A question for the Lithium battery guys

SkykoSkyko Solar Expert Posts: 121 ✭✭✭✭✭
I know this is not directly related to off grid but I need some advice and you guys have the most experience.

The RV/camper we are building on a Isuzu NRR truck has placed a lot of weight on the front axle. I am trying to put things on a diet and am eying the twin 12V AGM starting batteries that are mounted right behind the front axle (they are connected in parallel to start the 4 cylinder diesel engine). My current batteries are original to the 2006 truck and need replacing anyway.

If I could replace the 120 pounds of batteries with some Lithium option that would still crank the truck in colder weather, it would be excellent. Almost all of that weight would come off the front axle.

I don't know if LiFePO4 has the cranking amps needed. I am actually not sure what the required amps are but am looking up that information. The LiMnO4 might be a better candidate but would I need to build my own out of cylindrical cells?

Thanks for any help.

Comments

  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭
    Re: A question for the Lithium battery guys

    I would go for a LiFePO4 (Lithium Iron Phosphate) battery for this. These are much safer than LiMnO4 technology and should last longer. The downside of LIFePO4 over LiMnO4 batteries is that they are about 1/3 heavier and larger than LiMnO4 but still much lighter than Lead.

    They will have much better cold weather performance and lower internal resistance than Lead based batteries. I would do a little research on the cold weather capabilities of LiFePO4 batteries.

    All lithium battery technologies do not take very kindly to be overcharged or discharged so it is worthwhile checking that your vehicle charging system is suitable. I assume the truck electrics are 24 volt, if so make sure the charge voltage doesn't go above 28.8 volts, 28 volts would be preferable.

    I would be tempted to put some sort of battery monitoring/management system on the battery to make sure it is not overcharged or discharged.

    Another point is that as Lithium batteries have a very low internal resistance so they will charge very rapidly and are very hard on alternators and drive belts, you will need to check that your alternator can cope with this.

    Another very important point is to make sure that there is no 12 volt power being drawn from just one of the batteries. This will unbalance the battery which is not good.

    If you google "truck battery lifepo4", you will get lots of hits.

    I am sure there are other things that I have missed, hopefully PNJunuction will add to the discussion as he is very knowledgeable on twelve volt batteries.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • SkykoSkyko Solar Expert Posts: 121 ✭✭✭✭✭
    Re: A question for the Lithium battery guys

    Thanks karrak.

    The Isuzu uses a 12V system. I guess they thought it needed two batteries in parallel to provide enough cold cranking amps to start the 5.2L diesel engine in sub freezing temps? In warm weather even with these mostly dead tired 12 year old batteries it starts right up.

    Speaking of cold weather, I see the Lithionics 12V drop in solution batteries are not meant for use in sub freezing temps (according to the data sheet). I wonder what tech they use in their batteries?
  • CariboocootCariboocoot Banned Posts: 17,615 ✭✭
    Re: A question for the Lithium battery guys

    Before you invest a considerable amount of money in LiFePo make certain that the batteries you get can be charged properly from the vehicle's alternator and will supply sufficient current to start the engine when it is cold.

    Alternately examine the possibility of putting two large 6 Volt standard batteries in series as opposed to the parallel 12 Volt units. Having worked with both configuration in such an application I can tell you the parallel set-up is more likely to not provide the supposed full cranking current.
  • SkykoSkyko Solar Expert Posts: 121 ✭✭✭✭✭
    Re: A question for the Lithium battery guys
    Before you invest a considerable amount of money in LiFePo make certain that the batteries you get can be charged properly from the vehicle's alternator and will supply sufficient current to start the engine when it is cold.

    Alternately examine the possibility of putting two large 6 Volt standard batteries in series as opposed to the parallel 12 Volt units. Having worked with both configuration in such an application I can tell you the parallel set-up is more likely to not provide the supposed full cranking current.

    Yes. I agree here. I should measure the alternator output voltage at high rpm (well, high for diesel...2600) to see if it is within the range of four LiFePO4 cells. There may be a way to limit this and to limit the charging current so as not to strain the alternator.

