2108DS Lithium install: the trip report

[Marine359]

I want to thank Fred2106ds for all his exceptional help, photos and instructions on electrical upgrades posted on the Minnie Winnie thread. We will pretty much be following exactly his install in our new 2108ds.

One important difference though that I need some help on. Our Bigbattery 170ah LiFePo4 comes with Anderson terminal. The Anderson connectors they supply are 36” 6awg Anderson to ring terminal. That seems a bit long and puny to me if the connection is only a foot away. Should I bypass the Anderson and connect to internal battery terminal with 24” 4awg?

Also, should I presume all the dc loads that I need to connect need to be fused. Do I need to fuse them with a fuse block near the battery, or is the fusing in the main power center sufficient? And, the wires which were direct connect, like tongue jack, slide out, and trailer brake, can they be connected to bus bar or do they need to be fused, then to bus bar or battery.

Want to wire battery to a negative shunt Victron battery monitor. Can I wire the negative shunt to a bus bar? Can all the positive load wires be wired to a positive bus bar. This would make it easy to connect and disconnect, or add to dc loads. The battery can be connected to a disconnect or simply turned off.

Sorry if it sounds like I’m a slow learner.
Cheers,

[Elkman]

Current loss with a 36" long 6AWG wire is not significant. If doing it myself I would shorten the wire but only if using solder connectors with solder plugs like the ones sold by delcity.net. The solder connectors are much stronger and provide a better electrical connection than crimp on connectors and no need for a heavy duty crimper, only a propane torch to heat the connector and melt a solder slug inside and then thrusting the bare wires into the connnector.

In general the need to increase wire gauge is with runs (total run of both positive and negative/ground wire) is greater than 10 feet. There is an obsession with keeping line loss under 3% but does it really matter if it takes 60 minutes or 62 minutes to charge the batteries?

[Elkman]

The battery monitor is important to check battery temperature and to not over charge a FLAT type battery and shorten its life. It is not likely to be of any benefit with a sealed lithium phosphate battery bank. More imporatnt to have a charge controller that has a complete lithium phosphate charging profile like the Victron and Xantrex chargers.

[creativepart]

Originally Posted by Marine359

IOne important difference though that I need some help on. Our Bigbattery 170ah LiFePo4 comes with Anderson terminal. The Anderson connectors they supply are 36” 6awg Anderson to ring terminal.

All kinds of options are available here:

https://www.batterycablesusa.com/0-gauge-anderson-cable

[creativepart]

Originally Posted by Elkman

The battery monitor is important to check battery temperature and to not over charge a FLAT type battery.

Still hoping you'll fill us in on what a FLAT type battery is. Is it and FLA or an AGM or something else? You keep posting about FLAT batteries.

[Old Navy]

Originally Posted by Marine359

One important difference though that I need some help on. Our Bigbattery 170ah LiFePo4 comes with Anderson terminal. The Anderson connectors they supply are 36” 6awg Anderson to ring terminal. That seems a bit long and puny to me if the connection is only a foot away. Should I bypass the Anderson and connect to internal battery terminal with 24” 4awg?

6 AWG might be "OK" for charging, but at 100A you are going to see lower voltage at the battery than at the charger, changing the charge profile. You might be able to reduce this effect by decreasing charge current or increasing voltage at the charger. Your 2000W inverter can pull 170A. 3 feet of 6 AWG at 170A would exceed the "3% voltage drop" rule. It could also cause problems with the inverter when surges cause the inverter to draw higher current for a couple seconds, causing the inverter to trip off due to low voltage. the 6 AWG might work for you, but it is marginal. I kinda like the Anderson "Powerpole" connectors and would just buy or make one custom to fit my installation.

Also, should I presume all the dc loads that I need to connect need to be fused. Do I need to fuse them with a fuse block near the battery, or is the fusing in the main power center sufficient? And, the wires which were direct connect, like tongue jack, slide out, and trailer brake, can they be connected to bus bar or do they need to be fused, then to bus bar or battery.

Yes, you should fuse all loads near the battery. The load center is a single load, and only needs one fuse. The inverter/charger needs it's own fuse. Bus bars are good.

Want to wire battery to a negative shunt Victron battery monitor. Can I wire the negative shunt to a bus bar? Can all the positive load wires be wired to a positive bus bar. This would make it easy to connect and disconnect, or add to dc loads. The battery can be connected to a disconnect or simply turned off.

Yes, you can wire all of your loads to bus bars. The negative bus bar would be on the LOAD side of the shunt, and you have to ensure all negative wires are attached to the LOAD side of the shunt, and only the battery negative to the BATTERY side.

See in BLUE above.

[Old Navy]

Originally Posted by creativepart

Still hoping you'll fill us in on what a FLAT type battery is. Is it and FLA or an AGM or something else? You keep posting about FLAT batteries.

