FireFly Battery Notes II

[sailorboy1]

Please try to not drift too much here into a standard battery/electrical topic. All that happens is your general question gets lost to input from those not reading a thread about Fire Fly batteries, while at same time turning off the readers who came for the topic of Fire Fly batteries

[crayiii]

This might help with the voltage to SOC comparison.

[MerMike]

Originally Posted by crayiii

This might help with the voltage to SOC comparison.

Can you post the link to the source? Thanks.

[crayiii]

Originally Posted by MerMike

Can you post the link to the source? Thanks.

https://forums.sailboatowners.com/th...system.196179/

[rgleason]

I can't read that attachment, but I found the original document from Firefly

Test report ETL 16-Voltage vs SOC G31 Voltage vs SOC% the answer seems to be 12.02 or 12.01 at 40% SOC using C3 or C10. What is C3 3x the battery capacity or .3?

We would not be worryiing about this if they were LFP.


Not the link but related testing
https://coastalclimatecontrol.com/in...g-reveals.html
https://panbo.com/gizmos-new-firefly...t-the-details/


DoD What's the Latest on Firefly Oasis Batteries? - Gear Anarchy - Sailing Anarchy Forums
DOD 60% = 2350 cycles.

[MerMike]

Originally Posted by crayiii

https://forums.sailboatowners.com/th...system.196179/

Thanks, that's really useful. I note that the measurement is under load and the difference between C3 and C10 is not that great.

[rgleason]

The "C3" is 0.3C or 30a. The "C10" is 0.1C or 11a. Very confusing use of terms IMHO.
The batteries seem to hold up ok.

[RickG]

Originally Posted by rgleason

I can't read that attachment, but I found the original document from Firefly

Test report ETL 16-Voltage vs SOC G31 Voltage vs SOC% the answer seems to be 12.02 or 12.01 at 40% SOC using C3 or C10. What is C3 3x the battery capacity or .3?

We would not be worryiing about this if they were LFP.


Not the link but related testing
https://coastalclimatecontrol.com/in...g-reveals.html
https://panbo.com/gizmos-new-firefly...t-the-details/


DoD What's the Latest on Firefly Oasis Batteries? - Gear Anarchy - Sailing Anarchy Forums
DOD 60% = 2350 cycles.

The attached test report is what I use to judge SOC vs. Voltage. I disconnect the batteries at the switches for a couple of hours and check the voltage at night with no charging or load. It seems to track within 0.01V with what my BMV-712 is counting.

Rob at Coastal Climate Control knows his stuff and is always testing and experimenting. I bought my batteries and solar from them.

Cheers, RickG

[rgleason]

Originally Posted by RickG

The attached test report is what I use to judge SOC vs. Voltage. I disconnect the batteries at the switches for a couple of hours and check the voltage at night with no charging or load. It seems to track within 0.01V with what my BMV-712 is counting.

Rob at Coastal Climate Control knows his stuff and is always testing and experimenting. I bought my batteries and solar from them.

Cheers, RickG

Where is the attachment? The one I attached is voltages measured at the end of a long discharge.

[RickG]

Originally Posted by rgleason

Where is the attachment? The one I attached is voltages measured at the end of a long discharge.

I interpolate the SOC vs V to check apparent charge level. I don't do a C10 test. It may not be precise, but it appears accurate.

Cheers, RickG

[Jetx]

I use the same chart, and *think* it’s fairly accurate (I use it to adjust the %SOC on my Victron battery monitor after a few weeks of daily partial-SOC cycling). Note though that these are NOT resting voltages, they’re voltages measured under-load. It just so happens that when I’m brewing coffee in the morning, my current draw is close to the 0.3C rate for my bank of 8 G31’s, so I compare measured voltage at that time to the chart, and adjust the SOC on the battery monitor if it’s getting too far off.

The reason I think the chart is fairly accurate is that if I adjust the displayed SOC as described, then plug in to shore power and charge until tail current is roughly 1A per battery, the amp-hours put into the batteries is fairly close to what is expected, based on the starting SOC, with some allowance for charge efficiency (after some trial and error, I use 96%).

[rgleason]

Originally Posted by Jetx

I use the same chart, and *think* it’s fairly accurate (I use it to adjust the %SOC on my Victron battery monitor after a few weeks of daily partial-SOC cycling). Note though that these are NOT resting voltages, they’re voltages measured under-load. It just so happens that when I’m brewing coffee in the morning, my current draw is close to the 0.3C rate for my bank of 8 G31’s, so I compare measured voltage at that time to the chart, and adjust the SOC on the battery monitor if it’s getting too far off.

The reason I think the chart is fairly accurate is that if I adjust the displayed SOC as described, then plug in to shore power and charge until tail current is roughly 1A per battery, the amp-hours put into the batteries is fairly close to what is expected, based on the starting SOC, with some allowance for charge efficiency (after some trial and error, I use 96%).

Thanks Jetx for providing that clarity. The voltage is measured during the drawdown.

[MerMike]

Per the user manual, "Firefly batteries do not require a float charge on a regular basis. However, if you are float charging, due to their longer projected lifespan, it is important to keep the float voltage at 13.4V or 13.5V (4.5V for each 4V/450AH) to ensure the battery lasts for as many cycles as possible."

What do you do when you leave the boat for an extended period? Do you keep your batteries on float? Turn the charger off entirely? What have been the results?

Any thoughts on whether the recommended float voltage is a minimum? Is there any benefit to setting it lower for winter storage, while the boat is still in the water but not being used much?

Finally, should temperature compensation be taken into account when monitoring the float voltage, or should the batteries be maintained at 13.4V regardless of temperature?

Thanks in advance.

[rgleason]

I would be very interested in the particulars and best practices when leaving the boat on a mooring for say 5 days, to charge up to 100% Soc from 80% SoC and then float properly during the day. Location:Rhode Island. What size panel(s), voltages needed and controllers are needed and best. Size of bank (2) G31.

Should the solar be disconnected if gone for longer periods?

[sailorboy1]

I just leave mine on with it's normal solar settings. My controller will drop to float of current fey low enough, but that is fairly rare