Energy storage - New gen batteries

Hi mena,

I'm not entirely sure of the difference. It may be another way of looking at results of varying loads. It is clear that LI do show far less peukert effect--but that it is still some. Or at least that was my understanding of what I read.

EDIT: I see now. This isn't the same as the Puekert effect. There is a sharp drop off when you reach the end of the discharge curve in LI batts. LI users simply operate their batts outside of that drop off. You don't want to operate the batteries there anyways because you chance killing them, hence the recommendation to keep them at 80% DoD and above.

Hi,

I knew that 0 Peukert was too good to be true.

"Ragone Plot

Lithium and nickel-based batteries are more commonly evaluated by the Ragone plot. Named after David V. Ragone, the Ragone plot looks at the battery’s capacity in Wh and the discharge power in W The big advantage of the Ragone plot over Peukert is the ability to read the runtime in minutes and hours presented on the diagonal lines.

Figure 2 illustrates the Ragone plot of four lithium-ion systems in 18650 cells. The horizontal axis displays energy in watt-hours (Wh) and the vertical axis is power in watts (W). The diagonal lines across the field reveal the length of time the battery cells can deliver energy at given loading conditions. The scale is logarithmic to allow a wide selection of battery sizes. The battery chemistries featured in the chart include lithium-iron phosphate (LFP), lithium-manganese oxide (LMO), and nickel manganese cobalt (NMC). "

From battery runtime

horton333 wrote:
I understand there are in excess of 200 differing battery chemistries that are based on Lithium, but the comments I have read from the engineers are that any can catch, and do, fire. Whenever you have increased energy density this is something that needs to be planned for.

LFP won't catch fire unless under EXTREME overcharging. Something that will never happen with typical RV charging. First, you would have to exceed the batteries charging limits. How many people here have a 1C charger let alone 3-5C? Two, you need to extremely overcharge for hours and hours. People on the DIY EV forums have purposely overcharged their LFP batts and the most that happened was severe bulging of the case. As was stated all lithium ion batt chemistries are NOT the same. The fires you hear are from LiCo batts. LFP is a different beast. If you're afraid, I understand but please don't use your fear to spread ignorance.

The primary cause of over-heating of battery banks is charging at to high a rate. This is not likely to be a problem with solar charging. The figures show that charging up to 0.6C should not be harmful. Not sure how we can charge at a rate of 6 kW with a 1400 W solar panel array.

Electric Vehicle folks may charge to 70% SOC at rates up to 10C.

Reed and Elaine

horton333 wrote:
I understand there are in excess of 200 differing battery chemistries that are based on Lithium, but the comments I have read from the engineers are that any can catch, and do, fire. Whenever you have increased energy density this is something that needs to be planned for.

Spontaneous combustion I understand is pretty rare. Need physical damage or overheat or overcharge the battery. For light use in an RV this should not be an issue.

And of course lead-acid can have it's issues too.

The only problem with higher voltage battery bank is that you now need a converter (Mean Well in our case) to change 48 V to 12 V and there is a few percent inefficiency there.

We always turn off propane when we travel. However, the solar panels operate the fridge on AC while we travel. We are always circumspect concerning propane, tires, brakes etc. Have been this way for quite a while. Was foot recon 48 years ago and we had a saying "Stay a Lurp and stay alive!"

Reed and Elaine

Reed

I agree 100% with going to a higher battery bank voltage if at all possible. However for my current rig I do not see it happening, maybe a future rig but not this one. For the very same reasons you state I went with a PV array of 40Voc and a MPPT controller. It's all about POWER aka Watts higher voltage lower current WAY lower wire losses

Me I'm not worried about batteries starting on fire. Nor am I worried about using my 18 gallon propane tank supplying propane to the frig while driving or the 60 gallons gasoline tank starting on fire. Attention to the details is always required

I understand there are in excess of 200 differing battery chemistries that are based on Lithium, but the comments I have read from the engineers are that any can catch, and do, fire. Whenever you have increased energy density this is something that needs to be planned for.

One other discussion point found on LFP caravan/boating fora is going to 24 V or 48 V battery banks. This allows using much lower amperage and consequent smaller cabling and lower amperage MPPT controllers.
Reed and Elaine