Topics

charging info of house batteries while driving


Dick Stevenson
 

Hi all,

My name is Dick and I have a 2016 View.

I am contemplating some upgrades and starting to collect info to do so.

One of the upgrades might be to change battery type which would likely entail a new charging profile for the solar, battery charger, and for the charging done while driving. Solar and battery charger should be easy.

I am curious if there is information on the charging of the house batteries via the alternator that occurs when driving. How does the charging occur? I assume the chassis/starter battery is charged by the alternator and internally regulated inside the alternator. But what is the system to charge the house batteries while driving and how is it regulated and is there information on the charging profile.

Thanks for your help,
My best, Dick Stevenson


Tom
 

Dick,
There is a relay under the passenger seat that is energized when the engine is running. It is the same relay used in the boost feature. This connects the chassis and coach batteries together so both are charged with the same profile from the alternator. 

TomF 13NV


Dunc 18ND W.CO
 

If you upgrade to Lithium coach batteries  you will need to disable the cross-connect relay when driving due to dissimilar charge profile vs any lead acid. You can keep the "battery boost" feature if you keep the 12V coach bus. Victron and other suppliers have 12V source chargers that handle Lithium charging profiles.

I use one of the Victron chargers in my system which provides additional 15A of charging current when enabled while driving. I use this at night  or times I want more charging than what the PV array is producing enroute to the next site. You don't want to pull a lot of current from your alternator as it can get damaged and is extremely expensive to replace.
--
Dunc, W.CO, 2018 N24D
800W Solar, 10kWh Tesla Coach
Gyrocopter Toad


Dick Stevenson
 

Hi Tom,
That is what I thought might occur: and worried about. This is likely a pretty primitive charging algorithm (from the internally regulated alternator) and likely not in the best interests of battery types such as Gels, AGMs and Lithium. Do you know what others have done when they change battery types?
Thanks, Dick


Chuck W.
 

Dunc, can you explain more about the need to disable the cross connect? 

I've replaced the coach batteries with a pair of 12v lithium and haven't done that.

Chuck 08NH MN


Tom
 

Dick,
It is fine for any lead acid based battery which includes AGMs. The Lithium's may have some additional requirements like needing higher charging voltage to get to 100% SOC and a means of limiting the charge current from the alternator. The requirements may also vary depending on the battery brand recommendations. These are only what I have heard discussion about as I not am not interested in Lithium batteries right now. I use 2 6V Duracell (wetcell) 230 AH batteries.

Tomf 13NV


old_b4_my_time
 

If planning on still using the boost solenoid to "jump start" the engine off the house bank once it "goes lithium", make sure the BMS for that lithium mfg supports large motor starters, as there is a flyback voltage (CEMF) from starting that not all BMS can handle.   Same for starting the generator off a lithium battery but the generator CEMF spike is not as high as the main motor starter of course.   Some wiring changes would also be needed as stated by @dunc because you would need to disable the engine "run" condition's closing the boost solenoid while still provide for the boost switch to work.

Also if you are expecting near the same charging amperage out of the alternator that the dual GC2s often call for (55A) you'll need quite the expensive DC2DC charger if you go with a model many lithium battery manufacturers recommend such as the REDARC.   To approach the same rate as the lead/acid charge profile you'll need minimally a BEDARC BCDC1250D that runs around $541.
--
Don - 2006 Navion J


old_b4_my_time
 

On further thought, you'd likely need to energize a NC contact relay with the "run signal" from the Sprinter engine electronics, energizing a new small relay with the "run signal" while the boost button wiring would be run through that NC relay contact, meaning those NC contacts are broken apart when the relay is activated,  preventing the boost switch from working while the engine is running because it is presumed that the DC2DC charger is "wired around" the poles of the boost solenoid.  Most DC2DC converters need some type of signal to active them and most of them activate with either the high voltage seen from a running alternator or the less expensive models actually require a "run signal" to energize that would make sense to also provid that signal wire going to the DC2DC charger from the other side of the contacts from the NC contact of the new run-relay which is energized with the Sprinter electronics "run signal" and this would energize the more inexpensive DC2DC converters.

