Winter disconnect for batteries in series

Discussion in 'Electronics Q&A' started by sb in gp, Nov 28, 2022.

  1. sb in gp

    sb in gp Active Member

    857
    Oct 10, 2006
    Grosse Pointe, MI
    2016 Tiara 50 Coupe
    Volvo D11 IPS
    I have 4 engine batteries for 2 engines (see pic). They are in series providing 24V to my Volvo motors. When I had a 12V setup, I always disconnected the negatives.

    For winter storage this year (indoor heated) I completely removed the two middle cables (see red rectangle in pic). Is this good, or should I make sure all negatives are detached?

    Engine Battery disconnect.jpg
     
  2. km1125

    km1125 Well-Known Member

    411
    May 5, 2021
    470
    Cummins QSB6.7
    You're good with just removing those jumpers in the middle. It effectively breaks the circuit.
     
    sb in gp likes this.
  3. mschneider

    mschneider New Member

    3
    Apr 14, 2022
    2005 340 Sundancer
    8.1 Horizon w/v-drives
    I agree with km1125, disconnecting the jumpers should be fine.
     
    sb in gp likes this.
  4. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    Actually if you can, put a battery minder on them for the winter. If not possible then yes, disconnect the jumpers.
     
  5. Jus Cruisin

    Jus Cruisin Well-Known Member

    Oct 6, 2021
    Lake St Clair - MI (Belle Maer Harbor)
    2004 390 DA
    8.1's
    Yeah like @SKybolt said. Inside, you should have access to electrical outlets. That's what I'm doing. Just plug it in when I'm knocking around the boat. You just can't leave it plugged in unattended.
     
  6. sb in gp

    sb in gp Active Member

    857
    Oct 10, 2006
    Grosse Pointe, MI
    2016 Tiara 50 Coupe
    Volvo D11 IPS
    I typically do just put trickle chargers on the batteries and plug them in when I'm there. With 10 batteries in this boat it gets a bit more challenging.

    So for the house bank (6 x 12V) I connect built-in 12v charger to a temporary AC pigtail plug that I can plug into the wall to periodically top off the house batteries. In the spring, I'll remove the pigtail plug and reconnect the boat AC.
     
  7. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    6 House batteries!, all in paradelle? That's crazy, you should put in one 8D and be done. Will take up less space and last longer and provide more amperage for a longer period of time.
     
  8. sb in gp

    sb in gp Active Member

    857
    Oct 10, 2006
    Grosse Pointe, MI
    2016 Tiara 50 Coupe
    Volvo D11 IPS
    I was surprised at the number of house batteries too. This was the original Tiara design and all were replaced by PO with AGM last year. Replacing 6 with 1 8D is an interesting idea for when these near end of life.
     
  9. Wylie_Tunes

    Wylie_Tunes Well-Known Member

    943
    Oct 26, 2012
    Lake Wylie NC area
    N/A
    N/A
    Id leave each pair wired in series as thats the way they live and are used. All you need to do is make sure each bank is disconnected from any non-crucial laods. If each main B+ cable runs through a master battery switch, then off should accomplish this and no other action needed.
     
  10. sb in gp

    sb in gp Active Member

    857
    Oct 10, 2006
    Grosse Pointe, MI
    2016 Tiara 50 Coupe
    Volvo D11 IPS
    Yes, there is a main switch for each bank. So you're saying that I should not disconnect the cables? My understanding was there could still be some draw that bypasses the switch, like bilge pumps, but maybe that is just for the house bank.
     
  11. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    One 8D will supply close to 1400 amps and have a 430 min reserve. Your not going to get that from 6 group 31's (assuming they are 31 or 34, if 27 a whole lot less).

    With regard to your 24v engine banks. Disconnecting them is best, but since they are in series switching the battery switch off is also just as good. Bilge pumps are not going to be running while out of the water, at least in theory they aren't.
     
  12. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    Depending on your setup, things like the stereo and computers can often draw a tiny bit of power even with the battery switch off. Some auto-bilge pumps will check for water every so many minutes and turn on for a couple seconds as a "test". You'll probably be fine, though, by just turning the battery switch off... but you'll "definitely" be fine by removing the negative cables.

    (6) 27's (deep cycle) (or even 4) will definitely give a longer reserve time. I've never looked into the specs of (before now) an 8D size battery, but that's pretty impressive performance from a battery that weighs about the same as two regular deep cycles. Unless I looked at the specs wrong - I only looked very quickly.

    For example, I just looked at Dekas... a gGroup 27 has 175 minutes @ 25 amps. While a single 8D has 517 minutes!

    Certainly something to think about when the existing batteries are at the end of their life.
     
  13. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    Never meant to suggest that an 8D would equal six 27's. You would need two 8D's for that. But an 8D will out last single batteries when it comes to having to replace them.

