Posted: 1/9/2014 8:56:46 AM EDT
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Looking to get continue putting together items for my portable station which will include a battery in the case.
I know many people use 2 of the RBC6 UPS 12Ah batteries, but the case I have will only leave me about 3.5" clearance for the battery and these are listed at slightly larger then that. I was looking at the UB12220 22Ah battery instead since it is only 3" in width. Will this battery handle the amps needed for a 100w HF rig? My question relates to the 'Discharge Time vs Discharge Rate' charts shown for each one. The max current shown on the UB12220 chart is 5a and it is 36 on the UB12120 chart. See UB12220 Spec Sheet RBC6 (UB12120) Spec Sheet JLE |
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Neither of the battery setups will work as you described. A 100W HF rig needs [email protected], remember that it'll need more amps at a lower voltage to supply the same power output. You're going to wind up with somewhere around 14A available to the radio with the layout you proposed with two batteries, 13A available if you use the one 20Ah battery. It would work for a 50W VHF or UHF rig, but not an HF rig.
How much power does your HF rig draw while in RX mode? How much while idle? Mine draws just shy of 2A while idle. You need to know your rig's duty cycle (transmit vs receive vs idle) and the power draw for each of those "states", then you can figure your power requirements. You probably need either three of the 12Ah batteries, or two of the 20Ah batteries to meet your goals. Take your current draw while transmitting, mine is ~20A, multiply that by the voltage of your battery pack, mine is 13.8, to get your power comsumption. That gives me a usage of 276W while transmitting. Take your current draw while receiving, mine is ~2.1A, multiply that by the voltage of your battery pack, mine is 13.8, to get your power comsumption. That gives me a usage of 28.98W while receiving. Idle, ~1.8A, 24.84W usage. How long will you be using this? 8 hours a day? How much will be spent transmitting, 20% of the time? Receiving 60%? Idle 20%? Ok, let's do this: 276W * .20 * 8= 441.6 watts 28.98W * .60 * 8= 139.10400 watts 24.84W * .20 * 8= 39.74400 watts Total over an 8h shift = 620.44800 watts Once I get back from this meeting, I'll finish the calculations, unless someone else wants to step in. |
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Quoted: You're going to wind up with somewhere around 14A available to the radio with the layout you proposed with two batteries, 13A available if you use the one 20Ah battery.
How were you able to determine the 14A and 13A amounts you mentioned above? I get the basics regarding the capacity, length of time, duty cycle, ampHours etc (as much as a Mech Engineer can  )
I was mainly wondering if there is a physical reason that the UB12220 could not deliver the same current (even if for a limited amount of time) that the RBC6 could. (and how to determine this) It seemed like the charts they showed for Discharge were really different. JLE |
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To learn more about how SLA batteries work for Ham, have a look at my video (I've linked to the battery section, as it's a rather long presentation): http://youtu.be/8SuvAKZt0Vs?t=8m3s
The cliffs notes - your radio will not transmit below 11.8 volts (13.8V+/- 15%). At 11.8v, your SLA battery is approximately 60% dead - this means that you really only have 60% of the battery AH rating for your radio activities (your 22AH battery is really only good for 13ishAH). These batteries absolutely will support the current draw you require as long as you have good heavy wire between the radio and battery (I always replace factory wiring harnesses with larger wire). Bigger wire = less voltage drop under heavy load. In these charts, when it says CA, that means the coefficient x the AH rating - for a 22AH battery, 3.0CA = 66Amps. When transmitting voice (SSB) at 100 watts, your radio will "average" 10-16 amps of current draw while you are talking. Quoted:
Looking to get continue putting together items for my portable station which will include a battery in the case. I know many people use 2 of the RBC6 UPS 12Ah batteries, but the case I have will only leave me about 3.5" clearance for the battery and these are listed at slightly larger then that. I was looking at the UB12220 22Ah battery instead since it is only 3" in width. Will this battery handle the amps needed for a 100w HF rig? My question relates to the 'Discharge Time vs Discharge Rate' charts shown for each one. The max current shown on the UB12220 chart is 5a and it is 36 on the UB12120 chart. See UB12220 Spec Sheet RBC6 (UB12120) Spec Sheet JLE |
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THANKS! Much clearer now.
This part I had a pretty good understanding on. Quoted: At 11.8v, your SLA battery is approximately 60% dead - this means that you really only have 60% of the battery AH rating for your radio activities (your 22AH battery is really only good for 13ishAH). Quoted: At 11.8v, your SLA battery is approximately 60% dead - this means that you really only have 60% of the battery AH rating for your radio activities (your 22AH battery is really only good for 13ishAH). This was my main concern from looking at the spec sheets for each. These batteries absolutely will support the current draw you require as long as you have good heavy wire between the radio and battery (I always replace factory wiring harnesses with larger wire). Bigger wire = less voltage drop under heavy load. This is what I was missing/didn't know and what was causing my concern. I can now file this new education away for later. In these charts, when it says CA, that means the coefficient x the AH rating - for a 22AH battery, 3.0CA = 66Amps. I will check out the video this evening! JLE |
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Quoted:
How were you able to determine the 14A and 13A amounts you mentioned above? Rounding down to the nearest whole Ah. You'll never get the quoted capacity for batteries. I get the basics regarding the capacity, length of time, duty cycle, ampHours etc (as much as a Mech Engineer can )
I was mainly wondering if there is a physical reason that the UB12220 could not deliver the same current (even if for a limited amount of time) that the RBC6 could. (and how to determine this) It seemed like the charts they showed for Discharge were really different. The 12220 has the same size terminals as the RBC6, and you want to spread that load across as much surface area as possible to reduce the heating of the contacts. Left aside is the fact that battery manufacturers quote "capacity" as running the battery down to 11V. I'll finish the calcs when I get home. ETA: remember that batteries degrade over time, and you should only really use 50% of your bank's capacity if you intend to use them for a long time. |
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Wow, I totally screwed up all of those calculations. I really have to stop posting while I'm at work. I think I was figuring watt hours for solar replenishment... So, anyway, during a shift, you'll use about 621 watts that you have to put that back into the battery.
Since I'm not sure what I was actually doing earlier, a 20Ah battery will give you about an hour and 45 minutes of run time at 40/60 transmit/receive, and you might burn up the battery by unsafely discharging it. Sorry I can't help more, I have no idea wtf I was talking about earlier. You should really consider 2x 20Ah batteries if you want to run 100W. ETA: Reserve Capacity is really what you should be looking at, not Ah. |
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Just today I received this 55 AH battery via Brown Santa.
http://www.ebay.com/itm/200962020135 This is about $25 cheaper than on the Gruber Power site. and one of these http://www.ebay.com/itm/200957552197 And a new solar charge controller from yet another manufacturer that has sent it to me for test / eval /review. I will be reporting on this when I get it all into operation. The 55 ah Elite is replacing four 12 v 12 ah (two RBC-6) batteries that are about to be beyond their "use by" date. They are 4-1/2 years old and need replacing. |
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www.gruberpower.com
Just about any size, shape, capacity SLA/AGM battery you could want. |
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Quoted:
Unless you're hiking into remote areas, I don't see much wisdom in carrying around a dedicated battery anyway, since the battery in any nearby car will power the rig just fine. Quoted:
Quoted:
Back to the OP, why is it necessary to have your batteries inside the box? Unless you're hiking into remote areas, I don't see much wisdom in carrying around a dedicated battery anyway, since the battery in any nearby car will power the rig just fine. Unless the tree you're hanging your antenna from is 20yds from said car. For a manpack or a emmcomm box I'd rather have a battery and have the entire thing self contained. |