wanted: system planner for quantar backup power

[batdude]

i know it exists.

i would like to see the factory recommended backup power setup.

right now i am looking at 4 100amp AGM batteries running in parallel.


the honking fat quantar book is worthless. it doesn't even show whether the input power is 12vdc or 24vdc.




HELP!


doug

[xmo]

Here is what the Quantar planner has to say:

Quantar
• Battery Charger and Emergency Reverting (X30) * = Provides an adjustable, regulated power supply to trickle charge a battery, and automatically reverts to battery operation upon loss of primary power. This option is not recommended in situations of frequent AC power interruptions, due to the limited recharge capability of the power supply.

External storage batteries attach to the station through connector location 25 on the backplane bracket. Includes a low voltage disconnect feature, which disconnects at 10.5V for 12V batteries, and 21V for 24V batteries. Requires only 12V batteries for 20 and 25 watt models and only 24V batteries for 100, 110 and 125 watt models.

*Note: Output power may be reduced up to 3dB in the battery revert mode to conserve battery life. Full rated RF power is only available for terminal voltages of 13.5 to 15V (12 VDC: X30 option) and 27 to 30V (24 VDC: X30 option) at the station DC input connector.

Quantro
• Battery Charger and Emergency Reverting (C28) = Provides an adjustable, regulated power supply to maintain battery charge, and automatically reverts to battery operation upon loss of primary power. External storage batteries attach to the station through the battery connector located on the junction panel at the rear of the station. Includes low voltage disconnect, which disconnects the battery when voltage drops to 10.75V to conserve the battery's life. This option is not available on 350 watt models.

[batdude]

so i guess my 125w vhf needs 24vdc... would be nice if that was written in english in the manual


ok




d

[RKG]

The Quantar backup system has some deficiencies. For a better system, do an archive search on "Heart Interface" and take a look at the system described there. This will run a 100W Quantar for 2-10 hours (depending on duty cycle); the radio won't reboot on loss of offsite power, and there is no power reduction. The batteries will be properly charged once OOP is restored, and they can sit on the system for years without overcooking.

If you go the Q route, the way to get 24VDC is to hook two 12VDC batteries in series. For more capacity, hook two sets of 24VDC batteries (each consisting of two 12VDC batteries in series) in parallel. Be sure to fuse the batteries with a Class T fuse or better between the common positive output and the Q harness. Also not a bad idea to insert a disconnect switch of adequate rating between the fuse and the harness.

[batdude]

one of the things to remember that's particular to my installation is that it is just not accessible on a day-to-day basis.

300ft above traffic on a bridge (think post 9/11 here) is just not an easy feat to get access to.

the heart interface thread i have read thoroughly - but alas, i am also a believer that moto wouldn't have a crap battery backup system either.

however, cooking the batteries (they may not be checked for a year or more) is not an option either!



doug

[RKG]

If you're not going to check the batteries for up to a year, be sure to use gel cells, not flooded cells; electrolyte on latter has to be checked at least monthly.

The trouble with most built-in revert systems is that they use "trickle" chargers when the batteries are full; that is to say, current regulated chargers set for a small current level. The trouble with that is that such chargers will allow the battery terminal voltage to get above 15 VDC (for 12VDC batteries) -- which they have to do in order to maintain their set-point current output -- and this will quickly kill the batteries.

A true float charger will be voltage regulated at a voltage well below the gassing point (after the battery is charged, that is); on the order of 13.4 (plus or minus for ambient temperature) for flooded cells and 13.65 (+/-) for gel cells. Batteries can sit on such a charger for years without damage. I am not aware of any radio-supplied charger, including that of the Quantar, that is a true float charger in the post-charge mode.

[ASTROMODAT]

batdude, it is infinitely better to use multiple batteries in series to acheieve a given AHr rating, as opposed to parallel setups. So, instead of paralleling 4, 100 AHr 24 V batteries, it would be much better to place in series 4 qty 6 V batteries, each rated at 400 AHr. There is not room here in this post to go into the details, but basically paralleling batteries whose impedances are even slightly different causes huge problems. This becomes increasingly problematic as the batteries age.

