ecotrek batteries using 6 internal amps

[gregmchugh]

I will not own this van long enough to even consider the cost of lithium or to get the benefit of the life cycles they may have.

Option 1, draw the AGMs beyond 50%, cost $700 for two new Lifelines and maybe another $700 if I keep the van long enough to wear them out.

Option 2, find space for two more AGMs and add wiring to connect to the two under the hood. Cost $1500 or so now and no loss of 12% in usable AH over the life of the batteries (max loss at 80% discharge) and lost storage space for the added batteries.

For me option 1 makes sense...

[mojoman]

My BMS cost less than $100, works great.

[cruising7388]

Originally Posted by Matsuie62

Starting my engine at O dark hundred (0200 really) when my coach is plugged in with NO load. This is plugged into a 30amp outlet at my house. Coach is not being used.

In what position do you leave the battery off, the individual lithium battery modules and the inverter switch? I vaguely recall a u-tube presentation that indicated that for shore power charging that the battery module switches and the inverter switch had to be in the on position.

Did your CS deliver with a digital volt meter on the control panel installed where the battery on indicator used to be?

[booster]

I think we are getting a bit off track here. The question was if the 50% rule was incorrect for AGM batteries, and somehow lithium cost comparisons got into it. The only reference was that based on the single chart the we found, lithium seemed to have more deep discharge issues than AGMs. So, please, go back to comparing AGMs at 80% vs AGMs at 50% and then separately compare lithium at 80% vs lithium at 50%.

Mixing all these things to try to prove a point gets very confusing and is most certainly to be comparing apples to oranges. It appears that all of a sudden it is AGM vs lithium, which is not the point.

All this started when I mentioned that Roadtrek used the the 50% rule for AGMs, not lithium, and that we had found information that indicated the 50% rule may not be very correct. I think this really points out why folks look for very simply (but often not accurate) generalizations, and how these things get set in stone (like the 50% rule).

[Davydd]

Does any converter with AGM batteries have a BMS that will shut your battery bank down if it drops to 20% SOC?

[Matsuie62]

Originally Posted by cruising7388

In what position do you leave the battery off, the individual lithium battery modules and the inverter switch? I vaguely recall a u-tube presentation that indicated that for shore power charging that the battery module switches and the inverter switch had to be in the on position.

Did your CS deliver with a digital volt meter on the control panel installed where the battery on indicator used to be?

Battery off , all LI batts off, inverter on. No, I don't have a volt meter. I 'm supposed to get one from Roadtrek and get it installed.

[wincrasher]

Originally Posted by booster

I think we are getting a bit off track here. The question was if the 50% rule was incorrect for AGM batteries, and somehow lithium cost comparisons got into it. The only reference was that based on the single chart the we found, lithium seemed to have more deep discharge issues than AGMs. So, please, go back to comparing AGMs at 80% vs AGMs at 50% and then separately compare lithium at 80% vs lithium at 50%.

Mixing all these things to try to prove a point gets very confusing and is most certainly to be comparing apples to oranges. It appears that all of a sudden it is AGM vs lithium, which is not the point.

All this started when I mentioned that Roadtrek used the the 50% rule for AGMs, not lithium, and that we had found information that indicated the 50% rule may not be very correct. I think this really points out why folks look for very simply (but often not accurate) generalizations, and how these things get set in stone (like the 50% rule).

But we love rabbit holes around here! I think we've taken a smidgen of information from one vendor and created all these arguments to turn conventional wisdom on it's head. But I agree, we've made it more complicated than it needs to be.

I'd submit that probably the occasional minor excursion on your AGM batteries is of no real consequence. People have anecdotal evidence for that. Is there a sweet spot that is OK? 55%, 60%, 70%, somewhere in between? Is 80% going to cut noticeably into your battery life if done here or there? 10 times? 20 times? 100 times? There is no evidence to support that. Good quality AGM batteries are not cheap - so who wants to draw their down to 80% today and find out if they fully recover their total AH?

