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Thread: Help with electric motor battery selection and charging

  1. #1

    Help with electric motor battery selection and charging

    Hey gents,


    Hoping I can get some advice. Iíve just ordered a brand new 510 Stealth Hornet with a Mercury 115HP Pro XS. The next six weeks is going to be the longest wait of my life! Anyway, Iíve been told I should run an 80lb Minn Kota which of course means running a 24v battery system.


    Iíve been looking around and as much as Iíd love to go lithium (LiFePO4) batteries, I donít think think theyíre at a price point I can justify just yet. With that being said, I was looking to run 2 x 120Ah AGM batteries.


    Question #1:


    Is 120Ah an appropriately sized battery for my boat setup? Granted I donít do any offshore fishing so I wont be spending time in any raging currents for hours. I mainly fish, rivers, creeks, estuaries and the odd calm day in the bay. But I will occasionally do a solid 7-8 hours on the water.


    Obviously going to a 24v system I need to get a 24v charger. From what Iíve heard about 12v systems, you need to pick a charger with an amp output at least 10% of the battery amp hour rating. For example, to charge a 100Ah battery, your charger should be able to charge at 10amps.


    Question #2:


    Is this is the same theory with 24v systems? If Iím going to run 2 x 120Ah batteries in 24v, would I need a 24v charger with an amp output of at least 12amps?


    I know I can still charge the batteries separately with a 12v charger but I want to be able to hook it all up, start charging and go to bed, ready to fish the next day.


    Sorry for the novel in advance.


    Cheers

  2. #2

    Re: Help with electric motor battery selection and charging

    Have a look at the Sterling Pro Charge B 12/24 chargers, I have one installed on boat with 2 x 120AH AGM batts, still all good after 3 years, charges whilst outboard is running and then hook up a 12V charger to your starter battery to charge the lot at home.

  3. #3

    Re: Help with electric motor battery selection and charging

    Donno about charging dual batteries in series if one fails while on charge your pumping 24volts into the good 12volt battery....

    the slower the charge to a certain point the better but u dont want to be charging 120ah with 850mah charger for instance a good 4ah charger will work just as good as a 20ah charger it may take longer but it will keep your batteries healthier than a quick charge

    A lot of people charge in the boat for convienence i prefer to take the battery out and charge it place it in the laundry on cardboard as to soak up the tiny droplets of acid that bubble out and if something were to go wrong like over charge or the battery to explode its isolated and no danger to anyone

    Sent from my SM-G900I using Ausfish mobile app

  4. #4
    Ausfish Silver Member GAD's Avatar
    Join Date
    Mar 2006
    Location
    Gordonvale

    Re: Help with electric motor battery selection and charging

    Hi buddy , just bought a 80 lb , 24v Ulterra for my 5.1 TAB's , On Ebay I got 2 x 135amp lthiums for $630 ish a piece free delivery , sounds exspensive till you consider the pro's and cons . Agm batteries can only really supply half the rated amp hours and drawing more than half will cause them to die quickly , having had dual agm batteries in my truck to keep the fridge running and constantly turning them over at the price , even if they are coming down in price . Lithioums are able to draw alot more of their capacity without deterioration and have a much higher amount of charge cycles as compared to an agm . Then the big elephant in the room is weight , 13.7 kg per battery multiply it by 2 = 27.4 kg , Agm batteries are heavy , and 2 x 120ah would weigh as much as me if not more . As for charger well I am not sure yet , still reserching that , was sorta hoping to use the trusty old projecta 50 amp , but unsure as to wether the lithiums require a spacial charger ... I hope that helps a little with your decsion .
    Give a man a fish and feed him for a day , teach a man to fish and feed him for life .

  5. #5

    Re: Help with electric motor battery selection and charging

    The 120amp x 2 will be fine for what you want to do with the Stealth Ö.. nice boat btw.

    24 volt charging options can be very limited & most cheaper options are low output (10amp).

    I went with 2 x Victron blue smart on board chargers 12/25 amp ( you can choose output via the app) - My two batteries are connected via a andersson plug . I just break the connection & charge. For you - these chargers are LiFePO4 compatible if in future you go down this path .

    The advice is that Gels / AGMs & Flooded should only be charged at 10% (approx.). no problems when you have overnight to charge your batteries. I've used 25 amp chargers previously & have had the odd problem including frying batteries with a 25amp Ctek.

    Chris
    Give a man a fish & he will eat for a day !
    Teach him how to fish
    & he will sit in a boat - & drink beer all day!
    TEAM MOJIKO

  6. #6

    Re: Help with electric motor battery selection and charging

    Quote Originally Posted by NAGG View Post
    The 120amp x 2 will be fine for what you want to do with the Stealth Ö.. nice boat btw.

    24 volt charging options can be very limited & most cheaper options are low output (10amp).

