What is it?

ColoradoSun

I know the dealer mentioned what the device shown below does (and how to reset it) during our orientation but now I can't remember. It is located on the back wall of the outside storage compartment on our 2021 T@B 400.

pthomas745

It is a battery circuit breaker.

https://tab-rv.vanillacommunity.com/discussion/12451/electrical-connection-in-passenger-storage-area-near-battery-switch

Sharon_is_SAM

What are the green fuse holders for in this picture?  Solar?

ColoradoSun

Thank you. I should have guessed given the location.

rh5555

This is the mystery breaker.  I can think of no good purpose for it on the 400 TABs with AGM batteries.  It limits the current that can flow into or out of the AGM to 40A, which is way too low.  As an example, this was my first experience with it:

When we received our TAB the battery was completely flat (probably some dealership person leaving a light on in the trailer when not connected to shore power).  When I plugged the trailer into shore power to charge the battery, this breaker tripped.  It took me quite a while to figure out the problem, as everything seemed to work except the battery wasn't charging.  Given that the converter is capable of delivering 55 Amps of charging current, why does NuCamp put a 40 Amp breaker in the line?  Makes no sense.  It is a mystery.  My guess:  It is a hold-over from when the TAB was equipped with lesser batteries and overall current draw was a concern, and no one has questioned its continued relevance.

Sharon_is_SAM

I think they actually started out with a 30 amp fuse/breaker.  Depleted batteries kept tripping it.  Then they changed to the 40 amp.   I think I will ask nuCamp about why only 40 amps.

TNOutback

rh5555 said:

This is the mystery breaker.  I can think of no good purpose for it on the 400 TABs with AGM batteries.  It limits the current that can flow into or out of the AGM to 40A, which is way too low. 

Why do you say 40A is too low?  Generically, most AGM manufacturer guidelines I’ve read say the ideal constant current charging rate for AGMs is between 10-13% of the 20-hour rated capacity (224 Ah x 10%-13% = 22-29 A).  Trojan, for instance, says the maximum charge current for their AGMs is 20% of the 20 hr rate.  Harris Battery’s own recommendations say slow charge rate is 24 hrs @ 10 A, or fast charge of 6 hrs @ 40A (for batteries with >250 minutes reserve capacity).

It’s all a bit confusing to me, and based on other posts in this forum, I am highly doubtful that the power converter, the wire lengths and gauge being used is not sufficiently (or efficiently) charging our batteries.  However, it does seem that a 40A breaker is not limiting in any way.  I am interested in fast charging when I am boondocking, but simply plugging my generator into the 30A camper receptacle is not getting anywhere near the ideal charging current.

Sharon_is_SAM

Creed answered that the circuit breaker is to protect the wiring and he assumes that the wiring isn’t rated for anything above 40amps - hence the 40 amp breaker.  

 

rh5555

I guess there are AGM batteries and AGM batteries.  Doing a survey of golf-cart style batteries, I found maximum charge rates of 20% of C20 (Trojan), 25% (US Battery), 35% (Rolls) and even 40% (Odyssey).  I cannot find data for the Harris battery that is installed in my TAB (@TNOutback, could you share that please?).  It seems to me that the 55 Amp charger is appropriate given these numbers and the breaker (if needed at all) should be upgraded to 60 Amps.

You are right that the current configuration of power converter and cabling precludes achieving charging currents that would trip this breaker (which is why I've modified my system to a stand-alone converter mounted right next to the batteries and bypassing the 40 Amp breaker).  However, my original question stands:  Why do we even need this breaker?  The power distribution box has fuses for all the circuits.

P.S. responding to @Sharon_is_SAM, if NuCamp is going to install a 55 Amp converter, then shouldn't they install appropriate sized wiring to match?  In reality, the 8AWG cable they use is good for way more than 40 Amps because it is not constrained and will dissipate any heat it generates readily.  40 Amps is super-conservative.

TNOutback

@rh5555 I found a Battery Care and Maintenance Guide on Harris Battery’s website.  I’ve also sent them an email asking for specific charging recommendations based on the battery model number of those in my 400.