Size/volume wise for a given AHr capacity will come out to be an exact push, but the series configuration will be a much wiser choice.

Larry

[wavetar]

We use the factory battery back-up systems for Micor, MSR2000, MSF5000, MTR2000 (w/Argus revert), and Quantar. I've never once measured a voltage beyond 13.8Vdc at the battery terminals, regardless of how long the battery has been there (on 12V stations, of course). We also average approx 5 years between battery changes. We only use gel cells, never flooded, and don't seem to have any problems. We make sure to set the battery charge level voltage appropriately & away it goes, set it & forget it.

Todd

[ASTROMODAT]

I coudn't agree more strongly with wavetar on this point. We also use factory Quantars, with 24 volt battery strings, comprised of gel cells. These have lasted 5+ years, with no problems at all. As he said, "Just set it, and forget it!"

BTW, Yes, one can go with all sorts of exotic AC inverter systems and the like, and pay tons of money for same. In my opinion, those sytems tend to be huge overkill, and you can wind up paying many times more for such systems than the Quantar itself. Way over the top, and not worth it, IMHO.

Larry

[batdude]

ok, my last post on this before i go spend some coin.

due to weight considerations, the 6v x 4 idea just isn't feasible for my site - lifting four 70lb batteries up a 300ft concrete bridge pillar just isn't going to happen.

i am going to use two 12vdc AGM concorde/lifeline batteries rated at around 100AH wired in series - total weight about 100lbs or so. This should give me about 24 hours or so on battery with high-use of the repeater.

thanks to user 800mhz radio, i'll be using the built in backup feature of the quantar --- mainly to ensure that when the station drops to backup power i have the ability to easily control the output power of the station (i am going to drop it to 25w instead of 125w) - this is the biggest drawback to utilizing the heart interface that has been hashed out before...can't control station power level....not to mention the damn thing costs $1k.

question is... how does the quantar power supply charge the batteries? is this some kind of float charging system that tapers the charge according to the state of the battery?

and #2 is... i notice in my fat quantar book it speaks of a temperature sensor... i think this would only be applicable to lead-acid batteries (wet electrolyte) since AGM's don't produce heat. thoughts on this?

i am wondering if #1 and #2 are tied together in that the quantar power supply varies the applied voltage based upon the heat sensed by the battery... then again, i specifically remember that the quantar software has a selection for the type of battery connected to the damn thing...


THANKS FOR ALL THE HELP! - I will post pictures when i pull this one off...

doug

[RKG]

1. You won't get anything near 24 hours of service out of a 100 AH 24 VDC bank. The only usable part of the batteries is the top 50% (or 100 AH). The Quantar draws 600 watts when transmitting at 100 W (RF) and 60 watts when not transmitting (regardless of power setting) (draw is same for squelched or receiving, as it is dominated by the exciter). Take your expected duty cycle to get a weighted average draw (in amps), and then divide that into 50, and that is your design on-battery service life.

Note in the process that your 100 AH rated batteries are only worth a nominal 100 AH at a draw of or less than 5% of that value (i.e, 5A). If you calculate a higher weighted average draw, the nominal capacity (only half of which is usable) is less than the rated nominal capacity.

For what it is worth, in testing I've run a 100W Quantar on batteries (2x100AH) for over 4 hours without seeing a material voltage drop. The test was truncated because I was running out of time, not battery.

2. A good charger wants battery temperature input not because the batteries generate heat, but because the charging curve should be adjusted if the ambient temperature differs from the nominal ambient for which the curve is set. For instance, the 14.4/13.4 common set points for 12V batteries are based on an ambient temperature of 70F.

3. If you intend to run for an extended time on batteries, you should know how your device reacts to decreasing battery voltage. Specifically, at a voltage below about 11.2 VDC (12V system), the device should shut down to protect itself from overcurrent. I don't know how the Q revert system handles low voltage.

[batdude]

ok, i lied - please don't take this as "picking apart" your post - i'm just trying to get this right the first time - i hate climbing.


