Is B-B charger for Lifepo4 lithium batteries needed?

Stage 2 is necessary in both chemistries to bring the battery to 100% SOC. ... In long-term storage applications, a lithium battery should not be stored at 100% SOC, and therefore can be maintained with a full cycle (charged and discharged) once every 6 – 12 months to 30% – 70% SOC.

https://www.power-sonic.com/blog/how-to-charge-lithium-iron-phosphate-lifepo4-batteries/

SV K.

Thanks for the information--please don't get weary.

As far as dc to DC (b to b) charging the idea is to protect the alternator.

When the battery maker for these (expensive) items says 14.6 to charge, they don't mean 14. Ignore them at your peril.

However LI don't "like" to be taken to 100% state of charge. Apparently it reduces the (large) lifespan.


Uh..no

Just spoke with my retailer who has been involved with electrical vehicles and Lifepo4 for many years to verify my understanding before posting it.

First my cells are rated at 3000 cycles from 100% to 20%SOC.

That cycle count uses 14.6v as the top charge.

Now let’s say I’d like to increase my cycles beyond the 3000.

Then I can/should use 14.0v/14.1v/13.9v or an amount less than 14.6v as the top charge voltage.
Additionally I can/should discharge to an amount around 30%SOC.

There is no “Peril” there is no “don’t “”like””.

Not sure what this has to do with B to B, but I have grown weary of erroneous statements and wanted to straighten this out.

Hi,

When the battery maker for these (expensive) items says 14.6 to charge, they don't mean 14. Ignore them at your peril.

However LI don't "like" to be taken to 100% state of charge. Apparently it reduces the (large) lifespan.

Duel post, sorry.

RLS7201 wrote:
Grover, I believe you're on the right track if your new batteries have a built in charge controller. As far as alternators not being able to fully charge house batteries, that's non-¢. A steady charge at 14 volts for a full day of driving will fully charge lead/acid house batteries. If you are concerned about over heating you alternator with Li batteries, why not put a temperature sensor on the alternator before and after the battery change and see what happens. I see so much hype about burning out alternators but no solid evidence.

Richard

This is true. Your engine control computer, or what ever you want to call it, is what is controlling the alternator output by battery voltage over time. I believe this is being over-though. Lithium biased batteries have a max. discharge and charge rate, in amps. Exceeding either will damage or destroy them. Its your money, you seem to have a grasp on realty. Make your choice biased on you knowledge.

Groover,

It is going to be a LOT hotter under the hood than the open air situation of the Victron (flawed) testing platform.

Do as you think best--but I'd use a dc to DC device to get the voltage right and to limit the load to the alternator.

Sent PM

pianotuna wrote:

RLS7201 wrote:
Grover, I believe you're on the right track if your new batteries have a built in charge controller. As far as alternators not being able to fully charge house batteries, that's non-¢. A steady charge at 14 volts for a full day of driving will fully charge lead/acid house batteries. If you are concerned about over heating you alternator with Li batteries, why not put a temperature sensor on the alternator before and after the battery change and see what happens. I see so much hype about burning out alternators but no solid evidence.

Richard

1. 14 volts will NOT fully charge a lead acid battery in a full day of driving. It is unlikely unless there is a dedicated alternator that 14 is available for the entire day.

2. Victron has a different opinion that yours on burning out an alternator.

https://www.victronenergy.com/blog/2019/10/07/careful-alternator-charging-lithium/

While I have a lot of respect for Victron two things about this test three things about this test jump out at me.

1) I have never seen with a pulley more than half the size of the crankshaft pulley, meaning that automotive alternators typically turn at more than twice as fast as the engine and therefore get better cooling than what is being demonstrated in the video.

2) I have no idea what this alternator was designed for and whether it has anything in common with the one in my coach. I would hope that Freightliner and Cummins know that when putting an alternator into a motorhome chassis it will be expected to charge both engine batteries and a bank of house batteries simultaneously and take adequate protection for this.

3) As good as Victron is I know that they are trying to sell something.

I am not trying to fully charge the house batteries anyway. I am just trying to keep them moderately charged then either plug in somewhere or run the generator if needed to top them off before a long stay. As the video points out alternators are not extremely efficient anyway and putting an additional widget in the line would further reduce that efficiency.

One of my first camping trips in the coach was boondocking and the generator failed. Since the rig was so knew I called Cummins for advice and they told me to run the engine as needed to keep the house batteries charged. Just avoid going over 12 hours total to avoid damaging the particulate filter.

I know that there are some people out there running LiFe batteries in their coach and I would like to hear about their personal experience.

Hello Groover,

I’ve been running Lifepo4’s for 7 years and have helped friends install or been involved with the install of various other Lifepo4 systems for the last 6 years. Below will be the things we have learned in that time. In other words “real world experience” which is I think what you are after.

The first argument for the B-B charger is that it helps prevent alternator burnout from overload. I am thinking that a class A with a significant house battery pack of any sort should be prepared for a heavy load and that this reason doesn't really apply to newer class A's. Besides being expensive the B-B charger reduces efficiency and impedes charging, at least up to the voltage that the alternator produces.

On Coach #1- I installed Po4’s for the house and left the couple year old AGM’s for the chassis. Installed a Balmer programmable regulator to de-rate the “alternator” by half to avoid burnout. Set the “alternator” to the suggested charge profile for the Po4’s. All good. 7 years later both the AGM’s and the Po4’s are doing fine. Of note is that we played around will all types of various charge profiles and they all worked, additionally this coach has been used full time with over half of that time boondocking and they drive it 10k miles each year.

Coaches #2 and #3- Same as coach #1. Doing fine.

Coach #4- Used existing “alternator” controlled by 25yr. old original external controller. Doing fine 4 years later. BUT, these coaches, except for #3, all have oil cooled “alternators” or as my friend corrected me we actually have “generators”. The owner of this coach told me he just starts it up and the alt/gen pumps out 250amps, the PO4’s fill up and the current backs off.

Coach #5- Used air-cooled alternator with original internal regulator. He installed dash mounted switch allowing him to turn alt. on and off manually every 15 minutes or so to avoid over heating it. Well, he forgot to turn it off once and the alt. did indeed burnout.

Coach #6- Just finished Po’4 install and I am thinking I’ll go the DC-DC charger route. In the overall scheme of things it is not that large an expense and I like the simplicity.

The second argument for the B-B charger is that the engine alternator will not fully charge the lithium battery. I don't expect that to be an issue very often and if it looks like it may be an issue I can always fire up the generator and use its charger to top of the lithium batteries. In the summer it will probably be running anyway plus the solar panels that I plan to install will have a controller that will allow a full charge.

Hmmm…well they are plenty full for us. I have set various controllers to all types of voltages and they never fail to fill up the Po4’s. You guys got me thinking so I’ll set my solar to 14.0v today and see if it fills’m to the top. There is no need to fill Po4’s to the top though. The only “need” to do so is if you need those last few amps to get you thru till the next charge.

Hope this helps.