changing converter

Dutch061

If you go back and read the in depth posts by RH5555 he explains it very well as to why the Bulk Charge doesn't happen with the WFCO Convertor. It is a result of essentially two things.

1. Resistance in the wiring from the factory location of the convertor and the smaller diameter battery cables.
2. The way the WFCO Convertor is programmed (charging rate based on voltages)

I just ordered a PD9260CV today to install under the bed of out 400 as RH5555 did with the "free WFCO" he received from NuCamp. 

We boondock 90% of the time and I need to be able to charge the batteries in less than 20 hours of generator time if I don't have sunshine.

P.S. I wouldn't recommended buying a charger for Lithium Batteries unless you have Lithium, the charging voltages are higher than what should be used for AGM or Lead Acid. Once again, thanks to RH5555 and the testing that was done on the AGM's, I will likely never spend $2K to buy 2 x Lithium Batteries unless I win the lottery. 

Brad

Denny16

Thanks, I knew it was related to how the converter was installed by nüCamp that kept the bulk charge rate from occurring.  I also see the need for it when boondocking and using a generator to charge up the battery, if it gets a big overnight discharge.  

@Dutch061 when boondocking, I have noticed the 193 watt solar will recharge the AGM battery during the day to recover the charge after running the fridge and lights from the previous evening/night.  Could you not run the generator a short period in the morning and again in late pm to top off the batteries with the nüCamp factory converter setup?
cheers

Dutch061

@Denny16

I agree, if there is sunshine and the solar panel is able to have the sunlight hit it, it will take it from 80% to full charge easily in a few hours. But if it is overcast, tree cover, or the solar panel is in the wrong direction I end up using a generator after a couple of days. Unfortunately the amperage drops off very quickly when you start to charge with 120 volts because the OEM WFCO NEVER goes into the Bulk Charging mode. What I have observed is that the batteries will go from 55% to 80% in 2 to 4 hours but to go to a full charge is just not possible with the original WFCO in the original location unless you run the generator for many more hours than is feasible. I think in RH5555's testing it took almost 20 hours to fully charge the batteries.

By changing to a PD9260CV, installing it under the bed, and upgrading the cable sizes for the batteries; I should be able to go from nearly dead (30 to 40%) to full charge in less than 3 hours. 

Of course the goal is to never let the batteries get that discharged but in case they do, I will be able to easily recover.

Brad

Denny16

OK, good.  I was thinking of using the generator like you would the solar, on overcast or dark days, charge the battery in am with the generator and again in pm to top it back up, not letting the battery drop below 80-70% charge.

On our last camping trip in late October, the TaB was in partial shade from a small garden type tree. Solar was running about 50% of max capacity.  We had one night of boondocking, followed by a hookup for several,days, then a PG&E grid shutdown to the entire area for two days, and the solar kept the battery charged, even at reduced charging capacity., we were running the 2-way fridge on 13VDC, lights at night, and the Alde at night set on low, with LP on during power outage.  

The battery did not drop below 70%, with two days and one night of boondocking at the RV park, before power was turned back on.  High winds and a Red fire alert was the reason for shutting down the grid, to prevent a fire from downed power lines, which had previously happened in 2018 in Northern California.
cheers

ScottG

I'm not sure if this is relevant, but here's an interesting tidbit from page 7 of the updated WFCO-8735 operator's manual that appears to explain why we never see the converter kick up to that 14.4V bulk charge:

If the output current reaches its maximum (normally caused by a discharged battery), this will cause the converter to go into Bulk Mode, which means the target output voltage will change to 14.4 VDC and a timer will start. Although the converter is outputting 14.4 VDC, you will not be able to read that on a voltmeter due to the voltage-current relationship. From the paragraph above, as load current increases, output voltage decreases. The actual output voltage will not rise until the load current is reduced, which happens naturally as the battery charges or if 12 VDC appliances are turned off.

Now, I'm not quite sure I follow this explanation. While I've never seen 14.4V on my voltmeter, I'm not sure I've ever drawn the battery down low enough (IIRC ~12.1V) to activate the bulk phase.

