Author Topic: Changing from SLA to LifePo4 batteries  (Read 18058 times)

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Offline dochubert

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Changing from SLA to LifePo4 batteries
« on: January 27, 2021, 09:11:38 pm »

I think in my other posts I mentioned that my 3 year old SLA batteries were starting to fail.  I had two separate banks. My main bank that runs my house was (16) 200ah SLA 12v batteries set up in 4 sets of 4 in series for a 48v bank.  They still had lots of umph, but because there were 4 in series (for 48v in each of 4 strings in parallel) as they were discharged they didn't discharge evenly.
So my actual usable capacity was seriously diminished.
I ended up selling them to a guy across town who is going to use them in 12v banks.  He should get quite a bit of use out of them that way.  I thought about doing something like that with them but decided I didn't want to mess with them.

I made a good deal on some used BYD LifePo4 24v 220ah packs from Batteryhookup.com.  After some mishaps with shipping companies I then had to repair 4 of them damaged in shipping.  The first pic shows the shattered pallet they arrived on.




I ended up arc welding the terminals back in place using a 12v gel battery and a carbon rod.  Kind of a pain but it worked on all but one.  Batteryhookup replaced the damaged packs so by repairing the damaged units I got 4 extra packs, so a net gain.

The next challenge was to get these heavy packs (125lbs per pack) into place for use.  I had to beef up the shelf where the upper 2 stacks of 2 sit.  Then had to build custom ramps and rig a chainfall to get them installed.




That took awhile as I have no help and have to figure out how to safely do it all solo.  Got them in.  Didn't kill myself or drop anything so its all good.



The second bank is 24v so 6 packs in parallel.  I put them on their sides and strapped them together once in place.



These required a different custom ramp but only had to lift one at a time instead of stacks of two. 

For both banks I used flattened copper thick-walled pipe for bus bars.  I had picked up a coil of used air conditioner copper at a yard sale last summer.  Peel off the insulation, cut to length and flatten with a vise and mallet.  Beats buying copper bar stock or using/buying welding cable.

Next post I'll talk about hookup.
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #1 on: January 27, 2021, 09:13:34 pm »
All the pics are flipped 90 degrees left.
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Offline Pete

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Re: Changing from SLA to LifePo4 batteries
« Reply #2 on: January 28, 2021, 01:10:53 am »
Hi Doc well done on getting the batteries in place. They can be pretty hard to move about. I have VRLA batteries and each cell weights about 36 kg. I put them in wooden boxes with lids, Luckily I could pick each cell up individually and put them in the box before connecting them.
Seems that the USA needs a new voting system
When George W Bush beat Al Gore it was claimed that the voting machines were rigged.
When Trump won it was claimed that the Russians influenced the election
Now when Biden wins it is claimed to be a fraud too.
Either people love making spurious claims or your system is broken.
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Offline ClockmanFrance

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Re: Changing from SLA to LifePo4 batteries
« Reply #3 on: January 28, 2021, 02:44:32 am »
LifePo4,   Nice pics,   

I am very interested to see how you get on with these used LifePo4 batteries.

Please keep us informed.

Offline solarnewbee

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Re: Changing from SLA to LifePo4 batteries
« Reply #4 on: January 29, 2021, 09:06:35 am »
Hey Doc,

Nice work! I just recently sold some batteries very similar to those. Inter-connected with aluminum buss bars. Battery hookup ended up refunding quite a few folks for lack of kWh advertised. I got more back than I paid so it was a win. You can see mine were in A server cabinet and my son and I had hell loading them up as they were 168lbs. I like your ramp, I didn’t have the room that. I found that 57v was the sweet spot(max charge) before cell voltages got wacky. David Poz on YouTube, if you’ve seen him, paralleled his and it made a big difference.

I know your going to be very happy with the change.

