Charging a lithium house battery

[Jeremy]

I've just been reading belfert's battery-or-generator thread, and the comments from windtrader and others about building a lithium house battery got me thinking.

I've some limited experience of building lithium packs as I've got a 36v lithium pack in my electric bike which I built myself from new-old-stock laptop batteries bought cheaply on Ebay. I've also watched Youtube videos of people building much larger Tesla Powerwall-type packs for their homes - so I've got an idea of what's involved and would have no fears about building a large capacity 24v pack for my bus, and I know that it could be done fairly cheaply and would greatly out-perform the existing lead-acid batteries

My question though is how you'd charge a lithium pack in the bus:- obviously the pack itself would have it's own BMS, but you'd still need a charger designed for lithium cells, and my existing Trace inverter-charger definitely isn't - and since that's an expensive bit of kit I'm not about to throw it away to replace it with something else

So my question is - is there some other work-around here? Perhaps some device that sits between the Trace and the lithium pack that will enable it to be charged safely without burning the bus to the ground?

Jeremy

[belfert]

How about turning off the charger in the inverter and using a quality charger like a Victron that can deal with lithium batteries?  You would want the charger to only get power when the generator is running, or on shore power.

[peterbylt]

In the Lifepo4 battery system I am building I will using the Electrodacus SBMS0.

https://electrodacus.com/

One of the issues I have is an outdated Aims Inverter/Charger, like you, this is an expensive piece that I don't want to rebuy if I don't have to.

The SBMS0 is an interesting piece of hardware that functions as a BMS, Solar Charge controller, Inverter and charger controller and wants to be in charge of any charge or drain on the system.

Due to the age of the AIMS PICOGLF30W24V120VR it does not have a lithium charging selection.

There is a rotary dip switch for the charging selections including an off selection.

I contacted AIMS and was told the Lead Acid selection (#4) would be best for Lithium, they also told me I could bypass the dip switch connections to turn the charger on and off remotely.

I opened the case and soldered wires to the switch board in parallel to the main on/off switch and the Dip Switch #4 selection, these wires will in turn be connected to the SBMS0 to turn the charger on/off giving it control of the state of charge, or turn the entire unit off to protect the batteries if the state of charge gets too low.

I am still waiting on my batteries to arrive from China, (has taken over 4 months) so I have not tested it out yet.

I am hoping that the 1500 watts of Solar I have planned will keep the batteries changed and I will not have to rely on the AIMS to charge them, but I can definitely see where I will need to on occasion and want the option.

I am no expert, this is the way I plan on doing it, use this at your own risk.

I have included a high level design of what I have planned.

Peter

[windtrader]

Jeremy and Peterbylt!


We can start the lithium crowd; others do lithium like freds so we can make our own club here. LOL


SBMS0? Way to go. That is what is driving my DIY pack as a solar charge controller and BMS for the battery. Just about any 24v inverter/charger will work for charging the pack. I have both an older Vanner and a newer Victron inverter/charger in the bus. Just kept the Vanner in for backup purposes but may wire in parallel for continuous 7kWh use but even at max demand now I don't need more than 3kwh.


Your AIMS should work. Why would it not? I think it depends on the specific pack you make. 7S LiPo is 25.9v nominal, typically charged to 4.0 is 28vdc. LiFePo4 is 25.6v nominal, 28vdc max recommended.


The primary reason chargers have various settings is charge profiles. Different battery chemistry can be charged at different rates so the charger needs to know to feed current safely. In the case of lithium, all types in this specific use case, all that matters is the voltage and using a setting that maxes charge current as lithium can take it. Well, most should not charge at more than 1C, so just make sure you stay under that unless the specs allow for higher charge current.


