Low batteries- Gloso trips when I try to charge

WebTab2021

Looking for assistance - I had battery disconnect switch in in the “on”position and lost power to my 2018 Tab 400 without realizing it. My two 200 aH Renogy LiFePo’s got real low - one is at 9 ah’s and the other is at 6 ah’s. Now when I try to charge them, the Gloso trips every time after 3 - 4 minutes. I’m trying to bring the battery up with my suitcase solar panel but I’m in Ohio and it’s almost November so that’s not going well. Has anyone seen this before? My converter is a WFCO 8955 LIS (the one with the switch). 

I would appreciate any guidance!
thanks,
Steve

Marceline

I wonder if you might need to put the batteries on an external charger to bring them back to life. You might need to look at the documentation for the batteries or contact Renogy. 

rh5555

You've stumbled onto one of the deep mysteries of NuCamp.  How do they think it is appropriate to have a 55 Amp battery charger "protected" by a 40 Amp breaker?  Simple solution is to toss the 40 Amp breaker and replace it with a 60 Amp breaker.  Then you can use your charger with impunity.

NuCamp got away with this craziness because the charger never used to enter bulk charging mode with the AGM batteries, and therefore never charged at more than about 30 Amps.  It's a different situation with Lithium, I guess.

SLJ

rh5555 said:

You've stumbled onto one of the deep mysteries of NuCamp.  How do they think it is appropriate to have a 55 Amp battery charger "protected" by a 40 Amp breaker?  Simple solution is to toss the 40 Amp breaker and replace it with a 60 Amp breaker.  Then you can use your charger with impunity.

NuCamp got away with this craziness because the charger never used to enter bulk charging mode with the AGM batteries, and therefore never charged at more than about 30 Amps.  It's a different situation with Lithium, I guess.

Do not do this. Breakers protect the wiring. Doesn't matter how much the charger puts out. Do not increase the size of the breaker without making sure the gauge of the wire plus the length will hold a higher current than the existing 40A breaker.

rh5555

I'm assuming the wiring is 10AWG from charger to battery (like mine is).  10AWG wire is rated for 52 Amps regardless of wiring length.  That 52 Amp rating assumes no time limit, so self heating has to be dissipated.  Transient currents to 60 Amps would be easily handled.  Put in a 50 Amp breaker if you want to play by the rules, and chances are that it won't trip, but it might.  Or put in a 60 Amp breaker and recharge your batteries, then put the 40 Amp breaker back in.  Personally, I'd just bypass the 40 Amp breaker while recovering the batteries, then reinstall it when your batteries are happy.

Sharon_is_SAM

@WebTab2021 - we have seen this when the 400s first came out with the large 200 Amphr AGM battery.  As Marceline suggested, use a smart charger designed for lithium batteries to charge your batteries.  The bulk mode current required to recharge from a very depleted state simply trips the breaker.  

stp2136

As SLJ said, breakers and fuses protect the wiring.  #10 AWG is rated at 30 amps.  If you want the full 55 amps you will need #6 AWG and it can be fused at 60 amps.

rh5555

That 30 Amp rating is for household 120V wiring, where conductors are packed closely together, as in Romex cable.  The 52 Amp rating is for individual wires which can dissipate heat more readily, which is what you've got.  I stand by my statements.  It's all very well suggesting that @WebTab2021 goes out and buys a specialized charger when they have a perfectly good charger already which just needs a little assistance, but some of us don't have money to burn.

stp2136

The amperage rating of any wire is dependent on the temperature rating of the insulation.  Most common #10 copper  wire insulation is rated at 60 deg C and has a 30 Amp rating.  Yes you can run more current than that if you have the correct temperature rated insulation.  For example, #10 wire with THW or THWN which is rated at 75 deg C can carry 35 amps.  But it will get hot and that means there are losses (voltage drop) which we can't afford at the low voltages we run in the T@Bs.  If you are running anywhere near 30 Amps continuously I would recommend going to at least #8 AWG and if running 55 Amps use at least #6 AWG and always protect with the appropriate fuse or breaker.  And don't forget that the terminations must also be rated appropriately for the maximum continuous current. 

pthomas745

 @webtab2021 did you ever get your lithium out of "low voltage disconnect mode?"  The battery and the surge of power it might need to "jump start" it is the issue here.  You may need a separate charger to get the battery to start to accept a charge from the trailer.