Best of luck!
SN

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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #5 on: January 29, 2021, 10:14:53 pm »
Hi guys,
The second bank running my water heater setup is 6 modules in parallel for 24v.  They stay pretty even so far. 
The main bank, being 48v, is going to be more challenging.  Yes I've watched David Poz' videos on them.  He did a great job and I learned a lot watching him before I started with mine.  I'm not doing things quite the same as he did, but not that different either.  Since there is limited sun in January here, it's been fairly easy so far.  16s bms for balancing on each of the four 48v parallel sets.  Haven't got balancing on the 24v bank yet, but working on it.  To balance those I either have to parallel all the cells across all 6 or put a separate bms on each.  Since I'm only using the bms for balancing, not charging or discharging, I'll probably go with a bms on each.  Still pondering...

Ah, politics.
140 M registered voters.
Trump officially got 74 M.
Biden got 80 M.
That's 154 M total votes "counted" out of 140 M?
Yeah, I'd say it's broken.  Corrupt beyond repair.
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #6 on: January 30, 2021, 05:42:28 pm »

AsI mentioned, I used flattened thick-wall 3/4" copper pipe for my bus bars.  1 pos and one neg.  Bought large copper lugs from home depot to put on the battery posts, then bolted thru to the bus bar.  Ran new #6 copper wire to each of 4 charge controllers.  Still using xantrex c40 for charging.  Bulk charge set to 55.2v and float at 54v.  As mentioned, charging above 56v leads to unbalances in cells so will try to stay in the narrow range and see how that works out.  No higher than 56 and no lower than 48v.  Usually between 52 and 55v

8818-0

Added a temp control and 4 small fans to the charge controllers.  Last summer I just set a desk fan blowing on them.
About time I did something better.

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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #7 on: January 30, 2021, 06:11:42 pm »

Next was connecting up the bms'.  Too much trouble using the connectors on the BYD modules so just cut the wires (1 at a time) and connected to the bms wire harness.  One 16s bms to span the 2 byd modules in each 48v leg. x4 so lots of little connections.



Just used silicon to stick the bms to the module case.

8822-1

8824-2

Then added a little blue voltmeter to each module.  They are not super accurate but gives me a ballpark idea of whether cells are even at a glance.  Used some plastic wire looms to try to dress up all the leads.

8826-3
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #8 on: January 30, 2021, 06:48:31 pm »
Finally, I added a little blue led to the right of each bms.  Since these bms are relatively cheap, I can't monitor cell voltage directly, and I'm not using them for charging/discharging, only for balance.  The led just connects to the unused bms' charging lead so it will always be on if the bms is in normal mode.  If a cell goes too far out of spec the blue led should go out, indicating the bms has 'disconnected'.  Same if the total module charge gets too high or too low.

8828-0

This summer when I will have 120 to 150 amps going in (thru 4 controllers) I'm hoping these will help me make sure the parallel legs are charging evenly.  Also why the charge controllers are set just below 56v instead of the 58-59v the system should be able to accept if it was new.  As for now (January) I'm happy on days where there is enough sun to run the house during the day.  And of course if the grid goes down I can run for a few hours with minimal usage.
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Offline WooferHound

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Re: Changing from SLA to LifePo4 batteries
« Reply #9 on: February 02, 2021, 09:02:34 am »
Wow , Too Cool . . .
Nice to see someone else converting Lead Acid to Lithium.

Would love to hear about the differences you have seen  between the two systems ?
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #10 on: February 02, 2021, 02:52:29 pm »

I have to admit that I know almost nothing about lithium batteries as far as practical experience goes.  I'm learning as I go.  Did a lot of reading and watched many videos by other people using lithium.  Opinions and advice seems to vary widely.  Learned all I could then made my own decisions.  Many could prove wrong...

Impressions so far;
I like that voltage stays pretty steady under varying loads.
The fairly narrow voltage range worries me some but so far not an issue.
Cell balancing is something I think I still have a lot to learn about.  Will probably end up changing what I'm doing now.
I love that too low a charge level doesn't do permanent damage.
I like that there's no outgassing.
I like that fire hazard is minimal.
Looking forward to a longer lifetime for lithium. (Only got 3 years out of the SLA batteries)
My Inverter actually seems to run cooler, I think because of the more stable battery voltage level.
My other controls cycle less, same reason.
Hadn't thought about it till now, but output AC voltage is probably more stable and steady for same reason.  Less wear on household electronics and appliances.

