What Keith said, more or less...you can reduce them all to the same as you put on the + wire from battery to meter, if you start with 15A there; or drop some or all down to 10A. If you're not going to draw more than 10A on any given circuit there's no problem doing that. If you goof and do draw more than 10A you've only blown a fuse, nothing more expensive. Doesn't sound like you will, except for a small inverter...and as Keith pointed out, it will need to be a *small* inverter. One providing 200W AC (at ~1.6A max) will draw about 15-16A DC if it's actually powering a 200W-using gadget. AND most such inverters will handle a brief surge to 1.5-2x their continuous rated watts. So if you plug in something with a significant startup surge (AC motors being a primary example), but your DC circuit fuse is matched to the continuous max power of the inverter, it might draw enough, briefly, to blow your fuse. The basic math is watts = volts x amps. Your "twelve volt" battery if fully charged is actually 12.6. But a load pulls the voltage down - heavier load => lower voltage. So if you do your math based on 12V even, you have a margin of safety for when your load is heavy and/or your battery is run down. 12V DC vs. 120V AC is easy to ballpark because it's basically a factor of 10 - 10 times the V => 1/10 the A, and vice versa. Way too much information... :-) cheers, John S. On 02/20/2016 02:39 PM, Jazzy wrote:
Yes but the fuses all vary...should I put 10s on them all? On Feb 20, 2016 2:33 PM, "John Schinnerer" <john@eco-living.net> wrote:
Isn't your power panel one with breakers or fuses already included for each circuit? In that case each circuit is covered, for wire safety anyhow.
cheers, John S.
On 02/20/2016 01:56 PM, Jazzy 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 >>> >>> >>> >> >
-- 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
-- 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