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Old 07-10-2019, 12:00 PM   #15
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I really wasn't planning on stepping on anyone toes.

My primary objective was to make sure the everyone knew that some voltage drop calculators don't automatically calculate for round trip distance. They assume the user knows to put the number of feet to the load and back to the source.

Also some calculators do automatically calculate the round trip distance. How that is not doubling the distance I am having difficulty understanding. So ignore the word "double" and just use the "round trip" distance.

So if someone is installing solar panels and measures the distance from the solar panels or combiner box to the controller and comes up with 25 feet. They know they want no more than a say 2% voltage drop and just put the 25' into the calculator they may not realize they may wind up with a 4% voltage drop. Next comes the wonderment as to why they are not getting the power out of the solar panels the expected. Gee I designed everything as I thought I should, but it just isn't working as well as I planned.

The same thing happens with say 3 feet of distance between the battery bank and the inverter/charger and the 140 amps of 12V DC going to the inverter to run the microwave. Yes, I do realize that one of the cables, either plus or minus, may be 3 1/2 feet or maybe 4 feet long to reach the terminals, so that should be taken into consideration. So here the word "double" would be incorrect.

What really gets to be interesting is when you calculate the voltage drop from the solar panels to the combiner box, and don't understand you have more voltage loss than you planned for, then do that again for the distance from the combiner box to the controller and again for the distance from the controller to the batteries.

Hopefully people get the idea that you can have a lot of combined losses that will amount to the installation not preforming very well.
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Old 07-10-2019, 05:15 PM   #16
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All of my runs between batteries are 12”, so minimal loss at that length. The cables into the coach are existing, and I am inclined to leave them as is, since the coach is brand new.

I will try to make all cables the same length for balance.

I will be doing the switchover this Sat., so will let all know how it goes.

One last question - I have read (and it seems to makes sense) to cut all power at the circuit breakers before disconnecting the batteries - I haven’t researched this much as to which breakers to throw....but I did find them in the coach so that’s a start. Any advice on this would be appreciated.

One fun thing I will share - the nice guys at the battery store gave me a lifting strap for the Trojan T-105’s, which really helps they are > 60 lbs, and no good way to lift them without the strap. So, I get the batteries unloaded and set out in the driveway, ready to load up on the trailer in the morning. Covered it up with a tarp, and put the handle on top of the tarp, so I know where it is.

As it turns out, one of our border collies assume that the strap is a play toy, and take off with it, never to be found, at least until I mow the lawn tomorrow. I rigged a strap out of a piece of 1/2” nylon rope and 2 caribiners to get the batteries loaded. It’s always something with these dogs (we have 4) - I luv them, but they can be a pain sometimes!

Thanks all. John
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Old 07-10-2019, 07:59 PM   #17
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There is no way to manually switch a Winnebago circuit breaker from on to off. You can operate both the chassis and coach battery disconnect switches before you start before disconnecting any coach battery cables to move both the chassis and coach battery disconnect latching relays into the open position. This will make totally sure you can't energize anything while working on the batteries.
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Old 07-10-2019, 09:17 PM   #18
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What you don't want is to have a heavy load on the batteries when you disconnect or connect the cables from the battery. Heavy loads causes big sparks and surges. Turn off all the lights and turn off the inverter. You may have to read the manual to find out how to turn off the inverter. I have never removed all the 12V fuses or turned off all the 12V C/B's. I just turned off everything and made sure to disconnect from shore power and have the generator off.

Next, remove the negative cable(s) first and then the positive cable. With the negative cable(s) removed, even if your wrench shorts the positive battery post to the metal frame of the RV, there is no return path to the battery, so no harm done.
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Old 07-11-2019, 04:56 AM   #19
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Quote:
Originally Posted by John Vista View Post
....
One fun thing I will share - the nice guys at the battery store gave me a lifting strap for the Trojan T-105ís, which really helps they are > 60 lbs, and no good way to lift them without the strap. So, I get the batteries unloaded and set out in the driveway, ready to load up on the trailer in the morning. Covered it up with a tarp, and put the handle on top of the tarp, so I know where it is.

As it turns out, one of our border collies assume that the strap is a play toy, and take off with it, never to be found, at least until I mow the lawn tomorrow. I rigged a strap out of a piece of 1/2Ē nylon rope and 2 caribiners to get the batteries loaded. Itís always something with these dogs (we have 4) - I luv them, but they can be a pain sometimes!

Thanks all. John

The BEST post in this entire thread! Every time my 92lb GS sees a piece of rope or something that vaguely resembles those big tug ropes he takes the thing and hides it as HIS toy. We learned pretty early about this trick, he was a rescue. Getting grey beard now like me. We love our fur friends regardless of these little quirks! Border Collies are just too smart sometimes. We actually had a BC with the big German Shepherd and that could get wild at play time - get out of the way because that 92lb GS traveling full speed was a dangerous missile. It was hard to tell in working with them which one was the "smartest" but by far the BC had the most tricks and play ideas and little sneaky ideas at that - gone over the RB now.