This is one reason I'm always wondering why many follow the youtubers always pushing the 24v and 48v systems, trying to promote them for RVs.   Who wants to give up a boost feature or the generator starter because they've installed a "configured for homes" solar system in a RV and who wants to depend on some 24v or 48v to 12V buck converter to power all the house 12V appliances.  .
--
Don - 2006 Navion J


Dan Booher
 


Hmmm, I've got two  80 amp hr lithium batteries, with no special charging equipment.  They are  almost 4 years old. I have a $50 hardwired current monitor,   230 w solar. Stock Zamp controller.  I monitor and never dip below 60% capacity. I've been told I can go down to 20%. I have thought about changing the converter to a lithium specific version, but have yet to do so.  ( I hardly ever plug in).  I do almost all boondocking and have never had any issues.  Stock alternator.    
2016 NJ.


Dunc 18ND W.CO
 

Chuck,

Assuming you have a "drop in" battery, like from Battle Born, there will not be any safety issue. Their internal Battery Management System (BMS) will keep you safe, but it can not make up for incorrect charging algorithm. Did you change your battery charger/converter at the same time as you upgraded the batteries?

Lithium batteries can accept a much higher rate of charge than Lead-acid. Therefore they will be more fully charged, and much faster using a charger that is set up for these parameters. Your MB generator charging system is not set up this way, therefore a different method must be provided if you desire more than solar or shore power for charging.

Look at the nice chart and explanation provided here, with data from Progressive Dynamics. This shows how the higher Lithium charging current provides a much faster and higher charge. 
https://www.mygrandrv.com/forum/showthread.php/19791-Lithium-Battery-Owners-Some-Useful-Data

The cross-connecting solenoid has two signals to the coil. One is from the "boost" button, while the other is from the ignition switch "run" circuit. The latter wire should be cut so the alternator is not charging the coach battery - assuming you have installed an alternative method. I chose the Victron Orion series Smart DC-DC charger because it is integrated with all the other Victron devices I utilized. You can select its maximum allowed charge rate to limit stress on your (expensive) alternator.

--
Dunc, W.CO, 2018 N24D
800W Solar, 10kWh Tesla Coach
Gyrocopter Toad


Dick Stevenson
 

Hi all,

Lots of good thoughts and info: I appreciate it.

I will respond directly when I have anything relevant to say.

My best, Dick


Dick Stevenson
 

Hi Tom,

You report that the charging while driving: “is fine for any lead acid based battery which includes AGMs.” I interpret this as the current/voltage coming from the alternator is so minimal as to not put those lead acid based batteries such as AGMs, Gels and flooded in danger as they do have different charging algorithm requirements. Is that accurate?

Thanks, Dick


Christophe P.
 

Instead of cutting that run wire to the solenoid, I installed a rocker switch next to the driver side to enable alternator charging to my lithium batteries. 

I ran a bunch of measurements and the alternator won’t produce more amps than what it’s rated for. So at idle, it generates at more 110ish amps even though it’s rated 220. And my batteries were 50% charged then. So they only got around 80-90 amps. If you mostly use solar for charging and once in a while need alternator to boost it up, you don’t need to go all fancy.

Lots of folks up their battery bank with bigger agm or more golf cart ones and don’t switch to using fancy dc-dc or inverter. So depending on how much lithium you get, you may not need it either.

Christophe

On Aug 28, 2020, at 7:48 AM, Dick Stevenson <alchemy128@...> wrote:



Hi Tom,

You report that the charging while driving: “is fine for any lead acid based battery which includes AGMs.” I interpret this as the current/voltage coming from the alternator is so minimal as to not put those lead acid based batteries such as AGMs, Gels and flooded in danger as they do have different charging algorithm requirements. Is that accurate?

Thanks, Dick


Christophe P.
 

EDIT: when I said what’s it’s rated for I referred to the alternator chart that shows the amps produced at what RPM. At idle this alternator won’t produce more than 110 amps or so. 

Christophe

On Aug 28, 2020, at 8:24 AM, Christophe P. via groups.io <pqt_chris@...> wrote:

Instead of cutting that run wire to the solenoid, I installed a rocker switch next to the driver side to enable alternator charging to my lithium batteries. 

