Capacity monitoring of LiFePO4

[ffrree]

I was wondering how accurate the capacity monitors on the market are?

The reason I ask is, some of them don't need calibration, and some only calibrate the "zero" point by discharging the battery, but what about the "full" point ?

Some measure the current going in and out, but without calibration, they can only measure the net gain or drain, but not absolute capacity, is it?

The LiFePO4 batteries have a very flat voltage/capacity curve, and they are different from batt to batt, plus the batteries voltage would settle down after charged, so how accurate can that be ?

Any comments ?

 

[MisterSandals]

the capacity monitors on the market

Which capacity monitors? The shunt based monitors (coulomb counter) is pretty accurate but i believe they need to be periodically recalibrated.
Other Hall Effect monitors are also pretty good but all the inflows and outflows for the battery must be wired thru the ferrite ring.
The cheaper voltage based ones, i find anyway, are usually reporting a lower SoC than what i consider to be 100% (where the cells settle after a full charge). I think many assume that 14.4v (about) is 100% but there is dang little capacity from there down to settle point.

Personally, i find that after working with a bank on a near daily basis for a few weeks/months that i know the SoC at a glance at the (no load) voltage.

Did i get anywhere near answering your question? It was fairly vague.

 

[Q-Dog]

I can only comment on the Victron 712, but it recalibrates when the battery is fully charged. You set the voltage that you want the monitor to consider as 100%, plus the capacity of the pack and the efficiency and it counts down from that.

 

[ffrree]

Which capacity monitors? The shunt based monitors (coulomb counter) is pretty accurate but i believe they need to be periodically recalibrated.
Other Hall Effect monitors are also pretty good but all the inflows and outflows for the battery must be wired thru the ferrite ring.
The cheaper voltage based ones, i find anyway, are usually reporting a lower SoC than what i consider to be 100% (where the cells settle after a full charge). I think many assume that 14.4v (about) is 100% but there is dang little capacity from there down to settle point.

Personally, i find that after working with a bank on a near daily basis for a few weeks/months that i know the SoC at a glance at the (no load) voltage.

Did i get anywhere near answering your question? It was fairly vague.

Thanks. Yes you have answered my questions, basically confirming my suspicions that all capacity measurements must be calibrated and recalibrated, e.g. when adding or changing new batteries etc. The voltage ones are not reliable as I see it. So here it goes.

BTW, what type or model of capacity meter do you use or recommend. Especially, I would like to have one that either warns or disconnect battery from damaged by over voltage, under voltage, over current ( not too important as fuses can take care of it somehow ).

 

[GVSolar]

I can heartily recommend the Thornwave PowerMon - Bluetooth Battery Monitor - very versatile - can measure up to 60A with integrated shunt - and 500a with external shunt - logging capabilities - nice android/iphone app - coulomb counting - can monitor SOC in % and by remaining time at current discharge rates - can fire SSRs to disconnect/connect according to set parameters - using programmable LFP charge manager - remote on/off with phone app. I've been using it for 6 months - excellent. Customer support is very responsive and helpful.

PowerMon - Bluetooth LE Advanced Battery Monitor / DC Power Meter with data logging

We developed the PowerMon device to provide an affordable, high-tech solution for monitoring electrical systems. Whether you're in an RV, camper, or boat, utilizing solar systems, or managing off-grid setups, PowerMon is designed to meet your battery monitoring needs. Remotely monitoring DC...

www.thornwave.com

 

[ffrree]

I can heartily recommend the Thornwave PowerMon - Bluetooth Battery Monitor - very versatile - can measure up to 60A with integrated shunt - and 500a with external shunt - logging capabilities - nice android/iphone app - coulomb counting - can monitor SOC in % and by remaining time at current discharge rates - can fire SSRs to disconnect/connect according to set parameters - using programmable LFP charge manager - remote on/off with phone app. I've been using it for 6 months - excellent. Customer support is very responsive and helpful.

PowerMon - Bluetooth LE Advanced Battery Monitor / DC Power Meter with data logging

We developed the PowerMon device to provide an affordable, high-tech solution for monitoring electrical systems. Whether you're in an RV, camper, or boat, utilizing solar systems, or managing off-grid setups, PowerMon is designed to meet your battery monitoring needs. Remotely monitoring DC...

www.thornwave.com

Thanks. I have to figure out how to get this in Australia...interesting cetainly.

 

[Mittmy]

I hope this is the correct place to post this question. If not please advise. I have been following the threads and Will's review of the AiLi battery monitor (Amazon $44) and would like to get one. But I see many issues here and on Amazon with early failures, readings that stop, not working as advertized. What is the current feelings and experiences with this little inexpensive battery monitor as far as reliability?