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Thread: Best Setup to Charge Batteries on Board

  1. #1

    Best Setup to Charge Batteries on Board

    I have very basic knowledge on all things electrical so hoping experts here could help out. What's the best and most efficient setup to charge 1x start, 1x AGM deep cycle house and 1x 36V (or 3x 12V in series) LiFePo4? I'm hoping to prioritize engine alternator and possibly solar (1 panel on hardtop), and only using 240V charger for the lithium as a backup. Can lithium be used to start in event of an emergency? Thanks.
    It has always been my private conviction that any man who pits his intelligence against a fish and loses has it coming. ~John Steinbeck

  2. #2

    Re: Best Setup to Charge Batteries on Board

    Use a VSR (voltage sensitive relay) panel from BEP to prioritise charge to your starter then to your house battery. This panel includes an emergency parallel switch to link the house battery if the starter battery goes flat.
    Use a 12-36V DC to DC charger from house to lithium if you want to charge the lithiums in the boat - ensure it has a low voltage cutoff so the house battery is not completely drained if the engine isnít running.
    I wouldnít use the lithiums as an emergency start - most arenít rated for starting current. You could potentially manually connect them in a parallel configuration in an emergency but youíre better off just buying a small emergency starter from Repco or somewhere if youíre worried youíll flatten both the starter and house battery.

  3. #3
    Ausfish Platinum Member
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    Kalbarri, WA

    Re: Best Setup to Charge Batteries on Board

    Be careful if you want to charge on the fly with a 12-36v DC-Dc charger for a spotlocker. I've been looking into this for quite a while, and have decided it's just not worth the effort. My useage would include a lot of extended stays in remote areas. So I would be relying on a DC-DC charger to keep the 36v battery up. If you are using a Minn Kota, they must be completely disconnected from the batteries while they are on charge, or you fry a board. Minn Kota emphasize this. So, if you intend to have the batteries charged on the fly, you would have to isolate/disconnect every single time before you start your motor.
    This is a copy and paste from a reply on THT. The yanks are obviously well ahead of us in this stuff, they took hold over there long before they did over here, particularly in the larger saltwater sizes.

    A couple of points from a MK authorized service tech. Hard wiring any of MK's trolling motors without a means to disconnect power is a no-no. If we see that in the field and you blow a control board, MK replaces it once and after that, if you dont correct it, it is on you. Leaving it connected even if you are not charging and the motor is off, you still have voltage going into the board, and if that is constant it will result in a premature board failure.

    Yes, there is a Gen 2 Ulterra. The Gen 1's had some issues, mainly with the trim housings seal design allowing water in, which would destroy the trim motor and lock up the entire unit. They redesigned the seal and top of the trim housing and it generally seemed to solve the issue. MK also has replaced Gen 1 trim units even if the TM is out of warranty (if you are the original owner). The other main issue I have seen is the worm gear tilt motor. The housing on this is cast aluminum and I saw a lot of them break where the base attaches to the frame via a SS pin. They have now redesigned the casting to beef it up and it has been a running change they made. Only other issues we typically see are sensor faults, which they redesigned one of the sensors, but most of this happens due to things sticking because of corrosion.

    My opinion is the Ulterra is good, and it has gotten much better with the design changes, but it is still just too complicated. There are 5 different electrical/mechanical systems on them-propulsion, steering, trim, tilt, and ipilot/gps. Any one of the 5 can cause it to stop working effectively and when it does, manually getting it up to get it home is difficult if you dont know the tricks to do it. Unless the auto deploy and trim functions are a necessity, the Terrova units have the same key features-ipilot, electric steering, spot lock, and are simpler and thus more reliable. Repairs on Ulterras vs Terrovas I would say are in the 4-1 range in how often they occur. Many Ulterra repairs are simple and only require cleaning/lubrication, or a reset procedure, but they are annoying for a customer especially if you dont have a quick release to remove the motor from the boat.
    The whole thread is here https://www.thehulltruth.com/boating...country-2.html They start talking about reliabilty issues around post #21. This has been raised many times on that forum. The boards are very voltage sensitive, Minn Kota warn about this on their website, even down to recommending against Lithium due to the slightly higher voltage they will deliver compared to a lead acid of the same rating.
    So beware of a DC-DC charger for them. Fine if you only go out for 2 days, you'll probably get almost two days out of good batteries, then charge them at home with it unplugged.

    There are Lithiums out there rated for start useage if you look around, most seem to be deep cycle. I'd have no qualms about using a deep cycle lead acid as emergency start--some people get their knickers in a knot about it, I've done it, it's fine. All you'll do is shorten it's life if used as a start battery on a regular basis, it won't blow up on you or anything like that. As for Litium in the same circumstances, I'd seek expert advice.

