Deep cycle agm battery replacement?

[geomars]

Is a shunt the same as a dummy load?

Shunt is a general term meaning to divert flow of current. For the purpose of battery monitoring, a shunt is a very low resistance resistor in series with the load. By measuring the voltage drop across the resistor, the current into the load (or into or out of the battery) can be measured.
Here is a discussion of how it works:

Battery shunts for current monitori – what They are & why you need one -

Electrical shunts explained. 100 Amp/100mV, 500Amp/50mV Ohm's Law battery monitor Trimetric Victron BMV Renogy

www.bogartengineering.com

 

[Mikie]

So far, my experience with an AGM battery (an Optima Yellowtop DH6) has been that the car does not seem to be able to keep it fully charged. I CAN fully charge it with my Noco wall plug-in charger, but in the days after doing so it fairly quickly loses SOC, even tho I drive every day. This is presumably due to the fact that the 14.4V put out by the hybrid system is not quite enough to keep the AGM topped up.

A good example is that day before yesterday I fully charged the battery (using my Noco charger set to AGM). Then, yesterday I drove down to the Toyota dealership, a little over a half hour. During my vehicle service, they had the doors and liftgate open, etc., as expected. The tech tested the battery -- and although it tested at 100% health, it was only 85% charged. So as I see it, either:
- The battery is defective and cannot hold a charge, or
- The car should have been able to keep the battery topped off on the drive to the dealership, but was unable to do so (I assume because it was only putting out 14.4V).

Since the battery is new and tests at 100% health (measured by both my tester and the dealership's tester), I assume that the battery is not defective and the issue is the low voltage 12V battery charging by the hybrid system.

Interestingly, there is a recent post (attached) on another forum about a guy that changed from a flooded cell to an AGM with his 4Runner. This substantiates what I wrote above...

Yesterday, I asked my tech at the dealership about the possibility of a configuration setting for the car which would change the charging profile to AGM -- and unfortunately, there isn't such a setting. Hard for me to believe that Toyota doesn't provide support for AGM batteries -- kind of like telling us that we need to use bias ply tires, because radials aren't supported!!!!

I may need to revert to a flooded cell battery -- which I really don't want to do!! AGM batteries are so much better in many regards. For whatever reason, I still can't find any website that lists a battery replacement for a 2025 (or 2024) Land Cruiser...

 

[SlickLC]

So far, my experience with an AGM battery (an Optima Yellowtop DH6) has been that the car does not seem to be able to keep it fully charged. I CAN fully charge it with my Noco wall plug-in charger, but in the days after doing so it fairly quickly loses SOC, even tho I drive every day. This is presumably due to the fact that the 14.4V put out by the hybrid system is not quite enough to keep the AGM topped up.

A good example is that day before yesterday I fully charged the battery (using my Noco charger set to AGM). Then, yesterday I drove down to the Toyota dealership, a little over a half hour. During my vehicle service, they had the doors and liftgate open, etc., as expected. The tech tested the battery -- and although it tested at 100% health, it was only 85% charged. So as I see it, either:
- The battery is defective and cannot hold a charge, or
- The car should have been able to keep the battery topped off on the drive to the dealership, but was unable to do so (I assume because it was only putting out 14.4V).

Since the battery is new and tests at 100% health (measured by both my tester and the dealership's tester), I assume that the battery is not defective and the issue is the low voltage 12V battery charging by the hybrid system.

Interestingly, there is a recent post (attached) on another forum about a guy that changed from a flooded cell to an AGM with his 4Runner. This substantiates what I wrote above...

Yesterday, I asked my tech at the dealership about the possibility of a configuration setting for the car which would change the charging profile to AGM -- and unfortunately, there isn't such a setting. Hard for me to believe that Toyota doesn't provide support for AGM batteries -- kind of like telling us that we need to use bias ply tires, because radials aren't supported!!!!

I may need to revert to a flooded cell battery -- which I really don't want to do!! AGM batteries are so much better in many regards. For whatever reason, I still can't find any website that lists a battery replacement for a 2025 (or 2024) Land Cruiser...

this brings me back to my 2017 4runner days - in order to use an agm battery i had to replace the 7.5 amp alt-s fuse in the engine bay fuse box with a voltage booster diode from voltageboosterpro.com

 

[Mikie]

LOL -- they guy in the forum post I mentioned also had a '17 4Runner, that he boosted the recharging voltage in order to effectively charge an AGM battery.

Unfortunately the voltage booster you mentioned does not support the Land Cruiser.