    I need to measure the current needed to turn over the engine when it is cold. It is getting cooler and should dip to freezing soon. I really should get a clamp ammeter but I guess I could calculate the resistance of the existing wire between the battery and starter and then measure the voltage drop across that while cranking (I = V/R)
  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭
    Re: A question for the Lithium battery guys
    Skyko wrote: »
    Yes. I agree here. I should measure the alternator output voltage at high rpm (well, high for diesel...2600) to see if it is within the range of four LiFePO4 cells. There may be a way to limit this and to limit the charging current so as not to strain the alternator.

    Try doing this test when the battery is full and not taking much charge. It is more than likely that it will be OK, Japanese electrics are usually well and conservatively designed, and the truck is only eight years old, just something to be aware of. If you can find the make and model of the alternator and see if you can get the specs for it. If it has a thermal safety circuit inbuilt that would be good.
    I need to measure the current needed to turn over the engine when it is cold. It is getting cooler and should dip to freezing soon. I really should get a clamp ammeter but I guess I could calculate the resistance of the existing wire between the battery and starter and then measure the voltage drop across that while cranking (I = V/R)
    Yes that would give you an estimate, how are you going to get an estimate of the resistance? It might be easier if you can you find the manufacturer and model number of the starter motor, then you might be able to get the details on it. Another approach is to check out what the cold cranking current of the current batteries is and use this as a guide. I have no experience using LiFePO4 batteries as a vehicle starting battery but would think that the same guidelines apply as for EV use. I would think that the cold temperature operation is the thing you should be focusing on.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • SkykoSkyko Solar Expert Posts: 121 ✭✭✭✭✭
    Re: A question for the Lithium battery guys

    After doing a bit more research I have decided yet again that AGM is the way to go. Odyssey makes a 65-PC1750T AGM that is 58 pounds and has 1750 amp cranking capacity and 950 amps at -20 C. I don't think I can touch that in a LiFEPO4 without going to very large cells (>100AH) which would be around $500. The Odyssey is $289 shipped.

    Going from two 55 pound batteries to one 58 pound is at least some weight saving.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: A question for the Lithium battery guys
    Skyko wrote: »
    Going from two 55 pound batteries to one 58 pound is at least some weight saving.

    You chose wisely! Awesome battery if treated right. Just make SURE that battery "sees" 14.7v" once in awhile.

    Since your primary issue was one of weight, you scored, even though a lifepo4 bank of say CALB large prismatic cells would do nicely as they are about 1/2 to 1/3 the weight of lead.

    For some additional fun, you may want to see this video, even though it is motorcycle sli specific and not auto - A123 Lifepo4 (inside Antigravity) vs Deka agm
    https://www.youtube.com/watch?v=-nm7bl39uxk

    Thanks Joel W! (one of my main battery gurus..)

    Interestingly enough, the Deka is 12ah, whereas the 16-cell antigravity is only 9.5ah for "real" ah ratings, not the "PbEQ" rating. We'll leave PBeQ to the advrider forum.

    What you see here is how lifepo4 maintains a higher voltage under load as compared to agm, and for much longer. The Deka agm is an excellent battery, and Joel does not trick us by using abused / neglected junk, although he does know how to abuse them when he wishes. He will often take batteries to destruction to document their performance under various conditions. See the chart about 9:44 into the video, and you can see the difference between the discharge slopes.

    However, in your SLI application, the Deka is actually doing what it was designed to do very well, and an Odyssey, being even lower in internal resistance, will hold it's voltage much higher than the Deka under the same conditions. Not to mention that you will most likely not be starting your vehicle 17 times in a row! :)

    Just don't EVER let a generic Schumacher Speed-Charger touch your Odyssey. There is only ONE of them on their approved charger list, and that was from long ago. While their own chargers seem to be built by Schumacher, the internal firmware may be different. That was demonstrated to me when testing my own large Odyssey (A Sears "platinum" - Odyssey rebadge) with a generic speedcharger, and one built specifically for Odyssey - a Sears "platinum" charger. Both were the large wedge-shaped chargers, but only the "platinum" behaved properly and did not go into an overvoltage as measured at the terminals with a Fluke. Just a warning. :)
  • karrakkarrak Solar Expert Posts: 326 ✭✭✭✭
    Re: A question for the Lithium battery guys

    With the current pricing, for starting motors or battery backup I think it is hard to go past good quality Lead technology batteries unless weight is a problem. If they are kept nearly fully charged for the majority of there life Lead based batteries work well. Applications where the power in the battery is cycled is another matter.

