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2-Pack Eco-Worthy 12V 10Ah 256wH Lithium LiFePO4 Battery Deep Cycle for UPS $55.99 + Free Shipping
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eco-worthy-us via eBay [ebay.com] has 2-Pack Eco-Worthy 12V 10Ah 256wH Lithium LiFePO4 Battery Deep Cycle for UPS on sale for $69.99 - $14 (20%) off when you apply coupon code LOVEIT20 on the checkout page = $55.99. Shipping is free.
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eco-worthy-us via eBay [ebay.com] has 2-Pack Eco-Worthy 12V 10Ah 256wH Lithium LiFePO4 Battery Deep Cycle for UPS on sale for $69.99 - $14 (20%) off when you apply coupon code LOVEIT20 on the checkout page = $55.99. Shipping is free.
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1) The max discharge current spec for these is 20A. That's 264 watts. Most UPS units exceed that, my smallest units are 500w.
2) This may have a built-in BMS, but the charging current from a UPS has a voltage profile for charging sealed lead acid batts. In most cases the UPS won't provide a high enough voltage to charge a LFP all the way, maxing out around 13.5v when the LFP needs to be at 14.4v to be fully charged to 100% capacity.
1) The max discharge current spec for these is 20A. That's 264 watts. Most UPS units exceed that, my smallest units are 500w.
2) This may have a built-in BMS, but the charging current from a UPS has a voltage profile for charging sealed lead acid batts. In most cases the UPS won't provide a high enough voltage to charge a LFP all the way, maxing out around 13.5v when the LFP needs to be at 14.4v to be fully charged to 100% capacity.
Your right that most won't top off correctly. This may become a problem over time as many bms won't cell balance below a certain voltage. You many need to periodically manually top off if this is the case. Not charging all the way up has other benefits.. namely lowered cell degredation. Unless I'm top.balencing or calibrating, I just stop charging at about 95 percent.
You haven't seen a problem because your power load is well under the 20A limit. That limit isn't just an output concern, it may also be a safety issue if there's no internal thermal cut off. The product lists overcharging, undercharging and short circuit protection but nothing about overcurrent or thermal protection which is the far greater concern.
Your right that most won't top off correctly. This may become a problem over time as many bms won't cell balance below a certain voltage. You many need to periodically manually top off if this is the case. Not charging all the way up has other benefits.. namely lowered cell degredation. Unless I'm top.balencing or calibrating, I just stop charging at about 95 percent.
If you were hell bent on using these for a UPS power then wiring up your own external battery box where you have a bunch in parallel to exceed the current output limitation would potentially be a workable solution. But the use case being discussed here is for drop-in replacements, and this is not that.
As far as less cell degradation from undercharging goes, two things: 1) the UPS and battery BMS will both probably fail out long before the 3000+ cycle cell does and 2) your cell degradation is likely going to increase if you're overheating them by pushing the current limit.
1) under 200W like servers, laptops, routers, etc.
2) do not want to charge their batteries to 100% for longevity
Probably a majority of us uses our UPS for low power purposes <200W (like servers and routers) and not for a heater, microwave, power tool, etc. I have the CyberPower CP1500PFCLCD UPS. These are great because they're drop in replacements with benefits of lifepo4 like long life 3000 cycles, lighter 1/3 weight, not worried of charging SLA above 50%, etc.
You haven't seen a problem because your power load is well under the 20A limit. That limit isn't just an output concern, it may also be a safety issue if there's no internal thermal cut off. The product lists overcharging, undercharging and short circuit protection but nothing about overcurrent or thermal protection which is the far greater concern.
UPS units which use more than 2 batteries are well over 500w outputs, so it's just a bigger problem if you've sized your load to your UPS.
If you were hell bent on using these for a UPS power then wiring up your own external battery box where you have a bunch in parallel to exceed the current output limitation would potentially be a workable solution. But the use case being discussed here is for drop-in replacements, and this is not that.
As far as less cell degradation from undercharging goes, two things: 1) the UPS and battery BMS will both probably fail out long before the 3000+ cycle cell does and 2) your cell degradation is likely going to increase if you're overheating them by pushing the current limit.
However,most people who still buy UPS's are buying them for protecting and keeping routers/swtiches etc online- well under 200w total. SLA batteries just do not have great longevity, 2-3 years before degradation becomes an issue where either it will drop flat on its face the moment you put a load. If you did use your UPS as designed, a few full drains will result in a battery that has degraded significantly.
The C-Rate of SLA batteries is typically worse than that of lithium.
In truth, NMC batteries are in my opinion better (performance and longevity) in these applications. I've taken apart lots of backup power NMC 18650's from modems and VOIP devices. Probably 95% still tests to their mfg spec ratings. The cycle counts are extremely low in UPS's. The Linear decline in voltage also allows for better pack capacity monitoring.
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