Interesting DIY Lifo Battery Video

[freds]

I saw an interesting video today on a DIY Lifo Battery Video that I thought I would pass along.

In the power system for my bus I used recycled Tesla Battery modules and estimate that I paid somewhere around $0.35 per usable watt hour after everything was said and done.

There is a number of factors that bumped my cost per watt hour up:

Current house inverter cuts out at about 20% charge
You only want to charge a Tesla battery to 90% to extend it's life and generally not discharge below 10%.

My Tesla battery pack has a theoretical storage of 26KW with a usable storage of 18.2KW. Which is nothing to sneeze at as it is about the equivalent of 10-12 Deep Cycle 8D batteries.

Anyway the video in question that sparked this post is: https://www.youtube.com/watch?v=D2eXgiakD8U&t=2329s

The thing in this video is that he is converting a battery pack that is 65V to 48V to make it compatible with standard all in solar inverters that are on the market and heck who would want a 48V battery pack for your main house battery and an auxiliary 12V battery?

Anyway as a 48V battery it works out to about $0.19 a watt hour. At the end of this process you have 48V 14.2KW battery pack and 3KW 12V pack.

Note the gold standard Battle Born batteries are about $0.77 per watt hour. Though cheap alternatives on Amazon are around $0.25 per watt hour. But you would have to buy multiples and hook them together.

The battery Module weight is approximately 320 lbs and the dimensions are 36" x 17" x 9".

Note my Tesla battery modules are around 275 lbs in total.

Just tossing this out there as food for thought....

Enjoy...

[windtrader]

Thanks Fred. I have a shipment of those CATL grade A batteries in transit from BatteryHookup. I've been buying from them for a couple years. They claim these are new and true grade A, meaning they are EV rated.

48 vs 24. If I were starting fresh, I'd go 48v but 24v is more compatible. I'm most interested in testing the claimed charged/discharged C rating. If they can charge at 1C nominal that presents a new twist into the entire charge side design. The pack capacity is 6.8 kW, meaing a 7kW generator going full tilt can do a complete top off from empty. Given a 50% SOC, 3,4kW, many of the common gas generators can do that in an hour. I'd love to decommision the massive diesel genny and sub in a compact Honda or similar. It's only for times when solar is unable to provide sufficient watts anyway such as multiple days of gray days.
The pricing you quote is for LiFePO4, not lithium ion chemistry. I was tempted to go that way again due to lower cost but common sense prevailed and I went with the far safer, although less power dense and heavier.
I'll report back over the weekend as the cells are schedule to deliver on Thursday.

One other possibility is using the house bank for engine starts. If the battery can indeed pull 3C then 900 amps at 24v is more than enough to kick @$# on that engine for a few seconds.

[freds]

One other possibility is using the house bank for engine starts. If the battery can indeed pull 3C then 900 amps at 24v is more than enough to kick @$# on that engine for a few seconds.

I have cogitated on that myself and my current thoughts are that if the main start battery is to low to turn the engine over I will just use a jumper cable for 15-20 minutes to put some juice back into the start batteries.

However in my setup I have DC-DC converters to maintain both the start batteries and the 12V house battery which also serves as the generator start battery.

So if the house battery can't keep the start battery's and house battery up to snuff it's time to reboot everything.

I like your thoughts about dumping the heavy @$# diesel generator and going with something lighter for backup... Given that a mechanic listened to it run and thinks it about clapped out...

[luvrbus]

I have cogitated on that myself and my current thoughts are that if the main start battery is to low to turn the engine over I will just use a jumper cable for 15-20 minutes to put some juice back into the start batteries.

However in my setup I have DC-DC converters to maintain both the start batteries and the 12V house battery which also serves as the generator start battery.

So if the house battery can't keep the start battery's and house battery up to snuff it's time to reboot everything.

I like your thoughts about dumping the heavy @$# diesel generator and going with something lighter for backup... Given that a mechanic listened to it run and thinks it about clapped out...

If you toss the heavy @$# high amp 42 or 50 Delo starter for the Delo 39Mt you could start the engine with 2 lawn mower batteries and have power to spare

[Dave5Cs]

But then what is he going to do with two lawn mowers that can't be started?

[luvrbus]

But then what is he going to do with two lawn mowers that can't be started?

