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Old 04-20-2018, 06:16 PM   #1
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Default Lithium Batteries / voltstart.

As I research features we might want in a B van, I am thinkimg that Lithium batteries might well be a desirable thing, but not sure that we need or want "Voltstart." Especially when I learned that it is an option priced in excess of $1800!

We don't have pets any more, and I don't foresee needing to run the AC any time we are away from the trailer.

What I am wondering is whether - without voltstart - it is possible to set up a simple voltage drop monitor with an audible alarm to tell me I need to run
the engine - or generator to recharge the batteries,

I gather Lithium batteries hold their voltage and can be discharged much deeper than AGM's, so I'm not sure how well a simple voltage monitor would work.

Would that be what triggers "Voltstart," or does it use some more sophisticated means to determine when to charge?

I was thinking about a simple device like this

https://www.amazon.ca/dp/B00N6L8SMW/...a1d70caad2d6_S


You can set the alarm trigger voltage to whatever you like within range.

Any thoughts or advice?

Brian.
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Old 04-20-2018, 07:19 PM   #2
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Originally Posted by Wingeezer View Post
As I research features we might want in a B van, I am thinkimg that Lithium batteries might well be a desirable thing, but not sure that we need or want "Voltstart." Especially when I learned that it is an option priced in excess of $1800! ...

Brian.
I agree, this is a feature that is "Really Nice To Have"; but not critical. We don't have a RoadTrek so our configuration uses different labels, but we do have 600 AH of Lithium as well as the feature that starts the engine when the batteries fall to a personally configured State of Charge. Like you, we don't have pets. We tend to drive most days and that keeps the batteries charged. But we have done some rally-type events where we boon docked for several days in a row without driving. It was nice to know that if we were out and about, the batteries would be kept at a healthy charge without our constantly checking. Nice; not critical.
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Old 04-20-2018, 08:51 PM   #3
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Originally Posted by Wingeezer View Post
As I research features we might want in a B van, I am thinkimg that Lithium batteries might well be a desirable thing, but not sure that we need or want "Voltstart." Especially when I learned that it is an option priced in excess of $1800!

We don't have pets any more, and I don't foresee needing to run the AC any time we are away from the trailer.

What I am wondering is whether - without voltstart - it is possible to set up a simple voltage drop monitor with an audible alarm to tell me I need to run
the engine - or generator to recharge the batteries,

I gather Lithium batteries hold their voltage and can be discharged much deeper than AGM's, so I'm not sure how well a simple voltage monitor would work.

Would that be what triggers "Voltstart," or does it use some more sophisticated means to determine when to charge?

I was thinking about a simple device like this

https://www.amazon.ca/dp/B00N6L8SMW/...a1d70caad2d6_S


You can set the alarm trigger voltage to whatever you like within range.

Any thoughts or advice?

Brian.
The discharge curve for lithiums is relatively flat so using voltage readings for interpolating SOC provides a rougher metric than a true shunt driven SOC meter. The accuracy and usefulness of a volt meter reading is improved if you use a four digit meter which will indicate voltage changes of 10 millivolts whereas the the three digit meter will only register 100 millivolt changes. We replaced the factory meter with a Blue Sea 1733 OLED which unlike LEDs or LCDs is visible under any lighting conditions.

Early Etreks didn't have any voltmeter at all. Subsequent production did include one which evolved from a mini 3 digit round meter to the current configuration which is a four digit LCD meter which doesn't have any alarm feature.

The conventional wisdom is that voltage interpolation is a clearly inferior way to measure battery state of charge. As a generality, this is indisputable, but ironically with the Roadtrek's design, it turns out to be just the opposite because of the internal parasitic drain inherent in their BMS design. A state of charge meter like the Trimetric et al depends for accurate reading on current passing through it's shunt but with the Roadtrek BMS design, the parasitic losses are internal to the battery and are never registered by the shunt. Consequently, you can be dissipating somewhere between 75 - 100 ah of battery suds in 24 hours while your SOC meter tells you that you are good to go.

