Battery Cabling Question

[Tom in NH]

I am upgrading to a larger inverter. The larger current capacity means that I will have to use 4/0 cable between the battery and the inverter. My old system used 1/0 cable to connect the inverter to four batteries in parallel.

I'm wondering, do I have to go to 4/0 cable to connect the batteries in parallel, or could I keep the 1/0 cable in place and just use 4/0 to go to the new inverter?

--Tom

[RedLance]

Is the maximum amp draw of the new inverter enough to overload the 1/0 cable?  If it is, you'll need the 4/0 all the way to the last battery.  If you use the 1/0 cable between batteries, and 4/0 to the inverter, you are pulling all the amperage from the first 3 batteries through that last bit of 1/0 cable to the 4th battery.

I'd use the 4/0 all the way, assuming the inverter really draws that much current.

RedLance

[Tom in NH]

Yeah, you're probably right. That's the way I'll do it. 4/0 all the way. I was thinking maybe I could save a little expense and aggravation of making cables, but that is probably penny wise and pound foolish. Thanks.

[zmoz]

How big of an inverter is this?! And how many volts input? Even 1/0 cable will handle ALOT of amps. Since I have no idea how big your inverter is I can't say for sure, but I would think 1/0 between the batteries should be fine. Remember that a short peice of 1/0 can handle more amps than a long peice of 4/0. I'm just guessing that the wiring between your batteries is pretty short.

[Tom in NH]

It's the Xantrex 3000 PLUS. 2500 watt continuous, 5000 watt surge. I'm guessing the 12v max. surge current would be about 600 amps. The owners manual calls for 4/0 from battery to inverter, but it didn't say anything about the connections between batteries. That's what started me thinking...  Dangerous thing!

[zmoz]

2500 watts is only 208 amps at 12v. If the cable between the batteries is under a few feet, 1/0 is MORE than sufficient. I don't know how long the cable is between the batteries and the inverter, but 2/0 would probably be plenty for that too.

[Jerry]

Is it posable to use copper buss bar on your batteries? JK TAS Jerry

[Ungrounded Lightning Rod]

Yes you do want your jumpers to be as thick as the feeds to the inverter.  If nothing else, the last one before the battery with the feed will be pulling 3/4 the current of the feed itself.

For balancing your batteries REGARDLESS of the relative sizes of the jumpers, hook the + feed to the battery at ONE end of the string of jumpers and the - feed to the battery at the OTHER end.  If the + and - jumpers between each pair of batteries are of equal length this makes the total voltage drop in the + and - jumpers, as seen by each battery, be the same.  Your batteries are floating at slightly different voltages above ground but the voltage between the poles is the same for each.

[nothing to lose]

I like that setup in the pic, but isn't that a bit hard to check the water level?

I was thinking of something almost the same, one long piece of wire, remove the insulation at each battery bolt and use a washer above and below the wire to clamp it down with the wig nut. Maybe make a nice copper washer by drilling a hole through a penny? Well that's my 2 cents anyway.

 2 cents per connection :-)

Would make cable changes easy and cheap too, just remove wire and replace with new wire no worries about the size of connecters and wires matching or crimping etc.. when changing sizes in the future. That's if I went wired in a row like that.

 I figure the penny washer would secure the wire well and also act to spread the currant through out the wire. Plenty solid enough to take more force than would be applied by the wing bolts also.

My other thought is wire all the Pos terminals to one bolt and the inverter feed, then wire all the Negs to a bolt and the inverter feed. Each battery  is seperatly conneted to the feed making it easy to remove any one battery anytime.

I'm not that up on the amps for various wire gauges, but Watts divided by volts=amps.

Or Amps times volts= watts. SO....

600. amps X 12 Volts would be 7200 watts, abit more than you need for a 2500/5000 watt inverter.
     
5000. watts / 12v = 416.6 amps, but that's max load on your inverter for a very short time, not constant. Like a surge starting a motor.
      
2500. watts /12v= 208.33 amps if running max power load constantly.
      

[Victor]

Good luck finding copper pennies. Modern pennies are made of zinc and flash plaitted with copper. Heat one up with a torch to see it melt at a relatively low temp. The copper in a solid penny is worth more than a penny

[zmoz]

It's not that hard to find a copper penny...I just looked at the handfull of pennys beside my bed, about 20% of them are 1982 and older...

[Jerry]

Hi nothing to lose.

No problem with watter checking with these batteries. They don't have watter. They are gell cell type. Aviation batteries. They're 24 volt. wired  in siries for the 48 volt inverter they power.

There is 22 of them at 44 amp hrs each. This works out to be 484 amp. hrs at 48 volts.

Copper bars work good on flooded batteries setting side by side.   And yes take the positive and the neg. from oposite end of the bank. This keeps load sharing equal on all the batteries.

My oppinion off battery jumpers is also smaller gage is just fine. since the battries will be shoulder to shoulder the jumpers will be very short. Therefor will have very low resistance.

Look at a fuse. The size of metal in a fuse is very small compaired to ther power wire of the circut its in. However that small peice of metal in the fuse is very short compaired to the very large wire that feeds it. But yet it carries the same current. The same for wire end connectors. There is much less metal in the conector than there is in the wire.

                                 JK TAS Jerry

                               

[nothing to lose]

Yes I kinda figured those were some type of sealed battery, didn't know what type though off hand.

I have many many pennies that are old, and get more everyday in pocket change. Yes the copper in the penny probably is worth more than the penny itself. I know at one time years ago people were hording the pennies and taking them in for scrap or melting them down, I think 100 pennies had about $1.25 value as scrap copper.

 I don't know what happened to my nummbers in that post for watts, they did not show up right for me, 000.  instead of 5,000 ?? Hmm. don't know what happened there?

Well I am off to scronge for battereies and motors today, wish me luck

[Victor]

Your right Zmos, I was going to make a joke about how long the pennies were beside your bed, but I looked at a handfull of pennies and ~ 40% were copper.

 Just making the point that any penny may be a bad idea.

Victor

[zmoz]

Prices of copper have dropped since then...right now scrap copper is about $1.40/lb, and there's about 150 pennies in a pound. Maybe I should start hording pennies now in case the price goes back up. :-)

[nothing to lose]

Ya, might be a good idea if you wanted to hord pennies for future increase in copper value.

Even if it does not go up, as we drill holes in pennies to make washers there will become less and less real copper pennies available and the price for copper pennies will go up. Sort of like the old Wheat Cent pennies. Don't know what they go for now, but at one time they were at 2 cents a piece! $1 for a roll of 50 pennies! They may have gone either way by now, up or down?

I should look that stuff up for todays prices, I still have some REAL silver dollars, halfs, etc... too. I wonder which is worth more, face value, collector value, or scrap value for siver??