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Old 07-22-2020, 05:10 PM   #21
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high gauge wire

If you decide to separate that third battery, make sure you use a heavy gauge wire to connect them in series. 2ga is ideal, but it ought to at least be 10ga. Otherwise, you're going to lose a lot of power.


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Originally Posted by AJMike View Post
I have a 2018 Fuse and the 2 BB batteries fill up the battery compartment so I would have to put the 3rd battery in a completely different location. I was thinking about under the dinette seat in what passes for the living room in a 24' RV. The space under the seat is split into 2 separate compartments, one holding the hot water heater (which we never use) and the other a storage area. That storage area currently holds the DC-DC charger and is well ventilated with 4" holes in the front and rear panels and a small muffin fan which operates only when we are moving.

I assume there is no problem with physically separating the batteries. The dinette compartment is about 3 feet as the crow flies from the battery compartment although if the crow has to follow the wires it may be 4 ".

As for adding the extra battery, I have not yet decided. I think I have some time because right now it is not critical. Our camping has changed significantly over the past 20 years or so. We used to always camp with hook-ups, at least electricity, and now we almost always camp without them. We just returned from Bryce Canyon and we dry camped the entire trip - 2 days boondocking and 2 days at basic no frills campgrounds - one a NF campground and the other at Bryce Canyon National Park. That scenario - no utilities - is now our common way of camping.

Fortunately for me we have one additional trip scheduled before Fall and that is the only trip we make during the year where all of our stops are with utilities. We are heading to the Gulf in August and it will be far too hot to stop without AC and that means shore power. Given that we will be making this trip completely with electric power I don't have to worry about charging the batteries.

As for charging 3 batteries, I assume a 40 amp DC-DC charger will be enough since I don't expect to have to add more than 200 amps or so with 3 batteries. That is a 5 hour drive, or less with solar power. At least that is the theory.
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Old 07-22-2020, 05:41 PM   #22
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Make that four

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Two options... make that three:
  • Get 200 or so watts of portable solar panels you can set out in the sun
  • Head to the forests above Durango, Colorado where the elevation is above 8000'
  • Buy a portable Honda generator that you can set off away from your site (and others) and use it during the day to charge the batteries you have.
A 4th option would be to go with a power station and would be my personal choice; especially adding the 3rd battery without a proper place to install it. I have the Ego power station: https://www.homedepot.com/p/EGO-Nexu...3042/305092922
Yeah, it's expensive but very versatile and manageable. We use it to supplement power to non-essential loads such as fans and coffee maker. The two included batteries get us through several days and the battery recharge is exceptionally fast to me.
There are many other brands out there that do the same but I choose the Ego because of the ability to easily remove the batteries. However, unlike the other brands, the Ego doesn't have a solar charge option.
Grant it, the 15Ah capacity of the included batteries doesn't equate to meet the 60Ah need the OP uses, but with some load management, a power station can be a good alternative compared to adding another BB Lithium with wiring.

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Old 07-22-2020, 05:46 PM   #23
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Just a thought but what about swapping to a 40 amp MPPT and seeing if MPPT is enough efficiency before adding more panels or just one more. I don't know how much more efficient MPPT is but I think it would help and in the shade likely the most?
I don't understand why I would want a 40 amp controller. Three flexible panels can only produce about 20 amps so a fourth might bring that up to perhaps 26-27 amps. What benefit would I get from a 40 amp controller? Or is that that the MPPT controllers start at 40 amps?

How much more efficient are the MPPT controllers? And more efficient in what way? Do they end up adding more power to the batteries than the Zamp type controller that I currently have?

Those are honest questions as I know nothing about MPPT controllers. I am not trying to be snarky, only to understand.
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Old 07-22-2020, 05:51 PM   #24
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Originally Posted by golden13 View Post
If you decide to separate that third battery, make sure you use a heavy gauge wire to connect them in series. 2ga is ideal, but it ought to at least be 10ga. Otherwise, you're going to lose a lot of power.
Connect them in series? I don't understand.

The 2 current batteries are connected in parallel. They are both 12 volt batteries and connected in parallel give me 12 volts for a 12 volt system. A 3rd battery would also be in parallel and I don't see how I could connect them in series since that would give me more voltage than the system is designed for. What am I missing here?
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Old 07-22-2020, 05:51 PM   #25
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I don't understand why I would want a 40 amp controller. Three flexible panels can only produce about 20 amps so a fourth might bring that up to perhaps 26-27 amps. What benefit would I get from a 40 amp controller? Or is that that the MPPT controllers start at 40 amps?