The table from Lifeline clearly shows that sustained use of deep draw-downs has a consequence. I can only assume that those cycle counts are from testing and not just theoretical calculations. That cost is a 45% increase in your cycle cost. Yes, the AH available per cycle does not fall off a cliff as we'd expect. Again, that is most likely diminished if your excursions are minimal as common sense would tell you. What we don't have information on is as it approaches end of life, how far do the AH's fall? We can only assume the 12% drop off is an average over the lifetime.

The other argument that you can avoid a costly upgrade to lithium batteries simply by drawing down AGMs to low levels is short sighted and incorrect. The costs work out closely even if you disregard the other benefits, which are many and have value.

[booster]

Originally Posted by wincrasher

But we love rabbit holes around here! I think we've taken a smidgen of information from one vendor and created all these arguments to turn conventional wisdom on it's head. But I agree, we've made it more complicated than it needs to be.

I'd submit that probably the occasional minor excursion on your AGM batteries is of no real consequence. People have anecdotal evidence for that. Is there a sweet spot that is OK? 55%, 60%, 70%, somewhere in between? Is 80% going to cut noticeably into your battery life if done here or there? 10 times? 20 times? 100 times? There is no evidence to support that. Good quality AGM batteries are not cheap - so who wants to draw their down to 80% today and find out if they fully recover their total AH?

The table from Lifeline clearly shows that sustained use of deep draw-downs has a consequence. I can only assume that those cycle counts are from testing and not just theoretical calculations. That cost is a 45% increase in your cycle cost. Again, that is most likely diminished if your excursions are minimal as common sense would tell you.

The other argument that you can avoid a costly upgrade to lithium batteries simply by drawing down AGMs to low levels is short sighted and incorrect. The costs work out closely even if you disregard the other benefits, which are many and have value.

This was not a statement of not going to lithium batteries, it was a statement on how Roadtrek manipulated data to try to prove a point.

If you read the descriptions of the charts provided for total energy over life, you will see it was taken DIRECTLY OFF THE LIFELINE SOC VS CYCLES CHART, so it is the same information in a more real world format. As you say, Lifeline will have tested this, so it should be good information.

Anecdotal information from users is probably borderline useless, as there are way too many other variables, with the biggest one being charging quality. We found data from multiple sources that would reinforce the theory that the 50% rule is, at best, flawed. As has been stated repeatedly, number of recharge cycles is a very poor indicator of life of a battery. What really matters is how much energy you can store and reuse over the life of the battery.

[gregmchugh]

Originally Posted by Davydd

Does any converter with AGM batteries have a BMS that will shut your battery bank down if it drops to 20% SOC?

I surmise you are trying to make some point here about the danger of relying on manual intervention to prevent draining of AGMs below 20% charge when lithium BMS controllers handle this automatically??

Let me ask a similar question...

Does any converter with AGM batteries have a BMS that will shut your battery bank down if it drops to 50% SOC?

Not that I have ever seen but that doesn't seem to be something that was demanded to protect AGM batteries at the magic 50% cutoff point.

Maybe they are available as part of some battery monitors using a relay to disconnect the battery at some specific SOC.


Inverters have a low voltage shutdown point and generator auto start modules have a voltage trigger point so in some cases you might be able to configure these to automatically protect AGM batteries from discharge below XX% capacity...

[wincrasher]

Well, the 50% rule is there because there are SO MANY variables. It's presented as the safe approach, which it's still hard to argue that it's not.

That's probably why you have people that say they've taken care of their batteries and they've lasted 8 years, while others say they only have gotten 2 or 3 years out of them.

[gregmchugh]

As has been noted before, it will take more than data to change the minds of many of the believers in the 50% hard limit for discharging AGM batteries...

[wincrasher]

well, it will take more data that this. By the time enough rolls in, AGMs will most likely be obsolete anyways.

[BBQ]

Originally Posted by wincrasher

well, it will take more data that this. By the time enough rolls in, AGMs will most likely be obsolete anyways.

You'd never know,

by the time enough data roll in, AGMs will most likely be improved again, and making Lithium batteries even more uncompetitive?

[booster]

Originally Posted by gregmchugh

As has been noted before, it will take more than data to change the minds of many of the believers in the 50% hard limit for discharging AGM batteries...

Yep.

