LiFePo4 drop-in replacement batteries for UPS SLA batteries

Batteries and Chargers Rechargeable Batteries
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Yep — I understand —- Definitely by the book for others —— If it can happen it will happen

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Thanks, lots of good advice and info. Multiple incandescent light bulbs with independent switches is a clever quick way to load test. And it avoids having to remove the battery.

I might just have to take a chance on some budget no-name SLA replacements, with appropriate expectations.

@chops728, that’s one monster of a backup!

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In the end I decided to get the best quality SLA replacement batteries I could find, despite the higher cost.

Settled on CSB HRL1234F2FR, because:

  • It has a detailed datasheet. HRL1234WF2FR.pdf (662.0 KB)
  • The HRL long life series is claimed to last up to 8 years in standby use or 260 cycles at 100% discharge.
  • The vendor claimed “CSB is the original brand for APC Powerware and other UPS OEM batteries.”

I tested three of these CSB batteries in two UPS units.

One unpleasant observation was that both UPSes report a nearly instant 25% drop in capacity (showing ~75% charged) within the first couple of minutes of switching to the battery with a light load, then inching up to maybe 82% and discharging at a typical rate from there.

I’m hoping it is a calibration or reporting issue, since otherwise they seem to work fine, but it is still disconcerting. Has anyone else had this? The vendor suggested cycling the batteries a few times. The datasheet indicates that capacity increases a bit (<10%) with some cycles, but that’s nowhere close to the magnitude of the drop.

I thought they could be aged batteries that have lost 25% of their capacity, but the vendor said it is new stock. Not sure if it can be believed, but they seem to be one of the official vendors for CSB in Canada.

As for actual runtimes, here’s what I measured:

APC BE550G-CN @ 5% load (~16.5W): 2h32m
CyberPower CP1500PFCLCD @ ~8% load (72W): 1h24m

The CP1500PFCLCD’s load can be quite jumpy, but that’s around the average.

I’m not sure if it’s just me, but I thought the original batteries provided about half an hour more runtime for each UPS, though I don’t have records.

I had hoped for more runtime, but I suppose this is the norm. APC’s product page specifies 1h52m for a minimum 10% (33W) load, and CyberPower indicates 1h40m for a ~5% (50W) load and 1h6m for a ~11% 100W load.

Now time will tell if they live up to the longevity claim.

As for the old batteries being replaced, I discovered/observed a few things:

  • High internal resistance means a bad battery, but low internal resistance does not necessarily mean the battery is good. Capacity can apparently degrade independently of internal resistance. One bad battery measured at 19 mΩ, another at 75 mΩ (and after resting out of the UPS for days it measured at >300 mΩ). Another aged battery at about half of original capacity tested at 22 mΩ. New spec is typically ~19 mΩ. The three new CSB batteries tested at 13-15 mΩ, with a spec of ~17 mΩ. Tested with a car battery analyzer (Ancel BA301) set to 130A CA (cranking amps testing standard at 0C) measured at room temperature.

  • SLA batteries are apparently not supposed to be oriented upside down. If true, the CyberPower CP1500PFCLCD has a design flaw with one of its two batteries mounted upside down, in at least the first two revisions of the unit. A more recent revision has moved the upside down battery to be mounted vertically…

  • The upside down battery in the CP1500PFCLCD UPS has the high internal resistance of 75 mΩ (and >300 mΩ) while the other battery mounted right side up measured at 19 mΩ. Coincidence? I dunno, but sure makes me wonder.

1 Thank