Battery & Solar Panel Question (2 Viewers)

[Broski]

Where did you find your CCA to AH capacity calculation reference? Please provide a link.

Ability to provide 1000a of "cold cranking amps" says basically nothing about the total capacity of a battery, only that it has enough capacity to provide 1000a of "CCA" for the 15 seconds or whatever that test duration is.

Agm/lead acid battery manufacturers don't typically specify their battery product's true AH (amp hour) or WH (watt-hour) capacity, which means we have to work back their capacity using real numbers. CCA and RC (reserve capacity) are tough to work back to WH or AH in my experience.

CCA to AH Conversion - How to Convert it (Step by Step Guide) - A New Way Forward | Automotive and Home Advice & Review

If you are planning to purchase a new battery for your car, you are definitely going to be needing a whole lot of research before you bump into a good choice. However, when it comes to the specifications of a battery, things don’t stay simple anymore, and there is a lot that just flies over […]

anewwayforward.org

Jmack must have used some calculation to come up with 92HA

 

[GLTHFJ60]

CCA to AH Conversion - How to Convert it (Step by Step Guide) - A New Way Forward | Automotive and Home Advice & Review

If you are planning to purchase a new battery for your car, you are definitely going to be needing a whole lot of research before you bump into a good choice. However, when it comes to the specifications of a battery, things don’t stay simple anymore, and there is a lot that just flies over […]

anewwayforward.org

In that doc, it explains that there is NO correlation between CCA rating of the battery and it's AH capacity. The table screenshot below breaks their own rule of thumb, and they state that fact.

Perhaps you can get a rough estimation with a straight divide, but it's no where close to a definitive result. You need to find a battery specification from a manufacturer, either in watt hours or amp hours, or some other quantifiable test to work back from, to figure it out. Using this X2 power battery as an example, they state 840CCA, and a 77AH capacity. The rule of thumb from that site says this battery should have ~115AH of capacity, but it doesn't.

X2Power Premium AGM BCI Group 24 Car and Truck Battery - SLI24AGMDP at Batteries Plus Bulbs

X2Power group 24 AGM replacement battery designed for low maintenance and dependable engine starting power. Designed for Volvo, Pontiac, Subaru, Dodge and more

www.batteriesplus.com

Point is, you cannot convert from CCA directly to AH. If you want to know how to figure out the usable battery capacity of a battery you already have, you can conduct a discharge rate test, and calculate how many watt-hours (then amp-hours) from that:

How to calculate battery run-time when design equipment using batteries; Battery Technical Resources for Design Engineers from PowerStream

How long will a battery last calculator,AH to Watts and watt-hours, battery capacity, how to calculate battery life, run-time calculation Resources for designing equipment using battery packs from PowerStream

www.powerstream.com

 

[J Mack]

Again I am no expert, But was curious how you got 92 AH from the Odyssey

From Odyssey ODX-AGM31M (31M-PC2150ST) ODYSSEY Extreme Series Battery | ODYSSEY® Battery - https://www.odysseybattery.com/products/odx-agm31m-battery-31m-pc2150st/

I’m giving ODYSSEY a lot of credit and believe they are among the best in the business.
AGM batteries have roughly 50 percent rated capacity as usable capacity without permanent battery damage and ODYSSEY can’t change that.

 

[Broski]

In that doc, it explains that there is NO correlation between CCA rating of the battery and it's AH capacity. The table screenshot below breaks their own rule of thumb, and they state that fact.


View attachment 2676489


Perhaps you can get a rough estimation with a straight divide, but it's no where close to a definitive result. You need to find a battery specification from a manufacturer, either in watt hours or amp hours, or some other quantifiable test to work back from, to figure it out. Using this X2 power battery as an example, they state 840CCA, and a 77AH capacity. The rule of thumb from that site says this battery should have ~115AH of capacity, but it doesn't.

X2Power Premium AGM BCI Group 24 Car and Truck Battery - SLI24AGMDP at Batteries Plus Bulbs

X2Power group 24 AGM replacement battery designed for low maintenance and dependable engine starting power. Designed for Volvo, Pontiac, Subaru, Dodge and more

www.batteriesplus.com

Point is, you cannot convert from CCA directly to AH. If you want to know how to figure out the usable battery capacity of a battery you already have, you can conduct a discharge rate test, and calculate how many watt-hours (then amp-hours) from that:

How to calculate battery run-time when design equipment using batteries; Battery Technical Resources for Design Engineers from PowerStream

How long will a battery last calculator,AH to Watts and watt-hours, battery capacity, how to calculate battery life, run-time calculation Resources for designing equipment using battery packs from PowerStream

www.powerstream.com

Thank you

 

[Broski]

From Odyssey ODX-AGM31M (31M-PC2150ST) ODYSSEY Extreme Series Battery | ODYSSEY® Battery - https://www.odysseybattery.com/products/odx-agm31m-battery-31m-pc2150st/

I’m giving ODYSSEY a lot of credit and believe they are among the best in the business.
AGM batteries have roughly 50 percent rated capacity as usable capacity without permanent battery damage and ODYSSEY can’t change that.

My Bad, I don't know how I missed that.

 

[GLTHFJ60]

All good man, it's hard to sort through all the bad and/or misleading info that's out there!

To reiterate what Jim was saying, because this is the key advantage of LiFePO4 arrays, is the *usable* battery capacity. A lead acid chemistry battery (flooded, agm, spiral) can only provide 50% of it's rated AH capacity before you get into the voltage range that causes damage to the plates in the cell. A LiFePO4 array can provide 95-99% of it's rated capacity before the cell voltage drops too low.

