Camper Trailer Solar/Lith upgrade (WF-8740 Power Center)

[henkew]

I am upgrading my small trailer camper. Currently it has a WF 8740 Power Center, Lead Acid battery, and 80 Watt solar. The solar feed and power from the 7 pin trailer connector are connected directly to the battery. The power center has AC breakers, DC circuits/fuses, and a converter in it to charge the battery and power DC when plugged in to shore power. I’m not sure if the DC circuit to the battery is on it’s own circuit or tied directly to the DC breakers.

The camper is “Solar Ready” which is simply a 12 volt quick connect like the trickle charges for my motorcycles (this is wired directly to the battery). My 80 watt panel/controller plugs directly in to this. I don’t think the wires are big enough for 400 watts/30ish amps.

I am upgrading the solar to 400 watt and replacing the lead acid with a SOK 206AH lithium battery. I’ll need to upgrade my power center (for shore power charging), pick up 4 100 watt panels and controller, get a new battery, and buy the wiring/breakers/cut off switches to install it.

The WF8740 power center is not idea to charge a lithium battery (tops at 13.6 rather than 14.6). I’ll need the newer 8740LiS which is currently hard to get. I think I found one in stock and it is ordered. That should take care of my AC charging for the Lithium battery (it charges for 4 hours at 14.6 before dropping voltage which is, at least, better than the modes for lead acid).

WFCO has suggested I connect the solar controller and lead from the truck directly to the battery. Does that sound like the best approach? That means if I am plugged into shore power (or my 2000 watt generator) and the sun is out, both would be charging the battery (unless I flip the cutoff to solar). Is that a problem? If so, I can get a DCC50S and connect the Power Center to the alternator input so the DCC50S manages the charging when both solar and shore power are available.

With my trailer harness, I’m concerned that if I connect it direct to the battery (as is currently set up for lead acid) it will cause problems because the battery wants to suck up 50 amps. I’m thinking I’ll trip a breaker but not sure. My truck is a 2019 Dodge Ram 1500 and I am not sure yet how it is set up to handle feeding a power hungry battery.

So my questions are:

• Is the 8740Lis necessary. I’m thinking yes since I store in garage out of sun and need shore power to keep the battery charged.
• Where do I connect the Solar (direct to battery from controller or use a DCC50S to manage the power center and solar)?
• How do I connect the power from the 7 pin trailer harness (direct to battery, through DCC50S, or …?). My understanding is this really doesn’t offer much power anyways so not a big issue.

 

[John Frum]

I’ll need the newer 8740LiS which is currently hard to get.

There are way better options.
Suggest you just turn the converter breaker off and use a proper charger or inverter/charger to great effect.
There are many reason why and I would be glad to lay them out if you are interested.
If not, I will save my keystrokes.

 

[henkew]

There are way better options.
Suggest you just turn the converter breaker off and use a proper charger or inverter/charger to great effect.
There are many reason why and I would be glad to lay them out if you are interested.
If not, I will save my keystrokes.

I'd love to hear your thoughts!! Thanks

 

[John Frum]

I'd love to hear your thoughts!! Thanks

You will want to have your lfp batteries inside for climate control.
Its best to have the chargers as close to the battery bank as possible to avoid voltage drop between charge source and the battery.
Even the new converters are generally not well suited to charging lifepo4 batteries.
The converter vendors just want to sell you a new converter.

This is a decent charger for your application. https://www.aimscorp.net/ac-convert...art-charger-75-amps-listed-to-ul-458-csa.html

This is an inverter/charger which is tailor made for the rv usage model.

Samlex EVO-2212 2200W, 12V Pure Sine Inverter/Charger | DonRowe.com

The Samlex America EVO-2212, 2200 Watt, 12 Volt Pure Sine Wave Inverter/Charger with 100 Amp Charger is a rugged inverter/charger designed for mobile and off-grid applications

www.donrowe.com

The inverter/charger is a high quality low frequency inverter with a configurable low frequency disconnect.
It also has a configurable charger.
It also has an automatic transfer switch that makes connecting/disconnecting from show power easy and safe.

Both of these options are better than a converter and the latter is far far better.
You should check the sok battery and see what its max continuous discharge rate is.
I think you said you already have a 2000 watt inverter.

