# Testing Lithium Battery



## DBStoots (Jul 9, 2011)

Can’t use a traditional battery tester. How do I test a lithium?


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## Smackdaddy53 (Dec 31, 2012)

Voltmeter?


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## texasislandboy (Jul 25, 2011)

Victron makes a meter for them.


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## RaspberryPatch (Dec 17, 2016)

For what purpose? If it has a BMS that connects with OEM software, this would be best.


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## DBStoots (Jul 9, 2011)

No BMS that I know of. @Smackdaddy53 , I put a voltmeter on it after recharging and it showed good. Just wondering about using a real battery tester.


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## Headhunter (Mar 22, 2016)

Don’t you have a phone ap to check the battery status?


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## WC53 (Dec 2, 2015)

_every lithium has a bms, just a matter if you can access it. The voltage is flat for most of the discharge so voltage sort of tells you something. The amp hour meters tell you capacity through usage. For the lifepo4, usually charged to 13.8 and then voltage settles a bit, 13.5 on mine, and stays there. BMS might stop discharge at 10._


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## fjmaverick (Sep 18, 2015)

Stick it on your tongue? Actually I shouldn't joke about that I think if you touch metal while doing it might be a problem.

I'm actually not sure. I have a c-tek charger for regular batterys but I can't use it on lithium.


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## RaspberryPatch (Dec 17, 2016)

To echo what WC35 stated ...

.1. A voltmeter will tell you if the battery is deeply discharge. vThe flat curve makes it difficult to state it is fully charged
2. To be able to determine if it "fully charged", you need to read current at the "completion of charge", as it will go to near zero.
3. To be able to determines its health, you need to discharge it and monitor energy delivered - measure time, against current and less important current.

On tongue .... A lead battery has a high interrupt (shorting current), which can fuse tools, and we are talking about thousands of amps.

A typical energy (or low cost) Lithium BMS should limit current, so what current is dependent on the BMS design. An example would be 400A for 10 micro-seconds, reduce to 100A for next 200 milli-seconds, then 50A for 2 seconds, and then if the short remains, it will disconnect. If the battery truly is compliant to UL 1973 (battery, not cell (Lithium OEMs intentionally confuse this distinction)), you may also below a fuse or open a CB. Id est, the shock factor is a lot less for Lithium.


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## DBStoots (Jul 9, 2011)

Headhunter said:


> Don’t you have a phone ap to check the battery status?


Not that I know of


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## DBStoots (Jul 9, 2011)

RaspberryPatch said:


> To echo what WC35 stated ...
> 
> .1. A voltmeter will tell you if the battery is deeply discharge. vThe flat curve makes it difficult to state it is fully charged
> 2. To be able to determine if it "fully charged", you need to read current at the "completion of charge", as it will go to near zero.
> ...


"3. To be able to determines its health, you need to discharge it and monitor energy delivered - measure time, against current and less important current."

Wonder if one of the chain auto parts stores can do this?


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## WC53 (Dec 2, 2015)

No they can tell you peak current for starting loads. So if it is a starting battery, they could tell you it provides X amps.
The amp hour meter, coulometer, will measure the in and out amps and voltage giving you a picture of a batteries health and capacity. Trolling motor for x hours or head units over time depending what your use is.
Now if it is fully charged by the correct charger and you are reading under 13 or over 14 there is most likely an issue.


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## Texkitch (Jan 27, 2016)

Voltage testing just tells you state of charge but doesn’t tell much on capacity. The classic battery testers are set up for lead acid and will add resistive load to determine capacity but but not sure how effective they would be on lithium. I recently add a Victron tester to my lithium I’m using for cranking F60 to keep an eye on voltage and it shows temperature as well, which is good additional data. Uses bluetooth and connects quickly and easily. Victron Battery Tester


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## RaspberryPatch (Dec 17, 2016)

LFP lithium, unlike lead, NMC lithium or NCA lithium as previously stated has a flat discharge curve, so you cannot use Voltage to define its state of charge (SoC) or health (SoH). Then you have another issue that pertains to process control and quality of LFP lithium production and assembly, the discharge curve substantially shifts based on the rate of discharge. The degree of shift reflects process quality.

The curve below (per cell) is from what I have defined as a Tier 3 OEM, who process control is fair. (ok, there is better, and definitely there is worst). The sift here is a function just temperature, but with Tier 3 and lower, shift also happen as a function of rate of discharge, making accurate measurements moot.











Automotive repair are interested in cranking amps (short burst of power) and not energy delivery.

the following example of lead, shows it is easier to measure lead's SoC as a function of voltage, though this curve shows variance as a function of discharge rate, but the key point the curve is progressive.










fyi - at my "job", I do have people who wish to just use Voltage as a SoC for lead (simplicity), but I articulate this is an approximation as it does not account for temperature, and as above the rate of discharge. But it is a fair estimate, which you cannot do with LFP. or some other chemistries such as Zn-Br reflow.

Also lead voltage is NOT a measurement of SOH (state of health) when charged. You can estimate lead SoH if you monitor voltage drop during discharge.


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## Headhunter (Mar 22, 2016)

DBStoots said:


> Not that I know of


Dave, sorry. The ap is is tried into the charger and is called Victron direct. Bluetooth connected and shows everything, status, charging mod, the whole deal.


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