Lifepo4 12.8v, 100amp hour battery

[flyfisher]

I run my Air Venturi Rovair compressor with a Lifepo4 , 12.8v, 100ah battery with a volt/percent meter attached to it. Last week my compressor was working then stopped. I looked at the battery percentage and it read 40%. I hooked up my charger for that battery and charged it to 100%.Today I noticed something peculiar. I put the meter in % mode to see how much a compressor cycle would affect the charge of the battery. I started the compressor that was hooked up to my 1100z. I watched the percentage go down to 92%. After the compressor stopped., the meter slowly went back up to 100% (took about 30 seconds) Can someone tell me why the percentage went down then back up to 100%?
Thank you in advance.
Bill

 

[ctshooter]

Most likely % of charge is based on the output voltage of the battery. When you run the compressor you create a voltage sag on the battery due to the load. Once the load has been removed, and as long as you haven't taken out that much charge, you'll see the battery recover but maybe not to 100%.

While I would expect it to be a bit quicker than the 30 seconds of recovery time you mention, I've never had a 100Ah battery to compare with of that chemistry.

 

[Auto1191]

Do a load test, or bring the battery somewhere they could test it for you. This will tell you the true cca , If it is like a car size battery

 

[Billm]

Exactly what ctsshooter said. The Lifepo4 battery is a Lithium Ion battery. The magic of lithium batteries is two fold: high energy density and a near linear discharge down to their cut-off voltage. Most other battery chemistry’s do not have these characteristics. The high energy density means a long run time in a smaller package. As a battery discharges the voltage decreases until you can no longer use it. As a lithium battery discharges the voltage decreases very slightly from the original fully charged voltage until it reaches it cut-off power. When it gets to cut-off voltage the drop is fast and significant. If you hook a voltmeter up to the battery as it discharges you will see it drop a little bit and it’s about the same amount every minute. That allows you to estimate the amount of power left by measuring the output voltage. A 12.8v LiPo battery has a cutoff voltage of 10v. If the battery usually lasts 10 hours (Random number), the voltage will drop .28v per hour. Whenever you put a load on a battery the voltage will drop. If you hook your compressor to the battery and the voltage drops to 12.52v, your charge percentage will indicate around 90%. Remove the load immediately and it will indicate 100% or very close to it. A 12.8v LiOn is made up of 4 cells recovery time could be a weaker cell. The downside to Lithium batteries are the expense, volatility and the fact that if you discharge it below the cut-off voltage the battery can be ruined (or at least for the average user).

 

[flyfisher]

Do a load test, or bring the battery somewhere they could test it for you. This will tell you the true cca , If it is like a car size battery

This battery is for things like a trolling motors, it is rated for 5,000 charging cycles. I don't think there is a cca rating. I bought the battery 2 years ago when I got the air compressor and was only charged 2 times, once when I first got it and again last week.

 

[flyfisher]

Exactly what ctsshooter said. The Lifepo4 battery is a Lithium Ion battery. The magic of lithium batteries is two fold: high energy density and a near linear discharge down to their cut-off voltage. Most other battery chemistry’s do not have these characteristics. The high energy density means a long run time in a smaller package. As a battery discharges the voltage decreases until you can no longer use it. As a lithium battery discharges the voltage decreases very slightly from the original fully charged voltage until it reaches it cut-off power. When it gets to cut-off voltage the drop is fast and significant. If you hook a voltmeter up to the battery as it discharges you will see it drop a little bit and it’s about the same amount every minute. That allows you to estimate the amount of power left by measuring the output voltage. A 12.8v LiPo battery has a cutoff voltage of 10v. If the battery usually lasts 10 hours (Random number), the voltage will drop .28v per hour. Whenever you put a load on a battery the voltage will drop. If you hook your compressor to the battery and the voltage drops to 12.52v, your charge percentage will indicate around 90%. Remove the load immediately and it will indicate 100% or very close to it. A 12.8v LiOn is made up of 4 cells recovery time could be a weaker cell. The downside to Lithium batteries are the expense, volatility and the fact that if you discharge it below the cut-off voltage the battery can be ruined (or at least for the average user).

I bought the battery 2 years ago when I got the air compressor and was only charged 2 times, once when I first got it and again last week. When the compressor stopped about half way to the shut off pressure, the battery was at 40%. It charged to 100% over night. considering I shoot my 2 PCP's 4-5 of the colder months of the year, I got 8-10 months from the initial battery charge before it needed to be recharged. I shoot in my basement only. I decided to use 12v battery from the start, I figured it would save a little on my electric bill. And by the way, thank you all tor your explanations. Much appreciated.
Bill

 

[Auto1191]

I bought the battery 2 years ago when I got the air compressor and was only charged 2 times, once when I first got it and again last week. When the compressor stopped about half way to the shut off pressure, the battery was at 40%. It charged to 100% over night. considering I shoot my 2 PCP's 4-5 of the colder months of the year, I got 8-10 months from the initial battery charge before it needed to be recharged. I shoot in my basement only. I decided to use 12v battery from the start, I figured it would save a little on my electric bill. And by the way, thank you all tor your explanations. Much appreciated.
Bill

Just for an example , if you were to use portable compressor on a car battery , you would would drain the car battery if the vehicle was not running

