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FWC Electrical basics and upgrading to lithium!

lithium camper electrical batteries charging

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#1 pawleyk

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Posted 19 January 2022 - 06:56 PM

FWC Lithium Manifesto

 

Ok, lately especially, my inbox has exploded with questions about DIY installation of lithium batteries into Four Wheel Campers. We’re talking 5 new inquiries a day. There is a lot of info about it on here already, but I thought maybe it would be helpful if I put it all into one, centrally located place from a more or less reliable source..

This is going to be long, but I think I’ll cover everything you could ever want or need to know about the charging system in your four wheel camper, and how it relates to lithium batteries.

First: Why lithium over AGM?

Well, honestly, it depends.

  1. Full depth of discharge. You can only really pull 40-50% of the rated amp hours from lead batteries and expect them to live more than a year or so. Lithium batteries are rated for 100% Depth of discharge. This means that a dual 6v setup of AGM batteries is rated for about 224ah. BUT, you can only use just under half of that which makes them effectively 110ah of usable power when they’re new. A SINGLE 100ah Battleborn will have the same effective capacity as two 6v GC2 AGM’s and more capacity than the 2x 12v AGM batteries commonly installed into FWC. IF YOU CURRENTLY HAVE 2x AGM BATTERIES… YOU’LL ONLY NEED A SINGLE 100AH LITHIUM TO MATCH OR EXCEED THEIR CAPACITY
  2. Weight and space savings. As stated above, you need FEWER batteries to make the same power from lithium when compared to lead options. Not only do you need fewer, but the lithium batteries are MUCH lighter. A single battleborn 100ah weighs about 27lbs. A set of GC2 AGMs weighs about 120lbs. For some rigs, the weight savings of 90lbs isn’t a big deal. For some, it is.. *cough* tacomas *cough*
  3. Life span. Like I said before, you can expect your AGM batteries to last about 5 years.. IF you take good care of them. If you aren’t one to babysit your voltage and keep track of your energy use/charging, you’re looking at more like 1-2years between sets. At $600 for a set of GC2 6v batteries, that’s not cheap. A good lithium battery is warrantied to last 10. I’d expect them to actually last much longer in low-draw use like most of us have in our campers. Yes, the batteries are $800, but it doesn’t take many replacements to make up for the cost difference.
  4. Yes.. they also can be charged/discharged faster. Whoopee. In the context of a FWC system, again with low draw, and low-ish rate charge sources, this isn’t much of a benefit really, but it does exist in theory.
  5. But what about cold!?!?!?! A battleborn, as well as most other quality lithium batteries with internal BMS units will not charge below 27 deg F or so. Charging below that temperature WILL damage them, but, the BMS prevents this. So, if your battery is below 27deg internal temp.. it will simply not charge until internal temperature increases. IT WILL DISCHARGE, meaning your lights, pump, and HEATER will still work just fine. Which brings me to another point on this. FWC batteries are installed INSIDE. I use my camper all year long, including for ski and snowshoe trips. I run the heater. That’s WHY I have a camper. When I’m actively using the unit, it is NEVER below 27 deg inside. I also leave water in it all year round. If you are a sadist and like being super damn cold in your camper, there are many options for both internally heated batteries, as well as heating pads to warm them to a reasonable temperature and allow charging.

If you aren’t weight conscious and are a conservative power user who doesn’t mind keeping an eye on voltage.. honestly, your 2x 6v batteries are probably fine. If they’re working for you, keep on keeping on. Definitely don’t swap out a good set of batteries just because. Tacoma people: Swap out the 6v for a single lithium and you can bring either: 1x large dog, or a multitude of smaller dogs. Or several more cases of beer. Whatever you prefer.

Now for the real meat and potatoes. Charging.

First.. most lithium batteries on the market like an absorption charge of 14.4-14.6v or so to get to 100% full. If your charger isn’t capable of putting out voltage that high, it will not charge the batteries all the way.

Your FWC (and MOST vans/trucks/adventuremobiles) have two to three charging sources. The sources are:

Shore power, engine power (alternator), Solar. We’ll take each one in turn.

