Quick converter question

Olena

I am just about to buy a new lithium battery for next season and want to make sure I don't have to worry about needing to upgrade the converter in my T@B. I have a Nucamp built (early) 2017 Q plan 320. I am looking at the Enerwatt (a Canadian made battery so maybe my American friends do not know the brand) lithium with 88 Amp hours (it will fit a group 24 space). I have seen different opinions about the converter. Who has the voice of authority on this matter? Verna, are you there?

N7SHG_Ham

Technically you do need a converter with a Lithium profile for charging, lots don't though and if you have solar with a charge controller with Lithium profile you are covered for topping off, but the converter alone will never get it full with lead acid settings. Other option would be external charger with correct settings when you get home.

Olena

I do have 200W of Zamp solar with charge controller (I just bought one of the new lightweight Obsidian portables and can't wait for spring to use it) and my 2017 T@B is hard-wired with the Zamp solar port so I am totally set-up. I will never use the WFCO onboard converter for charging. I guess my question was about something I read in a post about the converter not being compatible somehow with lithium? Maybe I misunderstood and now I can't find the post!

Sometimes I do camp with shore power, but I guess I can always cut off the battery when I am on shore power and then I will have no questions about compatibility.

Olena

OK, I get it. My current converter won't fully top up the lithium battery. No problems for me then. Thanks so much for your advice!

4ncar

Olena said:

OK, I get it. My current converter won't fully top up the lithium battery. No problems for me then. Thanks so much for your advice!

Correct, no problem, other then you will never get the full benefit of your lithium investment. Solar is great, if you can rely on it 100% of the time...

pthomas745

So, when the claim is made that the converter will not "fully charge" lithium batteries, what exactly will the battery get charged to?  70 percent?  80 percent?  95 percent?

ColoradoJon

Lithium batteries have a narrow charge voltage and a different charging profile than lead acid batteries.  You can use your built in converter and it *might* fully charge your lithium battery.  It just won't charge as efficiently as a charger designed for lithium ion batteries.  Lithium batteries can hold a charge voltage over 13+ volts and some lead acid chargers will think the battery is fully charged and shut off.

You should disconnect the battery from the converter once it is fully charged.  You should not keep a lithium battery connected to a lead acid charger to maintain the charge in maintenance or float mode.  Also, use a charger that does not have an automatic equalization mode as the increased voltage can damage the lithium battery.

To answer your question - yes, you can use the onboard converter and it is safe to do so.  It is better to replace the converter with one compatible with lithium batteries, though.

Michigan_Mike

This guy has some interesting info 

https://youtu.be/gJtDHXJeB8Q

Sharon_is_SAM

Good resource @Michigan_Mike.  Although we have no plans at this time to go to lithium, it is very interesting to learn about all the nuances regarding charging, life cycle, storage etc.  Some day in the near future, all RVs will use lithium.

m_lewis

As much as anything, this video pointed out the problem with having the charger/converter some distance from the battery, severely limiting the rate of charge due to voltage drops in the cabling. For those that don't see much difference in 55 amps vs 30 amps of max charge current, consider the time it will take to recharge an 88 Amp Hour to go from 1.6 hours to 2.9 hours, even with large conductors.
Cable resistance and voltage drop is most important with a very large capacity lead acid battery bank or any lithium battery due to the much higher charge currents. 
Even short lengths will be seriously affected by small wire.

ColoradoJon

Good video!  If you aren't going to charge your lithium battery with the proper charging converter then why bother with spending all that money on one?  Just get a couple 6V AGMs and save some money and headache.

Marceline

ColoradoJon said:

Good video!  If you aren't going to charge your lithium battery with the proper charging converter then why bother with spending all that money on one?  Just get a couple 6V AGMs and save some money and headache.

Because there are other ways to charge a battery.
I rarely camp with shore power (a couple of times a year) and I store my trailer on a friend's back 40. So I mostly charge my battery from solar or by pulling it out of my trailer and bringing it home to put it on a battery charger. So I don't see much point in swapping out the converter. I switched to lithium because it gives me 90ah of usable power in a 23 pound battery. Getting 90ah of usable power from a lead acid setup would've greatly increased my tongue weight, which would mean making other changes ($$) to my setup. Frankly, the switch to lithium (even without replacing the converter) has greatly reduced my headaches.
Hope this clarifies things for you. 

