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Forum Home > Mods and Upgrades > Stock charger limitations for lithium battery upgrade

Doug Duncan
Member
Posts: 44

I wanted to alert everybody who is considering upgrading to LiFePO4 batteries that there is a limitation if you have the WFCO 9835 converter/charger that was supplied in the August 2017 build. 

Battle Born Batteries shows that the WFCO 9835 is compatible with their lithium batteries, which it is, sort of. The problem is that the charger won't charge the lithium battery up to 14.4 volts under all conditions. For example, if your battery is at 13.2 volts the charger will keep it there with its float (trickle) automatic setting and won't kick in to the bulk (quick charge) mode. So your battery will stay at 13.2 volts. According to an email from Battle Born, "You have to drain your batteries to 12.2V in order for the charger to kick back up to the boost charge. The WFCO has problems with this issue."

A second limitation is the wiring from the charger to the battery is AWG 12 about 7 feet long, which limits the current to about 20 amps (the WFCO is rated at 35 amps, so the wiring is undersized as installed). So if you upgrade the charger to a lithium-compatible charger, the wiring has to be upgraded as well. 

The lithium battery should charge fully from your tow vehicle alternator if you are set up to tow that way with a 7-pin plug.

So the WFCO will work, but not very optimally.


April 11, 2018 at 12:27 PM Flag Quote & Reply

Dave & Paula B.
Member
Posts: 228

Thanks Doug for the information.  The Battle Born battery will be our next upgrade when eventually our present set-up will need replacing.  Our 2014 LS only came with a inexpensive battery charger, not a converter/charger, which needed replacing in less than 1 year because it developed a very loud buzzing sound.  We now have a CTEK charger as well as an adjustable solar controller.  I will be very interested in your set-up and it’s performance, so please keep us up-dated.

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April 12, 2018 at 12:31 AM Flag Quote & Reply

Doug Duncan
Member
Posts: 44

I will write up the installation and performance when I am done. Right now let me just say that it is not a "drop in replacement" as you might be led to believe.

April 14, 2018 at 9:29 AM Flag Quote & Reply

Doug Duncan
Member
Posts: 44

I installed (sort of) a Progressive Dynamics 9160AL charger/converter today and used it to charge the Battle Born LFP battery. I bought the charger from Battle Born and it is supposed to be compatible with the BB LFP battery, without the issue that the WFCO has that I mentioned in my original post. The charger/converter has a 60 amp rating to take advantage of the high charge rate the LFPs can accept. (The sort of installation lacked the 6 gauge wire I had ordered but didn't arrive as promised, so I fabricated some 4 ga terminals for the charger and used 4 ga jumper cables from the charger to the battery.)

Using the 60 amp charger validated my concern in my original post. The initial charge was at 45 amps, which far exceeds the capacity of the 12 ga wire installed with the WFCO charger/converter. The charge rate settled down into the mid-30 amp range for half an hour - still exceeding the 20-25 amp capacity of the factory wiring for the WFCO. 

When the 6 ga wire and lugs arrive and I hard wire this in, I will repeat the experiment and report any differences. It is possible that the charge rate might be higher after replacing my jury rigged system.

April 25, 2018 at 5:46 PM Flag Quote & Reply

Doug Duncan
Member
Posts: 44

This is a duplicate of a post I made to the Fiberglass RB forum. I know some folks are interested so I'm posting it here, too.

I finished the LiFePO4 battery installation yesterday. We used the Li battery boondocking for 4 days a few weeks ago but I finally hard wired in all the pieces, including the ability to charge while driving. I am no expert in batteries and chargers, I am a geologist. So I may have done something really stupid in my installation. I am only describing what I did. Please do your own research and make your own decisions.

Putting in a single Battle Born 100 Ah battery ended up not being a drop-in installation. It did eliminate the need for a battery management system, which made the installation much easier. If you mainly camp in RV parks and can plug in every night, you can just drop in the BB Li battery and be fine (but then you don't need a Li battery) but if you boondock, you need to make some changes. Only the charger wiring is absolutely necessary but you will significantly limit the benefits of Li batteries if you don’t do the others. Why buy an expensive, high performance battery and then handicap it?

The changes I made are:

Replace the stock WFCO 9835 35 amp charger/converter with one that is designed for Li batteries. A Li charger will charge at higher voltage and higher amperage and doesn’t have features designed just for lead acid. The WFCO won't charge the Li battery unless the voltage drops pretty low (see initial post in this thread). So this change is not entirely mandatory, but pretty close. One of the advantages of Li is high-amp charging so you can fully recharge in an hour or two off of shore or generator power instead of many hours for lead acid. I installed a Progressive Dynamics 60 amp lithium charger purchased from Battle Born. The Progressive Dynamics charger/converter charges at 14.6 volts, but the BB Li battery is regulated against overcharge at 14.4 volts, so no problem there. When I charged a 90% full battery with the new charger and wiring, it charged at 55 amps, as designed. Another advantage of the PD charger is that the fan doesn't come on all the time like the WFCO, and when it does, it is really quiet.