The battery in my phone is flat.

[Marine359]

Thanks Old Navy for making it easier for me to understand. If I add so,ar later, I could just wire the charge controller, properly fused to the bus bar. Easy peasy.

[Elkman]

Old Navy - you are making a great many assumptions to arrive at your conclusion. The Xantrex 2000 inverter charger will provide "up to 100 amps" but that assumes that the battery can accept that rate of charge. There is always going to be a lower voltage state at the battery than at the charger.

When there is a 15 foot or longer run from a charger to the battery bank the gauge wire is important and for a run of greater length that will carry 30 amps going to 4 gauge may be adviseable. But for a 12 inch section of #6 wire any loss is negligble and the connectors have a far greater role in resistance to current flow.

The custom is to crimp connectors and that does not provide the best connections but it is a quick and dirty approach and there are far better alternatives that do not even require a special tool for a one time project.

[Marine359]

Thanks Elkman,
Our LiFePo4 can accept 75 amp @ 14.4v. So we went with a 60amp progressive dynamics charger converter. I’m thinking the battery will love it.

[Marine359]

Elkman,
Thanks to your input and from others,
We are going with 4awg marine grade for batt and inverter with connections less than 24”. Converter charger to be co-located In pass through with battery and inverter. Short run. 4awg. Batt to bus 4awg Anderson to ring terminal. Inverter 4awg ring terminal to bus bar. Better to be safe than sorry I guess.

[al1florida]

Do NOT depend on someone on the internet telling you to not worry about wire size for what ever reason or logic!

DO use a voltage drop calculator to provide you with the exact voltage drop to expect for the wire size you have, the length of the wire and the number of amps that will be going down the wire.

Here is an excellent voltage drop calculator: https://www.calculator.net/voltage-drop-calculator.html

[al1florida]

I would not and I have not set up my systems by installing wiring that has a 3% voltage drop.

If you are setting your charger to provide 14.6 volts to charge your battery and you have a 3% voltage drop you are only getting 14.162 volts at your battery. That means you will not be charging your battery as quickly or as fully as you would if you had a 1% voltage drop.

The cost of buying the larger wire is insignificant compared to the overall cost of installing your system. Additionally the extra cost of the larger wire is not that great for the few feet of wire you need.

I don't call that obsessing, I call that planning for the best efficiency in setting my system up.

Too small of wire size and too long of wire runs is one reason that many people are dissatisfied with their systems and a large contributor to why people have to run their generators.

USE the voltage drop calculator to determine the wire size you want to use and then compare the difference in cost when you go to buy the wire.

[al1florida]

Originally Posted by Elkman

Old Navy - you are making a great many assumptions to arrive at your conclusion. The Xantrex 2000 inverter charger will provide "up to 100 amps" but that assumes that the battery can accept that rate of charge. There is always going to be a lower voltage state at the battery than at the charger.

However the inverter can pull up to 170amps. The microwave will pull about 140amps from the batteries through the inverter. A coffee pot or 2 slice toaster will pull about 100amps.

Be sure to size your wires for the 170amps.

[Old Navy]

Originally Posted by Elkman

Old Navy - you are making a great many assumptions to arrive at your conclusion. The Xantrex 2000 inverter charger will provide "up to 100 amps" but that assumes that the battery can accept that rate of charge. There is always going to be a lower voltage state at the battery than at the charger.

You should always follow best practices and/or code laid out in the NEC/NFPA rather than cut corners. XANTREX recommends "less than 5 feet of 2/0 AWG", based on NEC table 310.17. This cable size isn't due to the maximum charging current, but the maximum current the XANTREX can draw from the battery when inverting. That's 170A continuous and more during short surges.

I'm not an Electrician, but I am a retired Electronics Tech, so I understand electricity and electronics a bit better than most. But I'll repeat, I'm not an Electrician. I don't know the NEC and NFPA by heart, but I know enough to look things up and ask questions.

[thataway4]

I'll "second" what "Old Navy" said. I posted earlier that I use OO cable for a very short run with 200 amp hours of LiFePO4 battery and a Victron Multiplus 2000/80 inverter charger. The cable is sized for the max current which will be drawn. You want as little voltage drop as possible. You are paying a premium using Li batteries and good chargers, thus you need to do every thing possible to maximize the results.

In marine applications the battery cable should be fused within 7". Solder vs crimp is often debated. In boats the technical agency (ABYC) specifies crimp connection and tinned AWG wire. I believe that crimp is preferred for any terminals in aircraft. A connection directly to a device is often soldered. I have a lot of experience soldering as a ham operator and electronic experimenter of many years. I crimp where it is best practice.

