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Old 04-30-2019, 02:26 PM   #21
Midwestdrifter
 
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

My 200 amp Bosch alternator can supply 100 A at idle in addition to engine loads. If your alternator is at between 13.8-14.1V, is perfectly suited to directly charging a lithium battery pack directly. At that voltage you have no concern of overcharging.
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Old 04-30-2019, 02:58 PM   #22
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

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Originally Posted by Graphite Dave View Post
Why?
Why ask why? OP limiting discussion parameters is perfectly valid, when he wants to discuss comparing other charge source types he can start a new thread.
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Old 04-30-2019, 03:10 PM   #23
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

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Originally Posted by Midwestdrifter View Post
If your alternator is at between 13.-14.1V, is perfectly suited to directly charging a lithium battery pack directly. At that voltage you have no concern of overcharging.
Not true unless there is a BMS capable of regulating charge input, especially the stop-charge termination point. Personally I set that to 3.45Vpc or 13.8V for 4S

And "13.-14.1V"? the latter is 3.53Vpc

At below 3.4V, charging will be slower, and anywhere below 3.35 is practically a Float V.

I do not recommend floating at all if longevity is important, to me losing lifetime cycling is the definition of overcharging.

But if the system design makes it unavoidable during active usage cycling, then below 3.2V is better than higher.
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Old 04-30-2019, 03:36 PM   #24
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

Just a couple of thoughts here from my experience. My rig is a 2016 Sprinter 3500 motorhome using 200 AH of Battle Born 12 volt Lithiums for the house batteries. I ran 1 year with the Battle Born Lithiums so far without any problems. This was with making no modifications to the charging system (i.e. straight drop-in replacement for lead-acid house batteries). The Sprinter charges the house batteries while driving through an Intellitec voltage sensitive control that drives a Cole Hersee 100 amp contactor relay to connect the Sprinter alternator to the Battle Born Lithiums. It is actually connecting both the vehicle battery and house battery together when the alternator is producing current. The Cole Hersee relay is rated at 100 amps. This is the factory design that was fully approved by Mercedes. We often camp with no electric hook ups for 2-3 days at a time. My solar is only a single 100 watt panel which is not much.

I recently purchased the Victron 712 battery monitor so I can see what is actually happening.

I discovered that my Battle Born Lithiums do not get fully charged at any time with the Sprinter alternator system. The highest I have ever seen is 80% using only the vehicle as the charging source. Here is what I observed with the 2016 Sprinter 3.0 diesel alternator: Initially, the alternator voltage starts out between 14.2 and 14.3 volts and it maintains that for a certain period of time (about 20 minutes in my case). The voltage drops gradually to 13.6 to 13.7. Presumably the 'smart' alternator system sees the vehicle battery as fully charged and it will not 'cook' the battery at 14.2 volts. Unfortunately, that is not enough voltage to effectively top off my house lithiums. I often saw only 4 or 5 amps flowing into the lithium house batteries after driving for a while, so my Battle Born lithiums never get fully charged. I was giving up 20% or more of my available capacity with that configuration.

Recently I put in a DC to DC converter specifically designed for lithium house batteries when an AGM or lead-acid vehicle battery is used for engine starting/running purposes. The converter I am using is made by Sterling and it is a 'smart' converter that steps up the vehicle voltage to charge and maintain the Battle Born lithium batteries. It has a lithium profile that fully charges the batteries, allows time for internal cell equalization (cell balancing), and then reduces the voltage to protect the batteries from staying in a continuous over charge condition. Since I have just installed that system, I can not provide a report on how it performs, but all I can say is that it is specifically designed for the application of using a vehicle alternator for charging lithium batteries when the vehicle has a lead-acid or AGM starting/running battery.
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Last edited by hoosierrun; 04-30-2019 at 03:45 PM.
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Old 04-30-2019, 06:59 PM   #25
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

Quote:
Originally Posted by hoosierrun View Post
Just a couple of thoughts here from my experience. My rig is a 2016 Sprinter 3500 motorhome using 200 AH of Battle Born 12 volt Lithiums for the house batteries. I ran 1 year with the Battle Born Lithiums so far without any problems. This was with making no modifications to the charging system (i.e. straight drop-in replacement for lead-acid house batteries). The Sprinter charges the house batteries while driving through an Intellitec voltage sensitive control that drives a Cole Hersee 100 amp contactor relay to connect the Sprinter alternator to the Battle Born Lithiums. It is actually connecting both the vehicle battery and house battery together when the alternator is producing current. The Cole Hersee relay is rated at 100 amps. This is the factory design that was fully approved by Mercedes. We often camp with no electric hook ups for 2-3 days at a time. My solar is only a single 100 watt panel which is not much.

I recently purchased the Victron 712 battery monitor so I can see what is actually happening.

