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Old 10-27-2018, 10:53 AM   #21
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Nice! Please share your charging results too. How long will it take to charge back to 100%? How many amps does your charger put on the battery? Do the Amps taper off like a wet cell or do you see max Amps until fully charged?
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Old 10-27-2018, 11:05 AM   #22
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Hi

Ok, those results look fine to me. Still above 13V (resting) at 40% discharge makes sense from the curves I have seen. Since they are your batteries and killing them does not impact me .... I wonder what the capacity is when run down to 12V ...

===

Setting the voltage on any converter should be done at the output lugs of the converter. That is the closest you can get to the servo in the converter. Obviously a multimeter is part of the process. Just how you hold on to two multimeter leads and twist that little pot at the same time .... deep breath ....

The risk of setting a converter output while looking at the battery is that there is current running into the battery (maybe quite a bit). The converter will get set to allow for however much current that is. Once the current drops back, the voltage will rise. If it rises to far, the BMS will get a bit bothered ( = maybe go into self protect mode and cut off the batteries).

For the BB's the converter should not be set above 14.6V. From what I have seen, there really is no value in setting it above 14.4V. If you have a solar charger that goes up to 14.4 V from time to time, set the converter to 13.7V. You still will have plenty of charge in the batteries.

One subtle issue - the "stock" AS solar charger is temperature compensated. Since the sensor is indoors, that's not really useful. In the winter, stored outdoors, ...hmmm.... the temperature compensation will then work. If it works well (.. who knows ...) it will drive the output voltage up above 15V. Definitely not what your BB's want to see. The same sort of thing could happen with a Victron MPPT if temperature compensation is not turned off. (Yes, you read correctly Bob saying temp comp is a bad thing .... )

======

Best data from "the factory" (that sounds much more official than Sean) is to fully disconnect the batteries for winter storage. Essentially no parasitic loads at all, including the mighty BMV 712 and it's 500 ua load. How big a deal is 500 ua at zero degrees? Bottom line is that nobody really has solid data and better to be safe than sorry. (Yes, that's yet another hijack isn't it ....)

Bob
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Old 10-27-2018, 12:01 PM   #23
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Well, you won't find out from me🤣.... on advise from Dennis at BB C/S I'm not going below 12.5v...period. I think that the closer you get to 12v the more likely it is that you'll fall off the lithium battery cliff, it goes to zip quick.😳
I did set the output at the lugs...on the bench, before install...just clamped the probes, gently.

We're back charging, getting too cold here in WNY, all Winterized, just flip the disconnect and wait for Spring.😥


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Old 10-27-2018, 12:23 PM   #24
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Originally Posted by ROBERT CROSS View Post
Well, you won't find out from me🤣.... on advise from Dennis at BB C/S I'm not going below 12.5v...period. I think that the closer you get to 12v the more likely it is that you'll fall off the lithium battery cliff, it goes to zip quick.😳
I did set the output at the lugs...on the bench, before install...just clamped the probes, gently.

We're back charging, getting too cold here in WNY, all Winterized, just flip the disconnect and wait for Spring.😥


Bob
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Hi

Based on the curves I've seen, there's not a lot left in a BB battery once you hit 12.5V. The amp hours between there and zero are pretty small. Indeed the BMS *should* cut things off before there is damage. No, I'm not trying it on mine either, 10 year warranty or no 10 year warranty.

So - batteries stored outdoors with the trailer or taken indoors?

Bob
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Old 10-27-2018, 12:48 PM   #25
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Hi

Based on the curves I've seen, there's not a lot left in a BB battery once you hit 12.5V. The amp hours between there and zero are pretty small. Indeed the BMS *should* cut things off before there is damage. No, I'm not trying it on mine either, 10 year warranty or no 10 year warranty.

So - batteries stored outdoors with the trailer or taken indoors?

Bob
They will be in the trailer, disconnected but monitor still in the loop....I have noticed that the draw from the Victron doesn't register on the monitor. 3ma/mo. If the draw becomes a problem I'll bring them in...I am able to ck them from the living room,🤣

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Old 10-27-2018, 12:54 PM   #26
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So I do have mine set at 3 stage. I could set to single stage and leave them at 13.8 or so. That seems reasonable. The solar charger will go to 14.4 most days. Just didnt want to send 14.4 to the BBs all day every day.

And I did measure with the batteries disconnected. Right at the converter.
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Old 10-27-2018, 02:28 PM   #27
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So I do have mine set at 3 stage. I could set to single stage and leave them at 13.8 or so. That seems reasonable. The solar charger will go to 14.4 most days. Just didnt want to send 14.4 to the BBs all day every day.

