12V battery replacement

[Maquis]

Interesting. I haven’t seen a cutaway. Thanks.
I think then I’ll stick to replacing my AGMs every few years.

Basically run of the mill cells and a circuit board held in place with spray foam.

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[Robert1380]

Basically run of the mill cells and a circuit board held in place with spray foam.

So those Ohhmu batteries aren’t any good?

 

[SpaceEVDriver]

Basically run of the mill cells and a circuit board held in place with spray foam.

No hard mount on that circuit board!? It would jar loose in the first week of owning it with my road and the use I put my truck through. Nothing to stop the circuit board from contacting the terminals.

You couldn’t pay me to put that in my truck.

 

[johnnyonetime]

No hard mount on that circuit board!? It would jar loose in the first week of owning it with my road and the use I put my truck through. Nothing to stop the circuit board from contacting the terminals.

You couldn’t pay me to put that in my truck.

Not worried at all, 50k miles and 2 years later it still works every time I push the button!

 

[SpaceEVDriver]

Not worried at all, 50k miles and 2 years later it still works every time I push the button!

I am truly happy for you that it hasn't caused any problems for you.

I'll still keep using the AGM until there's a better solution that I trust.

 

[Maxx]

Some context might help provide color to this conversation.

Looking at individual cells nominal and 12v cells in series voltages can help explain how different or similar a lead acid, lithium iron phosphate, and lithium ion batteries are.

Nominal cell voltages:

Lead acid = 2.1 v
Lfp = 3.2 v
Lithium ion = 3.6 v

Nominal voltages of cells in series to fit a 12 volt battery application:

Lead acid (6) cells = 12.6 v
Lfp (4) cells = 12.8 v
Li (4) cells = 14.4 v

So lithium ion is quite a bit different than lead acid. But Lfp is pretty close to lead acid when comparing the whole battery voltage in series.

Without getting into the specifics of Ford's lead acid charging algorithm, you can at least see how a 12v Lfp battery charged with a 12v Lead acid charging setup would be close enough to not necessitate changes to charging voltages.

This post isn't the whole enchilada per se, but I am trying to illustrate that lithium iron phosphate 12v batteries aren't radically different than your standard lead acid 12v battery we have all known forever. The guts are different, cell balancing is more important in Lfp, but 12.6v vs 12.8v nominal is only 1.6% difference in amount...

‘Thanks for a very informative post. It would be nice if @johnnyonetime could measure the voltage at battery terminal with negative before and after BMS. When the truck has been off for a while and when it is on and share the results so we can compare with our original batteries connected.

No hard mount on that circuit board!?

In the company video, internals don’t look that bad. The board seems to be screwed in. Not sure if this is a newer version or a different model. With all the Chinese (I assume) written on the cover, it may even get more expensive than $500. Their Sodium batteries are $100 less expensive.

Min: 6:58

 

[SpaceEVDriver]

Hmmm. Maybe they’ve improved over the past few years. Dunno.

I do know that I wouldn’t do a direct replacement of an AGM with a Lithium battery without some kind of system in between to convince the Ford BMS that it’s got the right battery. The charge curves are so different and with the very flat charge curve of the lithium battery, the voltage level of the lithium will make it appear that it’s almost full when it’s almost empty. Maybe the Ford BMS is smart enough to only care about counting coulombs and doesn’t ever lose track or need to measure voltage, but I’m doubtful. I’d be happy to be wrong.

(Yes, the y-axis is scaled to 58 volts—that’s irrelevant for the shape of the curve. Each cell has the same shape).

 

[Lytning]

I bought and installed in my Lightning an Ohmmu Li-H3-BH (LFP) 12 Volt Battery two weeks ago, based upon positive user comments on this forum. I just returned from a 25 mile errand trip. Ohmmu 12 volt SOC, easily accessible in the Ohmmu app, is at 100%.

Among several reasons for rewarding Ohmmu with my purchase, them delivering an easily accessible 12 volt battery SOC was near the top of my list ... something that @Ford Motor Company would not do in over 3 years.

Now, if Ohmmu sold BlueCruise 1.4 ...

 

[chl]

All LFP batteries have an internal BMS.

Since they are being used to swap with conventional or AGM lead acid batteries it makes sense they would include the BMS as a component, for safety and longevity, by balancing the cells.

They'd still need to be designed to match the charge curve of the thing they are put in or used with to, have optimum performance and longevity I'd think.

Years ago when my battery powered lawn mower's batteries died for the second time (24V lead acid pair in a Ryobi 48V mower RY14110) I bought a pair of 22V LiPo batteries (Turnigy 5000mAh 6S 40C Lipo) and a pair of chargers (SKYRC IMAX B6AC V2 Professional Balance Charger/Discharger).