    Six house batteries is crazy and in most cases not needed. One 8D would be more then enough for the average person. I use to have one for a house battery on my 340 and had converted everything to 12v and it lasted an easy three days, that included the refrigerator and an 12v Ice chest. Fans and three 12v tv's and video games (kids).

    As for removing the battery terminals, I would leave the negative and remove the positive side if your going to remove anything.
     
  14. sbw1

    sbw1 Well-Known Member

    Oct 10, 2006
    West Michigan
    This is listed in my signature
    This is listed in my signature
    I used to turn off all the battery switches as well as the DC and AC breakers. I believe that eliminates any small current drains. Put the boat in storage with fully charged batteries and never had any issues. Yours is a more complex setup, but turning every off including all the breakers should prevent issues.
     
  15. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    I agree - with a little thought and battery usage management, you can do quite a lot on batteries. This was a smaller boat with a smaller fridge and smaller kids (didn't need TV's or computer games), but I once went 3 days and nights on a single group 27DC - only ran the engine for about 45 minutes the entire time (to a lunch spot and back).

    "Generally", the rule of thumb is to always remove the negative first and put it back on last. That's more about safety when there's metal around (like a car engine bay). It's obviously less of an issue in this case. Truth is, you just need to interrupt the circuit - removing either + or - will do the job.
     
    SKybolt likes this.
  16. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    Usually when it comes to DC power related devices the ground is never removed first. With regard to boats, I always turn the battery switch off then remove the positive first. Should there be an issue in the circuit somewhere and any of the devices find a new path to ground, they could be damaged. Removing the positive first limits or removes that possibility.
     
  17. km1125

    km1125 Well-Known Member

    411
    May 5, 2021
    470
    Cummins QSB6.7
    He's talking specifically about the battery connections. It's always better -from a safety perspective- to remove the negative connection first, as any errant contact with the wrench and a nearby bracket or other grounded item would not be as "eventful" as one on the positive side of the battery.
     
  18. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    I understood what was being discussed, but disagree with this. An errant wrench has nothing to do with what I posted. That is a different safety issue and I don't see how disconnecting the ground effects that. So we'll have to agree to disagree. Not trying to be argumentative, just don't agree.

    From an electrical stand point my post makes sense.
     
  19. Lazy Daze

    Lazy Daze Well-Known Member TECHNICAL Contributor GOLD Sponsor

    Apr 21, 2009
    PA
    Various
    Various
    In this case, as I mentioned above, it's not nearly as much of a safety concern as it is in a car because, well, there isn't a whole lot of metal nearby like in a car engine bay :)

    The car's frame and, pretty much ALL, metal items on a car are grounded to the battery. If one would remove the positive first, there's a chance that the wrench, while still on the positive lug, can contact a piece of metal. This will create a HUGE spark and it WILL scare you... or at least it did me! I have a wrench or two laying around somewhere that still have the crater in them from this mistake. Yes, it will actually leave a crater in the wrench!!!

    If the ground lug is first removed and THEN a wrench bridges the positive lug to metal, nothing will happen.

    I'm wondering, though... are we disagreeing because I'm talking about the battery and you're talking about an actual device/accessory? Although, if I'm removing a starter (for example), the negative battery cable still comes off first to avoid that arcing possibility. It sounds like maybe you're referring more to electronic 12V items? In that case, I'd like to hear more about the reasoning behind what you said in post 16. For clarity, since we only have words here, that's not sarcasm - I really do want to hear more about it.
     
  20. SKybolt

    SKybolt Well-Known Member SILVER Sponsor

    Nov 11, 2014
    Kent Narrows, MD
    460 EC
    Detroit 6v92TA
    (Low profile's)
    Alison Gears
    Westerbeke
    12.5kw Genset
    I wasn't speaking from a car perspective, but agree with the car scenario. Boat's are a little different in that there is not to much to spark too and have a lot more custom wiring then your average car. If car's had battery switches this point would be moot and pulling the positive would make total sense.

    Once the positive DC is dead then there is no DC power, pulling the ground does not guarantee that. In most cases turning the battery switch off does the job. The only thing that should be on the battery side of the switch are bilge pumps.

    From an engineering standpoint and DC device(s), should anything still be powered some how, pulling the positive is the safest thing to do for an electronic device like a plotter or display etc. Meaning power switches never switch the ground off, they always switch the positive off. Disconnecting the ground first can cause electronics to sustain damage. In most cases boats have multiple ground points and in some cases can find the bonding system enough of a ground to allow dc devices to see low dc voltage. Didn't say in all cases, but in old boats that have had lot's hands in them, wiring is usually an issue.

    Turning the battery switch off, does and will prevent arching from changing out a starter. If it does not, that boat has bigger issues then just the starter. I have never removed a ground and only turned off the battery switch when changing a starter, and yes, I have changed many in my life. I also had a mobile marine service for years that turned into solely electronics based over time. So I am speaking form a professional stand point and not a boat owner's one.

    I get your point about pulling a cars positive, but we are talking boat's and the two have little in common.
     

Share This Page

Show Sidebar