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Old 17-01-2013, 17:09   #1186
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Doug,

I'm sure whatever inverter you are using has a voltage read out. On my old Cal 40 I had a Trace 2012 (still have it 20 years later) and would watch my battery voltage when powering a 1500 watt load, if memory serves, it was something more than 1 volt sag. Check your voltage before the load of the microwave and during the load. I'll bet your voltage sag will be quite small compared to the AGMs, which they do better than my 6 volt flooded golf cart batteries on the Cal.
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Old 17-01-2013, 17:20   #1187
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A lot of the voltage sag can be between the inverter and the battery. I see .4 to .5V between my inverter/chargers and the battery with 10-12 ft 4/0 inverter cables at 100A. Shorter would be better. The battery voltage only varies about .1V.
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Old 17-01-2013, 17:22   #1188
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Your right. Doug, if it isn't too much trouble, take a reading with your VOM at the battery while the microwave is running.
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Old 17-01-2013, 17:27   #1189
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Quote:
Originally Posted by diugo View Post
Thanks Bob, I really appreciate your optimism and your willingness to share your Balqon experience and your test results. In a few minutes, I will be pulling the plug on my old AGMs and finally bringing the LFPs online in a big way---microwaving my supper! Wish me luck...

It is interesting to hear that AGM's also suffer short life in RV applications. In the marine market, at least here in the great white North, they have been less than stellar performers for boats that:

A) Don't get back to 100% as often as possible

B) Charge at less than manufacturers suggested current rates 20% for Lifeline and 40% for Odyssey

C) Are cycled deeper than 50%

D) Mooring sailed vessels

E) Don't charge at the upper end of suggested absorption voltages

F) Don't use temp compensated charging

I see average life spans of 2-4 years on mooring sailed boats... For a boat that is at a dock charge every night, and only leaves on weekends, they average closer to 4-5 with the occasional outliers to 6 or 7...
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Old 17-01-2013, 17:35   #1190
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Quote:
Originally Posted by diugo

With an internal resistance of 2 millohms per cell? You've got to be kidding.
What's that got to do with capacity. ? , Peukerts exponent ,or more correctly his equation models the capacity of a LA battery against differing discharge currents, with an exponent of 1, the battery capacity remains the same irrespective of amount of the discharge rate.

Internal impedance is related to voltage drop , ie the slope of the discharge curve, Li has extremely low resistance , ie its almost a perfect voltage source , ie the voltage only droops a tiny amount under load

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Old 17-01-2013, 17:38   #1191
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Quote:
Originally Posted by deckofficer

Dave, that is what I thought too, but either the ratings on our cells are very conservative or there is a Peukert effect, not nearly as pronounced as LA, but if nil then my battery at 1365 w-hr now should be fully discharged as it is rated at 1280 w-hr.

I think their ratings are for use in the EV applications, where 3~5 C discharge is common. For our use they appear to have much higher capacities than their ratings.
Then either they are as you say conservatively rated , because I don't beleive they have much of a Peukerts effect certainly within 0-1 C which is the range were dealing with

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Old 17-01-2013, 17:38   #1192
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Quote:
Originally Posted by Maine Sail View Post

It is interesting to hear that AGM's also suffer short life in RV applications. In the marine market, at least here in the great white North, they have been less than stellar performers for boats that:

A) Don't get back to 100% as often as possible

B) Charge at less than manufacturers suggested current rates 20% for Lifeline and 40% for Odyssey

C) Are cycled deeper than 50%

D) Mooring sailed vessels

E) Don't charge at the upper end of suggested absorption voltages

F) Don't use temp compensated charging

I see average life spans of 2-4 years on mooring sailed boats... For a boat that is at a dock charge every night, and only leaves on weekends, they average closer to 4-5 with the occasional outliers to 6 or 7...
Other than the leakproof, no maintenance aspect, Im not sure there is much advantage to AGM over LA. There was a guy a while back on this thread that made a really good case for tubular LA forklift batteries. Even in comparison to LiFePO4.... If you can deal with the size and weight, and perhaps the cost in North America. I think they may be more widely available in Europe.
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Old 17-01-2013, 17:40   #1193
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Quote:
Originally Posted by Maine Sail

