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  • Charging a lithium battery

    I would appreciate advice from those who have upgraded from an AGM to a lithium battery, as to how you now charge the lithium. The reason I ask is because the dcdc controller I have had for 5 years (its otherwise been great) doesn't have lithium as a charging option in the setup. Am I right that the lithium batteries usually come with their own BMS and, if so, does that mean you can choose, say, a wet cell or AGM setting to recharge?

  • #2
    Hi Mundy55,

    LIthium batteries do have an internal BMS but from what I can understand that's mostly for cell balancing and under/over voltage protection. Lithium batteries operate on different voltage ranges than do Lead acid or AGM. Accordingly the charging algorithm is also different and targets different voltage points for the battery.

    A Lithium charger typically has two charging phases:

    1. Constant Current - the voltage will rise up to a predetermined point (say 13.7v). Some might be higher - up to 14.0v
    2. Once the threshold voltage is reached, the charger will move to constant voltage and the charge current will gradually reduce until the battery reaches 100% charge.

    Note these voltages are off the top off my head so don't shoot me if you see something a little different on your battery. There are some differences from different Lithium batteries and different chargers.

    As a Lithium battery discharges, the voltage range will stay 13.2V - 13.5V with the voltage staying flat up to 90% discharge and then rapidly reducing until 100% discharge when you might see it approach 12.5V. For most typical lifecycles you should not see your battery voltage go under 13V. I occasionally see my Enerdrive Lithium battery dip below 13V but only under high load (e.g. 100A from my coffee machine) but will then recover. The actual discharge curve will be different across different batteries, but you can assumes it is generally flat, whereas you would see an AGM vary from 12.8V fully charged with a discharge curve getting down to maybe 11.9V when fully discharged.

    Given the voltage rarely drops below 13V, a typical Lead acid charger will not trigger its bulk charging phase for a Lithium battery and as a result the battery will not charge. Also the other voltages used by the usual Lead acid charges are not compatible with the operating voltages of Lithium batteries.

    I have seen some Lithium battery suppliers (e.g. Fusion) claim you can continue to use your AGM charger, but you would need to look at it closely. given the cost of Lithium batteries, you are risking damage and as I said above you may not get your charger to charge your battery in any case.

    For my current Lithium, I use a full set of Enerdrive chargers. For my previous Lithium (Fusion) in my old van, I used a Redarc Lithium compatible DC-DC charger. I didn't ever bother to change out my old Electroparts AC charger as I relied on the car or Solar to keep the battery charged. Both batteries were 200AH.

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    • #3
      Agree with Pajadmin.

      I have replaced my AGMs with 2 x 100ah Revolution LiFePO batteries. Prior to actually buying them (big investment!) I asked Redarc whether my existing 1240LV BCDC would still be ok. Nup. Needed a newer version with a lithium profile. I decided to get the BMS30 which integrates the DCDC/solar charger with a 240 volt charger, so I never really found out whether my Ctek Marine 200 240v charger would have been ok. A colleague on the camper forum I belong to recently re-equipped with iTech LiFePOs. These apparently have some extra smarts in addition to the cell-balancing and overloading circuits. They claim you can use existing DCDC chargers (ie ones without specific Lithium profiles). He had a 1225 Redarc BCDC (no lithium profile) and he couldn't get it to work, even after following the battery vendor's suggestion of using the slightly higher Gel setting. His existing Ctek 200 240v charger did charge the new LiFePOs, but apparently it was getting hotter than he was used to when he was charging his old AGMs. Anyway, Redarc told him he would have to upgrade his BCDC.

      My take home from this is to select your battery, but before buying it talk to Redarc or Enerdrive or Projecta or whoever your favourite charging system vendor is, and get them to advise on exactly what you will need to charge your specific lithium battery from 12v, 240v and solar sources. Changing over to lithium is an expensive business and you want to get it right first time, before you lay down your hard-earned.

      Also, following on from Pajadmin, with lead acid or AGMs you could do an approximation to SOC by just measuring the voltage across the battery terminals and using a nomogram or table to get a rough idea of the % charge left. If I remember correctly by the time you were down to 12.3v you were at about 50% charge and you'd want to start thinking about recharging. Because of the flatter discharge curve of the lithium, you can get nice high voltages for a long time while hidden away your SOC is dropping, and you don't get much warning until the terminal voltage plunges. So to manage lithium you really need a better way to track SOC, like a bridge and SOC gauge, not just your trusty multi-meter.
      BY13/MY14 Pajero NW GLX Auto, Cooper ST Maxx, factory towbar, Drifta drawers, SmartBar, Airtec snorkel, Koni 90 front and Bilstein 6272 rear shocks with Lovell HD springs, Brown Davis i/c, sump and transmission bash plates, Piranha diff breathers, Fuel Manager pre-filter, LRA 81L auxiliary fuel tank, Piranha steel battery tray, Sherpa 9500 lb winch, HPD catch can, LockUp Mate, Kaon cargo barrier, Harrop front e-locker, DBA T3 rotors and Xtreme pads, Mark's 4WD reduction gears

