LifePo4 battery at 13.49 volts, but 12.7% Capacity??

[Dazed and Confused]

Hi folks

This is my first lithium battery, so I am hoping someone can set me straight.

I have a WEIZE 12V 100Ah LiFePO4 lithium battery, currently on a Battery Tender Junior 12V Battery Charger and Maintainer: 800mA 12 Volt switchable battery charger- set to the Lithium setting.

I have installed battery monitor which shows the voltage (disconnected from the charger) is at 13.48v and but 12.7% capacity.
The light on the Battery Tender is solid amber- indicating it is connected correctly, and charging.

The rate that the capacity percentage climbs is approximately 1% per hour.

Does this seem right?
Sorry for what may seem like a dumb question. Like I said, this is my first lithium battery.

Thanks in advance!
D&C

 

[Madco]

The state of charge increasing about 1%/hr is consistent with charging at 800mA. Should be about 1.25%/hr.

 

[mikefitz]

Your battery monitor capacity reading is incorrect. More details would be helpful.
Mike

 

[Dazed and Confused]

Your battery monitor capacity reading is incorrect. More details would be helpful.
Mike

This is not surprising. It's from China.....

What details can I provide?

 

[Lt.Dan]

I do not think it is reading incorrect. When was the last time it had a full charge? If it has been a significant amount of time, then the shunt or coulomb meter will drift over time, getting more and more inaccurate. The only way to get it to recalibrate is to charge it above its 100% threshold, which could be anywhere above 13.6v, depending on the programming.

Shunts and coulomb meters ALL will do this, no matter how accurate they are, there will be drift and parasitic draw that gets pulled from the battery that they cannot calculate correctly.

Give it a full charge and it should go back to normal, then regularly give it a full charge atleast once every few days or so, to stay accurate.

 

[Dazed and Confused]

I do not think it is reading incorrect. When was the last time it had a full charge? If it has been a significant amount of time, then the shunt or coulomb meter will drift over time, getting more and more inaccurate. The only way to get it to recalibrate is to charge it above its 100% threshold, which could be anywhere above 13.6v, depending on the programming.

Shunts and coulomb meters ALL will do this, no matter how accurate they are, there will be drift and parasitic draw that gets pulled from the battery that they cannot calculate correctly.

Give it a full charge and it should go back to normal, then regularly give it a full charge atleast once every few days or so, to stay accurate.

Thanks, Lt.Dan

This is the very first charge. So what you said makes sense.
I guess I expected it to charge at a little faster rate.

 

[Lt.Dan]

Thanks, Lt.Dan

This is the very first charge. So what you said makes sense.
I guess I expected it to charge at a little faster rate.

No problem.

A 100Ah battery, being charged at .8a, and assuming they shipped it to you with 30% capacity, will take 87.5 hours to charge.

Charging at .8a (800mA), will add roughly .8%/hr, not including any losses, so your 1% increase per hour is probably rounding up, or the charger is performing better than advertised.

 

[mikefitz]

What was the battery volts before you started charging?

13.48 volts on a rested battery not under charge is at quite a high SOC.

Attempting to charge a battery with a battery tender seems a strange approach.

Detains of your battery monitor and how its attached to the battery would be useful.

 

[Dazed and Confused]

What was the battery volts before you started charging?

13.48 volts on a rested battery not under charge is at quite a high SOC.

Attempting to charge a battery with a battery tender seems a strange approach.

Detains of your battery monitor and how its attached to the battery would be useful.

You don't put your batteries on a trickle charger?

 

[Dazed and Confused]

You don't put your batteries on a trickle charger?

This is the monitor I purchased.

https://www.amazon.com/dp/B08HWFPGL5?ref=ppx_yo2ov_dt_b_product_details&th=1

 

[Crowz]

This is the monitor I purchased.

https://www.amazon.com/dp/B08HWFPGL5?ref=ppx_yo2ov_dt_b_product_details&th=1

View attachment 146977

View attachment 146978

I bought one of those to start with and found it very inaccurate with my weize lifepo4 battery. I switched out to this :

https://www.amazon.com/gp/product/B07RP5B5P7/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Love the new meter since it shows all the information at once and it tracks soc much better for me.

The first one you bought had a nicer price though Thats why I bought it at first but the renogy works better from my testing.

 

[Dazed and Confused]

I bought one of those to start with and found it very inaccurate with my weize lifepo4 battery. I switched out to this :

https://www.amazon.com/gp/product/B07RP5B5P7/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

Love the new meter since it shows all the information at once and it tracks soc much better for me.

