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Old 08-12-2016, 10:04 PM   #321
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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?
I would want to see the entire discharge vs life cycles chart before saying that. The could be equal or better at any one spot, and very much different over the rest of the curve. Some of the AGM starting batteries like Optima are very poor if the are run down very far, as are a lot of wet cell starting batteries, for instance.
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Old 08-12-2016, 10:09 PM   #322
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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.
Why not try leaving one or more of the batteries on line when you plug in shore power and see if the Volt Start no longer behaves the way you describe?

The volt meter RT is supplying is a three digit meter that has 100 millivolt resolution. This might suffice for rough determination of the SOC of AGMs, but for lithium batteries, this meter provides little more information than your hood ornament. The better choice would be a Blue Sea 1733 four digit meter that provides 4 digits with 10 millivolt resolution which gives you at least some shot at interpreting a Lithium battery state of charge. Rather than eliminating the battery light indicator and hogging out a hole there for the meter, I would install any meter of choice on the section of the panel that is normally used to support an Onan generator.
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Old 08-12-2016, 10:18 PM   #323
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I don't understand the fascination with voltmeters for SOC determination. They are barely better than the idiot lights, unless you have a designated fixed load you can hook up to get a more accurate, loaded, voltage reading.

It is not rocket science to put in a shunt based battery monitor, even with the sealed modules. Many can be programmed with any parasitic losses, so the 5 amps could be taken into account (unless it is so much it is out of range!). Other lithium providers put in SOC monitors (the one Greg linked a while ago does), so the only reason I can think of that would keep Roadtrek from doing it would be then the customers could see how much power is getting wasted.
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Old 08-12-2016, 10:21 PM   #324
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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...
Doesn't matter if 20% or 50% with AGMs but yes I am asking because the only safety net I am aware of is the low battery beep with AGMs and fat lot of good it is going to do you if you are not there to hear it. Is anyone doing automatic protection is what I asked. Does Voltstart on Roadtreks work with AGMs? I don't know so am asking.

With a rather large battery bank most can safely go through a day or two with plenty of cushion but with two batteries of around 200ah total you can easily slam through your low acceptable SOC before you realize it like having one more round in a bar with an unattended B. There is a practical limit in size and weight you can put in a B with AGMs that could never match LFP batteries.

I've experienced going through life of an AGM house battery in one year. I know many others that have done likewise. It got to be pretty much accepted that was the way it was. I got to where I trusted wet cell batteries more because I could (and had to) monitor them with water. I don't know if I could trust so called maintenance free batteries without some kind of automatic intervention. I got my two Great West Van wet cells through 4 good years without apparent loss.

My LFP batteries are indeed complex, but there are a ton of safety controls put on them that I can monitor.
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Old 08-12-2016, 10:32 PM   #325
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Yes, you can get Voltstart with AGM batteries...

I have a pretty good understanding of my typical AH usage and a battery meter so I am not worried about accidentally discharging my AGM batteries beyond what I am targeting which is generally around 50-70% discharge at most...
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Old 08-12-2016, 10:55 PM   #326
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Doesn't matter if 20% or 50% with AGMs but yes I am asking because the only safety net I am aware of is the low battery beep with AGMs and fat lot of good it is going to do you if you are not there to hear it. Is anyone doing automatic protection is what I asked. Does Voltstart on Roadtreks work with AGMs? I don't know so am asking.
Yes, the RT Voltstart works on both AGMs and Lithiums. But they are programmed with different voltage trigger points. Unlke your autostart, it isn't user programmable with respect to depth of discharge before engagement. The RT AGM Voltstart doesn't conform to the conventional 50% DOD level recommended. It's a lot lower than that. I asked an RT rep about the shortened lifespan of AGM batteries subjected to the RT Voltstart threshold and the response was that Voltstart was not designed to operate routinely but rather as a bailout measure for unusually high discharge situations. IMO, this is why they shortened their warranty on their AGM batteries to one year.
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Old 08-12-2016, 11:01 PM   #327
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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.
why is your inverter/charger on. it should be off UNLESS you are plugged in
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Old 08-12-2016, 11:04 PM   #328
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Another possibility is that they shortened the AGM warranty to 1 year as an added incentive to get Ecotreks with a 6 year warranty.

