2019 TAB 400 Battery Charging

JeffroNC

I have a 2019 TAB 400 with the solar package. We have been out for 7 weeks and just completed 10 days in the shade with no hookups and temps from 30-40F at night. On the Victron, the battery would go down to about 56% in capacity and I ran my gen 3 hours a day to bring it back to the mid-70s. We were running the AC/DC fridge on DC, heating with the Alde, and I ran my CPAP. We also used basic water, lights, etc. and we watched a video some nights. I am satisfied with the performance and my generator used about .75 gal of propane each day.

Now we are plugged in. The charger kicked in and quickly brought the battery to 76% in a few hours as usual. Now it is the next morning and I am at 83% on the Victron which shows that we are charging at .8A. I will get solar today as we are ideally positioned. In fact, we went 4 days in death valley without starting the generator so it works great.

But if we didn't, can I figure that the battery has 17% of charge to full which is 38Ah of the 224 Ah and at .8A, it will take 47 more hours to charge?

Would a different charger complete more quickly? What about the replacement factory unit with the program override pendant? Or an external unit?

Is it important to fully charge periodically?

Also, another factor I hear about Lithium batteries is that they charge more quickly. Something to think about?

I ask this because I have been arranging campsites with power for one or two days between dry ones to get the battery charged and other services. If I need two days to charge, I can figure that in.

I have learned so much here and we have had a very smooth trip as a result. Thanks!

pthomas745

If you are trying to measure your state of charge while running anything inside the camper, the battery will always read low.   To answer your question, you need to see what your state of charge is when the battery is "rested", which usually means turn the battery switch off and let the battery sit for an hour.    Even if you just turn the switch off for a few minutes and watch your Victron you will see the numbers change.

Cbusguy

I see you mention the percentage of the battery.  Where are you getting that number?  off the solar charge controller?   If you are using battery voltage it is probably best guess,   did you take the time to adjust the victron for your specific battery type?

If you want the real scoop on whats happening to your battery a shunt style amp meter in line with the battery will provide that information.   It will track your amp hour usage and show how many amp hours are left in the battery

Sharon_is_SAM

@JeffroNC, is the Victron you refer to a solar charge controller or a battery monitor?
Regarding charging - charging through the converter can be slower.  Try using a charger with a dedicated AGM mode.  I think you will see a difference.

JeffroNC

Yes, it it is a BMV712 With a shunt. Good trip on letting the battery rest. Once all the draws were gone, the monitor reset to 100%. 

rh5555

There are a couple of problems with the 2020 TAB400's charging system:

• The converter (the thing that charges the battery from shore power) is too far from the battery.
• The converter has no way to be forced into a high rate charge mode

The consequence of the first problem is that there is 37.5mΩ of resistance in the wiring between the converter and the battery.  When the converter is being used to charge the battery, the charging current causes a voltage drop across this resistance that makes the battery appear to be more charged than it actually is.  This causes the converter to never use the highest charge rate (Bulk charging) and to prematurely shift from its middle charging rate (Adsorption charging) to its lowest charge rate (Float).  Thus it takes forever to charge the battery using the converter. 

So in answer to @JeffroNC questions:

Would a different charger complete more quickly? What about the replacement factory unit with the program override pendant? Or an external unit?

To get a faster charge, you either need to move the converter to be close to the batteries or use a converter with an override pendant or both.  I have been testing out some options, and should be able to offer a modification which will allow fast charging when using shore power (or a generator) soon.  NuCamp has been interested in this problem and supportive of my research to find a good solution.

Denny16

You can reduce or eliminate the voltage drop by changing the wire from the charger/converter to the battery with a larger gauge wire, their are charts to show voltage drop in DC wires by gauge size.  
Cheers

rh5555

In theory, yes, but in practice, no.  For the existing converter to work properly, it needs a maximum lead resistance of about 2mΩ.  So you would need leads ~20x bigger than the existing leads, and there isn't room in the conduit for them.

Denny16

Not so sure youmwould need that big of a wire?  The 2018 TaB 30-amp AC converter is connected to the battery with a no. 10 AWG wire, which is rated for a 3% drop over 0-6 feet.  The new new location up front, let’s say it is a 20-foot wire run, you would need a no. 6 AWG wire, which is about 1/2 inch (13.3mm) in diameter.  Yes this is a much larger diameter wire than the small no. 10, and is currently used, and is not going to be easy to route, but doable.   I have used no 6 wire for battery buss cable runs in a large boats for 30-amp loads.  I do not think you need a no O or OO AWG cable to adequately charge a 200 amp battery.

