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Old 11-17-2016, 10:21 PM   #21
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RC is actually not a very good measurement for a deep cycle battery.

https://www.batterystuff.com/kb/arti...ry-basics.html

It is typically found only in automotive batteries and is defined as the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.

In the past, RC was used to give some idea of how long a particular battery will run your car if the alternator belt broke. To convert RC (found today only on Dual Purpose (Marine) batteries) to AH (used almost exclusively on true deep cycle batteries) you must multiply the RC in minutes by 0.4167

So a Marine (DP) battery with an RC of 180 minutes would hold the equivalent energy of a Deep Cycle Battery rated at 75AH@25amps. You will need to multiply that by 1.25 to get the AH@20 amps (more common rating).

I attached the definition of Peukert Effect on battery capacity affected by discharge (or Charge) rate.
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File Type: pdf What is the Peukert Effect.pdf (164.5 KB, 6 views)
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Old 11-17-2016, 11:08 PM   #22
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Originally Posted by Herk7769 View Post
RC is actually not a very good measurement for a deep cycle battery.

https://www.batterystuff.com/kb/arti...ry-basics.html

It is typically found only in automotive batteries and is defined as the number of minutes a fully charged battery at 80 ° F will discharge 25 amps until the battery drops below 10.5 volts.

In the past, RC was used to give some idea of how long a particular battery will run your car if the alternator belt broke. To convert RC (found today only on Dual Purpose (Marine) batteries) to AH (used almost exclusively on true deep cycle batteries) you must multiply the RC in minutes by 0.4167

So a Marine (DP) battery with an RC of 180 minutes would hold the equivalent energy of a Deep Cycle Battery rated at 75AH.

I attached the definition of Peukert Effect on battery capacity affected by discharge (or Charge) rate.
I couldn't figure out where the exponent "n" was supposed to go in your attached PDF (it isn't shown as an "exponent") until I looked elsewhere on the web. It's the exponent to the current, but in your PDF they've made it looked like it's a multiplier of time.

In doing this, I came across this website, that shows you must be careful in using this equation.

SmartGauge Electronics - Peukert's Equation - what it means to you

They never show how the value of the exponent is actually calculated, which I also didn't find in at least the first few google search responses I looked at. So I don't know if your PDF's determination fixes that or not, or is someone "approximation." It seemed to me that the exponent needed to be determined by actually testing a specific battery.
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Old 11-18-2016, 06:59 AM   #23
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That link was great and added to my knowledge of the Peukert Effect on RV batteries.

From the article, the equation and graphs from my earlier post will work just fine for the 99% of commercially available RV batteries on the market.

For the 1% that use a non-standard AH definition, you can very easily convert that AH rating to the 20 hour rate with very simple algebra as long as the definition used by that manufacturer is published in their battery data.

The graph I used also uses the "n" exponent for true Deep Cycle batteries, like golf cart, Trojan, and backup storage, used in nearly all solar installations.

The PE for other types of batteries, like Dual Purpose and car starting batteries, would make the slope more shallow due to their ability to deliver higher currents without effecting capacity as much; but you must remember that their capacity for an identical weight/size is very much less. In the case of a starting battery, incredibly less.

For example of a battery at the other extreme from deep cycle, a starting battery's plate design is such that it can be charged and discharged quickly, deliver a huge amount of cranking amps, but the trade off is almost no staying power (capacity). Playing your radio alone for a few hours while you wax the car can result in a "no start" when you are done.
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Old 11-18-2016, 11:26 PM   #24
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The information still keeps coming .... thanks guys and gals.
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Old 06-05-2017, 06:33 AM   #25
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Originally Posted by mlatter View Post
Or you could get a higher-end invertor and put it between your generator/line input transfer switch and your main panel. You can even get an option that will auto-start your generator when the batteries reach a certain level of depletion.


Been think about doing this ... can you send me a link to what you have? Thanks
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Old 06-05-2017, 09:03 AM   #26
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Been think about doing this ... can you send me a link to what you have? Thanks
For the inverter, I use the Xantrex Freedom SW3012 inverter/charger: Inverter Charger | Freedom SW Inverter/Charger | Xantrex

I was able to bypass my converter and allow the inverter to supply the 12v for both load and battery charging - up to 150 amps. 3000 watt inversion will allow you to run any a/c appliance, but you have to keep in mind your battery reserve to figure out how long you can run things.

I also got the System Control Panel to go with it.

Very happy.
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Old 06-05-2017, 09:14 AM   #27
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And, to add one more tidbit..... an inverter will draw power when on, even if nothing is plugged in to it. Not much, but it adds up. In fact a large inverter will draw as much as 2-3 Amps...... Yup, that's 24-36 Amps over 12 hours.
Which is why you purchase a remote switching inverter like a Xantrex or Aims Power PSW. My 2500 watt Aims has total remote switching, that is, unless the green LED on the switch panel is illuminated, the inverter is drawing no idle current.

FYI, the Aims Power PSW Inverter has the lowest idle current draw of any unit made. I checked. Idle current on my 2500 watt is 2-3 ma, not amps.

Your 'tidbit' only applies to certain (non switching) units.
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