12V battery replacement

[RLXXI]

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.

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.

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[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.

 

[RLXXI]

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.

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.

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.

 

[RLXXI]

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.

The voltages are close enough to not make a difference. The main difference being charge/discharge curves et al.

 

[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!

 

[SpaceEVDriver]

The voltages are close enough to not make a difference. The main difference being charge/discharge curves et al.

The top-end and bottom-end voltages are similar. But the voltage of a Lithium battery at 25% looks the same as the voltage of a Pb-A battery at 90%. So when the lithium battery is at 25% and is still providing a voltage similar to a 90% SoC AGM, the truck won’t think it needs to charge the battery.

 

[chl]

Already!? OK, have to check it out.

I have time to wait for the price - $379 - to come down - 3 year B-B warranty ends Jan 2027, may need a replacement AGM by then when it fails, sodium (or whatever the best replacement is at the time).

https://www.ohmmu.com/product-page/12v-sodium-battery-for-ford

 

[RLXXI]

The top-end and bottom-end voltages are similar. But the voltage of a Lithium battery at 25% looks the same as the voltage of a Pb-A battery at 90%. So when the lithium battery is at 25% and is still providing a voltage similar to a 90% SoC AGM, the truck won’t think it needs to charge the battery.

And it won't until it needs it. They charge pretty fast being my experience.

 

[Maxx]

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...

As far as DC to DC goes, it must be. All power sources in the truck are DC (HVB and LVB). I didn't get to check to see what the threshold at which the charging kicks in now after the update. I immediately turned on the truck as soon as I saw 50% SOC and got it up to 73% and on my next drive to 84%.

My latest update has also made the truck turn on lane keep assist everytime I turn on the cruise control. It is annoying the heck out of me. Not sure if I can change the behavior in a setting somewhere or I am stuck with it.

 

[El Duderino]

The top-end and bottom-end voltages are similar. But the voltage of a Lithium battery at 25% looks the same as the voltage of a Pb-A battery at 90%. So when the lithium battery is at 25% and is still providing a voltage similar to a 90% SoC AGM, the truck won’t think it needs to charge the battery.

Pretty flat discharge curve. I see your point now.

 

[SpaceEVDriver]

Pretty flat discharge curve. I see your point now.

Glad the point made it somewhere.

A Li battery on an AGM BMS could easily be left in the 0% to 25% range. It is also likely never to reach full charge because a 100% SOC Li battery has a higher voltage than a 100% SOC AGM battery.

And because of the steep drop at the bottom end of the Li battery’s SOC curve, there could be very little warning that the Li battery is about to be dead. So a Li battery on a Pb-A BMS might only have ~25% of its Ah rating available for regular use. You might need a 70-140 Ah Li battery to get the same Ah of use as you would in the H3 in the Lightning.

Coulomb counting works much better for Li than for Pb-A and voltage measurements work much better for Pb-A than for Li (see your chart and the one I posted earlier). So the BMS charging strategy for the two batteries is likely different.

Again, this is assuming one just puts a random Li battery in place of the H3 AGM that came from the factory. If there’s a translation layer between the Li battery and the truck’s LVB BMS, that may mitigate this concern.

 

[Zprime29]

My latest update has also made the truck turn on lane keep assist everytime I turn on the cruise control. It is annoying the heck out of me. Not sure if I can change the behavior in a setting somewhere or I am stuck with it.

Several threads about this, one of the most annoying changes @Ford Motor Company made. Should have left them as independent toggles. I tried turning it off, but then I can't get Blue Cruise to activate.

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