Stock electrical system excess capacity?
- Thread starter scfw0x0f
- Start date
rigtec
New member
Hey [MENTION=144561]DCPower_Anthony[/MENTION] ...,
Just a thought: ...what if one of us with an ...After 2017 OEM 4Runner (SR5, Trail, Limited, TRD...etc, sent you a "Core/Dead alternator's End-frame Still assembled" that's being replaced; "...someone already has one from a 2018 or later(?)!" Couldn't you get your "EXACT MEASUREMENTS" from that, and cast a set-of End-frames from those architectural structured design measurements for an Up-dated 270-XP?
No one would need ta lose a daily-driver, or time Trailing, or Mall-Crawling...(?)!
~rig~ Just-a-thought...! Best to you!
Last edited:
lewdog998
New member
I am no where near DCPower shop....so that would not be an option. I can do most mech work short of rebuilding a transmission.
DCPower_Anthony
New member
I can get cores, that's not the issue. It's whatever is around the alternator has changed. The factory alternator is much smaller than the 270XP which means it was unaffected by the change.
DCPower_Anthony
New member
Send me a private message and will get this going.
lewdog998
New member
4RExplorer
New member
I'd like to see DC Power offer a high-output alternator for 2018+ 4Runners, but in the meantime, I implemented a different solution for charging my auxiliary battery bank from the OEM alternator using a DC-DC charger, without having to worry about the alternator overheating: install a temperature sensor on the alternator housing and measure high temps on a hot day. Mine hit 175 degrees F, and that wasn't even on the hottest day, but from that I know that the OEM alternator can withstand at least 175 degrees F.
Then I installed an ignition-switched On/Off switch on the dashboard to send power to a relay that powers the DC-DC charger only when the vehicle is running and the switch is turned on. So I can use the On/Off switch to manually start the charging when the temperature sensor display (which I also installed on the dashboard) shows that the alternator is fairly cool, and manually stop the charging when I see the alternator getting too hot, i.e. approaching 175 degrees. This way I can prevent the alternator from overheating because of the added load of charging the auxiliary batteries. This kept my battery bank topped up on a recent long road trip.
Then I installed an ignition-switched On/Off switch on the dashboard to send power to a relay that powers the DC-DC charger only when the vehicle is running and the switch is turned on. So I can use the On/Off switch to manually start the charging when the temperature sensor display (which I also installed on the dashboard) shows that the alternator is fairly cool, and manually stop the charging when I see the alternator getting too hot, i.e. approaching 175 degrees. This way I can prevent the alternator from overheating because of the added load of charging the auxiliary batteries. This kept my battery bank topped up on a recent long road trip.
This is a great solution and very similar to what I plan to do; although I was going to trust the "Ignition On" feature in the Victron charger to detect that the battery is on. My bank size is targeted at 3kWh (125Ah @ 24V nominal), and they can take up to 25A when charging (really, a lot more but 0.2C is optimal), so that's 725W at the batteries (25A @ 29V final bulk charge) before DC-DC efficiency is factored in (Victron isn't great, about 88%!), so that's about 58A at the alternator, assuming 14V.
I was trying to estimate the available power from the alternator (headroom). The best I could come up with is the fact that the built-in inverter is good for 400W when parked (engine running), but only 100W when driving. 100W would take a long time to recharge my bank, but maybe I could use the shore power charger @ 100W in to give some power to the batteries until a new alternator solution is available.
You could set up a simple window comparator circuit, trip and reset points at maybe 175F and 150F, and maybe an additional 3 minute lockout after tripping (so 3 mins min and <150F to reconnect) to automate your operation.
I'd never connect lithium batteries (these are LiFePO4) directly to a vehicle alternator; that way lay madness
4RExplorer
New member
This is a great solution and very similar to what I plan to do; although I was going to trust the "Ignition On" feature in the Victron charger to detect that the battery is on. My bank size is targeted at 3kWh (125Ah @ 24V nominal), and they can take up to 25A when charging (really, a lot more but 0.2C is optimal), so that's 725W at the batteries (25A @ 29V final bulk charge) before DC-DC efficiency is factored in (Victron isn't great, about 88%!), so that's about 58A at the alternator, assuming 14V.
I was trying to estimate the available power from the alternator (headroom). The best I could come up with is the fact that the built-in inverter is good for 400W when parked (engine running), but only 100W when driving. 100W would take a long time to recharge my bank, but maybe I could use the shore power charger @ 100W in to give some power to the batteries until a new alternator solution is available.
You could set up a simple window comparator circuit, trip and reset points at maybe 175F and 150F, and maybe an additional 3 minute lockout after tripping (so 3 mins min and <150F to reconnect) to automate your operation.
I'd never connect lithium batteries (these are LiFePO4) directly to a vehicle alternator; that way lay madness
My battery bank is smaller (two 92Ah LiFePO4 batteries in parallel at 12V), but the manufacturer's recommended maximum charge current at cool temperatures is 46A, so I have a RedArc BCDC1240D, which charges at 40A continuous. RedArc recommends a 60A fuse at the starter battery, so the draw on the alternator is probably not too far from your 58A setup. I was able to charge while driving at highway speeds for long periods of time with no problem, so that suggests that the OEM alternator would be able to handle the 58A draw from your Victron charger. But to be safe, I was charging only when I did not have the heater or other high-amp loads running. I haven't tested it with multiple high-amp OEM loads running simultaneously. But even with only intermittent charging, 40A bulk charging is enough to keep my batteries charged, given my typical electrical usage and time spent driving each day.
That all sounds great but I'd rather have an over-spec alternator than have to monitor alternator temperatures personally, or chance losing charging capacity due to an overload. A 60A fuse only means that the wiring is expected to handle more than 60A, and the load is expected to draw less; it doesn't really indicate actual load. I would expect 40A out, same voltage in and out, would draw 42A to 44A for a reasonably efficient regulator.