With all the advice given I hope you get those batteries installed soon and go on about life!
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Old 07-11-2019, 05:53 PM   #20
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Red face

The folks on this forum are the best - what a great resource. Thanks again for all the tips, warnings and suggestions!
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Old 07-15-2019, 06:58 PM   #21
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OK, so I did the switchover this past Saturday, with moderate results. I was only able to hook up 4 of the 6 T-105’s. As it turns out, the terminal posts on the batteries are just a bit too short to allow the thickness of three 4/0 cable lugs and get the nut started on the post.

I recall in the thread that someone warned me that this could be an issue. That person was spot on.

I did reduce the number of cables to the battery by wiring positives from the coach to a long post hub that I installed on the wall of the battery compartment, and for the negatives, hung a 500A shunt on the wall (for my next project - a Trimetric monitor). Still, I have one Pos and one Neg connection point that have three cables to them (the two battery interconnects, and the one coming from the wall mounted devices).

After hooking the batteries up, I turned everything back on, and changed the power control for the battery type. The system diagnostics looked good, and the charger went to absorb mode to charge up the new batteries. It was pulling quite a few amps at first, then gradually that decreased until it finally got to the normal float charge mode. Seems to be fine.

So, this week, I am searching for ideas to “make more room on the post”, which will allow jumpering in the remaining 2 batteries. I would like to get this done this weekend, so I have a little time to check how long I can go on battery before charging, and how long it takes to charge up with generator. With 6 batteries, I should have about 660 Ah (330 Ah usable) which I hope will get me the luxury of 12 hrs operation without starting the generator. We are headed to a 4 day music festival, so times for when I charge up are somewhat limited. We can always use coolers/ice as a backup to running the 120V fridge.

So far, ideas I have:

1- a steel bolt extender from hardware store, and a longer 5/16” bolt
2- a fosgate post extension (but they don’t list hole/bolt diam. Online or website)
3- an Odyssey L bracket post adaptor (which I hope is copper), or
4- 1/8” thick x 1” wide copper bar stock, which I would have to drill, cut and bend.

Trojan battery tech support indicated a copper L bracket would do the trick.

Any further thoughts?

John
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Old 07-15-2019, 08:59 PM   #22
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As far as the charging of the batteries with the generator. This is dependent on many variables, so it will be a learning curve. This is what the Trimetric will tell you. I.E. how many amp hours have you used, and how many AH's have you put back in. If you have used 50% of your 660AH (i.e used 330AH) and when the Trimetric is showing you are back to 100% full then you will know how long it took.
Some of this depends on how many amps your charging system puts out.

Keep in mind putting 330AH back into your big battery bank may take 8-10 hours of generator run time. Even putting 200AH back in may take 4 to 6 hours of gen run time.

The charging of your batteries is a much different topic from the original topic about wiring new batteries. Also much more difficult to answer than battery wiring.
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Old 07-16-2019, 10:44 AM   #23
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Al. Glad you are keeping in touch on this. I read an Onan manual that said that with a 100A charger (which my inverter/charger provides), that it will take 4.2 hours to charge up from 60% battery charge to reach float charge stage. If true, the 40% used up to get to 60% charge would be about 264Ahr. The fridge says it draws 6.5A max, and I would say it runs maybe 50% of the time when its hot outside....so in 12 hrs, this should only be 6.5 x 12 x 0.5 = 39Ahr used, leaving plenty for other devices. My hope is that during 12 hrs, the batteries will only discharge to maybe 75-80%, which would decrease the generator charging time.

As for the connection to the battery, I will be using a copper L bracket that I make from bar stock.


Unfortunately, I wont have time to install the Trimetric until after the music festival we are going to next week (still working full time till retirement at end of year). I still haven't researched how to get the wiring from the battery compartment up and into the coach to a convenient location. I like to plan things out before I do them, and then just do them till done.

Thanks for the info.



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Old 07-16-2019, 03:55 PM   #24
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Al. Glad you are keeping in touch on this. I read an Onan manual that said that with a 100A charger (which my inverter/charger provides), that it will take 4.2 hours to charge up from 60% battery charge to reach float charge stage. If true, the 40% used up to get to 60% charge would be about 264Ahr. The fridge says it draws 6.5A max, and I would say it runs maybe 50% of the time when its hot outside....so in 12 hrs, this should only be 6.5 x 12 x 0.5 = 39Ahr used, leaving plenty for other devices. My hope is that during 12 hrs, the batteries will only discharge to maybe 75-80%, which would decrease the generator charging time.

As for the connection to the battery, I will be using a copper L bracket that I make from bar stock.


Unfortunately, I wont have time to install the Trimetric until after the music festival we are going to next week (still working full time till retirement at end of year). I still haven't researched how to get the wiring from the battery compartment up and into the coach to a convenient location. I like to plan things out before I do them, and then just do them till done.

