DIY Raspberry Pi UPS

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neb

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#272999 29-Jul-2020 21:17

In the context of some unrelated work I recently found out that Analog Devices make a whole range of devices for UPS-style power management of low-voltage systems, e.g. the LTC4041 which is a supercap UPS controller that connects to a low-voltage input, say 5V, provides a balance charger for one or two supercaps, automatic switchover to backup, and assorted protection functions. It signals power-fail to the connected device, which then has the supercap discharge time to do a clean shutdown. A related one is the LTC4040 LiIon/LiFePo4 UPS controller, or the all-in-one LTC4110. There have been earlier threads on UPS-style setups for Raspberry Pi's and similar, it looks like these would make ideal devices for that functionality, with the downside that there's some assembly required...

timmmay

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#2531075 29-Jul-2020 21:30

My DIY solution was an SLA battery, a charger, and a car USB converter. My charger is the sentry lite UPS that runs my router.

MikeAqua

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#2533769 3-Aug-2020 14:30

timmmay:

My DIY solution was an SLA battery, a charger, and a car USB converter. My charger is the sentry lite UPS that runs my router.

What's the longevity of the system so far? Assume you have constant trickle charge?

Mike

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#2533772 3-Aug-2020 14:33

MikeAqua:
What's the longevity of the system so far? Assume you have constant trickle charge?

With a generic 7Ah battery would you even be able to measure longevity? You're connecting it to such a large reservoir of power that you could in theory charge it once at install and then leave it connected as a backup for months? years? without noticing any change if outages are relatively infrequent.

timmmay

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#2533798 3-Aug-2020 14:50

The sentry lite has worked fine for 5 years. The battery is probably due replacement soon. The 7ah is just for small outages, I have some larger batteries attached to a solar panel for if we really need more power.

MikeAqua

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#2533843 3-Aug-2020 16:22

neb:

With a generic 7Ah battery would you even be able to measure longevity? You're connecting it to such a large reservoir of power that you could in theory charge it once at install and then leave it connected as a backup for months? years? without noticing any change if outages are relatively infrequent.

I was referring to longevity of the system. I should have been clearer - dangers of teamsing and typing.

In my experience SLA batteries don't like being stored very much, so you have to keep them topped up. 5 years is really good Timmmay.

Mike

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#2533993 3-Aug-2020 19:45

The Sentry Lite is a DC UPS, constantly charging the battery, so it's always topped up. I did some testing on my 5ah alarm system SLA battery, which is meant to have a 5 year life reduced a bit from being in the ceiling. I worked out capacity dropped from 7Ah to 5.2AH in 5 years, so it'll last a few years longer. The Sentry Lite battery being in a cupboard rather than the roof space might last even longer.

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#2534499 4-Aug-2020 13:35

timmmay:

The Sentry Lite is a DC UPS, constantly charging the battery, so it's always topped up. I did some testing on my 5ah alarm system SLA battery, which is meant to have a 5 year life reduced a bit from being in the ceiling. I worked out capacity dropped from 7Ah to 5.2AH in 5 years, so it'll last a few years longer. The Sentry Lite battery being in a cupboard rather than the roof space might last even longer.

That's good. I used to use SLAs in my fishing kayas as fishfinder batteries. Had sufficient capacity to ensure they never went below 66% during a 12 hour trip. Sat them on trickle in between trips (1 -2 per week). 12 months was about how long they lasted.

Mike

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#2534562 4-Aug-2020 15:11

MikeAqua:

That's good. I used to use SLAs in my fishing kayas as fishfinder batteries. Had sufficient capacity to ensure they never went below 66% during a 12 hour trip. Sat them on trickle in between trips (1 -2 per week). 12 months was about how long they lasted.

That's not a long life given you only took them to 66%. I guess they get more actual use than mine though.