Lithium on the Cheap

[booster]

I agree with Marko.

Even with the best of the integrated lithium setups, the technology is relatively untested over time. Even Davydd had some surprises and some tweaking done. I would expect the same will happen with the Roadtrek setups.

To justify the new technology issues and cost, I would want to see some big benefits, like big capacity increases and weight reduction. I would also want to make sure all the cold weather and other issues were adequately addressed, as it would be a bummer to go backwards on convenience.

The 1 to 2 years on an AGM Marko stated might even be a little on the light side, and you could get considerably more depending on your use patterns. It is the number of times you go to the low SOC that counts, and most folks don't go that way all the time, and are at much lower discharge for many of their cycles. You can also considerably reduce the damage caused by deep discharges (at least per Lifeline) by doing the proper recharge procedures for the deep discharge use.

[avanti]

The whole "50%" rule-of-thumb came originally from the off-grid living gang. They have a lot more batteries at stake than we do.

[booster]

I totally agree, and although we will have a lot battery power at 440ah, I would not hesitate to take them to 20% SOC to stay somewhere we liked a little longer, or as was said, keep warm.

I think it you did all the math to see how much money it actually cost you each time you went under 50%, it would be a shock to see how low it is. Almost certainly way under what shore power costs extra, and folks don't hesitate to use shore power to save their batteries.

As said 50% is not a hard fast rule that you need to follow all the time unless you want to.

[wincrasher]

Yeah, I'm not too concerned about making something to last 10 years. I suspect that in a few years time, there would be bigger and better, and you probably upgrade anyways.

If I went with the Smart Battery, I'd expect to drain it down to the useable capacity - the full 108 ah like they claim, just to see if it can be done reliably. So that would be a pretty good upgrade over what I have now. I'd not be running inverters off this I don't think. At least not at first.

The Converter is a simple plug and play replacement. It's dimensionally the same with the same amperage and the same wiring connections. And it's only $200. It has a 3 year warranty.

The Battery is $1299. So all-in it's a $1500 project if you don't have to re-wire the alternator that is. Not too much $ to risk and still in the realm of DIY.

[Davydd]

The temperature issue is trying to apply a charge to a lithium battery that is under 32F. That's when damage will occur. Instantaneously or incremental? I don't know. But a simple solution is when the temperature is near or below freezing simply disconnect the battery so no charge can be added. That is an easy thing to do for long term winter storage if you want an inexpensive system. As for being out and about and having dropping temperatures chances are the batteries will stay above freezing if it is just an overnight temperature drop.

When we initially drove home for four days from Cleveland to Minneapolis with the temperatures all the time day and night below freezing our battery temperature did not drop close to freezing until it sat for a couple of days with little load at home in minus 0F temperatures. I took that to indicate batteries in use stay warmer than the air temperature. South Carolina and further south in the winter? It may not be an issue. Of course you might want to have some way of knowing your battery cell temperatures. Does the Smart Battery have that capability?

Driving lead-acid batteries down below 50% SOC certainly does accelerate aging. I went through an AGM in one season but you can buy a lot of AGM batteries for $1300. Too many times running an absorption refrigerator on 12V and forgetting when stopped or doing so through lunch hours probably did it more than anything. That was one reason I gave up arguing the safety issue and went to running the refrigerator on propane all the time. Also, with one battery you have to get through a night and you cannot always stay above 50%. Lithium systems are being designed with fail-safe in that regard with auto starting engines to recharge. Does anyone do that with lead-acid?

[wincrasher]

There is no indication in the materials that temp monitoring is part of the package. If the casing is sealed, then you probably can't open it without voiding the warranty to install a sensor.

Would a sensor on the terminal post be good enough for monitoring?

Insulating the battery is a double edged sword I suppose. If they develop heat on being charged or discharged, then that would be trapped inside. A location under the van would help in keeping it cool in the summer.

[mojoman]

The lithium battery box I'm building will have 12v seat heater elements. They are inexpensive and easy to install. I probably will never need to use them since they will be mounted inside the coach, but Murphy's law dictates their need. Also installing them on my FW tank.

[Davydd]

Lithiums cannot be taken down to 0 SOC or take an overcharge without fatal consequences. AGMs can and survive though it greatly diminishes life and capacity. That's something to consider too. It all comes down to effective BMS.

[avanti]

The freeze-avoidance issue is hardly rocket science. A thermostatic switch, a relay, a small 12v heating pad and a battery isolator solenoid would be sufficient to fully protect and automate the process. No fancy logic necessary. Not even an Arduino.

IMO, this sort of decentralized "spinal cord reflex" approach to this kind of thing makes much more sense than fancy multifunction controllers.

[markopolo]

I don't really understand the need or desire for autostarting the engine.

You don't want that to happened if you're parked on dry grass in some boondocking location, in your garage, when camped right next to people in tents, in no idle zones, during campground quiet times etc.

Remote car starters are very common here. Press a button - start the car.

Advanced RV's autostart is really cool with the app and ability to program campground quiet times etc. Have you ever needed it?

[avanti]

As far as I can tell, the whole "autostart" thing is about pets. Now, don't ask me to explain that.

[wincrasher]

If you recall, I have the Onan remote installed. For only $500 you get a plug and play unit that will autostart your genset on low voltage (that you can set) as well opt out on quiet times you can program. There is also a sensor to keep it starting if it hasn't been moved in a set amount of day (that keeps it from autostarting in a garage).

I'm not really comfortable having any of that engaged without being in attendance. I make sure it's completely off if I leave the van.