  4. #4

    Re: Best Setup to Charge Batteries on Board

    [QUOTE=ranmar850;1681099]Be careful if you want to charge on the fly with a 12-36v DC-Dc charger for a spotlocker. I've been looking into this for quite a while, and have decided it's just not worth the effort. My useage would include a lot of extended stays in remote areas. So I would be relying on a DC-DC charger to keep the 36v battery up. If you are using a Minn Kota, they must be completely disconnected from the batteries while they are on charge, or you fry a board. Minn Kota emphasize this. So, if you intend to have the batteries charged on the fly, you would have to isolate/disconnect every single time before you start your motor.
    This is a copy and paste from a reply on THT. The yanks are obviously well ahead of us in this stuff, they took hold over there long before they did over here, particularly in the larger saltwater sizes.



    I've currently got a sterling 12/36v dc dc on board charger, the output fuse is only 25a to the lithium 36v battery. The MK is then fused with a 70 amp circuit breaker from the lithium battery onto the MK. i'm no electrical engineer but from what i understand is implied is that the 25a current that feeds into the lithium battery is suggested to affect the circuit board of the MK unit which is fused at 70amps?

    Doesnt seem right to me....

  5. #5

    Re: Best Setup to Charge Batteries on Board

    Ranmar. The Yandina trollbridge is apparently built for just this application. When the 36v batteries are charging from the alternator it puts the 3x12v batteries back in series while the charging is going on. This means you canít run the TM and the outboard at the same time. Apparently though there is a manual over ride for this. But if you just want the TM lithiumís charged up while running between different locations then the Yandina Trollbridge does exactly this. There is a lithium and non-lithium version.
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  6. #6
    Ausfish Platinum Member
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    Mar 2015
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    Kalbarri, WA

    Re: Best Setup to Charge Batteries on Board

    [QUOTE=baitable;1681101]
    Quote Originally Posted by ranmar850 View Post
    Be careful if you want to charge on the fly with a 12-36v DC-Dc charger for a spotlocker. I've been looking into this for quite a while, and have decided it's just not worth the effort. My useage would include a lot of extended stays in remote areas. So I would be relying on a DC-DC charger to keep the 36v battery up. If you are using a Minn Kota, they must be completely disconnected from the batteries while they are on charge, or you fry a board. Minn Kota emphasize this. So, if you intend to have the batteries charged on the fly, you would have to isolate/disconnect every single time before you start your motor.
    This is a copy and paste from a reply on THT. The yanks are obviously well ahead of us in this stuff, they took hold over there long before they did over here, particularly in the larger saltwater sizes.



    I've currently got a sterling 12/36v dc dc on board charger, the output fuse is only 25a to the lithium 36v battery. The MK is then fused with a 70 amp circuit breaker from the lithium battery onto the MK. i'm no electrical engineer but from what i understand is implied is that the 25a current that feeds into the lithium battery is suggested to affect the circuit board of the MK unit which is fused at 70amps?

    Doesnt seem right to me....
    The issue is with over-voltage, not overcurrent. These things seem to be ridiculously sensitive to even 10% over normal supply voltage.

  7. #7
    Ausfish Platinum Member
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    Mar 2015
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    Kalbarri, WA

    Re: Best Setup to Charge Batteries on Board

    Quote Originally Posted by Lovey80 View Post
    Ranmar. The Yandina trollbridge is apparently built for just this application. When the 36v batteries are charging from the alternator it puts the 3x12v batteries back in series while the charging is going on. This means you canít run the TM and the outboard at the same time. Apparently though there is a manual over ride for this. But if you just want the TM lithiumís charged up while running between different locations then the Yandina Trollbridge does exactly this. There is a lithium and non-lithium version.
    This is also the subject of some debate. They are quite aware of the Trollbridge, gets used, too many problems still crop up unfortunately. It really seems that the only way to safely charge them is to do it from 240v, either as single 12v or a 36v charger, with the Minn Kota completely disconnected. Just remember that DC-DC chargers, so popular these days, come with a caveat. You don't create energy out of thin air--if you want to step up from 12v to 36v , you are putting a big load on your alternator. They are quite inefficient, even 12v to 12v is really loading them up. Gods knows how much a 12v-36v draws.

  8. #8

    Re: Best Setup to Charge Batteries on Board

    Iím interested to look at what options there are from twin engines to make the most benefit from both alternators.
    Democracy: Simply a system that allows the 51% to steal from the other 49%.

  9. #9
    Ausfish Addict disorderly's Avatar
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    Re: Best Setup to Charge Batteries on Board

    [QUOTE=baitable;1681101]
    Quote Originally Posted by ranmar850 View Post
    Be careful if you want to charge on the fly with a 12-36v DC-Dc charger for a spotlocker. I've been looking into this for quite a while, and have decided it's just not worth the effort. My useage would include a lot of extended stays in remote areas. So I would be relying on a DC-DC charger to keep the 36v battery up. If you are using a Minn Kota, they must be completely disconnected from the batteries while they are on charge, or you fry a board. Minn Kota emphasize this. So, if you intend to have the batteries charged on the fly, you would have to isolate/disconnect every single time before you start your motor.
    This is a copy and paste from a reply on THT. The yanks are obviously well ahead of us in this stuff, they took hold over there long before they did over here, particularly in the larger saltwater sizes.



