it is measurable that on a stock 4r or stock gx460 the agm battery cannot be fully charged without a voltage booster. i also believe the lc250 cannot charge an agm battery correctly. this argument about agm charging has been going on for a while. the data and anecdotal evidence of many agm battery users in the 4r/gx forums that have killed agm batteries by not charging it correctly. my 4r with a 300 dollar northstar agm battery i felt a 50 dollar (at the time) booster was worth it. this very battery is still working at full capacity 8 years later.
Deep cycle agm battery replacement?
- Thread starter phantasticphil
- Start date
I’ll just note that the LC250’s hybrid charging system is completely different than conventional vehicles’ system. If a $50 device gives you complete peace of mind that you are going to have a superior performing and more precisely regulated charging system that will never overcharge your batteries then why not? Sounds like a deal to me!
On my previous vehicle (a Jeep JKU Rubicon Hard Rock) I had some parasitic drain in the form of a 2 channel dash cam with motion activated parking mode enabled. Parking in a busy location at work would always generate many clips of footage, so the camera would be running almost full time.
When the original battery gave up, I went with a Northstar AGM replacement in the OEM size. While the Jeep would produce 13.9-14.7 volts in normal operation for charging (regulated through the ECU), I would still find the need to top it off every month or so with an AGM compatible charger to maintain an optimal state of charge. I eventually replaced the Northstar with an Odyssey AGM in the largest size that could be shoehorned to fit into the battery tray for some more reserve and CCA, and did the same regular charging routine with this battery. I connected the charger at end of day once every 3-4 weeks and would see resting voltage at or above 13V after charging overnight so I had some reserve against the ongoing parasitic drain. Voltages would stay good for weeks after an overnight charge, and when resting voltage dipped towards 12.6 it was time for a top up. Not too big a deal to ensure the battery was always good to go.
While an AGM battery would be a nice upgrade for the Land Cruiser, I would still be looking to top it off in a similar interval to maintain optimal state of charge on the battery for getting the longest life and strongest voltage out of it at any given time of need. I'd consider it good routine maintenance for upgraded AGM batteries in most vehicles considering these batteries cost more than your typical replacement.
When the original battery gave up, I went with a Northstar AGM replacement in the OEM size. While the Jeep would produce 13.9-14.7 volts in normal operation for charging (regulated through the ECU), I would still find the need to top it off every month or so with an AGM compatible charger to maintain an optimal state of charge. I eventually replaced the Northstar with an Odyssey AGM in the largest size that could be shoehorned to fit into the battery tray for some more reserve and CCA, and did the same regular charging routine with this battery. I connected the charger at end of day once every 3-4 weeks and would see resting voltage at or above 13V after charging overnight so I had some reserve against the ongoing parasitic drain. Voltages would stay good for weeks after an overnight charge, and when resting voltage dipped towards 12.6 it was time for a top up. Not too big a deal to ensure the battery was always good to go.
While an AGM battery would be a nice upgrade for the Land Cruiser, I would still be looking to top it off in a similar interval to maintain optimal state of charge on the battery for getting the longest life and strongest voltage out of it at any given time of need. I'd consider it good routine maintenance for upgraded AGM batteries in most vehicles considering these batteries cost more than your typical replacement.
Thanks.. so there may be an AGM in Miss Daisy’s future yet..
Yes, the LC puts out charging power within the acceptable range for the AGM, but that doesn't mean that it charges optimally wherever you are within the voltage range. That's why I have two emails into Optima support to try to clear this up...
There are lots of possibilities:
- The Optima specifications state that 14.7V is required for "cyclic applications". I'm not sure exactly what cyclic applications are, but the 14.7V is what I would have expected for an optimal charging voltage (for an AGM). The LC clearly does not put out 14.7V during charging.
- Maybe the charging time is related to the voltage used during charging -- and if so, it may take longer to recharge the battery if your car is putting out a lower than optimal recharging voltage. In my case, this may mean that I don't drive it long enough to fully charge the battery.
- It may be that the LC's BMS (battery mgmt system) "finishes" charging and goes into float mode too early -- i.e. at a "full charge" voltage appropriate for non-AGM batteries, and the BMS may not continue charging long enough to bring the AGM up to it's expected voltage for a full charge (which I believe is higher than that for a non-AGM battery).
In my situation, for the use case I plan for the LC, I really need the battery to be kept fully charged, as I typically camp for several days and drain the battery while camping before I drive home. This has never been a problem for my previous cars -- a Subaru Forester, a Nissan Xterra, and a Jeep Cherokee -- but they all had large AGM batteries.