Good luck there is a bit to learn but it is very rewarding to build lithium battery storage for $125/kW

[Jeremy]

Thanks very much for all replies, especially for the Electrodacus info and the circuit diagram (which I've saved to my PC for future reference!). I can see I have a bunch of new reading to do, but it's good to know that others have addressed the exact issue I was wondering about

I need to do some learning but at first sight I'm not sure how much I like the idea of an external BMS / charge controller being able to turn the big inverter-charger on and off:- for instance I'd be worried about damage being caused if the charge controller tried to rapidly cycle the inverter-charger on and off as the battery pack reached it's fully-charged state. Also - I understood that the inverter-charger would run a pre-set charge cycle program itself (bulk, absorption, float etc), and surely turning it on and off is going to mess with that completely - at best you'd presumably keep getting the maximum-output bulk setting, and at worse the charge controller might get horribly confused because each time it asked for current they'd be a delay whilst the inverter-charger turned-on and analyzed the battery state before deciding what output to provide.

The other thing that occurs to me after looking at peterbylt's circuit diagram is that I've not thought about the solar side of my installation at all - I've always had the vague idea that I would add solar eventually, but clearly it's something that really needs to be planned as an integral part of the house bank charging system, not just added as an after-thought later

Thanks again for the food-for-thought

Jeremy

[Fred Mc]

Ive read that there COULD be a problem charging from the engine alternator in that lithium can take a charge much faster than SLA and could overheat the alternator.

[windtrader]

Engine alternator is only connected to start batteries in my system. Lithium bank is charged solely off solar array or generator on occassion.

[belfert]

Good luck there is a bit to learn but it is very rewarding to build lithium battery storage for $125/kW

Can you give details on your battery bank please?  I've read that large prismatic LifePO4 cells should not be used in RVs, but no explanation why.  The larger cells are a much better value than the smaller cells. 

[luvrbus]

Lithium batteries is something I am glad you guys buy from China ,I stopped this summer and saw how that stuff is mine,not a tree hugger myself but it is nasty and ugly on the environment for something "green" 

[Dave5Cs]

The biggest environmental danger posed by lithium mining is the amount of water the process uses up: an estimated 500,000 gallons of water per ton of lithium extracted. This can endanger the communities where the lithium is being mined because it can cause droughts or famine if operations are not kept in check.
Only 2% is mined in the US in one state the rest is in Austrailia, south America, chilli. Portugal and Spain.

[luvrbus]

The biggest environmental danger posed by lithium mining is the amount of water the process uses up: an estimated 500,000 gallons of water per ton of lithium extracted. This can endanger the communities where the lithium is being mined because it can cause droughts or famine if operations are not kept in check.
Only 2% is mined in the US in one state the rest is in Austrailia, south America, chilli. Portugal and Spain.

Yep and the Nevada desert has plenty of water  ,that water is wasted through the evaporation process to mine the stuff .The place had a recycle center and the guy told me only about 15% of the batteries ever gets recycled,The BLM approved another mine in Winnemucca (Thacker) NV for the same outfit   

[benherman1]

Yep and the Nevada desert has plenty of water  ,that water is wasted through the evaporation process to mine the stuff .The place had a recycle center and the guy told me only about 15% of the batteries ever gets recycled

I'd venture to guess that that number is either # of batteries counting a phone the same as a car battery or is just wrong. Contrary to what a surprising number of Facebook posts have said The big batteries are far to valuable to be thrown away.

[windtrader]

Here is link to one post where I show a picture and some specs of what was built\https://www.busconversionmagazine.com/forum/index.php?topic=34877.msg400816#msg400816

[someguy]

Ive read that there COULD be a problem charging from the engine alternator in that lithium can take a charge much faster than SLA and could overheat the alternator.

You can control the charge rate by varying the voltage supplied by the alternator.   This is easily done with a modified alternator voltage regulator. 

You can also use a DC to DC converter.

[someguy]

Yep and the Nevada desert has plenty of water  ,that water is wasted through the evaporation process to mine the stuff .The place had a recycle center and the guy told me only about 15% of the batteries ever gets recycled,The BLM approved another mine in Winnemucca (Thacker) NV for the same outfit

I'm amazed at the BS on Facebook and social media in general that people believe.   People with absolutely no technical background are domain experts on what can and cannot be done.   Who needs engineers and scientists ?  Apparently people who barely graduated from high school are suddenly the the experts.   LOL.