And I did measure with the batteries disconnected. Right at the converter.
Hi

The gotcha with having the converter set to 3 stage is having it drop back to around 13.2V ( = lead acid float voltage). That's right at the point of the voltage curve where the battery starts to really discharge. Above 13.4 or so, it just sits there doing pretty much nothing at all. Run it up above 14.3-ish and you get the BMS into equalize mode.

=====

Unless western NY has warmed up a lot since I grew up there, it will be getting a bit colder there than down here on the southern end of PA. It will be interesting to see how things work out.

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Old 10-27-2018, 02:36 PM   #28
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Hi

The gotcha with having the converter set to 3 stage is having it drop back to around 13.2V ( = lead acid float voltage). That's right at the point of the voltage curve where the battery starts to really discharge. Above 13.4 or so, it just sits there doing pretty much nothing at all. Run it up above 14.3-ish and you get the BMS into equalize mode.

=====

Unless western NY has warmed up a lot since I grew up there, it will be getting a bit colder there than down here on the southern end of PA. It will be interesting to see how things work out.

Bob
Well, my trailer is in storage for the winter now so not worried about that. I have the batteries with me.

Maybe when I pick the trailer up I'll set it at 13.8 constant.
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Old 10-27-2018, 04:42 PM   #29
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13.8V is really not ideal for a BattleBorn, as 4x3.6V is 100% charge and it cannot balance cells if it doesn’t hit at least that...but really you would want occasional 4x3.65V target to balance every so many cycles.
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Old 10-27-2018, 05:07 PM   #30
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13.8V is really not ideal for a BattleBorn, as 4x3.6V is 100% charge and it cannot balance cells if it doesn’t hit at least that...but really you would want occasional 4x3.65V target to balance every so many cycles.
Yep...thats why BB c/s recommended 14.4v fixed when I called for charging recommendations 👍

Bob
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Old 10-27-2018, 05:40 PM   #31
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Originally Posted by uncle_bob View Post
~~

Setting the voltage on any converter should be done at the output lugs of the converter. That is the closest you can get to the servo in the converter. Obviously a multimeter is part of the process. Just how you hold on to two multimeter leads and twist that little pot at the same time .... deep breath ....

~~
I've found that eating with chopsticks offers good training for that. What gets me is putting the meter on the (conventional) batteries themselves... my shoulders are a LOT wider than the space between the propane cover and the front of the trailer and the terminals are much farther apart than typical converter outputs... then trying to keep the meter somewhere I can read the display while doing those gymnastics is entertaining...
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Old 10-27-2018, 05:55 PM   #32
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Why would you do it after install...?

Bob
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Old 10-27-2018, 07:32 PM   #33
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Yep...thats why BB c/s recommended 14.4v fixed when I called for charging recommendations 👍

Bob
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Hi

Ummm..... errrr .... you may want to dig a bit into some of the other threads here. Probably the best conversation about just what is or isn't best is buried in a couple of them.

The gotcha they have is that there are a bunch of chargers out there. Those chargers work a lot of different ways. They very much want to make sure that everybody knows that their batteries will work with all of them. Thus saying this or that is "not good" is not the way they do it.

Bottom line is that the batteries pretty much go to zero current (don't use the term float in this case .... they'll yell at you ...) at 13.5 to 13.8V. Since the cells are at >95% charge, that's fine. Go above that point and they start playing equalization games / don't really charge any further. They may indeed be less happy when perpetually charged at higher voltages.

It's not super hard to see all this with a current monitor setup. The equalization current is simple to measure once things stabilize at 14.4 to 14.6. Subtract that out and you can see how much has actually been put in as you go from 13.5 to 14.5. It's not much at all.

Going below 13.3 is not a great idea. That's 13.3 at the batteries. Given that there are drops in the wiring under loads, setting the converter to 13.3 may not keep the batteries above that point. The objective here is to not be doing a lot of charge / discharge / charge / discharge on the batteries. Yes it's weird that you have a voltage range like that but batteries can be weird.

If you subscribe to the never charge above 80% theory, then you have a bit of a hard task. You want the battery voltage to be at 13.236 volts (or some other magic number like that). Take it to 13.212 and you are way to low. Take it to 13.2791 and you are overcharged. Those are random values, but they aren't far from the truth. They also are temperature dependent so what works at 70F isn't the right set of numbers at 90F ....

Could you servo it with a current monitor? Well yes if you could come up with a way to re-sync the monitor. They all depend on detecting a "full charged" state and resetting to 100% pretty often. Take that away and their accuracy suffers ...This whole thread started out with a great example of that.

Bottom line - you have a 10 year warranty and data that at RV sort of charge rates you can get 5,000 cycles to 80% capacity. That's running the charge level from 100% to 0% and back again. You would be hard pressed to get in more than 200 cycles (full depth cycles) in a year of normal use in an AS. That would get you to 25 years .....