A 2000 watt inverter can draw a lot of current.
2000 ac watts / .85 conversion factor / 10 volts low cutoff = 235.294117647 service amps.
From memory sok batteries can only deliver 50 amps continuous.

As far as charging off the alternator I urge you to avoid the renogy product line.
Renogy support has earned a bad reputation over the last couple of years.
Victron and sterling are better choices imho.

 

[henkew]

You will want to have your lfp batteries inside for climate control.
Its best to have the chargers as close to the battery bank as possible to avoid voltage drop between charge source and the battery.
Even the new converters are generally not well suited to charging lifepo4 batteries.
The converter vendors just want to sell you a new converter.

This is a decent charger for your application. https://www.aimscorp.net/ac-convert...art-charger-75-amps-listed-to-ul-458-csa.html

Yes, batteries going inside!

Excellent, thanks for your input. The SOK 206AMP dischargers at 100A max. I'm going to use a small inverter, maybe just 1200/1500. We don't have a high need for AC with our setup. It's a small trailer... just the basics for two.

If I was running a higher bank of Lithium power, I would have looked more into a dedicated converter to charge. I don't see us going more than just 1 206 AH battery, which means the $200 power station would charge it fairly quick. So for ease of setup and cost, I had planned on going that route. I'm going to look at it again though based on your suggestions, thanks! I really just need to keep the batteries charged while parked in the garage, and be able to top them off with our 2800 watt generator when the sun isn't cutting it.


Any suggestions on how to connect my solar controller and truck 7 pin connection power? Direct to battery along with whatever converter or charger I go with?

 

[henkew]

OH, by the way. 100% yes on poor service from Renogy. My dad bought a system from them and installed on his motorhome... he's been trying to contact them for two weeks. They haven't updated a ticket, answered the phone, or responded to emails at all. So yeah, I think you are right there and I will look for another option. If I don't need to manage the solar and AC - Converter charging the battery at the same time, then I don't need that device anyways and I can get a regular Solar controller.

 

[John Frum]

Yes, batteries going inside!

Excellent, thanks for your input. The SOK 206AMP dischargers at 100A max. I'm going to use a small inverter, maybe just 1200/1500. We don't have a high need for AC with our setup. It's a small trailer... just the basics for two.

100 amps * .85 conversion factor / 12 volts low cutoff = 1020 ac watts.

If I was running a higher bank of Lithium power, I would have looked more into a dedicated converter to charge.

Please just forget about standard rv converters.

I don't see us going more than just 1 206 AH battery, which means the $200 power station would charge it fairly quick.

What is a power station?

So for ease of setup and cost, I had planned on going that route. I'm going to look at it again though based on your suggestions, thanks! I really just need to keep the batteries charged while parked in the garage, and be able to top them off with our 2800 watt generator when the sun isn't cutting it.

Its not good for lifepo4 batteries to be stored full.
Even worse to be full and trickle charged.

Any suggestions on how to connect my solar controller and truck 7 pin connection power? Direct to battery along with whatever converter or charger I go with?

The charge sources, batteries and loads are all connected in parralel.
Typically using bubars.

For the positive side I like these because each position is fused.

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder | Waytek

Littelfuse 0FHZ0007Z FHZ Series ZCASE Fuse Holder, 7 Stud Assembly with Bolts and Bus Bars, 400A is in stock and ready to ship. Order today!

www.waytekwire.com

For the negative side something like this is fine.

Blue Sea System 2104 PowerBar Terminal Block

Blue Sea Systems 2104 PowerBar BusBar Four 3/8"-16 Studs, 600A, is in stock and ready to ship. Order today!

www.waytekwire.com

 

[John Frum]

If I don't need to manage the solar and AC - Converter charging the battery at the same time, then I don't need that device anyways and I can get a regular Solar controller.

Its not hard to manage multiple charge sources.
Just make sure the aggregate current does not exceed the battery specs for continuos charge current.

 

[henkew]

What is a power station?

Its not good for lifepo4 batteries to be stored full.
Even worse to be full and trickle charged.

The power station includes the RV Converter you suggest to avoid I do know a lot of people are using this for lithium batteries with success. Probably, like me, smaller systems. And I should have said Power Center (WFCO product title).

WFCO Technologies - Innovating the Future of RV Power

WFCO Technologies is committed to simplifying, enhancing, and optimizing every RV owner’s experience through advanced power technology and proven support.

wfcoelectronics.com

I won't keep it plugged in all the time in garage, that should address the trickle/topped off issue. Thanks for that tip.

