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Old 02-13-2020, 04:08 PM   #11
Kajtek1
 
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Default Re: Adding inverter and lithium to 2015 ERA 170x

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Originally Posted by marklg View Post
Both batteries should be close together and no way #2 and #4 will work well between them. You will get large and different voltages drops such they will not charge or discharge the same, likely resulting in one wearing out before the other. ...
That would matter if you use your batteries for welding, but it is a myth for RV application.
Voltage drop in RV is not a problem and as long as inverter will not go into low voltage shut-down, it will work for most of application.
Years ago I kept my travel trailer in dry storage close to the lake. Since I had no way to charge the battery, I put old motorcycle battery in the trailer box for brakes when towing 1 mile to the storage and was taking big battery home for recharging.
Than when set for camping, I put big battery on ground and connected with small battery in the camper with #16 wires. Worked as a charm for 3 seasons.
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Old 02-13-2020, 04:51 PM   #12
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Default Re: Adding inverter and lithium to 2015 ERA 170x

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Originally Posted by Kajtek1 View Post
That would matter if you use your batteries for welding, but it is a myth for RV application.
Voltage drop in RV is not a problem and as long as inverter will not go into low voltage shut-down, it will work for most of application.
Years ago I kept my travel trailer in dry storage close to the lake. Since I had no way to charge the battery, I put old motorcycle battery in the trailer box for brakes when towing 1 mile to the storage and was taking big battery home for recharging.
Than when set for camping, I put big battery on ground and connected with small battery in the camper with #16 wires. Worked as a charm for 3 seasons.
Please read the links about unbalanced charging of parallel identical batteries. You charged a large battery with much lower internal resistance that probably made up for the wires. Did you check the state of charge of the various batteries to make sure they all were fully charged?

I still have to respectfully disagree when there are identical several hundred dollar batteries that you want to last. I threw away four bad AGM batteries that probably cost $1000 after only a few years. None would hold much of a charge.

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Old 02-13-2020, 04:53 PM   #13
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Default Re: Adding inverter and lithium to 2015 ERA 170x

It's your choice to drop high dollar on batteries.
When I had big conversion, I bought 4 golf cart batteries @ $46 a piece. Lasted me 12 years - badly neglected by your standart in dry storage without seeing a charger for 8-12 months.
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Old 02-13-2020, 05:49 PM   #14
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Default Re: Adding inverter and lithium to 2015 ERA 170x

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yea those wires are killing you. Wiring is fun. Buy a good hydraulic crimper and dive in! Add some wiring distances to your diagram on the key runs to help get better comments.

Heat with fossil fuels to make coffee as Orion suggests. So practical.

There are smaller microwaves that might do better on battery but maybe you do not want to mess with that.

Seems like this rig was only every envisioned to run appliances off shore power thus the silly wire sizes.

HarryN had a lot of great comments but I think the 2 Battleborns would drive the 2000W inverter.
If the load is 1250 watts for the coffee maker or even an occassional 1500 watts for the microwave then yes that will work with 2 batteries.

Where it gets tricky is an 1800 watt blow dryer or two loads.

2000 watts + 10% losses ~ 2200 watts

2200 watts / 12 volts = 183 amps, so ~ 90 amps from each BB if they are perfectly balanced.

Since I have a customer that blew out the 100 amp rated BMS on 3 parallel connected BBs, all pulling less than the spec, I tend to be a bit more conservative in my recommendations.

They are nice batteries and BB took care of the customer. I use them for some applications and have no complaints - but I also use them at 500 watts / battery, not 1000.
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Old 02-13-2020, 06:52 PM   #15
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Default Re: Adding inverter and lithium to 2015 ERA 170x

Spreading 4 batteries around like that is going to make balancing loads very difficult. If your loads/sources are less than 0.15C, then it doesn't matter as much, but with higher C rates, the load imbalance will inevitably cause one or more batteries to reach the cut-out long before the others. This can cause a sudden load increase on the remaining batteries. Depending on the load split, and wiring resistance, you can have a cascade where all the batteries over current and drop out for a short period. This of course depends on the load size, and small loads will not cause this issue.

Same goes for charging, depending on how your charger is configured you may end up with partial charge drift on a few. This is less of a problem with lithium packs, as they don't suffer from partial charge degradation like lead.

6AWG is too small for the rated output of the inverter. A startup surge (easily 1.5x the inverters continuous output) will easily drop the voltage below the cut out threshold.

I also strongly suggest a decent shunt based battery meter. This would require use of a common ground somewhere, through which all loads/sources pass through a single point.

Note that you don't have to use a single large cable. Multiple 6,4,2 AWG cables can be used to the same effect, and they are easier to run. When using multiples, it is sometimes easier to combine them into a single larger terminal lug at the termination.


With 2 parallel batteries like the ones on the right side of the diagram, they can be balanced by having the positive/negative parallel runs be the same gauge and length, and having the negative take-off on one battery, and the positive on the other.
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Old 02-21-2020, 02:04 AM   #16
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Default Re: Adding inverter and lithium to 2015 ERA 170x

I got an email from Battleborn. They essentially said use larger and shorter wires. I think we all knew that part already. Very disappointing! They never answered the real question. I was hoping for some way to connect the batteries and maintain the chassis charging. I will investigate moving the lithium batteries under the bed in the back and installing something like a DC-DC charger from chassis to coach. After studying inverter chargers for a while now I think I’m going to get an Aims PICOGLF20W12V120V. I settled on this one because it should fit in the space under the seat with the rest of the electrical equipment. I will get ERA out of storage in a week or so if the snow melts. Hope to start working on electrical and other mods then.
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