The reason for crimp is there is less chance of breaking due to fatigue due to vibration for a crimp connection. There is a lot of vibration in a trailer or motorized RV going down the road. Having said that there are proper crimpers, and the average person probably does not own them. I have an adjustable ratchet crimper for 10 thru 22 wire size, and specific dies for 4/0 thru #8 wire. In the long run it pays to do the job properly.

Also all of the crimp connections should be high quality terminals, and I like to either have heat shrink as part of the terminal, plus put quality heat shrink tubing over the connection to give it more support. Also all positive terminals should be covered to prevent shorts. I would not use a bus bar for the positive if more than a couple of wires/systems off the fuse block, but instead use one of the protected fuse blocks in 4 to 12 slot ATC blade fuses as made by "Blue Seas". You fuse to protect the wire from overheating--this should be done as close to it's origin as possible.

[Marine359]

Thank you all for your input. I know that bigger and shorter is better when it comes to dc wiring, which is why I suspected the wire from Bigbattery is a bad choice. However, I really like the idea of using the Anderson terminal on the battery. This enable easy disconnection of the battery from the entire system for removal. Since there is only one set of wire from the battery the Question becomes what do you connect to. Negative should go to shunt, but where to put positive ring connector? Seems to me bus bar gives the convenience of attaching charger, fused and switched dc loads, and unstitched dc like tongue jack, breakaway switch and slide out. If you don’t use a bus bar, all those wires have to go direct to internal battery terminal bypassing the Anderson terminal.

I’m not an electrician either, but I did lots of lab work in college for EE courses, and weapons courses. We always wired to bus bars in the lab. Makes it easy to disconnect so other students could then rig their projects.

Since this install is in the pass through compartment, all components can be located within 2ft of battery. So wires connected to bus bar all have soldered 3/8” ring connectors, there should be no risk of short across terminals, especially if using a quality covered bus bar. 00 gauge can be hard to work with when maybe 2ft 2awg will get the job done.

Chime in if I’m on the wrong track here, and thanks Thataway4 for the recommendation on Blue Seas blade fuse block.

[Marine359]

Excuse me Thataway4, you are correct about crimp v solder. I should us crimp.

[al1florida]

Originally Posted by Marine359

Thank you all for your input. I know that bigger and shorter is better when it comes to dc wiring, which is why I suspected the wire from Bigbattery is a bad choice. However, I really like the idea of using the Anderson terminal on the battery. This enable easy disconnection of the battery from the entire system for removal. Since there is only one set of wire from the battery the Question becomes what do you connect to. Negative should go to shunt, but where to put positive ring connector? Seems to me bus bar gives the convenience of attaching charger, fused and switched dc loads, and unstitched dc like tongue jack, breakaway switch and slide out. If you don’t use a bus bar, all those wires have to go direct to internal battery terminal bypassing the Anderson terminal.

I’m not an electrician either, but I did lots of lab work in college for EE courses, and weapons courses. We always wired to bus bars in the lab. Makes it easy to disconnect so other students could then rig their projects.

Since this install is in the pass through compartment, all components can be located within 2ft of battery. So wires connected to bus bar all have soldered 3/8” ring connectors, there should be no risk of short across terminals, especially if using a quality covered bus bar. 00 gauge can be hard to work with when maybe 2ft 2awg will get the job done.

Chime in if I’m on the wrong track here, and thanks Thataway4 for the recommendation on Blue Seas blade fuse block.

I believe you are on the right track. Going to a busbar with the positive lead from the battery is the right way to go.

For cable size I would use the Voltage Drop Calculator to verify the voltage loss with various wire sizes. It may take 2.5 to 4 feet of cable to go the 2 feet between components so don't just put 2' into the calculator. Note that the calculator in the link I gave automatically calculates the round trip distance, so you just enter the length of the cable from the component to the battery.

I would shorten the cable you now have for the battery either by cutting and splicing or just cutting and adding a new ring terminal. UNLESS the calculator shows the voltage loss is acceptable to you and the 36" cable will reach where you need it to go. 36 inches of #6 wire seems awfully small to go to a 2000 watt inverter.

[Old Navy]

I also like the Anderson connectors and used them when I installed a charger in my boat. Terminals are cheap, so you can always just buy some new terminals to install the exact gauge and length of wire you want. Or a new connector for about $15.

https://powerwerx.com/anderson-sb175...-piece-contact

You are definitely on the right path with bus bars. Many people have documented their projects online, and you can get lots of ideas for your own. I would recommend you get a piece of plywood the same dimension as your installation area. Then you can do the entire layout, cut and form the wires, and verify the system on your workbench rather than stuffed into your pass through storage. Remember to reserve space for future components like a solar controller. Below is a pic of a pretty simple and neat installation with bus bars and switches. Note that this person not only built their system on a piece of plywood, but left it on that plywood. It also shows how they wired the shunt between the battery and the neg bus bar.