I ran a bunch of measurements and the alternator won’t produce more amps than what it’s rated for. So at idle, it generates at more 110ish amps even though it’s rated 220. And my batteries were 50% charged then. So they only got around 80-90 amps. If you mostly use solar for charging and once in a while need alternator to boost it up, you don’t need to go all fancy.

Lots of folks up their battery bank with bigger agm or more golf cart ones and don’t switch to using fancy dc-dc or inverter. So depending on how much lithium you get, you may not need it either.

Christophe

On Aug 28, 2020, at 7:48 AM, Dick Stevenson <alchemy128@...> wrote:



Hi Tom,

You report that the charging while driving: “is fine for any lead acid based battery which includes AGMs.” I interpret this as the current/voltage coming from the alternator is so minimal as to not put those lead acid based batteries such as AGMs, Gels and flooded in danger as they do have different charging algorithm requirements. Is that accurate?

Thanks, Dick


old_b4_my_time
 

@Dunc But since the Battle Born (and very few) drop-ins have signal taps into their sealed BMS control circuit board, how does e.g. a BB individual BMS know how many you have in parallel?    If one BB is being a "good citizen" and drawing 50A, how can that one BMS know to "throttle down" if you have 4 in parallel?   The alternator still smokes if it has no protective circuitry (still waiting to see documentation on how the Sprinter handles near max-load conditions)     And regarding DC2DC, I have not seen one that reaches the likely 180A or more that a 200A sprinter might be capable of providing, with the most popular ones producing around 20A and on up to a very pricey 50A model.   Even that Victron Multiplus that everyone salivates over starts at $1200 and claims 80A max, a lot of waste of a 200A alternator.   (And I already have a 2000W PSW inverter and don't need another just to get a "free" DC2DC in the package.)

Still the only place I'm seeing a real need for charge profiles is perhaps in a converter situation where something must manage how the 120VAC charger is both supplying the house lamps and accessories and charging the batteries (if and when they need it) at the same time. (Of course all this goes to hell with a 24v to 12v or 48/12V buck converter powering everything in the coach if you're not running a 12V system and thus when everything turns into a maze of calculations since everything in the coach even when on "shore power" must come from constantly depleting the batteries and bringing them back up)  With this I'm also confused of how a charge profile comes into process if the BMS is passing all the current it can and only serves to 'switch off' if at the point that a voltage indicating full-charge is obtained (and of course the BMS also breaks the circuit when and if some fault such as temperature or over current is reached).   In other words what is the point of all that shaping and tapering of a charge profile if the lithium just eats all the current you pass to it up to point when the BMS thinks the cells have had enough and then snaps the circuit open (which by the way this factor is also warned about if you don't have some kind of voltage spike "sink" across the alternator such as a heavy duty varistor or more common, a chassis lead-acid battery and thus the "alternator unloading" syndrom caused a serious tripple digit voltage spike back into your 12V chassis electrical system).

Also does the battery bank really need some elaborate charge profile presented from the alternator when you drive for such short periods of time and with this assuming that the battery bank is in quite a "starving for current situation" and is going to likely be eating all the power you can pass to it during the initial 4-8 hours of conventional daily drives?

--
Don - 2006 Navion J


old_b4_my_time
 

@Christophe Let me say your kind of tests are few and far between and I understand why they would be unpopular where many drop $500 or more for this DC2DC box and you've found a way around that.    Can you elaborate more?

- what's your type of battery and how many do you have
- have you ever encountered a situation where the BMS drops during high current draw to where your system might encounter the famed "voltage spike" from the slow regular throttle-back where the spike can damage chais components?
- what's the lowest you depleted that bank and what did you see on the current meter when you started the engine and started charging
- and if considering you have no problems, why would you turn the rocker switch off, e.g. what reason or reasons

Thanks!
--
Don - 2006 Navion J


Christophe P.
 

