Lithium battery charge ?

[2link2]

Probably been beaten to death but doing a google & forum search & being ignorant on lithium battery charging I'm at a loss. I thought it was very simple question than I read (google) enough to get concerned if my system is OK. We bought the trailer used with what I think is a really decent Lithium/solar package. My question started out with "how fast will my TV 7 pin connector charge 2 Battle Born batteries". I never found an answer to my question, just more about problems that can happen with a TV charging lithium batteries. With my listed components below can anyone tell me if I need to add anything or if my TV can/will charge the batteries.

2 Zamp Obsidian 90 watt solar panels
2 Battle Born 100 AH heated lithium batteries
1 Victron MPPT 100/30 solar charge controller
1 Victron BMV 712 battery monitor
1 Victron BP -12/24 100 battery protector
1 Victron smart battery sense temperature monitor
1 Progressive Industries EMS-HW30C hard wired surge protector with remote
1 A.C. voltage and amperage display
Thanks !

[richard5933]

You also need to provide some idea of your electrical load on the batteries...Are you running a 12vdc fridge? Boondocking and running the furnace? Are you going from pedestal to pedestal? Etc, etc.

On a sunny day your solar panels will go a long way towards helping keep your batteries charged, but with only 180 watts they won't keep up if you are running an all-electric 12vdc fridge and hoping to get your batteries charged while underway.

You can get a minimal charge from your TV using the 7-wire connection. It won't fully charge them, and it will only give a minimal charge. You also stand a chance of having the tow vehicle drain the trailer's batteries if you leave things connected after turning off the TV.

An option is to add a DC-to-DC charger to the mix. There are lots of threads on that so I won't add to much about it here unless you have specific questions.

[field & stream]

In my opinion you should add a dc/dc converter, and in my experience (without rewiring from the tv alternator) you should not expect significant recharging.

Two bits of information will help us hep you:
— what make and model converter do you have
— what voltage does your 712 show under various circumstances

[JeffKim]

As stated above, there are lots of threads on DC-DC chargers. The salient points are:

1. You will get charging from the 7-pin charging wire but it does not provide a lithium charging profile that a DC-DC charger will. This is important if you want to top off, balance, and do the right thing for your expensive BB batteries.
2. With the raw wire charging, the MPPT solar charger while on the road can be confused by whatever voltage is applied via the charging wire and not perform as it should.
3. The Victron Smart 18A DC-DC charger is what most people use connected to the charging wire. Roughly speaking it's about 18A*12V = 216W of charging rain or shine. I don't consider this trivial especially if it's a long travel day. In six hours or so that's enough charge for one 100Ah battery. You can go with a bigger charger but as stated above, you will need to wire directly to your TV system.

[Wazbro]

Depending on your TV your TV may actually drain your trailer batteries while driving down the road. A Ford power boost for example only has 12.5 volts in the "12 volt" system unless some certain settings are done, this would then draw power from your higher voltage lithium batteries. This is why many recommend a DC to DC charger or disconnecting the 12 volt charge line.

[2link2]

Much thanks top all the posts, good info. !

It looks like I need the DC-DC charger installed.

From the paperwork & manuals that came with trailer these are what I have

inteli-power 9200 converter
Parallax SR series converter

Parallax RU upgrade ? (it says "it can deliver it's entire DC output toward battery charging)

Parallax 4400LBU Lithium battery charging module
I haven't paid much attention to the 712 display I think it was showing 13.6V on the battery's before I disconnected them for winter storage. I just connected the battery's and drove a few miles to DMV and when I got there the Victron app showed battery's at 100% charge. I believe the solar must have done that charging.
As far as load goes it's pretty minimal for us. We have propane/elec fridge, propane/elec. water heater. Travel only spring-fall & rarely use the furnace. Pretty much just running lights, TV a few hours at night. No microwave.

We just bought the trailer a 2017 25' FC in February towed it home, winterized it. Now were getting ready for some traveling. And as you can tell I know very little on how the system works.
Thanks again

[field & stream]

2link2 — thanks for the additional information. Based on that, and the addition of a dc/dc converter, I would say you have a very good system. The 13.6 volt reading is what fully charged lithium batteries will show at rest, so it looks like it is working properly.

