Suggestions 12V Inverter Overload Protection?

[KenO]

Am planning a wildlife photo shoot where an automotive 12V battery will be the primary charging device for camera Li batteries. The camera Li chargers have Input: 100-240V 50-60Hz (18-24 VA) Output: 8.4V 0.9A

To minimize charging hardware we want to use a 12V Inverter.

Am guessing that someone may unintentionally overload the Inverter so would like to make sure only the protection system is activated without damage to other components.

Appreciate suggestions how to make sure the Inverter purchased is fully protected from overload.

I am thinking that probably the most important thing is researching the 12V Inverter design.

Have searched for 12V Inverter Reviews but to date have only found a few customer ones that were not that technical.

Hope some others have researched this and would offer suggestions.

Thanks

Ken

 

KenO <kenitholson@yahoo.com> wrote:
> Am planning a wildlife photo shoot

Am writing telegraph style. Don't know why.

where an automotive 12V battery will be the primary charging device
for camera Li batteries.

Are you using the battery that's already installed in the car, or just a
loose battery by itself?

If you're using a loose battery, and you plan on recharging the camera
batteries multiple times (like, you'll be there for many hours), and
maybe if you plan to do this again in the future, you might be better
served by a "deep cycle" RV or trolling motor battery, as opposed to a
starting battery.

If you're using a loose battery, and you're going to do this once for an
hour or two, a $20 starting battery (or two!) from the junkyard is fine.
When you're done, you can get $1 or $2 back by taking the battery to a
scrap dealer.

If you need more than 100 W or so of output power - if you're going to
be running more than four or five of your chargers at once - it's
probably worth it to connect the inverter, through a fuse, directly to
the battery terminals, instead of trying to use a cigarette lighter
plug. For up to 30 A on the DC side, you can use one of the flat 1"
wide automotive fuses in a holder - every car parts store has these.
For more than 30 A, use one of the larger automotive fuses - there are
several kinds with holders to match. Car parts stores have the big
fuses but maybe not the big holders; look with the car stereo stuff, or
check a car stereo shop.

If you wire the inverter directly to the battery, make sure there is
some way to relatively easily disconnect the inverter - you may have to
do this to reset the overload protection on the inverter. It's hard to
buy a switch that doesn't suck at this power level, so something like
pulling the fuse, or a ring terminal on a stud secured by a wing nut, or
a bolted terminal and you keep the wrench with the battery, is OK.

If you're going to do this a *lot*, get a plastic battery box from the
general store or a place that sells RV parts. You can maybe bolt the
inverter to the lid or the side and make a whole self-contained unit.

Am guessing that someone may unintentionally overload the Inverter so
would like to make sure only the protection system is activated
without damage to other components.

Most small (< 200 W) inverters I have used have had a couple of levels
of protection. They usually have an automotive-style fuse on the DC
input. They also usually have some kind of electronic overload
protection on the AC output. Usually a beeper goes off and/or a red LED
comes on, the AC output is either reduced or shut off completely, and
you have to remove and restore the DC power to restore the AC output.

Some larger inverters have a circuit breaker on the AC output. Really
big ones have one on the DC input.

Appreciate suggestions how to make sure the Inverter purchased is
fully protected from overload.

Don't buy a really cheap junk inverter, like from Harbor Freight Tools,
or a $5 "300 W" inverter on Amazon or Ebay.

If you're really worried about it, you could wire a fuse holder,
probably for a 3AG/AGC/1.25"x0.25" glass tube fuse, in series with the
AC output. These fuses are available in 1 A increments, and sometimes
finer than that.

You might be able to buy a power strip and replace its circuit breaker
(usually 15 A) with your fuse holder, and then decree that all camera
chargers get plugged into the power strip and not directly into the
inverter.

If you're going to be far away from the car battery, then this doesn't
help, but if you will be reasonably near, a suggestion: also plug in
a small lamp, like a 4 W night-light or a 7 W Yule lamp, into the
inverter output. Put this lamp somewhere you can easily see it from
a distance. This wastes a little power but lets you know at a glance
if the inverter has shut down for some reason.

I am thinking that probably the most important thing is researching
the 12V Inverter design.

You won't find anything about this for the cheap junk inverters. Better
ones will say that they have "overload protection" but the only way to
find out what that means is to buy one and try it. A brand name you
have heard of before is somewhat of a vote of confidence, but beware of
*old* brand names that are now applied to whatever is cheapest.

For a really nice inverter, go to an RV store. The ones built into RVs
have more features than you need, but the RV manufacturers are highly
interested in not having vehicles burn down, so their inverters tend to
be better.

Matt Roberds