Adding a 3rd Lithium battery

[Marine359]

If it’s not practical for you to mount bus bars and run your dc loads there, you can accomplish the same thing by matching resistance on the cable for the 3rd battery. So, if you now connect 2 batteries with 3awg wire, your drop is .099%. If you run a 4ft 1/0awg wire from 3rd battery to the other 2, it’s drop will be .098%

[Marine359]

It may not be practical to match length and be able to connect loads. You can accomplish almost the same thing by matching cable resistance. If your 2 batts are connected with 2ft of 3awg, your drop is .099%. A 4ft 1/0awg from the 3rd batt would have a drop of .098%. You can play around with the numbers based on what you have.

[AJMike]

Originally Posted by al1florida

Do you mean to say that if the 3rd or more batteries have to be located 4 feet away that you should then lengthen the battery cables that are on the original batteries to the same length as the cables for the new batteries?

I would think you would have to do that if you wanted to keep all the cables the same length.

So you are suggesting that one solution would be to increase the length of the connecting cables on the two existing batteries to match the length of a 3rd? I have to admit that I never even thought of doing that.

[AJMike]

Originally Posted by creativepart

Optionally the Ekko can have over 600 aH of lithium batteries to make it even more practical.

Winnebago makes you choose between one 315 AH Lithium battery and a generator or two Lithium batteries without a generator. I spoke with a tech at Lichtsinn and they said that they can add an addition Lithium battery to either configuration so you could end up with three Lithium batteries for a total of 945 AH. I assume you could actually run the AC then, although you would still have to figure out how to add the power back in.

[AJMike]

Originally Posted by DavidM

Anyone know which make and model A/C unit is in the EKKO?

The local Winnebago dealership told me that they expect to have some show models of the EKKO in the middle of next month and that they would let me know when they arrive so I could see them. I will check the AC model then and post that information.

I have to admit to being very interested in that new model, although only in the 24C. There is a lot of appealing stuff - turn signal cameras, ducted AC, AWD, the 315 AH batteries, the 450 watts of solar, an enormous outside storage area, a coach that is well insulated (and hence will keep the cool in the summer as well as the warm in the winter) and the EcoBoost gas engine. That is a lot of appealing stuff in a small package and I am anxious to see it.

[Marine359]

No sir.
I’m suggesting you measure the length of your exiting parallel cables (I assumed 2ft), and determine the thickness of the cable (I assumed 3awg). Then go to the voltage drop calculator to determine your existing voltage drop. Then enter 4ft into the calculator for the 3rd battery, and use 1/0 for the wire gauge. If you buy a 4ft wire, you want the voltage drop to be as close as possible to the drop across your existing cables. If it’s close then you don’t need to change the existing cables.

[al1florida]

Originally Posted by AJMike

So you are suggesting that one solution would be to increase the length of the connecting cables on the two existing batteries to match the length of a 3rd? I have to admit that I never even thought of doing that.

Kind of. Build a bus bar at an equal distance from the new batteries and the existing batteries. Then all the cables from inverter, the RV and alternator goes to the bus bar. Now the cables from the both sets of batteries are equal distance and the balance is pretty much even. Then all the cables from inverter, the RV and alternator goes to the bus bar.

[Marine359]

I am now installing LiFePo4 with 2ft 1/0awg connected to covered bus bar (negative through monitor shunt), and 2,000w inverter/Charger with 12inches 1/0awg to bus bar using 300amp terminal fuse (through a disconnect). My wire runs are short and fat. Virtually no voltage drop between battery and inverter.

[orangeminnie]

Originally Posted by AJMike

I currently have 2 Battle Born Lithium batteries in our 2018 Winnebago Fuse and have been thinking about adding a 3rd battery. The two batteries generally are more than enough and I have never found myself lower than about 55-60% SOC in the morning when we are dry camping but have been thinking about being able to run the roof AC for a short time in the middle of the day, and I don't think that 200 AH is really enough for that.

The problem, of course, is that there is no room in the battery tray for a 3rd and I would have to add it separated from the other two or, alternately, find a location where all 3 could be mounted together. BB told me that there might be a balance problem if a 3rd battery is mounted separately from the other 2 but I have to admit that I have no idea what a "balance problem" really is, how serious it might be or what its affects might be. The installer that BB recommended is all for adding the 3rd battery, but then he sells them as well as installs them so he is probably not the best person to ask.