  1. Shore Power- When you’re plugged into an external AC source, like at a campground or an outlet into your garage, the IOTA AC to DC battery charger inside your camper takes the 110v alternating current and turns it into 12v DC power, then sends it to your batteries to provide a charge. Older IOTA chargers have an option to plug in an external module to adjust it’s parameters to better charge lithium batteries, newer ones do not. In my experience, the IOTA charger is typically not able to charge a battleborn battery more than 80-90%. Will this hurt the battery? Well, technically, yes. If used this way long term with no other charging sources, you could see a drop in battery life since it’s not being fully cycled. So, technically YES, but effectively.. NO. Almost NO FWC users plug in on a regular basis. Even if you do plug in regularly, you also more than likely have a second or third charge source that IS capable of charging the battery fully, so the IOTA really becomes a non-issue. So maybe it can only charge 80%. No big deal, solar or the alternator (through a DCDC charger) can take care of the rest, and realistically will be your main charge sources anyway.
  2.  Engine Power- The factory setup from FWC is through 10awg wire a 30 amp self-resetting circuit breaker, and an Atwood trolling motor plug. The 10awg wire is connected to the starting battery under the hood, and connected to the house, or camper, battery through those components. You wouldn’t want your fancy Isotherm fridge or your furnace to drain the truck battery and prevent you from staring the engine in the morning, however, so the two batteries are ‘isolated’ by a Blue Sea ACR (automatic charge relay) or a similarly functioning SurePower charge relay in older models. These work by connecting the two systems together through a large internal switch when the relay senses a higher than expected resting voltage, indicating the truck is running. When the truck is turned off, the voltage drops, and the relay disconnects, effectively isolating the two battery systems from each other and protecting the truck from excessive discharge (from the camper, leave your headlights on and she still ain’t gonna start). Now, most alternators never put out a high enough voltage to completely charge ANY deep cycle battery, lead acid or lithium. Typically, this isn’t a problem assuming you have solar to supplement. What IS a problem, is the tiny 10awg wire between the two batteries. It’s simply not large enough to carry the current that either a single lithium OR a dual 12v/dual 6v bank would really like. We typically only see 6-9 DC amps of charging through the factory setup. Imagine trying to suck a chunk of strawberry through your milkshake straw. Simply upgrading the wire and retaining the Blue Sea ACR, even with dual 6v systems, we see 25-45 amps of charging. That’s a huge difference and makes for huge drops in driving time to full (or almost full) charge.

So, small wire bad. Not enough amps for effective charging. Doesn’t matter what type of battery you currently have. Another issue, for lithium, is that the factory ACR won’t disconnect the battery banks when the engine is off, since the lithium battery will rest at a higher average voltage than the original AGM batteries. At first this seems bad.. like it’ll keep them connected and allow the house system to drain the truck batteries, but nope. Once the house system, even the lithium batteries, are low-ish the ACR WILL disconnect and isolate the two, saving you from an early morning no-start.

 

There is another issue, however. Many newer vehicles have “smart” alternators. The higher resting voltage of the lithium can also play havoc with these fancy new alts. My 2017 GMC, for example, when connected directly to the lithium bank in my Grandby, would detect the higher voltage and assume the truck battery was perfectly charged, effectively shutting down the alternator. I would have periods where the power would actually run BACKWARDS. I would see a large draw out of my camper battery, going TO the truck. My house battery was essentially powering my GMCs systems, fuel injection, ignition, etc. Not really ideal.

 

We’ve identified three issues with the factory truck-camper system and a fancy new lithium battery: ineffective charging rate, inability to charge fully, AND weird undesirable issues with smart alternators. Another aside here: people will tell you that the lithium battery will accept TOO MUCH charge and will fry your alternator. This is technically true, but a standard single battery will never really draw enough over a long enough period of time to have that be an issue. Regardless, the solution to the preceding three issues will also eliminate concerns of alternator-killing overdraw.

 

DCDC Charger! A DCDC charger takes the voltage from the truck and turns it into the voltage/amperage it thinks the camper battery will need, a good one is programmable and can be setup to perfectly charge whatever battery you’ve got, including your new lithium. It’s also a CHARGER, not a relay, so it will only charge the battery at it’s rated capacity, for the Victron we use, that’s 30 amps. It won’t ever pull too much power from your truck’s alternator, it’ll always charge the camper battery to 100% (given enough runtime, about 3hrs from empty for a 100ah battery) AND it completely separates the systems so you’ll never find the camper battery has drained your truck battery overnight (or ever).

 

And the final piece of the puzzle: SOLAR! The overland solar setup is more than capable of charging your new lithium battery without issues, assuming you reprogram it for the 14.4v absorption charge. Yep, that’s it. Nothing else. Just push some buttons and go camping. No wire upgrades, no extra panels, nothing. You CAN chuck more panels (or a larger panel) up there, but that’s just to increase charge capacity. It really has nothing to do, specifically, with the lithium battery itself. An extra, or larger, panel would also help out your dual 6v. As an aside, the 160w panel is just barely adequate to keep up with the isotherm. We won’t even bother to install anything smaller than a 210w panel.