Marceline

Olena said:

I do have 200W of Zamp solar with charge controller (I just bought one of the new lightweight Obsidian portables and can't wait for spring to use it) and my 2017 T@B is hard-wired with the Zamp solar port so I am totally set-up. I will never use the WFCO onboard converter for charging. I guess my question was about something I read in a post about the converter not being compatible somehow with lithium? Maybe I misunderstood and now I can't find the post!

Sometimes I do camp with shore power, but I guess I can always cut off the battery when I am on shore power and then I will have no questions about compatibility.

The converter won't fully charge the lithium battery but your solar should (as long as you can adjust the charging profile for lithium) so you should be fine. I've had mine for about a year with no issues whatsoever. 

gderrick

I didn't replace my WFCO, I instead use an old laptop power supply (19V 65 watt) connected in parallel with my solar panel input.  I leave it plugged into an outlet near the battery and while on shore power it supplies input to the solar controller charging the battery as if connected to a 65 watt panel in perfect light.  As an added safety measure I installed a blocking diode to the PS output. 

Sharon_is_SAM

That’s a first!  How did you come up with that idea @gderrick?  

gderrick

If you watch some of Will Prowse's videos where he is testing solar controllers or batteries he often uses a power supply to simulate a panel.  That got me to thinking that your average solar controller has profiles for different battery types and is probably more configurable than most RV power converters so why not harness that solar controller's capabilities to take over the charging role.  My RV's power converter still distributes the DC branches and supplies the house DC power while on shore power I'm simply blocking it from charging the battery.  As for the laptop PS, I tend to use what I have on hand and seeing that it supplied 19V 3.42A that's 65 watts and good enough for my needs - it is also UL listed so I felt better about sticking it under a panel where I and family will be sleeping.  

Sharon_is_SAM

@gderrick  - I subscribe to Will Prowse, too.  Did you let him know about what you did?  Maybe he can do a video on alternative ways to charge a lithium battery!

ChanW

Love that idea. So there's no controller function in the laptop charger?

gderrick said:

If you watch some of Will Prowse's videos where he is testing solar controllers or batteries he often uses a power supply to simulate a panel.  That got me to thinking that your average solar controller has profiles for different battery types and is probably more configurable than most RV power converters so why not harness that solar controller's capabilities to take over the charging role.  My RV's power converter still distributes the DC branches and supplies the house DC power while on shore power I'm simply blocking it from charging the battery.  As for the laptop PS, I tend to use what I have on hand and seeing that it supplied 19V 3.42A that's 65 watts and good enough for my needs - it is also UL listed so I felt better about sticking it under a panel where I and family will be sleeping.  

gderrick

ChanW said:

Love that idea. So there's no controller function in the laptop charger?

The laptop power supply is the Solar Controller's input PV power source.  I don't intend to run in parallel with the actual solar panels connected. 

MarkAl

@gderrick for all the good and useful ideas this forum has I like this best (okay I'm a techie nut). But I have a question doesn't the solar controller attempt to take as much current as the system needs until the voltage drops? For a discharged battery this would shut down the power supply through an over-temp or over current condition I think. Have you monitored the system for this condition? I'm thinking a laptop supply probably is safe and totally works if the battery only needs a float charge.  I have the trailer under a canopy so I don't get solar charging in the winter and I haven't wanted to run the converter or hook a separate battery charger to the system. With this I can just wire the supply with a Zamp connector and plug into my remote solar input.

gderrick

Thanks @MarkAl.  I haven't invested in a 100 ah lithium yet I've been testing against a flooded lead acid and a 30 ah lithium from a tennis ball machine.  I won't be taking the T@B out again until April so I'm holding off buying a 100 ah to get the most life out of the warranty.  You make a good point that the solar controller with a lithium may draw from the laptop power supply at or beyond its limit.  I haven't seen an issue with either of these batteries but neither was that badly depleted and the lead acid is much higher resistance and will never draw like a lithium can.  If that happens I'll replace the power supply with an adjustable one with current limiting.  Should I do that I'll probably move up in voltage to 24V but add a relay feeding the solar controller from the 24V power supply OR the solar port input to ensure that I can never run the solar panel port input and power supply in parallel.  There has to be a way to put this very capable battery charger to work for other than when connected to a solar panel.

Additional:  I did a little reading on MPPT solar controllers and the way they step down the voltage from the PV panel and adjust the current draw to keep the PV voltage at a "desirable level".   Checking the ratings on one of my panels it list Opitmum Operating Voltage at 19.3V; that closely matches what that laptop power supply is putting out so I imagine that should the controller start drawing close to the laptop power supply's 3.42 amp limit that voltage will start dropping and hopefully the MPPT controller will throttle back bringing the voltage back up and lessen the draw.  The PS output is supposed to be regulated but I bet not to the point of max draw. So that little power supply might still work even in a heavy demand situation. 

