kshopper2084
New Member
- Joined
- Nov 21, 2021
- Messages
- 34
Hi all. I've finally gotten a chance to test/use my new LiFePO4 280Ah battery with the JDB 200A BMS in my motorcoach.
Over a 2 week trip we used the battery extensively and charged via the Renogy 60A DC-DC charger while driving, and also using the legacy house Freedom 20 inverter/charger.
The Freedom 20 doesn't have a Lithium charging mode (it's 25 years old!) but it does allow you set a few different charge profiles for warm/cold FLA, GEL, etc. batteries.
So everything worked out really well on the trip, however, I did notice that when charging using the Freedom 20 I was seeing some scary high temperature readings from the BMS mounted temp sensor. During one charge session the BMS shutdown due to overtemp.
I was using the following charge profile on the Freedom 20 during these events: Bulk=14.3v, Float=13.4v.
The Freedom 20 will happily charge at up to 100A.
Here are some shots at the cutoff time, and then 1 hr later when the BMS temp dropped to match the rest of the cells.
Any thoughts on why the BMS temps would be so much higher than the cells in this scenario?
I then changed the Freedom 20 charge profile to use lower voltages: Bulk=13.9v, Float=13.3v.
Charging using this profile did not result in the extremely high BMS temperatures, and the charge cycle ended slightly before completely charging the battery:
Also, when charging using the DC-DC 60A charger no high temps have been seen.
I am fine with using this charge profile but am curious as to why the BMS would overtemp like that?
Finally, I have one temp. sensor on the cells that will sometimes go to "off chart low" aka -255c while charging is in progress. This doesn't seem to cause any actual problems, and the other sensors remain accurate, but I have my notifications setup such that I see when the temps drop below zero and so I am flooded with notifications when this happens. Seems sporadic. Has anyone else seen this type of sensor problem?
Over a 2 week trip we used the battery extensively and charged via the Renogy 60A DC-DC charger while driving, and also using the legacy house Freedom 20 inverter/charger.
The Freedom 20 doesn't have a Lithium charging mode (it's 25 years old!) but it does allow you set a few different charge profiles for warm/cold FLA, GEL, etc. batteries.
So everything worked out really well on the trip, however, I did notice that when charging using the Freedom 20 I was seeing some scary high temperature readings from the BMS mounted temp sensor. During one charge session the BMS shutdown due to overtemp.
I was using the following charge profile on the Freedom 20 during these events: Bulk=14.3v, Float=13.4v.
The Freedom 20 will happily charge at up to 100A.
Here are some shots at the cutoff time, and then 1 hr later when the BMS temp dropped to match the rest of the cells.
Any thoughts on why the BMS temps would be so much higher than the cells in this scenario?
I then changed the Freedom 20 charge profile to use lower voltages: Bulk=13.9v, Float=13.3v.
Charging using this profile did not result in the extremely high BMS temperatures, and the charge cycle ended slightly before completely charging the battery:
Also, when charging using the DC-DC 60A charger no high temps have been seen.
I am fine with using this charge profile but am curious as to why the BMS would overtemp like that?
Finally, I have one temp. sensor on the cells that will sometimes go to "off chart low" aka -255c while charging is in progress. This doesn't seem to cause any actual problems, and the other sensors remain accurate, but I have my notifications setup such that I see when the temps drop below zero and so I am flooded with notifications when this happens. Seems sporadic. Has anyone else seen this type of sensor problem?
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