Balance charging before mowing (about 45 min) and balance discharging after for storage until next mowing, is time consuming and the LiPo batteries have to be charged/dicharged and stored in fire-proof-ish containers, just in case.

Unlike a vehicle, the mower itself doesn't have a charger built in, but the SKYRC's will work with Lithium Iron Phosphate batteries and several other types.

The problem is 24V LFP batteries are larger and more expensive than the LiPo I have, and I'd need two x 24V or four x 12V LFPs, which would cost more than a new inexpensive mower (SunJoe for example) which is all I need.

I have been slowly eliminating the monoculture lawn for low maintenance ground cover anyway.

If it comes to fruition, I imagine the CATL sodium ion battery could make other Li batteries obsolete, and be a big boon for solar as well as EVs and general battery use.

Hopefully tariffs on China will be gone by then.

 

[chl]

Some context might help provide color to this conversation.

Looking at individual cells nominal and 12v cells in series voltages can help explain how different or similar a lead acid, lithium iron phosphate, and lithium ion batteries are.

Nominal cell voltages:

Lead acid = 2.1 v
Lfp = 3.2 v
Lithium ion = 3.6 v

Nominal voltages of cells in series to fit a 12 volt battery application:

Lead acid (6) cells = 12.6 v
Lfp (4) cells = 12.8 v
Li (4) cells = 14.4 v

So lithium ion is quite a bit different than lead acid. But Lfp is pretty close to lead acid when comparing the whole battery voltage in series.

Without getting into the specifics of Ford's lead acid charging algorithm, you can at least see how a 12v Lfp battery charged with a 12v Lead acid charging setup would be close enough to not necessitate changes to charging voltages.

This post isn't the whole enchilada per se, but I am trying to illustrate that lithium iron phosphate 12v batteries aren't radically different than your standard lead acid 12v battery we have all known forever. The guts are different, cell balancing is more important in Lfp, but 12.6v vs 12.8v nominal is only 1.6% difference in amount...

The Ford AGM battery may have a different terminal voltage than the 12.6V though.

And the critical factor is really the charging current/voltage curve difference, which is why the BMS is so important for the LFP.

An AGM-compatible battery charger sends more amps into a lead-acid battery while keeping the voltage less than 14-15 volts. AGM chargers go through the three charging phases (bulk, absorption and float) just like a regular charger. However, a regular charger could exceed 17 volts when charging a battery.

Which is why you need a charger compatible with an AGM battery - most newer ones seem to be.

If kept on an AGM battery maintainer, the Ford AGM should last longer than a normal lead acid battery, the problem has been the Lightning didn't keep the AGM fully charged and would let it fall below 50% which is a no-no for AGMs.

In case anyone wants to do that with their Lightning, hook the maintainer up to the jump terminals under the top panel on the passenger side of the Frunk, or to the proper terminals inside the battery compartment (the blue circles not the red X's):

 

[chl]

I have a 48v Ryobi myself, that's when I was introduced to the, at that time, fairly new LFP technology. I put 4 12v 50ah lfp in it to replace the agm it came with, still running strong.

The mower has power now that it didn't have brand new, I tried using the mulch plug but it kept bogging down so I took it off. Now with lfp I'm able to reinstall it and it doesn't bog at all.

I did have to purchase a new 48v charger for it due to the difference in chemistry, in my work van I put the same battery in and the alternator keeps it charged with no issue.

Now those same batteries are connected in parallel with my home solar storage bank and the inverter keeps them all charged.

Best part about the lfp is it doesn't care if you always run it flat, it'll recover on it's own and it doesn't care if you keep it charged at 100% either. The built in BMS keeps it happy.

Ha, small world!

I paid $420 for the mower originally in 2010 - omg!

Well my first EVSE (GE Watt Station) was $1000 in 2011 for a 30A max charge current for my $32k 2012 Leaf with barely 100 miles range on 24kWh battery charging at 3.3kW. Crazy!

The original batteries for the mower (April 2010) barely lasted a year - well they lasted a week past the 1 year warranty (May 2011) expiration. So I bought a new one ($135 ouch!) and that one lasted one day under the 1 year warranty (May 2012) even though I babied it.

So I got a third battery free from Home Depot - the manager could not get the SKU to work in his computer so he just gave me the unused one they had in the display model. I manged to get that one to last until the 2020 mowing season after which I changed to the LiPo setup.

The Ryobi mower manual said to leave the battery on the charger all the time, so I assumed it was a trickle charger when it got to full charge, but I believe it overcharged the first one because that one swelled up before it failed.

Yes, the LiPos also gave it a lot more kick, almost too much - with the wheels powered I have to jog to keep up, lol.

