lifepo4 coulomb capacity LCD meter

TK15 High Precision LiFePO/Lithium/Lead Acid Battery Tester Coulomb Counter 50A

Lifepo4 battery reads about the same voltage 13.1 volts whether it's 20 percent full or 80 percent full, making it difficult to figure out what the remaining capacity is by just using the voltage as a guideline.
I decided to get this lcd meter to keep track of battery status. This meter can also be used on other type of batteries lead acid, li-ion, and can measure up to 590 ah capacity, this one is rated 50 amps, but they sell ones that can handle higher amps at higher price point. I paid 21.99 for it on ebay, it ships from china and recieved it fairly quickly, ordered it on a tuesday and got it the following week on thursday. 

This meter when you set it up, you enter the battery capacity in amp hours (110 ah in my case), and also at what voltage the battery is full (14.6 volt lifepo4) and its discharged voltage (11.2 volt lifepo4).
There is a small amp sensor that connects between the battery and the output cables, it keeps track of all amps going in/out of the battery, the battery amp hour capacity on the lcd screen is updated as the battery is charged or discharged, and it gives you a real-time percentage of battery status.
It also shows how many actual amps are going in/out of the battery and the time to fully charge or discharge battery at the current amp rate its encountering.

When nothing is happening the Lcd shows battery status but light is off. When discharging the light on display is always on, when the battery is charging the light slowly blinks on and off. The only disadvantage is if your using the battery at nightime, the light can be pretty bright, but I just cover it with something. It came with no instructions but there are settings to shutoff the light.

So far it's been working well, on the picture, it shows status of battery after 5 hours of use from a fully charge condition. I used a dc wattmeter to check how accurate it is. Most of the readings are very close, The amps use (coulometer shows 15 amps used 110ah - 15ah = 95ah versus 13.8 amps used shown on dc wattmeter) is the only one that differ slightly but for me it was close enough for the 22 dollars I spent. 

dc wattmeter on top  50 amp coulomb meter below shown while discharging battery


This is all the attaching parts

What's the functional difference between this and the watt meter? Can it track both charge and discharge?

There are 3 differences
1. wattmeter only tracks up to 60 ah then goes back to zero
2. wattmeter only tracks amps in one direction. You have to flip the connections around to track amps in reverse
3. wattmeter has to be unplugged to reset everything.

The coulomb meters are more like bi-directional amp meters.

There is another coulomb meter ( TY01 8-60V Coulomb Meter LCD Battery Capacity Tester Power Level Indicator ) I been testing, which is almost the same as the TK15, it uses the same amp sensor, and can be use on up to 600 ah battery banks. This one you can't program the high/low voltages of the battery, but you can program the battery ah capacity. I paid 17.00 dollars for it. This one is much simpler as it only shows one thing on the LCD, percentage, but by pressing the lower button it will cycle to show voltage, amps being used, amps remaining, it doesnt show watts like the tk15, or tell you how many hours remain at current amp usage. The light also behaves similar off when nothing is going on, blinking when charging, and constantly on when discharging.

So far both have been working great, I recommend either one for those with lifepo4, but they can also be used on any type of battery. TK15 shows everything on the screen while the TY01 only shows one thing at a time. 

TY01

Great info. I think I'll try one out. I've been using the 100a rc type meters - one on the solar panel input, and one on the battery output, to show amps taken in (and voltage etc) and amps spent (and voltage etc).

I like the idea of this meter, but I think the light will be annoying. I guess I can make a little cover for it. The rc type meters I'm using now glow blue all the time anyway.

This unit looks interesting too: https://www.ebay.com/itm/DROK-DC-0-...ge-Discharge-Battery-Tester-Volt/253212149044

I actually have one of the droks meters, its wireless, you connect the sending unit to the battery and the actual meter where ever you need it. 

One fatal flaw I found on mine was the unit was using up 1 amp of power, if my controller/amp meter/dc wattmeter/drok said 6 amps were going into the battery, I was able to verify that only 5 amps were going into the battery. That and the wireless connection even from 5 feet way would be cutting in/out constantly. It does have over/under voltage/current protection, but I wouldn't recommend it for monitoring battery capacity. It can monitor capacity but its confusing how it counts up and down, and the 1 amp discrepancy didn't assure me about its accuracy.  

The lights on the coulomb meters are annoying but I just cover them up at night. So far they been working perfect, 5 years using solar this is the first time where I can actually see if my battery is performing to it's capacity, no more guessing how much power I'm using.