1. You won't get anything near 24 hours of service out of a 100 AH 24 VDC bank.

ok, roger that - what CAN i expect say at a 50/50 duty cycle and cutting the quantar power back to 25w? (certainly that cuts the 600w draw on transmit to something more like 300w or so) i am using 50/50 since if this station is on battery power, i will assume that some catastrophe has occurred which will result in more use of the repeater.


The only usable part of the batteries is the top 50% (or 100 AH).


i understand that based on the drop in terminal voltage (but i think you meant top 50 % = 50A assuming i am using two 12vdc 100AH cells connected in series ... (this is my intention)


The Quantar draws 600 watts when transmitting at 100 W (RF) and 60 watts when not transmitting (regardless of power setting) (draw is same for squelched or receiving, as it is dominated by the exciter). Take your expected duty cycle to get a weighted average draw (in amps), and then divide that into 50, and that is your design on-battery service life.


Lost me on that one.. 50/50 cycle = 300w 50% of the time and 60w the other 50%... what i am probably missing here is the relationship between AC power and DC current requirements....


Note in the process that your 100 AH rated batteries are only worth a nominal 100 AH at a draw of or less than 5% of that value (i.e, 5A).
roger that - but can't i expect a 300w load @ 24vdc to draw about 12 amps....?


If you calculate a higher weighted average draw, the nominal capacity (only half of which is usable) is less than the rated nominal capacity.
For what it is worth, in testing I've run a 100W Quantar on batteries (2x100AH) for over 4 hours without seeing a material voltage drop. The test was truncated because I was running out of time, not battery.


i'd like to get a run time of about 24 hours. the last power outage at my site was about 24 hours or so, and that's what i'd like to plan on.

granted, this is no police repeater. however, it's what i would like to think a "high profile" ham repeater. i won't bore you with the details - but it needs to work - rain or shine. barring a storm blowing the damn antenna off the bridge or taking a direct strike (my lightning protection issues are a whole other mess) i need this machine to be the one that everyone depends on.


2. A good charger wants battery temperature input not because the batteries generate heat, but because the charging curve should be adjusted if the ambient temperature differs from the nominal ambient for which the curve is set. For instance, the 14.4/13.4 common set points for 12V batteries are based on an ambient temperature of 70F.

ok, understand that. i would be willing to bet that the average temperature inside the upper pillar on this bridge stays about 79 degrees year round with VERY LITTLE variation over the year.

what i was getting at with my post is -- should i set the battery type to "NONE" in the software and use an external charger. what the software help screens don't tell you is whether or not setting the batt type to "NONE" will still make the station revert to DC upon AC fail....


3. If you intend to run for an extended time on batteries, you should know how your device reacts to decreasing battery voltage. Specifically, at a voltage below about 11.2 VDC (12V system), the device should shut down to protect itself from overcurrent. I don't know how the Q revert system handles low voltage

the software help talks a little about power cutback as battery voltage drops (but i didn't write down the exact numbers) - and eventually powers down the station due to low voltage input from the battery to prevent exactly what you discuss.

what i DON'T have is another quantar - or the ability to do some dry runs without actually going to the bridge and trying it out - and as stated, i only want to do this ONCE....



thanks again,


doug

[ASTROMODAT]

Doug, the Ahr system capacity rating determines the size (volume) and weight of the battery bank (based on any given battery technology). So, if you are shooting for 400 Ahr @ 24 volts, whether you parallel 2, 24 V batteries that are rated at 200 Ahr each, or you series 4 batteries that are each 6V @ 400 AHr, the volume and weight of the battery bank will be essentially the same. Therefore, how much weight and volume you need to strap to your back as you climb the bridge is essentially irrelevant to the parallel versus series argument. Keep in mind that you are much better off with 4 qty 6 V batteries in series, as opposed to 2 qty 12 V batteries in parallel. Parallelling batteries causes many problems, and these can be avoided by a series lash up.

