Capacity Tesing

[timber1111]

What is the latest best way to capacity test 100 Ah lifepo4 batteries?
Trying out some of the offerings on Amazon and want to make sure I am getting what I paid for.

Thanks

 

[Tim Tim]

What is the latest best way to capacity test 100 Ah lifepo4 batteries?
Trying out some of the offerings on Amazon and want to make sure I am getting what I paid for.

Thanks

Buy one of these and set it to a 5A load. The aligator clips are useless so change them to terminal connectors to suit the size of your battery terminals.

Link now added.

https://www.amazon.com/MakerHawk-El...39324&sprefix=Battery+capacity,aps,282&sr=8-6

 

[A.Justice]

I have a DL24P capacity tester that works great. They are about $40 from China, or $90 in the US.

Another option would be to use a shunt, which you'll probably want for your battery anyway. Just hook up the shunt, and a constant load, and let it run till empty.

 

[timselectric]

My house is my load test. The shunt tells me the capacity. This is how I test each new battery.

 

[timber1111]

Thanks for the great input all!

So I set up a shunt with and deep freeze as a load pulling about 23 watts and only got 24 Ah out of the 100 Ah battery
Any clues on what is wrong? bad battery? not doing this test right?

Equipment list:

https://www.amazon.com/dp/B07T8GN61Z?psc=1&ref=ppx_yo2ov_dt_b_product_details

(DC Multifunction Battery Monitor Meter)

https://www.amazon.com/gp/product/B07SWW6Y7D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

12v inverter

https://www.amazon.com/dp/B094NN5KWY?psc=1&ref=ppx_yo2ov_dt_b_product_details

100 Ah battery, fully charged with a victron smart charger

Thanks!!

 

[timselectric]

Are you sure that it was fully charged and balanced?

 

[timber1111]

Are you sure that it was fully charged and balanced?

as far as I know. set on victron smart charger for 24 hours, had 13.4 volts at start of test not sure what else could be done to make sure it was fully charged.

 

[timselectric]

I would go to 14.4v. Hold there until less than 1a drawing.

 

[timber1111]

I would go to 14.4v. Hold there until less than 1a drawing.

I will double check but I'm pretty sure 14.4 is the charging voltage, but once off the charger, the battery settles at 13.8.
I will double check that though

 

[timber1111]

I will double check but I'm pretty sure 14.4 is the charging voltage, but once off the charger, the battery settles at 13.8.
I will double check that though

I will double check but I'm pretty sure 14.4 is the charging voltage, but once off the charger, the battery settles at 13.8.
I will double check that though

Turns out, after fully charging to "storage" stage on the victron 12v smart charger, once taken off the charger the battery settles at 13.8v.

 

[timber1111]

Turns out, after fully charging to "storage" stage on the victron 12v smart charger, once taken off the charger the battery settles at 13.8v.

Sorry 13.5v

 

[timselectric]

Sorry 13.5v

Yes, that's the resting voltage.
The goal is to make sure that the battery has reached full. Holding it at the higher voltage is how to accomplish this.

 

[Texas-Mark]

So I set up a shunt with and deep freeze as a load pulling about 23 watts and only got 24 Ah out of the 100 Ah battery

What did you use as a basis for determining you only got 24Ah? One possibility is the inverter probably shut down from low voltage before the battery was actually depleted. Or the freezer compressor kicking in tripped it (or the BMS).

I would suggest using a strictly resistive 12V load to do capacity testing.

 

[timber1111]

I would go to 14.4v. Hold there until less than 1a drawing.

Yes, that's the resting voltage.
The goal is to make sure that the battery has reached full. Holding it at the higher voltage is how to accomplish this.

ok, found out the victron settings were on default for li-ion......which are wrong for this battery. So I fixed this, recharged overnight to 14.6v per spec req's for this battery.

Now have it hooked up to a fan running on high:
Start voltage 13.5
Amps being pulled: 1.35A
Watts: 17.9W
Starting time 10:26 am

We'll see what happens but after only 20 minutes battery voltage is already 13.2V

 

[timber1111]

What did you use as a basis for determining you only got 24Ah? One possibility is the inverter probably shut down from low voltage before the battery was actually depleted. Or the freezer compressor kicking in tripped it (or the BMS).

I would suggest using a strictly resistive 12V load to do capacity testing.

here is my setup, so when the battery quit, the battery monitor read 24 Ah....
I have a new charging profile for the victron charger, so maybe this will help.

Equipment list:

https://www.amazon.com/dp/B07T8GN61Z?psc=1&ref=ppx_yo2ov_dt_b_product_details
(DC Multifunction Battery Monitor Meter)

https://www.amazon.com/gp/product/B07SWW6Y7D/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
12v inverter

https://www.amazon.com/dp/B094NN5KWY?psc=1&ref=ppx_yo2ov_dt_b_product_details
100 Ah battery, fully charged with a victron smart charger

 

[timber1111]

Buy one of these and set it to a 5A load. The aligator clips are useless so change them to terminal connectors to suit the size of your battery terminals.

have not tried this method yet, trying fan as a load right now, it is really steady at 1.35A on the load, this battery should last a week!!! but i don't think it will.

 

[Texas-Mark]

here is my setup, so when the battery quit, the battery monitor read 24 Ah....

But did it quit from low voltage or because the BMS got tripped (over current) when the freezer compressor kicked in? The inverter should have gone into low voltage alarm/cutoff before the battery should have hit low voltage cutoff.

 

[timber1111]

But did it quit from low voltage or because the BMS got tripped (over current) when the freezer compressor kicked in? The inverter should have gone into low voltage alarm/cutoff before the battery should have hit low voltage cutoff.

yes, the inverter quit, it was beeping and the battery was actually still showing voltage, around 11v by the time I got to it

 

[Tim Tim]

have not tried this method yet, trying fan as a load right now, it is really steady at 1.35A on the load, this battery should last a week!!! but i don't think it will.

My apologies but realised the link was missing.

https://www.amazon.com/MakerHawk-El...39324&sprefix=Battery+capacity,aps,282&sr=8-6

 

[Texas-Mark]

My apologies but realised the link was missing.

https://www.amazon.com/MakerHawk-El...39324&sprefix=Battery+capacity,aps,282&sr=8-6

I use this version. Has sense leads and the color display is nice too.

https://www.amazon.com/Vastarry-Electronic-Capacity-Monitoring-Constant/dp/B0B56SP7Y9