Charging lithium batteries from our tv

[TouringDan]

The preferred method of charging lithium batteries from the TV seems to be installing a dc to dc battery charger. I considered this option and ordered a Renogy 40 amp dc charger. After it came I read the directions and it recommended installing #4 wire from the charger to the two lithium batteries at the back of our Tradewind about 40 ft away. I decided I didn’t want to do this and returned the charger.

I had a Zamp 1,000 watt pure sine inverter leftover after I replaced it with a Samlex 2,000 watt inverter in our Tradewind. Here is a photo of the lithium batteries and the inverter currently installed in our Tradewind.

I decided to install the Zamp inverter in my Tundra. There was plenty of room for it on top of the fuse box cover right next to the battery. I installed the remote switch for the inverter next to my brake controller. Here are photos of the inverter and the remote switch.

I plugged a 16/3 extension cord in (rated for 13 amps) and ran it underneath the truck to the 15 amp connector I installed at the front of the Airstream. Here are photos.

The 15 amp connector is wired using 14/2 wire to a switch, to isolate the connector, then to the Progressive Dynamics 45 amp lithium battery converter. There is only a very small chase running from front to back of the Tradewind to run utilities. It contains a 1/2” Pex line, two #10 wires for solar, the antenna wire and the #14 wire. Here are photos.

This seems like a much better solution for me for charging our lithium batteries than a dc to dc charger would be. Am I missing something?

Dan

[TouringDan]

One of the advantages of charging with an inverter is that I know the correct charging profile from the Progressive Dynamics converter for the lithium batteries is being used.

Another advantage is that I am able to split off the extension cord running under the truck and provide power to the battery charger for keeping my 35 Ah lithium battery charged that powers the compressor fridge that we carry in the back of the Tundra. It has a different charging profile than the BB batteries in the Airstream. The bulk charge is 16.8v with a float charge of 16.6v. Here is a photo of the battery and charger in the bed of the Tundra.

Dan

[AdvToaster]

If you’re plugged into shore power and that switch is flipped on are those prongs hot?

Also, I’d keep an eye on that extension cord in the engine bay. Those cords are definitely not rated for the 200+ degrees that you can find in there. The heat may kill your inverter pretty quickly as well.

[TouringDan]

Originally Posted by AdvToaster

If you’re plugged into shore power and that switch is flipped on are those prongs hot?

Also, I’d keep an eye on that extension cord in the engine bay. Those cords are definitely not rated for the 200+ degrees that you can find in there. The heat may kill your inverter pretty quickly as well.

AdvaToaster- Thank you for your comments. I agree with your concerns.

You are correct. The shore power connection at the rear is similar to the connection at the front that goes to the converter. If shore power is connected at the rear, the switch would need to be off. My plan is to always have the switch off unless I am charging the batteries from the TV. Similarly, the prongs in the shore power connector at the rear will be hot while I am charging the batteries from the TV. The circuit breaker to the converter will need to be turned off to make sure the prongs are not hot.

The extension cord (exterior grade) and the inverter may not last due to high temperatures. The only good way to find out is to operate it as planned and see what happens. It may be a good idea to keep the inverter turned off when in city traffic or at other times when high temperatures are a concern.

Dan

[AdvToaster]

Sounds like you’ve thought it through! Good luck, I hope it turns out the heat isn’t an issue!

[drbrick]

I live simple ... pulled the fuse in the TV and maintain the lithium charge via our solar panels - did the same with our AGMs and 6v golfcarts, never had a problem

[uncle_bob]

Hi

The "charge wire" on your 7 pin connector is likely fused at something in the 20 to 30A range. If you get 10V at the trailer from your wiring and put 14 V into the batteries (not all that unusual), the current into the DC/DC will be at least 1.5X the current out.

If your "40A" converter is 40A on the output, that means 60A into the device. You have a device that is pretty much guaranteed to blow whatever fuse is on the charge wire.

Getting anything over 10A through the charge wire is iffy. Indeed, you may simply disconnect before the fuse blows. Simple answer is that you want a DC/DC that puts out a max of 10 to 15A (with less being better ....).

Bob

[TouringDan]

Originally Posted by drbrick

I live simple ... pulled the fuse in the TV and maintain the lithium charge via our solar panels - did the same with our AGMs and 6v golfcarts, never had a problem

drbrick- Thanks. We strive to live simple too, but sometimes the 400 watts solar on the bed cap doesn’t work to well when carrying kayaks or camping in the shade. Also we no longer carry a separate generator. Just trying to make sure we can always have a way to keep our batteries charged since we generally camp without hookups.

Dan

[Wazbro]

It would be a good idea to wire in a switch so that in one position your converter is connected to shore power and in the other position it is connected to front plug. This would prevent hot prongs.

Also disconnect charge wire in umbilical if you haven't.

[TouringDan]

Originally Posted by uncle_bob

Hi

The "charge wire" on your 7 pin connector is likely fused at something in the 20 to 30A range. If you get 10V at the trailer from your wiring and put 14 V into the batteries (not all that unusual), the current into the DC/DC will be at least 1.5X the current out.

If your "40A" converter is 40A on the output, that means 60A into the device. You have a device that is pretty much guaranteed to blow whatever fuse is on the charge wire.

Getting anything over 10A through the charge wire is iffy. Indeed, you may simply disconnect before the fuse blows. Simple answer is that you want a DC/DC that puts out a max of 10 to 15A (with less being better ....).

Bob

Bob- I don’t understand your comment. I am not using the charge wire. I am charging the batteries using 120v from the inverter in the TV to the Airstream converter.