Larry

[batdude]

roger that larry

problem is that the smallest "high cap" AGM i can find in 6vdc is 170 amps @ $180 a pop

i was going to series two 12vdc batts instead @ about 125ah (about 140 a pop and i only need two instead of 4)



d

[ASTROMODAT]

You also need something like a nice Bell Super 205A to lift you and your stuff up there!

Larry

[RKG]

1. The reason for limiting energy draw from a storage battery to the top 50% of nominal capacity is not directly related to voltage drop, but rather battery life. Studies have shown that the number of cycles you can expect from a good deep cycle battery (of any sort) is an inverse function of how deeply they are drawn down before recharging. Top of the line batteries (Rolls, in the case of flooded cells, and East Penn, in the case of gel cells) should go for 1,000 cycles if the draw is limited to top 25%, about 700 or so if the draw is limited to 50%. Once the draw goes deeper, life is sharply curtailed.

2. Here is a shot at the calc you wanted, making the assumption (I don’t know if this is true) (a) that you cut RF output down to 25W during revert and (b) that doing so cuts station draw from 600W to 150W:

Duty Cycle you specify is 50-50 (i.e, 50% of seconds transmitting and 50% of seconds not transmitting); that is VERY high. But using it for the moment, if the station draws 150W transmitting and 60W not transmitting, then it will average on a 50-50 duty cycle 105W. This is approximately 10A @ 12VDC or 5A at 24VDC.

You propose to use two 12V-125AH batteries in series, which will yield one 24V-125AH battery. Since your average draw on the battery is about 5% of nominal, the battery should be able to support this load for 10 hours before reaching the 50% drawdown point.

Note that if the current draw during xmit were 300W (versus 150W), then the average draw would be 180W, which is about 18A @ 12VDC or 9A @ 24VDC. Since this is more than 5% of the nominal capacity of your 125AH battery, its available AH would be less; say, about 100. 50% of that is 50AH, and at 9A, you’d reach the 50% drawdown point at about 5-1/2 hours.

I’d regard both of these results to be conservative, since I don’t think your real life duty cycle would be anywhere near 50-50.

Here is a caveat: I don’t know what the battery voltage would be at this much extended load, but based on experience, I’d guess it to be in the range of 11.5V (or 23.0V on a 24VDC system). A lot of electronic equipment will shut down when voltage gets that low. I don’t know how the revert system of the Quantar handles low voltage.

3. As prior posts hint (strongly), I don’t trust the battery chargers that are OEM’d into radio products sold by people who know far less about batteries and charging them than they do about radios. However, I do know that the Quantar RSS gives you four choices of battery types, which implies (but does not guarantee, and the point is not explored in either the station manual or the RSS manual) that the different battery type selections generate different set points on some variant of the “Ideal Charge Curve.”

From the Hardware screen, the RSS gives you four battery type choices: None, Lead Acid-Linear, Lead Acid Non-linear, and NICAD. Use the Lead Acid-Linear selection for flood-cell lead acid batteries and the Lead Acid Non-linear setting for gel cells. There is no setting for AGMs, but I’ve been told by folks whose judgment I trust that, if your charger doesn’t have a specific curve for AGMs, you can use the flooded cell curve with no significant impact on the batteries.

The trip points you are looking for in the Ideal Charge Curve are 14.4-14.5/13.3 (double these for 24V batteries) for flooded cells and 14.1-14.2/13.7 for gel cells (ditto). (Note that there is some controversy about the acceptance set point for gel cells; battery manufacturers specify a max of 14.1, but experience of a number of folks is that at 14.1 the batteries won’t fully charge and 14.3 is a safe and effective setting.) I say again: there isn’t a hint in the Q RSS literature that these setting affect the Ideal Charge Curve setpoints, or even that the Q revert board uses a multi-stage charging function. If I had a Q with the revert board, a recording battery meter, and a lot of time, I could experiment to see how the revert charger charges, but I don’t have the first or the third of the required items.

Forgoing setpoints are for 70F; they go up for lower temps and down for higher temps. If your battery room is environmentally controlled at 75 or so, use them and you can forget temperature compensation.

