diy solar

diy solar

Can I get away with 95-100% DOD?

I always see this parroted....use between 80% - 20% for longevity my thought every time is what voltages are those?

If I'm charging to 14.1-14.2v and floating at 13.6v and haven't used below 12.65v what would you call these voltages in % reading?

99% of charging my lfp is done by solar. The system is never off, always have some sort of load on it being that it's is my main power source for living comfortable. Being used at whatever psoc with 100-150a loads at times. Now with 500+ full cycles on the batteries after 44 months with manufacturers claim of Cycle Life : >2000 (80% DOD); >3000 (70% DOD).

At the rate I'm going using the 80% DOD claim that only gives me another 11 years, so worrying about doubling the life by reducing capacity seems weird. :unsure:
 
Sojourner1 said:
At the rate I'm going using the 80% DOD claim that only gives me another 11 years, so worrying about doubling the life by reducing capacity seems weird. :unsure:
Click to expand...

Not sure on voltages but there are charts. Anyway, my plan, and also one of the reasons for swapping from FLA is I want a load of smart dump-loads. FLA loves to float at max voltage, so doesn't like dump loads.

But if you find a voltage at under 100% to trigger a water heater, fan, AirCon whatever, then that can only help increase battery life. That's ok on a 1000w RV setup only needing 1000w of dump load, but if you have a large house setup that's a hell of a dump load to use.
 
You know the answer you gave is the same answer that is usually given and always by folks that don't have lfp yet.

I believe charging to 80% would be near 13.8v (3.45vpc), 20% 11.4v (2.85vpc).

I smart dump my loads manually during the spring, summer, fall. It's nothing during this time to have countinous loads of 30-50a from 0900-1600 and still have the excess power going into the batteries for charging. If the batteries don't get to full who cares, theses aren't dead lead battery chemistry.

I believe the only difference of what you're saying is you would be at 48v (?) with a larger solar system.
 
Last edited:
Sojourner1 said:
99% of charging my lfp is done by solar. The system is never off, always have some sort of load on it being that it's is my main power source for living comfortable. Being used at whatever psoc with 100-150a loads at times.
Click to expand...

You hit an important point there, for those of us who are living offgrid, there is always an inverter running along with usual's like a fridge, a light or two, in general that's not a huge load but enough to keep the "top off" a battery pack. Even with that said, I rather prefer to run batteries within a respectable range that will prolong their life while getting the most reasonable amount out of them.

Because I'm using a Classic 200 and the Samlex EVO-4024 Inverter/Charger setting up the charge profiles is a tad trickier, plus the available amps for charging will have to be programmed in as well, maybe a charge rate of 50 Amps max ?.

Bulk Voltage: 28V - 29.2V
* Absorption Voltage : 28V - 29.2V Absorption Time 0-15 min
* Float Voltage : 26.6V - 27.6V
* Equalize : OFF or as short time possible @ float voltage
VOLTAGE CUTOFFS Low Voltage: 22V High Voltage: 29.2V
* not necessary, if possible, turn off.
I'm making the "assumption" from my collected research, that by using a lower rate @ 28V to charge vs 29V can help mitigate some heating potential and extend life cycles (very generalised) but there seems to be some extended debate on that.
 
Steve_S said:
I'm making the "assumption" from my collected research, that by using a lower rate @ 28V to charge vs 29V can help mitigate some heating potential and extend life cycles (very generalised) but there seems to be some extended debate on that.
Click to expand...
I'm guessing the heating you're referring to is cell temps?
From my personal observation with my prismatic cell batteries, cell heat is very minimal with fractional C charging. Meaning that the cell temps might rise a few degrees throughout the entire day while charging.

Here are some misc readings, this one here I didn't start recording the compartment temp yet.
Screenshot_20191229-062808_Excel.jpg
Screenshot_20191229-062829_Excel.jpg
Screenshot_20191229-041000_Excel.jpg
This here I started adding the compartment temp where the system is housed, there is an outside temp reading also but can't get that entire column to fit. I have 2 remote thermometers that can be read in the 5th wheel, 1 is in the compartment and 1 is outside for ambient air temps.
Screenshot_20191229-043344_Excel.jpg

Screenshot_20191229-044107_Excel.jpg

Screenshot_20191229-045109_Excel.jpg

I feel (atleast with my setup) cell temp (heat) is not that big of a deal.

