Alternator to Lithium Battery Charging Question

I'm planning on swapping my "house" batteries to Battle Born LiFePO4s.  I'm doing my best to try to educate myself, first by watching as many videos as I can find, and reading as much as I can, including the posts here on this forum.  The part that remains most confusing to me is charging the LiFePO4s from the alternator.

I called the factory and the service rep said Battle Born visited them and told them there were no modifications (from their standard wiring for lead acid batteries) necessary from the alternator to the house batteries for a LiFePO4 install, and therefore, they don't wire any differently when doing a lithium build.  I've also seen a few posts here by individuals that have installed lithium batteries and have determined a DC-DC charger wasn't necessary.

I have a 2021 Ford E-450 chassis and no idea what alternator (three versions listed by Ford and the smallest is 210amp) I have and whether it is a "smart" alternator, vs. regulated.  I understand that LiFePO4 batteries have a lower internal resistance than lead acid and will want to draw more current, but for some reason, this doesn't seem to be an issue, at least according to the factory and most of the posts I've read here regarding this.

Battle Born's page ( https://battlebornbatteries.com/lithium-for-beginners-all-about-our-battery-management-system/) discussing their internal BMS says they don't regulate amperage and you need to have a "battery-to-battery" charger between the alternator and house batteries to keep the current below 50% of the battery bank capacity. This seems at odds with the info I received from the factory and from what others have posted here and I'm trying to understand why.

Any insight or further explanation would be much appreciated!

Like you I struggled with this question when I installed two 100ah Battleborn Lithium batteries. From other post and personal communications with forum members on this forum it was reported the factory did not make any changes to the alternator charge wiring with their Lithium option.  I knew from my measurements with the lead acid batteries there was a significant voltage drop between the alternator and the house batteries with the OEM wiring.  With electrical measurements as well as estimates from wire lengths and wire gauge it appeared that I was not going to overload my alternator so I decided to give it a try with stock wiring and fusing arrangement. If I found it unsuitable I would purchase a Victron DC to DC charger and replace the factory wiring to 6 gauge.


After installation of the Lithium batteries I checked current flow between the alternator and house batteries.  Typically I saw about 10 amps to zero when fully charged with maximum of about 15 amps.  The in-line fuse did not blow at this current.  I camped without shore power for approximately three months and found the arrangement suitable for my needs thus I did not or do I plan to go with the DC to DC charger.  I expect from model to model of motorhome the charge wire length and gauge could vary and have a significant impact on power transmission.  I see that the DC to DC charger is widely used in class B models.  I expect the shorter wire length on these  units may play a part in the need to have better regulation.


I should also point out I have 520 watts of solar which quickly recharges the batteries if I have decent sun irradiance.  The only time I need the generator is when running either the microwave or air conditioner.  For those without solar that do not want to run a generator for charging I can see a case for higher energy transfer from the alternator that the DC to DC would be advantageous.  This would need to be coupled with frequent driving.  I would be a little concerned at idling the engine at full demand from the DC to DC charger that the alternator could overheat.  This may or may not be an issue.   It is a question I would want to explore.


I am so impressed with the Battleborn Lithium batteries over the short time I have used them.  I used them extensively last summer and found they are far superior to my lead acid batteries in terms of amount of available storage, ability to be quickly recharged from solar, maintenance, and hopefully longer life. Another benefit is that with the lead acid units I was anal about bringing the charge level back to 100% as soon as I could after use.  The Lithium units are fine setting at almost any charge level.  I haven’t done it nor do I plan to fully discharge and not at least partially recharge them. 


 I winterized my Phoenix in October last year and turned off my battery disconnect switch.  The battery voltage has not dropped at all.  With the lead acid batteries when in storage I would about monthly or so connect to shore power to insure the batteries stayed at 100% state of charge and I would also check water level.  There is no water to be checked in the Lithiums and self discharge is for all practical purposes near zero.


I hope this provides some useful information in your Lithium decision process.

I see the Battle Born LiFePO4s are 12V batteries.  Are 6V Battle Born batteries available?  I wonder if two 6V (if available) would have an advantage as is with wet acid and AGM technology.

I see the Battle Born LiFePO4s are 12V batteries.  Are 6V Battle Born batteries available?  I wonder if two 6V (if available) would have an advantage as is with wet acid and AGM technology.

The Lithium batteries are much more advanced technology.  Old wet acid and AGM technology depend entirely on the battery chemistry to regulate internal current and voltage to each cell.  Lithium utilize a solid state battery management system (BMS) to regulate charging to each individual cell to maximize energy storage.  Lead acid/AGM units when used as two 12 volt connected in parallel both batteries see the same voltage which allows a weaker battery to discharge a stronger battery.  When 2 six volt batteries are connected in series both batteries see exactly the same current minimizing the likelihood one battery will take down the other.


