LiFePO4 battery build

[StirCrazy]

I got my new cells in today and I am going to start putting them together after I sort out whether I am getting a new cell or not, as one has some slight damage. It is probably fine to use but between shipping and duty charges I paid quite a bit for this set of cells so if they offer to send a new cell, I'll take it.

so, the cells I got for this build are EVEv304AH grade A cells. so, when I do get it together and do a capacity test, I am expecting more than 304 and possibly up to 320AH.

here is how they were packed


here is the damage on one of the cells


length


height


width



Anyway, what I want to know is if there is interest in me doing a thread on this build. People that have already built batteries probably wouldn't be interested much but it is more the people that are sitting on the fence about building their own. Also, I would want people who have done builds before to have input on how I make a case or whatever else. my last one wasn't in a case or compressed.

[Community Alumni]

Well not sure if I am going to continue with posting this build or not and if I do should it be in a different area as this is not DIY maintenance so does it fit here?  plus the frustration and headache from three days of trying to navigate this site and also the main attraction forum for me that is now missing, has me questioning if I am even going to stay on this forum

[StirCrazy]

so my replacement cell should be here today, but now I am faced with another disision which I am going to go to some of the other people that have LifePO4 batteries they have build them selves for their opinion.

JBD BMS (also sold rebranded as Overkill) are a good BMS. I have been happy with the one I have in my other battery but now there is Jk on the scene.

This is the one I have, it is no longer available, but I bought two when I got my original one.

JBD 150 amp

this is the one I am thinking of buying a couple of and replacing what I am using now.
https://www.aliexpress.com/item/1005005854174956.html?spm=a2g0o.productlist.main.43.c8f92a40z0ehFE&a...

The main reason is for the 2A active cell balancing feature over the passive balancing feature of my original BMS. Plus, the reviews on JK BMS have been amazing and the app is set up much nicer.

so, for those that have built their own batteries, would you go with an external 2-amp active balancer if you were building a new battery, or would you go with an active one built into the BMS

[StirCrazy]

pianotuna wrote:
Stir I probably won't have SiO2 either. My existing bank may well outlast my ownership of my class C.

I know prices have dropped--but I want at least 500 amp-hours. That's over four grand.

yup they are expensive, and their curve isn't as closely matched as LFP for 12V, but they work. I just don't like the form factor they are available in as they are more work to mount and such.

[pianotuna]

Stir I probably won't have SiO2 either. My existing bank may well outlast my ownership of my class C.

I know prices have dropped--but I want at least 500 amp-hours. That's over four grand.

[StirCrazy]

pianotuna wrote:
stir find me an LifePo4 that works reliably at -40 with no "self heating". The only one I know of is Lithium titinate which is way beyond my budget. (at the time $1800 for a single 100 amp-hour)

I'm glad your choice works well for you.

SiO2 are a much better fit for me except for cost.

which is exactly why I am surprised your even comenting on this thread, you have dmisitidly stated you will never have LFP as you won't make alowances to make them work by putting them in the conditiond space or other simple things, so why are you interested in a thread on how to build one, I am actualy curious.

actualy LTO has come down a lot in price you can get 45AH cells for 39 bucks each and it takes 6 to make a 12V battery. so you could do a 90AH battery for about 684.00 plus what ever your BMS for that costs.

[StirCrazy]

Itinerant1 wrote:
StirCrazy nice size battery bank. The only thing I'm going to disagree on slightly is the cells heating up.

As I have posted before I fulltime in the 5th wheel living off of 500ah lfp batteries and 1,280w solar. This setup has been going for 7 years 7 months now in everday use never been turned off. My longest strech of consecutive boondocking was 1,017 days. As of today we have hit a 2 year stretch of consecutive boondocking.

The only time I've seen the cells heat up is when using the gen/ inverter charger and charging at 100a for more than anhour and then the cells only get 10f warmer. Any other time whether using microwave or other appliances the cells might climbed a dregree or so but nothing enough to make a difference.

My batteries, inverter, SCC is all in the front compartment of the 5th wheel. I have used foam board insulation on the walls. Used Reflectixs, foam board, 1/2" rubber mat on the floof of compartment and tapped into a heat duct above the batteries and dropped a tubedown towards the battery. This has made the biggest difference keeping the batteries warm in that compartment. I was just in Utah for a few days of night times of high teens and daytime of upper 40s. Cells were at 46-55f. Me personally that's as cold as I like it and have moved further south now for winter.

If I were somewhere that I couldn't run from the extreme cold the batteries would be in the 5th wheel somewhere staying as warm as me.

Keep us updated on the build. Thanks:)

ya that weird, I get about 8 to 10 degrees when its that cold in the camper. I supose some heat could hav been radiating from the wet bath shell into the storage space they used to be in. I know a lot of people I know in alberta just use a good cooler on there trailer tounge with a silicone heating pas that only comes on when it gets to 0 inside and they tell me when they are on their skidooing trips at -10 to -25C they hardly ever see the silicone heater come on.

