Pellet Stove Battery Backup

Pellet stove battery backup is a standard feature on a few stoves, all you have to do is to provide the battery. These stoves use twelve volt motors, and when running on mains power, voltage is stepped down before entering the stove system.

The power available from a battery is not enough at the moment to run an automatic ignition system, which would be very demanding and shorten battery life, so stoves running on battery power have to be lit manually using starter gel and pellets.

Pellet stove battery backup for stoves that are designed to use mains electricity will require an inverter as well as a battery.

The Battery

Placement of the pellet stove battery backup will ideally be about six feet from the pellet stove to avoid excessive heat and to maintain a fairly short cable run. It should be placed in a vented battery box. Batteries produce hydrogen gas which is inflammable if allowed to build up.

For decorative and safety reasons, the pellet stove battery backup should live in its own cupboard, then it can't be knocked over accidentally and metallic objects can't fall across the terminals and either short the battery out or cause a fire.

The type of twelve volt battery to go for is the "Deep Cycle" or "Deep Discharge". An automotive battery becomes effectively flat when it is dis charged to fifty percent of its capacity. The other thing automotive batteries don't like is being in a partially discharged state for any length of time. They are designed to produce a lot of power for a short time, (starting the engine), and then to be returned quickly to full charge by the alternator. An automotive battery will run a pellet stove for a while in an emergency.

Deep Cycle batteries, (also known as marine batteries), are designed to produce power at a constant rate for a long period of time. Typical applications would be the 'house battery' of an RV or boat, or the batteries used to run a golf cart. They can be discharged to about eighty percent without damage.

Deep cycle batteries are constructed in three ways. Flooded, (wet), is the most common, cheapest, and will probably last the longest. Other types are 'Gel' and 'AGM' (absorbed glass mat). Although gel and agm won't leak if tipped over, they can be damaged by rapid charging and mostly can't be topped up with electrolyte. Sealed or maintenance free batteries can't be topped up either and this will shorten their life. All batteries lose electrolyte to some extent.

Power Requirement

The length of time power can be out in your area will help decide your pellet stove battery backup power requirement. If power is likely to be out for a couple of days at most, battery backup is the way to go. Longer than a couple of days and you should be considering a pellet stove generator backup system ( see link at bottom of page ), or spare batteries and a way of charging them.

The size of battery needed depends on the power requirement of your pellet stove and the length of time you want it to run. Battery capacity is measured in ampere hours, (ah). Let's take an example. An automotive battery rated at say 100 ah can be discharged 50% without damage which gives usable power of 50 ah. A deep cycle battery rated at 100 ah can be discharged by 80%, giving usable power of 80 ah which means that it is capable of giving one amp for 80 hours, two amps for 40 hours etc.

To convert watts to amps, divide watts by the mains voltage.

Battery Charging

All batteries will discharge themselves over time, even if no power is being used, so you will need some means of keeping your Pellet stove battery backup topped up.

As well as being an essential part of the system, battery charging requirements may affect the type of battery you go for. Gel batteries are very sensitive to over voltage charging and need a dedicated charger.

The size of charger you need is determined by the size of battery, and the time you need it charged up in. If you take the ampere hour rating of the battery, divide it by the ampere rating of the charger, this will give the charging time. Add 10% to the charging time to make sure that the battery is fully charged.

The best chargers are microprocessor controlled and known as 'smart chargers'. They provide a large charge initially, then top the battery up to full and maintain it in that state automatically.

Solar and wind charging are good options for power out situations, but are unlikely to keep up with the demands of the stove in small scale installations. Good for keeping the battery trickle charged though.

The Inverter

This is the device that converts twelve volts dc, (battery power), to mains voltage. There are two types - pure sine wave or modified sine wave. Mains electricity is provided in the form of alternating current, (ac) in pure sine wave form. Controllers on some pellet stoves will only work with pure sine wave current.

As with the battery, the inverter must have enough capacity to run the stove, so check the stove's power requirement. Ignore the starting requirement which will include auto ignition, just work on the running requirement and add 10% to allow for loss in conversion

To convert amps to watts, multiply amps by the mains voltage.

Stove Sentry

A dedicated pellet stove battery backup system is available from Stove Sentry.

When electricity is present the Surefire Stove Sentry charges a battery and surveys the power line. At the instant that a power failure occurs, the Surefire Stove Sentry converts the energy stored in the battery to AC power. This assures operation of the pellet stove without interruption during the absence of electricity.

When AC utility power is restored, the Surefire Stove Sentry reinstates AC utility power as the prime energy source to operate the pellet stove. Simultaneously and automatically the Surefire Stove Sentry commences the recharging of the battery, to return it to full capacity in preparation for the next power failure.

Surefire Stove Sentry is offered as an option by Harman pellet stoves, but will work equally well on other systems.

12 Volt Stoves

These pellet stoves are configured to run on twelve volt battery power as standard. When a battery is connected, it will be trickle charged until mains power goes out when the battery will automatically take over stove operation.

American Energy Systems: Magnum Baby Countryside, Winchester.
Dell Point: Europa
Sierra Products 'Easyfire': EF5001U, EF5001, EF3801, EF4001 Insert.

Thelin:
Thelin Gnome
Thelin Echo
Thelin Parlour
Thelin Tiburon

Quadrafire:
Mt Vernon AE.

Edge 60 Pellet Fireplace