Tundra57

I have a 20 amp battery charge controller with a DC input (mine is 10 to 16v input). I use this to allow my truck to charge the 2019 tab 400 battery. if I installed this right by the battery, fed from the converter by the door wouldn't this solve the problem? Currently it is installed between the tab trailer plug 12v input and the trailer junction box so it only deals with the TV charging issue. The charger was not expensive. Or since the power inlet plug is very close the the battery, couldn't I just put a 110v input charger right there under the bed? Saves all this technical stuff.

rh5555

I got my years mixed up and my comments refer to the 2020 TAB 400 which has a 55 amp converter located up front and 8AWG wiring to the battery.  (Don't know what the 2109 has).

The AGM batteries installed in the 2020 models are happy to be charged at 55 amps, and obviously charging times will be quicker at such currents.  The difficulty is getting the converter to use the Bulk charging mode which delivers this current.  The voltage drop down the 37.5mΩ leads at 55 Amps is over 2V.  This means the converter thinks the battery voltage is 2V higher than it really is, and then slows down the charging accordingly - through Adsorption and all the way to Float mode.  Using a Progressive Dynamics #PD4655V replacement converter with an override pendant would help:  Forcing the converter to remain in Bulk charge mode with an output voltage of 14.4 volts will charge a 20% depleted battery with an terminal voltage of about 14V (while being charged) at about 10 Amps.  This is obviously way better than the 0.8 Amps @JeffroNC observed.  But to do better than this, you need to radically reduce the lead resistance.

Please note that I haven't tried using the #PD4655V so don't know how well it works.  Also your charging rate will vary depending on your overall wiring resistance.

rh5555

@Tundra57, I honestly don't know if using a charge controller would help.  The problem is that the converter used is "intelligent" and restricts the charging rate depending on how charged they think the batteries are.  I've no idea what they would "think" if connected to a charge controller.

The 110V input charger should work if you disconnect the battery from the converter while using it.  I'd worry that they might fight each other if connected simultaneously.

Denny16

OK, I see the issue, did not know you were referring to a 50 amp charge circuit.  So you would need a no. 4AWG cable to reduce the voltage drop, net exactly a “small” wire at almost 1-inch diameter, and about 1.5 lbs per 10-feet

TNOutback

This is a topic that is over my head, and I appreciate the insights here.  I am concerned now that my batteries are not being charged like they should be due to the distance between the converter/charger and the batteries, along with the wire gauge used.  Seems like this may be a design issue that NuCamp needs to know about.

rh5555

Nucamp is aware of the problem, and it looks like they've moved the converter back to be closer to the batteries in the 2021 model.  They have been quite helpful, and have procured for me a replacement converter which can be mounted next to the batteries on the 2020 model.  I will be installing and testing it next week.  Expect a write-up soon after that.

Denny16

Yes, keeping the converter/charger close to the battery is the best solution, or add in a dedicated AC/DC three stage marine type (they are sealed) three stage battery charger in the battery compartment, and disconnect the AC/DC Converter power panel from the battery, so you do not have to reroute the entire trailer wiring, and can leave the fuse panel where it is at.
cheers

N7SHG_Ham

Another unintended consequence of moving stuff around, the 400 started with the converter pretty close to battery, but then started adding bigger fridges which caused a bunch of other things to get shuffled, everything is a compromise!

Tundra57

So if I am understanding the posts on my tab 400 2019 my options are:

Beef up the wiring dramatically.

Fit a seperate ac powered dedicated battery charger next to the battery and disconnect the tab charger completely.

I like option b.

Any idea on the charge rate of the tab charger so I can match it?

Also it would have been better if the tab charger had remote battery voltage sending independent of charging cable length.

rh5555

@Tundra57 you can find the theoretical charge rate by looking at the part number of your current power center.  I have a WF-8955, indicating a 55 Amp charger.  Let me know what you have.  Also, where is your power center located?  Fore or aft?  Do you have the 2 x 6V AGM batteries?

