Lithium upgrade questions

[stickfigure]

After camping in 2°F (!) weather and flattening the lead acid battery twice by running the furnace continuously, it's time for some upgrades.

My pup is a 1999 Coleman Taos with the Magnatek 6712 converter. The only draws are furnace, CO sensor, lighting (no fridge). Current setup is a 100w panel, cheapo PWM controller, group 24 marine batt. No charge from the TV (4-pin).

I bought a Victron SmartSolar 75/15 MPPT controller and a chinese 100AH LiFePo4 battery with a fancy bluetooth BMS. My plan is to relocate the new battery and the controller inside the pup, probably under the seat next to the converter.

Question #1: Should I put the house system on the "load" of the MPPT controller, or should I wire the converter directly to the battery?

I guess the value of having it on the load terminals of the controller is that (hopefully - I haven't tried it yet) the victron bluetooth connect app might be able to tell me what the draw is in realtime. That would be useful to know. The downside is that it's a single 15 amp circuit? Would charging via the converter work if the converter was tied into the load side of the controller? I don't know if there's a diode in there, the victron manual is unhelpful.

Question #2: Should I replace the converter?

The 6712 apparently just produces a continuous 13.8v. This is less than the 14.4v that the battery BMS wants, but seems better than the multistage lead acid profiles that "modern" converters generate. I guess I could just live with the existing converter and accept slow charging, with the solar array finishing the job?

On the other hand, it would be nice to be able to plug in and get a reasonably fast charge. To replace the converter, what are my options? The 6712 has a low profile and all the replacement converters I see advertised online seem to be twice the height (ie, wouldn't fit under the seat). Ideally I would like to avoid cutting wood.

Looking for any advice, general or specific. I'm decent with a soldering iron and not afraid to rewire everything (there's not much there!) but still pretty new at this.

Thanks,
Jeff

 

[Anthony Hitchings]

we tried putting our load on the controller, but it was too annoying in practice, based on our usage mode

 

[SteveP]

You should verify the load output of the controller is sufficient for your needs, some are limited to 10 amps max. Also, it may default to a timed output, as the load is typically used to turn automatic lights on and off. You should be able to control the programming for the load outputs through the phone app.

Question #2: Should I replace the converter?

IMO you would be better off to spend your money on a good stand alone charger with 15 to 25 amps output. Victron has good models that will cost about the same as a new converter.

 

[stickfigure]

IMO you would be better off to spend your money on a good stand alone charger with 15 to 25 amps output. Victron has good models that will cost about the same as a new converter.

This makes a lot of sense to me, but talk me through it. I assume we're talking about something like this: https://www.victronenergy.com/chargers/blue-smart-ip65-charger

Do I keep the existing converter in place or rip it out?

If keep in place, I assume that I hardwire the charger between one of the 110v legs off the converter and the battery? When on 110, the 14.4v from the charger will be higher than the parallel 13.8v from the converter and will dominate. What does the converter do while this is running, I'm curious? I guess it's the same as when it's plugged in and the solar is active.

If I rip out the converter, what do I use as a bus panel? Sure would be nice to reclaim that space and weight if I'm not using it. Basically I need a distribution panel for the 110 and the 12v. I think there's only 2 circuits of each.

 

[SteveP]

If you don't have a manual for your converter look at http://web.archive.org/web/20200228...tes/8194/2018/09/6700-Series-Owner-Manual.pdf

The easiest way to isolate the battery from the converter is to install a switch, these are pricey but small and easy to install. Off when running off of Shore Power and on when you need to pull from the battery.

The Victron IP65 is my go to battery charger, I have the 14 amp model. I prefer to keep it free standing because I use it for other charging as well. But if you want to hard wire it I see no reason not to. As you said, wire it into the 120 VAC side of the power panel, but if you have room for an additional breaker I would add one so that you don't have the charger running except when you need it. LFP batteries don't require constant charging like LA batteries.

 

[Anthony Hitchings]

we kept our non-lithium converter in the camper, which charges the Li battery to around 95% I think. The Renogy solar system charges the battery to 100% when we are on the road. Its fine for the two chargers to be in prallel.

 

[NMroamer]

Rather than reinvent the wheel. Get a stand alone battery charger and a cheap harbor freight generator.

 

[TSQ]

You will need to heat the LFP battery in order to charge it in freezing temps.

I just kept my loads on the battery. Doesn't the battery Bluetooth BMS tell you current? But no reason you couldn't put your (minimal) loads on the Victron MPPT charger. This would let you set a custom low voltage disconnect IIRC. As for charging see below...

Keep the converter but disable the internal battery charger by removing the feed wire from the AC breaker. Install a Victron IP22 12V 30A charger directly to the battery circuit protection:

You can keep it plug-in, or hardwire it to the breaker that the converter internal charger used to go to.

Use a 50A breaker on the battery, it will double as a disconnect:


You can charge (very) slowly off a four way using a small DC-DC charger, but probably not worth the hassle for you with your minimal load and solar setup.

Throw LED bulbs in your lights if you have not already.

 

[JimmyM]

I upgraded to lithium and also use that same MPPT controller.

#1: Ignore the "Load" connections. Just connect the output to the battery and leave other connections to the battery as they are now.

#2: 13.8 isn't the greatest, but it's a good compromise. Lithium batteries age more quickly when held at high voltage (14.4-14.6V). Small fractures occur in the crystal grains in the cells.
Charging to 13.8V (3.45V/cell) will get you to about 95% SOC.
The internal BMS balancing may not kick in at only 3.45V/cell. But that can typically be adjusted.

