So, I just bought a new 5th wheel toyhauler. It currently has a single 12v battery. I want to seriously upgrade the battery capacity. I had 2 Costco 6v golf cart batteries in my last rig. I think I want to go to 4 batteries in the new RV. I'm interested in the Trojan T-1275 (12v 150AH at 20hr). I can get them for $158 each plus core locally.I have space for 2 batteries on each side of the RV. This means I would have to run cable between the sides, which looks like it will be fairly easy. Some more variables. I currently have 150 watts of solar with a Zamp charger. Looking to upgrade to ~450 watts. I also have a 2k watt pure sine wave inverter.Here is how I *think* it should be wired.This would require 3 wires (1 power and 2 ground) to the other side of the RV. I'm thinking some like 1/0 or 2/0 for these runs.So, my questions are these. Is it ok to have the battery banks spread apart like this? Is 1/0 big enough?

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.

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-FHmFNjoHere 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.

Battery Upgrade | Good Sam Community

pianotuna
Nomad III
Nov 11, 2015
Yup, that is balanced and the best way for 6 six volt jars.

Supereri73 wrote:

I think this shows your last suggestion. Please let me know if I still don't have this.

Thanks to everyone for all the GREAT feedback on this!!!!!!!
MEXICOWANDERER
Explorer
Nov 11, 2015
Heel and a toe and a heel and a toe, and slide-slide-slide.

One of the bigger mistakes I see with golf car batteries is a tendency to want to bolt a large lug down onto a relatively tiny post. Unless they've changed designs, a well positioned automotive type clamp is a hundred times better. Or to prove the point, load a thousand watt inverter heavily for a minute then run down to the batteries and feeeeeeeeel the energy with an almost burned finger tip. High amperage versus the stud contact area do not jibe. Not even close. This is why standard issue for an L-16 is an L-pad post.

For lesser amperage, no sweat. For big inverters, sweat...
mchero
Explorer
Nov 12, 2015
Something else to throw in the mix folks.

Should their be a 300Amp fuse between the inverter & positive post?

I have zero gauge between the positive inverter post and the batteries BUT that &^#$ fuse heats up! Not hot enough to burn but hot. Not sure what I'm loosing thru it. Ideas?
time2roll
Nomad
Nov 12, 2015
I would sooner build a custom battery box to vent outside vs pull wire between those two small compartments. Maybe go back to the 12v or even L16(6v) if you want to go big. Consider AGM and skip the venting in the large compartment.
DrewE
Explorer II
Nov 12, 2015
mchero wrote:
Something else to throw in the mix folks.

Should their be a 300Amp fuse between the inverter & positive post?

I have zero gauge between the positive inverter post and the batteries BUT that &^#$ fuse heats up! Not hot enough to burn but hot. Not sure what I'm loosing thru it. Ideas?

Absolutely there should be a fuse or circuit breaker there. If you think the fuse is getting hot, consider what a short circuit would do; several thousand watts being dissipated is no laughing matter.

You could measure the voltage drop across the fuse under load pretty easily with a decent voltmeter. It might also be good to check that the connections to the fuse are good and tight and clean; quite possibly some of the heat isn't due to the fuse itself, but due to a resistive connection there. (That would incidentally also tend to cause the fuse to blow earlier than it otherwise should, since it's basically vaporized by heat when it blows.)

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