It is interesting to hear that AGM's also suffer short life in RV applications. In the marine market, at least here in the great white North, they have been less than stellar performers for boats that:

A) Don't get back to 100% as often as possible

B) Charge at less than manufacturers suggested current rates 20% for Lifeline and 40% for Odyssey

C) Are cycled deeper than 50%

D) Mooring sailed vessels

E) Don't charge at the upper end of suggested absorption voltages

F) Don't use temp compensated charging

I see average life spans of 2-4 years on mooring sailed boats... For a boat that is at a dock charge every night, and only leaves on weekends, they average closer to 4-5 with the occasional outliers to 6 or 7...
I have Argued for years that AGMs have no place on boats given the typical usage patterns. None of their benefits can really be utilised and all of their disadvantages are exacerbated. Unsuitable technology for this applications and they have been foster on unknowing people as a kind of super LA battery. They are merely different not better.

Dave
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Old 17-01-2013, 17:45   #1194
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Dave, well that makes me happy. For my application I based my numbers on the battery delivering 1280 w-hr for 100% DOD. When this pack #2 only gave 980 w-hr on the first cycle, I was a bit bummed.

I am now 47.5 hours of a 30 watt load, all cells reading 3.31 after delivering 1425 w-hr.
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Old 17-01-2013, 17:46   #1195
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

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Originally Posted by goboatingnow View Post
I have Argued for years that AGMs have no place on boats given the typical usage patterns. None of their benefits can really be utilised and all of their disadvantages are exacerbated. Unsuitable technology for this applications and they have been foster on unknowing people as a kind of super LA battery. They are merely different not better.

Dave
We are in 100% agreement!! I too have been arguing/warning/cautioning against them for years.

Course I bit into the bogus promises of 80% DOD, (now 50% DOD recommended), don't sulfate, more cycles and wets etc. etc. and got STUNG hard. Customers were not happy.... They have proven much less tollerant of the deep cycling and charging practices we do on boats than GEL or flooded batts.
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Old 17-01-2013, 17:49   #1196
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

Dave,

I like my AGMs compared to flooded. Both a deep cycle and cranking battery that has no problem with 1.0 C charge compared to the 0.1 C charge I had to restrict to on my golf cart batteries.
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Old 17-01-2013, 17:56   #1197
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Quote:
Originally Posted by ebaugh

Other than the leakproof, no maintenance aspect, Im not sure there is much advantage to AGM over LA. There was a guy a while back on this thread that made a really good case for tubular LA forklift batteries. Even in comparison to LiFePO4.... If you can deal with the size and weight, and perhaps the cost in North America. I think they may be more widely available in Europe.
It's worse then that , they have disadvantages over flooded LA in particular. AGMs need to quickly recharged to 100% after discharge, something that boater struggle to do. , AGMs are sensitive to absorption voltage specs. Again often boaters don't have proper AGM charge regulator, especially on alternators. AGMs are very sensitive to over discharge, 50 percent is max really,

AGMs get murdered on boats. , my marina is littered with dumped AGMs. Usually annoyed customers too. Who have paid big bucks

tubular LA traction batteries are widely available certainly in Europe for electric fork truck applications. They are very expensive, but rugged. , Li ferrous is cheaper and better.

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Old 17-01-2013, 17:56   #1198
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Dave, well that makes me happy. For my application I based my numbers on the battery delivering 1280 w-hr for 100% DOD. When this pack #2 only gave 980 w-hr on the first cycle, I was a bit bummed.

I am now 47.5 hours of a 30 watt load, all cells reading 3.31 after delivering 1425 w-hr.
The discharging curve for my cells...show 10% more capacity at 3C discharge than .5C. But the difference is nearly nothing between 1C and .5C, so I think there may be a point of diminishing returns at fractions of C discharge rates.

Edit:... More capacity at .5C than 3C. Sorry...
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Old 17-01-2013, 17:58   #1199
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Re: LiFePO4 Batteries: Discussion Thread for Those Using Them as House Banks

It shows more at 3.0C vs 0.5C ?
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Old 17-01-2013, 17:59   #1200
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It shows more at 3.0C vs 0.5C ?
Sorry...see edit...
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