    Simon
    Off-Grid with LFP (LiFePO4) battery, battery Installed April 2013
    32x90Ah Winston cells 2p16s (48V), MPP Solar PIP5048MS 5kW Inverter/80A MPPT controller/60A charger, 1900W of Solar Panels
    modified BMS based on TI bq769x0 cell monitors.
    Homemade overall system monitoring and power management  https://github.com/simat/BatteryMonitor
     

  • SkykoSkyko Solar Expert Posts: 121 ✭✭✭✭✭
    Re: A question for the Lithium battery guys

    Yes, I agree that sticking with lead is the way to go on this heavy current draw, shallow cycle application.

    It is too bad that I am scared to use RC LiPo. I could start the engine with 20 ounces of Turnigy LiPo with it's 75C capability.
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: A question for the Lithium battery guys
    Skyko wrote: »
    Yes, I agree that sticking with lead is the way to go on this heavy current draw, shallow cycle application.

    Enersys / Odyssey tppl agm's are one of the best for this application. Other tppl's like Concord and Optima are also worthy candidates. Just take care of them.
    It is too bad that I am scared to use RC LiPo. I could start the engine with 20 ounces of Turnigy LiPo with it's 75C capability.

    Don't be scared - just be safe. My personal favorite for this comes from the Antigravity battery guys, who are in the powersports application, not RC! :
    http://antigravitybatteries.com/microstart/

    You can start a V8 Mustang with something no larger than your back pocket. HOWEVER, you may only get a few charges out of it for your cellphone / tablet, which is there for convenience, and is not it's primary focus. Safety is also a factor in the form of current-limiting mosfets and the like. Something you won't find in a RC DIY project. :)

    The small size implies that it is NOT lifepo4, but another higher energy-dense chemistry such as LiNMC or LiCo02 - I don't what they are actually using. But it points out that it would be crazy to try and build a solar housebank sized system out of these. :) Note that Antigravity's normal line of batteries is actually A123 Lifepo4, finely tuned for capacity and internal resistance. (oh, and NO bms!)
  • ReedReed Solar Expert Posts: 55 ✭✭
    Re: A question for the Lithium battery guys

    The racing motorcycle and dragster crowd seems to be going to Lithium since they want the least weight possible and only have to start the engine for that run (is there some clause in dragster world that the vehicle has to self-start?). However, am quite happy with lead acid for automotive use. And am extremely happy with LFP for full time RV-ing.
    Reed
  • PNjunctionPNjunction Solar Expert Posts: 762 ✭✭✭
    Re: A question for the Lithium battery guys

    The use of lifepo4 demands that one fit it within their application to see if it makes sense. For racers, definitely.

    One example is from the motorcycle world, where new users quickly learn not to undersize their new lifepo4 batteries, because while these small-cylindrical types can pump out a lot of current in a short amount of time, they can quickly die by leaving the radio on for an hour. One reason I never recommend using small-cylindricals for solar housebanks, and stick to the larger prismatics. You can see that kind of guidance here:

    http://www.advrider.com/forums/showthread.php?t=757934

    What helps make it trustworthy is that message #2 contains the sage advice to stick to agm unless you are prepared to make sure your application of lifepo4 fits your bike - not just physically, but operationally. Very important. A very big thank you to _CY_ , who goes to great lengths to explain it all to the bike owners.

    Great info - but again, these are batteries typically filled with high-rate A123 cylindricals, and not the type that we would use, like large GBS, CALB, Winston prismatics.
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