Date   

Re: Dash Air Cond. blowing hot air.

Suzanne Hinds
 

We had the same problem with our AC. It turns out it needed more Freon. I don’t think they tested for any leak, but it has been running cold since they filled it a few years ago. We were also told that we need to run the AC monthly when not in use.

Suzanne 13J CA


Re: Coach battery hookup

Christophe P.
 

I remember seeing it somewhere but a quick search:
https://evannex.com/pages/tesla-model-3-tips-and-tricks
says 80-90%.
Another one:
https://mashable.com/article/tesla-battery-charge-max/

I guess it's more 90%? My bad. But some other folks on sprinter-source mentioned 80% is a safer value.


Re: Coach battery hookup

Dunc 18ND W.CO
 

Where did you find that 80% charge value?
--
Dunc, W.CO, 2018 N24D
800W Solar, 10kWh Tesla Coach
Gyrocopter Toad


Re: charging info of house batteries while driving

old_b4_my_time
 


@Christophe P.    Yes, I see 55A into my 2 series GC2s at 60% SOC and that's as low as I have gone to date on the SOC.   I'm sure it would be more if I ever went lower.


Otherwise ref. topic on boost solenoid loss, I guess I just freak for some reason knowing I don't have a backup starting battery but if it's "out" as an option and with that then all my other worries are mostly moot as well.  I was worried that relying on a single BMS for auxiliary diesel engine starting might fry any of one or multiple BMS's on the first jump-start and perhaps if I had multiple ones in parallel, they might handle it better but still 200-400 potential voltage spikes across a MOSFET rated at 50-100V would be a little daring.  And I guess Battle Born sort of proves I had a valid concern.

And speaking of the BMS, do you know if that BMS in your battery is mosfet based or if the BMS on that unit you have just makes and breaks relays at the request of the BMS as it shuts down relays while over charging or excessive load (or other faults)?

From one perspective I think the multiple BMS of stacking some reliable 12V drop-ins might be better from a failure recovery perspective (e. g. removing the bad battery if it craps out rather than the whole battery failing) and in contrast I'm also considering something like you have.    I also looked at a lot of the youtubers and some were even using 4 of those Winston 100a 3.5V cells to create a 400aH system while using the 123BMS with the blue tooth and while I'm not crazy about fiddling with a phone all day to manage my daily life, I can't argue with the extended data access of a blue tooth BMS.    Still without really reading about anyone who's taxed this 123BMS which claims 300A capacity, I have to ask is that real or not and how does if react with a 155A microwave load tossed in and out for a few minutes every day.   And in contrast I also can't argue with the camp who says they don't want to manage and adjust the BMS, they just want a set and forget system.

Anyway here is something I've found which more on someone who is supposedly experienced and played with four Winston 100aH which makes up a 400aH bank and in these narrative he was using a 123BMS (which is the relay-cut-out as opposed to mosfet BMS):
https://marinehowto.com/lifepo4-batteries-on-boats/

Also interesting in the area of show and tell is this one who decided to add an additional alternator, which is supposedly an easy option on the V6.   I found it also an interesting study:
https://windinmyface.com/Sprinter-Batteries-Lithionics.html

Additionally here is a fellow GOM (grumpy old man LOL) who seems to feel the way I do about a lot of thus stuff:  (understand he's mostly talking home solar installation):   (And with all this one has to not discount the weight capacity of these coaches and how that might affect technology, particularly something as weighty as batteries)
https://www.youtube.com/watch?v=8dSlgrNwq5o



--
Don - 2006 Navion J


Re: charging info of house batteries while driving

Dunc 18ND W.CO
 

Exactly why I use a DC-DC charger, and suggest that the OEM solenoid be disabled as a charging circuit while driving. The DC-DC charger will enforce current limitations. Thus if it is set up for 30A charge in "bulk" mode, each of those four hypothetical Battle Borns will receive 7.5A charging current, and the chassis alternator load will be similarly controlled. Their internal BMS will further throttle as needed. NOTE - I am NOT an BB expert! Also many lithium batteries do NOT allow parallel connections.