How much more efficient are the MPPT controllers? And more efficient in what way? Do they end up adding more power to the batteries than the Zamp type controller that I currently have?

Those are honest questions as I know nothing about MPPT controllers. I am not trying to be snarky, only to understand.
40 amp only gives you a bit of head room IF that's not enough. They have all the same amperage offerings as PWM controllers.

MPPT is more efficient some say 20%? - I found this blog post but maybe others can chime in. https://www.solar4rvs.com.au/buying/...erter%E2%80%9D)
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Old 07-22-2020, 06:04 PM   #26
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You have described the exact problem that we have had. We have 400aH of Lithium batteries - and they are fantastic. But we have discovered that trying to keep them charged up with solar is not always realistic - the sun does not always shine, not are we parked away from shade trees.

Your solution is not necessarily to get another battery. It might be wonderful to have that extra capacity, but you will find you now need more charging ability. I would suggest a remote 120 - 200watt remote solar panel that you can place out in the sun even when you are not parked that way.

I am with you on generator use. I hate to use mine unless I have to, BUT it has been a lifesaver to have it on occasions when I really need the power.
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Old 07-22-2020, 06:42 PM   #27
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How much solar watts do you have? I think having at least 500 watts would help better even if shaded. I use pretty much electric everything and have 250 ah of lithium and 400 watts of solar. I have a compressor fridge too. Dont have any issues recharging to 100% if in sun. Shade hurts, and I think 100 watts more for me is the sweet spot and no generator use unless totally overcast.
Exactly! It isn't just the battery capacity you need to worry about, the solar capacity HAS to keep up with your daily demand no matter what, unless you want to be a slave to the almighty generator. Batteries only temporarily hold your power and allow you to trickle it out during the no-sun off hours or supplement what solar can't handle during the sunny times. Nothing more, nothing less. Your entire electrical system needs to be engineered in balance to provide for your pre-determined needs. AJMike seems to have gotten that backwards, and he is not alone.
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Old 07-22-2020, 07:16 PM   #28
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Research before you buy another battery.

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Originally Posted by AJMike View Post
I have a 2018 Fuse and the 2 BB batteries fill up the battery compartment so I would have to put the 3rd battery in a completely different location. I was thinking about under the dinette seat in what passes for the living room in a 24' RV.
I talked in length with a battery engineer for ReLion about my setup (three 100ah HP lithium batteries) He didn't like the fact that my batteries are strung in a linear fashion with different length cables, even though I used very low resistance 1/0 welding cable. It has to do with voltage drop battery-to-battery and the BMS systems inside the batteries, which may be having difficulties balancing the system. He prefers to use big thick buss bars between the batteries that are all clustered together. My reply was, "Right!" "In an RV?" "Keep dreaming!" RVers do what we need to get by as we leave the perfect world behind. As I've said before, It isn't rocket science, but it's close. So, how much "damage" am I doing with my imperfect system? Probably (hopefully) not much. The engineer may have been splitting hairs.

Another thing that you need to factor into these chained-together multi-battery systems is where you tap off for the big draw inverter. At the end of the chain? Well, think about this. With 3 batteries connected together by various lengths of cable and you draw, say 100 amps dc for your coffee maker and assorted small loads. Each battery supplies 33.3 amps right? So battery 1 to battery 2 cables have 33.3 amps running through them and battery 2 to battery 3 cables have 66.6 amps running through them and of course, battery 3 to the inverter has 100 amps running through them. Now ask yourself, did you properly size all of the cables? Even though each battery "equally" shares the load, the cables don't. Add more batteries, add more current between the last ones before the major load. Got all of your batteries together? Well, good for you!
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Old 07-22-2020, 07:57 PM   #29
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Bobby,
Woah! $1200 for a 15Ah battery Ego powerstation?? That doesn’t sound like a good buy at all compared to one BB 100Ah battery for $925. I’m more of a mind to add a third BB in the storage bin just aft of the “under the step” existing two BB batteries in my 18 Navion 24D.
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Old 07-22-2020, 08:50 PM   #30
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Bobby,
Woah! $1200 for a 15Ah battery Ego powerstation?? That doesn’t sound like a good buy at all compared to one BB 100Ah battery for $925. I’m more of a mind to add a third BB in the storage bin just aft of the “under the step” existing two BB batteries in my 18 Navion 24D.
Yes, it is expensive but you can get a bare unit for a little less. It is the clean power and the 3000 watt capacity that makes this unit more expnsive than Jackery and Goal Zero.
I didn't think a power station would be for me but years of week-long scout camping in the woods and the desire for faster/better than campfire coffee helped me rethink. Now that I do more of my backwoods camping in the View I have found plenty of use for the power station.
It relieved me of the worry of everything I turn on was eating precious battery reserves. I now put most stuff on the power station and just leave the refrigerator, fan and lighting on the coach battery.
Plus the fact that I live in hurricane alley makes for more reason to have an alternate power source.

