Lithium adoption strategies for older coach

[vsheetz]

Alternator charging of lithium batteries, options:

Checking to see if the alternator draw is actually excessive and voltage is adequate to charge lithium - act or do nothing accordingly. Use your shunt based amp counting battery monitor to do this.

The LiBim is just a timed switch. So many minutes off, so many minutes on. The idea is to reduce the duty cycle. Depending on the actual draw and voltage, it may be a solution. I'm not a fan, ymmv.

A DC to DC charger is likely the best if solution needed. Select the proper size unit for the alternator and provides a proper lithium charge profile.

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My experience with my DP motorhome and 600ah battery bank:

At low SoC the alternator draw is typically 40-45a - not excessive, and reduces as the bank charges. However the voltage is inadequate to bring the bank to a goodly charge level.

So a LiBim would not get the job done.

I've elected to do nothing, as my 1500w of solar typically charges well while traveling. If I do decide to add something, it would likely be a Victron DC to DC charger.

There are many, many, RVs - motorized and towables, that have not needed anything done to protect the alternator...

Imho. Ymmv.

[paul65k]

Yeah... Alternator issues happen with larger battery banks, 400-600Ah and larger. My batteries (Lion Energy) can handle up to 100A per battery of input charge but recommend 50-60A for longevity, and BB has a very similar spec. In a 600A system, for instance, this would mean that up to 300 - 350A charge rate would still keep you within the manufacturer's specs so you can see how a 160A - 200A Alternator can be easily working at 100% with no protection and likely causing premature wear.

I initially had a 200A Alternator with 6 batteries and it didn't last a year after upgrading to the then 600A Battery Bank (now 1000A).

The main benefit of a DC-DC converter is that these devices are truly smart chargers and the best ones can be programmed for the capability of your alternator and the size of your battery bank while intelligently sending as much charge as possible to the batteries while making sure that the alternator does not overwork itself.

We now have 60A of Victron DC-DC chargers that actually produce up to 85-90A at peak but still well within the specs of our current 260A Alternator and the manufacturer specs of 50 - 60A per battery......even when we are running the inverter charger(s) with the generator which can produce an additional 280A even 100A more from the solar panels.

If everything was running at max (440A) it would still be only 44A per battery....... this is how one should look at how much charging capacity and limits to design into your system.

[RoadTrip2084]

I was initially going to forgo the DC-DC converter and just see how much current the batteries pulled from the alternator first but ended up finding the Renogy 60A onsale at a price that made sense so pulled the trigger.

[RoadTrip2084]

Originally Posted by TR4

Looks great Ken! If I had to do it over again, I’d probably skip the cell compression springs. Your supposed to get more cycles, but these batteries will outlast me anyway. Plus you can put them in a smaller box.

I’ve now added heating and fan cooling to my enclosure. The heating has two settings, Hi and Low. Pictures here;
https://www.irv2.com/forums/f112/diy...ll-568880.html

Bill

I ended up putting a layer of sheet neoprene foam between each of the cells and then used a clamp to compress the pack slightly (compressing the foam about 1/3 maybe) before taping them together. Not really sure that the tape won't expand with heat or whatever anyway but figured at least the cells are snug. I'm not overly concerned with the "compression problem".

Haven't read your whole thread just yet, but were you seeing high temps at the batteries, is that why you added the fan cooling?

[TR4]

Originally Posted by RoadTrip2084

Haven't read your whole thread just yet, but were you seeing high temps at the batteries, is that why you added the fan cooling?

Don’t have any real world experience with the batteries yet. I’m not traveling, so I can only monitor the batteries from my house. Because of the large terminal mass, battery temperatures move slowly up or down. They’ve stayed in the mid 50’s.

I don’t think I’ll need the heating and cooling for the traveling I do, but wanted the option if needed.

Bill

[RoadTrip2084]

Thought I should provide an update on how it's going with the new battery so far (after 3.5 months of use, including 37 nights, and nearly 5000 miles traveled).

Basically, everything is working more or less as I'd hoped/intended with no major disasters or outages, etc.

Setup Overview

• Removed the lead-acid 8D house batteries and installed a new self-assembled 280Ah LiFePO4 battery, with 200A Bluetooth-enabled BMS next to the converter/inverter in the service bay (indoors, heated).
• Disconnected the house circuit completely from the chassis batteries. This involved removing the oem battery isolator, chassis battery maintainer, and the "big boy" boost solenoid (used to boost the chassis battery from the house battery) from the rear engine bay electrical panel.
• Kept the oem Freedom Model 20 Inverter/Converter (2000w, 100A 3-stage battery charger, no Lithium charge profile), set it to use its lowest voltage gel battery charge profile (14.1v absorption, 13.8v float, no equalization).
• Installed a 60A Renogy DC-DC charger in the rear electrical panel, between the chassis batteries and the house battery circuits (200A alternator connected to the chassis batteries).
• Rewired the oem 80w solar panel to charge the chassis batteries, instead of the house batteries (keeps the chassis batteries charged will parked).