- Lithionics 300Ah@12v, installed in early 2017
- Nope
- About 25% SoC and the current was about 100amp at most. My last measurement at 50% SoC showed that the alternator was producing about 130amps (or 110, somewhere around that) at idle and the battery was receiving 80-90 amps.
- Like most people when I initially did the install, I was worried about taxing the alternator too much and I had installed 400w of solar anyway. So I didn't want to rely on alternator charging unless for emergency. I quickly found out that in winter times, solar isn't sufficient so I use the alternator charging more during winter and never during summers.

Installing a DC2DC box that provides 50amps to the battery isn't a much better solution IMO because you're still taxing 60amps from the alternator (remember they're not 100% efficient) and you introduce yet another device that doesn't work with the boost functionality. Also my friend who's had several sprinter vans and a couple of those DC2DC chargers told me a lot of them are junk and failed early. Oh and they're pricey.
Now they have pluses since you can fully charge your battery with them but since I have solar, I can do it with that instead. And like I said in another thread: fully charging your lithium batteries all the time isn't the best thing to do for their lifetime. Tesla does it (defaults to 80% and only use 100% for long distance drives) and even the latest MacOS update does that now for MacBooks.


Christophe P.
 

Btw I attached again the alternator charging spec for the NCV3 ones (220 amp alternators). That means at idle, the alternator will not produce more than 130amps at low temp.


old_b4_my_time
 
Edited

Here's some more info for everyone to chew on.    And this is regarding talking wiring the boost solenoid to continue to function and from this it seems there is no need to attempt to keep the solenoid in circuit for a potential jump-starting because that is not recommended after you go lithium.  This email attached below came from Dragonfly Energy (Battle Born).

MyNotes1: The LiBIM he recommends sells for $179 on Amazon and if you read the specs it sounds even more flaky than my proposing a switch inserting a spool of 12 gauge wire in series with the alternator as an engineered solution.

MyNotes2: From item 4 below and the caution of going over the 0.5C rate, it appears as there may be nothing in the battery that prevents that from being reached and it's up to some other component to limit it,, which would dispel the belief that these top of the line LiFePo4 drop-in batteries are worry free, as they don't appear to be protected that much after all at least from an over-charging situation.  So this would make not only over taxing and alternator a concern but over-charging the battery as well.  (Of course there's always that gray area where you cross "capability" with "suggested rate"  and your being the one responsible for lowering the cut-off down to suggested and that requiring more battery management logic.

(Battle Born Batteries)   (unaltered received email)

Aug 27, 2020, 10:44 PM MST

Don,

Thank you for contacting Battle Born.

1. In general, you need at least two 100ah 12v batteries to start an Onan generator. The average Onan require a 440cca battery. Our 100ah 12v BMS limits discharge to 100 amps continuous, 200 amps for 30 seconds. A 200ah bank will provide 400 amps for 30 seconds. If you will be dependent on your generator for power, I recommend using a separate lead acid starter battery. If the generator will be used infrequently, you will have no problem starting the Onan with our batteries.

2. I do not recommend using our batteries to start your Sprinter. 

3. Our batteries will accept a low amperage charge. You can either limit the charging amperage with a DC to DC charger, or use a Precision Circuits Li Battery Isolation Manager (LiBIM) that combines the batteries on a duty cycle, allowing the alternator to cool. The LiBIM is activated by an ignition signal, and operates on specific voltage parameters.

4. If the available amperage from your alternator is below the 0.5C charge rate for your Battle Born battery bank, you can install a Precision Circuit LiBIM in place of your solenoid. The LiBIM has an available Signal post that can be used with a momentary switch on your dash.
-If the available amperage is above a 0.5C charge rate, I recommend installing a DC to DC charger to limit the amperage.

--
Don - 2006 Navion J


old_b4_my_time
 

@Christophe P.

Wow that's a pricey little dude.   Did you mount it to the frame under the coach or where did you find a spot for it?
It certainly encouraging that you can manage a behemoth like that and not over tax the alternator.
How long to recharge with the 400w e.g. from the 50% SOC mark?
Ever try jump starting via the boost and ever suffer BMS damage from it?
I would be looking at something around the 300-400aH range if I went to the trouble to switch out as well.
--
Don - 2006 Navion J