 

Battery Monitor: There is one final piece of the puzzle though: Keeping track of that new battery and it’s state of charge. Honestly, monitoring an AGM with a voltmeter is pretty darn effective. Keep it above 12.2v and it will last a good long time. Lithium though, doesn’t have a linear voltage drop profile, so simply monitoring voltage isn’t a great way to discern state of charge or ‘SOC’. A battery monitor with a true negative line shunt is the way to do that. It’ll effectively count amps in and amps out, and let you know exactly how much battery you have remaining, all rolled into a nice percentage readout. It’ll also let you know exactly how much power you’re using in the moment (and historically) and how well your chargers are working.  We require them in any install we do, simply because they ask so many questions and really help shine a light on what’s going on with a power system.

 

In conclusion. What do I need to do to use a lithium battery in my FWC? Well, really, nothing. You CAN just chuck one in there. If you have the newer MPPT (overland solar) controller, you’ll probably even be able to fully charge it a lot of the time.

If you really want to get the most out of your investment though, you should definitely install at the very least, a battery monitor.

After that, a DCDC charger. While you’re at it with the DCDC though, please upgrade that tiny wiring from the alternator back to the camper. Otherwise you’ll never get the full use of the DCDC. You’ll be limited to about 15-20% of it’s capacity.

Do you NEED lithium? Probably not. But it is pretty rad.

 

 

 


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#2 Jon R

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Posted 19 January 2022 - 08:45 PM

A couple of comments based on my recent project:

6 awg wire from the truck battery to the camper battery is adequate for a Victron Orion 30 amp dc to dc charger without excessive voltage loss causing the charger’s engine running detection test to cycle. My truck is a cclb with the camper battery at the back corner, so it’s about the longest wire run anyone would have. 6awg is the largest wire the Orion connectors will accept. Nothing wrong with bigger wire, but you don’t need it for a 30 amp charger and it complicates connections.

The Iota dsl 30 in my 2021 Grandby applies up to 14.8 volts in bulk charging, which exceeds the battery manufacturer’s recommended maximum charging voltage. I would only use it in a pinch for an emergency partial charge while monitoring it. I have never had to use it. When I rarely connect to shore power, I shut off my battery switch and the Iota serves as a simple power converter to run the 12 volt system.

The $20 Temco hammer crimper works well, and with the right crimp connectors, wire, and shrink tube you can make excellent cables. Fancier crimpers are nice, but the hammer crimper used properly is adequate.

100ah of lithium is probably adequate for many FWC users, but 200ah means the typical user would never need to worry about having enough battery, and is worth considering. Battleborn batteries are kind of the standard, but if space is an issue other very good batteries are available with different form factors. My 200 ah battery, for example, is 10.25Lx7.5Wx13.1H, and fit in my Grandby battery compartment with both Victron chargers and lots of remaining room.
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#3 pawleyk

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Posted 19 January 2022 - 09:16 PM

A couple of comments based on my recent project:

6 awg wire from the truck battery to the camper battery is adequate for a Victron Orion 30 amp dc to dc charger without excessive voltage loss causing the charger’s engine running detection test to cycle. My truck is a cclb with the camper battery at the back corner, so it’s about the longest wire run anyone would have. 6awg is the largest wire the Orion connectors will accept. Nothing wrong with bigger wire, but you don’t need it for a 30 amp charger and it complicates connections.

The Iota dsl 30 in my 2021 Grandby applies up to 14.8 volts in bulk charging, which exceeds the battery manufacturer’s recommended maximum charging voltage. I would only use it in a pinch for an emergency partial charge while monitoring it. I have never had to use it. When I rarely connect to shore power, I shut off my battery switch and the Iota serves as a simple power converter to run the 12 volt system.

The $20 Temco hammer crimper works well, and with the right crimp connectors, wire, and shrink tube you can make excellent cables. Fancier crimpers are nice, but the hammer crimper used properly is adequate.

100ah of lithium is probably adequate for many FWC users, but 200ah means the typical user would never need to worry about having enough battery, and is worth considering. Battleborn batteries are kind of the standard, but if space is an issue other very good batteries are available with different form factors. My 200 ah battery, for example, is 10.25Lx7.5Wx13.1H, and fit in my Grandby battery compartment with both Victron chargers and lots of remaining room.

 

Have you actively observed the DLS-30 output that high of a voltage? They're only rated to 13.6 or so, and a HIGHER voltage in BULK is entirely backwards for correct battery charging. We've seen literally hundreds of the DLS-30s and I've NEVER, EVER, seen a voltage output from one anywhere near that high. Including in my personal setup. 

