 24LBS.

Link to battery I quoted: Group 31 AGM 12 volt dual purpose boat and RV battery - SLI31AGMDPM at Batteries Plus Bulbs



And: Affordable Electric Vehicle Batteries & Components from Electric Car Parts Company

 

[J Mack]

For @GLTHFJ60 to help answer a question he asked me about storage.





Lithium-based

There is virtually no self-discharge below about 4.0V at 20C (68F); storing at 3.7V yields amazing longevity for most Li-ion systems. Finding the exact 40–50 percent SoC level to store Li-ion is not that important. At 40 percent charge, most Li-ion has an OCV of 3.82V/cell at room temperature. To get the correct reading after a charge or discharge, rest the battery for 90 minutes before taking the reading. If this is not practical, overshoot the discharge voltage by 50mV or go 50mV higher on charge. This means discharging to 3.77V/cell or charging to 3.87V/cell at a C-rate of 1C or less. The rubber band effect will settle the voltage at roughly 3.82V. Figure 1 shows the typical discharge voltage of a Li-ion battery.

Figure 1: Discharge voltage as a function of state-of-charge. Battery SoC is reflected in OCV. Lithium manganese oxide reads 3.82V at 40% SoC (25°C), and about 3.70V at 30% (shipping requirement). Temperature and previous charge and discharge activities affect the reading. Allow the battery to rest for 90 minutes before taking the reading.



Li-ion cannot dip below 2V/cell for any length of time. Copper shunts form inside the cells that can lead to elevated self-discharge or a partial electrical short. (See BU-802b: Elevated Self-discharge.) If recharged, the cells might become unstable, causing excessive heat or showing other anomalies. Li-ion batteries that have been under stress may function normally but are more sensitive to mechanical abuse. Liability for incorrect handling should go to the user and not the battery manufacturer.



More of the same info here: Storage voltage for LiFePo4 cell? - Endless Sphere

 

[GLTHFJ60]

Here is some good reading as well:

How to charge Lithium Iron Phosphate lithium ion battery packs including packs with high current and High Capacity.

High capacity LiFePO4, Lithium Iron Phosphate batteries.

www.powerstream.com

The root of what I was getting at via email is; what level of charge will you be able to achieve with a normal 12v alternator that charges at ~14.2v. Rough math says somewhere between 95-100%, but if that's the case, why do lifepo4 chargers charge at 14.6v? Just thinking out loud. Time to hit the books.

 

[J Mack]

The root of what I was getting at via email

I get it I just don't know if it's a big deal the way we are using them.



From the link you posted above.

" Commentary: It looks like the magic number is around 3.3 volts. Below that you don't have significant charging, above that you do. A lithium iron phosphate battery doesn't care if it is never fully charged, so if all you have available is 3.3 volts and you don't mind the loss in capacity you could use the 3.3 volts. This opens up new possibility for a simple but very long life backup battery in 3.3 volt systems. "

Guys are taking Battle Born batteries and direct replacing their lead based batteries with no concern to charging other than if the alternator is up to the job with the added capacity. We are basically deconstructing the Battle Born batteries to individual components and reconstructing them to fit in our confined spaces to better suit our needs. I could be wrong here but anything in the range of acceptable charge voltage is going to net you at or near full capacity like 98 to 99% and unless you are doing something very specific like preforming a capacity test the “full charge” value is just a max number not necessarily a value that’s needed to achieve the desired results from the battery as we are likely to use it powering a refrigerator or something similar.

I understand we are guys and numbers mean something when we are talking about this stuff and I also enjoy having these conversations as it’s how most of my learning is done so if you find something that contradicts my thinking please post it here so we can all learn this together.

 

[DTC72]

So....go with the smaller, lighter, and more efficient Lithium batteries for the camping rig setups. Got it.

 

[bobm]

And will they also be used to start the vehicle and power winches and lights also???

 

[GLTHFJ60]

I get it I just don't know if it's a big deal the way we are using them.



From the link you posted above.

" Commentary: It looks like the magic number is around 3.3 volts. Below that you don't have significant charging, above that you do. A lithium iron phosphate battery doesn't care if it is never fully charged, so if all you have available is 3.3 volts and you don't mind the loss in capacity you could use the 3.3 volts. This opens up new possibility for a simple but very long life backup battery in 3.3 volt systems. "

Guys are taking Battle Born batteries and direct replacing their lead based batteries with no concern to charging other than if the alternator is up to the job with the added capacity. We are basically deconstructing the Battle Born batteries to individual components and reconstructing them to fit in our confined spaces to better suit our needs. I could be wrong here but anything in the range of acceptable charge voltage is going to net you at or near full capacity like 98 to 99% and unless you are doing something very specific like preforming a capacity test the “full charge” value is just a max number not necessarily a value that’s needed to achieve the desired results from the battery as we are likely to use it powering a refrigerator or something similar.

