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  1. #1
    Automated Home Jr Member
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    Default Batteries for Evohome

    Exciting thread topic alert!

    Very occasional poster here. Infrequent lurker.

    As the weather is starting to turn, I thought I'd do a pre-Winter shakedown of my system and fire it up for the first time since March.

    All was well, but I discovered that something didn't shut down properly.

    Tracked down my issue to a duff set of batteries.

    My question to you all is this:

    what batteries do you use in your rads?

    I'd been replacing mine every year with a set of Costco own brand.

    Has anyone given Enerloops a try?

    I'd never heard of them until recently, but the fact that they don't leak seems like it could prevent having to buy a new rad "thing" (Mine are HR80, and I don't know the correct lingo for the updated ones!)

    eric

  2. #2
    Automated Home Legend paulockenden's Avatar
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    Energizer Lithium here. I buy them in bulk - still expensive, but about 1/3 the cost of buying in the supermarket.

    Last ages, but more importantly they don't leak. Just remember to set the parameter in the menus.

    Enerloops are rechargeable. These ones I use aren't. Rechargeable AAs don't have such good capacity as non-rechargeables.

  3. #3
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    Can you help me find the setting in the Menus?

    Is that in the Installer Menu?

    Thanks for the tip. I'd not heard of those batteries before.

  4. #4
    Automated Home Legend paulockenden's Avatar
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    The menus in the HR92 itself. I think it’s parameter 9. Maybe the HR80 doesn’t have this setting.

    P.

  5. #5
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    Rechargeables (even good ones like Enerloops) have less capacity than a good quality Alkaline battery. Given how little Alkalines last (it seems like some rooms last me only around a year), I've avoided using rechargeables (even though I have a tonne of them) as I imagine I would have to swap them more frequently. I think Paul's use of Lithium is the ideal, but I haven't worked out the cost (I still have a few Alkalines left).

  6. #6
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    I just buy a bulk pack of 40 decent brand alkalines online (which costs pennies per cell compared to smaller packs from ASDA etc) to keep on hand, which I think ironically Paul originally linked to last year.

    As soon as a zone starts complaining about low batteries, rather than trying to stretch out another months worth of use (which is about how long it will last once it starts complaining intermittently) I just replace them then and there, job done in about 2 minutes. I tension the battery contacts while I'm at it as they have inevitably gone soft since the last battery change leading to a loose connection.

    I don't bother to replace all batteries during the summer etc due to the waste that would cause - different rooms use their batteries at very different rates. So I just wait for them to complain then change them immediately.

    It will be interesting to see how long they last now - after installing Valencia valves I've concluded I need to run all HR92's in Stroke 1 mode for optimal performance, which theoretically uses the batteries quicker. However a number of my zones were already in Stroke 1 mode with the old valves and I'm pretty sure none of my zones has lasted less than 18 months despite this, although I don't actually keep a log of when individual rooms were changed. (Maybe I should!)

    If they last 18 months I'm happy with that.
    Last edited by DBMandrake; 28th September 2018 at 11:13 AM.

  7. #7
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    I wonder if you could somehow use a thermoelectric generator to recharge batteries, although I guess the amount of power they output would be too low.

  8. #8
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    Lovely idea - slap a TEG on the radiator and keep the batteries charged. Only problem is what do you do on a cold day when the batteries are flat - you need a hot radiator to open the valve - but you can't get heat unless you can open the valve and there is no electricity...

  9. #9
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    Quote Originally Posted by Old_Codger View Post
    Lovely idea - slap a TEG on the radiator and keep the batteries charged. Only problem is what do you do on a cold day when the batteries are flat - you need a hot radiator to open the valve - but you can't get heat unless you can open the valve and there is no electricity...
    Obviously it would charge some rechargeable batteries with several months worth of battery life... such as the NiMH that are already supported by the HR92...

    As long as the average power supplied by the peltier device was greater than the average power draw of the HR92 it would work. And if it's <2.6mA that is not much, even for a peltier device. And with all that hot surface available I don't see why it wouldn't work.

    Two problems though:

    1) Many radiators don't have a sufficiently large flat area to adhere a peltier device to, at least on the rear side, due to all the bumps and fins and you wouldn't want it on the front for appearance reasons.

    2) The major problem though is what do you do with the cool side of the peltier device ? To generate power you need a heat sink to cool the cool side. Often that literally is just a stuck on heatsink. If the device was attached to the rear of a radiator in the gap to the wall this heatsink would have great difficulty in attaining a significantly lower temperature than the radiator side of the device - thus no power generated, as only a difference in temperature generates power.

    On the front side of a radiator it could radiate IR into the room to cool itself so it would work a bit better but still be an eye sore. So in theory it could work but I suspect heatsinking of the cool side is the challenge, aside from adding cables and some gizmo stuck to your radiator. In the end changing batteries every 2 years is a lot easier!

    A perhaps easier approach would be a very small solar panel. They will produce some output with indoor lighting and will receive some indirect daylight as well. This could be enough to average over 2.6mA but might still be an eye sore.

  10. #10
    Automated Home Legend paulockenden's Avatar
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    Seems like a lot of hassle (and additional ugliness) when changing a couple of AAs every two years is hardly a major chore or expense.

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