Battery backup plus portable inverter generator

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rhanauer

Member
Apr 18, 2019
23
Oxford, MA
Hi, all! I have a Harman Accentra 52i-TC insert, and my only other heating is electric/mini-splits. Like many people, I'm worried about the potential for increased frequency/duration of power outages, and abrupt power loss to the stove with its risk of smoke infiltration into the house. I've seen lots of discussion here (and elsewhere online) about backup systems such as batteries, UPS's, and generators. I already have an old Surefire Stove Sentry 502 battery/inverter system which was installed for use with a Whitfield Advantage stove and is now connected to the Harman. (BTW I'm not clear how this differs from a high output UPS.) This has worked fine after replacing the marine battery, and should run the stove for a few hours, especially if I set it to constant burn/ignitor off mode. I'm looking to buy a 2000-2500W portable inverter generator to extend the stove backup time, and to have to ability to power my fridge, laptop, and some LED lights. My question is this: after firing up the inverter generator, could I just plug the Stove Sentry into it? This seems simpler than plugging the stove into the generator, and would recharge the backup battery too so it's topped off when I need it again (like when the generator has to be refueled). Wondering if anyone has tried this or knows a reason it wouldn't work. Thanks!
 
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velvetfoot

Minister of Fire
Dec 5, 2005
10,176
Sand Lake, NY
I don't see why this wouldn't work, but you could simulate this by letting the inverter run the stove for a while (the time it would take for you to break out your gennie), and then plug the setup into an outlet supplied by utility power and see what happens. You should take a look at the inverter nameplate, but I doubt it'll consume more than the 2000 watts of the proposed generator. This is just me talking-I'm not qualified or anything.

Also, how is your insert vented? Up the existing chimney in a liner? You'd think it'd have plenty of draft.
 
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Montecarlossfan

Burning Hunk
Jan 1, 2019
135
Connecticut
I have a 52i insert and i could unplug and it will not get smoke in the house even before the outside air intake,, as for plugging the backup into the generator, if the battery is low it may pull quite a bit of current to charge at first, it should be fine though. You may need to change settings on your stove for it to continue to run on non pure sine wave power as well.
 
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rhanauer

Member
Apr 18, 2019
23
Oxford, MA
I don't see why this wouldn't work, but you could simulate this by letting the inverter run the stove for a while (the time it would take for you to break out your gennie), and then plug the setup into an outlet supplied by utility power and see what happens. You should take a look at the inverter nameplate, but I doubt it'll consume more than the 2000 watts of the proposed generator. This is just me talking-I'm not qualified or anything.

Also, how is your insert vented? Up the existing chimney in a liner? You'd think it'd have plenty of draft.
It is vented up the chimney with a ss liner, but pellet stoves are supposed to be shut down under power so the exhaust fan continues removing smoke until combustion stops (i.e. burnpot temp is below a certain threshold). Without the fan the smoldering pellets fill the stove with smoke which can leak out. I think by design there isn't a lot unforced draft through the stove. This may increase efficiency by allowing as much heat as possible to go to the heat exchanger and be blown into the room by the convection fan.
 

rhanauer

Member
Apr 18, 2019
23
Oxford, MA
I have a 52i insert and i could unplug and it will not get smoke in the house even before the outside air intake,, as for plugging the backup into the generator, if the battery is low it may pull quite a bit of current to charge at first, it should be fine though. You may need to change settings on your stove for it to continue to run on non pure sine wave power as well.
Thanks! Yes, I'll have to see how much wattage the Stove Sentry draws during charge mode. I'd only use an inverter generator -- the ones I see for sale are supposed to put out clean power (<3%THD).
 

gfreek

Minister of Fire
Nov 5, 2010
1,561
WNYS
Have you tried to run your Accentra on the Stove Sentry 502 ? Quick web search, looks like the 502 draws up to 5 amps, 600 watts, the 512 draws up to 5.5 amps, 660 watts.. If it does work ok for the stove then you can seamlessly unplug the Stove Sentry from the wall and plug it into the generator. That's what I do with my Cyberpower backup.. Specs for 512:
 
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Ashful

Minister of Fire
Mar 7, 2012
16,358
Philadelphia
Yea, this would work fine. You should be able to find the specifications for your particular UPS, but most draw only 20W or thereabouts, in addition to the load, in order to charge the UPS battery. Remember, lead acid battery recharge times are very long compared to what you’ve become used to with your lithium ion cell phone batteries.
 
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rhanauer

Member
Apr 18, 2019
23
Oxford, MA
Have you tried to run your Accentra on the Stove Sentry 502 ? Quick web search, looks like the 502 draws up to 5 amps, 600 watts, the 512 draws up to 5.5 amps, 660 watts.. If it does work ok for the stove then you can seamlessly unplug the Stove Sentry from the wall and plug it into the generator. That's what I do with my Cyberpower backup.. Specs for 512:
Yes, the 502 has kicked in and run the Accentra for short outages (in a longer outage I'd shut off the ignitor). My Accentra is rated at 3.5A starting and 2.5A running at 120V (420W run/330W start). My fridge specs seem to show that it draws 816W max including defrost cycle and icemaker (and presumably including compressor startup), but the icemaker is shut off which subtracts 235W, so I believe I need about 580W gennie power for it. If the Stove Sentry uses 600W when charging the battery, I'll need a minimum of 2020W gennie power. I'm looking at a Champion 2500W peak dual fuel inverter generator, which should suffice.
 

johneh

Minister of Fire
Dec 19, 2009
4,073
Eastern Ontario
Peak watts are different than running watts
2500 peak is most likely 2000 running
and what if you want your TV or a radio maybe a light to read by
just my nickels worth.
 