I'm just getting started, and summer is months away, so I've no doubt I will have more comments as my experience increases.  Happy so far.
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #11 on: February 10, 2021, 09:19:41 pm »
Hooked up a couple of cell monitors to the Lifepo4 modules of my 24v water heater battery bank.  I bought two different types to check out.
The first one is nice in that it gives a single screen view of all 8 cells at once.  It is supposed to balance cells. 

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Its called an ISDT BG-8s.  Here's a link if anyone is interested in looking it up.  I paid $22.  It's since gone up to $35.

https://www.ebay.com/itm/ISDT-BG-8S-Smart-Battery-Checker/372744580497?hash=item56c94eed91:g:hacAAOSwuA1dWfzY

I ran this one for over 24 hrs on my most uneven module.  Didn't see much change so not that impressed with its balancing.  I realize these are big batteries so balancing by small balancers will necessarily take time.  I might need to get more substantial balancers.

The second cell monitor I tried is called a Cellmeter8.  It just has a simpler lcd readout (not all cells displayed at once) but does show minimum cell and maximum cell and a screen that displays the min-max difference.  Kinda cool.

[ Specified attachment is not available ]

[ Specified attachment is not available ]

These gadgets are cheaper than the other one at about $10-11 each.  Link below;

https://www.ebay.com/itm/Battery-Meter-Checker-Tester-CellMeter-7-8-Capacity-LiPo-LiFe-Li-ion-NiMH-Nicd/133627203511?hash=item1f1ccd4fb7:g:KwYAAOSwtCBf8rug

Left it on all day today and balance has noticeably improved in just that time.  Guess which one I'll get more of?
I like the display on the ISDT unit better but like the balancing on the Cellmeter8 better.  I want each module on the 24v bank to have a balancer, so ordered a few more Cellmeter8's.

The 48v bank is set up for 16s bms so can't use these for that bank (without re-doing all that wiring I spent hours hooking up).  Nobody seems to make anything like a "cellmeter16".  I know some of the very expensive bms' have bluetooth so you can read it on your cellphone.  Times 4 for 4 banks.  At this point not willing to spend that much.

I also have an 8s Daly like the 16s units on the 48v bank.  So I'll hook the 8s up to one of the 24v modules and see how it does versus the cellmeter.  Time will tell.
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Offline WooferHound

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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #13 on: February 18, 2021, 03:51:15 pm »
Thanks for the info and links, Wooferhound.  Since my last post the cellmeter8 balancer hasn't been able to keep up and balancing is still not great.  Not terribly bad but not great. 
So ordered a couple of the ones in your first link and will give them a try.  I can't really go to a 5a balancer without going to bigger wire size, and that's next to impossible for now.  (Moving those big lifepo4 modules again is something I don't want to think about.)
So I should be ok with a 1.2a balancer with current wire size.  Assuming 1.2a is enough to do the work.  Guess we'll see...
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Offline dochubert

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Re: Changing from SLA to LifePo4 batteries
« Reply #14 on: March 16, 2021, 06:14:15 pm »
Got the 2 1.2a active balancers recommended by Wooferhound and hooked them to the two worst modules.  Of course they haven't instantly put them in balance, but they seem to be working fairly well (a week or so of use so far).  The used Byd modules tend to go out of balance when at the top end of charge.  In my case, above 27v.  Battery hookup recommends using them in the 24-27v range, probably for that reason.



So they get out of balance somewhat near the top end, the balancers work and they're within acceptable balance eventually.  Since its early spring, I have longer Sun days ahead.  We'll see how they do when the batteries stay at fully charged for longer each day.
Anyway, I ordered 4 more so there will be one for each of the 6 modules in the water heater 24v bank.  The 48v bank is more challenging.  I already wired up the 8 modules in 4 48v sets, with a 16s bms for each.  Probably will just put a 16s active balancer on each set in addition to the bms.
I am considering buying 8 more of the byd modules to double the size of the bank.  If I do, I will probably do them differently than the existing set.  Before mounting them, I think I will add wires to allow paralleling all the cells of all 4 48v sets, then use one of the 5a active balancers for the whole thing.  Suspect I'll get better results.
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