Charging Lithium house battery using alternator. Will it work?

[a57oval]

Hello,

We have a 2.5 Subaru with a Subarugears 5 speed, a 2011 Outback 130 amp alternator and a lead acid car battery. We want to add a house battery to support an Espar B4 heater, a Truck Fridge TF49 (DC only), as well as some LED lights, a tablet, and cell phones. This is a new build, so we can do whatever makes sense.

Generally we camp for two weeks at a time and take day trips to and from the camp spot. We do not want to "hook up". We also would prefer not to carry solar panels. So we were thinking of using the alternator to charge the car and house battery.

I have done some reading on batteries and it seems like a lithium battery would be a good solution for us because of the longer life, greater discharge ability, and lighter weight.

But I am having a difficult time finding out some details:
With a lead acid "car" battery and a Lithium "house" how do I separate the two? Do I need to?
Can't I charge a lithium at a much faster rate and not have to worry about the several hours of Float charge to make the lead acid happy? For example, charge a 100 AH lithium in 1 hr. with a 100 amp alternator minus small wiring losses.
If I charge the Lithium via my alternator is the alternator running at 100% output until the lithium is happy? Doesn't that drastically shorten the alternator life? Again how do I charge a lithium to a specified voltage and charge the lead acid to a different specified value? It is my understanding that lithium likes to be charged to a higher value than the lead acid. Is this wrong?

I also have room to mount a second alternator if that makes things cleaner.

Needles to say I don't understand a lot of this and can't seem to find information on how to do this. Any advice or pointers would be appreciated.

Peter

[Wildthings]

I would think that the two batteries would be in conflict with each other if you tried to do a fast charge. You might come up with a way to isolate the starter battery while changing the lithium one. A 130 amp alternator should be pretty happy at 100 amps, giving a call to the manufacturer or someone with a lot of alternator experience should be able to get you a better answer.

[danfromsyr]

not saying my install is right, as every one has a different opinion on battery set ups.
but in my van I run a starting battery and 2 deep cycles all in parallel
have done this for 15years. get about 5-7 years from a set.

I'd suggest an Isolator on the starting battery, but I've yet to do such.

I run a 12v only dorm fridge, and a propex for when it's cold..
I can go about 3-4 days till it's weak to start in hot 90's temps. the fridge is a juice hog.

the benefit is it's cheap, it's maintainable, it's replaceable on the road, and it's not volatile

prefer to spend my $$ on other ventures that have a better ROI.
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[davevickery]

I don't know much about this but I had similar questions. I'm using AGM batteries and a manual switch and an on board charger for topping off at home. The cost of the Lithium iron is so high that it isn't something I would ever seriously consider anyway.

[MarkWard]

I had a Lithium battery in my racecar. It did not last. Seems the combination of charging it off an alternator and a battery tender killed it less than a year. Turns out the charging method for this brand was specific. I believe it was a Lithium Pro. That was some years ago. I use AGM batteries for both and have a manual battery combine isolate switch from the marine industry.
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☮️

[Kkinsch]

You may want to reach out to http://www.offthegridcamper.com. I have no affiliation with him, but I've seen what they're doing with LifePo4 systems for Sprinters and it looks pretty impressive.

I think they used to have a Westy but switched to a better platform for a mobile workshop recently.

[jimf909]

I agree that this question may be better directed to a gang that thinks about Lion batteries more than they think about 30 year old cars.

My question is why don’t you want to include solar panels in the system? They allow you to isolate the house and car systems, allow you to not have to turn on the noisy ICE to charge batteries and are just plain nice. A second alternator sounds more complex than adding solar.

Also, while Lion is super attractive, it seems that the battery is more expensive than AGM batteries plus solar. I’m looking forward to lower cost Lion batts.

Keep puzzling! It’s a fun part of these rigs.
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- Jim

[Abscate]

You’re loads and charge capabilities Aren’t going to work out with. 100 Ahour battery and alternator charging over two weeks. You will have to supplement this system somehow, probably easiest with a small generator
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.ssS!

[shagginwagon83]

My friend has a LiPo in his van. He uses a Victron Cyrix li ct with a Stark 125aH battery. He can see info on his smartphone. I think he sees like 50 amps going into his lithium with his Subaru 2.5. He took it on a 2 week camping trip and his family of 3 people total only cycled the battery like 6 times. The main thing with the alternator is overcharging the lipo. Most lipo's have internal circuitry to protect against such.
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[Pcforno]

An alternator is actually perfect to charge Li batteries with as it puts out a nice 14V. Just use a battery separator that has a connection to the key on power so that when the car is running the house and starter batteries are combined and off when not. There’s nothing really complicated about it. When the alternator is on, the whole electrical system is combined and the house and starter recharge at 13-14V and when the van is not running the house stays at its 13-14 V nominal charge whilst the starter floats for a while then returns to 12V.
Your alternator is not going to blow up or anything. It will slowly charge as the diode allows it to. I’ve run LIPO house with flooded lead acid starter for 3-4 years with zero problems.