Marceline

pthomas745 said:

 @webtab2021 did you ever get your lithium out of "low voltage disconnect mode?"  The battery and the surge of power it might need to "jump start" it is the issue here.  You may need a separate charger to get the battery to start to accept a charge from the trailer.

Yes. I don't know that the WFCO converter is meant to recover a battery from this state, even if it's a lithium-compatible WFCO. 

rh5555

@stp2136, we're basically in agreement.  10AWG wire is inappropriate for the high charging currents that Lithium (or AGM) batteries can draw, but the converter in the TAB generally cannot provide those high currents, so it's all moot.  The problem is that if you draw your batteries down too low, there can be a period of time (an hour or so), when the converter wants to deliver more current than the breaker tolerates.

The OP asks "what can one do?".  I think the options are, starting with the most conservative:

1. Buy an appropriate charger to recover the batteries enough that the internal converter no longer trips the breaker.
2. Reset the breaker every time it trips.  You may have to do this 20 or more times before the converter's output drops low enough that the breaker no longer trips.
   
3. Temporarily jumper the breaker and charge the batteries.  I would suggest doing this for no longer than an hour before reinstalling the breaker.  Repeat if breaker still pops.
   
4. Switch out the breaker for one with a higher current rating.  50 Amps is within the rating of 10 AWG wire when the wire can dissipate heat easily ("single core" in this table) which is the case in our trailers.  If this still trips, you'll have to use option 2 a few times.
   

I hope this helps.  Pick the option that matches your risk tolerance level. 

ckjs

If you are up to this:
temporarily disconnect one of the batteries charge up the other. Once one is topped off, reconnect the other. Perhaps the charger will not “try so hard” to deliver its full output, and avoid tripping the breaker. 

SLJ

ckjs said:

If you are up to this:
temporarily disconnect one of the batteries charge up the other. Once one is topped off, reconnect the other. Perhaps the charger will not “try so hard” to deliver its full output, and avoid tripping the breaker. 

Don't connect a dead lithium battery to a fully charged one. If you have an external charger, disconnect them both and charge each one to 100% separately. If one is fully charged it can try to dump a whole of current all at once into the dead one. Hopefully if this happens the battery's BMS should put a stop to it but it's not a guarantee.

ckjs

SLJ said:

Don't connect a dead lithium battery to a fully charged one. 

If you have an external charger, disconnect them both and charge each one to 100% separately….

Whoops, that’s right. I shouldn’t have tried to simplify the process that much. 

WebTab2021

Hi all - thanks so much for the many great suggestions. Renogy encouraged me to purchase their charger and pull my batteries out of the unit to charge them. I actually had it ordered when I decided to close that circuit one more time to give it a try (for probably the 15th time) and it held as I watched the amps flowing in to drop from over 60a to below 40a.  I chose to cancel the order for the charger. I am guessing that in all those short periods of charging before the breaker tripped, I got enough juice in the battery and it came out of sleep mode.  Whatever the case, both batteries have fully charged now and I am very happy to have not spent any money to correct the issue. Thank you all, once again!

rh5555

Good to know that option 2 (above) does eventually work.  By the way, the wiring on my TAB between the converter and battery as 8 AWG, not 10.  So earlier comments about installing a higher amp breaker are a little less crazy.  8 AWG wire is rated at 75 Amps when using single conductors.

KK1L

I ran into the same issue. Option 2 will stress the breaker with repeated cycling. Putting a 50A breaker in the circuit in my opinion is a better option (what I did). The peak charge current drops off within an hour. In reality the situation of low battery charge is the one time this high a current will occur for more than several minutes...at 50A your batteries wont be providing power long

While on the subject of losses and heat generation...the resistivity of the wire is distributed and therefore the power dissipation (heat...I-squared x R). Where it can be concentrated is at poor crimps, connections, or sharp kinks in the wiring. When adding or modifying pay attention to this.