Whether to spend the money for Voltstart is a vexed question. It uses a preset voltage rather than SOC as for the trigger. Compared to the Autostart features you see in the ARV where you can control the set point and depth of discharge, you have no control over this with Voltstart. Additionally, the factory has reconfigured the Voltstart trigger from 12.4 volts to 12.8 volts which means there is pretty little run time before triggering it.
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Old 04-20-2018, 09:05 PM   #4
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If you are not a huge power user, and considering the problems Roadtrek has had with the lithium (including the not fixed, it appears, big parsitic losses) you might want to consider going with AGM batteries. You could still do an auto start if you wanted to, but without pets and unattended AC it is likely you wouldn't need it. The high parasitic losses in the lithium batteries makes the auto recharging much more necessary.

I think the 210 still has the option of two or 4 AGM batteries.
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Old 04-20-2018, 09:10 PM   #5
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If you are not a huge power user, and considering the problems Roadtrek has had with the lithium (including the not fixed, it appears, big parsitic losses) you might want to consider going with AGM batteries. You could still do an auto start if you wanted to, but without pets and unattended AC it is likely you wouldn't need it. The high parasitic losses in the lithium batteries makes the auto recharging much more necessary.

I think the 210 still has the option of two or 4 AGM batteries.
i thought the parasitic losses got better booster. where did you read this?
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Old 04-20-2018, 09:17 PM   #6
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I think the 210 still has the option of two or 4 AGM batteries.
That's correct, the option for two additional AGM batteries is available. One of the redeeming virtues of the RT Chevys is that they still allow you to pick and choose among the options. The rest of their line requires choosing packages which IMO sucks.
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Old 04-20-2018, 09:23 PM   #7
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i thought the parasitic losses got better booster. where did you read this?
I think it is more of not hearing that it had been fixed. The last discussion here was a few months ago IIRC, and there didn't seem to be any information on it getting better. I think somebody may even have had information from a Hymer engineer giving the amount.

BBQ follows this stuff pretty closely, he will likely have more details.
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Old 04-20-2018, 09:33 PM   #8
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Here is the post that said the losses were still high. 60 watts continuous, 24/7.

http://www.classbforum.com/forums/f7...html#post63685
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Old 04-20-2018, 09:33 PM   #9
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Hmmm - all that info takes this retired old mech. eng. some time to digest!

So are you saying that despite the fact that it isn't normally the best way to go, Rt does in fact use voltage readings to trigger the voltstart charging?

If so, do you know if an accurate enough monitor with audible alarm (ie more precise than the one I linked to) is available to monitor manually and start the gennie as and when required?

I haven't read up much about lithium batts (guess I should!), particularly on this issue of internal parasitic load. What is the figure you quote of 75-100 AH loss in 24 hrs? Surely a typo? no?!

Maybe as "Booster suggests I should just forget about not only voltstart, but also lithiums as well, and just stick with AGM's.

I believe RT still offers a set up with either 2 or 4 6v AGMS for the 210.

I have two AGM coach batts in our Airstream trailer - 8 years old and still seem fine for use!

Unless we change our camping style dramatically (could happen if / when we swap our trailer for a van!) then at least, 90% of the time we camp with shore power available.

Now and then we stop overnght at a Flying I and then I use my Honda 2000 gennie as needed. Works fine for us. May of course do a bit more stealth camping with a van!

Many thanks for your detailed response - very helpful!

Brian.
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Old 04-20-2018, 09:42 PM   #10
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Yep the parasitic in the Roadtreks really is that high. 60 watts, 5 amps, 120ah per day wasted. It is not a function of lithium batteries in general, just the poor design of Roadtrek's system.

From the way you describe your travels, two or four AGMs and an engine generator would probably do just fine for you, and you avoid the wasted power and monitoring and cold weather charging questions.
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