I am hoping to try and build a 560ah 12 v battery using 8 no. 3.2v 280ah cells. I'm planning using an induction cooktop which is 1800 watts using an inverter. On a 12v system that would be 150 amps. My plan was to use 8 no. 280ah 3.2v lifepo4 cells. I was going to parallel connect these into pairs to get 4 sets of 560ah 3.2v cells and then series connect these to get the 560ah 12v battery (2P4S). This was where I intend to use the Overkill bms but 120a won't be enough. Could I use one overkill bms and connect 4 of the cells in parallel to create a 280ah 12v battery then use another to create a second 280ah 12v battery and then connect these 2 batteries in series? Would that double the capacity of the original 1 bms to 240a? Would the 2 batteries operate okay together?
Beginner trying to build diy lifepo4 battery
- Thread starter Cs1fr
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You could make two 12V batteries each with their own overkill and then parallel the two batteries. If you series them, you get 24V
Series means positive to negative - voltage adds, capacity stays the same.
Parallel means positive to positive, neg to neg - voltage stays the same, capacity adds.
Series means positive to negative - voltage adds, capacity stays the same.
Parallel means positive to positive, neg to neg - voltage stays the same, capacity adds.
You have your terminology backwards so it would 4 in series then parallel those to strings of 4. You can do as you wish but the problem arises if one of the BMS shuts down under say a 200 Amp which wS shred between the 2 BMS, you will now have 200 amps goi g through 1 BMS. The best possible solution is doing a 24v system. But that may not be possible for you depending on the whole system design.
Cs1fr, I have the battery bank in my trailer that I think you're considering. EVE 3.2v 280Ah cells in a 4s configuration with an Overkill 120 amp BMS. Two of those, both connected to the main bus bar, for 560 Ah.
An induction cooktop is going to be a HUGE drain. Add in the efficiency loss in the inverter, and you're looking at some seriously large cables.
To make this work, you would likely need a battery bank that is 24 or 48 volt and 560 Ah. I'm spitballing this, no number crunching. With the higher voltage you wouldn't need to have cables as large.
An induction cooktop is going to be a HUGE drain. Add in the efficiency loss in the inverter, and you're looking at some seriously large cables.
To make this work, you would likely need a battery bank that is 24 or 48 volt and 560 Ah. I'm spitballing this, no number crunching. With the higher voltage you wouldn't need to have cables as large.
NCblueridge
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Do you have a 12V system instead of 24? With my two projects, I am ok with 12V since they are fairly small, one is very small. I am thinking about a 3rd base unit that will go with my panels fulltime to manage a small freezer. I want all 3 for backup in the case of a power failure or SHTF
Do you have a 12V system instead of 24? With my two projects, I am ok with 12V since they are fairly small, one is very small. I am thinking about a 3rd base unit that will go with my panels fulltime to manage a small freezer. I want all 3 for backup in the case of a power failure or SHTF
Yes, it's 12 volt. I didn't want to complicate the system by jumping to 24 or 48. Everything DC in my trailer uses 12 volt.
NCblueridge
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For my needs that works also, but for the larger bank I want to do, I may go 24, the biggest obstacle I run into with 12v is wire size and amps. This one will be more stationary and 2X the amp hours of my 100 and 120ah setups.
Im curious about induction cook tops. Im seeing them in the 1300 to 1800 watt range. Since you wouldn't be using one for more than a half hour at a time it would be only 900 watt hours worst case. But as with everything the specs are not the full answer. Is there more I need to know about these. To me they just seem safer than gas. I understand a large drain but if one had a 24v 560Ah battery the 13Kw would handle it well
At the higher voltage, probably not a big deal. It's the 150 amp draw in a 12 volt system that could be a limiting factor. 75 amps in a 24 volt system, not such a big deal.
However, from my quick search, there simply aren't any 12v, 1800 watt induction cooktops out there. At least not any that you would actually trust.
There are very few DC induction cooktops at all.
I agree I was just looking last night and you would have to use an inverter and AC power.At the higher voltage, probably not a big deal. It's the 150 amp draw in a 12 volt system that could be a limiting factor. 75 amps in a 24 volt system, not such a big deal.