[avanti]

Yeah, our Outback inverter/charger can be programmed to autostart the genset. I never even bothered to hook it up.

[Davydd]

Marko,

I haven't needed it yet other than demoing and testing it but that has always been with the touch screen, app or key fobs. In fact I am doing one more test right now. I unplugged last Sunday to see how long I could go before it would autostart. It was kind of necessary because painters have been at our house all week painting the house and garage and I had to get away from them so they could do their work. Everything is on including the inverter and I am still at 17% which is still 102ah of usable energy (.17 x usable 600ah = 102ah). It might come close to auto starting in the middle of tonight but am guess tomorrow afternoon. So I may turn on the air conditioning to help it along as I would prefer it started today than tomorrow when I might be out and about. So it can go close to 8 days sitting with no cooking, coffee making or TV watching. I could prolong that turning the inverter off and even the wifi off if in the wilderness. I have been in and out of it all week turning lights on and off, started and repositioned the B once in the driveway and I did do about 5 minutes engine running to check decibels yesterday. The sun has been prolonging the time.

Just a recap. Advanced RV programmed a low autostart SOC at 20%. I upped it to 25% leaving 600ah usable out of the 800ah battery pack before autostart would come on. Roadtrek is programming 10% but interestingly Hammill said performance drop off started around 20 something percent.

[booster]

Getting back to the damage that can be done by going 80% down on AGM batteries.

Killing them in a year is probably possible pretty easily, although I think that some brands would be much more prone to die, than others.

But, IMO, the thing that is making the problem way worse than it needs to be is the quality of chargers, and all the undercharging that is happening. Overcharging happens also, but from what I have seen, nearly every smart charger undercharges almost all the time, and it is much worse on a deep discharge, where you actually need more time than normal to recover that deep discharge and minimize the damage.

I wouldn't be surprised (have no data) that proper charging could cut deep discharge damage in half, or more.

[BobB]

Originally Posted by booster

But, IMO, the thing that is making the problem way worse than it needs to be is the quality of chargers, and all the undercharging that is happening.

Booster,

Do you think it is the quality of the charger or that many chargers are pre-programmed in a way that does not match the recommendations of the battery manufacturer? If so, would that lead one to believe going to a programmable battery charger would help with that issue?

[booster]

From what I have been able to learn playing with our system and batteries, which are wet cells right now so I can check the state of charge accurately, about the only way to accurately charge wet and AGM batteries is with a charger that can end the charging cycle based on how many amps the battery or batteries are taking (called ending amps, or return amps). Doing the charger cycles based on timers and algorythems doesn't cut it, it appears. Most of the smart chargers seem to leave the batteries undercharged, especially when they are big battery banks and deeply discharged.

There are very few chargers that will do the return amp charging, and even the ones that will do it make it so you also have to buy their fancy remote and monitor in most cases. Not cheap stuff and very hard to find out if they do that style charging, because it only shows up in the instructions and specs for the remotes and monitors, not the chargers.

There is also the issue of chargers that use return amps to control the charging, but measure it at the charger instead of the batteries with a shunt. Any loads running in the van mess the charging up, unless you allow for it, and make sure you are using what you allowed. We have a charger like that, which works wonderful when no loads are on, but is a bit of PITA if there are loads.

[BobB]

Booster,

Thanks for info. A bit beyond my understanding but thank you.

In another thread, I noted that I am NOT a techie with electric (but I can compare spec sheets) So I need to rely on experts.

I read JH of RT stating:

"Our EcoTrek technology allows you to use 90% of available power before you have voltage loss. You will get up to 3000 cycles from our EcoTrek modules. Basically you will never need new batteries unless you live in your unit for more than ten years full time."

So how accurate is that 90% (10% SOC) gives you up to 3000 cycles? EcoTrek has not been out with Lithium for 10 years so all that is a guess. Who has been around that long using lithiums?

So I did some surfing on the net. See many claims of 3000-5000 cycles and comments in this thread keep talking about running the system down to 20 or 25% SOC. So I went to MasterVolt, Genasun, and Victron - names that have come up in other forums, companies with extensive experience making energy systems (and some with lithium batteries) for marine, military, etc.

MasterVolt: “Mastervolt Lithium Ion batteries have a realistic lifespan of over 2000 cycles at a depth of discharge (DOD) of 80%.”

Gensun: “And with lithium’s ability to discharge down 70% for 3000 cycles.....”

And Victron had this a pdf with this info:

CYCLE LIFE
80% DoD - 2500
70% DoD - 3000
50% DoD - 5000

Three well known, experienced companies are coming up with the just about the same numbers.

Seems any system "on the cheap" is going to need some way of controlling how low the SOC gets before the charging starts up. And if RT wants to get 3000 cycles, they might want to reconsider telling their customers not to use more than 70%.

Do others think those numbers are reasonably accurate? Who do we want to believe? Who do we need to believe?

[Davydd]

We will know in 10 years.

What I do know is that lithium batteries have performed better and outlasted all other types of batteries in phones, computers and power equipment so far.

[BobB]

Davvyd,

Is there any way you can measure recharge cycles (length, duration, number)?

Especially, if you discharge one night down to, say, 75% SOC, drive the next morning and they recharge from your engine and/or solar panels, then camp for the next 3 days, with them running down to some SOC, but recharging every sun day, etc. Length, duration, and number constantly variable.

Or is the idea of full - down to 25% SOC - discharge and then recharge up to 100% and keep doing that over and over, all theoretical?