Lithium Battery for UPS

[OffGridInTheCity]

>What did you use to crimp them?
I soldered mine - but they are hollow tubes closed on one end so any kind of tube crimper should work.


[size=small]>How did you terminate your cables to your battery pack?[/size]
[size=small]Soldered them to the buss bar.[/size]

No ifs or buts what so ever? Just straight high powered soldering iron?

Sure - we're talking 60amps absolute max for APC 15000. 8AWG wire/busbars - short work for 100w soldering iron
But I'm not against crimping for the Anderson connectors

 

[Tictac]

Anyone ever try the none soldier builds that let you change individual cells and include bms with case for a direct 12v replacement for a sla 7ah lead batteries?

 

[daromer]

Build a proper pack. You dont need to change cells that often that its worth it

 

[Tictac]

But if I can't spot weld or want to avoid soldering will they work properly?

 

[sainirahulk17]

I could be wrong on the one you have there, but most of those cheaper units are not very configurable. Usually the "smart" portion of the UPS means they are closer to a pure sine wave, and they are able to trigger a little better/faster on low/high line voltage than the other non-smart units

 

[Overmind]

I have a successful build so far of 2P4S for a 12-Volt Mustek 848VA.

Everything works fine, soldering was done only on main wires since the actual cells had screws fused already and they were easy to put together.

 

[Tictac]

Build a proper pack. You dont need to change cells that often that its worth it

I want to be able to change the cells easy, I don't want to have to solder or spot-weld. I'm using cells pulled from laptop and tool packs not new cells.

 

[LithiumSolar]

I have a successful build so far of 2P4S for a 12-Volt Mustek 848VA.

Everything works fine, soldering was done only on main wires since the actual cells had screws fused already and they were easy to put together.

Are you using LiFePO4 for that? Or NMC?

 

[Overmind]

Yes, I started to used them for UPS units instead of lead-acid. The extra capacity and most likely extra life time is what I want, not the raw discharge rate of lead-acid.

 

[kochikame]

HI all,
If I use a BMS with overcharging protection , even if there is continuous voltage at the input , can we say the batteries are in safe condition? Are they have a short life?
I am planning to change an acid battery ups with a lithim pack with bms.
Thanks

 

[OffGridInTheCity]

HI all,
If I use a BMS with overcharging protection , even if there is continuous voltage at the input , can we say the batteries are in safe condition? Are they have a short life?
I am planning to change an acid battery ups with a lithim pack with bms.
Thanks

If I'm understanding.... Typically, a UPS doesn't use the batteries unless there's a power outage - it simply keeps them at a set voltage, ready for an emergency. For lithium-ion or LifePO4 this will not harm them at all - they should forever. There's no problem with a BMS - in fact its recommended

 

[Bubba]

If I'm understanding.... Typically, a UPS doesn't use the batteries unless there's a power outage - it simply keeps them at a set voltage, ready for an emergency. For lithium-ion or LifePO4 this will not harm them at all - they should forever. There's no problem with a BMS - in fact its recommended

I have a different view of UPS design. My view is that they are constantly inverting and charging, that way a power input interruption just interrupts the charge circuit.
ie. brown out protection. In the event of a brownout, incoming charge drops and is interrupted, however the inverter still draws from the cells providing a constant uninterrupted output until proper charge (input brownout condition) is rectified.

I don't believe there is live switching or triggering as previously mentioned. I believe the clicking heard is the disconnect of the charge circuit.

I can see how it is said the batteries are not use, because there is sufficient charge current to meet the needs of the inverter.

Is this not correct?

 

[Korishan]

There are Stand-By/Line-Interactive UPS, and Online UPS.
The Stand-By/LI UPS charges and keeps the battery charged up, and in the event of a power failure will flip over to Battery mode usually in <25ms
The Online UPS will have two separate pieces of circuitry whereby it will charge the battery. Then it inverts from the battery to AC output. There is no switching involved as it is 'always' running on DC power. The Battery is maintained at full charge during this process. In the event of a power failure, there is no flipping over to DC, it's already there. These are far more expensive units.

Pros/Cons:
Stand-By/LI - Cheaper, lighter, smaller footprint. Possible for surges/brownout to happen during switching. Lights could easily been seen dimming on some units.
Online - More expensive, heavier, larger footprint. No brownouts/surges. All power is filtered even from the grid so no noise or power ripple on the load side

Understanding UPS Topologies: Online vs. Line-interactive vs. Standby

UPS Technologies When choosing a UPS (Uninterruptible Power Supply) to protect your electronic equipment there are 3 main UPS technologies on the market today. The standby UPS is a low cost option that will protect you from power failure, sags and surges, while an online UPS offers total power...

shop.toromontpowersystems.com

 

[OffGridInTheCity]

And in either case.... the battery is not discharging/charging to any depth and should have a very long life. In the 'always running on DC power' case - the battery is not being depleted 'for a while' (unless there's a power outage) and then recharged - its simply sitting in an active current stream.