[pianotuna]

Stir I fixate on outdoor temperatures because I am not full time. So the RV has to go from cold soaked -34 F to living temperatures.

Therefore the batteries need to be fully functional in admittedly, extreme cold.

[Itinerant1]

StirCrazy nice size battery bank. The only thing I'm going to disagree on slightly is the cells heating up.

As I have posted before I fulltime in the 5th wheel living off of 500ah lfp batteries and 1,280w solar. This setup has been going for 7 years 7 months now in everday use never been turned off. My longest strech of consecutive boondocking was 1,017 days. As of today we have hit a 2 year stretch of consecutive boondocking.

The only time I've seen the cells heat up is when using the gen/ inverter charger and charging at 100a for more than anhour and then the cells only get 10f warmer. Any other time whether using microwave or other appliances the cells might climbed a dregree or so but nothing enough to make a difference.

My batteries, inverter, SCC is all in the front compartment of the 5th wheel. I have used foam board insulation on the walls. Used Reflectixs, foam board, 1/2" rubber mat on the floof of compartment and tapped into a heat duct above the batteries and dropped a tubedown towards the battery. This has made the biggest difference keeping the batteries warm in that compartment. I was just in Utah for a few days of night times of high teens and daytime of upper 40s. Cells were at 46-55f. Me personally that's as cold as I like it and have moved further south now for winter.

If I were somewhere that I couldn't run from the extreme cold the batteries would be in the 5th wheel somewhere staying as warm as me.

Keep us updated on the build. Thanks:)

[pianotuna]

stir find me an LifePo4 that works reliably at -40 with no "self heating". The only one I know of is Lithium titinate which is way beyond my budget. (at the time $1800 for a single 100 amp-hour)

I'm glad your choice works well for you.

SiO2 are a much better fit for me except for cost.

[StirCrazy]

pianotuna wrote:
Stir thanks for the link.

I'm glad you posted some of the details. I can't read what ever language they have. They are close to my needs but..close only counts in horseshoes and curling.

I have done more than a few 10 day trips where the daily high was below -30.

well, that's why it is in Chinese and English. you keep fixating on the outside temperature. that has nothing to do with whether the batteries will work or not for you. well, it has an influence. It's the actual battery temperature that matters, as in the internal temp. So, with a BMS that has a built-in heat control and having the batteries in an insulated space (even one that receives heat from the rv) you would have no problem. You could have the BMS heat the internal temperature of the battery to -30 then run the furnace. As you start using the battery, they make their own heat also which warms them up even more. before I moved my 280AH batter to an interior place in my camper I had it in the uninsulated exterior storage that gets pretty darn cold and at -10C (nighttime temps) the internal temp of the battery was still above 5C so I didn't have any issues as the act of running the furnace and lights was enough to keep the battery warm. Now that it is inside the camper there is even less of an issue as it is only cold when I first go somewhere and being able to discharge at 0.25C at -30C is more than I will ever need to start the furnace and warm everything up.

[pianotuna]

Stir thanks for the link.

I'm glad you posted some of the details. I can't read what ever language they have. They are close to my needs but..close only counts in horseshoes and curling.

I have done more than a few 10 day trips where the daily high was below -30.

[StirCrazy]

pianotuna wrote:
stir,

Do you have a link to these -35 F cells?

here is the Data sheet for my cells.

when you want real info, you go by the data sheet not the sales info from middlemen. I do have to find out what they define pulse discharge as. At -35 you can only pulse discharge at 0.8C which for me to start my furnace and warm up the cells is fine as I would only draw 0.01C, but for continuous discharge you must be at -30 or warmer and you can draw 0.25C continuous.

I guess they define pulse as a 30 second blast, so I think if I ever planed on camping at -35, which I won't I have done once and nothing works good in the rv, even the propane is sluggish, but I would put heating mats on the battery with a 30 second on off timer to bring it up to -30 in the battery pack then I could have at it. but for the record camping in -30 isn't much fun either... I don't mind lows of -15 at night but beyond that it isn't camping its just surviving. haha

[pianotuna]

stir,

Do you have a link to these -35 F cells?

[StirCrazy]

time2roll wrote:
Cells look fine. JBD is great. Enjoy the new found freedom with lithium.
I recommend an active balancer over doing an initial parallel top balance.

I have 16 similar grade B cells and they work perfectly. Although I would have preferred your terminals if they were available at the time.

The store shipped a new cell to replace that damaged one. I have had a 280AH setup in the camper for almost two years now, so not new found freedom, just the start of converting the 5th wheel to LFP also. and the terminals are the major reason I went with these ones, plus a US supplier so more reliability.

I am probably going to initially balance them manually when I do my first could capacity tests, but I am also thinking of getting a different brand BMS, JBD is good, but JK is killing it with some of their new one. They have a 200amp 4S with 2amp active balancing. The best thing is it is 4 to 8S so if I wanted to add another 4 cells later I could. here is a link to it (not where I will buy it from just the first link to come up JK BMS

Steve