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  1. #1
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    36 volts lithiums in series. Middle battery not getting full charge.

    I am running 3 50 ah Lithium Pro batteries for my trolling motor. So far this has been adequate battery for the way I fish. Unfortunately the middle battery doesn’t get a full charge. 13.42 versus 14.26 for the other two. I’ve moved my middle battery to the front and it then gets to 14.26 resting voltage after charging. I also moved the charging cables around and it makes no difference. I tried isolating the middle battery when charging by disconnecting the jumpers and it still does the same thing. If I plug the charger back in and “recharge” the middle battery gets to 14.26 resting voltage like the other two. I recently ran out of power and it was the middle battery where the BMS shut it down. The other two read 13.8 volts. Unfortunately since I run a 36v Ultrex I was done for the day. I am using an almost new Noco GenPro x4 on the lithium setting for charging. Other than buying a 36 volt battery and 36 volt charger (what Lithium Pros recommended) can anyone explain what is going on here and a potential work around? Based on the lights on the charger it appears the middle battery in the series gets more fully discharged than the other two and then doesn’t charge to full capacity. It seems to me where the issue exists is the way the charger is programmed but I am no electrical engineer. I have not yet measured the voltages at the end of the day but am going to do that.
    Last edited by Amistad Tackle; 05-27-2023 at 01:12 PM.

  2. Member 78Staff's Avatar
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    #2
    I would be looking at the charger vs replacing the batteries - it appears you've done you due diligence in isolating both battery and wiring, only thing left is the charger. The PP Charge had an issue with middle batteries in some cases in the past, but the fixed it with a firmware upgrade. If possible to try a different charger that would be my next step. I know most folks don't have an extra charger laying around, but maybe a shop has one you borrow or even rent to see if any difference. I have spare MK PC on shelf as backup, if you were close I would let you try it, maybe a buddy near you has one you can borrow?

    Acutally, I do recall a post recently regarding Noco's and it was suggest to use the AGM setting vs the Lithium setting for lithium batteries - maybe try that first and see if it resolves the issue...

    EDIT - here's the post - it refers to IONIC brand, but I think it maybe be the cell type more than the actual brand.

    (for those that have been using the noco on lithium with no issues you may be fine ) but those chargers are very inconsistent and and tend to cut off a little early on the top end , AMG will top them off a little higher and better balance the cells

  3. Electrical/Wiring/Trolling Motors Moderator CatFan's Avatar
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    #3
    Assuming the wiring is right, all three batteries will discharge the same amount during use. It can’t vary.

    And you pretty well proved its not a charger issue.

    Resting voltage for Lithium Pro batteries is 12.8V, so all of your batteries are above the point where they are fully charged.

    How are you getting those voltages? If it’s the battery reporting it, I’d verify with a meter on the battery terminals.
    If you have integrity, nothing else matters. If you don't have integrity,
    nothing else matters.​

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    #4
    I am getting my readings from a voltage meter at the battery terminals. Charts I have seen for lithium 12 volt batteries list 13.6 as 100 percent resting and 14.6 as 100 percent charging (eg. https://cleversolarpower.com/). The readings I supplied above are after the batteries have sat off charge for 48 hours. The very knowledgeable technical support man at Lithium Pros did tell me their batteries could be charged with an AGM charger but didn’t indicate this would charge the middle battery any differently. He also told me they no longer recommend 3 12 volt batteries in series to get 36 volts for the exact issue I have. He said he had a guy in there that morning that had the same problem using the Tracker brand lithium batteries. He also knew before I told him it was the middle battery that cut off. He could not tell me why this occurred. His solution was to buy a 36 volt battery and charger which I may have to do if I run out of power consistently and sell the batteries I have.

    ….and the 13.8 voltage I listed above when the middle battery went dead I must be mistaken. Probably 13.2. Been about a month since this occurred.

    ....and the battery they sold me last May to run in series is now what they recommend for kayaks TM2450 12.8V 50Ah Lithium Ion Battery (lithiumpros.com). I am a little confused as to how a 50AH Lithium Pro is any different than a 50AH other brand lithium that is being heavily marketed for running in series (24 or 36 volt) for bass boats.

    ....and thanks for the BBC discussion link to the Ionic charger recommendations.

    A lot of nuances to these batteries. I could go back to lead acid but at 62 yo I dread lifting those in and out of the boat. I really like the lithiums just for that.
    Last edited by Amistad Tackle; 05-27-2023 at 06:28 PM.

  5. Member bhjr.'s Avatar
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    #5
    You might need to switch to the AGM setting on your charger. This is a tried and true fix for some situations. This is per Drew from Drewtec, a board member and sponsor for Iconic batteries.


    Sorry, didn’t see that this has been recommended already. Good luck anyway!

  6. Member
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    #6
    Thanks. Going to give that a try.

  7. Member
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    #7
    I don't have lithium pros but my lithiums are charged with power pole charge and they are fully charged at 13.8 volts. After a solid day of fishing they drop to 13.3 volts.

  8. Member
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    #8
    After two charges it appears the switch to the AGM mode worked. All three now charge to the same voltage. If someone has a good explanation why I would like to know.

  9. Member 78Staff's Avatar
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    #9
    It's explained in the post I linked i believe, but essentially I think some Noco's dont' fully charge up to the correct spec for Lithiums even when set for that type - the AGM has that little bit of extra charge to get them up to full charge.

  10. Member lpugh's Avatar
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    #10
    All three lithium batteries must be identical, no deviation allowed..
    Thank You Leon Pugh

  11. Member
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    #11
    Thanks. I was looking for a more technical explanation. Something is different in the charging profile. Thought maybe there was an electrical engineer on here that could shed some light on it. You would think with a lithium battery you would use the lithium setting but Ionic recommends the AGM setting and Lithium Pro said I could use it.

  12. BBC SPONSOR / PHOENIX MOD DREWTICK's Avatar
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    #12
    almost every brand of lithium may work ok with a generic charging profile but each one can perform better with the right profile, DualPro has 5 different profiles for reprograming SS and PS chargers but they have one called the NaNo thats generic to all which is similar to what they used in the new PS Auto, the NOCO works on IONICs on Lithium about 80% of the time but 2 out of 10 chargers will not work unless you use the AGM, they are not consistent.
    also have seen a noco charge to 14+ volts on 3 banks and 13.1 on the 4th bank , or going to the AGM setting 3 banks charge perfect and one throw a high voltage code
    we sell lots of the Gen Pros but and they are built great but very inconsistent from one charger to the next or one bank to the next specially on the lithium setting , I recommend AGM for any lithium unless you see high voltage then back up to the lithium
    Drewcraft Specializes in Lithium Batteries and Chargers, We carry all Brands of Trolling Motors and Graphs, Minnkota, Lowrance, Garmin, Motorguide
    910-722-0001 call or text
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