I don't see why all "goes to hell" in your other scenario. The math is quite simple, sometimes adding the instrumentation needed to fill in the values is not! In the stock VN, shore power is used directly for 120VAC loads, and simply provides the input required in parallel to the converter for all 12VDC loads, including charging.

The need for "elaborate profile" is dependent on current SOC vs what SOC you want to end up with. On a Lithium battery, if you are "running near empty" and you want to be "full" in x hours, you can generally max out the charging current with no problems. This is why newer cell phones and power tools recharge so quickly. 
--
Dunc, W.CO, 2018 N24D
800W Solar, 10kWh Tesla Coach
Gyrocopter Toad


Tesla Coach Battery Installation - Why? How?

Dunc 18ND W.CO
 

I was asked numerous times about my system. I performed this upgrade this spring. The COVID quarantine gave me plenty of free time, and it achieved my "5 C" goals of Capacity, Cubic Inches, Cost, Conservation, and Connectivity.
 
Capacity
----------
We enjoy boondock camping, and abhor KOA-style facilities. We also enjoy the quiet, non-generator environment. I calculated that about 10kWh of storage capacity is required to power our two CPAP machines, a small continuous oxygen concentrator, along with the standard Norcold DC compressor refrigerator, and other small loads overnight, and be usable over at least 4 days of zero sunshine. Upgrading the inverter to 3kW capacity would also allow the dogs to be in air-conditioned parked comfort while we spent a couple hours away shopping or hiking.  
 
Cubic Inches
----------------
Maybe your copilot is different, but mine did NOT want to forego any of the great storage capacity we found in our lightly used, pre-owned 2018 Navion. This meant not filling the storage bays with batteries. Research found the Tesla car batteries to have the highest power per volume (cubic inches). All Lithium batteries are also about 1/3 the weight of a comparable lead acid battery. Good. They also charge 3x faster, and can be nearly fully discharged without significant damage. Lead acid batteries can only be discharged to 50%.  
 
Cost
------
So ka-ching, we have decided to purchase a larger inverter, and "go Lithium". But Lithiums are generally much more expensive vs comparable lead acid. We saved a bunch of money buying a used RV, can we do the same buying a slightly used Lithium battery? Yes! Besides, Ebay, there are many sources of less expensive used lithium batteries. However and per above, the Tesla battery is the most efficient in terms of volume, and can be readily found for the ~$1,000 range. Two Tesla Model S battery modules will provide 2 x 233Ah at 24V storage capacity for a total of 10.4kWh. They weigh 58 lbs each, and are 27" x 12" x 3". Thus with some minor trimming, two of these will fit into the Navion's existing battery box below the top entryway step. By comparison a typical Battle Born-style lithium battery are each 29 lbs, 12.8" x 6.8" x 9.0", and have 1.2kWh of capacity. So ten Battle Born batteries, at ~$1,000 each, and total weight of 290 lbs, with have the same storage capacity as two Tesla batteries at ~$1,000 each and total weight of 116 lbs. This is ~$8,000 in savings, plus take less space and less weight! I imagine used Tesla batteries cost will also decrease with time when replacement is needed - 10+ years from now? 
 
A Tesla battery has a built-in proprietary Battery Management System (BMS) that communicate with the car's computer to control charging, discharging, and internal battery temperature. Although many alternative BMS providers are available, I chose the www.Electrodacus.com for its low cost ($121), flexibility, and awesome customer support. A good review is seen here:
 
Conservation
----------------
Repurposing a used Tesla battery is also good for our environment. Each module is made from 444 toxic cells. Each cell is slightly larger than a AA battery. Whether you are a tree-hugger or not, you have to admit this is also a good thing.
 