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      • #4
        So what's with all this 'Drop in replacement' talk of many Lithiums?
        I assume that the BMS takes care of everything, all you need is something with a bit of voltage and current capability connected up?
        In this case maybe the 'dumber' the charger the better?
        2014 NW MY14 3.2 DID GLX-R Auto. Champagne in colour!
        MM Lockup mate. King KCRS-35 rear springs. Monroe Gas Magnum TDT rear shocks. 3M color stable tint all round. Spare wheel lift kit. 'Dynamat' in all doors. Pioneer AVH-Z5150BT Head Unit. Upgraded Speakers. Rear USB outlet. Factory nudge bar with LED light bar. Provent catch can. LED interior lights.

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        • #5
          As an early adopter of Lithium batteries some 9 years ago, and selling a kidney, I will share what happens with my system.
          Each cell of each of the 2 lithium batteries has an inbuilt BMS that manages both discharge and recharge to protect and balance the individual cell. When the batteries are recharged in the vehicle using a conventional alternator or a SLR/AGM external battery charger, the lithium's never achieve a full recharge to for theoretical capacity. No damage is done to the batteries, simply the capacity of the system is reduced.

          I would be taking advice from the battery manufacturer on the specific operation and capabilities of the BMS.

          OJ.
          2011 PB Base White Auto, Smartbar, Cooper STMaxx LT235/85R-16,TPMS, HR TB, 3 x Bushskinz, front +40mm Dobinson , rear +50mm EHDVR Lovells, Dobinson MT struts and shockers, Peddars 5899 cone springs, Windcheater rack, GME UHF, Custom alloy drawer system inc. 30lt Engel & 2 x 30 AH LiFePo batteries + elec controls, Tailgate hi-lift/long struts, Phillips +100 LB & HB, Lightforce 20" single row driving beam LED lightbar, Scanguage II.
          MM4x4 Auto Mate, Serial No 1 .

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          • #6
            I,ve got 2 x 120 Itech lithium's in the camper, 1 x 120 Itech in the rear of the Paj as well as a 100 amp Renogy as a portable power box for around camp. I use a dedicated dc/dc for both vehicles and also have Victron solar regs for both systems. The Victrons are lithium compatible. I also carry a Enerdrive 240 volt 40 amp charger. I don't take any chances with cheap units and the "drop in " replacements might be ok. I prefer dedicated units designed specifically for the unit it is designed for. Lets face it...spend good dollars for quality gear and your seldom disappointed.
            Dicko. FNQ

            2014 NW with all the usual stuff plus more.
            If you take life too seriously you will never get out alive....



            Telegraph X camper

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            • #7
              I converted my caravan from AGM to Lithium and I wasn't about to risk a $1500 battery using a charger that didn't have a Lithium profile, so I updated my solar & 240v chargers to Victron with Lithium profiles.

              My understanding is that the "drop in" Lithiums will work fine on an AGM charging profile but you will shorten their life. Lithiums use a constant voltage/constant current 2 stage charging profile and don't like a float stage like AGM.

              In my caravan I only charge the battery to about 90% on solar with an occasional 100% charge from 240V. When not in use, I run the battery down to about 50% and turn everything off.
              Warren
              2012 NW DiD Activ

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              • #8
                Thats another difference to think about with storing lithium or leaving for long periods of non use. While an agm would like a trickle charge, lithiums are best left at 50-70% of capacity when stored. On my Renogy I also have the ability to shut the battery down so even if you connect anything it wont wake up until signaled to.
                Dicko. FNQ

                2014 NW with all the usual stuff plus more.
                If you take life too seriously you will never get out alive....



                Telegraph X camper

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                • #9
                  Thanks for all the responses. I am not quite an early adopter, usually. I've used AGMs for a couple of decades without any issues but like the idea of the Lithiums. So, I'm not sure, for me, the somewhat marginal increase in usability and battery life are worth the cost, not only of the battery but also the charger. My 5 year old Intervolt Pro dcdc charger has been a great unit and I'd would not like having to just dump it. Thanks again, great info.

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                  • #10
                    I’ve had my Lifepo4 for nearly 7 years now, and for about 5 of those I used an old model Redarc BCDC 1225-LV with no lithium profile and set on the Gel setting. I found it wouldn’t drop into boost mode by itself as the Lifepo4 doesn’t have the same drop in voltage as a Gel, and the Redarc wouldn’t know it had to switch to boost mode.

                    My solution was a switch so I could fully disconnect the charger from the system and then reconnect it. Did the trick but a couple of years ago I changed out to an Enerdrive EN3DC40+. Much better now, just set and forget.

                    I suspect my battery is showing it’s age now as I don’t seem to be getting the same amount of usage from it, so I’ve got a Lifepo4 battery tester on the way from Alibaba to give it a capacity test. Either that or my fridge is just a power hungry beast.
                    Last edited by stevemc181; 16-02-21, 09:52 AM.
                    2012 NW Activ with all the fruit, stripped what I could for my new build and handed over to the Mrs as a daily driver.