If I was going to get one later, I would get the non-wireless version, as I don't want more RF interference in my van. I'm a ham radio operator, and many of these devices send RF splatter everywhere. I went with morningstar because their solar controllers are less noisy than others.

I did purchase the 50a version model like you mentioned. Should be here in a few days.

I also separately have purchased a low voltage disconnect that uses mosfets with a delay for low voltage cutoff, and a low voltage alarm that I can enable and disable.

Got my tk15 in today. I have 2 100ah batteries in parallel. Set it to 100 or 200 on the meter?

My thinking is if it is set to 100, would it not show 0% after using 100 and would it not show only 50% if I'd set it to 200ah?

200AH.

Does it ask charge efficiency factor, temp correction coefficient or Peukert exponent?

Has 3 settings that I could see. I only pressed enter key for a few secs.

Capacity
0 voltage
Full voltage

OK.

Probably useful for Volts and AH-in and -out, if so great for the price

but can't be too accurate for SoC

Yeah, the 2 devices I was using prior would show similar info, but didn't have a "0-100% battery gauge" like this one does, showing the percentage of capacity remaining.

I tried setting it to 100 just to see what it would look like. I might set it to 200 in a day or two. It's raining today, so I should be able to see some changes in levels.

But for 20 bucks, yeah, it's not too shabby.

> a "0-100% battery gauge" like this one does, showing the percentage of capacity remaining

Yes that's the part that won't be too accurate without those factors I mentioned required by a good AH-counting SoC calculator. Don't rely on it too much.

Does it let *you* tell *it* when the bank is 100% full?

Now that I think about it, the SoC% indicator is maybe based on simply reading voltage.

Does it let you specify battery type, FLA vs AGM etc?

John61CT said:

>  a "0-100% battery gauge" like this one does, showing the percentage of capacity remaining

Yes that's the part that won't be too accurate without those factors I mentioned required by a good AH-counting SoC calculator. Don't rely on it too much.

Does it let *you* tell *it* when the bank is 100% full?

Now that I think about it, the SoC% indicator is maybe based on simply reading voltage.

Does it let you specify battery type, FLA vs AGM etc?

Click to expand...

You can manually tell it what voltage full and empty are.

It seems like it works pretty well so far.

It counts the amps as they go in or out. Shows watts as well right next to it. Voltage on the left.

It then shows battery percentage, and total ah within the battery.

Ah, great, so it uses that voltage calculation, the AH counting is not used for SoC%.

Just know it will be accurate at the top and bottom if you set those voltages properly, but LFP's SoC vs V curve is so flat between 10% and 95%, don't expect that to be too accurate.

Keeping an eye on the AH in and out will be better for anything critical.

John61CT said:

Ah, great, so it uses that voltage calculation, the AH counting is not used for SoC%.

Just know it will be accurate at the top and bottom if you set those voltages properly, but LFP's SoC vs V curve is so flat between 10% and 95%, don't expect that to be too accurate.

Keeping an eye on the AH in and out will be better for anything critical.

Click to expand...

Yeah, I think it does the math on the amps on and out. Very nice for 20 bucks.

Oh and one more thing... It is supposed to calculate by default the percentage for lead acid batteries without changing the empty and fill settings from 0. Supposedly you only set the empty and full voltage for lithium or other types.

After fully charging the batteries with no load yesterday, I then hooked up the fridge at dark. It ran all last night and the meter said 8 ah used. That's about what I'd calculated before using the RC watt meters.
So the percentage showed 92 percent remaining, and the ah said 92 ah remaining.

If I'd had set it to 200ah capacity, I'm sure it would have showed 96 percent remaining and 192 ah.

Today, on a cloudy and rainy day, I saw that by lunch time, I was back to 94 ah, and 94%.

It was still charging at a rate of 1 amp in from the 200w panels at noon.

Checked again just now at 9:30pm, meter says 98 percent.

It was at 99 percent at about 4:30pm. The fridge was eating away some amps, then the solar would put some back. I left my watt meter attached to the load side. Says 18ah used in about 27 hours or so.

What model fridge, inside vs ambient temps, is it full?

John61CT said:

What model fridge, inside vs ambient temps, is it full?

Click to expand...

It's the dometic cc40us. Inside temp is set to 32. Ambient is average 60 for last 24 hours.

It is 3/4 full. A case of bottled water in it . I'll check again the usage tomorrow around 9 am.