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rhanauer

Member
Apr 18, 2019
23
Oxford, MA
Peak watts are different than running watts
2500 peak is most likely 2000 running
and what if you want your TV or a radio maybe a light to read by
just my nickels worth.
Yeah a little more wattage would be nice but I really like the ultralight closed frame models for portability and fuel efficiency. I think I'll have some extra capacity once the backup battery is charged, since at that point I think the Stove Sentry will just pass through power to the Accentra without consuming any itself.
 

Ashful

Minister of Fire
Mar 7, 2012
16,358
Philadelphia
I think I'll have some extra capacity once the backup battery is charged, since at that point I think the Stove Sentry will just pass through power to the Accentra without consuming any itself.
I'm not following you. I am not familiar with the particulars of the Stove Sentry, but assuming it operates like any other UPS, the battery is outside the loop until input voltage drops below threshold. In other words, the Accentra will be running 100% off the generator, as will be the battery charging circuit in the Stove Sentry, until the generator fails or sags.
 

Montecarlossfan

Burning Hunk
Jan 1, 2019
135
Connecticut
I'm not following you. I am not familiar with the particulars of the Stove Sentry, but assuming it operates like any other UPS, the battery is outside the loop until input voltage drops below threshold. In other words, the Accentra will be running 100% off the generator, as will be the battery charging circuit in the Stove Sentry, until the generator fails or sags.
A Ups draws current to charge the battery , I believe he is getting at the fact that once the battery is full it no longer is adding to the load, for example I have a tripp lite unit and when it kicks back to line power after using the battery a bit, it spikes a few hundred watts and tapers as the battery fills, of course on this unit I can limit that if I chose to do so.
 
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Ashful

Minister of Fire
Mar 7, 2012
16,358
Philadelphia
A Ups draws current to charge the battery , I believe he is getting at the fact that once the battery is full it no longer is adding to the load, for example I have a tripp lite unit and when it kicks back to line power after using the battery a bit, it spikes a few hundred watts and tapers as the battery fills, of course on this unit I can limit that if I chose to do so.
Ahh... I follow him now. Normal consumer-grade UPS systems only pull a few tens of watts during recharge, eg. 16 watts for APC Back-UPS Pro 1500 S, which is at the top of the range for what most would consider "consumer grade". Enterprise-level UPS's will draw a few hundred watts, eg. APC Smart-UPS 2200, which is designed to carry a large server up to 4 hours, but these are usually $2k/ea type pricing.

The Stove Sentry tech spec's (I found model 512, not model 502) list a peak charging circuit output of 180 watts, which is higher than I'd have expected. With assumed power supply efficiency (eg. > 95%), something close to 200 watts might be a safe assumption. I also believe this would only be brief, on a completely dead battery, and tapering pretty quickly to a much lower value.
 
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rhanauer

Member
Apr 18, 2019
23
Oxford, MA
Ahh... I follow him now. Normal consumer-grade UPS systems only pull a few tens of watts during recharge, eg. 16 watts for APC Back-UPS Pro 1500 S, which is at the top of the range for what most would consider "consumer grade". Enterprise-level UPS's will draw a few hundred watts, eg. APC Smart-UPS 2200, which is designed to carry a large server up to 4 hours, but these are usually $2k/ea type pricing.

The Stove Sentry tech spec's (I found model 512, not model 502) list a peak charging circuit output of 180 watts, which is higher than I'd have expected. With assumed power supply efficiency (eg. > 95%), something close to 200 watts might be a safe assumption. I also believe this would only be brief, on a completely dead battery, and tapering pretty quickly to a much lower value.
Thanks, guys. 180W is about 1.5 amps, which is basically a trickle charge. That would be a small (and temporary) extra load on the gennie I'm looking at buying.
 

Ashful

Minister of Fire
Mar 7, 2012
16,358
Philadelphia
Thanks, guys. 180W is about 1.5 amps, which is basically a trickle charge. That would be a small (and temporary) extra load on the gennie I'm looking at buying.
Nope. 180 watts is 15 amps at 12 volts, not a trickle at all. Charger amperage is usually measured on battery side of circuit.
 

gfreek

Minister of Fire
Nov 5, 2010
1,561
WNYS
OK but its still 180W draw off the gennie, no?
Lets not confuse charging current amps, and supply line 120V input amps or draw,..and battery input current from the battery while in backup mode. Remember this Volts X Amps = Watts

Model SF 512

Normal model Operation

(Supplying Line Power)
Input Voltage Range 100-128 VAC
Input Current 5.5 A
Charging Current (max.) 12A
Recharge Time (max.) 13 Hours
(FOR 90 A-HR. BATTERY Fully Discharged)

Back Up Mode Operation
(Supplying Battery Power)
Maximum Back Up Power 550 Watts
Maximum Input Current 55 A
 
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Ashful

Minister of Fire
Mar 7, 2012
16,358
Philadelphia
OK but its still 180W draw off the gennie, no?
Yes. It will peak around 180 watts to re-charge a completely dead battery, and then likely taper off quickly as the battery charges. If you've ever owned a typical 10A car battery charger, you have seen this behavior. It starts off around 8 - 12 amps on a dead battery, quickly tapers to 5A, and then slowly tapers down to ~2A. From the little information given, I'd expect similar behavior from this unit, with load on the genny around 190 watts (180 watts minus efficiency of charger itself) when the battery is close to dead, tapering to 90 watts after several tens of minutes, and then likely stabilizing around 25 watts.
 
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