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Old 07-22-2020, 09:03 PM   #31
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Sorry I stopped reading at the first page.
Outside the box.
Wind turbine.
Good for 100mph
Should work in the shade.
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Old 07-22-2020, 10:33 PM   #32
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You need more solar not more battery.
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Old 07-22-2020, 10:38 PM   #33
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I talked in length with a battery engineer for ReLion about my setup (three 100ah HP lithium batteries) He didn't like the fact that my batteries are strung in a linear fashion with different length cables, even though I used very low resistance 1/0 welding cable.



This link will help you understand how to correctly connect batteries in a balanced manner. For three jars, only method #3 will work.


SmartGauge Electronics - Interconnecting multiple batteries to form one larger bank
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Old 07-23-2020, 10:45 AM   #34
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JoeC - I have read a lot about battery cable sizes,and how some want all lengths to be equalized, etc.. That's fine in theory - but as you correctly point point out when doing these installations in an RV you can only do what you can do with the available space.

Another thing to keep in mind re: cable sizes & lengths - the optimum recommendations really only come into play when you try to draw out maximum current at one time. But if you have 300aH of batteries when are you ever going to be trying to pull that much?? Unless you are trying to start your A/C you will never pull that much power, and as such unequal cable lengths become almost irrelevant. In my RV the biggest draw I have is the microwave - which pulls ~150 amps MAX through the inverter. But most of the time - 99% of the time - I am running a few lights, maybe the TV,etc, and rarely draw more than 20 amps. My 1/0 welding wire connecting all batteries to feed to my 1500 watt inverter barely notices that.

I have 400aH of mixed LiFePO4 batteries mounted where they fit on my RV. I have a 300aH Winston battery mounted under the steps - <2' from the inverter - and a single 100aH Battle Born mounted up front in front of the engine - about 9' from the steps, connected in parallel by 1/0 welding cable. So unequal cable sizes to be sure. But I mounted the batteries where I could, connected by heavy gauge wire, and everything works great. Yes there is a long cable run from the B.B. to the step battery, but it's total load will never be more than 25% of total load demand. In measuring voltage from the B.B. at the point where the cabling merges into the Winston battery it is virtually the same, In other words, with that gauge wiring there is virtually no resistance loss. And in normal low demand or resting stages the 2 batteries self-equalize voltages with each other. So again - I mounted batteries where I could in my RV layout, and things work great.

So I am back into the endless "round-about". As you add more batteries you then see how you could use more solar. As you add more solar you then see how maybe more batteries would be nice. Round 'n round you go.
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Old 07-23-2020, 11:10 AM   #35
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I just got off the Go Power web site, looking for a another 2kW inverter with AC bypass (they don't have one currently so I left them a message) hopefully more reliable than the Aims Power, that's right, AIMS POWER unit that I got less than a year ago and I'm not happy! (the AC bypass shorted and trips shore power breaker). Anyway, on the Go Power site's web page (https://gpelectric.com/calculator/) is their solar power calculator. Just answer several questions about your rig and electric appliances and magically the amount of solar required to support your system is calculated. I tested it out with my data. It came in quite close to my own calculations, validating my 300ah lithium with 400 Watts solar.

I've done other rough checks with other popular and respected RV individuals who installed solar and came up with an approximate recommendation of 1.25 to 1.33 times your lithium battery amp hours for your solar panel Wattage. All bets are off for lead acid batteries of any type as their charge profile is substantially different and take forever to charge at 50-60% efficiency. My personal guess would be to double the battery amp hours for solar Wattage when using lead acid batteries.