Dutch061

@ScottG

As per @rh5555 and the testing and research he done it is related to the resistance in the charge circuit which is caused by the distance from the convertor to the battery combined with the size of wire. It is further compounded by the voltage rising (though artificially) when the charging first starts that prevents the bulk charge mode which is aggravated by the small gauge battery cables. 

Moving the convertor closer to the battery, larger gauge wiring (including battery cables) and an ability to prevent the voltage from surging when the charging first starts are the secrets based on his testing.

The PD9260CV that I ordered has a pendant, that you can press a button and force the bulk mode if it doesn't enter on it's own. Plus, I will be mounting it under the bed and address the wire gauge sizing issues too.

Brad

ScottG

Various sources from WFCO claim the bulk phase is designed for extreme situations and should not--by design--be engaged under normal operating circumstances.

Am I interpreting it correctly that the main purpose for wanting to force a converter into bulk mode is to achieve faster charging when using a generator? 

Dutch061

@ScottG

Yes, if necessary to get it into the Bulk Charging Mode (depending on voltage) otherwise it is nearly impossible to be able to charge feasibly with a generator. Progressive Dynamics also stated that if I were to switch to Lithium batteries in the future (not at all likely after seeing testing results by @rh5555) that this would also prevent me from having to swap convertors again to have the different algorithm and voltages for Lithium. 

Brad

ScottG

Got it--thanks, @Dutch061. While it's not a problem I personally need to solve, I've always been curious about the apparent lack of bulk-charge capability with the WFCO converters and if/why it matters. It always catches my eye when it comes up here.

Not sure if we have digressed from @gregtipton19_'s original question, but since he asked about a four-stage converter I'm thinking it all might be relevant!

rh5555

The WFCO converters are designed for regular wet lead-acid batteries.  AGM batteries can tolerate much more aggressive charging without damage; indeed most AGM battery manufacturers call for 14.4V charging regardless of the state of charge of the battery. 

When I talked to a technician at WFCO, he indicated that they tailor their product to the mass market - which is non-AGM - and have decided not to embrace the AGM market (by adding a switch or something) because of the perceived liability issues (owners of non-AGM batteries switching to AGM mode and ruining their batteries).

I also learnt from the WFCO technician that to enter bulk charging mode, the converter needs to deliver its maximum rated current while the voltage at the output of the converter doesn't exceed 12.8V for the first 15 seconds after powering up the converter.   In my original setup, this could only be achieved when the battery voltage dropped below about 10V (i.e. completely flat).

The Progressive Dynamics folk take a different view, and provide a mechanism to force the converter into bulk charge mode each time you power it up, regardless of the state of charge of the battery.  While not as convenient as a converter with a switch, it is a reasonable compromise.

And yes, @ScottG, the main purpose of forcing the converter into bulk mode is to enable monumentally faster charging from generators. Previously, with the WF-8955 converter located at the front of the T@B400, it took 20 hours of charging to recover my battery from 60% discharged to 20% discharged. After relocating the converter to be next to the batteries, it took just 90 minutes to perform the same recharge in bulk-charging mode.

[Deleted User]

Anybody have thoughts on how 

Xantrex Freedom 458 Inverter/Charger - 2000W - Single In / Single Out [81-2010-12]

compares to renology or Progressive Dynamics?

https://www.mygreenoutdoors.com/xantrex-freedom-458-inverter-charger-2000w-single-in-single-out-81-2010-12/?msclkid=072853e9bc7b1856ab110c866a75ba1f&utm_source=bing&utm_medium=cpc&utm_campaign=MyGreen - (Tested)&utm_term=4581802397627545&utm_content=Non-Map/MRP Products - Computer

rh5555

Interesting product.  My concern would be that the power rating of the inverter seems to be tied to the charging current of the converter.  I agree that a 2000W inverter is an appropriate size (will run the microwave, for example) but the 2000W model gets you a charging current of 100A.  This seems to me to be way too high for our class of batteries.

rh5555

Although I'm a little skeptical about the Xantrex Inverter/Charger, their stand-alone charger, the TrueCharge2 60Amp, seems like the best charger I've yet seen for TABs with AGM batteries:

https://www.mygreenoutdoors.com/xantrex-truecharge2-60a-battery-charger-12v/

This charger has a setting for AGM batteries which neither WFCO nor Progressive Dynamics provide, so you'll automatically get the fastest possible charging when you power it up.

