LiFePO4. Is it bad to discharge all the way or to charge to 100%?

[zack sc]

My question is about an LiFePO4 battery. Is it okay to charge it to 100% (float) some of the time? Is it okay to discharge it all the way?
I have an LiTime mini 100 Ah battery (1280 Watt-hours) in my 2008 4Runner that I charge while driving using a Victron Orion 12-12 50 dc-dc converter (XS 50). Then, when I am parked, I transfer the energy from the LiTime battery into a Jackery. Typically the LiTime battery charges at about 15 amps and discharges at about 7 amps. If I don’t think about it too much, sometimes I am going to get to “Float” while driving, which I assume is 100%, and sometimes the discharge current will drop to zero while I am parked and charging the Jackery from the LIFePo4 (LiTime) battery. Are these occurrences bad for LiFePO4 battery? Is one extreme worse than the other? I can supply more details, but basically I am wondering if this is bad for the battery, or if I can continue to casually charge and discharge sometimes hitting 100% and 0%.

[John in Santa Cruz]

you ideally should set 5% or 10% as the lower discharge limit. 100% is fine.

[Mike Magee]

If you do drain the LiFePO4 completely by chance, it's helpful to recharge it at least somewhat as soon as possible.


Is there no way to recharge the Jackery directly while driving? Or are you doing that in addition to recharging the LiFePO4?

[zack sc]

Originally Posted by Mike Magee

If you do drain the LiFePO4 completely by chance, it's helpful to recharge it at least somewhat as soon as possible.


Is there no way to recharge the Jackery directly while driving? Or are you doing that in addition to recharging the LiFePO4?

Thanks Mike. I usually charge both while driving. The Jackery (Explorer 1000) will only charge at 6 amps on 12 V (about 75 Watts). The LiTime mini can charge at 20 amps or more, so I get an extra 290 Watts while driving and I am able to accumulate and store twice as much energy. LiTime mini is also much less expensive.
P.S. I am thinking about getting a larger capacity (around 200 Ah or so) and I am open to any suggestions as to what brands to consider.

[zack sc]

Originally Posted by John in Santa Cruz

you ideally should set 5% or 10% as the lower discharge limit. 100% is fine.

Thanks very much John. I will try to heed that although it is a bit tricky as I have no shunt or battery monitor. My system is minimal. After the Victron XS50 there is a circuit breaker and then a 6 AWG wire about 2 feet long going right to the battery.
Here is what I think I can do going forward though, and I would be very interested in what you think about this.
1. Charge to "Float"
2. Keep track of how the time over which I discharge the LiTime mini into the Jackery. Then use that info to avoid going to zero*. (10 hours of charging the Jackery should draw down about 800 Wh.)
(I can also keep track of any additional energy I put into the LiTime mini if I happen to drive again as there is a history function in the Victron app that tells you how much Watt hours you have added in your most recent drives.)
I think that should be doable. It is really helpful to know, as you explained, that avoiding zero is more important than avoiding "Float", cause I kinda need one or the other to keep from getting lost.

*PS. Regarding what I call zero, I don't really know what actual percentage that is. What I observe is just that the LiTime mini stops charging the Jackery. The charging rate goes to zero, and I assume that that is the LiTime BMS protecting the mini, but I really don't know what that actually corresponds to in terms of state of charge (SOC) of the LiTime mini. (I don't think LiTime has the sort of technical support where I can find out easily.) Would you call that zero state of charge? Any ideas and advice is most welcome! I appreciate your expertise.

[zack sc]

PS. I am thinking of replacing the LiTime mini with a larger capacity battery pretty soon. Maybe something in the 180 Ah to 250 Ah range. Any suggestions regarding brands and batteries are most welcome!

[John in Santa Cruz]

how big is the battery compartment in the Scamp 13 ? Guessing its sized for a Group 27M ? My preference would be for it to work like an RV should work... house battery onboard the camper, charged from the tow vehicle, and/or shore power via the DC converter, and/or solar, rather than messing with various external systems like a jackery etc... I'd use the largest LiFePO4 that would fit in the original battery compartment, maybe with minimal mods to expand. with a trailer that small I'd use a portable solar panel, like a Renogy Solar Suitcase, this worked quite well with our old Casita.

[steve67]

I recently moved to a 200Ah from a 100Ah LiFePo because the smaller battery wouldn't see us through the night using the Fantastic Fan. Using a 200-watt portable panel, I hope to charge the battery on sunny days. The battery I picked still fits inside my tongue box with the 20lb propane tank.

[John in Santa Cruz]

Originally Posted by steve67

I recently moved to a 200Ah from a 100Ah LiFePo because the smaller battery wouldn't see us through the night using the Fantastic Fan. Using a 200-watt portable panel, I hope to charge the battery on sunny days. The battery I picked still fits inside my tongue box with the 20lb propane tank.

wow, that sounds like a lot of power for the fan, like 4 amps ?? i have a MaxxFan deluxe, which has 10 speeds, I most commonly use speed 3 or 4. 3 is 0.5 amps, 4 is 0.8 amps, so even at 4 I'd get about 5 days continuously on a 100AH battery.

[steve67]

Forgot to include the fridge....(a stand-alone cooler style).

[John in Santa Cruz]

Originally Posted by steve67

Forgot to include the fridge....(a stand-alone cooler style).

I have a 6.3 cu ft DC Compressor fridge/freezer (Norcold N2175), the Maxxfan, and a propane furnace, in a 21 ft Escape... my 2 x 206AH (412AH or 5260 watt*hours total) batteries can run my whole trailer for a full week (7 days, 7 nights) with my solar panel shut off, and still have 30-40% battery capacity left. That includes lighting, fan running all day, fridge running 24/7, furnace running all night if its below 64F inside, and occasional use of a 2000W inverter (mostly, pot of coffee in the morning, wife's hair dryer after shower).

[Michael Pupeza]

Hey Guys;
Perhaps I'm misunderstanding the problem BUT:
To the best of my knowledge, ALL commercial Lithium 12V Batteries suitable for RVs, Boats, Camping, trolling motors, etc., of sizes beyond a few Ahrs have a BMS (Battery Management System) which inhibits and shuts off the power if below minimum voltage is present.
This BMS is installed inside the case and, while not perfect and does not regulate current flows, DOES protect the battery from over discharge and overcharge.
While some recent controversial studies have shown that shallow to medium discharges 'may' improve battery life, the Lead Acid Battery effects of deep discharge, or overcharge, are not there.
That being said, it is still a good idea to monitor for low voltage as you don't want your fridge to be shut off for too long. PHEW!
I wouldn't worry too much though!
Mike .....>