I do find it interesting that you can repair the damage done by poor charging by doing shallower discharges, which actually increase the number of damaging recharge cycles you would need. Sounds like Roadtrek logic.

[wincrasher]

Originally Posted by BBQ

You'd never know,

by the time enough data roll in, AGMs will most likely be improved again, and making Lithium batteries even more uncompetitive?

That may be surprising, as a colossal amount of lithium production is coming on line over the next few years. expect a collapse in prices and they become ubiquitous.

There are other chemistry types that have promise, as you see the occasional white paper here and there, so maybe something completely new will change everything. But I have doubts it will be anything old-tech like lead acid, tppl or agm. The market doesn't reward old-tech, does it?

[gregmchugh]

Originally Posted by wincrasher

Well, the 50% rule is there because there are SO MANY variables. It's presented as the safe approach, which it's still hard to argue that it's not.

That's probably why you have people that say they've taken care of their batteries and they've lasted 8 years, while others say they only have gotten 2 or 3 years out of them.

The 50% number is clearly safe but why is it 50% instead of 40% or 60% or other discharge limits that seem just as reasonable based on real data and not anecdotal evidence. If other manufacturers beside Lifeline provided real test data then you could see if the 50% number is a real limit for other batteries but it clearly is not a hard limit of any sort for Lifelines...

How are these anecdotal users killing their batteries? Are they just lower performing batteries that aren't as capable of handling discharge past 50%, are they not keeping them fully charged, are they discharging them completely repeatably which will not be good for any AGMs, are they exposed to high temperatures and being charged with chargers with no temperature compensation resulting in overcharging, are they using chargers which are not getting full charges on the batteries??

The focus on the 50% number is likely giving people a false sense of security and they are ignoring more likely causes for the early demise of their batteries...

Just my humble opinion...

[gregmchugh]

I have no doubt that lithium or whatever will replace AGM batteries in RVs and remove the downsides of lead acid batteries: weight, volume, long absorption charge times, etc.

No reason not to maximize performance for AGMs while they still around by using data to make operational decisions rather than using recommendations that have not been recently tested for validity...

[wincrasher]

Originally Posted by gregmchugh

The 50% number is clearly safe but why is it 50% instead of 40% or 60% or other discharge limits that seem just as reasonable based on real data and not anecdotal evidence. If other manufacturers beside Lifeline provided real test data then you could see if the 50% number is a real limit for other batteries but it clearly is not a hard limit of any sort for Lifelines...

How are these anecdotal users killing their batteries? Are they just lower performing batteries that aren't as capable of handling discharge past 50%, are they not keeping them fully charged, are they discharging them completely repeatably which will not be good for any AGMs, are they exposed to high temperatures and being charged with chargers with no temperature compensation resulting in overcharging, are they using chargers which are not getting full charges on the batteries??

The focus on the 50% number is likely giving people a false sense of security and they are ignoring more likely causes for the early demise of their batteries...

Just my humble opinion...

I'm not really disagreeing.

Most likely they focus on it as a benchmark so people can compare brands of batteries. If battery A is good for 1000 cycles, but battery B is good for 1500 cycles, then battery B is better, right?

Could be that running changes in production can make the battery cheaper, and has an effect on other performance aspects, but they can still hit the 50% use cycle life. That wouldn't really be all that shocking, would it?

One of my electrical engineers used to work for a battery manufacturer. He confirms they keep a tight lid on their testing data.

[Bruceper]

Originally Posted by wincrasher

expect a collapse in prices and they become ubiquitous.

I doubt this. A reduction in prices perhaps, but a "collapse" is not going to happen.

Good sealed Lead Acid batteries were $80-100 CAD in the 80's. And they're about $80-100 now. Same price minus increased earning potenial. Point is, the base price hasn't changed in 30 years.

[gregmchugh]

I am never shocked to find some manufacturer has reduced the performance of their products by reducing the cost of production, that is the way it goes and customers seem to go for cheap as opposed to good...

Lifeline started as an aerospace and military supplier so providing real test data is the norm for those markets and I prefer to buy based on proven quality not low price so I bought Lifeline but I would have bought Fullriver or Trojan or some other brands that are above average based on customer reviews...