replace UPS battery with lithium ion?

From what I've seen lithium iron phosphate is a near drop-in replacement for lead acid. The exact voltages differ slightly from lead but if you have access to the charge profile can be managed.

If you don't have access to the charge profile it's another matter. LiFePO4 can be charged at 1C rates to 14.4-14.6 volts in a 4-cell battery. For long durations, 13.8-14.0 V is considered desirable. That's not wildly different from lead acid behaviro, but neither is it identical. In particular the full-charge float current is apt to be much lower for LiFePO4, leading to long-term overcharge.

Safetywise I'd say LiFePO4 is safer than lead acid. Neither is able to self-ignite and the former isn't even corrosive. Both are equally good firestarters 8-)

hth,

bob prohaska

If you end up doing this, I will be interested to here how it goes.

Thanks

This is a response to the post seen at:

I won't be doing it. Seems too risky for me and I lack enough knowledge in order to make the necessary circuit changes.

Thought that was a scam site. Went there and they wanted me to answer a question before showing me that page.

The real question is: Why would you want to? Which problem are you trying to solve?

Lithium batteries age more quickly when they are kept at full charge, while lead batteries age best when they yare kept at full charge.

Lithium batteries are lighter and smaller for the same amount of energy, but for stationary use, it does not matter.

Lithium is, as you have found out, more expensive than lead.

For standby applications such as UPS and emergency lighting, lead-acid batteries are simply superior on all levels.

HW, Are the batteries in Cellphones Lithium?

A friend has his cellphone connected to the A.C. line 24/7. He asked me once thinking it was a bad idea and I told him I figured the charging circuitry would/should taper the charging level down after the battery gets fully charged

Reading your post caused me to want to ask you about the battery in a cellphone. Ed.

Yes, they are.

Yes, all lithium chargers will stop when the battery is fully charged. They have to, otherwise the battery will be damaged or even catch fire.

But keeping the battery at 100% charge for a long time is "stressful" for the battery. It is a time thing: The longer you keep it at 100%, the harder it is for the battery.

Most people replace their phone well before the battery is worn out, so it's probably fine.

If you want your battery to last as long as possible, it is best to not keep it fully charged for extended periods of time. Many phones can be configured to charge the battery to some value, like 85%. Apple have a feature where, if you have an alarm set, the phone will charge to 85% and hold it there all night, and then fully charge the battery just in time for the alarm time.

Some electric cars have a feature where you can tell it to charge the battery to less than 100% for those days when you know you don't need the full range.

My laptop computer has a similar feature, where I can configure it to stop charging at less than 100%.

So, check if the phone has a battery save feature.

LiPo (Lithium Polymer).

Agreed. That's the way it's suppose to work. However, I've seen a few phones that don't know when to quit charging. If you're worried about premature battery death due to failure to stop charging, you might want to invest in a USB-C tester:

I've seen statistics claiming that the typical lifetime of a phone is about 2.5 years.

Note: If the 2.5 year life test results included lost phone, damaged phones, 3rd part junk batteries, fashion failure, feature envy and other reasons to replace the phone, it might be correct. If the test results included only battery failures, then I believe it's probably too low.

Thanks HW, My friend has had several phones quit working on him. He probably will continue doing as he has.

Myself, I charge this phone while asleep each night. Ed

I have my cell phone charging most all the time. I may pick it up once or twice when I go out. Retired so around the house most of the time. I use a landline for almost all the calls. Never had a problem with the cellphone battery that I can recall in 10 years of using a couple of updated phones.