Whatever you do, do NOT employ the Q “equalization” function, for any type of battery.

4. As you can tell, if I were doing this, I would certainly use an external battery charger. Two reasons: first, I want the batteries charged correctly, fully and efficiently; second, I don’t want the batteries cooked. I trust a number of commercially available charging systems. I don’t trust the charging system built into the Q revert board. But, if you’re going to pay the $500 for the Q board, it seems to be really expensive to then invest several hundred $ more for a good true multi-stage external charger.

Setting the battery type to “None” will defeat the charging function but will leave the battery revert function (if you have the revert board installed) working: “Setting the battery type to NONE will DISABLE the charging circuitry, but it does not affect the battery revert or low battery disconnect, which are built in to the battery supply hardware. Select NONE for battery type if the batteries to be used are charged from an external battery charger.” (From the RSS manual.)

5. I’d be leery of anyone selling 12V 120AH AGMs for $140 per. According to my sources, the Group 31 AGM is only rated at 105AH (and costs about $200) (and weighs 70 pounds). The next biggest is the 4D size, which is over 20 inches long and weighs 130 pounds (and is rated at 200AH and costs $350). I’m not saying what you’ve found doesn’t exist, but it is far enough off the “norm” for these batteries that I’d take a real close look.

6. Constructive nit-picking is how we all get more precise and learn something; I’d never take offense.

[ASTROMODAT]

Doug, IMHO, your best bet is to go with Motorola's stock setup on the Quantar, utilizing their station supply, a proven (and Motorola endorsed) solution. I know it will work perfectly for you, as ours has for many years, and as these posts have pointed out. Building a nuclear bomb shelter to protect you from a BB gun might be a lot of fun, but unless you have a lot of $ to throw around... I seem to recall that you are trying to do this with a limited and sensible budget. Go with your instincts, and your two batteries hung off the Quant's supply, and you will be just fine!

Larry

[Bob W]

what i DON'T have is another quantar - or the ability to do some dry runs without actually going to the bridge and trying it out - and as stated, i only want to do this ONCE....


doug

I made some measurements that might be useful....
(all the ...'s are 'cause I couldn't get the format right otherwise)

This is a 125W VHF Quantar, W/ wireline, no UHSO

Results @27c Voltages go up with decrease in temperature.

................................Float........Equal.........Charge Current Limit
Lead Acid Linear........26.6V........28.2V........3.50A
Lead acid non............27.1V........xx.x..........3.50A
Nicad........................28.5V........31.7V........3.50A

Current @23.5 Volts...25W..........50W........75W.......100w......125W
..................................5.24A........7.21A......8.82A.....10.17A...11.94A

All with no PA fan on.

Idle current @24v 1.18 amps

Death occurs at 21.14 volts

This might be enough info for you to calculate runtime. Here's a table from power-sonic that might help. According to them, and in my experience, Lead_Acid_Non will float a gel cell properly - 2.26 volts per cell. Linear is for lead-antimony (flooded) cells - 2.21 volts per cell. Too low for lead-calcium (gel cell, AGM, etc). Too low float voltage makes the plates absorb water, and swell, and sulfate. So... It looks like the power supply does produce the correct voltages for the listed battery types. 3.5 amp current limit will take a long time to recharge a large battery - like a day and a half for 100 AH like the one in the link. But, really, how often will you take it to nothing?

http://www.power-sonic.com/121000.html

One other thing... You will need to program something less than 75watts on battery revert. If not, and if the input voltage at the connector is less than 26 volts, you will get a PA fail upon key-up. It does recover, and drop down in power, but run 50 watts on revert, and you'll be good.
At 25, with the 100 AH battery in the link, according to my table and their table, and the cutoff voltage, you should get something more than 15 hours continuous key down before it dies. Also, you get that nice single tone beep over the air when on revert. Use as short leads as possible to minimize drop.

[batdude]

bob w - you rock man!


that was exactly what i was after... thanks so much for the time it took to compile that data.... data which should be in the darn service manual in the first place!!!


doug