 

[JimmyM]

If keep in place, I assume that I hardwire the charger between one of the 110v legs off the converter and the battery? When on 110, the 14.4v from the charger will be higher than the parallel 13.8v from the converter and will dominate. What does the converter do while this is running, I'm curious? I guess it's the same as when it's plugged in and the solar is active.

The 14.4V charger would provide all current to loads until the load is sufficient to pull the 14.4V down to 13.8, then the converter would provide current as well.

I like the Victron IP22 30A charger. But it's pricey for debatable effect.

 

[JimmyM]

FYI
In my system, I removed the existing 35A converter and installed a Powermax PM3-60.
I added a switch to allow me to select 2 different constant voltages. 13.2 and 14.2. It's almost always set to 13.2 when I'm on Shore Power because the battery (460 Ah) doesn't need to be charged. Before a dry camping trip, I switch to 14.2 to fully charge and balance. Then I go camping. If I need to recharge during the trip, I can dump 60A into the battery and not have to run a generator for very long.

A friend is building a system (560Ah) that will use an additional 100A converter set to 14.2-14.4V that will only be used when a full fast charge is needed.

 

[BikeNFish]

Although I do not have lithium on my TT now, I have done many, many hours of exhaustive research on lithium RV batteries and will convert my TT to lithium in the spring because we mostly boondock and dry camp.

Does your new lithium battery have low temperature protection? Without low temperature protection, you put your battery at risk.

As others have inferred, you will damage or destroy the Lithium battery if it does not have low temperature protection. If the battery BMS does not have low temperature protection, then check to see if your Victron has an option for an external battery thermostat and that the Victron will shut down charging when the temperature is below 32°F.

You can discharge a lithium battery below freezing (most down to -4°F) without damaging it. But if you charge a lithium battery when the battery temperature is below freezing, it will be permanently damaged or destroyed. This includes Jackerys or any other lithium portable generators.

Bringing the battery inside the camper will help keep it warm, but then you need to make sure the storage compartment is kept above freezing temperatures.

If your converter is not lithium compatible, then your battery will be charged to a max of around 80%. If you have a solar panel with a controller that is lithium compatible (most are), then the solar panel will top off the battery to 100%. Charging with a non-lithium charger will never get your battery close to 100%. This is bad only if you need to rely on a fully charged battery.

In my research, I have read many manufacturer's posts that say it is recommended to keep a lithium battery charged between 20% to 80% to extend the number of lifetime battery cycles. But this recommendation is only useful if you are in you are camping full time and discharging and charging the battery every day. If you are not charging and discharging every day, you should easily get 10 years out of a lithium battery even if you keep the battery at 100% as long as it is properly maintained.

A lithium battery should not be stored below freezing and should be removed and kept inside in a heated area when not being used.

 

[stickfigure]

Thanks everyone, lots of good advice.

The battery I bought () has low-temp protection. I saw Will Prowse's teardown; this seems to be a newer version of that battery, and someone in the comments tested it and verified the low-temp protection works. $300 for 100AH with low-temp and BT seems to be the new bargain price point.

That said, this pup will live in temperate California weather and only occasionally foray into freezing weather (errr, like last week, and in another couple weeks... why do I do this to myself).

Glad to know I can leave the converter intact. That's the solution I'll take for now, mounting the battery and solar controller under the seat next to the converter. I bought a 120v receptacle to mount under the seat so I can soft-mount a Victron IP65 charger. I probably don't need it with the solar and 13.8v from the converter, but a little extra security in cloudy weather will be nice.

The only annoying part about this build is that I'll have to drill out and replace the pop rivets that hold on the ABS front panel of the pup so that I can mount an input port and run wiring for the solar all the way around two sides of the pup to the controller. Whatever, easy enough.

Long run I'd like to remove the converter and mount all this hardware in the space that the converter currently occupies. But that will have to wait until spring. I'll post pics of the build (which will start when the battery arrives).

 

[Anthony Hitchings]

FWIW - our LiFePo4 battery case was 37.4 deg F inside the Aliner (roof erected) this morning (its parked outside). It has no battery heater (yet)

 

[BikeNFish]

The battery I bought (Ampere Time) has low-temp protection. I saw Will Prowse's teardown; this seems to be a newer version of that battery, and someone in the comments tested it and verified the low-temp protection works.

I also have seen many Will Prowse reviews. He is a great resource. HOBOTECH is another great resource.

I would definitely buy an Ampere Time battery but they don't offer what I'm looking for.

I want two 100AH batteries or a single 200AH battery that fits in my existing double battery case and I need that low temp protection here in Minnesota. Unfortunately, two Ampere Time 100AH batteries don't fit in the battery case and the 200AH battery does not have low temp protection. This seems to be the case with most manufacturers.

Low temp protections isn't needed for our Minnesota summer camping season, but it is definitely needed in in early spring (March, April) and late fall (October, November) when the temps regularly drop below freezing at night.

 

[stickfigure]

Weird, popupportal must have screwed up when auto-editing my post to add their amazon affilite codes. I bought the Vestwoods battery, not Ampere Time. AFAICT the 100AH AT battery doesn't have bluetooth or cold temp cutoff. My impression from going through old youtube videos is that every six months these things come down in price and go up in features. I'm just glad I don't have to wait for aliexpress to ship it over on a boat.

 

[SteveP]

If you ordered the Vestwoods return the AT for the correct battery.