If I can't resolve this issue, I will need to take a big financial hit and trade the LC in for some other vehicle (presumably a non-hybrid vehicle, with a big AGM battery, like my Jeep Cherokee had). This would be very unfortunate.
Note -- Optima very clearly states that you need to maintain the battery voltage above 12.4V to avoid damage to your battery (sulfation)... There are several references to this on their support pages.
Last edited:
As a practical example of my 12V power concerns...
I haven't done ANY of the big power draw stuff that I'll be doing while camping, like repeatedly opening and closing the power liftgate, leaving the liftgate and/or doors open for extended periods, or using any of the switchable interior or liftgate lights. And, since I always camp at very high elevations, where morning temps even in the summer may get well below freezing, that will make life all the harder for the battery. (I live at 8600 feet, and only drive to higher mountains from here!)
- On Sunday night, I fully charged my battery using a Noco wall plug-in charger
- On Monday I did two short drives (10-15 minutes each)
- On Tuesday, I drove the car for over an hour (two half hour drives, to to take it in for service and then return home)
- On Tuesday, the service tech measured my battery charge at 85% (after I drove it for a half hour to the dealership)
- On Wed and Thurs, I did a total of four relatively short drives (10-15 minutes each)
- Today (Friday) my charge shows as 57%, and just opening and closing the passenger side door dropped the voltage from 12.5 down to 12.3 volts. (My car came with illuminated front door sill lights that are always on when the door is open. I'm pretty sure that this voltage drop will gradually "recover" over the next hour or so.)
I haven't done ANY of the big power draw stuff that I'll be doing while camping, like repeatedly opening and closing the power liftgate, leaving the liftgate and/or doors open for extended periods, or using any of the switchable interior or liftgate lights. And, since I always camp at very high elevations, where morning temps even in the summer may get well below freezing, that will make life all the harder for the battery. (I live at 8600 feet, and only drive to higher mountains from here!)
Last edited:
That may be an idea, especially if I start running a lot of devices of one sort or another.
Right now, I'm keeping my sights low and staying mostly focused on all the drain from the LC onboard systems and devices, for which I have limited or no control. I've already done as much as possible to minimize the persistent drain from normal use, but there is more I could do (like disconnect the front door sill lights, which are very bright, and always on when the door is open, day or night).
There are other options that I've only briefly thought about, but haven't yet fully run down:
- I could just leave the hybrid system in Ready state for a while (whether or not the engine is running), and it can recharge the 12V battery from the traction battery as it sits at my campsite. But it may not fully charge the battery (as we've been discussing), so this would only bring the battery up to a certain level. And it would cause the engine to cycle on and off, using up valuable gas (which is a problem with the LC's small gas tank). This also brings up the question of what happens if you fully discharge the traction battery? (see entry #79 above...)
- I could bring a wall plug in charger, and plug that into the LC and charge the battery. This would allow me to fully top off the 12V battery, but it may take some time to do this (a few hours??) Again, this would require leaving the hybrid system on for an extended period, which if nothing else will consume gas as the engine cycles on and off.
From what I have read, a high charge rate (cyclic) is for deeply discharged battery, not one that has normal 12V+ output.. Constantly charging at around 15V will likely do more damage to a battery than good. This is probably why AGM batteries have usually worked great for the past few decades by being maintained with normal OEM alternators. If your battery becomes deeply discharged, you can always plug it in to a AGM charger that a battery manufacturer recommends.
You could look into installing additional batteries for more reserve power, which is common in overlanding, I think there are threads here about those installs. Maybe a second battery could be lithium, which would be a fun/interesting combo!
Last edited:
Obviously the 57% could be concerning, but the 85% may not be. It may be how Toyota programmed the BMS. Obviously not a LC, but the newer F150 BMS only charges the battery to 80%, people have been Forscaning (a program that allows you to change settings, etc, fairly deeply) the BMS to up it to 90%.
This is an interesting thread and over my head, but I’m glad I didn’t go buy a AGM replacement, just from the information I sort of understand.
I bought a Noco G10 because of the battery conversations on this forum.
It’s kinda over my head too, but I’ve been reading about AGM’s since ~2008, when I had to replace my battery in my R1200GS Adventure (which was covered under the factory warranty at the time). I learned back then, that when not in use, to just plug the battery into a battery charger built specifically for that battery. I usually get 5+ years out of the Duracell AGM’s in my bikes, Gravely mower, Mule, by using the Duracell charger and plugging it into each machine, rotating around them.