Connectivity
---------------
If you want to spend the least amount of money, and have time to research, you can likely save a few dollars by mixing and matching devices to make this work. But with about $8,000 of battery cost savings jingling in your virtual pocket, it is prudent to look into the best full-system solution available. There would be no band-aid mixing and matching. Victron is among the most prestigious providers, and makes everything required with good instructions. Their customer service is done through resellers, and you WILL need help, so don't skimp by saving a few dollars through Amazon. Buy from a reputable brick and mortar business, especially one that thoroughly knows RVs and/or solar.
 
How
-----
This is not a detailed "How To", but a list of suggested components and details needed to achieve the full system goals. I plan to double my 800W available PV power so I have upsized various systems.  
 
Tesla Batteries, 2 x $1,000 + BMS, $121
 
All batteries are affected by temperature. The Tesla car uses electrical heaters and coolers to control antifreeze fluid temperature which is pumped through the battery modules. The lithium battery is best charged at about 65F, and that's where I keep mine. Aluminum plates were added to fully enclose the current battery compartment exterior. There is room to insert both batteries, plus 2" of blue construction foam inside. The opening at the top needs to be enlarged by about 1/2" on the upper/lower sides, and 1 inch on each remaining side to fit the batteries in. New top step rubber moulding was supplied by WBGO and cut for the larger opening. The top step was lightly modified to seal. The main battery cables, BMS cables, and heated fluid lines pass through bulkhead seals at the rear of the semi-sealed battery compartment. RV antifreeze fluid is kept in a Tupperware tub under the kitchen sink, heated by an aquarium heater, and pump flow is controlled with a Buck converter to about 10V DC. Bulkhead gland nuts pass all cables and insulated fluid lines into the front outside storage bay behind the passenger. 
 
 
Victron BMV-712 Battery monitor, $220
 
Although not strictly "required", this provides a quick way to monitor the overall battery health and State of Charge (SOC) either through the display, or Bluetooth connection to your smartphone. You can quickly see how much time in hrs/days that you have left with your battery at the current usage and SOC. I suggest having something like this for any RV coach battery! It allows you to perform an energy audit at any time.  
 
 
Victron MultiPlus (24/3000/70-50 Inverter/Charger, $1,200
 
Inverter/Charger - since committed to supplying higher inverter power (3kW), and the need to properly charge a 10kW lithium battery, both the stock inverter and converter must be replaced. Victron has numerous solutions, but this unit also provides several unique features. Among these are a "Power Assist" setting which allows control of shore power level. This is especially handy when "mooch-docking" and you are connected to your benefactor's wall outlet which has a 15A breaker. You can set the Power Assist to any value, like 12A, and the inverter will only draw up to that value from the wall outlet. Any additional power requirement will come from your batteries. Therefore you can likely run your air conditioning getting most of its power from the wall outlet, while sipping power from your battery. Another feature is automatic switch-over for shore power. You simply rewire all 120VAC loads to come from the inverter, through the existing circuit breaker box. The 120VAC loads, like microwave, etc. will always work, regardless of whether shore power is being used. The Multiplus is controlled via the Electrodacus BMS. If the Tesla battery voltage reaches the upper charging limit, the charger section is stopped. If the battery voltage ever drops below the lower limit, the inverter is stopped. You need to purchase the $75 Victron Mk3-USB adapter to initially program the Multiplus from your laptop. 
 
 
Victron Color Control GX, $516
 
Not required, but it provides two great features. 1) Single location to quickly view any Victron device state, control, and modify certain parameters, like the "Power Assist" value above; 2) It stores your past energy history on the Victron portal website for review by connecting to the internet via WiFi.
 
 
Victron Energy MPPT 150/45 TR SmartSolar charger, $450
 
The solar charge controller is enabled by the BMS when the batteries need to be charged. It displays status and history on the Color Control GX or via Bluetooth on your smartphone.
 
 
Victron Orion 24/12-70A (24VDC-12VDC converter), $265
 
This 92% efficient converter powers all the 12VDC loads through the existing fuse box. It will be disabled by the BMS if the battery voltages are at the low voltage limit setting.
 

