Central heating and battery controls.

I had a thermostat which should show a battery icon to tell you when they need changing, however before it lit the icon, the battery would be too low to work the relay, cure was easy, I would swap cells in September each year regardless of icon.

However now I have a lot more devices that need batteries, there are 18 x AA cells in my central heating, all used as pairs, and today I finally got the last bits done to get central heating up to scratch, and realised the TRV head was not working, again the battery report said battery was OK.

My stock is old so not sure how good new batteries are, and it takes some time to get a report, it says "Battery Voltage: 2.82812V (Reported 3 days ago)" so since swapped them today, don't know voltage, but they seem to be working OK now.

The instructions say "Red flashes once every 5 seconds means dead battery needs replacing" this did not happen, it also says "Check the battery voltage level(nominally 3.1V)" don't think I have ever seen it reported so high. When red flashing it says "At this point, the eTRV’s stem will automatically retract so heating will not be controlled." also it says "Do not use rechargeable batteries." and the battery life should be 1.5 years.

Don't know if because using in central heating device but it seems in spite of having low and dead battery warning they actually fail first. The stem was not fully retracted so it seems the device had not identified the battery as being dead. And neither the twin flash, or single flash (battery low or battery dead) actually happened. It says use alkaline batteries but last set were Duracell Alkaline as did not want them to leak.

So is it the devices which don't report when battery discharged, or are the batteries doing some think which is foxing the devices software? Pressing the built in button on the battery and it showed nothing, volt meter 1.462 volt the replacement was 1.582 volt with same meter.

I have been having problems with the Energenie TRV heads, set to follow Nest, but not actually following Nest when set by time or PC but did follow when set with Phone. As to if this was related to voltage I don't know.

I suspect it's down to the very low usage, but wonder if others have problems with batteries failing but not being reported as failed?

ericmark said:

It says use alkaline batteries but last set were Duracell Alkaline as did not want them to leak.

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You must be joking. Duracells are notorious for leaking. Cheap Chinese batteries seem to be better in this respect.

I love Ericmark’s ability to put his point across in such a succinct fashion.

Nicad AA cell will only be around 1.2v fully charged iirc, probably why they don't recommend them.

It all depends when the system samples the voltage, in an ideal world it would be under load, a battery can have good float voltage but fail drastically when asked to drive a load.

ericmark said:

So is it the devices which don't report when battery discharged, or are the batteries doing some think which is foxing the devices software? Pressing the built in button on the battery and it showed nothing, volt meter 1.462 volt the replacement was 1.582 volt with same meter.

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You cannot check the voltage of a cell with an high impedance meter, they need a load applied to get a sensible value.

Most battery warnings on equipment tend to not work well, or not give much warning, but are you sure the manufacturer specifies alkaline rather than a zinc/carbon cell? They have slightly different voltage curves, I suspect the alkaline curve to complete failure is steeper than zinc/carbon, so less warning time to failure.

The software allows one to select time, and which days to sample voltage. So unlikely to be under load.

The instructions say

insert new high-quality AA alkaline batteries.

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battery says

made in Belgium Alkaline

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it was more luck than good judgement, but had fitted Alkaline.

Now they have Zinc Chloride fitted as they were all I had in stock.

ericmark said:

The software allows one to select time, and which days to sample voltage. So unlikely to be under load.

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I don't follow the point you are trying to make with that?

At 21:04 every day the software requests the voltage, the motor runs to adjust water flow for around 15 seconds a time, maybe 20 times a day, it is highly unlikely the voltage is sampled while motor is running.

However the twin flash (battery low) or single flash (battery depleted) the voltage is likely sampled under load, but neither happened.

I have an on going problem, and I want to find out why the TRV is not following the thermostat, I want to rule out the batteries.

ericmark said:

I have an on going problem, and I want to find out why the TRV is not following the thermostat, I want to rule out the batteries.

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Could you not use a 3v wall wart or similar to supply the TRV as a temporary test?

I am undecided as to using follow command or not, the idea of simply turning dial on thermostat seems good, however if the TRV does not follow down there is no problem, but if it does not follow up, then boiler running or at least cycling, and pump running but the TRV is not open, since pump on return not feed the idea of a by-pass valve does not work, so could be left with a pump cavitating. No problem with boiler as DHW is thermo syphon with no motorised valve. But could be a problem with pump.

I think with 10 TRV's the chance that all are closed is slim, and with a schedule programmed into each valve they should all change together anyway, it is annoying to think I have spent around £45 each for the 4 wifi TRV heads, where I could have used the £15 TRV heads used up stairs which are also programmable and unlike the expensive heads I can alter manually, don't need to find phone, spin the dial until temperature wanted shows then press dial for fast warm up.

The removed batteries have a built in power check, it shows batteries as full. So now think it's either Energenie or Nest software letting me down.