With Lithium when nearing full charge the BMS enters into a cell balancing mode thus each cell as much as possible is brought up to full charge.  The BMS also prevents the battery from being overcharged, over discharged, over and under temperature, etc. which as you know is not regulated by conventional lead acid/AGM batteries but can drastically shorten their life.

Quote from: fandj on February 28, 2022, 06:12:47 am

.....  Typically I saw about 10 amps to zero when fully charged with maximum of about 15 amps. .....

I appreciate the reply and I definitely learned from your posts about your lithium upgrade! 

The Battle Born internal BMS will supposedly shut off charging for under/over temp, current, or voltage.  Since you saw zero amps at times, I'm trying to understand what cut off the charging.  If the alternator just supplies a single voltage, it doesn't seem like it would ever trip the high voltage cutoff of the internal BMS, so the charging from the alternator stopped for some other reason, but it isn't clear to me why.

Also, your comments are interesting regarding the voltage drop for the stock wiring from the alternator.  I've read that a typical LiFePO4 battery internal resistance is about .1 ohm.  Using good old Ohm's law, if the voltage supplied to the batteries after the drop is e.g. 13v, then I=V/R means the battery should receive 130 amps (13/.1).  This would not only exceed the 50% recommendation for a 200Ah battery bank, but also the capacity of the wire.  Even 10ga wire only has a resistance of less than 1 ohm per 1000', so I'm not sure what is keeping your amp draw down to only a max of 15 amps.  Hopefully I'm not dragging this down too far into the weeds, but at some point, I hope the light bulb in my head comes on and I understand this!

Remember the voltage is the difference in alternator and coach battery voltage.  Right or wrong I think of it if both alternator and coach battery are at exactly the same voltage potential there would not be any current flow i.e. I=0.


I am still learning so I welcome any comments where my assumptions are flawed and to help me more fully understand the technology.

......Typically I saw about 10 amps to zero when fully charged with maximum of about 15 amps.  The in-line fuse did not blow at this current......

I appreciate the reply and I definitely learned from your posts about your lithium upgrade!

The Battle Born internal BMS will supposedly shut off charging for under/over temp, current, or voltage.  Since you saw zero amps at times, I'm trying to understand what cut off the charging.  If the alternator just supplies a single voltage, it doesn't seem like it would ever trip the high voltage cutoff of the internal BMS, so the charging from the alternator stopped for some other reason, but it isn't clear to me why.

Also, your comments are interesting regarding the voltage drop for the stock wiring from the alternator.  I've read that a typical LiFePO4 battery internal resistance is about .1 ohm.  Using good old Ohm's law, if the voltage supplied to the batteries after the drop is e.g. 13v, then I=V/R means the battery should receive 130 amps (13/.1).  This would not only exceed the 50% recommendation for a 200Ah battery bank, but also the capacity of the wire.  Even 10ga wire only has a resistance of less than 1 ohm per 1000' (only .01 ohms for a 10' run), so I'm not sure what is keeping your amp draw down to only a max of 15 amps.  Hopefully I'm not dragging this down too far into the weeds, but at some point, I hope the light bulb in my head comes on and I understand this!

Remember the voltage is the difference in alternator and coach battery voltage.  Right or wrong I think of it if both alternator and coach battery are at exactly the same voltage potential there would not be any current flow i.e. I=0.


I am still learning so I welcome any comments where my assumptions are flawed and to help me more fully understand the technology.

Sorry, I corrected my previous post and reposted, so it appears out of order.  I think you hit on a "eureka" moment for me!  It isn't the supplied voltage from the alternator, it is the difference between the alternator and battery voltage!  So, if the alternator is supplying 14.4v at the battery after the drop due to the wiring, and the battery is at 13.4v, then the difference is only 1 volt and the current should be 1/.1, or 10 amps!  I think the light bulb in my head just came on...thanks!

I should have included in my previous posts that it is my understanding that the internal battery management system (BMS) enters into the cell balancing mode when the voltage reaches about 14.2 volts and over charging is prevented at 14.6 volts.

This is the part of the Battle Born blog (BMS post that I linked above) that caused me concern...

"If you only have two batteries in your van, and you’re running a 225 amp alternator, you can potentially pump 225 amps into a battery bank that can’t be charged more than 100 amps. Regulation of those amps must go through a battery-to-battery charger, which we sell from Victron.

It’s important to regulate this current in order to charge the battery properly without shortening the lifespan of your Battle Born Batteries."

I suppose they are referring to a worst-case scenario where your lithium batteries have discharged completely.  I understand that lithium batteries, unlike lead acid, hold their voltage until very late in the discharge cycle so this would be a very rare case, especially if you had shore power, solar, or a generator.

