Batteries

clev-THOR

Senior Member
Joined
Oct 11, 2017
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330
Location
San Marcos
I currently have 8 6-volt deep cycle batteries in my tlr. They were bought in ?Jan?, 2017, so at 8 years, they pretty much oos. I have a long trip scheduled for the end of May, if my disability will permit. I am going to replace them with lithium. Question: Is it better to have 8 6-volt lithium or the equivalent with 4 12-volt. Any advice is appreciated.
 
I currently have 8 6-volt deep cycle batteries in my tlr. They were bought in ?Jan?, 2017, so at 8 years, they pretty much oos. I have a long trip scheduled for the end of May, if my disability will permit. I am going to replace them with lithium. Question: Is it better to have 8 6-volt lithium or the equivalent with 4 12-volt. Any advice is appreciated.
Come on, guys and gals. I know some of you have lithiums. Advice is appreciated. Gotta get this done within the next couple of weeks.
 
I currently have 8 6-volt deep cycle batteries in my tlr. They were bought in ?Jan?, 2017, so at 8 years, they pretty much oos. I have a long trip scheduled for the end of May, if my disability will permit. I am going to replace them with lithium. Question: Is it better to have 8 6-volt lithium or the equivalent with 4 12-volt. Any advice is appreciated.
You want four 12 volt lithium batteries. I am not aware of 6 volt lithium batteries that are commercially available, but lithium does not have the same limits as lead acid and you would gain nothing doing double 6 volts versus a single 12 volt with lithium. Four 12 volt lithium batteries are going to give you approximately double the battery capacity you had when your eight 6 volts were brand new. If you don't need that added capacity, you could cut back to two new lithium for approximately the same capacity or even 3 for a 50% increase. Of course this assumes you buy lithium that are rated for similar amp hour ratings. Good luck and enjoy!
 
Thank you dt. I am aware of 6 vs 12 volt batteries. One of my 6 volts had 205 ah, so it took two to get 12 volts at the same amps. My 8 6-volts, gave me a bank of 4 12-volts at ~820 ah, with weight at ~500 pounds. That’s about the limit of my knowledge. I’ looking at 12 volt lithium, 300 ah each, at 55 pounds. So 6 of them would give me 1800 ah, at about 330 pounds. But are the 12’s as good as the 6’s? Are they as good with longevity? Do they hold their charge without discharging too quickly?
 
Thank you dt. I am aware of 6 vs 12 volt batteries. One of my 6 volts had 205 ah, so it took two to get 12 volts at the same amps. My 8 6-volts, gave me a bank of 4 12-volts at ~820 ah, with weight at ~500 pounds. That’s about the limit of my knowledge. I’ looking at 12 volt lithium, 300 ah each, at 55 pounds. So 6 of them would give me 1800 ah, at about 330 pounds. But are the 12’s as good as the 6’s? Are they as good with longevity? Do they hold their charge without discharging too quickly?
You are going to love the lithium! Lithium 12v are way better than your old 6v in series/12v parallel setup. First is the obvious weight savings - always nice. But your planned six 12v lithium batteries giving you 1800 ah is actually not just doubling your usable capacity, but actually it will basically quadruple your old capacity. The really nice thing with Lithium is the very flat voltage curve. Unlike lead acid batteries that lose voltage as they discharge, lithium voltage stays really consistent until they are nearly 100% discharged. For this reason, you can run them until they are virtually 100% discharged without damaging them, where lead acid begins to see long term damage anytime you go below 50% capacity and are considered dead at that point.

They will also hold a charge a lot longer than lead acid while in storage. It is best to store them at 80% or less charge, but they will hold that for months. I had some that sat on a shelf for 22 months and only dropped to from 80 to 73%.

As for longevity, most are rated at a minimum of 4,000 full cycles. That means the approximate equivalent of discharging from fully charged to less than 10%, 4,000 times. So if one is fully charged and discharges to 50%, that is eqivalent of a half cycle - doing it twice equals 1 of the 4,000 cycles. In a nutshell, if you fully discharge the batteries every day of a year (365 times), they will last eleven plus years! Longevity is a strong point!

