TheSamba.com :: View topic - Charging Lithium house battery using alternator. Will it work?

Tue Jun 26, 2018 4:00 pm

DuncanS wrote:
Don't do it!!! It takes a huge amount of savvy to do this and get it right.

That may be the case if you are building your own battery system from the ground up with bare cells. But what about the products that are engineered to be direct replacements for RV batteries? They have the built in charging circuitry and protection and claim to be plug and play.

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

Tue Jun 26, 2018 4:26 pm

Hmmm... looks like SmartBattery does not have many happy customers. 76 complaints and an "F" rating with the BBB.

It would be an awesome alternative to lead acid with a 100% discharge rate, though...

Tue Jun 26, 2018 4:56 pm

izzydog wrote: Hmmm... looks like SmartBattery does not have many happy customers. 76 complaints and an "F" rating with the BBB.

It would be an awesome alternative to lead acid with a 100% discharge rate, though...

There are other similar products. That's just one brand.

https://greenlifebattery.com/products/

https://www.bioennopower.com/

https://battlebornbatteries.com/

https://relionbattery.com/products/lithium/application/recreational-vehicles

I have no experience with any of them. Just doing a search.

Tue Jun 26, 2018 6:58 pm

Thanks.

I'd really love to hear some real-world users weigh in on these. For instance, what's the usage/depletion ratio compared to lead-acid? Is an 80AH lithium the equivalent of a 120AH lead acid when you consider deeper discharge and faster charge times for the lithium?

I'm thinking of replacing my 100AH lead acid with a 150AH lead acid, which would mean reconfiguring my under-seat set up for the bigger 150AH battery. A 100AH lithium would drop right in the same space and weigh 55 lbs less!

Wed Jun 27, 2018 3:05 am

The most reliable start/house battery marine systems use a dual separate circuit. The standard engine mounted alternator is left alone with it's start battery voltage controller which is designed for the wet cell. Hands off and forget it. Start and go. Then a second alternator is added which is dedicated to the house batteries. They can be wet cell, AGM or LiPo's or whatever you want. This circuit has all the necessary control circuitry to deal with the specialized batteries they are feeding. So there is no manual switch over or battery combiner with a complicated solid-state mechanism to deal with different batteries. ntaramorris has a good diagram, but I don't see the mechanism that changes the alternator output to exactly what the LiPo's need with all the feed back requirements to insure safe and fast charging for the house circuit. The Cyrix is a battery combiner only, not a smart voltage and amperage controller that can discern the differences required between the different styles of batteries.

Wed Jun 27, 2018 6:47 am

Mugford, Thanks for finding this. Whoops on the diagram! You are correct and that is physically how I am wired. Its corrected now on my original post.

izzydog et all:

I purchased a "deep cell" lithium battery from Stark Power that has a built in BMS. (www.StarkPower.com).

I have been using this LiFeP04 battery:

- The output voltage is way more consistent (running a cpap very successfully that is sensitive to what is thinks is low voltage). LA / AGM has a more noticeable drop in voltage as you use power. This is known as peukert effect.

- I can draw down the battery more than 50% ( the recommended not to exceed use of a Lead Acid batt) and not worry about its lifespan. I go down to 20%. Given this theory of not to exceed 50% is how you can add to your requirements for battery size and Ah needs. My 125 Ah battery weighs 34.2 lbs. That's remarkable!

- The recharging of the LiFeP04 is super fast especially from a shot in the arm from the alternator or AC charger. It has a higher efficiency in taking a charge.

LA / AGM cells will self discharge over time and need a trickle maintenance charge to stay healthy during storage. LiFePO4 cells can sit for many months without losing charge. Storage is generally recommended around 60% charge.

I wont go back to an LA / AGM battery for an Aux battery ever. Not after experiencing the LiFeP04 battery set up in my Van.

Should everyone switch to LiFeP04 batteries today? Probably not for at least these 2 reasons.
1. They are expensive right now. Yes you can factor lifespan into the cost savings but will you keep your van long enough or use the aux batt enough to realize this?

2. They don't like to take a charge below 32 deg. Fahrenheit. What ever you design for the implementation you must take this into account. Some batteries have a BMS that auto protects from charging. I believe in a multi system protection where possible.

3. Your system should be designed specifically for LiFEP04 in mind. If your re-working a set up like I did, you need to evaluate it and all its components. This can be expensive if things like your charger and Solar controller don't have profiles for a LiFeP04 battery and need to be replaced.