Hopefully someone here can give me some information. This is completely optional - I can do what I do now and run the generator - but my wife really does not like the noise and smell of the generator and if I could find a reasonable way to avoid it for an hour run, then it might be worth the time and trouble. We are almost always dry camping/boondocking so any neighbors we have are usually far enough away that they don't hear the generator but it would also be nice to be able to not use the gen if anyone is close enough to hear it.

I realize it would mean that I would still end up having to add that charge back up, but if necessary I generally do that by running the generator when we go for our late after walk so neither of us has to listen to it and, as I mentioned, we almost always boondock so the neighbors are far enough away that they don't have to listen to the generator either.

Any information would be appreciated.

--This distance to the 3rd battery is less important than having a equal wire distance from each battery to the load. The plus and minus wires should come off of the "opposite corners" of the parallel battery array. We recommend 4/0 wire throughout (at least 2/0).

--Yes you definitely can run a 13.5 AC on a 2000W inverter IF a Soft-Start is installed. We're doing it now, also with 3 BB batteries.

--Hold fast to your desire not to use the generator, whenever possible. We appreciate it!

[AJMike]

Originally Posted by orangeminnie

-
--Yes you definitely can ran a 13.5 AC on a 2000W inverter IF a Soft-Start is installed. We're doing it now, also with 3 BB batteries.

--Hold fast to your desire not to use the generator, whenever possible. We appreciate it!

What do you find the current draw to be?

[orangeminnie]

Originally Posted by AJMike

What do you find the current draw to be?

When the compressor is running, your 12V battery draw might be somewhere between 90-130A. With AC's, the startup current is the main problem, which is largely solved with the Easy-Start device. Our microwave pulls more current than our 13.5k AC.



The inverter should have a true 2000 watt capacity, not just 2000VA.

[AJMike]

Originally Posted by orangeminnie

When the compressor is running, your 12V battery draw might be somewhere between 90-130A. With AC's, the startup current is the main problem, which is largely solved with the Easy-Start device. Our microwave pulls more current than our 13.5k AC.



The inverter should have a true 2000 watt capacity, not just 2000VA.

Thank you for the information. Which Soft Start device did you use? And how much trouble was it to install? Or did you have someone else do that?

As for the generator, we dry camp/boondock a lot, and we do so to enjoy the peace and beauty of the surroundings. I don’t want to hear anyone else’s generator or TV so we don’t run the generator except for short periods when absolutely needed, and our outside speakers are turned off. Personally I wish the manufacturers would stop installing outside speakers and outside TVs, but that is just me.

[DavidM]

Originally Posted by AJMike

Personally I wish the manufacturers would stop installing outside speakers and outside TVs, but that is just me.

Thor dropped the outside TV on its 2021 Axis. I don't miss it at all.

For RV Park queens I guess I can see it. Great for a football gathering or similar.

David

[orangeminnie]

Originally Posted by AJMike

Thank you for the information. Which Soft Start device did you use? And how much trouble was it to install? Or did you have someone else do that?

As for the generator, we dry camp/boondock a lot, and we do so to enjoy the peace and beauty of the surroundings. I don’t want to hear anyone else’s generator or TV so we don’t run the generator except for short periods when absolutely needed, and our outside speakers are turned off. Personally I wish the manufacturers would stop installing outside speakers and outside TVs, but that is just me.

We installed the Micro-Air EasyStart. Between the paper and online directions, you should be able to do this yourself if you have a crimper and are comfortable around AC wiring. There are dozens of confusing sub-variations of various air conditioners, and Micro-Air covers them all with the online resources. Follow the directions to a T (including "teaching" the unit, while running on shore power), and you should be able to run the 13.5k AC on a true-2000 watt inverter.

Some inverters with "2000" in the name (including Victron Multiplus), supply far less true power (e.g.: 1450W at 40C). This is partly why there are postings that insist that only a 3000W inverter can power an AC. If they're talking about Victron (and some other brands), or any unit without a soft-start added, they're absolutely right.

We're using a Xantrex XC2000 inverter, and a Dometic Duo-Therm 13.5k AC . I've read that some 15,000 BTU units in hot weather can pull up to 1900W. I make no firm assurances for any inverter/AC combo, other than what we're using.

[AJMike]

Originally Posted by orangeminnie

Some inverters with "2000" in the name (including Victron Multiplus), supply far less true power (e.g.: 1450W at 40C). This is partly why there are postings that insist that only a 3000W inverter can power an AC. If they're talking about Victron (and some other brands), or any unit without a soft-start added, they're absolutely right.