 

We use 4awg because it allows us to standardize across installs. Can you use 6awg? Sure, but we typically work with a higher margin than that. Connections are no issue using the correct ferrules. We also use SB120 plugs, so no issues there either. 

 

I see many people that think they must replace their two AGM batteries with two lithium batteries. I just wanted to make sure and clarify how the usable capacities compare, so people don't feel like making that sort of investment is necessary. A VAST majority of FWC and other simple, small rig folks are fine with 2x 6v AGMs, and are just as fine with 100ah of lithium. Is two better? Sure, but most will never really use it assuming the charging sources are setup correctly. I just don't believe in convincing people to light cash on fire. Better served for beer and tacos.

 

KP


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#4 craig333

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Posted 19 January 2022 - 09:36 PM

Thanks KP. Though I'd disagree about the lifespan of a properly charged agm battery. I'd also argue the need for a dc/dc charger if you have solar unless you're one of those crazies who camp where the sun doesn't shine :)


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#5 BBZ

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Posted 19 January 2022 - 09:42 PM

Good info.. 

 

I recently upgraded my battery to lithium (renogy had a killer sale).. I wanted the extra space for storage so replace 2 AGM for one 100ah Lithium (so I thought)... Renogy ended up shipping me a 200ah (for $479) instead and it fits in the battery box so I kept it.. also have the inverter in there.. 

 

About to head to Baja for awhile and really get to see how everything works out. I chose to keep it simple and not replace anything but the battery and use the GEL mode as suggested by others.. Will see how it all goes..


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#6 Vic Harder

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Posted 19 January 2022 - 09:45 PM

Nice summary KP.  I agree with almost everything said here, except that a voltmeter is good enough for monitoring AGM batteries.  Given that most people don't/can't rest their batteries while using their campers, the 12.2v (=50% SOC at rest) for AGM batteries is tough to use.  A shunt based SOC battery monitor is always a good idea.


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#7 Jon R

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Posted 19 January 2022 - 10:12 PM

Hi KP,

Yes I’ve observed 14.8 volts. I started a thread about it in the electrical forum on 8/18/21 when i first observed it. It’s repeatable, and it’s to be expected in certain situations based on its design for charging lead acid batteries. Its maximum voltage rating in bulk charging is 14.8 volts. When it first is given 120 vac, if it detects a battery connected, it goes into bulk mode regardless of the charge state of your battery and ramps up voltage in an attempt to force 30 amps to flow, up to the maximum charging voltage limit of 14.8 volts. If you turn it on with a lithium battery in a fairly high charge state, it happily cranks the voltage right up to 14.8 within several seconds. I’ve watched it with my BMV and a voltmeter.

I was referring to the connections to the Victron equipment being max 6awg. 6 awg is already overkill for 30 amps from a wire heating standpoint. Since what we are doing with the large wire in the installation of a 30 amp dc to dc charger is reducing voltage loss to avoid any undesirable charger behavior, margin above the needed gage for that doesn’t really give a benefit. With the Orion the behavior I wanted to avoid was tripping the test for engine running, cycling the charging off and back on every two minutes. I agree in an unregulated (really wire regulated) lead acid charging situation the approach is different. And I have no criticism for anyone who likes margin in electrical design.

I agree 100 ah is going to be enough for many people. I live in Western Washington and a good portion of my camping is in the trees and/or in overcast conditions, so my solar system often is not much benefit. If I want to stay in one location without running my truck for a 3 day weekend in such conditions, 100ah looked to be cutting it close, so I went with 200ah. I couldn’t fit two Battleborn batteries in my compartment neatly, so i didn’t want to do the try it with one and see approach. If i decided i wanted 200ah, i was going to need a different form factor battery, so i just decided to do 200ah and I’m happy with never worrying about it. Most trips the battery never goes below 60%, confirming your advice that 100ah is probably plenty for most.

Edited by Jon R, 19 January 2022 - 10:13 PM.

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#8 craig333

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Posted 20 January 2022 - 01:20 AM

Just plugged mine in. With an S.O.C. of 96% it promptly went up to 14.2 volts. That is with the original smart charger module plugged in. I have the agm module but haven't gotten around to plugging it in. Its not really far enough off to bother with especially considering how seldom its used.


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#9 Dirtroadsavant

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Posted 20 January 2022 - 01:46 AM

Thank you to pawleyk and everyone else on this thread—this is super-valuable information shared in totally clear language!


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#10 Wango

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Posted 20 January 2022 - 02:14 AM

Thanks to all, am in the beginning stages of upgrading our electrical.

Pawley K, thanks for taking my call today, and for the estimate. Look forward to further communication with you about this.

w


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