There is actually 2 more columns that aren't showing, that would be the inverter voltage/ inverting amps (loads) being used during charging/ float.
 
Last edited:
gnubie said:
Did you take any special precautions such as those highlighted in the document referenced in this thread?
Click to expand...
I didn't do anything special, other than step a bit away from min/max voltages, as I stated above, and maintain reasonable temperature envelope, preventing extremes.
All this talk about 80%-20% SOC is mostly nonsense because SOC measurement is too complex with variable parameters you can't easily measure or control. Just step a little bit away from the absolute min/max voltages and maintain temperature closer to human comfort zone, that is all you need.
 
Sojourner1 said:
You know the answer you gave is the same answer that is usually given and always by folks that don't have lfp yet.

I believe charging to 80% would be near 13.8v (3.45vpc), 20% (2.85vpc).

I smart dump my loads manually during the spring, summer, fall. It's nothing during this time to have countinous loads of 30-50a from 0900-1600 and still have the excess power going into the batteries for charging. If the batteries don't get to full who cares, theses aren't dead lead battery chemistry.

I believe the only difference of what you're saying is you would be at 48v (?) with a larger solar system.
Click to expand...
Will has already done a video and a chart on this. Note that there are caveats: loads or chargers connected to the batteries will skew the readings, and 'voltage as a state of charge' is an estimate.

I would use:
13.4V (open circuit) as 100%
13.25VOC as 80%
12.9VOC as 20%
(double for 24v systems, x4 for 48v)
to start with and do some experimentation to see how your system responds.
 
Lost In The Desert said:
So 60% use? Only 10% more than LA?
Click to expand...
From what I've been reading and watching, a healthy, 100 amp flooded lead acid battery has about thirty amps available, (the battery can output higher "cold cranking amps", for brief time periods). An AGM lead acid battery does better with about 50% of it's rated amperage capacity available, (IE 50 amps are available with a 100 amp AGM). In regards to your excellent question, I you chose to only use 60% of the available amperage of a 100 amp, lifepo battery, (and I believe that healthy lifepo's deliver nearly all of their rated amperage capacity), then it stands to reason that you would be limiting yourself to about 60 amps of usage.
 
NOTE there is significant differences in FLA. a Deep Cycle battery has a lot more oomph than a car / rv / marine battery. Deep Cycle AGM's are also different than standard AGMs with a lot more juice behind them. Apples & Peaches !
 
offgriddle said:
From what I've been reading and watching, a healthy, 100 amp flooded lead acid battery has about thirty amps available, (the battery can output higher "cold cranking amps", for brief time periods). An AGM lead acid battery does better with about 50% of it's rated amperage capacity available, (IE 50 amps are available with a 100 amp AGM). In regards to your excellent question, I you chose to only use 60% of the available amperage of a 100 amp, lifepo battery, (and I believe that healthy lifepo's deliver nearly all of their rated amperage capacity), then it stands to reason that you would be limiting yourself to about 60 amps of usage.
Click to expand...

Not that I enjoy saying good things about Renogy, but you can pull the full amount of available power from their gel batteries. Too bad their proofreading is on par with their code writing. They can't even spell their own name correctly:

Description
Dg (deep cycle gel, 12V) series are pure Gel batteries with 12 years of floating design life. This series is ideal for standby or frequent cyclic discharge applications under extreme environments. The 12V 200Ah Rangy deep cycle pure Gel battery gives you maximum storage for any solar setup & can deliver 1000 cycles at 50% dud. Make the most of your solar System with a 12V 200Ah Rangy deep cycle pure Gel battery! Specifications: cells per unit: 6 voltage per unit: 12 Max. Discharge current: 2000 a (5 sec) normal operating temperature range: 25℃ plush; 5℃Float charging voltage: 13 6 to 13 8 VDC/unit average at 25℃
 
Sojourner1 said:
You know the answer you gave is the same answer that is usually given and always by folks that don't have lfp yet.