Dutch061

rh5555 said:

Although I'm a little skeptical about the Xantrex Inverter/Charger, their stand-alone charger, the TrueCharge2 60Amp, seems like the best charger I've yet seen for TABs with AGM batteries:

https://www.mygreenoutdoors.com/xantrex-truecharge2-60a-battery-charger-12v/

This charger has a setting for AGM batteries which neither WFCO nor Progressive Dynamics provide, so you'll automatically get the fastest possible charging when you power it up.

OUCH, it has a price to match!!!! I will keep the PD9260V that I ordered to install, but thanks for sharing.

Brad

[Deleted User]

Battery charging via generator (rvbooks.com.au) is a good read and likes Xantrex

[Deleted User]

Would you achieve the same result if you just moved the existing WFCO close to the batteries instead of replacing it with the progressive dynamics converter? Actually I remember now the Dutch061 said its partly a programming issue too, so that answere my question. 

TomCanada

Does this issue (long charging) happen with the newer 2021 Tab 400s as well?  With the batteries under the bed they're a lot closer to the converter than some of the older models.

rh5555

@TomCanada, the answer "yes". 

The problem with the WFCO converter is that it will not enter bulk charging mode (in which the full 55 Amps of charge current is delivered) unless the battery is really, really flat.  This is because the converter was designed for wet cell batteries and is unnecessarily conservative when hooked up to AGM batteries.  The WFCO charger will only enter bulk charging mode if the voltage it measures at its output is below 12.8V for the first 15 seconds while delivering 55 Amps.  In my 2020 TAB400 (with the converter up by the front door), I measured the resistance of the wires between it and the battery.  They measured 0.0375 ohms.  That may not sound like much, but when 55 Amps of current flows through these wires, over 2 Volts is lost.  Thus the battery needs to be below 10.8 Volts (when being charged at 55 Amps) for the converter to see a voltage below 12.8 Volts.

Now in the 2021 TAB 400s, the converter is considerably closer to the batteries, so there will be less wiring resistance and I would guess it to be about half (unless NuCamp upgraded the wiring to something beefier than my 8AWG).  So you are still going to need the batteries to be below 11.8 Volts while being charged to enter Bulk charging mode.  Here's the final nail in the coffin, our AGM batteries voltage rises whenever you start to charge them, and if you charge at 55 Amps, they rise a lot:

This graph is from my heavily modified setup, in which I only have 0.0018 ohms of wiring resistance, your setup will be about 10x worse than this.  i.e. the blue line will be about 1 volt (not 0.1V) above the red line.  With my setup I can just get the WFCO converter to enter bulk charge mode when the battery is depleted to 20%.  There is no way you will ever enter bulk charge mode unless you deplete your batteries to almost zero.

TomCanada

@rh5555 interesting and thanks for sharing all that data. What's the timeframe on your plot?  I'm wondering how much the voltage rises within 15s.

I presume as well that if we have any current at all from the solar controller in parallel (14.4V absorption mode output) that this would be another thing that prevents the WFCO from entering bulk mode. So if you have a solar setup and you have a deeply discharged battery, you'd want to disconnect the solar source in order to get the WFCO to see a low battery voltage & enter bulk.

I'm also curious why the lack of bulk mode entry is the reason for such slow charging - the WFCO theory of operation doc actually says we should be able to charge within absorption mode (13.6v converter output) from 11.9V to 12.7V in under 3 hours, so while bulk would accelerate this even further, 3 hours isn't bad at all.  However, it sounds like people aren't quite getting that - perhaps the resistance of the cabling is playing into the lower current during absorption mode as well, just at a lesser degree?  It still seems your 20hrs from 40% SOC to 80% SOC is somewhat long.  Do you find a solid improvement in absorption mode charging after reducing the resistance?  I'll be checking this on my 2021 Tab 400 when it arrives in the spring - putting in a thick parallel cable run should be pretty straightforward and a win if it helps with charging times!  Even for the small cable for the BMV-712 I'm planning on nothing smaller than a AWG4 or 5..

rh5555

@TomCanada, answering your questions:

The voltage on the battery rises almost instantaneously to the values in my graph when 55 Amps of charging current is applied.  Then it creeps up further as the battery charges.