Pros

• The battery output is amazingly stable, no flickering or dimming of lights when high loads are turned on or off, unlike with the lead acid batteries.
• The battery output amperage is amazing. We can run our microwave or convection oven for 30mins to bake pizzas for dinner without issue. The only thing we don't run off the battery are the rooftop A/C units, and the electric hot water heat (use propane instead).
• The battery charges quickly, easily recharging during a travel day off the 60A DC-DC charger, and even faster (100A) when plugged in or running the generator. One time when travelling we had the generator running to operate the A/Cs and were getting a combined 160A charging from both the DC-DC and converter.
• In normal to warm weather the battery remains at optimal usage temps. generally between 20c and 30c in the service bay, even when it is cooler outside.
• The bluetooth BMS is a must-have for this simple configuration. With it I can monitor charge/discharge cycles/values, set warning notifications for certain events (cell over/under-charge cutoff, high/low temp cutoff, etc.). I am also able to manually disable charging using the app. if I want the battery to remain at say 70% charge because the coach will be parked for a week or two until the next use. I can also completely disable the battery input/output for storage. Without the BMS, I'd need to add a smart shunt, at the least.
• Using the tiny 80A (when it was new, 25 years ago!) solar panel to charge the chassis battery is working really nicely, at least in the peak summer months. I can park the rig, leave the chassis battery disconnect connected, and not worry about the chassis battery dying (of course, I can't leave the headlights on or anything with load).
• With the house battery installed next to the converter in the service bay I am able to repurpose it's tray in the semi-sheltered battery compartment which I now use for storing extra fluids (oil, anti-freeze, etc.) and filters.

Cons / Issues

• When I first configured the Freedom 20 converter/inverter I used a lightly higher voltage charge profile; 14.4v absorption, 13.8v float. This caused a couple of high-temp shutoff events on the BMS itself, reaching 80.6c. It also had a cell high voltage cutoff event. I think the BMS could use improved airflow over its cooler for sure. Lowering the inverter charge voltage profile to 14.1v absorption, 13.8v float has eliminated both of those issued thus far.
• The way the Freedom 20 converter works, when plugged in to shore or generator power, it actually doesn't provide 12v DC power other than via the battery charger. So if I manually turn off the charger, all 12v DC power is supplied from the battery alone. If I charge the battery and leave the charger on, it reduces the 12v DC output from the battery to 0 amps while it is charging, but eventually it lowers or stops charging current enough that the battery is once again providing the bulk of the 12v DC power. This isn't a deal-breaker, but it does mean I need to keep at least a half-open eye on my battery charge level while plugged in for multiple days in a row and eventually initiate the charger to recharge it. I suppose the converter would automatically enter a new charge cycle when the battery voltage got low enough, but I haven't witnessed this occurring yet so am not certain that it would do so before the BMS low-voltage cutoff would kick in.
• Having no boost solenoid means that I have no way to charge the chassis battery from the house battery. The solar panel negates this requirement, at least so far in the summer months. If I ever do flatten the chassis battery by leaving the headlights on or something, I can use jumper cables to provide a boost charge to the chassis to try to recover them before attempting to start as a temporary measure. Or get a boost from another vehicle/toad vehicle.

Overall I'm very pleased with my results thus far. The system is probably slightly more labour intensive in terms of my needing to manage the battery via the BMS app regularily than a complete new install with smart shunts, proper modern LiFePO4 charger, etc. would be (or maybe those would be worse, actually?), but I don't mind it at all and I love the attributes of the LiFeP04 battery (100% charge/discharge, zero physical maintenance, fast charge/discharge, stable output even under load, etc. etc.)

My costs for this project were:

Battery Cells
* 4 x EVE LF280K (3.2V 280Ah) cells (3,360Wh): $566.50 or $0.169/Wh (delivered).
* Flexible Bus Bars: $25
* JBD BMS - 4S 200A Smart BMS (www.lithiumbatterypcb.com): $85
* Plastic battery box: $25
* 300A fuse, misc. wire and lugs, crimper, etc. approx. $125
* 60A Renogy DC-DC Charger: $163

Total Cost: $989.50 USD

Future projects for this winter are to remove the Freedom 20 and rebuild it on my workbench at home, fresh capacitors, reflow any cracked solder joints. These things are built to last and use simple discrete components which are easy to replace. No reason it shouldn't keep working basically forever with a little care and attention now. I'm also going to take my battery out to inspect the cells for any unusual swelling, etc. and to try to figure out an improved cooling situation for the BMS (fan?).

[vito.a]

Ken, thanks for posting the follow up. Sounds like a great system.