12v non-automotive UPS with battery health monitoring

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OldGeek

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#303495 14-Feb-2023 14:58

Currently I have a Constant Vigil Sentry Lite unit (Sentry Lite | Battery Backup (UPS) for Fibre Internet (constantvigil.com)) that provides a 12v UPS service to my ONT and 1 router. The problem with this unit is that I have no visibility to the state of the external battery (REMCO RM12-9) and in a recent power failure there was no cutover because the battery was dead. These devices have no ability to indicate anything to do with battery charge. ONT and router are well within the power consumption specs.

I am therefore looking for a similar unit that includes battery health reporting (preferably both charging and discharging)- or at least some way of ensuring that in the event of a power failure the battery has some charge to take over. Provision for external batteries is also preferable so that I can swap out batteries to increase time coverage.

A simple Google search gave a long list of mostly automotive battery charge or monitor options.

Can anyone suggest products (preferably available from NZ-based sources)? Thanks in anticipation.

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Jase2985

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#3037367 15-Feb-2023 20:23

even most modestly priced UPS dotn do a good job of monitoring the batteries, best idea is to consider them consumables and replace them once every 3 years.

You can turn the power off when them on load and monitor the battery voltage for a couple of minutes to see how much it drops which will let you know a rough state of health.

OldGeek

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#3037384 15-Feb-2023 21:04

The Constant Vigil unit failed well within 3 years. I don't want trial-and-error but properly monitored battery health units. If necessary I will consider main-voltage UPS (some of which include this it seems).

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OldGeek.

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Jase2985

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#3037419 16-Feb-2023 05:33

did the constant vigil fail or the battery?

again most UPS do a poor job of battery monitoring, they will tell you the battery is full, it will hit a power cut and the battery will run for 2-3 mins then fail.

Some of the more expensive ones have a self test but they only go on load for 20 seconds or so then back to mains. still not great.

OldGeek

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#3037434 16-Feb-2023 07:55

Jase2985:

did the constant vigil fail or the battery?

I have put a multimeter across the battery and got no measurement on a 20v DC scale. An automotive charger registers a charging fault (ie unchargable state).

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richms

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#3037435 16-Feb-2023 08:12

IME the cheap small lead acid batteries used in UPSs need to be changed on a schedule of about 18 months to be certain that they will run when needed. I have come to the conclusion that its too expensive to maintain my UPSs when the power is so reliable here now that vector have mostly undone the decades of neglect that the old united networks and prior power board did to the north shore network.

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djtOtago

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#3037499 16-Feb-2023 11:35

Smaller AGM batteries tend to very sensitive to the Float voltage a charger applies to maintain the charge. And not all AGM batteries have the same Float voltage requirement. I have seen AGM batteries fail in 6 months if the float voltage is little as 0.2 volts higher than what the battery specifies.

Edit added.

Often smaller batteries sold as AGM are in fact SLA (Sealed lead acid) or GEL cell type batteries. These all have different charging requirements.

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pdh

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#3037562 16-Feb-2023 13:03

Perhaps a little outside the box...

Lead-acid (in any form) is not good at shelf life.

What about a decent Lithium power-tool battery - which you maintain 3-monthly by slipping it out of your existing UPS and into the appropriate power-tool system charger for a couple of hours. A 3A battery may be the biggest you can find in 12V, but it should hold charge for months - with a lifespan of 10 years.

I realise this does nothing for your in-circuit 'testability' requirement, but at least you'd be using better kit.

neb

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#3037782 16-Feb-2023 16:04

If by "health reporting" you mean "LEDs to indicate current capacity and state" then APC sell a decent LiIon 12V UPS that does this. Beware of equivalents from the Middle Kingdom where you have no idea of the quality or safety of the cells that go into them. The APC one seems to last more or less forever, I've had mine for probably about ten years with no indication of capacity loss, it held some networking gear up for six hours the last time it was needed.