Wed Jun 27, 2018 7:45 am

Sorry for taking so long to respond. There is a lot of great info here and it's taking me a bit to process. FWIW, I am not planning to build a battery but buy one. The 125AH from StarkPower is appealing because it is the same size as the 100AH batteries from other retailers. All of these batteries have a BMS in them which is why I am confused as to why I would need anything else between it and the alternator if I don't have any other input sources such as solar or shore power. Thank you for all the responses. Ntaramorris, the diagram is very helpful.

Wed Jun 27, 2018 8:06 am

(Opinions ahead)...For me, it's just so hard to justify that price of $1200. If you need 100AH why should it matter what the source is? (except for weight). I've been getting 5 years out of my 100 AH deep cycle lead acid batteries for around $170. It's not like you get more power from a Li battery, it's just a smaller package. It's still 100AH. I realize there are other benefits, but I could buy a new battery every year for what the Li batteries cost right now and still be ahead of the game. From an economic standpoint it can't be justified. If you want to have the coolest package out there, then you certainly are paying for image.

Wed Jun 27, 2018 8:16 am

I’ve recently installed (2)two 100ah Lithium batteries along with a new MPPT Lithium solar controller and a Genius Lithium charger to my Westfalia. It was expensive but I like the weight savings and added power storage. I also set mine up so that if I don’t get enough solar power charge from my (2)two 100w panels I can flip a switch and the alternator will charge my house bank of Lithiums.

It’s only money. :wink:

Thu Jun 28, 2018 10:18 am

I've been keeping a tally on price/performance for various lithium batteries from various vendors. PM me if you'd like a copy or host it on Google Docs or whathaveyou...

Thu Jun 28, 2018 11:29 am

I used 2 100 ah LiFePo batteries from Battleborn. The capacity is enormous and I could have gone with one 100 ah battery, but when in doubt, belt and suspenders. I’m just now getting around to re-installing my solar panels and decided against an alternator connection, since my panels will constantly charge the battery bank and an ACR means more cabling, electronics, space and weight. I did install and onboard charger, which I use to top off the bank before I leave on a trip. I’m delighted with how it turned out and my wife (who rarely stops working) is even happier to be able to power her laptop and anything else.

Battleborn was helpful, though my best source of quality information on RV solar systems was AM Solar in Oregon. Having a built-in battery management system is much cleaner than the external variety and has worked well so far. I worked very slowly and methodically through my design and build process, which was helpful, since I don’t do this sort of thing for a living.

I’ve been pretty impressed with some of the systems I’ve seen here. When I was contemplating an ACR, the Samba was very helpful.

Fri Jun 29, 2018 6:15 am

Ntaramorris - I really like your system. Seems like I could do something very similar without the solar and charger.

Can you tell me what size is your alternator? How fast will it charge the LiFePO4 battery? Do you limit the charge current the alternator throws at it?

Also, I am a bit confused by the use of the Victron BMS 712. The StarkPower 125AH battery has an internal BMS and also has BT capability for monitoring. Can you please tell me what functionality the Victron BMS provides?

Thanks to all who have contributed. This does look possible, just gotta figure out how.
Peter

Fri Jun 29, 2018 9:07 am

a57oval,
I run a 110 amp Subaru Alternator and upgraded the wiring from its top post to the starter post. Ensured existing wire to start battery was in good shape by visual inspection of connections and measuring out put at alternator compared to measurement at battery post. Charging the battery from a 60% SOC takes under 2 hrs roughly ( I think its much faster than this but am answering conservatively). I have observed on the phone app up to 80Amps charging the LiFeP04 battery. It tapers as the battery charges up. The combination of the Start battery and the Aux battery is key to everything staying healthy.

I have created a strawman wiring diagram for Alternator only charging and using the LiFeBlue battery. (use at your own risk as I make no claims if being a pro!)

A few words on this compared to my set up with the BMV 712 and Stark power Battery.

I found in speaking with StarkPower that their BMS does not protect from freezing temp charging. (As of 4-1-2018) They were hoping the next round of BMS logic would. The literature says it will and its a version ahead. I still choose StarkPower as I live very near by and I knew I could deploy the Victron BMV 712 to control the Cyrix. The BMV also uses bluetooth to not only provide stats on your smart phone but to also communicate with the Victon smart solar series of MPPT controllers to create a "system". The Stark battery has a phone app that has nearly the same interface as the LifeBlue- They both originate from China so, no surprise there.

All that stated for a more simplified approach I suggest the LifeBlue with the Cyrix Li-CT. (read the data specs from Victron)
The phone App will give you the stats on the battery.

Here are some pics of my install. Some are in-progress and don't reflect the final completion. i.e. Aux Battery is laying in place in the under floor storage and pic doesn't show its aluminum hold down strap.