However, from my quick search, there simply aren't any 12v, 1800 watt induction cooktops out there. At least not any that you would actually trust.
I could see using an induction cooktop during the day, when I have excess solar watts available. But once the sun goes away, I would be skeptical. 900 watts overall doesn't sound too bad, but that's probably optimistic.
Propane isn't a big deal unless it's 20° F and a refill of a 30 lb tank is 45 minutes away. Been there, done that. Where I hunt, the little town 45 minutes away rolls up the sidewalks at 6 pm except for the two restaurants.
Propane isn't a big deal unless it's 20° F and a refill of a 30 lb tank is 45 minutes away. Been there, done that. Where I hunt, the little town 45 minutes away rolls up the sidewalks at 6 pm except for the two restaurants.
My system is for a campervan and the plan is to charge from alternator which is why I'm not able to go 24v. I will also have solar but the alternator charging is essential because it guarantees battery charging when no sun. Unless anyone knows of a way of charging a 24v system from an alternator.
Yes I intend to have a 3000 watt inverter. Not sure if this is overkill as I'm not planning on running more than one a/c appliance at a time (240v UK) but am worried that 1800watt induction is close to the limit of a 2000w inverter
This is so good to hear you have the same as I am planning. Unfortunately I am going to be using alternator charging, as well as solar, to make sure that I always have a way of providing power. I have a couple of questions that I would be really grateful if you could answer as I am a real beginner and worried about making a mistake:
1. Where did you get your cells. Were they a good supplier to deal with, did they take long, did they appear class A etc?
2. A really stupid question but I can't figure out how to wire it. I think I would connect the first overkill bms to the first negative of my first 4s 280ah battery. Then hiw do I connect the negative out from the first bms to the next 4s 280ah battery? I'm guessing the out negative for the second battery would connect to all the chargers and 12v out system. Like zip said a real beginner.
Here is a good Q&A with SV Delos talking about their converted galley to all electric. I believe they are a 24 or 48 volt setup.
SV Delos electric galley
SV Delos electric galley
I bought my cells from Xuba through Alibaba. Here is the thread that talks about buying from Xuba. You don't need to read the whole thing, but there's a lot of good information there. Prices went up this month and supply may be limited because the manufacturer may be withholding supply.
I wired my batteries independently. They both connect to a common bus bar. In other words, there are no wires between the batteries. The bus bar is where they meet up.
I'm planning on a very similar system (12v, 560AH LIFEPO4 DIY battery bank) in my van conversion to use with a 3000W 12v inverter for my 1800w induction cooktop and 1400w hot water tank (though I don't plan to run them at the same time). I spent a few weeks researching the pros and cons of 12v vs 24v for this system. For me the main downsides were needing to add a 24 to 12v converter to the system to run the majority of my appliances (12v), and use a 12-24v dc to dc charger like this rather than one of the more commonly found 12v-12v dc to dc chargers. After much consideration I've gone ahead and purchased a 3000w 12v inverter I found a great deal on, and am leaning towards the chargery 600A BMS and relay at the moment but have yet to order my cells and BMS.
Looks like you've explored some good options. Only thing I'm concerned about with my BMS is that it has low temp cutoff because I live in Scotland. Also have you sourced your cells yet. Would be great to get a link and also for the inverter.
You can easily charge a 24v lithium battery from a 12v alternator. Both Sterling and Victron (and I am sure a few others) make them. The charger pulls 14v from the car battery/alternator when its running, then it charges (using the proper lithium settings) the 24v lithium battery. The other advantage of these DC-DC chargers is you won't overtax your alternator by running the alternator at 100% for a long time.
you may also want/need a 24v to 12v convertor to run any 12v items (Lights, fans, etc).
you may also want/need a 24v to 12v convertor to run any 12v items (Lights, fans, etc).
RVsolar1Day
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I am building a similar battery bank and was wondering if there was a reason you connected the batteries to a bus bar instead of wiring them together directly?