Even with your low power usage you will need reasonably good solar conditions to last for extended periods (more than several days). Cloudy and/or shady conditions can cost you 90% of potential output. Portable panels can add when necessary, and chase the sun around wooded campsites.

I suggest you spend some time with your 712 turning devices on and off one at a time. From that you can learn what the power demands of each are, and then better manage your consumption during shady conditions.

[3OnOurWay]

Originally Posted by field & stream

In my opinion you should add a dc/dc converter, and in my experience (without rewiring from the tv alternator) you should not expect significant recharging.

Two bits of information will help us hep you:
— what make and model converter do you have
— what voltage does your 712 show under various circumstances

For us BT solar controller and BT shunt were valuable to determine / table the guess work out of our driveway trial usage and then on our shorter test trips to have confidence. Now tracking each item, I know what parasitic draw is for our rig, under 1 amp no fridge running and so can make sure no one ( mainly me) left something on ( propane switch , bathroom fan, inverter, digital satellite power)
Good luck and driveway tests will show your basic minimum 24hr draw numbers. We average minimum of 20% 40 amp on a 200 amp system with some solar in driveway. Solar parked at campsite full sun will give us back 7-10%

[2link2]

K.I.S.S. applies to me for sure ! I kind of read into (mis-read) a few posts here & combined with the google search I thought I would need a DC-DC charger to keep from draining the batteries. I called Battle Born this morning to discuss buying a Victron DC-DC charger. BB told me there is no way the batteries can drain while driving using a 7 pin connection. The only possible way batteries can drain is when TV is not running and the higher BB voltage can back feed the TV battery. As the resting voltage of my truck battery is 12.6V running it's 14.8V. He also told me don't expect any real charge from the 7 pin as it's only going to be 3-5 amps. Also said having or not having a DC-DC charger has no affect on how the Victron charge controller functions or improve battery life. But having one adds a reliable way to charge your batteries while driving. I got an answer to my original question & gained some knowledge on my solar set up. Were going to carry on without adding a DC-DC charger at this point & see how it goes.

Thanks again everyone.

[kmayer]

Originally Posted by 2link2

K.I.S.S. applies to me for sure ! I kind of read into (mis-read) a few posts here & combined with the google search I thought I would need a DC-DC charger to keep from draining the batteries. I called Battle Born this morning to discuss buying a Victron DC-DC charger. BB told me there is no way the batteries can drain while driving using a 7 pin connection. The only possible way batteries can drain is when TV is not running and the higher BB voltage can back feed the TV battery. As the resting voltage of my truck battery is 12.6V running it's 14.8V. He also told me don't expect any real charge from the 7 pin as it's only going to be 3-5 amps. Also said having or not having a DC-DC charger has no affect on how the Victron charge controller functions or improve battery life. But having one adds a reliable way to charge your batteries while driving. I got an answer to my original question & gained some knowledge on my solar set up. Were going to carry on without adding a DC-DC charger at this point & see how it goes.

Thanks again everyone.

Sounds like a wise way to move forward. Keeps us posted regarding how things work for you.

[field & stream]

Originally Posted by 2link2

K.I.S.S. applies to me for sure ! I kind of read into (mis-read) a few posts here & combined with the google search I thought I would need a DC-DC charger to keep from draining the batteries. I called Battle Born this morning to discuss buying a Victron DC-DC charger. BB told me there is no way the batteries can drain while driving using a 7 pin connection. The only possible way batteries can drain is when TV is not running and the higher BB voltage can back feed the TV battery. As the resting voltage of my truck battery is 12.6V running it's 14.8V. He also told me don't expect any real charge from the 7 pin as it's only going to be 3-5 amps. Also said having or not having a DC-DC charger has no affect on how the Victron charge controller functions or improve battery life. But having one adds a reliable way to charge your batteries while driving. I got an answer to my original question & gained some knowledge on my solar set up. Were going to carry on without adding a DC-DC charger at this point & see how it goes.

Thanks again everyone.

Hmmm…. True there will be no back feed while running, but there can/will be back feed while engine off and 7pin still connected — like stops for meals, shopping, sightseeing, etc. Why not eliminate that? And as BB said it is a reliable way to pick up a few Ah, so why not?