I understand we are guys and numbers mean something when we are talking about this stuff and I also enjoy having these conversations as it’s how most of my learning is done so if you find something that contradicts my thinking please post it here so we can all learn this together.

Battle-born will also (in some models) put more than the advertised capacity within the case. They may put 120ah in a 100ah battery to make sure that the user has 100ah usable off of a 12v system.



For me it's more of a thought experiment to see what the limits of this system are, having never delved into this realm before. I've got my lithium battery array charging now off of a 5a charger I have at the house, and I've been able to charge back in 10ah of capacity in about 2 hours. Pretty neat

 

[GLTHFJ60]

And will they also be used to start the vehicle and power winches and lights also???

You can set it up that way, yes, it's just more expensive to get components that can output the amperage required for winches. Lights, regular ACC loads, vehicle harness, no problem from a 100ah type setup like Jim and I have.

 

[J Mack]

And will they also be used to start the vehicle and power winches and lights also???

First thing to remember here Bob “I’m a janitor” I get paid to clean up other people’s messes not design battery systems so take all of my opinions with a grain of salt.



My ideal system would keep the “start” battery in the factory location and let it continue in its role as the “start” battery and add a LiFePO4 battery second battery to run everything else, these two batteries can be combined with something like the power gate battery isolator like Scraps and I use if needed when one runs too low to do what you need. This would not only be easier offering more mounting options but offer 4X the capacity (the only reason to add a second battery in the first place) at ¼ the weight of our standard Pig sized batteries. (About 30 usable amp hour)

Battle-born will also (in some models) put more than the advertised capacity within the case. They may put 120ah in a 100ah battery to make sure that the user has 100ah usable off of a 12v system.

It’s my understanding most of the LiFePO4 batteries “lithium” over promise on capacities when new and start to level into advertised capacities as they age.

 

[J Mack]

Refrigerator finally showed up so I can start some real world testing on the battery.
Just over 4 AMPs with the ice maker on and just under 4 AMPs with the ice maker off.
Pump runs for a minute or two then shuts off for 5 to 8 minutes, plan to let it run for 12 hours and check it tomorrow.

 

[Ol Yeller]

Not anywhere near doing any of this but great tech from you guys!

Any concerns over “thermal events”??

I know an RC guy who had his house burn down...

 

[RUSH55]

 

[J Mack]

Not anywhere near doing any of this but great tech from you guys!

Any concerns over “thermal events”??

I know an RC guy who had his house burn down...

Nothing is impossible so I’m reluctant to say no I’m not concerned but we are running good battery management systems that will prevent “most” of the scenarios that you hear about when you hear about lithium batteries catching on fire so my concerns are more focused around having something in the cab of my pig that has the potential to short out and dump hundreds of AMP’s like any battery of any chemistry.

The RC batteries themselves don’t typically have a built-in BMS and rely on common sense to prevent fires so it’s not all that uncommon to hear about more issues over there then in the RV camping world.

 

[Megadoomer]

RC batteries are moved around a lot more and could be dropped. This could cause the plates inside to touch and kablamy. I'd say a system is going to be in one spot most of the time and be just fine.

 

[GLTHFJ60]

Not anywhere near doing any of this but great tech from you guys!

Any concerns over “thermal events”??

I know an RC guy who had his house burn down...

Lots of amperage protection, and multiple fire extinguishers. Nothing is impossible, but these systems appear to be pretty safe with the BMS that exist today.

Also, LiFePO4 is a much safer battery chemistry than lithium-ion, the latter of which is used in RC batteries, phones, etc. We're using LiFePO4 here.

 

[J Mack]

After 12 hours of running the refrigerator with the ice maker on running on the 60Ah battery pack it went down from 72% to 41% remaining capacity. I think this is acceptable for a stand by battery backup for when the pig isn’t running. The refrigerator temp was at 86° when I started and I ran this test with it empty, set temperature was 32°.

We usually drive around for five+ hours exploring on our adventures and I think all of my batteries should get fully charged in this time, I’ll do one more test starting with a full refrigerator that is already down at the set temperature but I believe I’m good to go with this setup.