[PDXWesty]

I just googled “lipo rv batteries” and came up with a ton of information on people who have made the switch.

https://www.lithiumion-batteries.com/lithium-rv-deep-cycle.php

Looks like you could use a battery with built in protection and set up your system with a normal battery isolator like blue seas or yandina and make it work just fine. Seems high priced though at $1200 for a battery. If something goes wrong it’s an expensive mistake. A $200 flexible solar panel could get you to the same storage with a standard deep cycle.
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89 Westy 2.1 Auto

[Steve Arndt]

Vanagain just posted a fancy Li battery they sell, and they recommend this for it:

https://www.vanagain.com/shop/dual-input-25a-in-vehicle-dc-battery-charger
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Steve
Steve's 87 Syncro project

[kenwilfy]

Thanks for letting folks know about this Steve. Here is a short video that I did recently talking about the Lithium Battery into a Vanagon and also the charger.
Link

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Thanks,
Ken Wilford
John 3:16
www.vanagain.com
856-327-4936

[shagginwagon83]

Yeah but that unit doesn't charge the batteries through the alternators power right??

Edit: maybe it does. Video says "you charge your secondary battery through main battery" I hope thats only when engine is running.

If it were me (and im going to when my deep cycle dies), I'm investing in a Victron 712 with a shunt (so you can have a battery % and see actual amperage usage) and a Victron LI-CT to be the 'relay' when alternator is running.

I'll see if my friend can post his wiring diagram here. He did a lot of research on this.
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Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[ntaramorris]

Hi, a57Oval. Your right there isn't much complete info on using a LiFeP04 as an aux battery and multiple charging applications. As Shagginwagon83 says, I have completed the install of a Lithium set up in April. I previously had an aged Lead Acid AGM and went for a total re-wire and install of my Aux batt system to get to a LiFeP04 set up. My experience with the set up since the install is pretty awesome. I actually power a T-49 truck fridge in addition to a Dometic 65Qt fridge form the 125AH LiFeP04 Aux battery. I charge via solar, alternator or designated LiFeP04 charger. Lithium batteries like constant current , constant voltage. Using products from Victron energy to create a system works well. Their Cyrix LI series offer a range of combiners / isolators for Lithium set ups.

The wiring diagram below shows how my system is set up. Credit goes to OTGcamper for his review and guidance on the use of the Cyrix-Li-CT.

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"Bruce Vanner" aka: The Incredible Hulk
88 Westy 2.5 Subaru

[kenwilfy]

The Redarc system is another way to go. That is what we have chosen for our systems and they work very well and are simple to set up. Take a look at this overview video on how they work. It combines the battery isolator, battery charger for the lithium, and a solar controller all into one compact unit that is affordable. Made in Australia too. We sell them on our site and I recommend them to our customers who buy Lithium Batteries.

Link

_________________
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
856-327-4936

[shagginwagon83]

Does the Redarc have a maximum charging amperage of 25A when engine is running? Or is that max solar charging amps of 25a?
_________________
Brandon
"Jo Ann" - '83.5 Westfalia EJ22e w/Peloquin
Instagram @joannthevan

[kenwilfy]

There are two different versions of the Redarc and we sell both on the site. 25 amp and 40 amp. However I really recommend the 25 amp version for the Vanagon because your alternator is 90 amps. If you had a Subaru with a higher amperage alternator then maybe the 40 amp would work. I was watching the charging in real time with a meter and 25 amps is the max, or normally it is less than that depending on what state the battery is in. It prefers the solar panel if you have one installed.
_________________
Thanks,
Ken Wilford
John 3:16
www.vanagain.com
856-327-4936

[DuncanS]

There is a lot of good info here. Kinna interesting that a57Oval hasn't responded to any of the posts. So I'm going to direct this to you.

Don't do it!!! It takes a huge amount of savvy to do this and get it right. Judging by your question, this seems like it might be beyond your skill set. Getting the correct charging protocol for LiPo's can't happen with the set-up you have. It takes a special chip controlled apparatus to make sure that they get what they want. They are finicky and deviating from their requirements will cause problems. My son is an electrical model airplane expert and the batteries they use are similar to what your are considering. Up until recently, pilots weren't allowed on the field unless they had 50 cal ammo boxes or the equivalent to put the batteries in while charging because of fire and explosion issues. This requirement has only disappeared because of the new very sophisticated charging equipment now available.

I have a cruising sailboat that has a ton of 12vdc requirements. I mention sail, because unlike a power boat, we can go days without running the engine. I have four 95 amp hour deep cycle batteries. I recommend you go with deep cycle with the latest in marine technology to keep them happy. It's not cheap and they require constant monitoring. House batteries are definitely not like the starting battery where you buy it and forget it. You want to pick the equipment that requires a load and think carefully if the convenience of the device is worth the inconvenience of supplying it with juice. The more you have on board, the greater the number of things to go wrong and ruin your trip. It's called camping, after all .

[mugford]

Nice diagram ntaramorris, I'm putting together something similar.

Are you missing a ground connection on your aux battery, after the shunt?
Not seeing how the alternator could energize the aux batt otherwise.