Lots of fun..

Bob
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Old 10-27-2018, 08:11 PM   #34
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13.8V is really not ideal for a BattleBorn, as 4x3.6V is 100% charge and it cannot balance cells if it doesn’t hit at least that...but really you would want occasional 4x3.65V target to balance every so many cycles.
I'm saying 13.8 because in my case I also use a solar controller that hits 14.4 regularly.

I'm thinking of there is no sun then I'd never drop below 13.8. I suppose I could go higher. But still quite uncertain that 14.4 is best.

Honestly, I like when my converter stops charging. The fan shuts off and I can enjoy the reason I'm out in nature!
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Old 10-28-2018, 09:26 AM   #35
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I'm saying 13.8 because in my case I also use a solar controller that hits 14.4 regularly.

I'm thinking of there is no sun then I'd never drop below 13.8. I suppose I could go higher. But still quite uncertain that 14.4 is best.

Honestly, I like when my converter stops charging. The fan shuts off and I can enjoy the reason I'm out in nature!
Hi

You do need to get up above 14.2 every so often to engage the equalizer in the BMS. Nothing much is going into the battery or coming out of it at 13.4 to 13.9V. The converter is not running at all unless you have a load somewhere pulling power. If you are pulling power and are on shore power, that's what the converter is there for. Why wear out the batteries? Stay away from 13.2V where the current is chugging in an out of the batteries all the time.....

Pretty much everything above can be observed by playing with a current monitor setup, some loads, and a programable converter / charger. It's an entertaining thing to do on a rainy day in the trailer .... You can also dig into the BB posts here and get the same info, but that's not as much fun

If the converter fan is the issue, address that point. The fan(s) on my Victron only kick on when it's doing heavy lifting ( = charging at a measured 80A into the batteries). Normal loads (lights + fridge + Alde + water pump) around the trailer don't get it going at all. Since that's probably < 8A, I don't find this alarming at all.

Bob
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Old 10-28-2018, 09:50 AM   #36
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go to the BB or victron site

they both have video on how to set the victron devices to support lion batteries
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Old 10-28-2018, 10:26 AM   #37
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go to the BB or victron site

they both have video on how to set the Victron devices to support lion batteries
Hi

Unfortunately the Victron site focuses on their batteries (which are quite different than the BB's) and the BB site does not (yet) have a video on the Victron chargers or inverter / chargers.

Bob
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Old 10-28-2018, 11:03 AM   #38
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Could it be that too much emphasis is being put on the converter and it's parameters when it should be on the BMS of the batteries.
Does the BMS really care where the voltage is coming from as long as it's within it's operational spec's...TV alt, solar, trlr converter? (BB specs...Acceptable Voltages 14.4 – 14.6 for bulk charging)....DC volts is DC volts.

Bob
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Old 10-28-2018, 11:30 AM   #39
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Could it be that too much emphasis is being put on the converter and it's parameters when it should be on the BMS of the batteries.
Does the BMS really care where the voltage is coming from as long as it's within it's operational spec's...TV alt, solar, trlr converter? (BB specs...Acceptable Voltages 14.4 – 14.6 for bulk charging)....DC volts is DC volts.

Bob
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Hi

The issue is indeed not the source of the voltage, but the voltage it's self. A constant 14.4V 24 hours a day 365 days a year from solar would be no different than the same voltage over the same time period from a converter charger.

Obviously, solar is not a 24 hours a day 365 days a year sort of thing. In a lot of cases the output of the converter / charger is far from 365 days a year. What happens with one person't usage pattern does not happen with another usage pattern.

The BMS *does* do something very different at 14.x volts than it does at 13.x volts. That is at the heart of this. Yes, it will deal with whatever you throw at it. The issue is how it deals with it. At the higher voltage, it goes into a mode designed to equalize the voltage on the cell banks. That takes them all up to max voltage and keeps them there forever and ever ( or as long as the 14.x volts is present.

There are a couple of problems. One is that in equalize mode, you are putting some finite (though likely minor) stress on the BMS. It will wear out just a little bit quicker when stressed. Is this taking it from a 287 year life (= mtbf) to "only" a 87 year life? who knows ... It is pretty clear that taking all the cells to max voltage all the time is less than ideal.

What is very clear is that charging above 14V does not add any significant amount of energy to the battery bank. Once past the low 13V range (yes depending on temperature) the battery is essentially "full". Since there is no gain and some (small) risk to the higher voltage .... why do it?

Bob
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Old 10-28-2018, 11:57 AM   #40
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My bad Bob...I just ass-u-me that no-one is charging 24/7/365.

To your point...two screenshots. "Fully" charged and at rest a day later.

Bob
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