Lead Acid to LiFePO4 Swap

[Schmalzy]

I'm completely new to this, and my only knowledge comes from watching Will's YouTube Channel.

I have a small teardrop camper with a small 12v system. It currently has a lead-acid battery, and I'm looking to upgrade to a LiFePO4 12v battery.

I was just diagnosed with sleep apnea, and will need to get a CPAP machine... I know I should probably do an energy audit before I get a new battery, but my questions\concerns below are not specific to the battery capacity at this point, more about the concerns and feasibility of upgrading the battery to LiFePO4.

Current Setup:

• Zamp OBSIDIAN® SERIES 90 Watt Panel
• Zamp 15 Amp 5-Stage PWM Charge Controller
• NOCO Genius 10 charger (for shore power)
• Generic Lead-Acid Battery
• Fuse Box

Current loads:

• Overhead LED lighting
• Autobrake Controller
• 12v cigarette outlet and USB ports

Concerns\Questions:

• Vibrations\Security: The base of the existing battery-box is screwed into the truck-bed-box, and the cover of the box is then strapped down to the base. Are there similar types of battery-boxes that exist for LiFePO4 batteries? Or am I better off getting rid of the box and securing some strap loops to the truck-bed-box and strapping it down that way?
• Cold Temps: I do take the camper out in late-fall when temps can fall below freezing overnight. I'm going to make sure that I get a quality battery with low-temp sensor\cutoff. But I'm wondering if the "heated" type of battery would make a difference in this situation?
• Water\Moisture: Although the truck-bed-box is supposed to be waterproof, I know its very possible that water could get in the box and onto the battery. This was making me consider the Plastic\Marine cased type battery.
• Compatibility: As far as I can tell, both the NOCO charger and the Zamp controller have modes for Li batteries, so I don't believe this will be an issue.
• Any other "Gotchas" I'm not thinking of?

Considering one of these two option, the choice would come down to choosing Marine\Plastic case vs Heated models (I wish there was an option with both features):

• SOK Battery | 206Ah 12v | LiFePO4 Battery (Plastic\Marine Case Option)
• SOK Battery | 206Ah “H” 12v | Heated & Bluetooth

Thank you!

 

[sunshine_eggo]

• Vibrations\Security: The base of the existing battery-box is screwed into the truck-bed-box, and the cover of the box is then strapped down to the base. Are there similar types of battery-boxes that exist for LiFePO4 batteries? Or am I better off getting rid of the box and securing some strap loops to the truck-bed-box and strapping it down that way?

Some sort of cushion is advisable.

• Cold Temps: I do take the camper out in late-fall when temps can fall below freezing overnight. I'm going to make sure that I get a quality battery with low-temp sensor\cutoff. But I'm wondering if the "heated" type of battery would make a difference in this situation?

Storage/discharge in cold temps is a non-issue. CHARGING below freezing is deadly. Most batteries protect themselves by refusing to charge or for a little more $, have heaters that route incoming charge current to heat the battery.

• Water\Moisture: Although the truck-bed-box is supposed to be waterproof, I know its very possible that water could get in the box and onto the battery. This was making me consider the Plastic\Marine cased type battery.

Drain holes.

• Compatibility: As far as I can tell, both the NOCO charger and the Zamp controller have modes for Li batteries, so I don't believe this will be an issue.

If those chargers can be set to 14.2-14.6V absorption and < 13.6V float (13.8V is acceptable in a pinch), they're fine.

• Any other "Gotchas" I'm not thinking of?

Cost.

Primary benefits of LFP in your situation are:
1) increased cycle life
2) lighter weight
3) smaller volume

Unless you're regularly cycling the battery (daily), you're losing out on #1, and you're paying a premium for #2 and #3. If you're fine with that, it's a non-issue.

 

[Schmalzy]

Some sort of cushion is advisable.



Storage/discharge in cold temps is a non-issue. CHARGING below freezing is deadly. Most batteries protect themselves by refusing to charge or for a little more $, have heaters that route incoming charge current to heat the battery.



Drain holes.



If those chargers can be set to 14.2-14.6V absorption and < 13.6V float (13.8V is acceptable in a pinch), they're fine.



Cost.

Primary benefits of LFP in your situation are:
1) increased cycle life
2) lighter weight
3) smaller volume

Unless you're regularly cycling the battery (daily), you're losing out on #1, and you're paying a premium for #2 and #3. If you're fine with that, it's a non-issue.

Thank you!

 

[Schmalzy]

Primary benefits of LFP in your situation are:
1) increased cycle life
2) lighter weight
3) smaller volume

Unless you're regularly cycling the battery (daily), you're losing out on #1, and you're paying a premium for #2 and #3. If you're fine with that, it's a non-issue.

Weight is an important factor for me. I don't want to add more weight to the truck-bed-box, as this effects the tongue weight of the trailer.

What about depth of discharge? My goal is to add more capacity without adding weight. I assumed I was only getting maybe ~30Ah (~50%) useable power from the lead-acid battery. Is it realistic to expect to get the full useable capacity from LiFePO4?

 

[sunshine_eggo]

Weight is an important factor for me. I don't want to add more weight to the truck-bed-box, as this effects the tongue weight of the trailer.

What about depth of discharge? My goal is to add more capacity without adding weight. I assumed I was only getting maybe ~30Ah (~50%) useable power from the lead-acid battery. Is it realistic to expect to get the full useable capacity from LiFePO4?

Depends on the manufacturer. Many rate discharge to 20% SoC (80% rated capacity). Even if you do go to 0%, cycle life should be improved over AGM.

 

[Geokilroy]

As far as going LiFePo4 it's a great Idea. I DIY'ed my 12v 280ah battery (200 amp BMS w/bluetooth) for about $800 from Amy @ Docan. About 225ah useable (80%). It arrived in less than 2 weeks from the Texas warehouse and I built in a few days. Only about 60 pounds. That's about the weight of one lead type 90-100ah battery. Mine has been working great for about 6 months so far. With that many available ah you can add a heater for about $50. It should run your CPAP and lights for quite a while even in the cold.