Thanks for the info.



I believe you said you have a residential fridge, so the 6.5amps is at 120V AC. So the 12V amps would be 78 amps at max load.

Chances are the fridge won't be running at max load. Maybe only when the compressor starts will it be at 6.5A AC, then only for a second or two. The compressor running will probably be more like 3-4 amps AC, or 36-48amps at 12V DC.
The exact numbers will show when you have a monitor, or if you have a multi meter that has a "clamp on" probe that reads DC amps so you can check the current at the battery lead.

I believe for your planning purposes, plan on your fridge using 150AH in 24 hours. The AH numbers I have see (w/o any supporting documentation) in forums is a residential fridge draws from about 100AH to about 200AH in 24 hours. The smaller number is for smaller fridges, like 9-10 cu ft and the higher number are for the 20 cu ft or maybe larger.

Note, for your inverter/charger to put out the 100amps you will have to configure it so it knows you have 660AH of battery.
Even then you may not get the full 100A. Also don't plan on having that 100A continuously. Typically a charger will start at say the 100 amps. Within 15-30 minutes it will drop to 95 amps maybe 90 amps and in a couple of hours you will see more like 50 amps or lower. In 3-4 hours it will probably be down to 15-10 amps.

Here is a link which goes into great detail the charging of lead acid batteries. It is pretty technical. The key is to scan all the words until you get down to a caption for 20 minutes, then 1 hour followed by 2 hours. While his charging started out at about 40 amps, in 2 hours it was down to about 7 amps. https://marinehowto.com/how-fast-can...ry-be-charged/
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Old 07-16-2019, 08:44 PM   #25
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Al,
Every time you post that link to the battery charge test I am compelled to click and study it again. That is absolutely the best charging explanation I have seen on the net and he uses the terms I know, BULK, Absorption, Float and Equalize. Like he states, I wish the industry would follow that common terminology.


It can't be overstated but the worst part is it makes me want to spend that cash on those LiFeP04 batteries because it is so very difficult to get mine back to FULL while boondocked. Clearly explains why so many folks wind up replacing batteries every two years and not five. I will be shocked if I get five years on this set of very good batteries but I will try or just give up and go lithium.


Yes the converters and charger/inverters are far better today than 15 years ago but, like the man said, they are really dumb and it takes a lot of work to keep batteries healthy. Work meaning attention to detail, SOC, equalize etc.
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Old 07-17-2019, 09:36 AM   #26
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About Fridge power usage. In May we dry camped and tested a couple of methodologies for preserving battery power. One night, with not a lot of planning or thought I must say, we charged the batteries with our generator up to 99% SOC. Then when we went to bed for the evening I turned off the inverter. This killed the fridge, out internet router and a few phone chargers.

When we woke in the morning the fridge was just as cold as when we went to bed. The temp gauge on the fridge showed 37 in the fridge and 2 in the freezer.

Our SOC that morning was 91%.

Why so low? It was in the low 50's that night and we had our heater set at 63, so it came on during the night.

What I don't know is if the cold night air is what made the "test" so successful or if it was the fridge's insulation and all the cold food and not being opened during the night - keeping all the cold air in.

Perhaps a few days before your trip, when the RV is being set up for the trip, you could get the fridge cold and then turn off the power overnight to see what happens in Summer conditions one night.

Just a thought.

PS. As has been said in this thread. A Battery Monitor Kit is pretty much mandatory for anything more than a day of dry camping. You can't make decisions without it. Unless you can run a generator any time you wish.
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Old 07-18-2019, 09:08 AM   #27
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I can see that on a really cool night in May but our little fridge is not nearly as well insulated as a typical residential unit, just the way it is. I added a little in the rear but could not get extra on the sides etc.


With the dual charging interaction in my components known and workarounds in place I can get back to nearly 95% regardless, if the sun is good I can get into almost 1 amp or sometimes less charge in absorption - not too bad - with good sun. Otherwise the generator is running a lot.


My rebuild of the solar install is off the table until cooler weather, just way too hot outside here to get out and do that work. No doubt I need another panel etc. and wire run corrections and a lot of work to get good solar. The goal is to hear a whole lot less diesel generator run time as you know. I hate taking the little Honda 2000 along but right now for a long stay it is a good bet.


There have been many good suggestions given and advice is taken gladly. I still haven't given up on the 24volt panels but they are usually too big to fit on my roof - still looking.
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Old 07-30-2019, 04:48 PM   #28
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Reporting in - we dry camped for 5 days, trying out the new battery system........and the system worked fine. Had to run the generator every day for several hours, but that was expected. We got 12 - 14 hrs of power, with the batteries reading at 12.2V or above when we started charging (once we were at 12.1V before charging).

Glad I made the changeover - I think it gave us the Ahr. cushion we needed for this trip.

Thanks again for all the help. John
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