Hi all,
I've been reading a lot through these forums, and trying to give myself a crash course on what to do, what not to do, and what direction to go with this...
Firstly, I have this UPS:
www.cyberpower.com
It's a 1000VA / 900W unit that can do 'eco' mode and be line interactive, or 'online' mode and always do an AC-DC-AC cycle.
It runs off 36v (3 x 12v 7Ah SLA internal, 6 x 7Ah SLA in external battery module - BPSE36V45A) and seems to have a float voltage of 41v (measured at the EBM port).
Interestingly, it also mentions in the specifications: Maximum Charging Current (A): 1
So I'm looking to put together a battery pack that I can plug into the EBM port that I could use - and hopefully disconnect the internal SLA batteries. There's no rush on this - as the SLAs still give me ~2h runtime as is using the 3S 3P setup of internal + EBM. As such, I'd like to learn what to do to make as few mistakes as possible
As for use case, I have a wifi operated 240v switch on the main input lead that's hooked up to my electricity providers pricing data - used to cut off the mains and run a few things from battery when the price gets high and charge up again when prices become reasonable again. ATM, this rule is set to disconnect above $0.45/kWh and reconnect below that.
Problem is, the battery reading from the UPS interface is shit - and only does whole volts, and the UPS estimate of time left is horrible - meaning it can often go from 60% to 3% when things have been running for a while.
See:
It also seems to lie when the battery is 100% charged - as I can still see a higher input current when the UPS says its 100% charged.
Anyway - so I'm looking at creating a 12S LiFePo4 battery - hopefully as 1P to make things simpler - and guessing around 50-100Ah - simply because bolting cells together seems to be simpler than other methods.
I've been looking at cells like these - mainly from AliExpress due to what seems to be a lack of sellers in Australia... https://s.click.aliexpress.com/e/_AtETUM
36v at 60Ah for ~$270USD seems to be fairly reasonable - unless others know of better pricing / cells / providers.
Given that the current 9 x 7Ah SLA batteries would only give ~21Ah at best, a single pack of 60Ah LiFePo4 would still give a lot more runtime, and seemingly pretty small too.
I'm guessing I would need to use a BMS for this - even though the UPS would output (up to) 41v @ 1A for charging. And yeah, I'm aware that this setup would take *ages* to fully charge - but I'm ok with that - as its really only going to be the same rate that it'd charge the SLAs do after use. I'm more after the cycle count than anything else.
It seems like the Daly BMS stuff is popular? I figure if I can grab further details via the USB port, I could use that instead of the woeful information on battery state given by the UPS... Given that its a max of 900W, a 30A BMS would be enough, but I'd likely upsize it for lesser load...
What is there that I should know?
Am I being sane?
What will bite me in the backside?
Am I even looking at the best form factor / type for my use case?
Should I just use the 36v ebike batteries? If so, any issues of using them in parallel?
I've been reading a lot through these forums, and trying to give myself a crash course on what to do, what not to do, and what direction to go with this...
Firstly, I have this UPS:
OLS1000E - Smart App UPS Systems | CyberPower
CyberPower OLS1000E is a high-performance UPS featuring online double-conversion topology, which provides seamless Pure Sine Wave power for mission-critical devices such as NAS and servers, DVRs/surveillance systems, transportation and infrastructure, and emergency systems. It’s typically...
www.cyberpower.com
It's a 1000VA / 900W unit that can do 'eco' mode and be line interactive, or 'online' mode and always do an AC-DC-AC cycle.
It runs off 36v (3 x 12v 7Ah SLA internal, 6 x 7Ah SLA in external battery module - BPSE36V45A) and seems to have a float voltage of 41v (measured at the EBM port).
Interestingly, it also mentions in the specifications: Maximum Charging Current (A): 1
So I'm looking to put together a battery pack that I can plug into the EBM port that I could use - and hopefully disconnect the internal SLA batteries. There's no rush on this - as the SLAs still give me ~2h runtime as is using the 3S 3P setup of internal + EBM. As such, I'd like to learn what to do to make as few mistakes as possible
As for use case, I have a wifi operated 240v switch on the main input lead that's hooked up to my electricity providers pricing data - used to cut off the mains and run a few things from battery when the price gets high and charge up again when prices become reasonable again. ATM, this rule is set to disconnect above $0.45/kWh and reconnect below that.
Problem is, the battery reading from the UPS interface is shit - and only does whole volts, and the UPS estimate of time left is horrible - meaning it can often go from 60% to 3% when things have been running for a while.
See:
It also seems to lie when the battery is 100% charged - as I can still see a higher input current when the UPS says its 100% charged.
Anyway - so I'm looking at creating a 12S LiFePo4 battery - hopefully as 1P to make things simpler - and guessing around 50-100Ah - simply because bolting cells together seems to be simpler than other methods.
I've been looking at cells like these - mainly from AliExpress due to what seems to be a lack of sellers in Australia... https://s.click.aliexpress.com/e/_AtETUM
36v at 60Ah for ~$270USD seems to be fairly reasonable - unless others know of better pricing / cells / providers.
Given that the current 9 x 7Ah SLA batteries would only give ~21Ah at best, a single pack of 60Ah LiFePo4 would still give a lot more runtime, and seemingly pretty small too.
I'm guessing I would need to use a BMS for this - even though the UPS would output (up to) 41v @ 1A for charging. And yeah, I'm aware that this setup would take *ages* to fully charge - but I'm ok with that - as its really only going to be the same rate that it'd charge the SLAs do after use. I'm more after the cycle count than anything else.
It seems like the Daly BMS stuff is popular? I figure if I can grab further details via the USB port, I could use that instead of the woeful information on battery state given by the UPS... Given that its a max of 900W, a 30A BMS would be enough, but I'd likely upsize it for lesser load...
What is there that I should know?
Am I being sane?
What will bite me in the backside?
Am I even looking at the best form factor / type for my use case?
Should I just use the 36v ebike batteries? If so, any issues of using them in parallel?
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