watt cycle batteries

[m.muddk]

is it normal for a new LiFePO4 battery voltage to drop(13.8 to 12.4 v) when a 50% load is applied and pop back up when removed
wattcycle 100ah LiFePO4

 

[Texas-Mark]

Where are you measuring the voltage? At the battery terminals or the load?

 

[m.muddk]

batt terminals

 

[Omkar]

There is a youtube video where a person tests the Wattcycle battery, and observed the same issue. So, are you able to fully charge the battery up to 14.6? or does the charge terminate at a lower voltage? Do you have a way to monitor charge voltage and current? You may have one cell with a lower voltage than the other 3. Meaning the battery is "out of balance".

 

[Texas-Mark]

Do you know the exact current draw and what the BMS is actually rated for? Some of the cheaper BMSs use small gauge wire, and I can see there being a voltage drop (between cells and the battery terminals) under a high load.

 

[RCinFLA]

50 amp load on 100 AH battery, I would expect about 100 mV slump at cell's terminals after 1 to 3 minutes of load.

X4 for four cells = 0.4 v.

Guess on BMS Rs about 1 mohm, x 50A for 0.05v drop.

Misc wiring and internal connections about 2 mohms for 0.1v drop.

Total about 0.6v slump at 12v LFP terminals at 25 degs C.

This assumes 25 degs C. Cold temp is much greater.

1.4v drop (if around 25 degs C) is way too much. Would be within range if battery near 0 degs C.

 

[m.muddk]

There is a youtube video where a person tests the Wattcycle battery, and observed the same issue. So, are you able to fully charge the battery up to 14.6? or does the charge terminate at a lower voltage? Do you have a way to monitor charge voltage and current? You may have one cell with a lower voltage than the other 3. Meaning the battery is "out of balance".

have not been able to charge to 100 % yet but what im seeing so far is it needs balancing i did purchase a bench supply to work on balancing

 

[m.muddk]

Do you know the exact current draw and what the BMS is actually rated for? Some of the cheaper BMSs use small gauge wire, and I can see there being a voltage drop (between cells and the battery terminals) under a high load.

book says 100amp is max continues discharge

 

[Texas-Mark]

Guess on BMS Rs about 1 mohm, x 50A for 0.05v drop.

Misc wiring and internal connections about 2 mohms for 0.1v drop.

No way to know for sure about those without opening the battery.

 

[Omkar]

have not been able to charge to 100 % yet but what im seeing so far is it needs balancing i did purchase a bench supply to work on balancing

Which supply did you purchase?

 

[m.muddk]

watched a video of will opening one and checking the quality of the build
this is one reason i purchased
purchased a cheap 0-30v 0-10 amp dc bench supply

 

[Omkar]

watched a video of will opening one and checking the quality of the build
this is one reason i purchased
purchased a cheap 0-30v 0-10 amp dc bench supply

Would you mind post a link to it? Thanks.

 

[m.muddk]

 

[Omkar]

I was referring to the bench supply you purchased... Thanks again.

 

[m.muddk]

power supply

Amazon.com

 

[Omkar]

power supply

Amazon.com

Thank you!

 

[Wiley]

Excuse the off the wall question: If one were to replace the BMS in this battery (say for example, it became fried) which BMS would the experts on the forum suggest would be a suitable replacement?
Many thanks in advance, Wiley

 

[Impatient]

Excuse the off the wall question: If one were to replace the BMS in this battery (say for example, it became fried) which BMS would the experts on the forum suggest would be a suitable replacement?
Many thanks in advance, Wiley

Yeah. One side of me REALLY wants the IP67 TM version with 120A BMS for a 2P setup, but wondering if I should opt for 2x or 3x IP65 mini’s whose tops can be removed with screws…for BMS replacement.

These will go on underside of camper van, exposed to grunge, occasional splash, with temp extremes (near muffler, but subject to overnight freezing.

This would be to replace 186Ah AGMs (2x 93…though somewhat tired). Yeah yeah yeah, I’ve heard the LiFePO marketing schpiel, and buy into most, but these 8yr old AGM’s are still hanging in there…albeit they don’t last as long (>12v) per charge as they used to. Never dreamed of microwave before, now trying to decide which setup would better support Inverter & Microwave.