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  • Battery Comparison Chart -- Does This Look Right?

    UPDATE: See v3 in post 14. Old versions removed. -Howard

    Another rally question for the group: what I'm attempting to convey in the chart below (that I'll talk to in the Advanced Solar Seminar at the National Rally) is that 100aH batteries are not all equal. The total usable watts (power available to do work) are not the same. I had to use "guestimates" on some of the LifePO4 voltages so the chart has a consistent % listing.

    Note the load is assumed to be a constant 1.5 ohms (resistive) and voltage for a given percentage is constant for 1 hour.
    Any input? Please don't hesitate if there's constructive criticism-- I'd rather someone here point out a flaw than find out in front of an audience.

    Howard

    P.S. The rest of the battery section of the Advanced seminar is "stolen" from TucsonJim's presentation (with his permission). Jim's battery slides are in the Reference Material of this channel.
    Last edited by howson; 08-06-2022, 11:27 AM.
    Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

    2017 Ford F-350 DRW, '19 315RLTSPlus

  • #2
    How does this relate to calculating battery Wh as voltage x rated amp- hours? Actual available Wh vs rated Wh?

    12.0 x 100 = 1200Wh wet lead acid
    13.0 x 100 = 1300Wh agm
    13.6 x 100 = 1360Wh lifepo4

    Add a place for rated Wh comparison.

    A nitpik: black cell color instead of gray at bottom of agm column.
    Ted
    2021 Reflection 310RLS
    2020 F350 PS,CC,LB,SRW

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    • #3
      howson

      Howard - not sure what the context of this chart is in your presentation, but maybe clarify that this is Wh per charging cycle.

      Just a thought, depending on where you're going with the concept, you could also add another line at the bottom about the Wh over the life of the battery. In addition to the WH per cycle, the LiFePO4 batteries generally have significantly more charge cycles available than the LA/AGM. Like, over 2000 cycles on a LFP vs. maybe 500 on the other technology (assuming not over-discharged). Using your Wh numbers and a guesstimate at lifetime charge cycles:

      LA = 611 Wh x 500 cycles = 305,500 Wh
      AGM = 716 Wh x 500 cycles = 358,000 Wh
      LFP = 1130 Wh x 2000 cycles = 2,260,000 Wh

      Basically, significantly more useable energy out of a LFP for each charge cycle, and dramatically more over its lifetime.
      Ken & Sandra
      2021 303RLS | 2020 F350 Lariat 6.7L 4x4 SB SRW

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      • #4
        howson Howard, I would suggest removing the 10V on the LiPo as a good battery with a BMS should shut down before this. IIRC at 10V bad things happen with LiPo.

        I would say cell voltage of 3.2V is 0% charge (12.8V nominal). In the RC world battery cell voltage range for use is 3.2V - 4.2V (3.2 is actually LOW by some standards).
        Joseph
        Tow
        Vehicle: 2018 GMC K2500 Denali Diesel
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        South of Houston Texas

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        • #5
          Originally posted by TedS View Post
          How does this relate to calculating battery Wh as voltage x rated amp- hours? Actual available Wh vs rated Wh?

          12.0 x 100 = 1200Wh wet lead acid
          13.0 x 100 = 1300Wh agm
          13.6 x 100 = 1360Wh lifepo4

          Add a place for rated Wh comparison.

          A nitpik: black cell color instead of gray at bottom of agm column.
          To the first question: yes. IMHO the reason batteries are not rated in usable WH is because it would be very obvious how superior LifePO4 batteries are. Having all of them rated at "100aH" hides this fact.
          KSC_Travels charge cycle data makes it even more obvious. (I'm going to "steal" that data!)

          In context with the presentation this is an attempt to show that while the initial price is high of a LifePO4, the cost and performance over the long term is something an owner should seriously consider when it's time for a battery. Especially for those who have or are considering solar power on their GDRV.

          What will follow this data slide is Jim's graphic representation--which I think will cement the concept in the viewer's mind. (I hope.)

          Click image for larger version  Name:	Solar 101 Hinkle_Page_09.jpg Views:	0 Size:	63.1 KB ID:	91932
          Last edited by howson; 08-05-2022, 11:21 AM.
          Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

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          • #6
            Originally posted by Jlawles2 View Post
            howson Howard, I would suggest removing the 10V on the LiPo as a good battery with a BMS should shut down before this. IIRC at 10V bad things happen with LiPo.

            I would say cell voltage of 3.2V is 0% charge (12.8V nominal). In the RC world battery cell voltage range for use is 3.2V - 4.2V (3.2 is actually LOW by some standards).
            Thanks, Joseph. I went and double-checked to verify Battle Born's batteries shut off under 10V. https://battlebornbatteries.com/low-voltage-disconnect/ Since 10V (on the chart) represents 0% I believe it's accurate. At least for Battle Born batteries. Other LifePO4's could be different.

