Typical value of individual circuit fuses that come by default in new Marine DC circuit panels when they are sold is often 15 or 20 Amps... I have seen much smaller values, ie 5-10 amp on boats like ours... In the end the reason I suggested a smaller value for the inline fuse for your power monitor is that given it's function and low cost it has the distinct possibility of having a practicable average power handling capacity which is well below the marketing "specification"..... The important thing is to fuse it... If it were me I would fuse it below it's maximum rating at least to start with, in this case perhaps 15 amps or so for the power monitor. If you do this you will then need something corresponding less for the "downstream" fuses so if you go with 15 in the inline power monitor fuse , you could drop 10 Amp fuses into the individual circuits.. The only circuit that gets close to that from you description is when you plan to use your inverter.. Practically speaking it's going to be hard to collect/generate more juice than that on our little boats unless you add an shore power input for use when docking..... Keith *Keith R. Martin, P.Eng.* *Burnaby, B.C. CanadaSerenity,** M17 Hull #353* On 20 February 2016 at 13:56, Jazzy <jazzydaze@gmail.com> wrote:
So, talk to me about fuses on the switches versus the one on the positive wire...
Jazz On Feb 20, 2016 1:54 PM, "Keith R. Martin" <keith.richard.martin@gmail.com
wrote:
My experience with low cost power electronics is that the maximum marketing ratings rarely if ever hold up under sustained maximum loads, and when they fail they often don't do so in a safe manner hence my suggestion to fuse it at a level lower than the max rating.
If you think your going to use it to monitor loads drawn by an inverter it would be have to be one of the smaller ones... As an example 150Watt inverter delivering full load to the AC is going to draw on the order of about 14-16 Amps, which is close to the power monitor's max rating... That said if charging a typical laptop (70W) via the inverter would probably draw 6-7 Amps DC well within range, similarly an 12V air pumps I have seen are on the order of 4-7 amps, so both of those are within the range ...
All that said if it were me I would want some head room between the the fuse rating and the units max rating given it's cost base..
The great thing is your power monitor will tell you whats happening and frankly help you settle in on a fuse rating that works for you, a simple check would be to check how warm the power unit gets under a sustained load...
Messing with boats... Tons of fun...
*Keith R. Martin, P.Eng.*
*Burnaby, B.C. CanadaSerenity,** M17 Hull #353*
On 20 February 2016 at 12:36, Jazzy <jazzydaze@gmail.com> wrote:
I'm thinking the biggest things that may ever go in the lighter plug is a little inverter or a pump to blow up an inflatable. Maybe I should fuse that switch a little higher? On Feb 20, 2016 12:34 PM, "Keith R. Martin" < keith.richard.martin@gmail.com> wrote:
Yup sounds like you are okay depending on what you plug into the cigarette lighter plug...
I would be surprised if the gps plotter and a couple of usb devices combined exceeded 3-4 A, the lighter plug however is often used to power devices that draw a little more current, but 6-7 amps of a lighter plug is a pretty good load..
The good think is your meter will tell you..... The worst that can happen if it's properly fused is it blows with too large a load drawn from the lighter plug...
Keith
*Keith R. Martin, P.Eng.*
*Burnaby, B.C. CanadaSerenity,** M17 Hull #353*
On 20 February 2016 at 12:21, Jazzy <jazzydaze@gmail.com> wrote:
Hi all, Keith, never too late for a party! With led lighting and an older small grayscale gps/plotter, 1 cigarette lighter plug, one dual usb plug I'm thinking I can't really draw enough to cause an issue. Is this a correct assumption? I don't have official specs on what the items draw, just seems minimal to me even with everything on On Feb 20, 2016 12:16 PM, "Keith R. Martin" < keith.richard.martin@gmail.com> wrote:
Late to the party but I concur with Mitch and John's last post...
*1. Power supply (battery) to “+” and “-“. Disconnect the battery from everything else. 2. Connect “+ load” and “- load” where the battery used to connect.*
Attached I think is the picture John was talking about showing a practical wiring connection for the device in lab bench setting.
I would definitely put an inline fuse on this, and given the low cost of the device if it were me I would limit the fuse to 10A .. Given the low cost of the device, if you think you need more than 10A on the boat I would have a hard look at the device to make sure it could safely sustain the higher currents.
Keith
*Keith R. Martin, P.Eng.*
*Burnaby, B.C. CanadaSerenity,** M17 Hull #353*
On 20 February 2016 at 11:46, John Schinnerer < john@eco-living.net
wrote:
> Ditto that... > > Note that the diagram says "built in shunt" - this means that
the device
> itself contains a thingamajig doohickey (sorry for all the technical terms > :-) called a "shunt" that all DC power passes through on its way to the > loads (and is what enables the measurement of the current). > > So just connect as the pictures show, battery + and - to battery, and then > you need to substitute your panel + and busbar - for the + and
of
the
big > wire-wound resistor DC load shown in the pictures. > > Absolutely fuse it, between battery + and meter +. A regular ATO or Mini > auto fuse inline holder will do. As someone already said, fuses are to > prevent fires mainly, protect the wiring from getting hot and/or melting. > > Also, if you're in saltwater environment mostly, don't expect this cheap > of a meter to last long. > > cheers, > John S. > > On 02/20/2016 09:00 AM, David Rifkind wrote: > >> >> On Feb 20, 2016, at 9:24 AM, Mitch Carnes < mitch_carnes@sbcglobal.net
>>> wrote: >>> >>> + to positive side of battery, - to negative side of battery. This >>> will power unit AND monitor battery voltage.+load to positive side of >>> battery - load goes to positive side of device being powered. (AMP/Current >>> meters are typically wired "in line" or "in series" of device being >>> monitored) The negative, or - side of the device being monitored still goes >>> to the negative side of the battery. >>> >> >> I don’t think this is right. Look at the photos in the eBay listing and >> you can see they have hooked up: >> >> 1. Power supply (battery) to “+” and “-“. Disconnect the battery from >> everything else. >> 2. Connect “+ load” and “- load” where the battery used to connect. >> >> It might not hurt to put an inline 20A fuse in the + line between battery >> and meter. Just in case. >> >> > -- > John Schinnerer - M.A., Whole Systems Design > -------------------------------------------- > - Eco-Living - > Whole Systems Design Services > People - Place - Learning - Integration > john@eco-living.net - 510.982.1334 > http://eco-living.net > http://sociocracyconsulting.com > >