Dan

[TouringDan]

Originally Posted by Wazbro

It would be a good idea to wire in a switch so that in one position your converter is connected to shore power and in the other position it is connected to front plug. This would prevent hot prongs.

Also disconnect charge wire in umbilical if you haven't.

Wazbro- Thanks for your comments.

I have already disconnected the charge wire in the umbilical.

I already have a 3 way switch to select between power for the electrical panel from the rear connector for shore power (the switch is down) or from the 2,000 watt Samlex inverter (the switch is up).

When I am charging the batteries from the TV the front switch will need to be turned on to send power to the converter and I will turn off both of the circuit breakers so that only the converter has power.

Dan

[uncle_bob]

Originally Posted by TouringDan

Bob- I don’t understand your comment. I am not using the charge wire. I am charging the batteries using 120v from the inverter in the TV to the Airstream converter.

Dan

Hi

When you started this out, you had a 40A dc/dc involved. That's *way* to big. There is no practical way to use that device with stock wiring.

========

Doing the truck -> inverter -> converter -> battery thing is *very* inefficient. You loose at the inverter, and at the converter.....

Bob

[Gulliver72]

Seems like overkill to me. I run #2 fused wire from TV battery to back of TV with Anderson plug at back end. #2 wire at front end of trailer to 40A dc/dc charger. When the sun is shining I’ve got 65+A coming in, 40 when it’s not. Sysytem works great.

[TouringDan]

Originally Posted by uncle_bob

Hi



When you started this out, you had a 40A dc/dc involved. That's *way* to big. There is no practical way to use that device with stock wiring.



========



Doing the truck -> inverter -> converter -> battery thing is *very* inefficient. You loose at the inverter, and at the converter.....



Bob

Bob- Good point, I agree that you lose efficiency due to the losses in the TV inverter and the Airstream converter. However, I am not sure how much that matters as long as I am charging the lithium batteries correctly as I am driving down the road.

Dan

[TouringDan]

Originally Posted by Gulliver72

Seems like overkill to me. I run #2 fused wire from TV battery to back of TV with Anderson plug at back end. #2 wire at front end of trailer to 40A dc/dc charger. When the sun is shining I’ve got 65+A coming in, 40 when it’s not. Sysytem works great.

Gulliver72- Thanks for your comment. Glad that the 40A dc/dc charger works for you. My situation is a bit different though. My lithium batteries are 40 ft away, not 20 ft and I need to charge a second lithium battery in the bed of my truck with a different charging profile than the lithium batteries in the Airstream.

Dan

[TouringDan]

The 1,000 watt Zamp inverter I have installed is left over from my original power plant for our 66 Tradewind consisting of two golfcart batteries and the inverter.

When I installed the lithium batteries I installed a larger 2,000 watt Samlex inverter. This allows us to operate the microwave or any other appliance that plugs into a standard receptacle. When we installed the lithium batteries we needed to install a new converter. At the time we were using a Honda 1,000 watt generator in the event that the solar was not adequate for keeping the batteries charged. We could only go with the 45 amp Progressive Dynamics converter because the 60 amp model required 1,025 watts to operate. The Zamp inverter does fine because it only requires 725 watts to operate.

CarGenerater markets a 1,000 watt inverter that you can connect to your TV battery for $460.

I noticed that this inverter seems to be identical to the Zamp inverter. The Zamp inverter on Amazon costs $332. I looked at other pure sine inverters on Amazon and stumbled across the Giandel 1,200 watt model for $200.

The aluminum case looks like the Zamp case and has the same dimensions. I believe that Giandel, a large worldwide manufacturer of inverters, makes the inverters for Zamp and CarGenerator.

If I knew then what I know, I would have installed a Progressive Dynamics 60 amp converter in our Airstream and a Giandel 1,200 watt inverter in my Tundra. This combination would charge the batteries faster and also will actually operate a small microwave. I have a 700 watt microwave. The specifications list an input of 1,050. I have measured the actual input at 1,060 watts.

The specifications show a high temperature cutoff at about 150 F. I suspect this may be exceeded in hot weather while idling in traffic but it should be fine when not stuck in traffic. I just hope the hot weather doesn’t damage the inverter. That is my only real concern in this installation. I like not having to carry my Honda generator and fuel in the bed of the truck. We shall see.

Dan

[coloradoup]

Dan,
Do you still have the stock alternator in your TV? I have heard that if you are charging LI batteries you need a larger alternator do to the amount of amps your LI batteries will take. Maybe just a sales pitch to get you to buy a bigger alternator but it worked on me.

[waninae39]

the 7 pin cable does not allow a high charge from TV to AS.

the 7 pin cable is the weakest link in the chain.

even if you upgrade the alternator, the 7 pin is still the limiting factor

some people add another cable just for the charge

[TouringDan]

Originally Posted by coloradoup

Dan,

Do you still have the stock alternator in your TV? I have heard that if you are charging LI batteries you need a larger alternator do to the amount of amps your LI batteries will take. Maybe just a sales pitch to get you to buy a bigger alternator but it worked on me.

Coloradoup- My Tundra has the tow package, so I believe the alternator capacity is 150 amps. The maximum amp draw is about 60 amps (for 725 watts power consumption) so I don’t believe that I will have a problem. If ever I notice that the inverter is using too much power I will just turn it off. Thanks for asking the question.

Dan

[TouringDan]

Originally Posted by waninae39

the 7 pin cable does not allow a high charge from TV to AS.

the 7 pin cable is the weakest link in the chain.

even if you upgrade the alternator, the 7 pin is still the limiting factor

some people add another cable just for the charge

waninae39-I am not using the 7 pin charging cable (12v). I am charging the Airstream lithium batteries by running 120v from the output of the inverter to the AS converter.

Dan