            I'll add that caveat to the notes on the slide.
            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

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            • #7
              Version 2 with inputs applied (thanks, guys!)

              More comments are most welcome...

              (Update: Chart had errors so removed. -Howard)

              Last edited by howson; 08-06-2022, 11:26 AM.
              Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

              2017 Ford F-350 DRW, '19 315RLTSPlus

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              • #8
                Really good stuff Howard. On an AGM battery, if you discharge to 50%, you should get approximately 550 cycles. If you only discharge by 20%, you'll get a huge boost to battery life. Here's one source for that info:
                https://www.greenway-battery.com/new...king-1359.html

                Northern Arizona wind and sun has some really good information on various battery chemistries and information. Check out this article for probably more information than you'd ever need:
                https://www.solar-electric.com/learn...of%20Batteries
                I especially like the "mini factoids" at the bottom of the article.

                JIM
                GDRV Forum Moderator
                GDRV SW USA Rally Support Coordinator

                Jim and Ginnie
                2017 Reflection 297RSTS

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                • #9
                  TucsonJim -- thank you! I'll add those references to the "Additional Resources" slide. (No way I can cover all the intricacies of every topic in the time allowed.)
                  Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                  2017 Ford F-350 DRW, '19 315RLTSPlus

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                  • #10
                    This is what Crown sent me. It is showing things a bit higher for their deep cycle like the CR 260 (6V 260 AH) I have 4 in a series/parallel set up.

                    On edit I was told the only real way to tell exact SOC is by specific gravity testing. I have a SG meter and do use it. You might also mention you need to be sure your at 100% SOC before syncing your battery monitor.
                    ProperSetUpCareSLI.pdf

                    Attached Files
                    Last edited by Yoda; 08-05-2022, 01:54 PM.
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                    • #11
                      Yoda -- each specific battery will be a bit different. I'll make sure and mention that the numbers are a generic representation, not an exact value for a given battery. Thanks for the PDF!
                      Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                      2017 Ford F-350 DRW, '19 315RLTSPlus

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                      • #12
                        Originally posted by howson View Post

                        To the first question: yes. IMHO the reason batteries are not rated in usable WH is because it would be very obvious how superior LifePO4 batteries are. Having all of them rated at "100aH" hides this fact.
                        KSC_Travels charge cycle data makes it even more obvious. (I'm going to "steal" that data!)

                        In context with the presentation this is an attempt to show that while the initial price is high of a LifePO4, the cost and performance over the long term is something an owner should seriously consider when it's time for a battery. Especially for those who have or are considering solar power on their GDRV.
                        Hey Howard. You're welcome to it! I did a little more reading on the LFP's and the 2000 cycles is probably very conservative. Battleborn and Renogy both claim up to 4000 lifetime cycles and Lion claims a "minimum of 3500" (i.e. 10 years for all of them). You might consider bumping up the lifetime numbers on the LFP column to (conservatively) 3000 cycles. (1130 x 3000 = 3,390,000 Wh).

                        FWIW, some other benefits that weighed into my decision to go with LFP - ZERO maintenance, BMS protection from over-discharging and damaging the battery (which I have done to several LA batteries in my past), weight & form factor (no ventilation required), long "shelf" storage (no need for trickle charger over the winter).

                        PS - FYI, Renogy's BMS will also shut down the battery at/below 10 Volts.

                        Cheers!
                        Ken & Sandra
                        2021 303RLS | 2020 F350 Lariat 6.7L 4x4 SB SRW

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                        • #13
                          KSC_Travels -- thanks! I was wondering about that since TucsonJim's slide (in his battery presentation) showed higher LifePO4 lifetime cycle numbers.
                          Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                          2017 Ford F-350 DRW, '19 315RLTSPlus

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                          • #14
                            Update--version 3 deleted. See post 19.

                            Final(?) version. I've deleted the previous versions from this thread to avoid them proliferating (along with their errors).
                            Last edited by howson; 08-07-2022, 02:48 PM.
                            Forum moderators are not GD employees--we are volunteers and owners presumably just like yourself. Unless specifically mentioned otherwise, we have nothing to gain should you choose to purchase a product or engage a service we discuss on this forum.

                            2017 Ford F-350 DRW, '19 315RLTSPlus

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                            • #15
                              Lots of info in that chart Howard. Nice job.

                              Jim
                              GDRV Forum Moderator
                              GDRV SW USA Rally Support Coordinator

                              Jim and Ginnie
                              2017 Reflection 297RSTS

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