I believe charging to 80% would be near 13.8v (3.45vpc), 20% 11.4v (2.85vpc).

I smart dump my loads manually during the spring, summer, fall. It's nothing during this time to have countinous loads of 30-50a from 0900-1600 and still have the excess power going into the batteries for charging. If the batteries don't get to full who cares, theses aren't dead lead battery chemistry.

I believe the only difference of what you're saying is you would be at 48v (?) with a larger solar system.
Click to expand...
How fo you dump yhr
Lost In The Desert said:
Not that I enjoy saying good things about Renogy, but you can pull the full amount of available power from their gel batteries. Too bad their proofreading is on par with their code writing. They can't even spell their own name correctly:

Description
Dg (deep cycle gel, 12V) series are pure Gel batteries with 12 years of floating design life. This series is ideal for standby or frequent cyclic discharge applications under extreme environments. The 12V 200Ah Rangy deep cycle pure Gel battery gives you maximum storage for any solar setup & can deliver 1000 cycles at 50% dud. Make the most of your solar System with a 12V 200Ah Rangy deep cycle pure Gel battery! Specifications: cells per unit: 6 voltage per unit: 12 Max. Discharge current: 2000 a (5 sec) normal operating temperature range: 25℃ plush; 5℃Float charging voltage: 13 6 to 13 8 VDC/unit average at 25℃
Click to expand...
I don't know how Renogy is supposed to be spelled, but I do know that a gel cell is a lead acid battery, where the acid is suspended I a gel so it won't leak out when tipped over! The specifications of a gel lead acid are not only similar to any other lead acids, but also contain the additional caveat of being destroyed if enough overcharging occurs to dry up the gell suspension. How does RenoLogy get it's fully rated capacity from it's gel lead acids, I dunnoh maybe 1/2 rate their battery capacity specs and for example label a 100 amp battery at 50 amps?
 
Last edited:
offgriddle said:
How fo you dump yhr

I don't know how Renogy is supposed to be spelled, but I do know that a gel cell is a lead acid battery, where the acid is suspended I a gel so it won't leak out when tipped over! The specifications of a gel lead acid are not only similar to any other lead acids, but also contain the additional caveat of being destroyed if enough overcharging occurs to dry up the hell suspension. How does RenoLogy get it's fully rated capacity from it's gel lead acids, I dunnoh maybe 1/2 rate their battery capacity specs and for example label a 100 amp battery at 50 amps?
Click to expand...

In my experience, it's very simple. They lie. But I do see similar claims on other gel batteries. And yes, they are sealed and can allegedly be mounted in any position.
 
[AiQUOTE="Lost In The Desert, post: 26770, member: 783"]
In my experience, it's very simple. They lie. But I do see similar claims on other gel batteries. And yes, they are sealed and can allegedly be mounted in any position.
[/QUOTE] The aviation industry likes gel lead acids, they don't leak and are not destroyed in sub freezing temps like lifepoos.
 
[/QUOTE] The aviation industry likes gel lead acids, they don't leak and are not destroyed in sub freezing temps like lifepoos.
[/QUOTE]

That part is definitely true. Mine have been charged down to 18 F (-8C) without issue.
 
I will likely buy the same batteries when I upgrade. Watching the industry and Will's comments very closely, this seems like a bad time to drop several grand on LIP, at least for my application. I think LIP will drop drastically in price over the next couple years as new chemistries become available. There's no reason for them to cost what they do, except that people will pay it. Look at how much they cost just a couple years ago.
 
I’ve seen this type of thread many times and maybe was a contributor to this problem. Good information sent but no one actually simply directly answering the original question. They are emergency use battery’s, No attempt to max cycles is being made. He needs to do the math and spend as little as he can but get the watts he planned for a few cycles during a power outage. Let’s say he wants 2.4kW. If he gets a 200 amp 12 v battery and in an emergency disconnects the BMS and runs it 100% DOD he gets 2.4kW. Can he do this and still have a battery with some use after? I think yes, gel or flooded. Others may say no he needs 3kW batteries run down 80% or the battery will be fried. With a simple answer he would know how much to spend on batteries for emergency back up use only which was the question.
 