Full timers don't mow grass some grow a plant or 2,Dave you believe this I bought a battery for the John Deere mower yesterday 56 bucks for a tiny battery lol I could have bought a goat for $35.00

[windtrader]

I have cogitated on that myself and my current thoughts are that if the main start battery is to low to turn the engine over I will just use a jumper cable for 15-20 minutes to put some juice back into the start batteries.

Good idea, it works. I've done that many times until I decided to keep the inverter on 24/7 and now leave a battery charger alway attached. Works even better as batteries stay 100% and always a single button press and vroom.
Fred, what is the battery bank spec, volts and capacity? One advantage of running at 24v is it is plug compatible with the bus electrical. If there has to be a DC-DC converter between battery and starter, that adds a complexity that is likely not cheap as finding one that passes 600-800 amps even for not too long is industrial , i.e. expensive.

[freds]

Good idea, it works. I've done that many times until I decided to keep the inverter on 24/7 and now leave a battery charger alway attached. Works even better as batteries stay 100% and always a single button press and vroom.
Fred, what is the battery bank spec, volts and capacity? One advantage of running at 24v is it is plug compatible with the bus electrical. If there has to be a DC-DC converter between battery and starter, that adds a complexity that is likely not cheap as finding one that passes 600-800 amps even for not too long is industrial , i.e. expensive.

There is nothing that prevents you from configuring the same pack as 24V by splitting it up into three sections and paralleling the 24V sections in which case you would have a 24V 560AH battery, that can deliver 1680 amps (3C discharge rate) in short bursts and a separate 12V 280AH battery,  that can deliver 840 amps (3C discharge rate) in short bursts.

The fly in the ointment would be the BMS as I am not sure there are ones out there that can handle the draw of the main starter motor. Maybe have a temporary bypass around the BMS for bus emergencies or starting only?

Interesting idea, totally get rid of lead acid batteries all together. Though if you had to jump start the bus you might melt the jumper cables!!!

I use a Victron DC-DC converter that draws off of my Tesla battery pack in battery charger mode to just keep the bus start batteries always charged.

[Dave5Cs]

Full timers don't mow grass some grow a plant or 2,Dave you believe this I bought a battery for the John Deere mower yesterday 56 bucks for a tiny battery lol I could have bought a goat for $35.00

That's  incorrect weed hopper. At two of the last places we stayed in Missouri we had to mow our own grass between sites which was a good sized lawn.LOL
Here I weed eat every so often but the mow just not very good sometimes.

Ya batteries are up again. Maybe they will put someone in office that has a brain either side IDC. and vote for all new people to send a message.

[freds]

If you toss the heavy @$# high amp 42 or 50 Delo starter for the Delo 39Mt you could start the engine with 2 lawn mower batteries and have power to spare

Interesting what is the amperage draw of the starter for a Detroit diesel?

I found a couple of links but couldn't make heads or tails of the amperage graph which looked similar to other starters.

https://www.doverbrakeinc.com/downloads/catelogs/DELCO%2039MT%20STARTER.pdf
https://www.delcoremy.com/starters/find-by-model-family/39mt-gear-reduction-starter

But hey it does spark an idea of Windtraders post of only one battery for the entire bus. Set the BMS to kick offline with enough juice remaining to start the bus.

You would need a smart controller for the buses alternator to limit the maximum charge current.

I found a link to such a controller:

https://balmar.net/balmar-announces-regulator-support-for-lithium-batteries/

[freds]

Opp's forgot extreme cold weather charging environment, so a single large battery for everything wouldn't work.

[windtrader]

Interesting idea, totally get rid of lead acid batteries all together. Though if you had to jump start the bus you might melt the jumper cables!!!

Hey, I've done it more than once and they have not melted but will warm up pretty quick so I feel the pressure to get it to fire right away. Glad those days are behind me now that I keep the charger connected all the time.
If I were to hook the start directly, just take the lead going to the battery and swing them to the main house posts, cut out the BMS. The main bus battery cutoff switch would still be operational that way.
Somebody needs to stick a clamp on amp meter to get a read on the start current. I'll need to check if my will read in that range. It does have a max feature to capture the number.

What works for some won't do for others. As my religion forbids me to live where it freezes or gets too hot, my bus is always kept at the right temps. LOL

[luvrbus]

I rented a car last week for a few days,I almost got weak enough to try a EV  they had in the fleet but the price was crazy $250.00 a day and by the time a rental agency gets through adding all the fees it would have cost close to $400.00 a day so I passed.Rental cars are terribly expensive now with all the fees they impose on you