I think the inverter power being derated by Toyota from 400W (in park) to 100W (in drive) is indicative of how much (or little) power is available from the alternator. I agree, in a lot of cases the stock alternator is probably fine for this application. I'm still going to hold out for the DC Power alternator, just because I want the extra capacity, and may add more loads later.
Thanks for sharing your solution. It sounds very useful for a lot of users.
I think the inverter power being derated by Toyota from 400W (in park) to 100W (in drive) is indicative of how much (or little) power is available from the alternator. I agree, in a lot of cases the stock alternator is probably fine for this application. I'm still going to hold out for the DC Power alternator, just because I want the extra capacity, and may add more loads later.
Thanks for sharing your solution. It sounds very useful for a lot of users.
2021nightshade4x4
New member
I think I dropped in on this thread after you already made your decision, but I had a question for my own learning.
You say “rather have an over spec alternator than have to monitor alternator temperatures”.
Would the heat build in the alternator (vs the wires, if the wires were not insufficient) in the case that the charging rate of your system exceeded the available current of the stock alternator? Would there just be a voltage drop? Both?
If there are options for multiple alternators on the 4Runner, I’ve toyed with the idea of having one be a 24V alternator (seen some up to 150A) to charge accessory batteries more efficiently.
Sent from my iPhone using Tapatalk
Interesting questions and options!
24V alternator: I'd be interested in this, but given the problems fitting a new higher-capacity alternator, I suspect adding a second alternator would be crazy hard. I don't want to add a 24V-12V DC/DC for the rest of the electronics, change to a 24V starter, etc. This could be a great option at home, on a boat, or in a larger vehicle.
The available current from the stock alternator, after subtracting loads for the stock devices, is an open question. I regard the information that Toyota restricts the load on the stock inverter to 100W when driving, but allows 400W when in park, to indicate that the available current may be pretty low (100W) in some cases. Toyota almost certainly built in margin on that, but I suspect it's not more than 100%, so 200W max when driving. Several things could happen:
* The voltage from the alternator could drop so low that the starter battery might start to supply current, which would be Bad (draining the starter battery).
* The big 140A fuse that protects the alternator and its wiring could open. Replacing it is a PITA.
* The alternator could overheat if not monitored (hot day, slow speed, high load).
In general, running electronics below their ratings (usually power, but also temps, and depth of discharge and peak charge level for some batteries) prolongs the life of the electronics. Electromechanical devices like alternators also generally benefit from lower loading. A nominal 270 amp alternator that can maintain that output at a certain ambient temperature, should be a lot cooler and last longer than a 130 amp alternator for the same output, all other factors being equal (no fair comparing an oil-cooled device against an air-cooled one, for example).
[MENTION=294318]4RExplorer[/MENTION] 's approach is perfectly valid in a "let's see what works" approach to the problem. But as he's said, he's be careful about what he runs when charging; I'd rather not have to track alternator temps, or chance losing charging capacity even with an automatic system to watch the alternator temperatures and output current.
Does that help or did I go sideways on your question?
24V alternator: I'd be interested in this, but given the problems fitting a new higher-capacity alternator, I suspect adding a second alternator would be crazy hard. I don't want to add a 24V-12V DC/DC for the rest of the electronics, change to a 24V starter, etc. This could be a great option at home, on a boat, or in a larger vehicle.
The available current from the stock alternator, after subtracting loads for the stock devices, is an open question. I regard the information that Toyota restricts the load on the stock inverter to 100W when driving, but allows 400W when in park, to indicate that the available current may be pretty low (100W) in some cases. Toyota almost certainly built in margin on that, but I suspect it's not more than 100%, so 200W max when driving. Several things could happen:
* The voltage from the alternator could drop so low that the starter battery might start to supply current, which would be Bad (draining the starter battery).
* The big 140A fuse that protects the alternator and its wiring could open. Replacing it is a PITA.
* The alternator could overheat if not monitored (hot day, slow speed, high load).
In general, running electronics below their ratings (usually power, but also temps, and depth of discharge and peak charge level for some batteries) prolongs the life of the electronics. Electromechanical devices like alternators also generally benefit from lower loading. A nominal 270 amp alternator that can maintain that output at a certain ambient temperature, should be a lot cooler and last longer than a 130 amp alternator for the same output, all other factors being equal (no fair comparing an oil-cooled device against an air-cooled one, for example).
[MENTION=294318]4RExplorer[/MENTION] 's approach is perfectly valid in a "let's see what works" approach to the problem. But as he's said, he's be careful about what he runs when charging; I'd rather not have to track alternator temps, or chance losing charging capacity even with an automatic system to watch the alternator temperatures and output current.
Does that help or did I go sideways on your question?
lewdog998
New member
[MENTION=294318]4RExplorer[/MENTION]
[MENTION=710497]scfw0x0f[/MENTION]
[MENTION=659386]2021nightshade4x4[/MENTION]
Not sure if you missed it earlier in this thread..but I did just install the DC power alternator....and it works great.
Here is the install thread
High Power Alternator install
[MENTION=710497]scfw0x0f[/MENTION]
[MENTION=659386]2021nightshade4x4[/MENTION]
Not sure if you missed it earlier in this thread..but I did just install the DC power alternator....and it works great.
Here is the install thread
High Power Alternator install
Yes, and thanks for breaking that trail! I’m holding off until [MENTION=144561]DCPower_Anthony[/MENTION] issues official instructions; my mechanic is more likely to be willing to work from those than from a post here. I do electrics, mostly, and leave the really funky wrenching to others.
