LiFePO4 house battery -> DC-DC charger -> Tiny LTO battery for high current induction cooker

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
Has anyone ever added a small LTO battery to a LiFePO4 system specifically to handle just one very high current appliance?

I've been putting together a 24v system to handle an induction cooker, but I got to thinking that I could also just maintain a small 50-60 AH LTO battery for this need. This might just add more complications than needed, but I like the idea of having the LTO around as well for things like emergency jump starts in freezing weather (I life in Colorado).
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
Why?

What induction cooker? You can get two burner ones that are 1800w and this is easily handled by a 12v system, trivial on 24v.

What is your lifepo4 system AH capacity and configuration?

Do you already have an inverter for 120v?

Or are you trying to get a low voltage induction cooker (which I believe isn't even a thing?)
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
On top of that you'd need to isolate that battery from the rest of it in order to only draw power from the one LTO pack when you use it
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
>Why?

If I had an LTO battery, I could pull high than the 1c my 12v battery is limited to.

> What induction cooker? You can get two burner ones that are 1800w and this is easily handled by a 12v system, trivial on 24v.

It's an AC powered single burner that pulls ~1700w at max. Not handled at all by a 1c 12v battery, hence why I'm looking at LTO for the higher C rating as a possible solution to avoid going 24v.

> What is your lifepo4 system AH capacity and configuration?

I've got 2 battleborn 12v 100AG batteries.

> Do you already have an inverter for 120v?

Not yet.

> Or are you trying to get a low voltage induction cooker (which I believe isn't even a thing?)
No, I wish they were a thing. a 24v one would be awesome as I'd be able to completely eliminate the inverter.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
1700w after inverter losses at 24v is 83 amps.


This is less than 1C.

At 12 volts it's ~166 amps across two batteries.

Which is less than 1C. Remember in parallel it distributes the load more or less equally.
 

wholybee

Solar Addict
Joined
Feb 11, 2021
Messages
468
>Why?

If I had an LTO battery, I could pull high than the 1c my 12v battery is limited to.

> What induction cooker? You can get two burner ones that are 1800w and this is easily handled by a 12v system, trivial on 24v.

It's an AC powered single burner that pulls ~1700w at max. Not handled at all by a 1c 12v battery, hence why I'm looking at LTO for the higher C rating as a possible solution to avoid going 24v.

> What is your lifepo4 system AH capacity and configuration?

I've got 2 battleborn 12v 100AG batteries.

> Do you already have an inverter for 120v?

Not yet.

> Or are you trying to get a low voltage induction cooker (which I believe isn't even a thing?)
No, I wish they were a thing. a 24v one would be awesome as I'd be able to completely eliminate the inverter.
2 Battleborn batteries should be able to handle 1700W easily.
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
Sorry Ive made this not clear. Im looking at LTO as a solution to keep from having to go to 24v. Charging becomes more complicated if I wire in series and make 24v. If I wire in parallel, charging is a lot cheaper, but my understanding is that would limit me to 1c at 12v =100 amps.

@whollbe, are you saying in parallel I could pull 1c from each battery or 12v 200 amps?
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
Sorry Ive made this not clear. Im looking at LTO as a solution to keep from having to go to 24v. Charging becomes more complicated if I wire in series and make 24v. If I wire in parallel, charging is a lot cheaper, but my understanding is that would limit me to 1c at 12v =100 amps.

@whollbe, are you saying in parallel I could pull 1c from each battery or 12v 200 amps?
In parallel half the current goes to each battery.

You'll only pull 85 amps or so from the batteries @ 12v
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
Wow, I wonder why I didn’t know this…

Looks like that solves it for me. 12v it is. Only downside is I won’t be able to go smaller wires for the 24v runs, but I was going to bring 12v from the alternator to the charger sitting next to the batteries anyhow, so that would have only been a very immaterial savings anyhow.

Thanks all!
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
Wow, I wonder why I didn’t know this…

Looks like that solves it for me. 12v it is. Only downside is I won’t be able to go smaller wires for the 24v runs, but I was going to bring 12v from the alternator to the charger sitting next to the batteries anyhow, so that would have only been a very immaterial savings anyhow.

Thanks all!
You might find you run out of capacity before you have issues pulling that power out of them to be honest.

However, being able to run at less than full power for less time is a benefit of an induction plate with a good pan.
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
You might find you run out of capacity before you have issues pulling that power out of them to be honest.

However, being able to run at less than full power for less time is a benefit of an induction plate with a good pan.
I suspect I'll only be using the induction burner for 20-25 minutes per meal... if that. If I do run out of capacity (especially since I'll then be turning around and running the AC for 8 hours (only uses 250 watts max)) I can just throw another battery at the end of the parallel "stack".
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
You have about 2400wh.

