Mike Wendlends lithium batteries

[gerrym51]

http://roadtreking.com/rv-lithium-batteries/

[wincrasher]

Anyone care to explain what this 20k watts equates to in AH @ 12 volts?

[markopolo]

Battery capacity simply isn't expressed in watts. It has no meaning.

You can use watt-hours to express battery capacity but you need to know the amp hour rating used and the voltage.

Look at the ratings here:
http://www.trojanbattery.com/products/deep-cycle-agm-2/

Batteries typically have three ratings: 5-Hr Rate,20-Hr Rate & 100-Hr Rate
Take the Trojan 31-AGM:
5-Hr Rate: 82 Ah (16.4 amps delivered per hour for 5 hours)
20-Hr Rate: 100 Ah (5 amps delivered per hour for 20 hours)
100-Hr Rate: 111 Ah (1.11 amps delivered per hour for 100 hours)

You can convert that to watt-hours:
using 5-Hr Rate: 82 Ah x 12 volts = 984 watt-hours
using 20-Hr Rate: 100 Ah x 12 volts = 1,200 watt-hours
using 100-Hr Rate: 111 Ah x 12 volts = 1,332 watt-hours

Do you see how much it varies? Which do you choose? Those are all at low current draws too, not air conditioner or microwave oven current usage for sure.

Generators are rated in watts.
Inverters are rated in watts.
Batteries are not rated in watts.

[gerrym51]

although i think lithium is the best i have come to like the middle ground of the 'next generation' agm the tpplagm.


tpplagm will satisfy my needs.

[markopolo]

Ok, I see Roadtrek lists the battery capacity in watts for the units advertised on their website. Battery capacity isn't measured in watts.

But, we might be able to decode what Mike meant by 20,000 watts battery.

I think the E-trek has 8 x 200 Ah 6 volt batteries (advertised at 9,600 W on their website today)



9,600 W divided by 6 volts = 1600 A
8 x 200 Ah = 1600 Ah

They might be mixing up amps and amp hours and watts and watt hours .................

It would appear that, in his new rig, Mike has approximately double the 800 Ah at 12v battery capacity that he had in his E-trek (if the advertising is consistent).

This is just a guess - I don't know for sure as I don't have enough information. Someone could ask Roadtrek and report back ...................................

[gerrym51]

someone could-but it won't be me-they are sick of me. However the only way we can measure battery power is really 12 volts.

so 20000 watts is 1666 12 volt amps. a goodly amount and the only number that matters. you can also draw easily 70-80 percent of it in a lithium battery-combined with his 650 watts in solar panels-he will never have to return to civilization

[markopolo]

One question that needs to answered is how does the LifepO4 battery Ah rating compare to a lead-acid battery Ah rating?

I've read that you could go with 1/2 the lead-acid rating required if the LifepO4 battery is constructed using using Phostec premium powder for example.

I'll find and bump up the LifepO4 topic and post the question there.

[booster]

As Marko said, the watts, and by calculation to amps tell nothing about battery capacity and off grid time capability. If the 1666 amps will only run for 5 minutes, it would be pretty low battery capacity if it will run there for 3 hours, then you have something to talk about. They need to put a time with the watts or amps, which would normally be amp hours or watt hours, to give battery capacity.

[gerrym51]

the only way to judge amps to others is amps -12 volt. we already know what devices are being used(sort of). air conditioner of some kind( any one of usual suspects in the area of 100 amps(DC). heater is the Alde sytem(propane-can also use electricty). inducction cook top (1800 watts). microwave convection /oven.

the easiest way is to take whatever vehicle you have-combine it with an inverter powered AC. and figure out how much per day you need.


the power system may be unique but the devices it's powering are not

[booster]

The 9600 watts listed for an etrek, would make sense as being watt-hours at 12 volts. The etreks were said to have 1600 amp hours of 6 volts, so that would be 800 amp hours at 12v or 9600 watt hours. If that is correct, as Marlo says, Wendlund has a lot of battery capacity.

[Davydd]

I posted my guess as to what Roadtrek is doing in Marko's LiFePO4 Battery thread just now.

They seem to be fast and loose with numbers such as the cycles reported up to 5,000 for lithium ion batteries. The only report I know of that says that in an RV comes from Advanced RV's actual testing. Everywhere else I have read has used the 2,000 cycles as a general number.

As far as individual cell blocks put together vs. discreet batteries there has been a few years of this by sailors (boats) and Technomadia (for RVs) that we know about. Hate to spoil the fun but Advanced RV has already shipped lithium ion technology in their Class Bs. I'll take delivery of one next month myself.

[gerrym51]

Originally Posted by Davydd

I posted my guess as to what Roadtrek is doing in Marko's LiFePO4 Battery thread just now.

They seem to be fast and loose with numbers such as the cycles reported up to 5,000 for lithium ion batteries. The only report I know of that says that in an RV comes from Advanced RV's actual testing. Everywhere else I have read has used the 2,000 cycles as a general number.