Victron Energy Orion-Tr Smart 12/24-15A Isolated Dc-dc charger, $260
 
Not required. This device allows you to charge the Tesla lithium batteries using the chassis alternator. This can be handy if driving at night, or any other time you want to add a little more charge than your solar can provide while driving during the day. Typically my 800W solar array will provide about 600W at 24V, or 25A of charging power as the panels are not pointed directly at the sun. This DC-DC charger allows an additional 15A to be charging the battery. Thus about 30A at 12V is drawn from the vehicle alternator system. I think any more power draw can impair the alternator, especially when the headlights are on.  
  
--
Dunc, W.CO, 2018 N24D
800W Solar, 10kWh Tesla Coach
Gyrocopter Toad


Re: charging info of house batteries while driving

Christophe P.
 

Haha, yeah I paid something like $3k for it. But I bundled it with my solar install so I got the 30% tax refund on it :)
I had to install it under the bed of my 24J along with a new 3kw inverter charger.

On summer days, charging from 50% SoC to 100% with solar takes a few days really, perhaps something like 2-3 days? That if I don't use the RV.

No, I've never had to use the boost functionality because I have a trik-l-start device as well. It serves me very well.

The alternator will never work harder than its spec so it should be "safe" overall. I just want it to work under its rated spec, that's why I try avoiding using it to charge the battery. But I bet it's not an issue overall since Winnebago has it ALWAYS on and the fridge on top of that. So even if you battery bank isn't lithium, the whole system can still get the alternator close to spec: Fridge is about 16-20 amps while driving, the dashboard and all are between 20-30 amps. I'd think discharged lead-acid batteries can draw 50-60 amps easily, no?
But even if you're considering a DC2DC, you'll reach the max at idle (110-130amps) quick, so it's the same as not having one at all in terms of loads on the alternator.


Re: charging info of house batteries while driving

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


Re: charging info of house batteries while driving

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


Re: charging info of house batteries while driving

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.


Re: charging info of house batteries while driving

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.


Re: charging info of house batteries while driving

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


Re: charging info of house batteries while driving

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


Re: Coach battery hookup

Christophe P.
 

Dan,

I have 300ah lithium so about twice as much as you and do the same: Don't use a dc-dc charger nor inverter or whatever. I do override it with a rocker switch though so the alternator doesn't always charge it. I mainly use solar with a 400w system.

Here's the alternator charging chart, you know your sprinter won't get more than 110-130amps at idle. So for a 220amp rated alternator, that's 0.5C which should be safe for your alternator and give lots of amps to your batteries.

Also, just like what Tesla does for their batteries, lithiums shouldn't be charged more than 80% on a regular basis if you want full long life out of them. Once a month or so I do a full charge to balance the cells.
Inline image



Re: Dash Air Cond. blowing hot air.

Doug 17 Via T
 

Based on the description of the problem, I'm not sure that the one we were experiencing is the same. However, for those who experience periodic reductions in air flow from the a/c vents, here's information from the service report after our local Mercedes shop worked on it. "Suspect evaporator has frozen up. Replaced control head with updated part per LI83.30-N-068253." It wasn't cheap, and we've not taken a long enough trip to confirm that the problem is solved, but it now appears that Mercedes knows about the issue, has produced a better controller, and has issued a service bulletin.