Also totally agree about remote sensing (or a using 4-wire system (2 leads to charge, 2 leads to sense battery voltage)).  No one seems to make these except for very high-end units.

Denny16

If you are running a single or dual 12VDC Battery, a marine charger like this will do the trick:
https://www.westmarine.com/buy/promariner--prosport-6-heavy-duty-marine-battery-charger--19781798?recordNum=18

Tundra57

@rh5555 my plan is to disable the 8955 charging but leave the battery attached to power the distribution center. I have contacted wfco how to do this. It looks like the converter part is wired seperately so it should be easy. Then I'll fit a seperate charger like @Denny16 suggests. The main power inlet is right there and I can add an ac breaker to my additional DCdistribution panel under the 3 way fridge.

You are correct I have the two 6v batteries and the wf 8955 PEC @rh5555 , the write up on the 8955 says the bulk rate is driven by the current draw to the battery, so I have missed something in your explanation. Can you dumb it down for me lol.

Tundra57

@Denny16 the charger you recommend is only 6amps. The 8955 says it's 55Amps. Also I have dual 6v batteries, don't know if this makes any difference so I'll look for something with more "go".

Denny16

OK, then you might be better off with a dual 6-volt Charger, that charges each battery.  That is how dual 13/24vdc marine chargers work.  Going to a bigger charger just charges the batteries faster in bulk rate.  So the 6 amp would charge up a 100 amp loss in 16 hrs, or overnight at a full hookup.  

How fast do you need to charge your batteries?  You do not need a 50 amp charger for a 200 amp battery bank, which only gets discharged 50% or 100 amps. Charge your batteries too fast, and you shorten their life.  

I doubt the TaB Charger is much larger than an actual 10 amp charge circuit (if that large), or it would be using larger gauge cables to the battery hookup.  A 50-amp automotive quick Charger has something like no 8 or 6 gauge cables (like is used on jumper cables).  There is more to modern battery chargers than the amp rating.  
cheers

Tundra57

Victron does a 30Amp Bluetooth. Still looking for a 55Amp Bluetooth charger..might as well get data from it.

Denny16

 Victron MPPT are solar charge controllers, a much different ball park, or e you looking for an AC battery chargers.
cheers

rh5555

I need fast charging to recover my 210Ah batteries off a generator.  I cannot run a generator overnight to charge them.  The existing WF-8955 is quite capable of charging my batteries at 55 Amps, but the existing wiring has too much resistance to allow this.  Disabling the existing converter and adding a new converter near the batteries is the way to go.  There are 2 moderately priced converters that can do the job:  The WFCO WF-9855 and the Progressive Dynamics PD9260. 

My experience to date of moving the WF-8955 converter section out of the power center, and installing it near the batteries, is that it really does the job, provided the resistance of the leads to the battery are very low, like 2mΩ.  For me, that meant using 2 AWG wiring:

This shows the unit with the cover I made for it removed.  I will be replacing this with the WF-9855 next week which will look way more professional, and can report then. The attached pdf shows how this is wired in.  The performance?  Before moving the converter it took 20 hours on shore power to recover the batteries from 60% depleted to 20% depleted.  After the converter move, it takes 90 minutes.

Denny16

I see where you are coming from now. Here you go, 2 hrs charging time to recover 100 amps:  https://www.galco.com/buy/Mastervolt/44010500?source=googleshopping&utm_source=adwords&utm_campaign=&gclid=EAIaIQobChMIhcX08-OE6AIVg6_sCh0q9gj7EAQYAiABEgJlZvD_BwE

Big chargers are not inexpensive however.  Good luck.
cheere

rh5555

The WF-9855 is considerably cheaper: https://www.amazon.com/WFCO-WF9855-WF-9855-Mount-Converter/dp/B004A30UHG about $150.

Sharon_is_SAM

@rh555, what kind of heat, if any, is generated with this rapid charging?

rh5555

Good question!  I did the experiment in the pacific NW when it was pretty cold out, and I had the bed panel removed.  I didn't notice any local warming in the vicinity of the converter.  I'll be doing the change-out to the WF-9855 in Arizona (where our TAB is hibernating).  I'll be sure to monitor temperature when I test the new setup.

Tundra57

@rh5555 . I see the fan went with it. Does it run? I wasn't sure if it was commanded from the distribution center.