MarkAl

I think this is a good way to trickle charge either Lead/Acid or Lithium when limited solar is available during storage regardless of the converter problem on Lithium. In my case I don't want to run the converter daily while storing the trailer. A little power supply is much cheaper to replace than a converter or solar charger. 

In the case of both an active solar panel and this supply I doubt the series diode is needed for protection and you lose the voltage to the charger. Most little power supplies would be protected from higher voltages by their rectifying diode and hopefully a protection diode across a regulator if present. As I said I'm more worried that some cheap supplies would burn up if asked to pull too much current.

ColoradoJon

Marceline said:

ColoradoJon said:

Good video!  If you aren't going to charge your lithium battery with the proper charging converter then why bother with spending all that money on one?  Just get a couple 6V AGMs and save some money and headache.

Because there are other ways to charge a battery.
I rarely camp with shore power (a couple of times a year) and I store my trailer on a friend's back 40. So I mostly charge my battery from solar or by pulling it out of my trailer and bringing it home to put it on a battery charger. So I don't see much point in swapping out the converter. I switched to lithium because it gives me 90ah of usable power in a 23 pound battery. Getting 90ah of usable power from a lead acid setup would've greatly increased my tongue weight, which would mean making other changes ($$) to my setup. Frankly, the switch to lithium (even without replacing the converter) has greatly reduced my headaches.
Hope this clarifies things for you. 

I do apologize if you were offended by my post.  You did not mention in your original post that you were intending to use an external lithium battery charger to charge and maintain your battery so I naturally assumed that you were attempting to do so with the onboard converter.

DesertDweller

@gderrick. Kudos to you.  What a great way to repurpose a laptop power supply.  I recently bought a lithium battery and will install it soon.  I have factory installed solar with a Victron charge controller, but was wondering what to do with the very few times I camp with shore power connected.  Your solution seems like a great alternative to replacing the WFCO for those of us who do not use shore power frequently.  Would it be possible to post some pictures of your install?

gderrick

I don't have pictures but I did make myself a diagram.  Some of the images, like the battery, are representative and not actual models.  I had to create some of my own symbols for diagrams.net and I went with what I could find.

Disclaimer:  I have no training or experience that would qualify me to dispense advice on electrical, solar, RV's or any other subject.  I submit this diagram as nothing more than an exercise on alternative battery charging ideas.  And remember, always seek professional advice before attempting any modifications yourself. 

@Sharon_is_SAM - I meant to attach a much smaller jpg but clicked on the pdf by accident.  My attempts to delete it fail.  I can attach the jpg if you wish to delete the pdf. 

Sharon_is_SAM

@gderrick - the PDF size is fine.  One question:  why is the negative battery lead with the shunt going through a cut off switch?

gderrick

That cut off isolates that battery from the Power Converter and Tow Vehicle but the Solar Controller is on the same side of that switch as the battery so still connected when isolated from the main house wiring.  I have to store it with a cover outside and I have mounted a small 20 watt panel on my tongue box serving as a trickle charge.

DesertDweller

Thank you everyone for sharing.  Thanks @gderrick for the wiring schematic.  After looking at everything it occurred to me that for the few times I am camping with shore power and may not have enough sunlight to fully charge the Li battery, I can use the small AC powered battery charger that I already have.  It has different settings for different types of batteries, including Li.  

TomCanada

Sharon_is_SAM said:

Good resource @Michigan_Mike.  Although we have no plans at this time to go to lithium, it is very interesting to learn about all the nuances regarding charging, life cycle, storage etc.  Some day in the near future, all RVs will use lithium.

I just hope they figure out how to charge these in sub-32 temperatures - to me that's the biggest negative of lithium at this point..

VictoriaP

TomCanada said:

Sharon_is_SAM said:

Good resource @Michigan_Mike.  Although we have no plans at this time to go to lithium, it is very interesting to learn about all the nuances regarding charging, life cycle, storage etc.  Some day in the near future, all RVs will use lithium.

I just hope they figure out how to charge these in sub-32 temperatures - to me that's the biggest negative of lithium at this point..

Any number of heated versions on the market already...typically, these use the initial energy from charging to warm the battery instead, then charge it once it’s above 32°F.

NCNative

I swapped out the converter when I got my new lithium batteries.