I forgot to mention that the PC factory rep stated the Battle Born batteries should be a drop-in replacement for me.  My coach has a Progressive Dynamics 4575 converter/charger with a lead acid/lithium switch.  Just need to flip the switch to change it to a lithium charge profile.  The Samlex solar charger also has dip switches that allow switching to a lithium profile.   My only hang-up was the alternator charging, and now that makes much more sense to me.

On the 8th of March 1500 hours Pacific Time, I will be doing a presentation on what I did to install my lithium system.  This will be through the Phoenix Cruiser Travel Club (PCTC) Zoom.  Contact information on joining this Zoom event can be accessed through the PCTC website.  It would be great to have all of you attend and share your great advice, experience and expertise. 

I am not an electrical expert but learned much from You Tube, reading online, and from our fellow PC colleagues.   I have now had my system in place for about a year and with no issues.  I faced the same questions:  What lithium batteries do I purchase?  What about the converter in my Parallax system?  What is the size of the alternator installed on my Ford E450?  Do I need a DC/DC charger?   Do I need to disable the existing wiring from the chassis to lithium batteries and how would I do this if I installed a D/C to D/C charger?  How do you wire the D/C to D/C charger from the chassis batteries to the control unit?   Should I change out my solar controller to match the rest of my Victron equipment?  How much is this entire going to cost?  How long will it take me to install and wire my system?  Should I add more solar panels?  What size of solar controller should I purchase?

Again it would be great to have many join me on this Zoom presentation.  If you are unable to join let me know and I can send you my Power Point presentation which shows photos of what I did to install my lithium system.   Feel free to contact me via pm.

Dave

This is the part of the Battle Born blog (BMS post that I linked above) that caused me concern...

"If you only have two batteries in your van, and you’re running a 225 amp alternator, you can potentially pump 225 amps into a battery bank that can’t be charged more than 100 amps. Regulation of those amps must go through a battery-to-battery charger, which we sell from Victron.

It’s important to regulate this current in order to charge the battery properly without shortening the lifespan of your Battle Born Batteries."

I suppose they are referring to a worst-case scenario where your lithium batteries have discharged completely.  I understand that lithium batteries, unlike lead acid, hold their voltage until very late in the discharge cycle so this would be a very rare case, especially if you had shore power, solar, or a generator.

I forgot to mention that the PC factory rep stated the Battle Born batteries should be a drop-in replacement for me.  My coach has a Progressive Dynamics 4575 converter/charger with a lead acid/lithium switch.  Just need to flip the switch to change it to a lithium charge profile.  The Samlex solar charger also has dip switches that allow switching to a lithium profile.   My only hang-up was the alternator charging, and now that makes much more sense to me.

Certainly it is theoretically possible to put very high amps in the battery but from a practical manner using the Phoenix wiring it would be very unlikely.   First if the battery is 80% discharged the battery is still at 12.9 volts so you can see from your calculation wire resistance would limit charging current to about 25 amps.  Secondly, as I recall the inline fuse is rated at 30 amps so this would prevent over current.  I think Phoenix has with their existing system provided various layers of over current protection.  As stated in an earlier post the only drawback I see is charge rate is reduced charge rate with the Phoenix system vs a DC to DC charger.  Even with the charge limiting Lithium batteries still recharge faster than lead acid/AGM using the Phoenix supplied system.


As an old friend once told me “I have already told you more than I know” so I will stop now and listen.

I have a 2021 Ford E-450 chassis and no idea what alternator (three versions listed by Ford and the smallest is 210amp) I have and whether it is a "smart" alternator, vs. regulated.

It’s linked to the VIN. The parts department at any Ford dealership should be able to tell which alternator you have.

I wonder what the battery life expectancy is of Lithium technology.

Our 1st pair in 2007, the original PC-supplied 12V wet acid batteries provided only 2 good years, and 1 marginal year.
Our 2nd pair in 2010, I bought at Walmart were the same.  I tried to get a 4th year from these with bad results.
Our 3rd pair in 2015, are 6V AGM which were installed 7 years ago next month and still have today.  They continued to perform great as of last fall.  I assume they are worthy of yet another RV season.

My current two 6V AGM batteries also hold more reserve power than both sets of 12V wet acid ever did.  I paid twice as much for them, but they are lasting 4 times as long so far, and they offer more 12V power.  The change was a win, win, win, in every category, price per year, longevity, and available power.

I wonder how Lithium batteries would compare to this improvement.

I wonder what the battery life expectancy is of Lithium technology.

This is what Battle Born says about their LiFePO4 batteries... "They are designed to last 3000 – 5000 cycles, at which point the battery will still hold 75 to 80% of its energy capacity."

Quote from: Ron Dittmer on February 28, 2022, 03:47:38 pm

I wonder what the battery life expectancy is of Lithium technology.

This is what Battle Born says about their LiFePO4 batteries... "They are designed to last 3000 – 5000 cycles, at which point the battery will still hold 75 to 80% of its energy capacity."

That sounds "Tremendous".