Another feature is that it converts the alternator output voltage to the higher voltage required by the lithium profile. You imply that the output of your truck alternator is 14.8v, and it may be, but my alternator output voltage is 13.9 and it will not charge my lithium above 60% without the dc/dc converter. I suggest you check the actual output voltage of your alternator.

In my mind, it is a reliable way to pick up some Ah and reduce some slight risk.

[3OnOurWay]

Originally Posted by 2link2

K.I.S.S. applies to me for sure ! I kind of read into (mis-read) a few posts here & combined with the google search I thought I would need a DC-DC charger to keep from draining the batteries. I called Battle Born this morning to discuss buying a Victron DC-DC charger. BB told me there is no way the batteries can drain while driving using a 7 pin connection. The only possible way batteries can drain is when TV is not running and the higher BB voltage can back feed the TV battery. As the resting voltage of my truck battery is 12.6V running it's 14.8V. He also told me don't expect any real charge from the 7 pin as it's only going to be 3-5 amps. Also said having or not having a DC-DC charger has no affect on how the Victron charge controller functions or improve battery life. But having one adds a reliable way to charge your batteries while driving. I got an answer to my original question & gained some knowledge on my solar set up. Were going to carry on without adding a DC-DC charger at this point & see how it goes.

Thanks again everyone.

You bring up valid points and everyone’s use is so individual across the trailer and class B segment.

I think it would be very helpful to know what your 24hr usage is ?
2. whether you plan to Boondock / use any site available or be plugged in at mostly @ campsites.
3. Ans/or what your generator ideas are for usage to provide you with power

I forget the size your system, but 200 aH for us is not a lot for trips longer than three days Boondocking.

Having a strong understanding of your individual trailer usage will help you make decisions on this for us were in a class B and so we cheat all the time with the DCC charger to dump in another 30 A/h when moving from one location to another over our short time period that we have been doing this.
As you’ve read on some of the posts, easy way to not backfeed is to disconnect anyways, and as you’ve read on post here, some run direct power cable down the bed of the truck to a DC DDC controller. All good ideas for individual preferences and usage.

[2link2]

Originally Posted by 3OnOurWay

You bring up valid points and everyone’s use is so individual across the trailer and class B segment.

I think it would be very helpful to know what your 24hr usage is ?
2. whether you plan to Boondock / use any site available or be plugged in at mostly @ campsites.
3. Ans/or what your generator ideas are for usage to provide you with power

I forget the size your system, but 200 aH for us is not a lot for trips longer than three days Boondocking.

Having a strong understanding of your individual trailer usage will help you make decisions on this for us were in a class B and so we cheat all the time with the DCC charger to dump in another 30 A/h when moving from one location to another over our short time period that we have been doing this.
As you’ve read on some of the posts, easy way to not backfeed is to disconnect anyways, and as you’ve read on post here, some run direct power cable down the bed of the truck to a DC DDC controller. All good ideas for individual preferences and usage.

No idea on actual amp usage but have a little experience in our last trailer.

Our last trailer 2014 23' FC had 2-100w roof panels & 2 AGM batteries, same appliance set up as our 2017 25'. We boondocked a few times in it, summertime/full to partial sun every day. Elec power was not a problem it seemed in those conditions we could go on forever. The battery drain at night was always recharged enough the next day. I even drained the batteries one morning using our toaster. That night we were fine.

Water and waste water seemed to our biggest boondocking problem.
Time will tell but for now I think were going keep system as is.
Thanks

[2link2]

Originally Posted by field & stream

Hmmm…. True there will be no back feed while running, but there can/will be back feed while engine off and 7pin still connected — like stops for meals, shopping, sightseeing, etc. Why not eliminate that? And as BB said it is a reliable way to pick up a few Ah, so why not?

Another feature is that it converts the alternator output voltage to the higher voltage required by the lithium profile. You imply that the output of your truck alternator is 14.8v, and it may be, but my alternator output voltage is 13.9 and it will not charge my lithium above 60% without the dc/dc converter. I suggest you check the actual output voltage of your alternator.

In my mind, it is a reliable way to pick up some Ah and reduce some slight risk.

Good point on the stopping, didn't consider that. I did check the voltage output so OK there. I think the DC charger is good idea but there are a few other things I need to spend money on for the AS that are more pressing. 1st thing will be trailer tire TPMS, next decent mud flaps, & the biggee FES repair So maybe next year fo a DC charger.
Thanks