Before I Spend a Big Gob of Money on LiFePo4.......

[ColeMan]

.......I need to ask a couple of questions.
I'm capable of a lot of DIY stuff, but I've never built a battery.
This is for a camp trailer in which I plan to eventually add
a 2 or 3000 watt inverter and maybe 600 watts of solar,
but for now I'm only interested in running the 12 volt systems.

Been considering a SunFunKits ready-to-build battery,
but I learned in a YouTube video that before you can
built these kits, the cells need to be "top balanced".
So I watched some videos on that, but I'm not set
up with all kinds of power supplies and battery chargers.
All I have is the converter in my camper, which can
be switched over to charge lithium batteries, but doesn't
seem like it would be the right tool for "top balancing".

So should I bag the kit and just buy pre-built batteries?
And if I do that, is it better to get two or
three 100ah batteries and wire them in parallel,
or just get one 200ah or 300ah battery?
What's the optimum set up for just the 12 volt systems?
Thanks in advance!

 

[time2roll]

Depending on the converter..... an upgrade might be an eventuality. If it is a WFCO the charge voltage may only be 13.6 rendering the balance close enough to put in service imediately.

An active balancer for $20 can get the balance close enough if the cells prove to be at significant difference in charge levels.

When choosing a LFP battery also consider max charge and discharge rates. All are limited by the BMS. May need two or more in parallel to drive a 2000+ watt inverter.

 

[ColeMan]

.

 

[GavCol]

.......I need to ask a couple of questions.
I'm capable of a lot of DIY stuff, but I've never built a battery.
This is for a camp trailer in which I plan to eventually add
a 2 or 3000 watt inverter and maybe 600 watts of solar,
but for now I'm only interested in running the 12 volt systems.

Been considering a SunFunKits ready-to-build battery,
but I learned in a YouTube video that before you can
built these kits, the cells need to be "top balanced".
So I watched some videos on that, but I'm not set
up with all kinds of power supplies and battery chargers.
All I have is the converter in my camper, which can
be switched over to charge lithium batteries, but doesn't
seem like it would be the right tool for "top balancing".

So should I bag the kit and just buy pre-built batteries?
And if I do that, is it better to get two or
three 100ah batteries and wire them in parallel,
or just get one 200ah or 300ah battery?
What's the optimum set up for just the 12 volt systems?
Thanks in advance!

From one ColeMan to another
Don't limit yourself to 200-300ah and go for the diy 640ah option (could even be higher now) with 8 cells ? and it didn't break the bank either.

Checkout these posts of my build.

Post in thread 'Feedback on LiitoKala 3.2V 320Ah lifepo4 prismatic cells Ali Express' https://diysolarforum.com/threads/f...prismatic-cells-ali-express.20683/post-299293

AliExpress (Sellers or disputes) - the good, the bad & the ugly

Hi all, Lovin' the wealth of info here. Such a compliment to Will's videos. I've learned a helluva lot over the past year to the point we recently ordered our own DIY components. Still waiting on the 8 x 320ah cells from China. The reason for this post is that I have a good news experience...

diysolarforum.com

 

[ColeMan]

Well, my original question is moot.
I've since learned that the V3 kits come with
an "active balancer", so now I'll learn about that.
Off-Grid Garage Andy isn't a fan of that.
What say you?

 

[Alkaline]

You can balance your cells using a 3.65 power supply and some buss bars.

I am using an active cell balancer on my 8s 280K setup and it keeps my cells about 3.63 volt each when fully charged.

I think the consensus now is, use it to bring your back to full charge and then remove/dissable it until you need to balance your cells again.

As for me I just keep it connected and have not had any issues, although some people are claiming the active cell balancers have a vampire/beserk mode where they can drain down a cell, so this is still to be investigated.

I also made a thread regarding this https://diysolarforum.com/threads/a...ancers-fail-and-kill-cells.41219/#post-521242

 

[ColeMan]

You can balance your cells using a 3.65 power supply and some buss bars.

I am using an active cell balancer on my 8s 280K setup and it keeps my cells about 3.63 volt each when fully charged.

I think the consensus now is, use it to bring your back to full charge and then remove/dissable it until you need to balance your cells again.

As for me I just keep it connected and have not had any issues, although some people are claiming the active cell balancers have a vampire/beserk mode where they can drain down a cell, so this is still to be investigated.

I also made a thread regarding this https://diysolarforum.com/threads/a...ancers-fail-and-kill-cells.41219/#post-521242

I watched OGG Andy's video on building the Sun Fun Kit, and the active balancer is located underneath the BMS. Disabling the active balancer would seem to require opening the battery case and removing the BMS in order to access the plug-in. Not exactly convenient. Could the active balancer be switched on and off through the BMS's bluetooth interface?

 

[Alkaline]

You could put a switch on the active balancer, or ask them to put a switch on it, this way you can turn it off without disconnecting.

 

[Alkaline]

I cna't find a picture but there is a little run jumper on the pCB, if you unsolder it you can attach 2 wires and then turn it on/off. any little dip switch will work.

 

[Alkaline]

here:

https://www.newark.com/switchcraft-conxall/46202lrx/switch-slide-spst-3a-125v-panel/dp/89K7662

 

[Browneye]

A bench type 10A power supply is like $60.
I'd be happy to ship mine to you to use for setup, send it back when you're done. Unless I build another battery I'll probly never use it.

I had never built a battery either, actually an electronics flunkie, but mine turned out just dandy.