Should I replace my 2008 4Runner alternator to enable fast Li battery charging?

[zack sc]

Should I replace the alternator in my 2008 Toyota forerunner.

I recently installed a Victron Orion dc-dc charger (XS-50) that draws power from the alternator of my 2008 4Runner and uses that to charge an LiFePO4 auxiliary battery at about 20 amps while I drive. This post is an inquiry about the impact of that additional power draw on the 4Runner alternator and the possibility of charging at a higher rate: can the alternator handle that?

Here is some possibly relevant information:
With the Victron app on my phone I can see the voltage that the alternator is putting out. Here’s what I typically observe.
When I start the forerunner the voltage is typically 14.1 V. Over the next 15 minutes it typically drops to 13.6 V and then gradually decreases to about 13.2 V and tends to stay in that range. Is that cause for concern? Are those voltages too low? Do they possibly indicate some sort of issue with the alternator? This sequence of voltages seems to happen about the same regardless of whether I’m charging at 10 A or 24 A. (So far I’ve been afraid to go higher than 24 A, however for the 165 Ah battery I am charging, a charging rate of 40 or 50 A would not be unreasonable if the alternator could handle that. Essentially, it is concern about the alternator that holds me back from trying to charge at a higher current level.

Some people have suggested that I should get a more powerful alternator. Others have said that you should stick with the OEM alternator. And that if the alternator‘s been working a long time, that’s a really good sign. My 2008 forerunner has 250,000 miles on it. I’ve owned it since 2013. I believe it’s the original alternator. Over the entire time I’ve had the car, the alternator has seemed to work perfectly in the sense that my interstate starter batteries last really well and never fail me. So the alternator has always worked really well and has never boiled a battery, which I might be slightly concerned about with a new more powerful alternator. Also, it has also never left the battery under charged. It’s been perfect. On the other hand it’s 16 years old and 250,000 miles old.

So I’m hoping to get some advice from some experts about whether it’s more prudent to keep the old alternator that has worked well for so long, or whether replacing an alternator proactively is a reasonable preventative maintenance and would enable faster charging, for example, at 40 amps. I camp in remote areas. Alternator failure would be a real problem for me. so I’m kind of torn between the mindset of if it ain’t broke don’t fix it, or the thought that my alternator is really old and maybe I should get a new one and then I could charge more rapidly with peace of mind. So I would be most interested and appreciative to learn what people who are experts on or have experience with alternators think I should do.

[Lynn Eberhardt]

The voltages you posted indicate that the alternator is working exactly as it should. It starts at 14.1 to replace the power you used to start plus any self discharge losses, then gradually goes back to 13.2 to supply ongoing electrical needs. If it still does that or runs slightly higher while running the Victron charger, no worries. Check voltages at the vehicle battery. Your alternator may someday die of old age, but that is not what you're seeing now.

[ShelbyM]

^^^That sounds right and you often don't know what you are getting with a replacement part. At 250,000 miles every part is past its reasonable lifetime so replacement just in case could be a slippery slope.

[Mike Magee]

I don't know much about alternators, but based on the previous comments I would say that an alternator will never be able to charge your LiFePO4 to full capacity. Probably 70% is realistic. You will want to top off the battery occasionally with a proper charger so the cells equalize.

[Lynn Eberhardt]

See post 1.
"I recently installed a Victron Orion dc-dc charger (XS-50)"

[CharlesinGA]

DC-DC charger will be the way to go, it can buck/boost the voltage to what the batteries need, no matter (within limits) what the incoming voltage is. It keeps you from overloading the alternator as it is a finite max draw on your tow vehicle that is reasonable.

Charles

[Sunnyfalls]

We took a different approach. We don't allow our TV to power our trailer systems or charge our trailer 100AH LiFePO4 battery at all. We use propane to run our absorption refrigerator when traveling. As such, we never see more than a couple percent of battery depletion after a day of traveling. Our 200 Watt solar panel suitcase can replenish our typical 30-40% overnight depletion in less than 4 hours. And of course, Shore Power or our propane modified Honda EU2200i generator can replenish this in less than an hour. We hardly take our generator as it is only needed for air conditioning which is hardly ever needed given where we camp and our awning system that fully shades our trailer driver and passenger sides.

Gayle & Bob
"Los Gatos Casita"

[StevenMaria]

Does your lithium battery have built in circuitry which controls the charging rate and shut off or does that charger you specified have setting for lithium batteries. I’m not fluent in their designs but I have read that charging is one of the fire safety areas to be concerned about with Li batteries.

I ask this as a neighbor nearly burnt his house down because of a charging leaf blower that blew up in his garage and started a bad fire.

[Sunnyfalls]

Originally Posted by StevenMaria

Does your lithium battery have built in circuitry which controls the charging rate and shut off or does that charger you specified have setting for lithium batteries. I’m not fluent in their designs but I have read that charging is one of the fire safety areas to be concerned about with Li batteries.