Doug in OR
17ViaT


Re: charging info of house batteries while driving

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


Re: charging info of house batteries while driving

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


Re: Coach battery hookup

old_b4_my_time
 

I've heard that from a couple of other people as well.   I imagine it's all about how much the batteries can demand at their lowest SOC, what's "inside" the BMS and how Mercedes handles a heavy alternator load if and when it gets presented with a significant one nearing the alternator's capacity.   Now I've consulted with some pretty savvy experts over on sprinter-source.com including Midwest Drifter and no one seems to have any clear data on how the Mercedes alternator reacts when it might get slapped in the face with a heavy load (at near its maximum capacity) and assuming a severely depleted lithium bank is thrown across the alternator output to cause that.   Most people I talk to regarding their work on system analysis just walk in somewhere or sign up to the cool-aid group and go buy everything from the most expensive equipment list and settle into that being the norm as the cost of operation.   The died in the wool lithium crowd would likely scoff at what you have @Dan Booher and as to who is right (since you've never discharged them significantly enough to see any smoke rising), therefore I can't know.  I'm guessing that you'd have to run them down a lot more to really test what the alternator is going to do.   Still if you figure a 150a alternator, and with perhaps only the headlights as a load there's a lot of amps available "left over" from that Mercedes alternator and maybe even so many that a 160aH lithium supply greatly depleted would not over tax it.  

There is one fellow I've read an article from who has an interesting way to charge his slightly larger capacity bank (read from sprinter-source) - he uses what I call the "dinky charge option" (one of the 25a DC2DC chargers) while watching an amp meter and when the initial heavy load of the charging cycle passes after about 20 minutes, he says he has a heavy duty switch he throws where the lithium bank is then hooked directly to the alternator.     And if you look on some of the charts I've seen the LiFePo4 cells claim a level of 99% full at 3.5V per cell assuming 4 cells.   Now you divide 14.0 by 4 and what do you get?   So assuming your alternator charges at 14.2V, then you should theoretically be able to get your cells up to 99% charge without any kind of DC2DC converter which touts also raising the voltage to 14.6 or 14.4 or whatever the latest expert is suggesting.   But going the direct alternator connect route (even if at the end of the charging cycle) means you need an alternator that outputs what used to be the US standard of 14.2V.  And it/s weird how standards have turned into open interpretations these days as all my adult life we lived by a required 14.2V seen across a lead acid auto batt as gospel but with European cars I'm never quite sure what it is supposed to be standard now.   I know monitoring my T1N it was 13.8V for years, then it started fluctuating all over the lower value of 13V and finally failed and that was with no abuse or attempt to charge lithium.   Now I tied this failure to when the PO had the battery short out he had reported upon my purchase and I imagine this affected the alternator somewhat.   Anyway I had the alternator repaired and today it's reading 14.2V rock-steady and I know I purchased an after-market Chinese regulator in it as an experiment and it's working as well as any one I've ever seen (I monitor my alternator output with a dash readout).   So short story is however, a direct charging line should keep a bank at least at 99% which one could assuredly "top off" with the solar system if there was any slighting by the alternator charge which would leave only that initial surge to deal with and by being a standing member of that group of "having my cake and eating it too" I'd almost elect to do what the guy in sprinter-source did but approaching it from the perspective of being even more of a miser and leaving out the "dinky 25a charger" all together.   I am sort of thinking about a large wire wound coil out of that 12 gauge wire that Lion lithium FAQ was talking about but instead of stretching it where it might catch something on fire, I'd wind it on a spool like they do the old style golf-cart accelerators, then I'd install a switch like mister sprinter-source and throw it to bridge that resistor after the initial current onslaught to form a direct connect (perhaps after I see the resistor stop glowing - might even toss a nice smoked sausage in the center during the charging process LOL).   To me that would be a lot easier on my miser-dom than throwing down $600 to get a measly 50A out of the alternator through a DC2DC converter, especially when the alternator (depending on model) can output 150-200a).

So my guess is the reason you are still comfortably afloat is first you don't have a massively large bank and you have managed to remain just below the "smoke factor" with your light battery discharges or even your BMS is a little more robust than one's I've seen that can just only switch on and off at various voltages.    So you are lucky from that perspective.

(Side question - Not criticizing or anything but to settle my own curiosity, with the total of 160aH from the two 80aH lithiums, what was the motivation for switching from an option of say a 230aH dual 6V GC2 lead/acid setup over to a lithium bank which I imagine was a little pricey 4 years ago .... was it clean-ness of operation, zero maintenance, lighter weight or all of the above?)
--
Don - 2006 Navion J


Re: charging info of house batteries while driving

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


Re: charging info of house batteries while driving

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