Replace the stock 12 gauge charger/converter wiring with 6 gauge so you can charge at up to 60 amps. This is a big deal. If you keep the WFCO 9835 and try to charge a depleted LiFePO4 battery with it, it will charge at close to 35 amps, which far exceeds the ampacity of the 12 gauge wiring supplied with the Snoozy. It is even worse with the Progressive Dynamics 60 amp charger I installed. So you must replace this wiring.

Build a new battery rack. You don't need the big, plastic battery box because the LiFePO4 battery is solid state and not lead acid. That frees up a ton of room and you can easily fit two BB Li batteries between the hot water heater and the hatch door.

Install a 300 amp fuse on the battery because it has the ability to discharge to a short at a much higher rate than the stock AMG battery.

I installed a Victron battery monitor (BMV 700) with dongle so I can keep track of charge level, amp-hours used, and charge/discharge rates. This is not essential but it is really hard to track battery status doing it manually with a multimeter. There is a video on the Battle Born website on how to program the monitor for their battery.

My 4Runner has a factory isolator that keeps the trailer from draining the vehicle starter battery in camp with the engine off. If you don't have that, you will have to install one, or unplug the trailer wiring harness in camp. This is a potential issue with either lead acid or Li batteries, but the next paragraph describes a much better solution to a battery isolator alone, that is needed for the Li battery.

To charge the Li battery while driving, you need to install an isolated DC/DC converter between the tow vehicle and the battery. I use a 7-pin tow connector so that the vehicle will charge the battery and run the Truck Fridge while driving. It is optimum to arrive at camp with a cold fridge and charged battery. The stock trailer AMG battery setup works okay because the vehicle and trailer batteries are both lead acid. But the Li battery has a higher voltage at full charge so it won't charge from the vehicle without a modification. While driving, a fully charged trailer Li battery will actually discharge to the vehicle lead acid battery. To prevent this and charge the trailer Li batteryn instead, the DC/DC converter takes alternator current at, say, 13 volts and bumps it up to 14 volts or so, enough higher to charge the Li battery. Putting the DC/DC converter near the trailer battery also takes care of the voltage drop from the alternator over ~30-40 feet of 12 gauge wire to the trailer battery, which is probably about 1 volt. I got a Victron DC/DC converter (Victron Orion-TR 12/12-9) and set it to charge at 14.2 volts, although it can be set to charge higher. Since it is isolated, it also prevents discharge from the trailer to the tow vehicle. When charging a 90% charged battery it was running at 8.5 amps, plenty for a fast recharge.

Finally, I installed a battery cut-off switch that I can use to isolate the battery for storage or in case of a short somewhere. This is something I would install regardless of battery type.

How has it worked? I didn’t have the DC/DC converter installed when we went camping so we went more than a day without charging on the trip down and camping at WalMart. I used my generator for 30 minutes one day and I vampired off of my neighbor’s generator for 45 minutes the next day. I got plenty of juice and returned home with about 70% charge remaining. We head out for a 5-day trip this weekend and I will report back afterwards.

 


May 22, 2018 at 11:43 AM Flag Quote & Reply

Dan and Liz
Limited Member
Posts: 6
Great post Thanks for the details. What kind of battery master switch did you use and where did you mount it? Can you plug your Snoozy into shore power and charge your battery with the switch off or does the switch need to be on to get power to your charger? Thanks.
May 22, 2018 at 9:42 PM Flag Quote & Reply

Doug Duncan
Member
Posts: 44

Dan and Liz at May 22, 2018 at 9:42 PM

Great post Thanks for the details. What kind of battery master switch did you use and where did you mount it? Can you plug your Snoozy into shore power and charge your battery with the switch off or does the switch need to be on to get power to your charger? Thanks.

Dan and Liz,

I used a Blue Sea 9001e battery selector switch purchased from PKYS in Annapolis, MD, via mail order. I mounted it right above the battery on the bulkhead between the basement and the couch. This is not optimum from an emergency access perspective but I hope to someday do the hinged bed frame modification so will then be able to get to it easily from the cabin. 

I can plug into shore power or the generator to charge. The switch can be wired several ways but I chose to have the battery come in on terminal 1 and the charger into terminal 2. For normal operation I leave the selector at 1+2. I could also select 2 only and remove the battery for servicing. The selector options are OFF, 1, 2, and 1+2. 

You could also wire the charger into the OUTPUT terminal because the charger can be turned off from the master panel anyway. 

I have pictures but have been unable to figure out how to post them here. I can send them to you directly if you want.

Doug

May 23, 2018 at 9:26 PM Flag Quote & Reply

Dan and Liz
Limited Member
Posts: 6
Doug, Thanks again. This is very helpful. I am getting two 6v AGM golf cart batteries mounted in a tongue box at the factory. I may see if Richard can mount the switch inside the tongue box during the factory build. Photos might help but your description is clear.
May 24, 2018 at 11:13 PM Flag Quote & Reply

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