                    Current vehicle: 2016 Y61 GU Patrol Legend series Auto, (Last of the Breed)
                    3505kg GVM Upgrade and 2" Lift | Warn XD 9000 Winch | Factory steel bar, towbar, snorkel, alloy roof rack | 285/70/17 (33") Mickey T ATZ P3's | 3" Manta Exhaust | ORS Drawer System | Manual Boost Controller | ECU Remap |

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                    • #11
                      Originally posted by Mundy55 View Post
                      Thanks for all the responses. I am not quite an early adopter, usually. I've used AGMs for a couple of decades without any issues but like the idea of the Lithiums. So, I'm not sure, for me, the somewhat marginal increase in usability and battery life are worth the cost, not only of the battery but also the charger. My 5 year old Intervolt Pro dcdc charger has been a great unit and I'd would not like having to just dump it. Thanks again, great info.
                      Why? Unless you have a specific need why change to Lithium? I changed to Lithium in my caravan to save weight but still run AGM in my car. An AGM, Gel, etc., battery is simply with no BMS or other electronics to worry about. Basically hook them up and go. KISS. Lithium can also limit you on high current draw items like inverters. So unless you need to change, stick with AGM.
                      Warren
                      2012 NW DiD Activ

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                      • #12
                        Originally posted by 2bad4u View Post

                        Why? Unless you have a specific need why change to Lithium? I changed to Lithium in my caravan to save weight but still run AGM in my car. An AGM, Gel, etc., battery is simply with no BMS or other electronics to worry about. Basically hook them up and go. KISS. Lithium can also limit you on high current draw items like inverters. So unless you need to change, stick with AGM.
                        Why? Mainly because I could have a much greater capacity battery without the size or weight of an equivalent AGM. KISS? KIS yes, but the extra S is a bit pejorative . Still, my current AGM is 5 years old and whilst not quite the same capacity as new, is still doing well. So, good VFM I guess.

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                        • #13
                          Originally posted by 2bad4u View Post
                          I converted my caravan from AGM to Lithium and I wasn't about to risk a $1500 battery using a charger that didn't have a Lithium profile, so I updated my solar & 240v chargers to Victron with Lithium profiles.

                          My understanding is that the "drop in" Lithiums will work fine on an AGM charging profile but you will shorten their life. Lithiums use a constant voltage/constant current 2 stage charging profile and don't like a float stage like AGM.

                          In my caravan I only charge the battery to about 90% on solar with an occasional 100% charge from 240V. When not in use, I run the battery down to about 50% and turn everything off.
                          FWIW my lithiums charge off power supply mode which turns off that chite smarts that are a problem at times. They charge perfectly fine. The main ingredient that constitutes a "lithium profile" is simply the end amps style absorb timer. All lithium chargers are really just lead acid with marketing. A real lithium specific charger would actually communicate with a good battery monitor and have a proper top balance feature, precise voltage control, dedicated volt sensing etc...let me know when you find that charger.... To cycle a lithium properly in a daily setting requires extra stuff like relays, side lead acid batteries. Long story.

                          you can shorten the life using an AGM profile mainly because the absorb timer is too long or you keep hammering it with high c rates in hot weather, the voltage is rather meaningless without duration unlike AGM as lithium have such over absorbing quality and so the voltage must be taken into account with the c rates too.

                          lithium actually use 3 stage for proper charging , not 2! Lots of confusion it's sad really and shows people don't understand the basics of electricity.
                          the belief that they dont like floating is about as unsound as the 50%DOD lead acid rule, floating can mean many things, the guys who say its bad are zellots looking to get 20years out of their cells, for them it's like 'well, you never know what might happen' when you put 2cells in parrelle you are floating them...the big misunderstanding is you must float a lithium at the RIGHT voltage at the RIGHT time and place.

                          I charge my lithiums to near 100% as to not be wasteful, but in a every day living on the road situation 90% is a good sound practice given how in real life most people never get anywhere near the cycle life.


                          to test the capacity all you need is some 12v lights or a heating element on the inverter. My 125 to 160ah lithiums use 4x130watt 12v bulbs drawing 37amps at 13 2v all wired into one anderson plug lol. Count the ah with victory bmv and you will get a very accurate capacity. Min .1C is needed and those Alibaba testers are absolute rubbish! They burn out so easy and cant reliably run anywhere near their advertised wattage.
                          2000 NM Exceed Auto V6 3.5

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                          • #14
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                            Dicko. FNQ

                            2014 NW with all the usual stuff plus more.
                            If you take life too seriously you will never get out alive....



                            Telegraph X camper

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                            • #15
                              I had assumed most lithium batteries destined for in vehicle use would come with a BMS which allowed the now usual smart alternators to charge the battery. Given that smart alternators provide varying voltage from 13V to 14V typically, I can't for the moment understand why a smart dcdc charger on any of the settings, power, gel or agm, wouldn't charge the lithium battery.

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