The Siren Board

Is this the first attempt at a battery backup ThunderBolt?

SIRENMAN wrote: you would need 18 batteries to power the inverter.

You are confusing voltage and power.

The batteries cannot power the Thunderbolt motor directly, regardless of how many you add together, bcause they privide direct current and the siren motor needs alternating current. The job of the inverter is to convert the DC power from the batteries into AC for the siren.

The system will work as long as the available DC power input (which is voltage times current), multiplied by the inverter efficiency (which is typically better than 95%) is greater than or equal to the power required by the load.

Don't some sirens have Ac and dc motors?

I do not think I am confused. Look at the link you posted. It calls for 205 to 385 DC volts as an input. How do you propose to accomplish this.

SIRENMAN wrote:I do not think I am confused. Look at the link you posted. It calls for 205 to 385 DC volts as an input. How do you propose to accomplish this.

Sorry, now I understand.

The link I posted was the first thing I came across, and was meant to show that inverter products in the 15-20 kW range could fit on a utility pole in a box close to the size pictured.

That inverter is designed for the solar photovoltaic market. In that industry the solar panels are typically wired in series for higher voltages to minimize wiring losses. DC input voltages on the order of 200-400V combined with a comparatively low current can supply input power without having to resort to very large diameter conductors, although the same power could be achieved with a lower DC voltage at a higher current.

Please accept my apologies for the confusion. I was in a hurry and should have looked for a link to a more applicable inverter.

landmobile wrote:

SIRENMAN wrote:I do not think I am confused. Look at the link you posted. It calls for 205 to 385 DC volts as an input. How do you propose to accomplish this.

Sorry, now I understand.

The link I posted was the first thing I came across, and was meant to show that inverter products in the 15-20 kW range could fit on a utility pole in a box close to the size pictured.

That inverter is designed for the solar photovoltaic market. In that industry the solar panels are typically wired in series for higher voltages to minimize wiring losses. DC input voltages on the order of 200-400V combined with a comparatively low current can supply input power without having to resort to very large diameter conductors, although the same power could be achieved with a lower DC voltage at a higher current.

Please accept my apologies for the confusion. I was in a hurry and should have looked for a link to a more applicable inverter.

This appears to be the same thing we have done with several of our customers in the past with older one-way equipment. I'm assuming this customer has upgraded to a 2-way status reporting system, and are planning to eventually go to a battery back up system. They can upgrade to 2-way controllers with DC cabinets, operating as an AC only siren, then when they are ready to upgrade the sirens, only the head needs to be replaced and add batteries.

FederalSignalGuy wrote:This appears to be the same thing we have done with several of our customers in the past with older one-way equipment. I'm assuming this customer has upgraded to a 2-way status reporting system, and are planning to eventually go to a battery back up system. They can upgrade to 2-way controllers with DC cabinets, operating as an AC only siren, then when they are ready to upgrade the sirens, only the head needs to be replaced and add batteries.

There are no plans to remove the Thunderbolts in the system.


Well now I really need to ask him. I will call him later this week for the explanation. I do know the Thunderbolt a Juniper Hills does not have these batteries, but the others are all building-mounted, so I can't be sure about those.

Maybe they replaced the blower motor with something that could be run off batteries?