The first one you bought had a nicer price though Thats why I bought it at first but the renogy works better from my testing.

Thanks Crowz

So maybe I’m not crazy.
I may have to consider the one you linked.

But now I have a gaping 2 1/8” hole in my battery box….. ?

 

[Crowz]

Thanks Crowz

So maybe I’m not crazy.
I may have to consider the one you linked.

But now I have a gaping 2 1/8” hole in my battery box….. ?

LOL EXACT same thing I did !



If you notice in the top of this picture you can see the inverter remote keypad for a small inverter I have in there and the "round" edges either side of it is from the hole I cut for that first gauge. I was able to get that keypad inserted into it to cover it pretty much. Thats the renogy I replaced it with under it sitting on the screwdriver holders. I haven't cut a hole for it yet.

I was going to suggest this setup I did for my gauges for people that didn't have wifi enabled fancy units that wanted to monitor remote displays to keep an eye on things. The workshop in my new house is to far to run network cables easily like my older house. So I put a wifi webcam on a table clamp microphone boom I bought off amazon. This way I can see the readouts while at my computer without having to go out to the workshop $39 wifi cam beats running network cables.

 

[Tomthumb62]

You don't put your batteries on a trickle charger?

Trickle chargers were created for lead acid batteries. Lead acid batteries love to be fully charged, all the time.

AFAIK, there’s nothing wrong with using a trickle charger to charge a lithium battery, but once it’s charged, remove it from the charger unless you can confirm it’s no longer trickle charging. Continuously trickle charging a lithium battery is not good for the battery. And keeping a lithium battery stored for long periods of time at 100% charge isn’t good either. No problem charging it to 100%, just put it to use fairly soon instead of storing it for weeks or months.

 

[Dazed and Confused]

…. No problem charging it to 100%, just put it to use fairly soon instead of storing it for weeks or months.

It’ll probably be put to use on the boat weekly, or biweekly. So that shouldn’t be a problem… ?

 

[A.Justice]

For what it's worth, I've found my Renogy battery monitor to be not the most accurate. Any current under 1 amp and the shunt has no idea what's going on. I can drain my battery to empty and as long as it's done under 1a, the shunt won't register it.

I also have one of these, and it matches my Fluke within a % or so. It's also much less than the Renogy.

bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt https://a.co/d/3B5Fvc6

 

[Tomthumb62]

For what it's worth, I've found my Renogy battery monitor to be not the most accurate. Any current under 1 amp and the shunt has no idea what's going on

So I wonder if other shunts are more accurate than the Renogy and it’s lookalikes?

Junctek? Victron? Aili? I would assume that Victron would be able to track sub 1A draws, but I don’t know. That alone could be worth the price difference.

 

[jdege]

I was under the impression that LiFePO4 batteries had too flat a voltage profit for estimates of charge from nothing but voltage to be of much accuracy.

 

[Tomthumb62]

I was under the impression that LiFePO4 batteries had too flat a voltage profit for estimates of charge from nothing but voltage to be of much accuracy.

To my understanding, you’re right. However, these shunt monitors are measuring amps in and out, not voltage. There are voltage-only $15 battery “monitors”, but they’re not doing the same thing as the shunt based monitors. These voltage based ones are also not very reliable for lead acid systems, unless you remove all loads and charging sources for at least a couple hours, ideally for 24 hours.

 

[Crowz]

For what it's worth, I've found my Renogy battery monitor to be not the most accurate. Any current under 1 amp and the shunt has no idea what's going on. I can drain my battery to empty and as long as it's done under 1a, the shunt won't register it.

I also have one of these, and it matches my Fluke within a % or so. It's also much less than the Renogy.

bayite DC 6.5-100V 0-100A LCD Display Digital Current Voltage Power Energy Meter Multimeter Ammeter Voltmeter with 100A Current Shunt https://a.co/d/3B5Fvc6

Thats a bit weird in that I only had 400 to 800 mA load on the renogy for a few months and it worked fine showing discharge and charge.

From what I have read elsewhere the wifi renogy and their other products shunt wise suck at measuring accurately but the wired one I linked to is pretty accurate from what I had read and from my experience. The highest load it normally deals with is 1.8 amps max these days and again for the first few months of owning it I never even made it to the 1 amp point.

Now the volt reading isnt that accurate. Its about .1 to .2 off most of the time compared to a real volt meter. But the state of charge, time till empty/full and amp readouts are dead on with mine.