 

[Billm]

I bought the battery 2 years ago when I got the air compressor and was only charged 2 times, once when I first got it and again last week. When the compressor stopped about half way to the shut off pressure, the battery was at 40%. It charged to 100% over night. considering I shoot my 2 PCP's 4-5 of the colder months of the year, I got 8-10 months from the initial battery charge before it needed to be recharged. I shoot in my basement only. I decided to use 12v battery from the start, I figured it would save a little on my electric bill. And by the way, thank you all tor your explanations. Much appreciated.
Bill

You’re welcome. I was an electronics tech in the Navy for 13 years and then owned hobby shops for 20 years lithium batteries are the lifeblood of radio controlled planes, helis, drones, trucks, boats and cars. It’s really bad for any battery to not be used often or left on a charger and even worse for lithium chargers. Even if you’re not using the battery and discharging it often, try and use it down to about 50-60% of its charge before storing. Even better is to charge it and run it down every few weeks. Usually once a lithium battery drops below its cutoffs voltage, the charger won’t try to charge it for safety reasons. High end hobby chargers have two functions that most consumer chargers don’t have: a cycle function where the charger charges the battery and then discharges it and does the cycle several times, it increases the batter life. The other function is a storage charge function, it charges it, then automatically discharges to the best storage voltage. If you think your battery is draining too fast, charge it then run your compressor with its drain valve open until the battery needs to be charged again and then charge it again. Do that a few times and you might be able to refresh the life of your battery. Leave the valve open so that there’s no real load on the compressor. It’s important to let a lithium battery to cool down before charging. Or do more shooting lol.

 

[Billm]

The one thing that I didn’t mention was that you cannot test a battery with a voltmeter, that’s why Radio Shack sold battery checkers. It’s normal behavior for a worn battery to show a much higher voltage than the what battery is capable of of providing under load. Once a load is applied the voltage drops to what the battery can actually put out. Battery testers have a different sized resistor for each battery type inline with the test terminals. This is the reason why the older nicad batteries would show charged and then die as soon as you used them. Hopefully someone will get something useful out of my waffling lol.

 

[Auto1191]

The one thing that I didn’t mention was that you cannot test a battery with a voltmeter, that’s why Radio Shack sold battery checkers. It’s normal behavior for a worn battery to show a much higher voltage than the what battery is capable of of providing under load. Once a load is applied the voltage drops to what the battery can actually put out. Battery testers have a different sized resistor for each battery type inline with the test terminals. This is the reason why the older nicad batteries would show charged and then die as soon as you used them. Hopefully someone will get something useful out of my waffling lol.

Bill I own a repair shop, people run a volt meter across the terminals on their battery& when the they do , they think 12 volts is a good Battery . False you have to load test it. I own a high end tester that test CCA , Starter & Alt test/. By trade I am an L1 Master tech. Do you own a Tesla ?

 

[Billm]

Bill I own a repair shop, people run a volt meter across the terminals on their battery& when the they do , they think 12 volts is a good Battery . False you have to load test it. I own a high end tester that test CCA , Starter & Alt test/. By trade I am an L1 Master tech. Do you own a Tesla ?

Nope lol. Batteries belong in radio controlled cars not real ones LOL. Just kidding. The founder of one of the most well known American RC manufacturers *Team Losi” put his Lipo batteries on charge and went out to dinner. He came back to the burning embers of his house. I like Tesla products, but I prefer good old gasoline. At least for now.

 

[Auto1191]

Men of great skill & Trade . Blue collar worker to the end

 

[flyfisher]

You’re welcome. I was an electronics tech in the Navy for 13 years and then owned hobby shops for 20 years lithium batteries are the lifeblood of radio controlled planes, helis, drones, trucks, boats and cars. It’s really bad for any battery to not be used often or left on a charger and even worse for lithium chargers. Even if you’re not using the battery and discharging it often, try and use it down to about 50-60% of its charge before storing. Even better is to charge it and run it down every few weeks. Usually once a lithium battery drops below its cutoffs voltage, the charger won’t try to charge it for safety reasons. High end hobby chargers have two functions that most consumer chargers don’t have: a cycle function where the charger charges the battery and then discharges it and does the cycle several times, it increases the batter life. The other function is a storage charge function, it charges it, then automatically discharges to the best storage voltage. If you think your battery is draining too fast, charge it then run your compressor with its drain valve open until the battery needs to be charged again and then charge it again. Do that a few times and you might be able to refresh the life of your battery. Leave the valve open so that there’s no real load on the compressor. It’s important to let a lithium battery to cool down before charging. Or do more shooting lol.

The charger that I have has a battery setting for car, motorcycle, AGM and the lifepo4. . Seeing that on a full charge I got a total of 8-10 months of shooting time., and that is 4-5 months with about 7 months between sessions and 4-5 or more days a week, I thought that the battery did real good. Now if I charge the battery when it gets down to 50 or 60%, I won't get as many months from a full charge but that is not a problem since it charges full over night and I'm sure it will be better for the battery than letting it get down to 40% like I did. I do know about the charge/discharge cycle of hobby batteries because I used to race RC cars. We did the cycling when the batteries were regular rechargeable type. The lithium batteries did not become popular until shortly before I stopped racing.