Lithium Battery? (1 Viewer)

[TheLCProject]

My LC200 has a underhood LFP (Renogy 100AHr. RBT100LFP12SH-US) with heater to allow charging below 32 deg's and I use a RedArc BCDC as the charger, but thats not because of concern about my alternator compatibility, but rather the issue of two batteries that are not equivalent.

If your BCDC is below 32F on the Li profile it won't charge your heated Li battery.

 

[KJun]

Your Valence XP does not have a BMS so you should not expect any protection that a BMS would provide such as low/high voltage cutoff, low temp charge cutoff, cell temp monitoring, etc.

Yes I know and so far have had zero issues to date and now going on year five. I did think that it had a discharge cutoff at 10V no? My fridge has a low voltage cutoff which doesn't hurt. Though as I get older I know I'm bound to forget to turn off an accessory light somewhere by mistake again.

 

[KJun]

There are tons of good threads on LFP at diysolarforum.com. There's a whole thread on why you shouldn't charge below 0F. Why you cannot charge LiFePO4 below 0 degrees Celsius - https://diysolarforum.com/threads/why-you-cannot-charge-lifepo4-below-0-degrees-celsius.2912/. That's not to say you can't do it, just that it will permanently harm the battery. (Note that it's cell temp, not ambient temp, so it's possible your cells can be a bit warmer than the air temp and still be "above 0C"

Now if your battery has a BMS (and many do have a cheap internal one) it should prevent you from doing really bad things like discharging or charging outside the cell temp range or over/under charging the cell voltages.

The Valence specs clearly state charging temp is 0C to 45 C and discharge is -10C to 50C. The chemistry of LFP batteries is all essentially the same. LFP is LFP is LFP. If you're using it to start when it's 0F out you're harming the battery. On top of that if you're not charging at 14V+ then you're never getting a full charge.

I don't know why you'd pay 3-4x the cost for a LFP battery to then abuse it and end up with a battery life that is equal to or less than a cheap FLA but do whatever you want I suppose.

Specs from Valence U27-12XP Lithium Ion Battery Module | Greentec Auto - https://www.greentecauto.com/hybrid-battery/repurposed-batteries/valence

Voltage (nominal) 12.8 V
Capacity @ C/5, 25 °C (typical) 138 Ah (New)
Energy 1.76 kWh (New)
Discharge Cont./Peak (30 sec) 150 A / 300 A
Discharge Cutoff Voltage 10 V
Recommended Charge Voltage 14.6 V
Charge Float Voltage Range 13.8 - 14.6 V
Recommended Charge CCCV ≤ 72 A to 14.6 V
Discharge Temperature -10 °C to 50 °C
Charge Temperature 0 °C to 45 °C
Self Discharge @ 25 °C < 2% per month
Terminal Hardware M8 x 1.25
Terminal Torque 25 Nm 222 in-lbs
Plastic Case Flame Retardant
IP Rating IP56

Features
• >4000 cycles at 80% DOD
• Create systems 12 - 1000 V
• Series and/or parallel operation
• Automatic cell monitoring & balancing
• Temperature monitoring of cells
• Rugged mechanical design
• Thread locking feature
• Footprint of Group 27 lead acid case
• Maintenance-free
• No hydrogen generation or gassing

Height: (excluding bolts) 225 mm 8.86”
Width: 172 mm 6.77”
Length: 306 mm 12.0”
Weight: 19.2 ± 0.1 kg 42.2 lbs
Cell Configuration: 4IFpR27/66-44

Yup familiar with all the dire warnings on permanently damage to the battery if charged at freezing temperatures. Again it's an experiment to put all of these claims to the test empirically. And given what I paid for it it's already returned years of problem free and reliable service (relative to my experience with LA/AGMs) and it could crap out and die tomorrow and I would swap another one in (have a few lying around for solar generator and off grid applications). Currently no signs of it slowing down yet though at some point I may pull it and run another capacity test (lucked out and got a lot with 90%+ of original stated capacity) to see how far its degraded. I see no reason why it wouldn't be serviceable even if it was in the 80% range or even lower given the performance characteristics of LiFePO4 batteries that I'm sure you're well aware of. I do wonder though what the temperature of the engine bay is after it warms up a bit and how it might affect the battery temperature.

 

[linuxgod]

Yup familiar with all the dire warnings on permanently damage to the battery if charged at freezing temperatures. Again it's an experiment to put all of these claims to the test empirically. And given what I paid for it it's already returned years of problem free and reliable service (relative to my experience with LA/AGMs) and it could crap out and die tomorrow and I would swap another one in (have a few lying around for solar generator and off grid applications). Currently no signs of it slowing down yet though at some point I may pull it and run another capacity test (lucked out and got a lot with 90%+ of original stated capacity) to see how far its degraded. I see no reason why it wouldn't be serviceable even if it was in the 80% range or even lower given the performance characteristics of LiFePO4 batteries that I'm sure you're well aware of. I do wonder though what the temperature of the engine bay is after it warms up a bit and how it might affect the battery temperature.

Once the engine (radiator, really) warms up it's probably ok. There are chemistries which are much better suited for cold though. Adding manganese or something to the LFP battery changes the chemistry and will let the batteries charge and discharge below freezing. Normal Lithium-ion as well tends to do better than LFP.

I spent a ton of time reading the diysolarforum.com before (and after) I built my pack. Real world experience will most likely show you're able to exceed manufacturer ranges to an extent, though most likely with some sort of trade-off like long term cycle count. It's entirely possible that a huge draw on the battery for 2 seconds at -20F causes much less damage than a light draw for 30 minutes at -10F as well. I've seen a lot of swollen, leaking, and otherwise damaged LFP batteries from abuse though.

 

[KJun]

Once the engine (radiator, really) warms up it's probably ok. There are chemistries which are much better suited for cold though. Adding manganese or something to the LFP battery changes the chemistry and will let the batteries charge and discharge below freezing. Normal Lithium-ion as well tends to do better than LFP.

I spent a ton of time reading the diysolarforum.com before (and after) I built my pack. Real world experience will most likely show you're able to exceed manufacturer ranges to an extent, though most likely with some sort of trade-off like long term cycle count. It's entirely possible that a huge draw on the battery for 2 seconds at -20F causes much less damage than a light draw for 30 minutes at -10F as well. I've seen a lot of swollen, leaking, and otherwise damaged LFP batteries from abuse though.

Good info and generally agree that there are many variables in play that could contribute to the longevity vs utility considerations of a LiFePO4 battery. I'm just one data point on what I'm observing out of a a battery under the hood of a 200 series in real world driving conditions. Btw I'm adding a BCDC and second battery that will go in the back of the rig that would provide added redundancy should it ever be needed.

 

[linuxgod]

Good info and generally agree that there are many variables in play that could contribute to the longevity vs utility considerations of a LiFePO4 battery. I'm just one data point on what I'm observing out of a a battery under the hood of a 200 series in real world driving conditions. Btw I'm adding a BCDC and second battery that will go in the back of the rig that would provide added redundancy should it ever be needed.

Be careful with charging btw. If you run the battery way down and rely on the alternator to fully recharge I’ve seen numerous alternators burned out in RVs after 15-20 minutes of run time because LFP has extremely low internal resistance and the alternator will run full tilt

 

[Lester did that]

The main advantages I see with lithium is the super fast re-charging (I think a deep cell take 6 to 8 hours to charge back up) plus they run constant voltage as they drain which keeps the fridge running.

Yes and weight