I hope that this helps some of the somewhat less than qualified do-it-yourselfers out there in RV land who are looking to go solar. Best wishes and happy camping. :-)
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Old 07-23-2020, 11:35 AM   #36
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JoeC - I have read a lot about battery cable sizes,and how some want all lengths to be equalized, etc.. That's fine in theory - but as you correctly point point out when doing these installations in an RV you can only do what you can do with the available space.

Another thing to keep in mind re: cable sizes & lengths - the optimum recommendations really only come into play when you try to draw out maximum current at one time.
I don't mean to be "picky" or demeaning but in the dirty details of lithium battery design and operation (the rocket science), the different minor voltage drops across those battery interconnect cables (smaller sizes and longer cable have more resistance and therefore more voltage drop) could, and probably do, mess with the battery's internal BMS. Is this a big deal? I don't know and hazard to guess, very few people actually do know for sure because they live and test in the "perfect world" and are not likely testing RV-style Frankin-battery systems.

The thing you are on the money about is big current draw over long or undersized cabling is heat buildup in the cables. Draw enough current and they will act like a fuse experiencing thermal runaway. This may be an extreme example but it illustrates the issue. Long and or undersized cables have more resistance, lose more power and heat up as a reaction to the additional resistance. Moral of the story is: Go big or go home when it comes to electrical cabling in the RV. Err on the side of big, not cheap, especially when building non-conventional systems.
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Old 07-23-2020, 11:36 AM   #37
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JoeC - Your recommendation for solar capacity vs. battery of 1.25x is a good one - but I have found both to be important.

For example - battery capacity is what one has to work with once charging is done for the day (assuming no shore power). No more solar charging, no more driving, and no more running the generator. The point is that solar is only 1 method of charging up house batteries, and while your capacity suggestion is very valid - I think many will appreciate having more batteries to work from.

In my RV when driving the engine can supply >70 amps of charging power. Also when driving we usually travel on good weather days so we not only get lots of sun while driving but we are also not using any house battery amps. I find that on most driving days we reach 100% charge state by early afternoon. So having more battery capacity is great to be able to capture that.

However - on the other side of the coin - it is much less expensive to add solar capacity these days as the price on panels has fallen over the years. Certainly cheaper than having to buy another $950 B.B. battery.

But it is good to have extra capacity in both areas.
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Old 07-23-2020, 11:44 AM   #38
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Don't know why cable sizing has anything to do with the internal BMS of a battery. Batteries simply work on voltages. My remote cabled B.B. battery still receives the 14+ volts my charging systems supply it. As long as voltages are stable & consistent then it's BMS is happy to do it's job. It has no way of "knowing" connected cable lengths - it only sees the voltages coming to it, and what it's own internal cell voltages are.

As for cable sizing - remember that electrical resistance is a factor of load - amperage. In low power situations (99% of the time)(charging or discharging) there is little resistance, so voltages are stable. My remote B.B. essentially sees the same system voltage as my larger Winston battery. The reason for wanting large cable sizing is to help supply the amps under load, in order to keep the voltage as high as possible.
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Old 07-23-2020, 12:59 PM   #39
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So battery 1 to battery 2 cables have 33.3 amps running through them and battery 2 to battery 3 cables have 66.6 amps running through them and of course, battery 3 to the inverter has 100 amps running through them.
Correct me if I am wrong, but that is only true if the batteries are connected in series. Right?

My batteries are connected in parallel and any third battery would also be in parallel so presumably the load would be balanced properly between the three batteries. Or am I missing something here?
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Old 07-23-2020, 01:10 PM   #40
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I used very low resistance 1/0 welding cable.
A question.

I moved my DC-DC charger because it did not have enough ventilation in the location the installer used and it was overheating and the output was dropping to 0. I moved it and that meant I had to add about 3 feet of 6 gauge wire to the existing 6 gauge wire but I believe the total length now is above the recommended distance for 6 gauge wire for there charger installation. I asked a repair guy to replace it with 4 gauge wire, which is the recommended size for the cable length.

He told me he uses welding cable and I suppose that is better than 4 gauge wire, but I was wondering what the equivalent gauge would be for welding cable. I know little to nothing about practical electrical connections (I know a lot more theory than I have practical knowledge thanks to all of those Physics classes but have a severe lack of Shop classes).

And what does the 1/0 represent in your post?
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