I like that fused block! Better option that I had planned on, thanks!

 

[John Frum]

I like that fused block! Better option that I had planned on, thanks!

Not totally.
lifepo4 batteries have a very low self discharge rate.
If you are going to leave the sit for a while its best to discharge them to ~50% SOC.

 

[henkew]

Its not hard to manage multiple charge sources.
Just make sure the aggregate current does not exceed the battery specs for continuos charge current.

The SOK has a max 50 amp charge limit. But it also has a smart battery management system, low/high temp cutoff, over charging/discharge protection. So I need to make sure there is never more than 50 amps being dumped into the system, or will the battery auto manage if, at times, there was?

SOK Battery

SK12V100,SK12V206,SK12V206H,SK24V100,SK48V100

www.sokbattery.com

 

[John Frum]

The SOK has a max 50 amp charge limit. But it also has a smart battery management system, low/high temp cutoff, over charging/discharge protection. So I need to make sure there is never more than 50 amps being dumped into the system, or will the battery auto manage if, at times, there was?

SOK Battery

SK12V100,SK12V206,SK12V206H,SK24V100,SK48V100

www.sokbattery.com

The bms disconnect mechanism is meant to be a reserve parachute.
Not meant to be your primary means of low or high voltage disconnect.
You charger should always stay within the safe envelope as should all your loads.
BTW you can cause a battery to degrade from voltage stress even within the "safe" envelope enforced by the bms.

 

[MarkF]

My RV has a WFCO 8735, 2015 vintage and it charges my 272ah lithium at around 12 amps then at 9. It will bring it up to 99% given enough time. The odd thing is at some point during a multi day camp stay, after the converter has charged the battery the converter stops supplying 12v power to my trailer and starts discharging my battery. Shutting the power off at the pedestal and turning it back on doesn’t make make the converter come back on. If I turn off the battery the converter picks up the 12v load. Odd…

I wouldn’t count on the 7 pin for any charging. In fact, on my tow vehicle, I had to pull the 12v fuse because the tow vehicle was taking 4 amps of power from my fully charged lithium battery going down the road.
I installed a 30 amp victron non isolateded Orion tr smart Dc-dc charger and I’ve been happy with it. I ran 2awg positive with a breaker from the car starter battery and picked up a chassis ground at the back. It works well.

 

[time2roll]

WFCO 8740 should bulk/absorption charge to 14.4 volts, operate at 13.6 normally and drop to 13.2 volts for storage.

https://wfcoelectronics.com/product/wf-8740-40-amp/

14.6 volts is a bit overrated for LFP and 14.4 should be fine to get you 100% charged. Trouble with WFCO is that with lead-acid it very often never switches to 14.4 bulk mode. Instead WFCO languishes at 13.6 volts which is a trickle charge for lead-acid but will still charge LFP fairly well. Due to the lower resistance of LFP you have a good chance the WFCO will operate better with the new batteries. Give WFCO a try and see what goes.

Worst case you are still at 13.6 on the WFCO and you let the solar take you to 14.2/14.5 volts daily.

I would not immediately change the converter. Please post your results.

 

[rmaddy]

The SOK has a max 50 amp charge limit. But it also has a smart battery management system, low/high temp cutoff, over charging/discharge protection. So I need to make sure there is never more than 50 amps being dumped into the system, or will the battery auto manage if, at times, there was?

SOK Battery

SK12V100,SK12V206,SK12V206H,SK24V100,SK48V100

www.sokbattery.com

Just make sure your charging sources are setup so they don't charge higher than 50A. SOK actually states 40A is the recommended charge current. 50A is the max.

If you have a need to charge at a higher current, use two 100Ah SOK batteries in parallel instead of using one 206Ah. Two in parallel can accept twice the charge current.

 

[RF_Burns]

Further to SmoothJoey's recommendation of the Samlex EVO series... I've had an EVO-1212 for about 3 years and love it. Just converted to LFP batteries and a MPPT solar controller. My EVO's inverter is rated at 1,200 watts rather than the 2,200 watt unit that SmoothJoey recommended. The EVO is completely programmable so it was just a few button presses to change the charging profile.