I’ve about decided to install some leads, leaving them near the Alde access hatch, so I can attach a separate (and appropriate) battery charger when I need to fast recharge. I think the power converter is maybe sufficient for slow charging?

http://www.harrisbattery.com/sites/default/files/literature/Battery%20Care%20and%20Maintenance%20Guide_web2_1.pdf

rh5555

@TNOutback, that guide is for their wet-cell batteries.  AGM batteries are another breed entirely - and way, way better.  Other than weight, AGMs are pretty close to Lithium cells in performance.  And they love to be charged fast!

Dutch061

Here is the PDF for the Harris 6 Volt Batteries for reference. 

Brad

ColoradoSun

I don''t see where the Harris spec sheet lists the optimum absorption and float voltage settings for a solar charge controller.

TNOutback

Very interesting, @Dutch061. I have the spec sheet for that same battery model I downloaded over a year ago, and it shows a charging profile for bulk charge amps of 15% of the 20 hr rate.  The one you posted, listing the same exact model number, now shows maximum and minimum values, with a max of 25% and minimum of 10%. That would be a range of 56 amps to 22 amps for bulk charging.

Those batts are not receiving anywhere near that amp range through the power converter and wiring if my Victron battery monitor is correct.

@ColoradoSun reference the “Performance Characteristics” chart at the bottom of the spec sheet for the range of absorption and float charging.

TNOutback

I received this response from Bill Swonger at Harris Battery yesterday when I asked about recommended charging of these 6V+6V AGMs, and if he recommended a charger to use:

You are correct to be concerned about properly charging your 6 volt batteries.  I am not familiar with the system NuCamp uses but it is imperative that the batteries get recharged to 100% as soon as possible.  Short charging can ruin any batteries just as overcharging does also.  This does not have to be a concern with a Dual Pro charger.  The Eagle Performance Series Dual Pro chargers are a very high quality transformer based charger controlled by a sophisticated computer that analyzes the battery or pack, and sets the proper charge algorithm for either flooded, gel or agm.  It then analyzes the state of discharge and recharges according to its programmed parameters.  The Dual Pro charger will hold the pack in bulk longer depending upon the state of discharge.  This feature allows for a much faster recharge.  After the absorption stage it will go into float and perfectly maintain the pack at full charge.

 

As to the bulk stage voltages, we recommend not going over 2.45 VPC or 14.7 volts on a 12 volt pack.  In addition, there should not be an equalization setting used as some of these could force your charge to 15 volts.  Over charging will dry out the acid absorbed in the glass mat separators which will lead to rapid premature failure.

 

With this all being said, we have experienced very few issues with our batteries in the NuCamp system.  To my knowledge they appear to be working very well.  However, if you wish to have a quote on the Dual Pro 12 volt chargers please let me know.  They are very affordable and offer complete peace of mind.

 

If you have any battery questions anytime, please feel free to contact me.

 

Sincerely,

Bill Swonger

rh5555

Interesting, but there isn't a Dual Pro charger for our needs.  They mostly serve the 36 and 48 Volt market, and at a price!  Their only 12V model is limited to 25 Amps.  Sounds mostly like a sales pitch.

One interesting note was to avoid chargers with an equalization phase.  Not a problem with the WFCO converter (as it doesn't have one).  The Victron solar controller seems to disable equalization if you select an AGM battery.

ColoradoSun

The Harris battery performance chart lists 2.45 VPC for absorption and 2.3 VPC for float. Apparently VPC means voltage per cell but I don't know how many cells there are. I hoping it would list what values should be entered for the battery settings in the Victron charger controller.

rh5555

There are 3 cells in each 6V battery, so 6 cells total.  At 2.45V, this means the batteries can be charged with a maximum overall voltage of 14.7V instead of the standard 14.4V, and a float voltage of 13.8V instead of the standard 13.6V.  You could make these changes to your Victron unit, and it may enable you to charge your batteries a little faster - particularly when they are almost fully charged and charging rate is less than the output of your solar panels.

ColoradoSun

Thanks that really helps.

ColoradoSun

Since I set the absorption to 14.7V and the float to 13.8V the Victron Charge Controller is showing the daily maximum battery voltage going up to 15.04V and when in float mode reading 14.1V.  Is this normal? I was expecting the maximum voltage to be closer to 14.7V and the voltage to be 13.8 once it is in float. 
I did have a few things (Alde on propane and the radio) powered for a few hours on the second day. Would that account for the difference?