A different lithium battery heater setup

[wincrasher]

Well that's basically Davydd's argument isn't it? The bigger the pack, the more worry free and more capable off-grid you are. The less need for monitoring or tinkering. Or the possibility of ever going "cold".

If you are already $20k in for the tech, why not go all the way for an extra $5k? At a certain point, you might as well just get everything.

[gregmchugh]

My point was simply that at some point you are buying battery capacity you may use very rarely. If you want the extra capacity, even if it is rarely used, and you want to spend the money, I am sure ARV or Roadtrek will take your money. The only difference, I expect, is that ARV would discuss it with you to make sure you understood your needs before taking the money.

On the Ecotreks it looks like there will be no 1200 amp hour option, only a jump from 800 to 1600 costing $10,000.

[Davydd]

The only plausible reason for 1600ah is air conditioning, or a belief you can satisfy that need off grid. Sans an air conditioning need it would be a total waste of money. 800ah is enough to live off grid same as being on shore power. 600ah could also do it with the potential of invoking auto start engine idling. 400ah will have you constantly planning your strategies, conserving and using your second alternator idling or driving about just about every day. I doubt you could simulate shore power living off grid with 200ah. I'm basing that on a typical 2-3 day stay in one place with lithium ion using your shore power appliances. I'm also implying a propane free B without an Onan generator since you will not have the space or weight capacity available in a high ah battery set up.

[Davydd]

I should mention auto start engine idling with the second alternator is not an onerous thing. You can charge double the rate of an Onan. The consequences on the MB Diesel engine are not as bad as reported or feared. You don't need to do it just to brew coffee or run your microwave. With high ah battery capacity running it is a rare occurrence anyway. You can run it if you desire to run air conditioning and still net charge your batteries. If you lie in bed in the back of the Sprinter you don't feel or even hear the engine. What you hear on an ARV is a forced air fan cooling the alternator. Current ARVs have eliminated the fan with the abandoning of the Nations alternator for a better alternator (says ARV.)

[mojoman]

More is better in regard to AH of lithium, they will loose capacity with high use and age a few years down the road. 900AH bank is what I calculated will be enough for me, down the road when they loose 20% of their capacity they will still be more than enough.

[gregmchugh]

I wonder how much capacity loss would be needed for replacement under Roadtreks 6 year warranty?

[wincrasher]

I would suppose, the bigger the bank, the less deeply you are depleting them, thus extending their useful life and capacity.

[mojoman]

I was going to build a 720AH pack, 4 more cells gave me 180 more AH and hopefully will delay replacement in the future, at a cost of $960.

[Davydd]

We have rarely depleted our 800ah battery bank below 50% SOC and have set our Autogen to come on arbitrarily at 30%. Of course ARV won't let us go below 20%.

[mojoman]

I came across a review/testing of the cells I'm using. Apparently they hold more AH than what they are rated as. The 180AH rating of my cells is a already factored in for longevity and safety. By reducing the SOC by 20% more you may be cycling the charge system more than needed for paying the price of using this technology. I too will limiting the SOC, but to 90% and adjust to 100% if needed or desired if I go to the desert and run the AC allot during dry camping. Do you have the option of raising the SOC %?

[gregmchugh]

Are the factors that reduce the capacity over time well documented for lithium cells like they are for AGMs. Are they quantified?

[booster]

Originally Posted by gregmchugh

Are the factors that reduce the capacity over time well documented for lithium cells like they are for AGMs. Are they quantified?

The only real information I have seen is for high temperature degradation. That was the 50% loss for every 10*C hotter.

The cycle life based on discharge %, how full %, low end cutoff%, charge voltage, float or not, seem to be all over the place. You have one manufacturer saying fill them all the way, leave them on full voltage, discharge them flat and another saying leave 10% on each end, full cutoff charger, store at 50%, etc.

I would rate it all as undetermined, but trending toward the latter example.

[gregmchugh]

Lifeline uses a 20% loss in capacity for their AGM batteries as the lifetime as I recall, is this a standard that is generally used in other battery specs?

[mojoman]

Yes, there is really no comparison between AGM and lithium batteries other than cost which continue to fall. I predict lead batteries will be history within 5 years. EPA will probably push it sooner depending on which clown is elected next year.

[avanti]

Originally Posted by mojoman

Yes, there is really no comparison between AGM and lithium batteries other than cost which continue to fall. I predict lead batteries will be history within 5 years. EPA will probably push it sooner depending on which clown is elected next year.

Well, I am enthusiastic as well. However, the other advantage of AGM is robustness to various kinds of abuse (mis-charging, temperature, etc). Even at the same price, these considerations will most likely continue to give AGM an edge in certain applications.

[mojoman]

Your car battery will be replaced with something the size of a beer can pretty soon.

[avanti]

Originally Posted by mojoman

Your car battery will be replaced with something the size of a beer can pretty soon.

We'll see...

[booster]

Originally Posted by mojoman

Your car battery will be replaced with something the size of a beer can pretty soon.

Hopefully, they will replace the driver instead, and then we all can ride along and use a real beer can.

[gregmchugh]

You won't find fixed solar systems in off grid appications changing from wet cell lead acid batteries anytime soon, still much cheaper than anything else. Of course, we may have different perspectives on how soon is soon...

[mojoman]

I think its more of getting away from lead for environmental concerns since it so toxic.