Battery back up for enviro maxx

[hwdemers]

Im trying to set up a battery backup system for my pellet stove and want to see if I am figuring this out correctly.

I was thinking I want to use 12v 500ah deep cycle battery (3 in series) for a total 1500ah
at 6 amps (enviro maxx) this should give me +/- 24 hrs

T(hours)=(3*500)/(6*10*1)= 25

here is the link to the place I got my numbers from http://www.secamerica.com/pdf/Application Notes/StoveCombined.pdf


here comes the part i'm confused about

6 amps is what the service book for enviro says the max is at, but is that with the ignitor on? seams high?
or what I really want to know is, if I want to use (no more than)3 batteries to power an enviro max for 24 hours (in high/low thermostat control) what "size" batteries must i get, and will the SEC STOVE SENTRY do the trick?

 

[TimfromMA]

First off, you want the batteries in parallel NOT in series otherwise you will have 36V at the stove.

Secondly, I think you are seriously over estimating your battery needs. I use 90ah of batteries and get a good 8 hours of runtime. You say your stove draws 6a which calculates out to 720Watts. That seems incredibly high to me.

 

[TimfromMA]

According to this:

http://www.dynamitebuys.com/store/pdf/EnviroFireMaxx.pdf

The stove uses 300 watts under normal use and 450 Watts at startup.

I would base my usage calcuations on the 300 watt number since that's mostly where you'll use it.

300 watts from a 12V battery = 25 amps * 24 hours = 600ah.

To avoid damage to the batteries, you want to only use a deep cycle battery to 50% of it's rated capacity so I would go to 1200ah to get your 24hours of use.

 

[Deromax]

This is surely the maximum, with the ignitor ON. I just measured my stove. At power level 3 out of 5, it will use 0,7A for the blowers and 1,7A when the auger kicks in, once every few seconds. So maybe 1 to 1.2A average.

 

[TimfromMA]

This is surely the maximum, with the ignitor ON. I just measured my stove. At power level 3 out of 5, it will use 0,7A for the blowers and 1,7A when the auger kicks in, once every few seconds. So maybe 1 to 1.2A average.

Sounds ALOT more reasonable.

 

[Deromax]

You won't know until you purchase a Kill-a-watt or some similar measuring device! I think published specs are invented by the marketing dept in most cases!

 

[BrotherBart]

Marketing departments don't come up with electrical consumption numbers lately, or ever. The Enviro Maxx listing shows 432 watts, 3.6 amps. Listings are done for maximum current draw.

 

[TimfromMA]

Which is when the igniter is running.

 

[BrotherBart]

The ignitor in the Maxx is 400W. Enviro part# 50-1691

 

[hwdemers]

I'm just hanging back waiting for the dust to settle
So what size battery do I need for 24hrs no igniter coming on?

 

[TimfromMA]

There seems to be conflicting information on just how much current your stove actually draws. There are devices you can buy to measure this. Once you have an accurate measure of the current, use the following formula to calculate battery size:

((Stove Current) * 120) / (battery voltage) * (numbers of hours you want it to run) *2

For example if Deromax's number is correct:

(1.2 * 120) / 12 * 24 * 2 = 576ah

 

[Deromax]

Given that a 24 hrs power outage in not something which tend to happen often, I think the provision for twice the battery life in the name of protecting the batteries from complete depletion might not be needed. A battery bank that goes empty half a dozen time in its lif should survive. 576A/h of battery will cost some serious money.

imho, past a few hours of power outage, we are into generator territory, as you may want to also power the fridge, well water pump, sump pump, etc. Entry level units can be had for 250$, which is the cost of a single 160Ah deep cycle battery.

ymmv

 

[TimfromMA]

Given that a 24 hrs power outage in not something which tend to happen often, I think the provision for twice the battery life in the name of protecting the batteries from complete depletion might not be needed. A battery bank that goes empty half a dozen time in its lif should survive. 576A/h of battery will cost some serious money.

imho, past a few hours of power outage, we are into generator territory, as you may want to also power the fridge, well water pump, sump pump, etc. Entry level units can be had for 250$, which is the cost of a single 160Ah deep cycle battery.

ymmv

I disagree. As the battery depletes, deposits build up inside the cells that can actually create shorts inside rendering the battery useless. Even one time over depleting the batteries can do this.