Last edited:
Its all at least tangentially related to the original question. It's a conversation.
 
Lost In The Desert said:
I will likely buy the same batteries when I upgrade. Watching the industry and Will's comments very closely, this seems like a bad time to drop several grand on LIP, at least for my application. I think LIP will drop drastically in price over the next couple years as new chemistries become available. There's no reason for them to cost what they do, except that people will pay it. Look at how much they cost just a couple years ago.
Click to expand...
Well, because I'm not a monetarily wealthy man, and because I refuse to succumb to excessive sdebt that is above and beyond the immense and growing nationalized debt that a government gone wild heaps upon the heads of a common core made clueless proletariat majority, I buy my battery capacity a few amps at a time and my solar capacity a few watts at a time. I have discovered that on it's worse day, the performance of my lifepoo's are so above and beyond great gramps's lead acid technology, that it's well worth buying and keeping my lifepoos in an insulated box, in my root cellar, below the frost line. PS: My last twenty Amps of lifepoo cost me $120.00 including the built in BMS. And per our discussion, 20 amps of Lifepo are the same as 40 to 60 amps of grampa's lead acids AND the usable lifespain charge cycles of the lifepo's is calculated to be far greater than grampy's battery. Happy 2020!
 
offgriddle said:
Well, because I'm not a monetarily wealthy man, and because I refuse to succumb to excessive sdebt that is above and beyond the immense and growing nationalized debt that a government gone wild heaps upon the heads of a common core made clueless proletariat majority, I buy my battery capacity a few amps at a time and my solar capacity a few watts at a time. I have discovered that on it's worse day, the performance of my lifepoo's are so above and beyond great gramps's lead acid technology, that it's well worth buying and keeping my lifepoos in an insulated box, in my root cellar, below the frost line. PS: My last twenty Amps of lifepoo cost me $120.00 including the built in BMS. And per our discussion, 20 amps of Lifepo are the same as 40 to 60 amps of grampa's lead acids AND the usable lifespain charge cycles of the lifepo's is calculated to be far greater than grampy's battery. Happy 2020!
Click to expand...

Sounds like they are perfect for your application.
 
Lost In The Desert said:
Sounds like they are perfect for your application.
Click to expand...
Yes, with that being said Lost, I operate another active solar system on property, in that case, the batteries are kept in an unheated shed that can see twenty below zero F, so, in that application I run 200 amps, (yielding at Best 60 to 70 amps) of Trojan flooded lead acids and have been doing so there for three years 24/7/365 without incident. ☮
 
Lost In The Desert said:
Its all at least tangentially related to the original question. It's a conversation.
Click to expand...
True but he had to keep trying to redirect the answers back to the simple question. I learn a ton from these conversations but have to admit they sometimes never quite directly answer the question or if they do you need to pull one nugget from nine replies. What if the first reply said, yes you can in a pinch pull 100% from a battery as you are willing to give up battery life. Don’t even consider doing this with lifepo4s with no BMS or battery low voltage cut off but a lead acid would survive it if it was a rare event. Simple ,clean, answered. Then the thread could get into max cycles, built in BMSs, temp effects etc.
 
You must log in or register to reply here.

Similar threads

H
Will SQF-3, 500ft deep, 800ft of wiring, run off this Anker battery pack?
Replies
18
Views
913
Tomthumb62
Tomthumb62
V
Avoiding sulfation and loss of capacity: How frequently must I charge to 100%?
3 4 5
Replies
116
Views
6K
altenergy20
A
S
Low-budget Project Thread: 23' sailboat with 24v trolling motor and 12v systems / 24v Shed with solar charging.
Replies
23
Views
1K
SparkyGage
S
J
Can I maintain my starter battery with my dc distribution panel?
Replies
3
Views
483
Substrate
S
F
Need help with off grid EV charging system design
2 3
Replies
59
Views
3K
Doggydogworld
Doggydogworld

diy solar

diy solar
Back
Top