Battery Upgrade

It is possible to have TOO MUCH battery capacity and exceed your ability to keep them charged.....or overload the charging equipment in the rig or the tow vehicle.

I think you need a somewhat sophisticated controller to handle 4 batteries but there are some "experts" on here who can be more specific.

delete

Yes you can do that all sorts of ways.

-If you run parallel links to join each "pair" you only need to ground one to the frame.

-You can have one side only do the inverter and give it its own solar set for recharging plus a portable charger when no solar. the other side can do the usual rig stuff, and have its own solar set and charger. Now you don't need the long parallel links

-You can put the inverter in the middle and have two wire sets for it.
Two wires from pos terminal and two from its neg terminal. One pos and one neg to each "pair". Now the inverter-battery wires are also the parallel links and they don't have to be so fat since each is carrying about half the amps.

-If you have a Trimetric with its shunt, it means if you split the bank you can only monitor the pair the shunt is on, but you don't really need a momnitor anyway :)

I have played with these set-ups a different times and they all work.

You need to recharge those T-1275s seriously to 14.8v temp adjusted or they won't last, so don't expect to keep them going with a 14.4 volt converter. A solar controller with adjustable voltage will help with that, plus an adjustable voltage charger for when not using solar. This type would be a good choice for that--he can do one up as a 100 amper for you.

http://www.bestconverter.com/Boondocker-BPCM-75-75-Amp-Adjustable-Power-ConverterCharger_p_587.html#.VkJ-FHmFNjo

Here is one of my past set-ups with the two T-1275s on inverter only with the Solar30 controller and the four 6s (two are out of sight to the right) doing the rest of the work with an Eco-Worthy controller for them. The Trimetric would only do the four 6s in that set-up.

I'm not sure why you'd need the ground to go to the other side; just find a good ground on the ground side of the RV. Maybe I'm missing something (perhaps needing a lower impedance ground than the chassis provides for the inverter).

What you post at the top is not quite balanced, as it turns out, but only pretty close. See http://www.smartgauge.co.uk/batt_con.html for a more thorough explanation, and (at the end) this nifty approach:

DrewE wrote:
I'm not sure why you'd need the ground to go to the other side; just find a good ground on the ground side of the RV. Maybe I'm missing something (perhaps needing a lower impedance ground than the chassis provides for the inverter).

What you post at the top is not quite balanced, as it turns out, but only pretty close. See http://www.smartgauge.co.uk/batt_con.html for a more thorough explanation, and (at the end) this nifty approach:

If you draw a horizontal line separating the four batteries shown you will see the positive needs to be connected on one set and the ground on the other set. If he uses existing conditions both + & - will be on same side.

The links between batts 2 and 3 will be eight feet long so there goes having all links the same :)

I chose dividing up the loads between big inverter loading on one bank and the rest on the other because it was easier to keep each bank properly looked after( no uneven charging or discharging among batts in a bank), and I was still taking advantage of having lots of battery

If you just have inverter-battery the battery does not need to be grounded to the frame. The bank doing the rest of the rig does need a frame ground to complete the neg path for several rig items that use the frame as neg.

Well, the 1275s didn't fit....... Off by about 1/4 inch on the length (Thank goodness I wasn't cutting anything). I missed an inside bracket when I measured. I was worried about height, but that was more than sufficient. I'm going to take them back and likely go T-125 in a series/parallel arraignment.

I ordered a Trimetric earlier this morning. I think it's going to be very insightful when it comes to understanding our actual usage. The new rig has a lot more toys so I look forward to seeing what the cost of using these are to my energy profile.

So, if I understand correctly I can run the series on each side (2 x t-125). Ground each of these separate banks to the chassis. Run a positive between them and a separate negative to the trimetric shunt.

Is this correct?

No. The Trimetric shunt goes straight to the one battery neg, which is not grounded to the frame there. The frame ground goes to the "load" end of the shunt with all the other negs from loads and chargers (solar and any portable chargers)

So you will still need that long neg wire between pairs as the neg parallel link but that wire does not go to frame ground.

The wire from shunt to battery has to be fat, since it carries the total of all the current on the various wires attached to the "load" end of the shunt.

You can see how it all becomes awkward when you have to use the one shunt with two pairs of batts widely separated.

You also need to give up on proper balancing by having the positives from all the "loads" go to the other pair for many of those loads. You pretty much have to go to the "upstream" pair and have nothing on the "downstream" pair, just because of wire lengths and routing the wires.

The shunt can only hold so many wires and stacking lugs isn't such a good thing anyway, so you can have a wide neg buss on the load end of the shunt and then can attach many lugs along that.

I added a copper pipe to mine as seen in the photo, so I can clamp several items to it using clamps, such as when I use more than one portable charger at a time to add their amps.

The chassis itself cannot replace the long ground between banks, right?

Corrected PIC

Really need the shunt on the other side to keep the batteries balanced.