charging issues

ws9876 · January 2010

I have a Suresine 300 watt...using small 12v battery right now. Backup system only. I have a Shumacher cheapo car battery charger to top it off.
1- can I put the charger terminals on the battery with the inverter leads on there too??? or do I have to take off the cables to the inverter..?? dont really see why I would have to but want to be sure....

2-I dont have the Suresine grounded at the moment. later. but I did ground the separate outlets that I have wired to it. But when I checked the outlets with the tester ,it showed an open ground. I thought the outlet ground would have made that right...???no..??

By the way..Crown battery is not very good about having distibutors near by..
they dont have many near Montana and dont return emails either.
Who can ship me some 225 ah crowns deep cycles to Montana..??
but I would rather have sealed but wont pay those stupid prices...
we dont believe for a second that it costs that much more to make them..

I wanted to mention ,I do happen to have one of those big red Blue Sea DC
switches,round, that has the 1,2,1+2 and off. I never used it for anything.
should I stick that in the loop and just shut off the juice to the inverter when I am using the car charger..???
do you break the pos wire on those switches(1 only) or does the neg have to
go thru the common lug also...??

icarus · January 2010

Re: charging issues

Question # 1 Yes, you can have the charger and the inverter wired and on at the smae time.

Question # 2 How are the outlets grounded? By rights, the outlets should only ground at on point, at the fuse box/breaker box to building ground. So pleas describe how you have the inverter/outlets wired.

Finally, if you are concerned about good battery health/value of batteries, I suggest that you use the car charger for the car, and get a good 4 stage charger. It is the only way you are going to be able to keep the batteries in top condition. A car charger won't adjust the voltage/current relationship as the batteries near full charge or when they float charge, and they don't change the charging parameters for differing battery temperatures.

Use the switch as you wish, but make sure you fuse/breaker the wire from the battery to the inverter. Remember, a 300 watt load on the inverter =~ 2.5 amps @120 vac, but on 12 volts it would be ~25 amps.

Tony

ws9876 · January 2010

Re: charging issues

whats a good small 4 stage charger cheap...???online....
figured out the switch..

the outlets are wired independant of house system but I tied the ground wire into the house system by jumping the ground wire to one of the house outlets.
better than nothing eh????
I will drive another rod next spring when I have an impact driver and use that
as a ground system for the solar system.
I am fused 100 amp dc

BB. · January 2010

Re: charging issues

You probably don't need a second ground rod and it could be a bad idea in some cases...

If you need to ground your DC system... Just run "ONE" DC ground wire to the common ground rod tie point. What you don't want is to get the AC ground system and DC ground system mixed up (connected in more than one point). For example, a DC grounded radio is accidentally tied to the green earth wire instead of the negative battery connection. That would cause DC current to flow through the AC ground/neutral connections. Not a good thing.

If you have two ground rods and get a voltage between them--it can cause your pipes and rebar in your foundation to fail from electrolysis if there is a DC voltage gradient between the two ground rods (not likely--but certainly possible).

-Bill

ws9876 · January 2010

Re: charging issues

If I could I would run a fat (Morningstar recommends) ground DC wire to my house mains. Maybe I will pony up for the wire and do that..sound ok???
but the outlet(romex) connection on the Suresine does not have a ground pin.
Its only 2 wire. Stupid and poor choice by Morningstar.
Right now the ONLY ground wire is a jumper 12awg from 1 inverter outlet to a close outlet
of the house system. This is ok for now right..?????
If I put in a fat DC ground I will ground the outlet to that fat wire also and disconnect from any other grounds....... is this ok??

dwh · January 2010

Re: charging issues

ws9876 wrote: »

whats a good small 4 stage charger cheap...???online....
figured out the switch..

If you are using the inverter at the same time that you are charging, then you might be better off running a 2-stage charger. 2-stage is the default for Iota chargers (without the IQ Module), and the Samlex have a DIP switch to set them to 2-stage if you are running a load while charging (they call it "UPS Mode").

icarus · January 2010

Re: charging issues

I believe you are wrong about the sure sine and it's grounding. If you read the instructions on the Suresine300 it clearly states that the way to ground the inverter is to choose either 120 vac conductor and ground it, and IT becomes the neutral/ground. I bought this inverter specifically because you could bond the neutral to to ground un-like many small inverters.

So you can wire your receptics with 2 wire with ground, carry the bare back to the inverter and bond it to the white or better yet, use a sub panel, land the ground on the grounding bus bar, and carry it through to the building ground. That way, the recepts are earth ground.

http://www.scribd.com/doc/21008682/MorningStar-SureSine-300-Inverter-Installation-Operation-Manual

There are better links out there to pdfs that you can print, this was just the first one I came to.

PS Iota or Xantrex TC series charger, but you won't find them "cheap"! Why cheap out when the batteries are the expensive part of the system?

T
Tony

ws9876 · January 2010

Re: charging issues

i'm not an EE but I dont see why people call neutral anything but the white wire on Romex. Its not ground.. it sounds like you say bring the bare back to the inverter and join it to the white wire. If that was the case why wouldnt I just join the bare
and the white together ...
I'll put a buss bar on the plywood and connect both DC and ac grounds to the mains with a 8 awg wire...ok???

