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  1. #1

    running a battery charger off an inverter

    I have a 3 x 130aH deep cycle 32v system Minn Kota being charged by a ProSport 20 plus triple bank charger, which plugs into my AC when at home.
    While its a great system for day trips and most uses, for overnight or more I think I would need another option.
    Has anyone ever used an inverter (2000W pure sine) to supply 230V to the battery charger for the MK batteries?
    Is this possible to run off my 100aH house deep cycle, even with the motor running.
    My yamaha has a 35A alternator at full noise or 27A at 1000 rpm.

  2. #2
    Ausfish Gold Member
    Join Date
    Mar 2015
    Location
    Kalbarri, WA

    Re: running a battery charger off an inverter

    Inverter will draw approx 20 X DC current as the AC current required. How much is the AC draw on 240V?

  3. #3

    Re: running a battery charger off an inverter

    The trouble with charging leccy batteries when out on the water is that you need to run the outboard motor for a hell of a long time to put enough charge into the batteries - whether its a DC-DC / inverter / trollbridge etc - (we are talking several hours) The problem is exacerbated when you are talking 24 & 36 volt systems.

    I guess from my point of view - you are probably better off carrying a generator & running it to power your chargers .

    I haven't found the magic bullet but the best I came up with was to run LiFePO4 batteries (24 volt system) & each have their own onboard Victron 25amp charger . I'll carry a 2KVA Honda Generator & can pump in 75 amps in 3 hours - The additional benefit of the LiFePO4s is that you can discharge them further & pump in higher amps before the charger goes into Absorb mode at 95% .

    Yes sure running a gennie is a pain at the end of a day ( specially if you are planning to stay on the boat for the night) ….. but if you are going remote for several days what options are there ?

    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

  4. #4

    Re: running a battery charger off an inverter


  5. #5

    Re: running a battery charger off an inverter

    Quote Originally Posted by scottar View Post
    So how many amps will be put into the 3 batteries ?

    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: running a battery charger off an inverter

    Quote Originally Posted by NAGG View Post
    So how many amps will be put into the 3 batteries ?

    chris
    I was talking to a a guy who sell the Trollbridge in Victoria today.....they will put in as many amps as much as your alternator can put out...…...…..some of the dc-dc chargers only put out 20 amps or less..

    Maybe I'm a simple guy but with the simplicity and durability of the trollbridge I can t see why anyone would buy a sterling or similar with only a 2 year warranty...

    I was told its very simple to also just hook a solar system up to the start battery and it will fill the leccy batteries as well.....I was also told that if you don't have huge house battery requirements that one of the leccy bank batteries can be used for accessory requirements….thus saving a stand alone house battery.....

    So a bit over $200 for 24v or $315 for 36v.....,,,,can anybody confirm what I was told......it sounds to good to be true...….gunna keep the leccy batteries topped up with a combination of alternator and 600 watts of solar cranking along....no need for a generator you would think..

  7. #7

    Re: running a battery charger off an inverter

    Quote Originally Posted by NAGG View Post
    So how many amps will be put into the 3 batteries ?

    chris
    Ultimately determined by your charging system but it's rated at up to 100 amps - basic maths equals 33 amps each for a 36 volt system assuming you have 100 amps to spare. In reality though most boats wouldn't have anywhere near that available in surplus. Whether it is worth doing is going to be purely dependant on the individuals usage pattern. If you run to your spot, fish all day and then run home it's probably a waste of time. If you are running between spots regularly and want to maintain as much charge as is possible without the need for solar or a generator, it's a pretty simple system that will offer some benefit for a reasonably small outlay.

  8. #8

    Re: running a battery charger off an inverter

    Quote Originally Posted by disorderly View Post
    I was talking to a a guy who sell the Trollbridge in Victoria today.....they will put in as many amps as much as your alternator can put out...…...…..some of the dc-dc chargers only put out 20 amps or less..

    Maybe I'm a simple guy but with the simplicity and durability of the trollbridge I can t see why anyone would buy a sterling or similar with only a 2 year warranty...

    I was told its very simple to also just hook a solar system up to the start battery and it will fill the leccy batteries as well.....I was also told that if you don't have huge house battery requirements that one of the leccy bank batteries can be used for accessory requirements….thus saving a stand alone house battery.....

    So a bit over $200 for 24v or $315 for 36v.....,,,,can anybody confirm what I was told......it sounds to good to be true...….gunna keep the leccy batteries topped up with a combination of alternator and 600 watts of solar cranking along....no need for a generator you would think..
    Main issue is that it can't charge the batteries and run the electric at the same time so if you are on the electric during the day, your solar isn't doing anything apart from charging your start or 12v house system. If you go to a 12v in - 24/36 volt out type charger, the surplus from your solar can be going in while you are running the electric - up to the rating of the charger of course. The other option would be a solar system at the rated voltage of your electric but this wouldn't then be charging your house power - unless your house bank is part of your electric set up - not recommended in my book.

  9. #9

    Re: running a battery charger off an inverter

    From all I've heard, read and been told is that the FePo4 batteries do NOT like intermittent charging, that is charge for a short period, at different rates of charge e.g. idle vs running at 4200rpm. All suppliers of quality Lithium Iron Phosphate batteries say take them home and charge them properly. The consequences are very shortened life and considering their current cost, expensive. Also my understanding is that if you have 3 x 12V FePo4 batteries in series, they should all be purchased at the same time and when charged , in parallel at the same time. They do seem to have a few more issues with with voltage and current disparities. All slowly being resolved and by the time it is nicely resolved something new will be around the corner e.g. LTPS or even better.