When you install them, you do not want the negative and positive cables from the RV going to the same battery. It's best to have the positive cable on one end of the bank and the negative on the farthest away negative terminal. Also use as large cables as possible and make sure all the cables are the same size and length. The reason for all of this is that lithium batteries are very sensitive to resistance and will pull power from the battery with the lowest resistance if possible. By putting the cables at opposite ends, it fools the batteries into "thinking" they are just one big battery - and equal size and length cables make that equation even stronger.

One other plus is that lithium batteries do not off gas and there is no corrosion of the terminals or cables. If you are investing in six lithium batteries, I would advise you to invest is a couple of other items. See below:

1. A "shunt" with either a readout or Bluetooth (or both) capability. This is a unit (I prefer Victron brand personally) that tells you the status of your battery banks charge. Unlike lead acid, where you can watch voltage drop for the battery's state of charge, as described earlier, lithium batteries maintain an almost flat voltage curve until the very end and then they shut off quickly. The shunt mounts on the negative terminal between the negative RV cable and the post. By doing this, it reads the actual amp hours/wattage consumed and tells you the accurate status of your available power. It is definitely worth the expense.

2. All new battery cables. If there is any corrosion in the old cables, and after 6 years it is almost a given that there is, there is no way to balance resistance. New, big cables are worth the spend.

3. A Converter- Charrger that is lithium compatible. A non compatible one will still work, but will only charge the batteries to 80-82 percent of capacity. This is not a huge problem if you don't need 100% of the amp-hour capacity, but it does impact that by about 20%. Also lithium can charge a lot faster than lead acid batteries and a compatible unit aids the faster charging benefit.

4. Finally, if you don't already have it, solar charging works phenomenally well with Lithium. You can go mild to wild on a solar system, but even a modest system will add substantially to your power storage - and greatly lessen generator or plugging in requirements.

Two last items. I did not catch where you live or the type of camping you do, but lithium does have one, fairly major, drawback. That is extreme cold weather. They will discharge just fine down to -4 degrees Farenheit internal core temperature and will then taper off fairly quickly, but you absolutely cannot charge them below 32 degrees Farenheit (freezing) internal core temperature. Trying to charge at colder temperatures will quickly destroy the battery. Make sure that whatever batteries you are looking at have built in low temperature protection. Some also have built in heaters, but if they are discharging or charging, they create their own heat. I definitely don't want to destroy my batteries and would not buy a new battery today without built in freeze protection, but I'm not yet sold on the benefit of internal heaters unless you know you will be camping in those extreme temperatures.

Finally, some will tell you that you cannot start your generator with Lithium and some manufacturers warn against it. This is due to their low ability to provide short term, high end rush, voltage, and is a problem in small battery banks. I started an Onan 7KW gas generator in our last 5th-wheel toyhauler with just two Lion 1300 100AH 12v batteries in parallel operation just fine. I currently have a motorhome with a 12.5KW Diesel generator and also start it with my lithium bank, but it is a substantial bank of batteries. As long as you go with your current plan, you will be able to start any RV generator you may have!

I absolutely love our solar/lithium system on our RV and truly hope you find it to be everything you were looking for. I think I've about depleted my limited knowledge on this topic and if others correct me, that is great as we all learn, but this is what I've learned in 5 years of dealing with Lithium and I would never consider a lead acid battery as a suitable replacement.
 
Wow! Thank you for all the information. The wiring for the 6’s had the ground at one end of the string and the positive connection on the other. It worked well. I found a better wiring solution called “Balanced Efficiency”, with a slight modification for 6 batteries.
1746546712105.jpeg

Thank you for taking the time to give me a good lesson. I’m printing it out to keep with my files in the RV.
 