What this boils down to, is if you have 100ah of capacity in a LiFePO4 array, and your buddy has 100ah of capacity in a lead acid battery array, both with the same fridge, you can run your fridge for twice as long as he can before you need to recharge. It's pretty amazing.

 

[J Mack]

you can run your fridge for twice as long as he can before you need to recharge. It's pretty amazing.

I’ll only add that the Li batteries we are talking about will have a BMS that protects your battery and you would expect to get 1000’s of charge and discharges before you would derate the battery.

AGM batteries do not have built in protection and one discharge below the threshold and you’ve done irreversible damage and you’ll need to derate your Ah usage or you will continue to damage the battery more. AGM batteries are rated at 100’s of charge/discharge cycles under ideal conditions, LiFePO4 will be in the 1000’s making it better for running the loads we are talking about here.

 

[scrapdaddy]

Good info guys! I have to figure out something in the near future.

 

[Broski]

I’ll only add that the Li batteries we are talking about will have a BMS that protects your battery and you would expect to get 1000’s of charge and discharges before you would derate the battery.

AGM batteries do not have built in protection and one discharge below the threshold and you’ve done irreversible damage and you’ll need to derate your Ah usage or you will continue to damage the battery more. AGM batteries are rated at 100’s of charge/discharge cycles under ideal conditions, LiFePO4 will be in the 1000’s making it better for running the loads we are talking about here.

Thank you for sharing your knowledge. And apologies for my ignorance.

Also at approximately what point of discharge is the irreversible damage done to the AMG batteries

Thanks RB

 

[GLTHFJ60]

Thank you for sharing your knowledge. And apologies for my ignorance.

Also at approximately what point of discharge is the irreversible damage done to the *AGM* batteries

Thanks RB

~11.6v is the point at which you need to stop discharging lead acid chemistry batteries (including AGMs) to prevent damage.

Low Voltage Cut-off information

A Note about Deep Cycle Batteries and Low Voltage Cut-off

www.kendrickastro.com

 

[Megadoomer]

This is a good thread as well as the timing. I was going to run a Optima Red top for starting on the passenger side and a Yellow for accessories on the drive side. After building my inner fenders and placing a few other goodies I wont have room for the yellow top. Going with the LiFePo4 gives an option to put in the vehicle and doing an array I could possibly get more smaller batteries and put them under the back seat.

I don't really need a system right now but the Yellow top was going to be a free gift from work. I don't have a fridge but it's only a matter of time. Really all I want it for my CPAP to work thru the night while camping. Maybe the Lion Safari does that for me. Just kinda spendy.

 

[J Mack]

The dual-purpose batteries have massive starting power, along with amazing deep cycling capability—up to 400 cycles at 80 percent depth of discharge

~11.6v is the point at which you need to stop discharging lead acid chemistry batteries (including AGMs) to prevent damage.

I would test it on the conservative side taking it to 80 percent depth of discharge and work your actual Ah for your setup and not chance going all the way down to 11.6V and using that as my base line if this is also used as your starting battery.

 

[Megadoomer]

It is also good timing for work. We use yellow tops to run our equipment and we have been having issue. My guys would say "we used to run this for 2 days without a charge and now it doesn't last." Well crap. After reading all this and then getting the first part of my Google degree in batteries, I know why. I might be moving our crews to some 40AH lifepo4s as the yellow tops poop out. They can be cheaper and it just makes more sense for our work. Thanks sty!

 

[GLTHFJ60]

Relevant video about longevity of LiFePO4 arrays:

 

[scrapdaddy]

I just came across Will Prowse a couple weeks ago, learning a lot from him.

 

[Franknozly]

Thanks man! Good to hear from you!

The thing that got me excited was the $589 was for the battery in a smart box, plus the solar panel. It looked like a nice little promotional price.

So divide the 450 WH by 12V to get the 37.50 Ah, eh?

My fridge specs have 2 line items that interest me:

• Average power consumption = 40 watts <- this equals 3.33 Amps @ 12V, eh? If I am on the right track, the Lion box could run the fridge "on average" for 12 hours w/ no solar panel plugged in, yes?
• Current draw on 12 volts = ~0.7 Ah/h <- is this amp hours/hour?

Obviously the 0.7 Ah/h sounds fine if the device puts out 37 Ah. But I think there is a big difference in draw between compressor start up vs. just keeping the compressor running after it has started. If it can take that start up draw, I think this might be a good solution to let me move the fridge around between vehicles and keep stuff cold if we are not moving for a day or so...

It's much simpler than that...
A 450 Wh battery with a load of 40W is calculated as 450Wh / 40W = 11.25 hours.

Watt hour means if you ran a 100W light bulb for an hour, it would be 100Wh. It's how electricity is typically measured in, it's what your electricity bill gets calculated with (kWh).

 

[Franknozly]

It's much simpler than that...
A 450 Wh battery with a load of 40W is calculated as 450Wh / 40W = 11.25 hours.

Watt hour means if you ran a 100W light bulb for an hour, it would be 100Wh. It's how electricity is typically measured in, it's what your electricity bill gets calculated with (kWh).

Also 40W seems high. Maybe it's a poorly made fridge...
If you check out this post on an Iceco fridge, over 24 hour period, it averaged about 10.8W.

April 2022 rolling out now: check 1st post. 3 Models 25% so far.

This is a great thing you've organized here. Thank you for the kind words brother, i really appreciate it! @Owyhee Jackass Sorry it took a while and seems you figured it out. For everyone else, all of their fridges are BOTH 12V and 24V compatible, as well as BOTH 110v and 220V compatible. You...

forum.ih8mud.com

 

[bobm]

My Brain don't work that Good