  10. #10

    Re: running a battery charger off an inverter

    Quote Originally Posted by scottar View Post
    Main issue is that it can't charge the batteries and run the electric at the same time so if you are on the electric during the day, your solar isn't doing anything apart from charging your start or 12v house system. If you go to a 12v in - 24/36 volt out type charger, the surplus from your solar can be going in while you are running the electric - up to the rating of the charger of course. The other option would be a solar system at the rated voltage of your electric but this wouldn't then be charging your house power - unless your house bank is part of your electric set up - not recommended in my book.
    Oh bugga thought it sounded to easy...so basically while the battery bank is being used for a 36v application each battery cant also be separately charged at 12v...? can I just use a solar controller from 12 to 36v...?...and what are the pitfalls of using a trolling motor battery bank as house battery Scott...?

  11. #11

    Re: running a battery charger off an inverter

    Quote Originally Posted by scottar View Post
    Ultimately determined by your charging system but it's rated at up to 100 amps - basic maths equals 33 amps each for a 36 volt system assuming you have 100 amps to spare. In reality though most boats wouldn't have anywhere near that available in surplus. Whether it is worth doing is going to be purely dependant on the individuals usage pattern. If you run to your spot, fish all day and then run home it's probably a waste of time. If you are running between spots regularly and want to maintain as much charge as is possible without the need for solar or a generator, it's a pretty simple system that will offer some benefit for a reasonably small outlay.
    OK ….. that's the theoretical & depending on the size of your motor(s) your alternator could be only 40amps like my DF140

    Reality is another story - With the exception of LiFePO4 batteries …… shouldn't deep cycle batteries only be charged at around 10-15% of the batteries capacity ? …… so what damage would 33 amps do to a 100/120 amp AGM / GEL ? (If you could pump in that much)

    On the water - Realistically how far do people run between locations ? ……. most fishoes wouldn't move too far from their chosen destination - I certainly doubt that they would do too many 1 hour transits ( not for a trailer boat operator who will rely on an electric motor ) . Probably the exception would be boats fishing the big rivers in the NT .


    Where I'm coming from is that depending on conditions (wind / tide … both) - you could be drawing anywhere from 20-50amps / hour spot locking ….. though I guess you could leave the motor running while spot locking.

    The Trollbridge sounds wonderful but I'd like to see some realistic data on a trollbridge running off a 150hp outboard & maintaining the house battery & 2 x 100amp AGMs

    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

  12. #12

    Re: running a battery charger off an inverter

    Quote Originally Posted by Dignity View Post
    From all I've heard, read and been told is that the FePo4 batteries do NOT like intermittent charging, that is charge for a short period, at different rates of charge e.g. idle vs running at 4200rpm. All suppliers of quality Lithium Iron Phosphate batteries say take them home and charge them properly. The consequences are very shortened life and considering their current cost, expensive. Also my understanding is that if you have 3 x 12V FePo4 batteries in series, they should all be purchased at the same time and when charged , in parallel at the same time. They do seem to have a few more issues with with voltage and current disparities. All slowly being resolved and by the time it is nicely resolved something new will be around the corner e.g. LTPS or even better.
    That's pretty well what I was told - Use them & bring them up to at least Absorb (95%) …… To avoid those other issues I went with individual chargers for each battery . I just brake the 24 volt ( via an Anderson connector) & charge away putting in 25 amps .

    Originally - I tossed up with going the DC DC charger route & sticking with AGMs but when I looked at how my boat is used it just didn't cut it . I thought lighter with a greater DOD was the way to go


    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

  13. #13

    Re: running a battery charger off an inverter

    Quote Originally Posted by disorderly View Post
    Oh bugga thought it sounded to easy...so basically while the battery bank is being used for a 36v application each battery cant also be separately charged at 12v...? can I just use a solar controller from 12 to 36v...?...and what are the pitfalls of using a trolling motor battery bank as house battery Scott...?
    You would need a massive solar array to even put a dent in offsetting your electric motor usage …… unlike an fridge which might draw 5amps & then be able to get away with a 150W solar panel - your leccy even in good conditions might pull 10amps / hr .

    As for using your leccy batteries for house purposes ……. nah , better off leaving them isolated .

    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: running a battery charger off an inverter

    Quote Originally Posted by NAGG View Post
    You would need a massive solar array to even put a dent in offsetting your electric motor usage …… unlike an fridge which might draw 5amps & then be able to get away with a 150W solar panel - your leccy even in good conditions might pull 10amps / hr .

    As for using your leccy batteries for house purposes ……. nah , better off leaving them isolated .

    Chris
    As you mentioned before Chris...most of us, once we reach our starting destination, and begin fishing wont be travelling enough after that to add any significant charge via the alternator....
    If I put a couple of 300w panels on the roof (subject to available space),
    surely over the course of a day or 2 fishing that would add a useable amount of energy...it would also keep the batteries topped up while the boat is sitting around at home...

    Can someone better explain about the house battery thing though...I have been boating for over 40 years now and with my parents when I was a kid and then me as an adult.... We have never owned a boat with more than one battery ever before....

  15. #15

    Re: running a battery charger off an inverter

    Here the waters get really muddled. Size of boat, type of usage e.g. lots of accessories, distance travelled on water and whether offshore or inshore, type of battery used.
    There are only 3 types of battery basically.
    1 crank - high capacity load at short intervals with a lower level of DOD. Use for starter motor, anchor winch and trim tabs only generally.
    2 deep cycle - this includes your Lithium Iron Phosphate (benefits of higher DOD than lead acid or AGM and of course weight advantage) takes long slow loads, accepts higher DOD, doesn't like heavy start up loads and weighted than a crank battery (lithium Irons excepted). Use for lighting, GPS, sounder etc.
    3 hybrid crank deep cycle- usually have calcium in them and can be used as either but go below their DOD and you can virtually throw them out.
    As mentioned earlier depending on usage it is a matter of Safety, good house keeping especially with wiring looms etc.

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