 

[Mikie]

I forgot to add -- if you go with an AGM on your LC, and you don't regularly (weekly?) do a full battery recharge with an external charger, then because your LC won't keep your battery fully charged when driving, you will have a consistently undercharged battery... And this will significantly reduce the life of your AGM battery.

 

[ultane]

The USA LC250 seems to charge at a 14.4v consistently when operating.

How do you know this (14.4v) to be true?

 

[Mikie]

See post #40 above, but more directly, I've installed a Bluetooth battery monitor that allows me to keep tabs on battery status via my cell phone. In addition to instantaneous results, it also provides a running hourly or daily log of battery voltage.

Ancel BM300 Battery Monitor

 

[SlickLC]

I forgot to add -- if you go with an AGM on your LC, and you don't regularly (weekly?) do a full battery recharge with an external charger, then because your LC won't keep your battery fully charged when driving, you will have a consistently undercharged battery... And this will significantly reduce the life of your AGM battery.

ive had to clear up many sla vs agm pros and cons with people who deep cycle without knowing what damage they can do to batteries. and those who switch to agm, why they need a higher charging voltage. a lot of it has to do with people who run car dash cams 24/7.

 

[ultane]

See post #40 above, but more directly, I've installed a Bluetooth battery monitor that allows me to keep tabs on battery status via my cell phone. In addition to instantaneous results, it also provides a running hourly or daily log of battery voltage.

Ancel BM300 Battery Monitor

Thank you! This answers, proves my question and concern from long ago in this forum, after years of reading about batteries and AGM’s in particular, on another forum (ADVrider.com) for motorcycles… though it is a better technology, an AGM in our LC’s is a no go..

I wish Toyota and other manufacturers would get up to speed.

 

[Mikie]

Thank you! This answers, proves my question and concern from long ago in this forum, after years of reading about batteries and AGM’s in particular, on another forum (ADVrider.com) for motorcycles… though it is a better technology, an AGM in our LC’s is a no go..

I wish Toyota and other manufacturers would get up to speed.

SOME manufacturers do handle this problem directly -- e.g. I've watched a video of a guy upgrading his flooded cell battery with an AGM (I think this was for a VW) -- and part of the process was to hook up his Carista and change the battery charging profile to AGM (this was all done in the video). I'm pretty surprised that with such a new car as the LC, Toyota doesn't support this.

BTW, a while back I did look at the doc for Carista and OBD1 (for the Land Cruiser), and didn't find anything for changing the battery charging profile.

 

[D-mac]

Thank you! This answers, proves my question and concern from long ago in this forum, after years of reading about batteries and AGM’s in particular, on another forum (ADVrider.com) for motorcycles… though it is a better technology, an AGM in our LC’s is a no go..

I wish Toyota and other manufacturers would get up to speed.

Optima specifies an alternator voltage range of 13.65V to 15V. Odyssey specs 14.1 to 14.7V. The LC250's OEM alternator output range appears to be within the AGM battery manufacturer's specs. Both battery manufacturers have a safe charge voltage limit of 15V. They note full charging is only needed if the battery voltage output goes below about 12V.

 

[Homers Kid]

How do you know this (14.4v) to be true?

Please see post 49 and 51 in this thread. I used the Antigravity Battery tracker to monitor the charging when the Landcruiser is running and in motion. Resting voltage of a lead acid battery is roughly high 12v's where as resting voltage of Lithium is 13.3-13.4v resting voltage. So when you see a voltage of 14.4v on tracker during the vehicle on, in motion it is charging the battery at 14.4v.

 

[Mikie]

A few more data points...

• Note that Optima specifically recommends that you do not let your battery drop below 12.4 volts, otherwise it is subject to sulfation.
• Today I sat in the car with the engine running and watched the voltage while charging -- and although it started out at 14.4, over the course of several minutes it slowly dropped a bit to just under 14.3 (i.e. it floated between 14.27-14.28). It didn't seem to keep dropping after that, but I didn't watch it for a super long time. I hadn't noted this drop before (but I've never looked for it).
• A couple people have mentioned VoltageBoosterPro, having used it in their earlier generation 4Runners. They don't make one for Land Cruisers (nor the new 4Runners), but this is some (marketing) info from their website:

Absorbent Glass Mat (AGM) batteries including Optima, Odyssey, Duracell Platinum, AC Delco Gold/AGM, Northstar, and XS Power, typically require a slightly higher charging voltage compared to flooded lead-acid batteries. AGM batteries have a different internal construction and electrolyte containment method compared to traditional flooded lead-acid batteries.​