    I went with 2 x Victron blue smart on board chargers 12/25 amp ( you can choose output via the app) - My two batteries are connected via a andersson plug . I just break the connection & charge. For you - these chargers are LiFePO4 compatible if in future you go down this path .

    The advice is that Gels / AGMs & Flooded should only be charged at 10% (approx.). no problems when you have overnight to charge your batteries. I've used 25 amp chargers previously & have had the odd problem including frying batteries with a 25amp Ctek.

    Chris
    Cheers for your reply Nagg.

    Yeah I've heard about Victron chargers and I'm definitely going to buy one that's LiFePO4 compatible.

    Just to clarify, you charger is permanently mounted to your batteries inside your boat? Then when you come in after a trip, you break the connection between the batteries and run power to the charger?

    I've drawn up a few wiring diagrams and I think you're running something similar to what I was planning to do.

    Appreciate your time.

  7. #7

    Re: Help with electric motor battery selection and charging

    Quote Originally Posted by GAD View Post
    Hi buddy , just bought a 80 lb , 24v Ulterra for my 5.1 TAB's , On Ebay I got 2 x 135amp lthiums for $630 ish a piece free delivery , sounds exspensive till you consider the pro's and cons . Agm batteries can only really supply half the rated amp hours and drawing more than half will cause them to die quickly , having had dual agm batteries in my truck to keep the fridge running and constantly turning them over at the price , even if they are coming down in price . Lithioums are able to draw alot more of their capacity without deterioration and have a much higher amount of charge cycles as compared to an agm . Then the big elephant in the room is weight , 13.7 kg per battery multiply it by 2 = 27.4 kg , Agm batteries are heavy , and 2 x 120ah would weigh as much as me if not more . As for charger well I am not sure yet , still reserching that , was sorta hoping to use the trusty old projecta 50 amp , but unsure as to wether the lithiums require a spacial charger ... I hope that helps a little with your decsion .
    Thanks for your reply Gad.

    What was the name of the batteries you scored for $630?

    How long have you been using the lithiums for and how how has your experience been so far? I was a little nervous that Minn Kota do warn about the use of their electric motors and lithiums due to their higher voltage. But it also seems like a lot more people are doing it without issue.

    With regards to the charger, you definitely need one that's compatible with Lithium. There's plenty online if you google lithium smart chargers.

  8. #8

    Re: Help with electric motor battery selection and charging

    I'd also like to know more about these as will be up for a couple in the next year. One thing I have found is that older technology gets cheaper while current technology seems to be up there in price.

    I know newer lithium batteries accept a much larger range of chargers. A lot of the cost is actually in the circuitry embedded in the battery the actual cells are really pretty much equal but need very specific care (inbuilt circuitry) to make them last.

  9. #9
    Ausfish Addict disorderly's Avatar
    Join Date
    Sep 2006
    Location
    In the Jungle

    Re: Help with electric motor battery selection and charging

    https://www.evworks.com.au/calb-ca100

    I decided on these ones with a Victron battery monitor with Bluetooth so I can check all the real time parameters on my phone...its nice to be able to see exactly how many amps are being drawn and how much has been used as well as the protection features..

    Works out under $700 per 12v with delivery and the joiner things and I just made a box up with ply..a 36v charger was $180.

    The main reason i decided on these was these appear to be the best bet in that price range...these have been around a while and are used in electric cars, planes and domestic and commercial applications....comparative priced batteries on ebay for examples seem to be some dude just buying a container of the cheapest cleanskin generic batteries form china and slapping a cool sticker on the box...Ö.so dubious quality, backup service and warranty IMO....EV works couldnt do enough to help me as i knew nothing about Lithiums previously..

    Another good feature is you can rearrange the configuration to fit into the space required..i made mine up to perfectly fit in the compartment beside the passenger seat...very neat and tidy indeed, out of the weather with no chance of accidently dropping anything on top..



    IMG_0430.jpg

  10. #10

    Re: Help with electric motor battery selection and charging

    Quote Originally Posted by disorderly View Post
    https://www.evworks.com.au/calb-ca100

    I decided on these ones with a Victron battery monitor with Bluetooth so I can check all the real time parameters on my phone...its nice to be able to see exactly how many amps are being drawn and how much has been used as well as the protection features..

    Works out under $700 per 12v with delivery and the joiner things and I just made a box up with ply..a 36v charger was $180.

    The main reason i decided on these was these appear to be the best bet in that price range...these have been around a while and are used in electric cars, planes and domestic and commercial applications....comparative priced batteries on ebay for examples seem to be some dude just buying a container of the cheapest cleanskin generic batteries form china and slapping a cool sticker on the box...Ö.so dubious quality, backup service and warranty IMO....EV works couldnt do enough to help me as i knew nothing about Lithiums previously..