BB. · January 2010

Re: charging issues

The "Neutral" in North American 120/240 VAC split phase wiring is the ground center-tap of the pole transformer.

The neutral and the green/bare ground wire are pretty much the same thing in someways (i.e., they are both at zero volts to earth ground).

However, in the wiring scheme of things, they are very different. The green wire is never to carry current except in the case of a failure. The AC white wires should always be mated with their "hot counter part" so they don't carry too much return current (i.,e., the A phase + neutral + B phase will ensure that the neutral will never carry excessive current and since A+B are 180 degrees out of phase, if there is equal current flow through the A+B, the neutral carries no current. If miss-wired, such as A+neutral+A, it would return 2x the rated current through the neutral wire).

In general, the White+Ground connection will be made in the AC mains box, not in the trailer. If you switch over to Inverter power, you could simply let the AC hot/neutral connections float, or tie the "neutral" to frame ground of the RV. Of course, you would need a plug/switch to lift the Neutral ground when on shore power. You don't want the White+Neutral bonding in both the RV and the Shore Power Breaker Box--that would cause current to flow in the Green Wire ground of the shore power connector.

I have found a few appliances that won't work if the neutral is not grounded... In the one case I remember, it was our natural gas stove with spark ignition for the burners (if no flame detected, sparks until re-lite). When the Hot/Neutral where flipped (contractor error), the sparking function became very erratic in operation.

-Bill

icarus · January 2010

Re: charging issues

Green can also be bare copper, just to be clear.

Tony

ws9876 · January 2010

Re: charging issues

I appreciate the replies..however it is still unclear. I am going to leave the outlets untied to ground of the house AC system. 300 watts is not a big deal.
If I can afford a 6 awg wire 30 ft long...would you tie that from the inverter ground lug ,DC, to the mains house ground..?? yes or no..??

BB. · January 2010

Re: charging issues

I have never seen or taken apart a MorningStar inverter--so I am just guessing here.

But, I see no reason that I would run a 30' 4 awg wire from the inverter to earth ground unless you were trying to protect against lightning strikes.

In general, the earth ground should be connected to the metal chassis of the inverter (internally by the manufacturer) and should go back to the common ground point (where battery "-" and vehicle frame ground and the one ground lead to the earth ground rod all connect). The common ground point can then be wired to a ground rod--if needed (fixed installation in cabin for example). For a mobile/portable setup--nobody ever drives a ground rod next to the battery+inverter setup (camping, portable power, etc.).

The inverter's earth ground is there to ground the metal box of the inverter. If there was an internal short from battery "+" to the chassis of the inverter, the excess current would flow back to the common ground and back to the "-" terminal of the battery -- and create a current surge that would blow the breaker/fuses in the positive lead (either the 100 amp protective device at the battery positive terminal or the 3x 40 amp fuses inside the inverter itself).

If the inverter where directly connected to an earth ground and nothing else--then the short would cause almost no current flow, the chassis would become energized and a hazard to somebody if they touched the inverter box with grounded metal. If the battery where connected to the earth ground rod too (drawing shows the battery floating) then there would be a complete heavy gauge wiring path back to the negative battery terminal and the short would blow the fuse/breaker.

If this is in a metal building/vehicle/RV, the AC outlet Neutral and Ground Connection can be tied back to the common frame ground of the vehicle (or other metal point on the frame/chassis if easier to connect too). The AC output is only ~3-6 amp maximum--you don't need the 4 awg as the AC safety ground. In any case, since the AC output if the inverter is isolated (floating), you really do not need to earth the neutral/white wire unless you are trying to copy North American Building Code or you have a piece of gear that needs the Neutral to be Earth Grounded (very rare).

In normal operation, floating AC will work fine (neutral not bonded). The ground connection of an AC socket can be tied to the battery/building/chassis ground if you want (basically, you want the AC ground to be the same potential as the rest of the metal/plumbing in the area so that nobody is shocked if the AC ground and the plumbing/metal ground is touched at the same time by a person.

-Bill

ws9876 · January 2010

Re: charging issues

good enough
its going ungrounded per se
the fuses are good enough for any danger stuff
yee haw

BB. · January 2010

Re: charging issues

I should add--one of the more common devices that may like a chassis referenced neutral are florescent tube fixtures. The AC White/Neutral lead and Fixture Metal safety ground (usually the metal reflector behind the tubes) are tied together to help the lamp strike the arc (starting).

If the neutral and fixture "grounds" are not tied together (at some point), the lamps may not reliably start (particularly in cold weather).

The fixture does not "care" if there is a connection to ground rod / earth or not for starting.

-Bill

icarus · January 2010

Re: charging issues

I have the white side of my Suresine output, jumpered to the grounded side of the battery connection, which in turn is grounded to the building ground, as well as the neutral buss bar in the 12 vdc and 120vac panels.

charging issues

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