I discovered that my Battle Born Lithiums do not get fully charged at any time with the Sprinter alternator system. The highest I have ever seen is 80% using only the vehicle as the charging source. Here is what I observed with the 2016 Sprinter 3.0 diesel alternator: Initially, the alternator voltage starts out between 14.2 and 14.3 volts and it maintains that for a certain period of time (about 20 minutes in my case). The voltage drops gradually to 13.6 to 13.7. Presumably the 'smart' alternator system sees the vehicle battery as fully charged and it will not 'cook' the battery at 14.2 volts. Unfortunately, that is not enough voltage to effectively top off my house lithiums. I often saw only 4 or 5 amps flowing into the lithium house batteries after driving for a while, so my Battle Born lithiums never get fully charged. I was giving up 20% or more of my available capacity with that configuration.

Recently I put in a DC to DC converter specifically designed for lithium house batteries when an AGM or lead-acid vehicle battery is used for engine starting/running purposes. The converter I am using is made by Sterling and it is a 'smart' converter that steps up the vehicle voltage to charge and maintain the Battle Born lithium batteries. It has a lithium profile that fully charges the batteries, allows time for internal cell equalization (cell balancing), and then reduces the voltage to protect the batteries from staying in a continuous over charge condition. Since I have just installed that system, I can not provide a report on how it performs, but all I can say is that it is specifically designed for the application of using a vehicle alternator for charging lithium batteries when the vehicle has a lead-acid or AGM starting/running battery.
Thanks. That's part of why I would plan to use a DC/DC charger/converter.
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Old 04-30-2019, 07:01 PM   #26
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

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Originally Posted by markxengineering View Post
I will second this, using a 50 amp kisae b2b charger, 50 (well maybe 48) amps at idle is no problem for 150 amp sprinter alternator.
Excellent.

If you end up needing more out of the alternator, a smaller pulley might be something to look into. The output of an alternator is very non-linear with large gains for very small RPM increases near idle.[/QUOTE]

Yes, I am aware of that.
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Old 04-30-2019, 07:04 PM   #27
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

Quote:
Originally Posted by HarryN View Post
The typical consumer available LiFe battery that is discussed on forums like this should be thought of as charge / discharge rates of about 500 watts per battery. (example BB 100 amp-hr or similar).

This is a separate number from what the van's electrical system can provide for feeding into the appropriate charger to manage the power transfer, but it helps when determining component sizing.
Yes, and that's why I started with the alternator and worked backwards on this idea.

Quote:
It is helpful in matching battery capacity with inverter demand as well. A 2 kW inverter really needs at least:

( 2000 watts inverter ) / (500 watts per battery) = 4 batteries.

Which is exactly why our units are sized this way.

A 2 kW class system is roughly equivalent to one kitchen outlet in a home.
Wow, that's a good point.
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Old 04-30-2019, 07:07 PM   #28
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

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Originally Posted by HarryN View Post
A somewhat more accurate description of LiFe vs AGM is that the AGM needs to be regularly fully recharged, while the LiFe bank is fairly tolerant of being only partially charged.

Good quality AGMs tend to be more tolerant of abusive charge / discharge rates than LiFe.
Thanks, Harry.

We plan to control the charge rate with the DC/DC charger- we're not just gonna hook this up to the alternator with a solenoid.

And we're not gonna be running microwaves and hairdryers off of a giant inverter either.
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Old 04-30-2019, 07:08 PM   #29
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

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Originally Posted by john61ct View Post
LFP has **zero** need to ever go anywhere near Full, and sitting there is harmful.

LFP has no problem with C rates **much** higher than AGM. If you use the maximum C rates AGM can accept, that is gentle usage for LFP and great for longevity.
Yes, and that would allow me to use a larger DC/DC charger to cut down on the amount of time that I have to run the engine to recharge.
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Old 04-30-2019, 07:25 PM   #30
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Default Re: Single alternator, 12VDC/12VDC charger and and LiFePO4 battery ONLY?

Quote:
Originally Posted by Graphite Dave View Post
Why?
A number of reasons.

As I stated before, if I take the money that I would have spent on a solar system feeding AGM batteries, I could then afford to upgrade to LiFePO4, and since LiFePO4 can be recharged much faster than AGM, that makes the alternator a more viable power source, because I would be able to use a larger DC/DC charger, allowing me to run the engine less to recharge.

Plus, it's much simpler.

And as one aspect of that simplicity, there would be fewer holes in the van's body, because I wouldn't be having to run wires from the solar panels on the roof, through the van's body, into the interior. One (or two) less things to keep from leaking when it rains.

Solar panels spell camper van, so no solar makes stealth camping easier.

Solar panels create heat. I don't want extra heat.

Solar panel output drops to just about zero if even a little portion of the solar panel is shaded. A leaf could keep my batteries from recharging if we are away from the van for the day. So could shade from any buildings, trees, utility poles, flag poles, etc.- we don't always get to pick the best parking spots. And then there's the shade caused by roof vents, 4G booster antenna, and/or anything else.

Solar panels make roof cleaning more difficult.

Then there's the challenges of being at the mercy of sunlight in order to recharge. Solar panels work best in the sun, so spending time in places where the sun doesn't shine very much, would have us looking for yet another way to obtain electrical power. Solar panels mounted flat on the roof, produce less power at higher latitudes. We'd like to explore the entire continental U.S.

The purpose of this thread is to explore exactly what I said in the first post. If you want, we could have another thread to explore solar.
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