As far as individual cell blocks put together vs. discreet batteries there has been a few years of this by sailors (boats) and Technomadia (for RVs) that we know about. Hate to spoil the fun but Advanced RV has already shipped lithium ion technology in their Class Bs. I'll take delivery of one next month myself.

most of this cyle stuff for tlithium is based on estimated guesses. at one total draw down a day thats more than 13 years. real life use has never been tested -not around long enough

[markopolo]

Carolann's E-Trek might have been the first (or one of the first) Roadtrek with lithium batteries.
Link: http://www.sprinter-source.com/forum...7&postcount=27

[Davydd]

Originally Posted by markopolo

Carolann's E-Trek might have been the first (or one of the first) Roadtrek with lithium batteries.
Link: http://www.sprinter-source.com/forum...7&postcount=27

I remember that one. Did anyone figure out how all that worked? What I was referring to was instead of discreet batteries that in theory are batteries that look the same as the lead acid and drop in as substitutes, a new generation of technology such as Roadtrek just announced. I'm not sure how long but Advanced RV was doing the discreet battery systems with the Smart Battery. The Roadtrek Etreknology and the Advanced RV ecOasis systems are lithium ion assemblies from individual 3.2v cells with sophisticated BMS. Roadtrek has a couple on the road testing with Campskunk and Mike Wendland of which I am assuming that's what they are doing. Advanced RV has already gone through that phase and is building and delivering them now.

[Davydd]

Originally Posted by gerrym51

most of this cyle stuff for tlithium is based on estimated guesses. at one total draw down a day thats more than 13 years. real life use has never been tested -not around long enough

LiFePO4 batteries came on in 1999. So true they haven't been around. There evidently has been simulated testing (don't ask me how as I don't know) but the industry had pretty much settled on a 2,000 cycle figure which is considerably greater than AGMs' 500 cycles as a recognized limit. Advanced RV is the only source I know of that has tested and determined with their systems they feel confident of 5,000 cycles, at least in the RV industry. Wendland's blog picked up on that without any attribution and claiming it for Roadtrek's system. Question? Do they even know what Advanced RV is doing in coming up with that? You are right about one thing. It is a ridiculously high number representing 13 years of full timing. It will never happen. But even if 2,000 cycles is accurate the LiFePO4 batteries will outlast my ownership. I cannot make that claim with AGMs with any hope or confidence from direct experience. So, I am willing to try LiFePO4 batteries.

[Arlo]

As a 2013 E-trek owner (who rarely uses AC) the thing that strikes me about this is that 800 amp hrs at 12 volts is rarely a binding constraint on my electrical power use. Water and holding tanks are the constraint for dry camping, usually before I come close to 50% state of charge. From a marginal cost - marginal benefit perspective, balance is the key.

[Davydd]

Originally Posted by Arlo

As a 2013 E-trek owner (who rarely uses AC) the thing that strikes me about this is that 800 amp hrs at 12 volts is rarely a binding constraint on my electrical power use. Water and holding tanks are the constraint for dry camping, usually before I come close to 50% state of charge. From a marginal cost - marginal benefit perspective, balance is the key.

Arlo,

Have you tried testing the limits of how much air conditioning you can get off your batteries?

I am getting an 800 ah battery lithium ion battery system and went through an analysis where I first settled on 400 ah as enough then later changed my mind and went with 600 ah. Then finally just went all in because that was the maximum Advanced RV was offering and I didn't want to leave anything on the table. This was my analysis when I settled for 600 ah. We will take ownership next month and will see. I think you just expressed what my gut feels. Besides, I can't sit still in a campground more than a couple of days.

viewtopic.php?p=22144#p22144

[Arlo]

Davydd,

I have never tested the limits of my E-trek batteries running the AC. Guess I don't care or I would have done it! An acquaintance with a CS Adventurous with full E-trek package told me (if my memory is correct) that he got 5.5 hours max of AC. My main use of AC is similar to yours - maybe a couple hours max to keep the dog comfy while we dine or are in a visitor center. We rarely stay put more than a couple days without driving somewhere, so I tend to not even plug in when the opportunity is there. Our use of a B van is very similar to yours so I'm following your posts on Alvar with great interest.

[Davydd]

The 5.5 hours seems about right. A dealer in Minnesota said it was tested but deliberately wide open to run constantly and they got 4.5 hours or thereabouts. We have never run an air conditioner that long even with shore power and certainly would not want to be in a position to have to.

Roadtrek is shooting for 24/7 battery air conditioning. Looking at what they are doing with 20,000 watts of battery as they bill it would mean 1,667 ah? Add solar contribution? We are hedging here with the numbers and of course if you run your air conditioner in Alaska it might be a no-brainer to achieve. That might mean something like an 85 ah 12v air conditioner manipulating the criteria. They exist I've been told and will give you the BTUs you might need. Start searching.

It would be kind of cool to say you went to Burning Man in the Nevada desert in August and enjoyed full comfort for 5 days.

[Arlo]

I like the Burning Man battery test idea. Camp Skunk? Mike W.? Are you out there? Think of what a great podcast that would make.