Interesting battery analysis

I just watched that video. I like Morton's videos in general because he is well grounded in his electrical engineering. And I agree with the overall conclusion, which is that Li batteries are more cost effective than PbA's one a life cycle basis, and also that expensive AGM's are not cost effective relative to deep cycle flooded golf cart batteries. Finally, I agree that self heating Li batteries are a waste of energy, much better to keep them in a space that is already heated anyway, or at the very least to insulate them well.

So, here are the areas where I disagree.

First, saying that PbA's can't be used for energy storage systems because if their temperature sensitivity is silly Of course they can, what does the think has been used for off grid energy storage for a century now?

Second, he is shilling for Battle Born which is probably the most expensive Li battery alternative available. There is no test alternative with a more cost effective Li battery presented, the implication being that Battle Born is representative of all Li batteries. It is not and Morton is well aware of that. In fact, his first Li RV installation used salvage Tesla Li batteries, which are far less expensive than Battleborne is. At some point he picked up Battle Born as a sponsor and the bias shows.

Third, proposing to use energy production rather than amp hours as the metric for battery comparisons is really only valid for inverter loads. For direct DC loads (like fans, lights, furnace fans, and water pumps IOW most of our DC amconsumption) amp hours is a better metric. Why? Because they either run or they don't. No one cares if the fan runs a little slower because the voltage is lower, it's doing its job, and in fact using less amp hours at the lower voltage provided by the PbA battery, thereby saving energy. It's annoying when someone proposes using a metric simply because that makes one technology look better than another.

4th, measuring capacity to 12.2V under cold or high discharage conditions is unfair to the PbA battery. I loved it when the Battle Born guy said that they were just using the PbA manufacturers' one specs against them. Dead giveaway that someone is playing soecsmanship games.

In reality the Peukert effect and temp dependence while valid is not taking into account that both PbA and Li batteries have a coulombic efficiency of nearly 100% (not counting losses durung float or equalization after the battery reaches full charge).. Meaning that you can get all the amp hours out that you put in. You just need to take them out slower or set a lower ending voltage if it's cold and/or you have a higher discharge rate.

You can model a battery (either type) as a voltage source in series with a resistor, the resistance of which gets higher at with lower temps. So if you run at a high discharge rate and then go to a low discharge rate you will get the essentially the same capacity in amp hours out of the battery as if you ran at the low discharge rate the whole time. Ditto with discharging at a cold temp and then warming the battery up, the capacity is still there. It's not like the coulombs of charge stored in the battery plates magically disappear when it gets cold and/or the discharge rate increases, it's just that it's harder to get out and you have to set the end voltage lower to get it. That doesn't harm the battery plates because you are not changing how many coulombs you are removing.

Solar charge controller designers, myself included, have know this for decades, the good ones can be set to change their end voltage (and float voltage) based on battery temp and discharge (and charge) rates.


5th. Morton does not mention the cost of changing out charging electronics when looking at the economics if converting to Li batteries. That significantly changes the decision making process, as new shore power chargers, DC to DC converters of alternator charging, and potentially new solar charge controllers, can easily cost more than the batteries themselves do.

6th. PbA batteries are generally acknowledged to require initial formatting in order to reach full capacity while Li batteries are not. It's not clear from what I saw that this was done with the PbA's in the experiment Morton did but it could explain at least part of the low capacities measured in the test.

Morton did his first Li conversion to have much more capacity without increasing weight, and in my opinion that remains the most compelling reason to stop using PbA batteries. If you don't need high capacity and are ok with the weight of PbA batteries, then inexpensive flooded golf cart batteries remain the best option for most folks. And if you want to make the switch then there are much cheaper alternative than Battle Born.

Agreed, you were an ideal candidate for the Li conversion.

I would also mention that an expectation of keeping your rpod long term is key as well. If you don't plan to keep it at least another few years then it's not a great idea to invest in Li batteries, the average buyer wont understand and/or need the benefits so won't be willing to pay you extra for them. That's why I didn't convert, I was not planning to keep the rpod long enough. Also my objective would have been to be able to run an a/c overnight during campground quiet hours, which would have required at least 5 kwh capacity and a change to 24Vdc and a a minisplit for efficiency. A high
time and cost conversion for sure.

Some higher end trailers are now offered with Li battery systems from the factory. As that becomes more common the economics will change, if you don't have to change out all the charging systems there isn't a good reason not to go with Li from the beginning. The ev manufacturers are now sourcing Li batteries for around $100 per kWh so they will soon be on par with all but the cheapest PbA's in initial cost.

Good idea, your electrical system is likely to outlive the trailer itself.

Okay. A lot depends on what model converter is installed. Check your manual to see whether there is a switch to enable you to set it for proper charging of the LiFePO4 battery. Since it is 2021, it is more likely than it was with our 2016. As for solar panels, the charge controller is the key there. The panel just produces electricity. The charge controller applies it. I chose a Renogy system that was negative ground to match the negative ground of the RPod. I saw that some panels were available with positive ground. Offgrid would need to answer but as for me, I avoided the positive ground models.

Is your RPod equipped with solar or just solar ready? If it is the second one, then the wiring is in place, but things like solar panels and charge controllers are not. Since I have no idea about 2021 models, I really can't help you much.