About to buy an AGM battery bank. Anything new or economical I should consider?

[Withalligators]

Wow, that was quick, sir. You are on point! A tube of what? Some dielectric grease or something? EDIT- I see, thanks!

[Sunking]

Can I oversize them in case I decide to put a large inverter in down the line? IE, can I use 2/0 cables with copper terminals?

Absolutely, requirements are minimum for safety. As for the battery end of the cable lead plated copper is best but not required. Get online and order a small tube of Sanchem NO OX ID A Special. Coat all connections lightly and it will last and protect electrical connection or any metal until you bury your grand children. There is no better product at any price

[Withalligators]

Can I oversize them in case I decide to put a large inverter in down the line? IE, can I use 2/0 cables with copper terminals?

Also, I think I'm going to have to go back to Lifeline 2Vs. Despite the sun xtender line being built for solar, they aren't warranted for mobile use. With the Lifelines, I get 1 year full, plus a 5 year pro-rated. I'm trying to decide on an alternator charging solution. I had the Samlex ACR-160 in my old rig. This provides whatever the alternator is producing, but would a DC DC charger be smarter? They're about 3 to 4 times as expensive, but then I'm not taxing the alternator as hard, and getting a constant charge (I would go with a 60A) in my case. I could also use it for a lithium bank if that ever becomes feasible. How many amps are the Lifeline AGMs capable of absorbing do you think?

[Sunking]

Copy that. Never solder terminals again. What about the inter-cell cables, what gauge should I use? I can probably order premade ones, right?

Same size as the largest conductor you use to the loads. You can order cables. Let me know if you need help with that and what gauge.

[Withalligators]

Copy that. Never solder terminals again. What about the inter-cell cables, what gauge should I use? I can probably order premade ones, right?

[Sunking]

Using non-equal-length wiring for series strings is not a "sloppy wiring practice." Indeed, if going to unequal length wiring in such cases minimizes total cable length, that would be considered best practice.

Allow me to pile on so he is so discredited and embarrassed he never comes back.

You got it backwards. Non equal lengths compounds the problem for PARALLEL batteries you idiot. You are on my radar and a target. You are also on the moderators radar and other engineers ready to attack you. Understand? Now go away.

[jflorey2]

It is not a technical issue with series battery banks . . . . .

So to sum up - your claim that "If the cable lengths are asymmetrical from the midpoint to both end points, there will be a voltage imbalance across the batteries" in series strings is incorrect.

Good, now that that's out of the way -

If others choose to teach sloppy wiring practices and deal with the fall out later, that is their decision and they can deal with the fallout.

Using non-equal-length wiring for series strings is not a "sloppy wiring practice." Indeed, if going to unequal length wiring in such cases minimizes total cable length, that would be considered best practice.

[Sunking]

For my last series bank, I used 2/0 cable, with copper terminals that I crimped at West Marine, soldered afterwards, and then used heat shrink tubing on to cover as much as possible. Is that enough?

OK I just caught this after Mike pointed it out. I do not take any issue with over sizing if some conditions are met which I will get to next. What I have a big problem with is SOLDER. Time to ge ton my soapbox. For Pete's Sake and yous personal safety do not ever do that again. This is not an opinion, professional fact. A lot of property has been destroyed and many people have died from soldered connections. There is a good reason the FAA (aerospace), SAE (automotive), and USCG & ABYC (Marine) industries forbid the use of solder, and NEC severely restricts it use to state can only be used if the connection mechanical and electrical connection does not depend on solder. Short story it solder is weak and a poor conductor.

Stick with properly compressed compression terminals using approved tooling and terminals. A properly terminated terminal is stronger the the wire it is connected to and the extreme pressures homogenize the conductors effectively weld them electrically for the lowest resistance possible. So I have no issue over sizing cables. But with any of them larger than 6 AWG, have a Marine, Cable Shop, electrician, or buy terminated cables. Consumers just do not have the tooling and experience.

OK off my soap box.

What I do suggest for all RV users out there is use Marine Rated Cable and Devices. To size your wiring needs use the following table 3% column. Example if you have a 50 amp fuse and 1-way distance will require 4 AWG.

[Withalligators]

Excellent info. Thanks! You guys are super helpful and I appreciate it.

[Mike90250]

For my last series bank, I used 2/0 cable, with copper terminals that I crimped at West Marine, soldered afterwards, and then used heat shrink tubing on to cover as much as possible. Is that enough?

It's overkill. Soldering is harmful, because it
a) wicks solder up the cable in an uncontrolled manner
b) the heat of soldering damages the insulation
c) a properly crimped connector is gas tight, and has no room between the strands to wick solder into the joint
d) if a connector relies on solder, under high amps, the solder can melt and let the wire fall out

Oh, I've been wondering this, can the cables connecting the batteries in series be different lengths?

In series, all current is equal at all points, excess length just means a bit more total resistance in the circuit

[Mike90250]

It depends. If the cable lengths are symmetrical from the midpoint to both end points, It will be OK. If the cable lengths are asymmetrical from the midpoint to both end points, there will be a voltage imbalance across the batteries. Keep it as symmetrical as possible and the shortest possible lengths best results.

You get another vacation to learn how a series circuit works. Don't rely on you-tube idiots to teach you.
Continue giving erroneous information, and you get longer vacations.

[Falsa_Nominis]

Why would it matter? The current is the same in all batteries in a series string.

It is not a technical issue with series battery banks, it is a best educational issue and a it is a preempt.

Many people will undersize the battery bank because they do not develop an energy usage profile before building the system. By the time they realize the mistake, they will be economically locked into a battery bank voltage. Their only economical option will be to expand the battery bank by going to a series-parallel battery bank.

Over the years I have tried to get people to develop energy usage profiles before building but the success rate is not very good. Many either cannot do the math or they choose to follow somebody else that does not understand the value of an energy usage profile.

By teaching people to be uniform with series interconnect cables, I am teaching them a practice that can benefit them later.

If others choose to teach sloppy wiring practices and deal with the fall out later, that is their decision and they can deal with the fallout.

[Sunking]

It depends. If the cable lengths are symmetrical from the midpoint to both end points, It will be OK.

Do not listen to this idiot. He s as dumb as a rock giving bad and dangerous advice.

Mods nuke this SOB before he gets someone hurt.

[Sunking]

Oh, I've been wondering this, can the cables connecting the batteries in series be different lengths?

No problem at all providing the cable size is adequate. You wil most likely be using over sized cable, so nothing to worry about.

[jflorey2]

It depends. If the cable lengths are symmetrical from the midpoint to both end points, It will be OK. If the cable lengths are asymmetrical from the midpoint to both end points, there will be a voltage imbalance across the batteries. Keep it as symmetrical as possible and the shortest possible lengths best results.

Nope. Cable lengths don't matter in series batteries (provided they are adequately sized to handle the current at that length, of course.)