I do agree on the incredible expense and questionable necessity of that much battery. I have a 24V system which means I need (2) 90ah batteries to get 45ah of usage. They're not cheap.

 

[batchman]

Search my "Maxx MAdventure" post as I measured my Maxx, ISTR it was ~360w. I went with a TrippLite UPS to manage shutdown and for now am planning on lugging the batteries from my diesel if I need an extended run. Be sure to remember the inverter you use won't be 100% efficient.

Cheers,
- Jeff

 

[hwdemers]

Search my "Maxx MAdventure" post as I measured my Maxx, ISTR it was ~360w. I went with a TrippLite UPS to manage shutdown and for now am planning on lugging the batteries from my diesel if I need an extended run. Be sure to remember the inverter you use won't be 100% efficient.

Cheers,
- Jeff

So what do you mean manage shutdown, you still have to manually shut it off in time correct?

 

[TimfromMA]

I have a low voltage sensor tied to a relay on the auger motor. When the voltage drops to a certain point, the relay opens cutting power to the auger. The pellets stop, feeding, the fire goes out and the stove shuts down.

 

[hwdemers]

I disagree. As the battery depletes, deposits build up inside the cells that can actually create shorts inside rendering the battery useless. Even one time over depleting the batteries can do this.

I do agree on the incredible expense and questionable necessity of that much battery. I have a 24V system which means I need (2) 90ah batteries to get 45ah of usage. They're not cheap.

While don't want to throw money away, I frequently am at the ship for 18 plus hrs and just want to keep stove going so I have time to get home and fire up the wood stove. There is no way my wife is lugging a singel stick of firewood. I have 800 to spend on this anyone have a recommendation on how to achieve my goal the best I can in v this budget

 

[hwdemers]

I have a low voltage sensor tied to a relay on the auger motor. When the voltage drops to a certain point, the relay opens cutting power to the auger. The pellets stop, feeding, the fire goes out and the stove shuts down.

Um.. why didn't I think of that, can you send a link to the one you used?

 

[TimfromMA]

How often do you lose power and how long does it usually stay out?

 

[hwdemers]

Once or twice a year, for 2 days at a time tho, big snowfalls around here

 

[hwdemers]

Should ad that this is an experiment so I can start setting up some of y these systems for customers once I understand it better

 

[TimfromMA]

One issue I had with my low voltage sensor circuit was that once the relay opened up, it was sometimes just enough of a load reduction on the batteries for the voltage to recover a bit. This recovery would reset the low voltage senor, reactivating the auger. It would flip back and forth like this repeatedly. I had to design the circuit so that once the relay opened, it would not close again regardless of the battery voltage unless I pushed a reset button.

 

[TimfromMA]

The biggest cost is going to be the battery or batteries. If you want your stove to run 24 hours on battery, you are going to need at least 600ah. These batteries produce hydrogen when re-charging so you need to keep them a good distance from the stove and possibly even put them in some sort of enclosure that is vented outside.

 

[batchman]

So what do you mean manage shutdown, you still have to manually shut it off in time correct?

My plan is to use a 24v supply on a wall outlet (not on UPS) to hold closed a relay on the thermostat line - when power drops the thermostat opens but the stove keeps running 20min on the UPS. To make things more complicated I'll use another one with a timer function to hold off re-start 1/2hr or so since re-starting on a still-running stove will overfeed pellets. And since that's not quite complicated enough I'm going to use another one to engage my A/C fan on low 1/2hr after the stove starts. That's part of why it's not done yet .

While don't want to throw money away, I frequently am at the ship for 18 plus hrs and just want to keep stove going so I have time to get home and fire up the wood stove. There is no way my wife is lugging a singel stick of firewood. I have 800 to spend on this anyone have a recommendation on how to achieve my goal the best I can in v this budget

I'm thinking a UPS with a big outboard AGM batteries could be done on that budget and avoid the Hydrogen problem Tim mentions. Be sure to get one that supports external batteries, and know what the internal voltage on the UPS is (mine is 24v) so you know how to configure batteries.

Cheers,
- Jeff

 

[TimfromMA]

My UPS sits downstairs in the room directly below the stove. I installed an outlet in the wall right next to the stove and ran a piece of romex downstairs to a empy outlet box in the wall next to the UPS. From there, I wired in a AC wall cord that plugs into the back of MY UPS. The only thing you see upstairs is an outlet while the batteries are downstairs far enough from the stove to mitigate the hydrogen problem.