You are correct that your solar charger will hinder your converter from entering bulk mode.  However, given that your converter will never enter bulk mode anyway, you should keep your solar connected to help the converter out.

The charge times quoted

should be able to charge within absorption mode (13.6v converter output) from 11.9V to 12.7V in under 3 hours

are really misleading for AGM batteries.  To see a voltage of 11.9V while being moderately charged would only happen with a completely discharged battery.  The end voltage of 12.7V would be what I would expect for a 40% charged battery.  They may well be accurate in stating that it only takes 3 hours to charge from a totally dead battery to a battery that is 40% charged, but this isn't what anyone would want to do.  As the battery gets further charged, then the wiring resistance does become a limiting factor and beefing up your wiring will speed up charging.

I have not done this (though I think @Tundra57 has):  Replace the converter section of the WFCO power center with a Progressive Dynamics PD4655V.  This comes with a "pendant" that allows you to force the converter into bulk charging mode.  This (and beefier wiring) should radically improve you charging times.

TomCanada

Thanks Roger - one of my first to-do's with the Tab will be to get the BMV wired up and start plotting some charge times/voltages/currents - should be a fun exercise, and I'll share what I find with the forum.  What interests me the most is 50%-to-100% charge time, for converter-only, converter+solar, and solar-only scenarios.  Think I'll see where I land before going down too many HW upgrade paths.

Also of some interest is speed of charge via the TV's alternator, though I suspect the resistance across the cabling in that case is so high that all we'll do is heat up the wires at best!  Hmmm.. I wonder if I should make sure I wire up my 7-pin connector on my TV with some heavier cables to the battery in the trunk rather than the (front-mounted) alternator.. but then there's also the routing from the trailer's 7-pin connection to the WFCO (any idea what gauge that run is?).  I've seen a thread here somewhere where someone beefed up all the TV wiring - will need to hunt for that again..

Btw - I received a reply from WFCO's tech support folks today.  They say: "The absorption charge of 13.6 volts is the standard in the industry.  The converter not only charges the battery but operates all your DC items in the RV.  If voltage was 14.4 all the time it would be very hard on the DC items and most would not last very long.  Also for customers using a standard single deep cycle batter a continuous voltage of 14.4 could cause the battery to boil."

While I asked specifically about AGM, their statement about boiling is a potential issue with lead-acid batteries, not AGM, and their comment about absorption voltage also seems relevant more towards those batteries as well.  So I wonder - why is nuCamp choosing to continue using a converter that's tuned for lead-acid, while supplying everyone with AGM's?  Boggles the mind a bit.. I wouldn't be surprised to see a 2022 or 2023 with a different converter if they've acknowledged this - though I could equally see them keep the current solution - it's not perfect, but I suppose it works..

Marceline

TomCanada said:

 So I wonder - why is nuCamp choosing to continue using a converter that's tuned for lead-acid, while supplying everyone with AGM's?  Boggles the mind a bit.. I wouldn't be surprised to see a 2022 or 2023 with a different converter if they've acknowledged this - though I could equally see them keep the current solution - it's not perfect, but I suppose it works..

NuCamp doesn't supply the battery. The battery comes from your dealer. 

Sharon_is_SAM

The 320 battery is supplied by the dealer, the 400 battery is installed by nuCamp at production.

tphaggerty

rh5555 said:

@TomCanada, answering your questions:

The voltage on the battery rises almost instantaneously to the values in my graph when 55 Amps of charging current is applied.  Then it creeps up further as the battery charges.

You are correct that your solar charger will hinder your converter from entering bulk mode.  However, given that your converter will never enter bulk mode anyway, you should keep your solar connected to help the converter out.

The charge times quoted

should be able to charge within absorption mode (13.6v converter output) from 11.9V to 12.7V in under 3 hours

are really misleading for AGM batteries.  To see a voltage of 11.9V while being moderately charged would only happen with a completely discharged battery.  The end voltage of 12.7V would be what I would expect for a 40% charged battery.  They may well be accurate in stating that it only takes 3 hours to charge from a totally dead battery to a battery that is 40% charged, but this isn't what anyone would want to do.  As the battery gets further charged, then the wiring resistance does become a limiting factor and beefing up your wiring will speed up charging.