I ask this as a neighbor nearly burnt his house down because of a charging leaf blower that blew up in his garage and started a bad fire.

Yep...the reason we first minimized our AH requirements and why we typically only operate within 30-80% capacity with some occasional 100% charges to fully cycle and maximize battery life. LiFePO4 batteries are relatively safe, but not so safe that the FAA allows them to go into the cargo hold of airplanes. I think some people don't appreciate how much energy is in these batteries and how difficult it can be to extinguish their fires.

Gayle & Bob
"Los Gatos Casita"

[John in Santa Cruz]

I tried to sue an Orion Tr 12/18 on my Escape when i was pulling it with an F250 and I'd put 412AH of LFP batts in the back of the Escape. There was just too much voltage drop in the wiring from the truck. I had 14.x V under the hood, and was only seeing like 10-ish V at the Orion's input. To output 18A at 13.6-ish V to charge the lithiums requires about 25A at 10V which is why the voltage was dropping so low. Combination of the factory wiring in a 21 foot long truck (F250 w/ 8 foot bed and cab-and-a-half), plus another 21 or so feet of wiring in the trailer from the hitch to my power stuff in the very back. I ended up shutting the Orion off, and rely almost entirely on my 360W solar panel, which does very nicely keeping things happy.

[barrry smithe]

Running propane equipment while driving is a disaster waiting to happen. Gas leak, spark and boom end of camping excursion.

[Jann Todd]

Originally Posted by barrry smithe

Running propane equipment while driving is a disaster waiting to happen. Gas leak, spark and boom end of camping excursion.

Using propane while driving is no problem as long as you turn off the appliance before pulling up to gas pumps to fuel up. I've seen several RV fires and none caused by running the fridge on propane as long as you don't have it on at a gas station pump. If a propane leak happens and it is bad then the tank shuts off. This is the newer parts on a tank. It is no more dangerous than using the propane appliances in the campground. Electrical fires are much more common than propane fires in RV's.

[Jon in AZ]

Since this thread is about charging lithium coach batteries while towing, it might be best to stay on topic. In any case, we know nothing about the OP's trailer configuration.

There are lots of old discussions about the pros and cons of running propane appliances while towing. Here's one if anyone feels compelled to address the issue...
https://www.fiberglassrv.com/forums/...ane-44457.html

[zack sc]

My Scamp configuration is completely unaltered with an excellent interstate RV battery in the group 27 box on the front behind the propane. I run a Dometic DZ65 fridge in the 4Runner TV using a Jackery 1000 in the TV. That's where my LiFePO4 battery is. The LiFePO4 battery (LiTime 165 Ah) is right behind the driver's seat, so there is just 5 or 6 feet of 4 AWG wire from the alternator to the 12-12 50 d.c. converter. No voltage drop to speak of charging at 20 amps (280 Watts). Works great for me and I can use the Jackery to top up the RV battery when I am not driving if needed. I think the LiTme (and many other brands) are safe especially when properly charged e.g. with Victron Orion dc-dc converters. I have a lot of energy now and no conversion or voltage-drop issues because the Lithium battery is so close to the TV alternator. The LiFePO4 battery charges whenever I drive (along with the TV starter battery and the RV battery. I also often draw 6 more amps to charge the Jackery 1000 from a cigarette lighter port while driving (so 26 amps plus TV battery and RV battery.) Occasionally I idle just to charge, but I am nervous about that. I can basically see all relevant voltages any time on my phone. I installed a smart shunt recently, though I haven't really figured out how to calibrate that yet. (Do I have to charge to 100% to do that?) I am nervous about the alternator though, especially since all this is new.

[Jeep Man]

No way. Just get a DC-DC charger from Victron or another brand so you don't over charge your battery. Your Toyota alternator puts out way over 20 amps when at higher than idle RPM when driving. At least double that. So 2 hr driving will charge up 100 amps no problem. I'd really advise avoiding charging off your alternator but if you have to this is the way to go.

[ShelbyM]

Originally Posted by Jeep Man

No way. Just get a DC-DC charger from Victron or another brand so you don't over charge your battery. Your Toyota alternator puts out way over 20 amps when at higher than idle RPM when driving. At least double that. So 2 hr driving will charge up 100 amps no problem. I'd really advise avoiding charging off your alternator but if you have to this is the way to go.

Good to know....

[CarlD]

I have a victron 12/12-9 DC to DC isolator that runs off the TV to charge my LFP battery. I ran a 12 ga wire with fuse from the distribution panel under the hood to a dedicated connector at the back of the truck and installed a relay that's triggered from the OEM power wire at the 7 pin connector to break the circuit when the TV is not running. I have 110,000 miles on the trailer. The only issue I had was one of the terminals on the victrom burned up from a loose connection (my bad). It sounds like to OP has good wiring and shouldn't have a problem. The alternator should handle the load fine, but not knowing the alternator power output curve vs RPM, I wouldn't idle for long periods of time unless you reduce the charging current.