As for Miss Daisy, I plan on attaching a pig tail to the battery, or under the hood, so she can easily get plugged in when parked for days on end.
Yea, the Noco G10 is probably in my future as well.
My Noco AGM charger came with a pigtail that plugs into the harness where the battery terminal clams attach (same plug, so you can use clamps or pigtail). On my Jeep the battery terminals were more convenient. On the LC, the pigtail makes more sense with the "tucked away" nature of the battery.
Yep, pig tails are very useful -- I have two of 'em attached to my battery, a Noco plug for my Noco wall chargers, and a SAE plug for my portable solar charger.
This is all new to me as well -- I'm still at the I don't know enough to know how much I don't know phase!!
To some extent, I agree, the 85% probably isn't as concerning, because for whatever reason (either because the BMS doesn't want to fully charge the battery, or because it thinks the battery is a flooded cell) the BMS may be doing that intentionally. But that still seems like a big SOC drop from Monday morning to Tuesday morning. I don't know how much of a load the Toyota tech put on the system before he measured the SOC, but 15% seems like a lot to me.
Re the low charge that I measured this morning, to further confuse things I'll mention that I get very different SOC readings from different measuring devices. I assume that there is no specific way to measure or assess SOC -- it's more of a concept, as opposed to a standard set of specific quantitative measurements that roll up in a defined way into an overall percentage score.
I know for instance, that my battery monitor constantly broadcasts SOC and voltage, whereas with my battery tester, measuring SOC is done by running a specific test that first requires input of a battery capacity parameter (e.g. CCA), and then when you run the test it puts a load on the battery (I can see the voltage of the battery drop at the same time). Clearly, these two devices approach SOC differently. And the Toyota tech that measured my battery was using an altogether different battery tester (a fairly large "professional" one).
For SOC, I trust my battery tester more than my battery monitor (although both of them produce exactly the same results for voltage). I must admit that the 57% I reported this morning was from my battery monitor (since that is so much easier to use -- just pull up the app on my phone, as opposed to digging into the battery compartment in order to hook up and use my battery tester).
In any case, today I drove the car for a total of almost an hour and a half, and at this point, my battery tester (which I trust more) is showing an SOC of 82% (my battery monitor is showing only 68%). I assume that an hour and a half would have been long enough for the system to fully recharge the battery, assuming that it wanted to (i.e. that it doesn't automatically cut off at some pre-determined less-than-100% charge level). Or, it could be that it finished the charge phase early and moved on to float because it assumed that it was charging a flooded cell battery. Or that the charging voltage was too low. Or who knows, it could be something else altogether!
Incidentally, I don't think that my battery is defective. My battery tester has consistently showed that the overall "Health" is at 100%. I know that it looks at various measured battery parameters (such as internal resistance) to arrive at this value. The Toyota dealer also measured the health of my battery to be at 100%.
I had no idea that I'd be spending this much time trying to sort things out with a brand new car...
Not new to me, but I still feel like I don’t know enough.
Note that the LC owner's manual specifically states that you should not use a charger that puts out more than 5 amps (if I recall correctly, it says that higher amps may cause your battery to explode!!!!!!)
Last edited:
I thought that I had read that! I should probably revisit that seciton of the owners manual.Note that the LC owner's manual specifically states that you should not use a charger that puts out more than 5 amps (if I recall correctly, it says that higher amps may cause your battery to explode!!!!!!)
View attachment 39813
Oh, lovely... and here I got the 10A because it was supposed to be faster. The Noco Genius is supposed to be 'smart" though. I regret tossing the box now.Note that the LC owner's manual specifically states that you should not use a charger that puts out more than 5 amps (if I recall correctly, it says that higher amps may cause your battery to explode!!!!!!)
View attachment 39813
I swapped the OEM AGM H6 for a H8 in my pick up.I'm not leaving mine hooked up FWIW.
Last edited:
Can’t say for anyone else, but I do know………….. OEM flooded battery, while tested good, would go flat after just a few hours of the rear hatch being open. Replaced the OEM with an Optima, still draws down with the rear hatch open, but not to the point of a non-start. Installed a solar charger, don’t know(or care) if it’s rated for the AGM charge rate, but it keeps the battery at a level where I no longer have “top it off” with an external trickle charger and haven’t had an issue.
Similar threads