The build your own options on the Roadtrek website have eliminated the Onan generator option in many cases and the minimum Ecotrek option seems to be a 400 AH system with a 200 AH single Ecotrek no longer shown in some cases...
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Old 08-12-2016, 11:07 PM   #329
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Yes, the RT Voltstart works on both AGMs and Lithiums. But they are programmed with different voltage trigger points. Unlke your autostart, it isn't user programmable with respect to depth of discharge before engagement. The RT AGM Voltstart doesn't conform to the conventional 50% DOD level recommended. It's a lot lower than that. I asked an RT rep about the shortened lifespan of AGM batteries subjected to the RT Voltstart threshold and the response was that Voltstart was not designed to operate routinely but rather as a bailout measure for unusually high discharge situations. IMO, this is why they shortened their warranty on their AGM batteries to one year.
Could it be they are trying to account for the voltage sag you'll see in a rapidly depleting battery with a large load on it from the inverter?
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Old 08-12-2016, 11:12 PM   #330
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I don't understand the fascination with voltmeters for SOC determination. They are barely better than the idiot lights, unless you have a designated fixed load you can hook up to get a more accurate, loaded, voltage reading.

It is not rocket science to put in a shunt based battery monitor, even with the sealed modules...

... the only reason I can think of that would keep Roadtrek from doing it would be then the customers could see how much power is getting wasted.
Not hard to put a shunt in each module to measure the current but you also need a centrallized system to collect the info from each module and display the info. If an Ecotrek module is offline it may not be able to report the data so that is a potential issue. I expect it might be coming in the new release of the Coach Connect option.
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Old 08-12-2016, 11:16 PM   #331
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Could it be they are trying to account for the voltage sag you'll see in a rapidly depleting battery with a large load on it from the inverter?
They also need to set the trigger voltage high enough to avoid the inverter low battery voltage shutdown under heavy loads. I think a manual reset is needed on the inverter they use after a low voltage shutdown.
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Old 08-13-2016, 12:09 AM   #332
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Thanks, I will certainly consider both of your suggestions.
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Old 08-13-2016, 12:13 AM   #333
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I don't understand the fascination with voltmeters for SOC determination. They are barely better than the idiot lights, unless you have a designated fixed load you can hook up to get a more accurate, loaded, voltage reading.

It is not rocket science to put in a shunt based battery monitor, even with the sealed modules. Many can be programmed with any parasitic losses, so the 5 amps could be taken into account (unless it is so much it is out of range!). Other lithium providers put in SOC monitors (the one Greg linked a while ago does), so the only reason I can think of that would keep Roadtrek from doing it would be then the customers could see how much power is getting wasted.
I haven't had the opportunity to work with SOC measurements of large lithium batteries but I have done measurements with smaller lithiums used on electric assist bikes and with four digit measurements, you can put together a table that establishes the state of charge with usable accuracy.

That said, there is no question that shunt driven monitors are the way to go. With a setup like ARV provides this is easy to do because all of the batteries are either on or all off. RT makes this more difficult to implement because they permit the user to bring batteries on or off in a multiple independent battery setup. To initiate any of these monitors, the ah capacity has to be inputted. Consequently, with the RT arrangement, if the user takes one or more of the batteries off line, while the voltage reading may be accurate, the State of Charge readings would not be accurate unless the user reconfigured the ah capacity accordingly. So, with RT's setup you would either require multiple shunts and meters or a program written for the BMS that would determine how many batteries are on line and provide some correction information to the metering system. I'm sure it's doable but it's certainly more complicated.
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