We're using a Xantrex XC2000 inverter, and a Dometic Duo-Therm 13.5k AC . I've read that some 15,000 BTU units in hot weather can pull up to 1900W. I make no firm assurances for any inverter/AC combo, other than what we're using.

The Magnum 1000 watt inverter in our Fuse seems to be a true 1000 watts as I have seen the display showing output of more than 900 watts. And we use it to run my wife’s electric tea kettle and toaster, although not both at the same time, and they are 750-850 watts each. We have had no issues.

But perhaps the most convenient thing is that there is a remote for it already installed on the wall of the RV and I have been told that the same remote wil work for the Magnum 2000 watt inverter. I will check to see if it is indeed a real 2000 watt inverter but it would be nice to just be able to plug the remote wire into a new inverter and not have to install a new remote.

Our AC us Coleman and I believe it to be a 13,500 BTU unit. I do not know what the current draw is.

[Oldtrooper]

I don’t think the “balancing” issue has to do the either of the three batteries being charged. Lipo battery Balancing is more about the LIPO battery itself and the balancing of the cells of each battery so that no one cell is charged higher or lower than the other cells......thus the balancing of each cell as the battery is being charged. The balance makes sure all cells in each battery are charged at a rate no higher than the weakest cell. Since two batteries are close to each other the balancing shouldn’t be an issue, but if you add a third battery located farther away, the resistance of the longer cables may be enough for the balancer to think the third battery is not charging at the same rate and the balancer will try to compensate. What that compensation would be I dont know, likely longer charging time or unequal charge status on the third battery.

[jipper]

The current LI batteries have BMS systems that protect and control THAT battery.
As stated above, the balancing is the cells within that battery. I recently installed 2 - Lithionics batteries and was directed to wire each battery to bus bars so that the batteries BMS systems would not be inter wired. This would allow the individual BMS to operate and be able to balance the cells within, provided that each battery sees a high enough voltage, not necessary the same.


jipper
2019 Navion J

[Phil G.]

Mike,

It seems a better approach would be to make enough changes in your camping equipment and camping style so as to use your generator for what it would be best at - powering your A/C for extended periods whenever needed.

Here's some suggestions on what to do about better tolerating use of an RV generator:

1. Quiet the perceived generator noise down - as heard from the inside and outside - by better sound insulating the cabinet that houses it ... being careful to not disturb it's cooling air flow.

2. Reduce any excessive RV floor vibration from the running generator by changing out it's mounts to top grade isolation mounts - perhaps the type isolators used in boats.

3. Keep any generator fumes from entering the RV by pressurizing the interior. We do this all the time when using our built-in generator for long runs. We have even left our generator running nearly all night while sleeping in order to be comfortable during extreme heat and humidity.

4. An "ultimate solution" to perceived generator noise when inside the RV with it running to power the A/C is to wear noise-canceling headphones. Modern wireless headsets permit the user to both cancel outside noise while at the same time listening to music from various sources, listening to the TV, etc. via a bluetooth wireless connection. These type headphones have built-in lithium batteries to power them for many hours.

OR

You can power your RV while it's A/C is running ...this way:

[tinglett]

Originally Posted by al1florida

Here is a link to info about mismatched lithium batteries and their loss of capacity.

https://batteryuniversity.com/learn/...atch_balancing

The article references capacity, not a voltage imbalance while under load.

At one point a while back, someone posted another link to an explanation of this issue where somebody did some experiments measuring different cabling configurations. I'll be damned if I can find it, but maybe this post will jog someone's memory. For example, one basic scenario was identical cable lengths/gauges, but differing connections to a pair of batteries. What happens if you connect to a single battery's terminals vs the positive of one and the negative of the other in the pair. The drain difference was dramatic. The main takeaway was that these very tiny voltage drops are magnified greatly in how much current (and therefore energy) is extracted from each battery.

Ha, I know that statement is vague, but the problem is real. While a bigger cable is likely the solution, I believe a huge problem would be cutting it precisely to length to balance the batteries. That sounds like a serious engineering calculation to me that is far over my head to figure out. Just speaking for myself! Of course you might balance by using 6ft cables between all batteries. This sounds silly, but I imagine would work as the batteries won't care provided the gauge is big enough.

[Marine359]

When it comes to wire gauge, I’m told go big or go home. But it’s expensive. I went with 1/0 because my runs were very short. A single piece of 2ft copper 1/0 costs $19.24.
https://www.batterycablesusa.com/0-g...able-with-ends