250w for 8 hours is 2000wh.
20 minutes per meal at 1700w is around 670wh after inverter losses.

You're coming up short already before you started. And you've still got perhaps an additional meal, maybe two per day.

Are you going to run solar as well? I assume that is the case if you're on this forum.
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
You have about 2400wh.

250w for 8 hours is 2000wh.
20 minutes per meal at 1700w is around 670wh after inverter losses.

You're coming up short already before you started. And you've still got perhaps an additional meal, maybe two per day.

Are you going to run solar as well? I assume that is the case if you're on this forum.
250W is absolutely max… will usually be half that. Same with 1700w on the stove. It’s hard not to burn anything. I’ll probably usually cook at around 1kw.

But, if I do go over, then I’ll just bring my 3rd battery.

Eventually, I’ll throw 200w in the top of the jeep, but that’ll probably be a spring of next year.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
What AC do you have that's only 250w max???

One of those tiny 2000 btu things that's insanely expensive?
 

imbuere

New Member
Joined
Oct 2, 2020
Messages
45
What AC do you have that's only 250w max???

One of those tiny 2000 btu things that's insanely expensive?
I haven’t purchased it yet, but my eye is in the zero breeze2. I hope to spend 60-75 nights a year in the camper, so if it lasts it’s not that expensive. They are only around 2k btu, but my sleeping area is only a poorly insulated 30ish cubic feet.

In the long term, I’m pretty sure I’m going to make a mini split. Being able to put the condenser outside separated from the air inside should increase the efficiency by 1/4.
 

chrisski

Solar Boondocker
Joined
Aug 14, 2020
Messages
3,386
I have not seen it mentioned, but running 1800 watts for an extended time, like more than a minute or two, off a 12 volt system is not good. In my signature block there's links to why, but short answer is over 100 amps in wiring you have to do special things.

I think of the high C output application of LTO as for cases where its going to be used in very short bursts, but not sustained, like for an electric vehicle when accelerating. The cooking you described, if done in the day, could be handled by 100 ah of 24 volt batteries lithium Iron Phosphate and 200 watts + of panels. To me, how many panels depends on how long you cook so your panels can replace. With only 100 ah of batteries, would not leave a lot of power once the sun goes down.
 

wholybee

Solar Addict
Joined
Feb 11, 2021
Messages
468
I would suggest 4 battleborns, series parallel for 200Ah at 24V. Presumably, you have more than just an induction cooker and the tiny A/C unit. (a cooler? Lights, a laptop?) And if your 30sq ft space is poorly insulated, that tiny A/C unit might be working harder/longer than you think. At some point you might even want to add 2 more, for 300Ah.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
I haven’t purchased it yet, but my eye is in the zero breeze2. I hope to spend 60-75 nights a year in the camper, so if it lasts it’s not that expensive. They are only around 2k btu, but my sleeping area is only a poorly insulated 30ish cubic feet.

In the long term, I’m pretty sure I’m going to make a mini split. Being able to put the condenser outside separated from the air inside should increase the efficiency by 1/4.
Oh man I don't recommend that unit.

I use a 5k btu in my mypod and it's not enough sometimes. My mypod is maybe 50 cubic feet or so I think.

You'll be better off buying a Mitsubishi 6k and a 120v to 230v step up transformer for roughly the same cost, if you're considering it in the longer term anyways


The lowest output on the Mitsubishi is 1700 btus and it pulls 100 watts, plus a bit for the indoor unit.

Do some math on the costs and power consumption before buying that insanely overpriced zero breeze.

I almost fell into the same logic you're likely using, and looked into that unit heavily.
 

Short_Shot

Photon Sorcerer
Joined
Jul 13, 2021
Messages
1,816
I have not seen it mentioned, but running 1800 watts for an extended time, like more than a minute or two, off a 12 volt system is not good. In my signature block there's links to why, but short answer is over 100 amps in wiring you have to do special things.

I think of the high C output application of LTO as for cases where its going to be used in very short bursts, but not sustained, like for an electric vehicle when accelerating. The cooking you described, if done in the day, could be handled by 100 ah of 24 volt batteries lithium Iron Phosphate and 200 watts + of panels. To me, how many panels depends on how long you cook so your panels can replace. With only 100 ah of batteries, would not leave a lot of power once the sun goes down.
Hard disagree.

The only thing you need to do for a 12v system is suitably size your wiring and make sure the connections are good.


100a wiring is fairly trivial to install. Even 200a isn't a huge pain.

Though I agree that 24v is better suited overall.
 
Top