I don't recall the LFP's being readily available at the time I modified the Ryobi (circa 2000), if they had been and the price was competitive, I'm pretty sure I would have opted for LFP over LiPo.

I think I paid somewhere around $200 for the 2 chargers and 2 LiPo batteries, which at the time was less than the cost of a new e-mower.

But frankly, it gave me the willies whenever I used the LiPo batteries - I guess I watched too many videos of LiPo fires and explosions? They still work well, but they make me nervous as they age.

When there was a 50% off sale with free shipping last spring(2025), I bought a little SunJoe mower for a little over $120. No power wheels, but otherwise suits me fine. Very light weight - remember how heavy the Ryobi was with the lead acid battery pack?

I have had good results with SunJoe/SnowJoe products and the price is always right (cheap). I have a little pressure washer (1600 psi on sale for $62.50 at Home Depot in 2022) and a corded snow thrower (SnowJoe SJ615E 15" $110 at Home Depot 2023).

I guess some day we may be switching to sodium ion batteries if things go well.

 

[Maxx]

the voltage level of the lithium will make it appear that it’s almost full when it’s almost empty. Maybe the Ford BMS is smart enough to only care about counting coulombs and doesn’t ever lose track or need to measure voltage, but I’m doubtful. I’d be happy to be wrong.

If that was the case, @johnnyonetime battery would not reach 87% SOC as he showed earlier. In the situation you are describing, Truck would stop charging the battery long before then. So something in this setup must be smart enough to keep the electrons flowing.

I bought and installed in my Lightning an Ohmmu Li-H3-BH (LFP) 12 Volt Battery two weeks ago, based upon positive user comments on this forum. I just returned from a 25 mile errand trip. Ohmmu 12 volt SOC, easily accessible in the Ohmmu app, is at 100%.

Among several reasons for rewarding Ohmmu with my purchase, them delivering an easily accessible 12 volt battery SOC was near the top of my list ... something that @Ford Motor Company would not do in over 3 years.

Now, if Ohmmu sold BlueCruise 1.4 ...

If you have car scanner, or can look online in your account, can you share what Ford thinks your SOC is vs your 12V battery? If the SOCs match?

If it comes to fruition, I imagine the CATL sodium ion battery could make other Li batteries obsolete, and be a big boon for solar as well as EVs and general battery use.

OHMMU is already selling Salty batteries at $100 less.

the problem has been the Lightning didn't keep the AGM fully charged and would let it fall below 50% which is a no-no for AGMs.

They must have changed that with one of the updates. I saw for the first time a few days ago my truck trying to protect 12V battery by shutting things off when it's SOC was around 50%.

 

[SpaceEVDriver]

If that was the case, @johnnyonetime battery would not reach 87% SOC as he showed earlier. In the situation you are describing, Truck would stop charging the battery long before then. So something in this setup must be smart enough to keep the electrons flowing.

Yeah, that’s my point. There seems to be something going on in the Ohmmu BMS that’s converting the lithium battery voltage / SOC to reflect the voltage / SOC of an AGM.

But buying just any lithium battery that has the right size without the translation layer would likely lead to premature failure.

 

[chl]

OHMMU is already selling Salty batteries at $100 less.

They must have changed that with one of the updates. I saw for the first time a few days ago my truck trying to protect 12V battery by shutting things off when it's SOC was around 50%.

Already!? OK, have to check it out.

Yes there was an update recently that changed the program for maintaining the 12V - but does it use the DC-DC converter to top off the AGM? All lead acid batteries prefer 100% charge for longer life...

 

[chl]

Lipo's are what we use in all our drones, those suckers are extremely volatile. Those are not Li-ion or Lifepo4 (LFP).

Lithium polymer (Lipo), I had one that swole up so I was going to recycle it then decided to see something, electronic equivalent to "Hold my beer" I set it out front on concrete away from anything flammable, and poked it with the tip of my knife when all hell broke loose!!!

Made me jump back I'll tell ya that lol . That thing spewed smoke like a jet engine then it shot flames out and I came inside and watched the rest from the living room, haha. Never actually exploded just spewed and popped a few times then burned itself out. Thermal runaway is spooky.

I don't play with those any more than I have to, haven't flown any of my drones but the ones I have, all have built in bms, those packs you buy from the hobby shop for racing drones and really anything RC in genera,l gotta be careful with them, once mine get so much as a dent in them, they go straight to the recycler.

Yes, they make me nervous for exactly that reason.
I keep them in a bat case in a cool place.

When I use them in the lawn mower they are cushioned with bubble wrap and inside fire-bags but every time I go over a bump, I sweat bullets.

Been thinking about recycling them before something bad happens!

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