    Another good feature is you can rearrange the configuration to fit into the space required..i made mine up to perfectly fit in the compartment beside the passenger seat...very neat and tidy indeed, out of the weather with no chance of accidently dropping anything on top..



    IMG_0430.jpg
    That's awesome! So you've just essentially made up your own custom battery using individual LiFePO4 cells from EV Works? What sort of AH is your setup?

  11. #11
    Ausfish Addict disorderly's Avatar
    Join Date
    Sep 2006
    Location
    In the Jungle

    Re: Help with electric motor battery selection and charging

    Quote Originally Posted by JNaumov View Post
    That's awesome! So you've just essentially made up your own custom battery using individual LiFePO4 cells from EV Works? What sort of AH is your setup?
    Yeah in hindsight, despite knowing nothing initially, I made a very good decision by going the larger 36v electric and by going lithium to reduce a bit of weight as I have the equivalent of 6 batteries on board (4 x 12v lithium with 100 useable AH) and 2x 100AH dual purpose and soon a solar panel..we have done 7-8 x 2 or 3 day reef or Hinchinbrook island trips plus the usual day trips in between since I fitted out in mid October last year and never used more than 50% of charge ...we use the electric during the days and anchor overnight...

    Some of my issues with weight and battery capacity in ever changing ocean conditions may not be as relevant to you if you are mainly estuary fishing but wherever you are fishing no one wants to go home early just because the batteries are running low and we all seem to keep adding more gadgets and gear to our boats so weight and balance of the boat is always a consideration as well....

    Its a tough decision as you have laid out a sh!tload of money on the new boat already as I did but after 5 months I feel I made the right decision..I really wanted lithium but didn't want the ebay cheapies and couldn't afford the better brand name ones at double or more the cost..

  12. #12

    Re: Help with electric motor battery selection and charging

    To make the correct decision to ensure maximum life from your batterys requires quite a bit of research.
    First thing if buying on line what is the sellers policy on warranty returns. If buying from interstate the freight can easily come close to the price of a new battery.
    Read carefully the charge voltage and current requirements and see if your charger meets the specifications. For example lead crystal batterys specify a minimum charge current of at leas 30% of the batterys capacity which for a 120a/h battery is 40 amps lifeline batterys specify 30 amps for a 120 a/h battery if your charger does not meet specifications your warranty is void. In many cases you will find that your 25 amp ctek charger does not cut the mustard as I found out with 2 lead crystal batterys that failed after 15 months. All new lead crystal batterys now have a yellow sticker across the terminals warning of this. Mine did not have this and luckily after a bit of too and froeing they were replaced under warranty.
    Cheers Ray

  13. #13

    Re: Help with electric motor battery selection and charging

    All I will say if anyone is considering buying a LFePO4 battery - buy a reputable brand or from a reputable source

    They will cost you more (generally) sometimes considerably more but I've seen photos of inside some of these cheapies & you would be horrified - cheaper polymers used for the cases & cells connected by what appears to be speaker wire. BMS that are basically floating around inside the case .
    I went with Fusion because they have been around a long time / early into the Lithium scene & they are known for their quality . I've been using them for about 16 months now with no issues .

    hindsight - I should have gone bigger than 2 x 100amp (2 x 125amp) would get me through a full days spotlocking - currently I'm only getting 6-7 hrs in typical offshore conditions .

    Chris
    Give a man a fish & he will eat for a day !
    Teach him how to fish
    & he will sit in a boat - & drink beer all day!
    TEAM MOJIKO

  14. #14

    Re: Help with electric motor battery selection and charging

    Quote Originally Posted by JNaumov View Post
    Cheers for your reply Nagg.

    Yeah I've heard about Victron chargers and I'm definitely going to buy one that's LiFePO4 compatible.

    Just to clarify, you charger is permanently mounted to your batteries inside your boat? Then when you come in after a trip, you break the connection between the batteries and run power to the charger?

    I've drawn up a few wiring diagrams and I think you're running something similar to what I was planning to do.

    Appreciate your time.
    Yep - hardwired the chargers - one for each battery & I've incorporated a 30amp breaker for each
    The chargers do draw power (0.5amp from memory) So tripping the breaker eliminates this .

    Charging just involves - breaking the Andersson connection & setting the breakers - plugging into the power source (240 vlt or generator when camping.) I can fit my Honda 2Kva under my front hatch and have used this for overnighters up at Port Stephens when staying out at Broughton Island.

    Chris
    Give a man a fish & he will eat for a day !
    Teach him how to fish
    & he will sit in a boat - & drink beer all day!
    TEAM MOJIKO

  15. #15

    Re: Help with electric motor battery selection and charging

    I've been using 3 x I-Tech 120Ah Lithiums for a while now on 36V MK, Victron 30A 3 outlet charger. Can't fault any of it and I'm a critical bastard.

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