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Old 30th May 2013, 03:13 PM   #111
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Quote:
Originally Posted by m R g S r View Post
That may be roughly accurate for no solar panels involved, but throw them into the mix, turning the volume up or down etc things change. So that's why I said very hard to get a good idea of how long it will last.
Yeah, I edited the equation to include charging sources...

That equation will work for continuously running flat-out, so could be considered a minimum battery life.
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Old 30th May 2013, 05:29 PM   #112
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Quote:
Originally Posted by m R g S r View Post
That may be roughly accurate for no solar panels involved, but throw them into the mix, turning the volume up or down etc things change. So that's why I said very hard to get a good idea of how long it will last.
My estimate include the solar panels at rated power.
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Old 30th May 2013, 07:21 PM   #113
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Quote:
Originally Posted by m R g S r View Post
Art do you have any tables that show voltage vs charge percentage for LiFe batteries? Just curios so I know what percentage I'm at while using the radio....

I know that may be tricky when the radio is in use, because most tables are for resting voltage, not in use.

Just from the few times I checked over the weekend while using the radio, with the panels connected, in full sun, the voltage with the LiFe battery was still higher than even the big lead acid batteries were at full charge, In full sun!
That would make sense, the LiFePO4 have a higher full charge voltage than LA batteries.

I have seen no state of charge tables for LiFePO4, the very narrow range from full charge to discharge makes it difficult to estimate.

I made my own chart, the one below is the second revision (version one resulted in me pushing the bike when I thought I had about 30% left ), divided by four from my 48 V pack estimate.

Your radio won't average 1C (40amp) draw, so your "load" voltage will be higher.
The LiFePO4 recover to a resting voltage much faster than LA.

If you don't have a LVC, get one, the LiFePO4 just go from good to nothing in a heartbeat.
A $25 LVC will save your batteries if you don't happen to be looking at your VOM when the sun goes behind a cloud and the voltage falls off the cliff.

Art
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File Type: png State of Charge.png (19.8 KB, 68 views)

Last edited by weltersys; 30th May 2013 at 07:30 PM.
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Old 31st May 2013, 04:08 AM   #114
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Is that 100% charge right? My charger charged the pack more than that....
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Old 31st May 2013, 04:12 AM   #115
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This:
Smart Charger (10 A) for 12.8V LiFePO4 Battery Pack, Worldwide use, CE listed

Cut off the charge at right around 14.6. Hope that's not over charging the pack causing damage.
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Old 31st May 2013, 07:59 PM   #116
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Quote:
Originally Posted by m R g S r View Post
This:
Smart Charger (10 A) for 12.8V LiFePO4 Battery Pack, Worldwide use, CE listed

Cut off the charge at right around 14.6. Hope that's not over charging the pack causing damage.
The individual cells can be charged to 3.8v, x 4 is 15.2 v.
14.6/4 is 3.65v, considered "safe" for these LiFePO4.
The topped off voltage drops from 14.6 to 13.6 very quickly which is why I used 13.6 as 100% charge in the state of charge chart, when 100% could actually be as high as 15.2v for a few seconds.

Good idea to initially check the individual cells, if one is not accepting charge, even at 14.6v finish some of the other cells can be overcharged.

I over discharged my pack, had to individually charge a few cells that went "over the cliff", they seem to have not suffered damage, but had me worried.

When I was testing my bike for distance, I individually tweaked all the cells to 3.8v, compared to just letting the charger quit at an average of 3.65v. It probably only amounted to a few % more distance covered, not worth the effort.

You can see in the discharge curve that anything above 3.2 volts per cell is gone in a hurry.
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Old 31st May 2013, 08:01 PM   #117
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Awesome Info thanks again. Will do!
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Old 1st June 2013, 05:08 PM   #118
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I checked and all were pretty close. Topped off charge after resting for 48 hours is 13.6v if I remember correctly. So good to go! Can't wait to use it tomorrow
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Old 2nd June 2013, 02:16 PM   #119
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At the beach now. Been on for an hour at volume 22 out of 60 I believe?
Working voltage is at 13.32V. Once I crank it ill monitor voltage and see how long she lasts!!
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