I run both the Dometic Fridge 65Qt as well as TF-49 Fridge. Family of 3 and we eat and drink a lot! LifeProof flooring was a very inexpensive addition.

Just so I have said it.....Wiring is serious business and isn't a place to save a buck or two. Buy good supplies and take your time. Double check everything including any wiring advice you get or diagrams like mine. I am not a pro. Use at your own risk.

A great option for those not wanting to do this themselves is Cameron Belscher (OTG Camper on Insta). He has done many many setups form VW vans to Sprinters etc. He is smart and is a pro.

Fri Jun 29, 2018 10:04 am

I'll add a few general thoughts to consider...

1. I'd listen to and trust Kenwilfy, a fine guy, great vendor, and all-around Westy Guru;

2. No battery likes constant discharging. The limits vary per type, but keeping a high charge saves batteries.

3. Per 2, using only a single 100aH as a house system is barely enough to keep up at a decent charge, even with a panel. What about clouds?

4. Charging extra batteries with an alternator means going through alternators quicker, and if all the batteries match in type everything works better and lasts longer. Ours did until we reallocated our AGM starter battery to a second house battery and put a lead acid in as a starter battery.

5. A second alternator dedicated to house batteries strikes me as ideal -- but not justified if your style is to drive to a place and park, i.e., not driving every day. Without question, we have found the shorter-life alternator route to be the least of our worries and we carry a spare -- with a pulley mounted. There's nothing better than pulling into a site and having a full charge of 12.8 volts or so, and few things are worse than begging the sun to come out because you didn't charge while you drive.

6. You must use a good isolator, too. In our 59 months of full-time, and maybe 800 of those days working on a laptop and second monitor all day, I highly recommend charging all batteries with an alternator, and the bigger, the better.

7. Keep it simple, the more parts the more issues... and losing your capabilities in the MoN when you need it to work just plain sucks.

8. I would absolutely love a lithium and may go down that road when they cost double instead of six-fold. They have advantages I am told, but the *only* reason I could justify one is if we were hundreds of lbs. over GVWR and desperate to lose weight.

9. Whatever one does, to minimize Westy lean I would highly recommend doing what we didn't when installing vendors didn't think it through enough... mount the batteries under the bench instead of under the sink to move weight rightwards and rearwards, and consider a single, 240aH battery of the size unknown to me by name but lower and lighter and more-powerful than two 100ah Group 31s. The issue with two batteries is the lesser-cold cranking amp one always drags the other one down and longevity and performance is compromised throughout their lives.

Fri Jun 29, 2018 11:00 am

I've got the Victron 712 and their solar charger as well (75 |15) along with their BT interfaces. Its a nice system but I'm not seeing their 'network' capabilities yet since the Victron app has to connect with the devices separately even though I've created the 'network' in the UI. So if you want to view the starter battery level you have to go to the 712 UI, the solar output is on the other device. I'd like to have the app connected continuously to them but thats probably more of a function of how I use my tablet. The disconnections are irritating. The Victron batteries, the most expensive ones in terms of Wh/$, tie into the system as well. Debating whether they are actually that much better than the rest...

Fri Jun 29, 2018 11:04 am

^^^ Perfect demonstration of why I recommended keeping it simple ^^^

Fri Jun 29, 2018 11:08 am

Knowledge is power - but, applying knowledge is more powerful.

Fri Jun 29, 2018 11:42 am

Yet neither is as powerful as clear communication everyone can understand. 8)

Wed Jun 19, 2019 10:35 am

I am about to add an aux battery to my camper under the drivers seat. I will be using the alternator for charging for now and see if I need solar later. Is it the consensus that the wire from the starter to the aux battery should be upgraded to something beefier like 4 gauge? If so, how are folks running this wire? I saw someone running it externally along the carpet, but seems like there must be a more concealed way of doing this.

Thanks,

Wed Jun 19, 2019 11:38 am

DeLvxe wrote: I am about to add an aux battery to my camper under the drivers seat. I will be using the alternator for charging for now and see if I need solar later. Is it the consensus that the wire from the starter to the aux battery should be upgraded to something beefier like 4 gauge? If so, how are folks running this wire? I saw someone running it externally along the carpet, but seems like there must be a more concealed way of doing this.

Thanks,

You don't need to run a wire from the alternator to the aux battery. You can upgrade the wire from the alternator to the starter with an 8ga or add a second wire in this location. Typically the second battery is connected to the starter battery with an isolator. The cable from the starter to the main battery can carry enough current to adequately charge both batteries.