With the EVO, you connect solar controllers through it's External charger input. The EVO then controls the total charging current by subtracting the external charge current from its supplied current. So if you have the EVO set to 50Amp Bulk current and your solar is supplying 10Amps, the EVO will only supply 40Amps to keep the total current at 50Amps.

I recently changed the charging voltage to 13.5V (lowest setting) because we will not be using the motorhome for about a month. But I still need to have it plugged in because it's all-electric refrigerator is my shop's beer fridge! I'm hoping this lower charge setting will make the LFP battery happy while not in use.

The EVO has a built-in transfer switch and the inverter sine wave sync's to the power-line frequency for near seamless transfers to/from the inverter. My unit has only one external power input whereas the larger units can switch between grid/generator/inverter. That's ok because with my small motorhome I manually plug the landline power cord into the generator.

We have an all-electric fridge which the EVO-1212 handles easily and the sync'd inverter makes the transfer seamless to the compressor motor, so no more stalled compressor.

Just my 2 cents.

 

[henkew]

WFCO 8740 should bulk/absorption charge to 14.4 volts, operate at 13.6 normally and drop to 13.2 volts for storage.

https://wfcoelectronics.com/product/wf-8740-40-amp/

14.6 volts is a bit overrated for LFP and 14.4 should be fine to get you 100% charged. Trouble with WFCO is that with lead-acid it very often never switches to 14.4 bulk mode. Instead WFCO languishes at 13.6 volts which is a trickle charge for lead-acid but will still charge LFP fairly well. Due to the lower resistance of LFP you have a good chance the WFCO will operate better with the new batteries. Give WFCO a try and see what goes.

Worst case you are still at 13.6 on the WFCO and you let the solar take you to 14.2/14.5 volts daily.

I would not immediately change the converter. Please post your results.

I had already ordered the 8740LiS to replace the 8740 in my trailer. I considered just sticking with the 8740, but when parked in my garage, the solar isn't going to contribute anything. And we do use it as a guest room in the garage when kids visit. I figured the added circuitry for the lithium was worth the $200... but I am fairly new to all this. Maybe it wasn't worth it... hopefully I can get a few bucks for the used 8740.

WFCO Technologies - Innovating the Future of RV Power

WFCO Technologies is committed to simplifying, enhancing, and optimizing every RV owner’s experience through advanced power technology and proven support.

wfcoelectronics.com

From the manual:
Bulk mode output voltage 14.6 VDC and allowing the maximum current to flow as required by the loads. The bulk mode stage could last anywhere from 1 to 4 hours based on the battery and load current which is being used. For a full battery, the bulk stage has a minimum time requirement of 1 hour, which allows the lithium cells inside the battery the time required to “balance”. For an empty battery, the bulk stage has a maximum time requirement of 4 hours. If your application requires longer than 4 hours (such as a larger battery bank > 200 Ahr), a simple cycling of power will reset the timers.

 

[Short_Shot]

WF8740 does not max out at 13.6vdc.

It has a 14.4 volt bulk mode and 13.2v float. It's not inherently unusable with lithium as such, and does not do equalization.

This is all in the manual.

It is definitely better to upgrade to the lithium version though. I'm debating doing this for mine.

 

[Short_Shot]

Oh and since it tops out at 14.4, you should be able to just hook up the solar controller and send it and it'll get you that last 0.2 volts and likely trigger the 8740 to actually stop charging in bulk because it'll think the battery is full.

Of course this depends on the accuracy of the voltage measurements in the two chargers.

Personally I think the slightly lower voltage is ideal for lithium since it's not constantly trying I charge to 100% capacity, but I'll know more in a couple months once I've messed about with my camper when my lithium cells arrive.

 

[henkew]

Oh and since it tops out at 14.4, you should be able to just hook up the solar controller and send it and it'll get you that last 0.2 volts and likely trigger the 8740 to actually stop charging in bulk because it'll think the battery is full.

Of course this depends on the accuracy of the voltage measurements in the two chargers.

Personally I think the slightly lower voltage is ideal for lithium since it's not constantly trying I charge to 100% capacity, but I'll know more in a couple months once I've messed about with my camper when my lithium cells arrive.

I wish Renogy had better support. The DCC50S looks like a cool product that could manage the charging from multiple sources a little cleaner. But after the problems my dad had with them, and the fact they haven't answered a couple presale questions I had for them 2 weeks ago... I'm thinking I'll stay away.