Batboard

Hello all,

I have a few customers that have quantars that are currently connected to ups. All of the buildings that house the repeaters are generated.

To this extent, I would like to move the Quantars off of UPS and put them on the DC battery. All of the repeaters have the option, and have the battery cables tied up to the chassis not being used.

I have read some other posts about using AGM type batteries, but what should I look for as far as AH rating. I would like to keep the 100 watt units up for at least 1 hour at half power in case of generator failure, but would most likely only need to carry power loss to generator time.
In some of our locations space is premium.

I believe that all have the 24 Volt option. So I am thinking of two 12v 75 amp batteries? Any ideas, thoughts, etc. Is there an easy way to calculate what I need.

Happy Thanksgiving - Rob

Any takers on this question??

Yeah. I thought about it yesterday when you posted, but got side tracked. There was something going on. Don't recall. (grin)

I don't have my power books in front of me. You're going to need a charging system as well as a bank of batteries. You can either contact a pro power system company like Eltek to size everything to your spec, or you can roll your own. Tessco carries several products. So does Talley. The part you really have to be careful - the part that has burned my biscuits more than once - is interpreting the battery OEM discharge ratings. Read the fine print. It's supposed to be simple math, but they complicate it. Let's say you need one amp for one hour. That's one amp hour. Okay. So you buy a one amp hour battery and it doesn't last more than five minutes under load because the fine print says extended discharge periods should not draw more than 100mA continuous. Translation - you need 10 of their batteries in parallel to get one amp for one hour. There's generally fine print about the charging and maintenance characteristics too. So, drill through your Quantar maintenance manuals. Determine the full load you will be applying during a power failure. Add at least 10% additional capacity. Then size your charger and batteries accordingly.

And don't forget to consider the structural integrity of your shelter floor.

BIll,

Thanks for the reply. I cant find much in the manual. The quantar has its own intelligent battery charging circuit. I just need to figure out the quantars amp/power requirement and the fine details of the battery and their associated discharge rates? If anyone has some info or point out where I can find the power requirements for the quantar that would be awesome.

Thanks, Rob

Rob - You're welcome. There are several Quantar manuals. The info you want for current on batt revert is in one of the smaller service manuals. Or you can measure it.

Or you can WAG it.
P(out)/V(in) x 2.5(efficiency fudge factor) = I(in)
50W/24V x 2.5 = 5.2A or so. Sounds a bit low, but it might get you by. Assume 25% of that for rx (1.3A). Unless it's a busy dispatch center, assume 25% transmit time, 75% receive time meaning approx 2.3AH required. Round that up to 3AH.

If you go looking for 3AH batteries, you'll find the little things they put in alarm panels, and robot kits. Your original choice of a 75A battery was closer to the correct size. Look at this one. Rated for 12V at 75AH for wheelchair operation with 3A for 20 hours should serve you well. About 60 pounds each. You'll need two. They'll get almost a whole day of service out of these batteries which is a more realistic requirement than an hour.

http://www.batteryspace.com/sealedleada ... v75ah.aspx

Dig out your vendor catalogs. Look through the batteries available. Read the spec sheets on the batteries. Verify with the customer they want an hour of service on battery if the generator fails or if they just need enough to get past the bump of AC fail and gen start. Also figure out where you'll mount these batteries, and how you'll protect the open terminals.