I just increased my battery bank to six of Lynac Lithium State series 150 AH batteries. I installed two last summer along with four 220 W solar panels. We spent the winter touring around Arizona and the system worked very well. So I decided to increase the system capacity. We have a large 5th wheel and I moved the batteries from the cold front storage to the mid section to utilize what was essentially unused space occupied by only some plumbing and cabling, which I worked around. I will be adding four more panels this summer. I'm using Victron controllers and their Smart Shunt. I opted to use copper flat bars for the battery bank interconnections instead of a bunch of short cables. I didn't try to figure out which method would be less expensive, but I did find out that copper bar is not cheap these days! The main feed from the bank to where my DC distribution is uses #3/0 size welding cable. I know that the ideal would be to have equal conductor lengths from the bank main connection point to each battery terminal to help ensure equal current distribution to each battery, but in the real world, this was as close as I got. The battery BMS circuits can do their thing. Here's a photo after I got it laid out ready to put into its new space. The 6th battery is connected to the RV to operate the lights while I'm working on this. The Smart Shunt is at the left end.
1746548076625.jpeg
 
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Wow! Thank you for all the information. The wiring for the 6’s had the ground at one end of the string and the positive connection on the other. It worked well. I found a better wiring solution called “Balanced Efficiency”, with a slight modification for 6 batteries.
View attachment 1113910
Thank you for taking the time to give me a good lesson. I’m printing it out to keep with my files in the RV.
I am glad I was able to help you out and please dont hesitate to ask more questions. If I dont know the answer, I probably know someone who does!

I like that cable layout and it triggered another thought that I missed yesterday. The absolute best way to wire multiple batteries in parallel is to install a positive and a negative buss barr and run equal length cables from each battery to the buss bar. This makes it easy for the system to see one large battery, but also important, it is easy to remove one (or more) battery from the system (maybe to verify capacity or some maintenance need) without any disruption to the overall system. You just disconnect and isolate two cables and you can remove a battery - no making sure they are all wired right after removing one.

Mine is this way and I pull five of my six batteries and charge them to 100% while the system is running on the one battery. I then shut it all down while I charge the last battery to 100%. I then reinstall all six batteries and start the system again.

Two things here. First is that it is critically that all the batteries are fully charged when you start using them. This balance assures they will be used as equally as possible by the system. Secondly, if one starts out low in parallel, it will tend to steal power from the others and lower your available power - when they recharge, they will also tend to think they are all full when the lower one is saying it is full. Balancing them at install and again annually is my practice.
 
I am no familiar with bus bars and am looking at yours very carefully. I am interested.
In my case the bus bars are 1" wide by 3/16" think copper, and I insulated the positive bars with heat shrink tubing. Each battery is also fused on the positive terminal. Some lithium batteries have the fuses built in, but not in my case, so I used Blue Sea fuses & terminals, as opposed to some of the cheaper versions available on Amazon etc.
 
One final question, DA. I finally decided on three 300 amp batteries for 900 amps; plenty for my uses, with 600 amp solar. With a foot print of 13x7.6, only one will fit in either of the front battery trays. So, I would have to string them out, one left side tray, one right side tray and one in the belly by the belly slide out. Even though I'm using 4/0 cable, I don't like them strung out that far apart. They fit, end to end, on the front side of the belly tray, but the end one is really snug. Is that snug fit a problem? Do the batteries expand with use? I'm completing this install today, and would appreciate your advice as soon as you can.
 
Now, a few more problems. I had called Magnum a few years back and tech spt informed me that the system could be set for a work around in Settings to manage Lithium's. I called yesterday, and Magnum is out of business. So, not sure how to set up the ME-RC controller. Anyone have any suggestions? The first problem is 'Battery Type'. Choices are Gel, Flooded, and AGM's 1 & 2.
 
Got it done today. Biggest problem was cutting and fitting the 4/0 cables. Watched some You-Tube videos on the ME-RC set up for LifePo4. Still a little uncertain on some setting.
 

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One more problem. The positive battery cable, at the circuit breaker, on the lead battery, gets extremely hot. I had the current set to 80 amps, and that popped the 300 amp breaker. Setting it down to 50 amps is still very hot but does not trip the breaker. These are 300 amp batteries with a built in BMS of 200 amps. is this heat normal?
 

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