​

Flooded lead-acid batteries have free-flowing electrolyte, while AGM batteries use a fiberglass mat to hold the electrolyte in place. This design difference impacts the charging process. AGM batteries are generally more sensitive to voltage fluctuations and can be damaged if not charged properly.​

​

AGM batteries usually require a charging voltage of around 14.4 to 14.7 volts for a 12-volt battery, which is slightly higher than the 14.2 to 14.4 volts typically used for flooded lead-acid batteries. It’s important to follow the manufacturer’s recommendations for charging voltage to ensure the longevity and performance of the battery.​

Although I really can't verify that 14.4-14.7V is in fact needed for charging AGMs, it does appear that the Land Cruiser's charging voltage is aimed squarely at non-AGM flooded cell batteries...

 

[D-mac]

It’s important to follow the manufacturer’s recommendations for charging voltage to ensure the longevity and performance of the battery.​

From the data available, it appears from the data listed that these Toyota's OEM LC250 alternators meet popular AGM battery manufacturers' recommended ranges for safe charging voltage and there is no need to 'boost' an LC250's output above 15V.

 

[Mikie]

From the data available, it appears from the data listed that these Toyota's OEM LC250 alternators meet popular AGM battery manufacturers' recommended ranges for safe charging voltage and there is no need to 'boost' an LC250's output above 15V.

I agree, you definitely don't want to go above 15V -- but I am wondering if you want to get it up to something like 14.5 or 14.6 or so to fully charge an AGM battery. This is what I've read in many places on the net (and you know, there is no bad info there!)

Per what you wrote, the allowable range for charging is as low as 13.65V for Optima or 14.1V for Odyssey, but I wonder if the batteries will fully charge at those low levels. I'm guessing not, but I have an email into Optima, and we'll see what they say.

 

[LCP250]

Do you guys mean the inverter? my understanding is the LC250 doesn't have an alternator. sounds like the LX700 does.

Any way to add an alterantor?

 

[Mikie]

I could be wrong, but I believe that the inverter converts DC to AC (so that the DC traction battery power can be used to drive the AC motor), and the DC-DC converter changes DC voltage (so the high DC voltage in the traction battery can be used to charge the low voltage 12V battery, and run all of the 12V electronics while the hybrid system is on).

You are correct, there is no alternator in the LC (the electric motor is used to serve this function).

 

[AlexGates]

Do you guys mean the inverter? my understanding is the LC250 doesn't have an alternator. sounds like the LX700 does.

Any way to add an alterantor?

By my recollection, the only two hybrids that have an alternator and starter are the 700h and the 4Runner (if you get the aux switches.) Both will start and run if the hybrid system fails.

 

[Mikie]

Although I'm not sure about this, I think that there is in fact a back-up starter in the LC... I have found such a part for it online, such as this: Land Cruiser starter

This is an interesting topic that I've wondered about: What happens if the traction battery sits and drains such that it no longer has enough juice to start the engine?? I THINK (but am not sure) that in this case, you can start the car using the back-up starter and the 12V battery. This is all surmising on my part, but I think it may be right -- if not anyone, please correct me, as I'd love to know how this works!!

I seem to remember reading in the owner's manual that if the traction battery sits for several months, the charge may decline and thus the hybrid system will not be able to start the engine. In this case, I think the fix was to call the dealer, but I don't remember for sure (I've looked, but I can't seem to find this reference). I wonder if the dealer would instruct you to start the engine with the backup starter, but I've no idea how you would accomplish this...

 

[D-mac]

I agree, you definitely don't want to go above 15V -- but I am wondering if you want to get it up to something like 14.5 or 14.6 or so to fully charge an AGM battery. This is what I've read in many places on the net (and you know, there is no bad info there!)

I'm not an electrical engineer, but suspect that the AGM battery manufacturers specify a range of acceptable charging voltages instead of a single value to provide a margin of safety for different operating loads on the electrical system and temperatures. I doubt the aftermarket 'voltage booster' devices could accurately for these variables, but clearly the manufacturer(s) of the devices want you to believe they can.
AGM batteries are not a new technology. I've been using them on all of my cars over the last 25+ years and never had to replace one that I have installed. I do remember the days of adding electrolyte to maintain batteries, but am glad those are just memories.
I've had another hybrid that I have stored for months and plugged the 12V battery into a 1-2 amp trickle charger (like many car collectors do), and there were no issues. I plan to do the same with my LC250 if needed.