I have not done this (though I think @Tundra57 has):  Replace the converter section of the WFCO power center with a Progressive Dynamics PD4655V.  This comes with a "pendant" that allows you to force the converter into bulk charging mode.  This (and beefier wiring) should radically improve you charging times.

I have installed the PD4665, discussed in another thread. Haven’t replaced the wiring, but did cut the length down considerably as the installed run included about an extra 3 or 4 feet of wire. I may change it out in the future. You also have to change the 40amp circuit breaker for a 60amp one or it pops as soon as the charger enters bulk mode.  It definitely charges much faster when the battery is low, it seems to settle at about a 50amp charge when in bulk mode. I’ve only had it do this a couple of times, but only replaced the charger in September. 

The charger I got has Li mode, wanted that as I will likely go that route soon. Replacement was extremely easy.

One of the things that bothers me about the nuCamp setup is that even when the WFCO does, by chance, start bulk charging, it immediately trips the standard 40amp breaker. This happened to my son when he brought our 400 to us across country last year (and I verified it when we met up). The battery got really low and he could not get it to charge because the WFCO entered bulk mode and then tripped the (stupid) 40amp breaker. Finally got it to charge by plugging in an AC heater to siphon off some of the power which kept the WFCO from going to bulk - at least that’s my theory since it did work. A true catch 22... Either make the charger smaller or put in a higher amp breaker or wiring. Didn’t think to talk to nuCamp about it when we stopped there on our way home. 😕

TomCanada

Let's hope some of their tech people are reading these forums and updating the design for future purchasers. 

In the case of tripping the 40A breaker, I'll keep an eye out for that but since I'm planning on discharging no lower than 50% SOC and my cable runs are long, I might never enter bulk anyways.  I'll watch out for that though - and will likely read up on converter upgrades at some point, especially if lithium becomes more compelling down the road..

Sharon_is_SAM

@TomCanada - the 40 amp breaker issue was just discussed over here:  https://tab-rv.vanillacommunity.com/discussion/12627/what-is-it#latest

[Deleted User]

Tphaggerty, thanks for mentioning the upgrade of the breaker. I'm about to take my 400 in for service to have my converter upgraded and I didn't think of that and I'm not confident the service place would have thought of that.  

TomCanada

Interestingly, the PD4655 seems to have the same (lead-acid oriented) voltage levels as the WFCO 8955:

• BOOST Mode 14.4 Volts – Rapidly brings RV battery up to 90% of full charge.
• NORMAL Mode 13.6 Volts – Safely completes the charge.
• STORAGE Mode 13.2 Volts – Maintains charge with minimal gassing or water loss.

@tphaggerty I also didn't see anything about a Li mode - am I looking at the right model?  You mentioned a PD4665 but that doesn't seem to exist on the PD site (just PD4655).

TomCanada

So I confirmed with my installer that he uses AWG10 from the trunk-mounted battery in the TV to the 7-pin connector, with a 30A inline fuse.  I guess I shouldn't expect any more than 30A coming from the TV to the battery then?  If it was severely discharged I could see it sucking up a lot of current in bulk mode and tripping that fuse, no?  The alternator puts out 160A max and level at battery terminals while idling w/ running + interior lights on is 14.4V, so I could see conceivably blowing this fuse if I let my battery fall too low..

tphaggerty

TomCanada said:

@tphaggerty I also didn't see anything about a Li mode - am I looking at the right model?  You mentioned a PD4665 but that doesn't seem to exist on the PD site (just PD4655).

Yeah, PD4655 is right. There is a model of that one that has a jumper for Li charging. I will have to dig up my order documentation for specifics.  I didn’t order directly from PD, I’ll have to find where I did order from, someone in GA I believe.

Also, I only get about 7A from my TV at the plug, from what I’ve read on the forum, that is about average if you aren’t using a DC-DC converter and a separate wire path from the TV to the Tab batteries.