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Thread: Battery monitor

  1. #21
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    Default Re: Battery monitor

    Quote Originally Posted by VicS View Post
    The smartgauge monitor certainly has its merits but on the downside it does not measure current, as other battery monitors do.

    If a display of charge or discharge current is important then the Smartgauge is not the one
    Thats perfectly true but interfacing the Smartguage with their split charge relay system (SmartCharge I think its called) gives a degree of battery management I have not seen in other systems. Advantages are 1 No voltage drop over diodes 2. The ability to tandem both battery banks for emergency engine start 3. Totally automatic system splits batteries when they are up to charge and wont allow services to drain engine start battery. You don't need to do anything. On my boat I fitted a separate analogue ammeter shunt on the service side to monitor charge/discharge. With a total cost of around £250 its more expensive but a brilliant system.

  2. #22
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    Default Re: Battery monitor

    Quote Originally Posted by boatmike View Post
    Thats perfectly true but interfacing the Smartguage with their split charge relay system (SmartCharge I think its called) gives a degree of battery management I have not seen in other systems. Advantages are 1 No voltage drop over diodes 2. The ability to tandem both battery banks for emergency engine start 3. Totally automatic system splits batteries when they are up to charge and wont allow services to drain engine start battery. You don't need to do anything. On my boat I fitted a separate analogue ammeter shunt on the service side to monitor charge/discharge. With a total cost of around £250 its more expensive but a brilliant system.
    A decent VSR would do the same, eg the Victron Cyrix at about £45.

  3. #23
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    Default Re: Battery monitor

    slightly off topic but if you have a bow thruster with a fuse of 300amp. What battery monitor do you use? The Nasa ones BM2 needs all your lecky to flow through a 200 amp shunt.

  4. #24
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    Default Re: Battery monitor

    Quote Originally Posted by MAURICE View Post
    slightly off topic but if you have a bow thruster with a fuse of 300amp. What battery monitor do you use? The Nasa ones BM2 needs all your lecky to flow through a 200 amp shunt.
    Nasa shunts (indeed all shunts) will withstand excess current for short periods. Anyway, most people would have a dedicated battery for a bow thruster, so the shunt wouldn't monitor it.

  5. #25
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    Default Re: Battery monitor

    Quote Originally Posted by MAURICE View Post
    slightly off topic but if you have a bow thruster with a fuse of 300amp. What battery monitor do you use? The Nasa ones BM2 needs all your lecky to flow through a 200 amp shunt.
    Assuming the bow thruster is operated from the house bank rather than a dedicated battery the shunt size needs to be considered carefully. The 200A shunt rating will be for continuous operation and the bow thruster will not operate continuously so it may still be OK. You need dive into the specifications looking at intermediate ratings. The durations etc.

    However, often the specifications are for best case conditions, adequate cooling, large gauge wires (these help dissipate heat from the shunt) etc etc. Even if the shunt is just OK it will be very marginal so personally I would forget the calculations and purchase a battery monitor with a 500A shunt. There several battery monitors that can be fitted with 500A (or larger) shunts.

  6. #26
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    Default Re: Battery monitor

    Quote Originally Posted by noelex View Post
    Assuming the bow thruster is operated from the house bank rather than a dedicated battery the shunt size needs to be considered carefully.
    It's rather unusual to try to run a thruster from the domestic bank - cable sizes are massive.

  7. #27
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    Default Re: Battery monitor

    Quote Originally Posted by pvb View Post
    It's rather unusual to try to run a thruster from the domestic bank - cable sizes are massive.
    It depends on the configuration of the boat. The installation position of the domestic bank is the most critical factor.

    It is usually cheaper to install a bow thruster battery so this method is increasingy used, but I would not agree that it is “unusual” to power a bow thruster from the domestic battery. Powering the bow thruster from the domestic bank is preferable if it is practical.

    Anyway, Maurice will know if he has a bow thruster battery or not so can decide if the domestic batteryy shunt needs to be rated for this load.
    Last edited by noelex; 22-08-19 at 19:00.

  8. #28
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    Default Re: Battery monitor

    The VSR you mention would certainly have many of the functions of the Smartcharge but interfaced with the Smartguage I think you would find that functions are available that cant be achieved with a VCR alone. The Smartguage puts information on the display that tells you exactly how and when the relay is operating and has an inbuilt learning program that recognises the capacity and condition of each battery bank. As I said however, it is expensive and if you are happy to pay £45 for a Victron plus another £100 or so for a cheap battery monitor I would not argue. My own opinion however having had one is that the extra functions of the system are worth having. Its entirely a matter of preference however and I would not argue that standard VCR systems are no good. They are infinitely better than diode bridges or manual switching.

  9. #29
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    Default Re: Battery monitor

    Quote Originally Posted by noelex View Post
    Assuming the bow thruster is operated from the house bank rather than a dedicated battery the shunt size needs to be considered carefully. The 200A shunt rating will be for continuous operation and the bow thruster will not operate continuously so it may still be OK. You need dive into the specifications looking at intermediate ratings. The durations etc.

    However, often the specifications are for best case conditions, adequate cooling, large gauge wires (these help dissipate heat from the shunt) etc etc. Even if the shunt is just OK it will be very marginal so personally I would forget the calculations and purchase a battery monitor with a 500A shunt. There several battery monitors that can be fitted with 500A (or larger) shunts.
    While I think 500A might be OTT I would certainly not fit one with a 100A capacity. Many vessels have inverters fitted these days and if the service batteries are ever switched in for engine start that current also runs through the shunt. 200A should generally be OK but 100A in my view is risky unless your system is very basic.

  10. #30
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    Default Re: Battery monitor

    Quote Originally Posted by boatmike View Post
    While I think 500A might be OTT I would certainly not fit one with a 100A capacity. Many vessels have inverters fitted these days and if the service batteries are ever switched in for engine start that current also runs through the shunt. 200A should generally be OK but 100A in my view is risky unless your system is very basic.
    I think it is a little dangerous to generalise. Electrical systems have grown more sophisticated. Inverters, anchor windlasses, bow thrusters can all draw more than 200A in some installations. Of course on some occasions these items will be used together with other high draw appliances, so I think it is important to check rather than assume. 200A is not a large shunt these days.

    Certainly for our boat, a 500A shunt is needed despite running on 24v, which halves the current needed.

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