    I've currently got a sterling 12/36v dc dc on board charger, the output fuse is only 25a to the lithium 36v battery. The MK is then fused with a 70 amp circuit breaker from the lithium battery onto the MK. i'm no electrical engineer but from what i understand is implied is that the 25a current that feeds into the lithium battery is suggested to affect the circuit board of the MK unit which is fused at 70amps?

    Doesnt seem right to me....
    Is that 25 amps the total amperage available for charging..?

    If so wouldnt that means 25 divided by 3 which basically means you are putting 8 amps per hour of outboard use back into the 36v bank..

    If that were the case why even bother...thats an insignificant amount...

    Why not just build your 36v bank with a larger battery bank to begin with and avoid the cost and hassle of alternator charging and charge at home...?

    Originally looked at a combination of solar, trollbridge and a dc to dc charger.....I have had my 100 ah 36v lithium ion system for 15 months now and been on plenty of 2-3 day trips and the most I have used is 52ah ah in a trip ..

    I do however drop anchor at night and also if gets much above 12-15 knots for any length of time..

    In hindsight I'm glad I didnt pursue onboard charging.

  10. #10

    Re: Best Setup to Charge Batteries on Board

    [QUOTE=disorderly;1681167][QUOTE=baitable;1681101]

    Is that 25 amps the total amperage available for charging..?

    If so wouldnt that means 25 divided by 3 which basically means you are putting 8 amps per hour of outboard use back into the 36v bank..


    I run a single 36V lithium invicta battery. I guess i have the 25 amps going into the single battery. Twin motors wont help, as you will be limited by the amperage of what the sterling (or whatever chosen 12:36 charger) of the 12:36v charger can output. I think the sterling can imput up to 25 amps max. running a 100 ah battery thats 4 hours to fully charge running at full charge. The charger cant run at 25 amps all the time- i suspect it drops down to maybe 10A. The only reason why i went the ability to charge the 36v on water is for our 2-3rd day on the water. Dont forget everyone has different boat sizes (mine is a brick in the wind) and fishing schedule duration. I dont think many on this forum will be pushing having spotlock in a boat exceeding 7m. horses for courses.....

    At the end of the day the ability to have on water charging has only cost me 3 kgs in extra weight and about 400 bucks plus cabling for the 12/36 charger. MK 112lb 36v 87 inch shaft is about 24 kgs, 36v battery is about 25kgs...

  11. #11

    Re: Best Setup to Charge Batteries on Board

    [QUOTE=ranmar850;1681142]
    Quote Originally Posted by baitable View Post

    The issue is with over-voltage, not overcurrent. These things seem to be ridiculously sensitive to even 10% over normal supply voltage.

    If the issue is over voltage there are simple fixes... I thought the issue on THT was about ripple current not ripple voltage. Also QMEQ has made a public statement that BLA the suppliers of MK are accepting the use of LIfepo4 batteries now for running the MK motors. I think the biggest issue was that motors were imploding due to prolonged running at WOT. The thread was chatting about the circuit boards frying due to the MK unit not be isolated whilst charge was applied to the 36V battery- 2 different issues.

  12. #12
    Ausfish Addict disorderly's Avatar
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    Re: Best Setup to Charge Batteries on Board

    Quote Originally Posted by baitable View Post


    I run a single 36V lithium invicta battery. I guess i have the 25 amps going into the single battery.
    Remember 36v is 3 lots of 12v batteries so that figure is reduced about 3 fold...

    So I think that you will always be charging at a maximum of 10 amps or less..

    For me that was just too insignificant to bother with...

  13. #13

    Re: Best Setup to Charge Batteries on Board

    Quote Originally Posted by disorderly View Post
    Remember 36v is 3 lots of 12v batteries so that figure is reduced about 3 fold...

    So I think that you will always be charging at a maximum of 10 amps or less..

    For me that was just too insignificant to bother with...

    not if that extra 10% you can pump back into the battery gets you an extra 20 mins on red emperor rounds!!!!

  14. #14

    Re: Best Setup to Charge Batteries on Board

    Sounds all too confusing to me but I was wondering whether there was something similar to a VSR that you could run between the Lithium batteries and the MK i.e. it switches the MK off when it senses charging current to the batteries, and once the alternator is switched off then re-establishes power to the MK or will there still be a bit of a spike when that occurs. Maybe I'm oversimplifying it as electrikery is not my forte, I've decide to go with the simple charge at home policy myself once I get my LiFePO4.


    I wonder what the OP did as it has been some time since his enquiry was posted.

  15. #15
    Ausfish Addict disorderly's Avatar
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    Re: Best Setup to Charge Batteries on Board

    Quote Originally Posted by baitable View Post
    not if that extra 10% you can pump back into the battery gets you an extra 20 mins on red emperor rounds!!!!
    Well in that case its definitely worth it then...

    What size is your boat and which Red grounds are you fishing..?..?

    Quote Originally Posted by Dignity View Post
    I've decide to go with the simple charge at home policy myself once I get my LiFePO4.

    Yes Sam, if you can get away with it then its certainly easier and less complicated...

    I already have too many gadgets and gizmo's..

    I dont need more wiring and connections to stuff up...

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