Dual Battery Questions

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kfmarshall

kfmarshall

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I realize there are several threads out there currently but most are a decade old. I'm not sure the protocol for refreshing a conversation, but hopefully my noob status will afford me some leniency.

Here is the series of events: My lights started to dim at night a few weeks ago and I assumed that meant my alternator was going or I have some sort of electrical issue (battery is new). As I looked around online I saw there are more powerful alternators available, but really what I needed was more storage (I realize this is all dependent upon the accessories drawing power, but I'm planning on adding a winch and more lights so I think it applies). I then stumbled across the dual-battery threads with a lot of suggestions, components, vendors, and advice but all are fairly dated and I wasn't able to draw a conclusion. So, here is what I've garnered thus far:
  • A dual battery setup should have a starter battery and an accessory battery. The first for engine starting power, the second for longer term power for accessories.
  • Back in the day, Optima Red and Yellow top batteries were the answer, but they appear to have lost the confidence of the community
  • Regardless of battery choice, I'll need a tray and a dual-battery system like the IBS (Intelligent Battery System) that has components that tie the batteries to the alternator, and their respective power drawing components
  • A savvy mechanic can build their own system with easily available parts (probably not me)
  • Apparently there is room for a dual setup if there hasn't been a V8 upgrade (My 2F is still in place)
So, before I hang a bunch of accessories on my rig I figure I need to get this sorted. Is there now, in 2021, a community consensus on the best approach?
  • Which battery combo is best?
  • Which system is best?
  • Should I upgrade my alternator anyway?
I recognize there is probably a wide dollar range here but I'm shooting for best solution so for the time being I'm not going to sweat cost.

Thanks in advance,

Kevin
 
FJ40 that green thing

FJ40 that green thing

1996 KZJ78 Prado
Joined
Jul 8, 2004
Messages
198
Location
Wyoming
You used to be able to buy a kit for the JF40 I believe from Specter and ManaFre but I couldn't find anything when I was ready to add dual batteries on the 45. With a winch, I don't see how you could get by with only 1 battery, I was surprised I was the only one seemingly looking for a solution. This is what I came up with.

Dual battery tray here: Amazon product

This is designed to fit Optima batteries but like you, I wasn't sure I could pay $200 ea with their reputation so I was actually able to get a couple Interstate Lead Acid batteries to fit in there and I have been happy with them so far. I hear Odyssey brand batteries are real nice AGM and worth the money but they are expensive! I removed the factory battery tray but kept the base mount in place, positioned this dual battery bracket in there at just the right angle and ran some new holes into the bottom of it so the bolts would thread into the factory base mount. This bracket is strong and works great.

I needed quite a bit bigger alternator since I'm running fridge, on board air, multiple accessory lights, etc. so I went with the Vintage Air alternator/ A/C bracket and a GM 1 wire 200 amp alternator. I went ahead and installed the AC compressor so all the belts and accessories worked properly. I bypassed the factory harness and built a power distribution box with relays for the individual components, you could really design this however you want, thats just how I chose to do it.

Vintage Air FJ40 Alternator bracket: Vintage Air 158209 68-83 FJ40 Land Cruiser Compressor/Alt Bracket - https://www.speedwaymotors.com/Vintage-Air-158209-68-83-FJ40-Land-Cruiser-Compressor-Alt-Bracket,442231.html?sku=721158209&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQiA-K2MBhC-ARIsAMtLKRsYMELObjcgYBQ6yysZBsP9wIfFyanBNrTWUu1UrTeqIpbkJIz3bKUaAkAVEALw_wcB

I chose not to isolate 1 battery from the other because I would rarely have to worry about running both batteries down and I kept hearing keep it simple is better which I believe is best as well with anything electrical but you certainly could go with a more sophisticated charging system. Redarc and others have some nice off the shelf products. I simply wired my batteries parallel which keeps the voltage the same but doubles the Ah.

This is the best solution I could find for dual battery and high amp alternator, I hope that helps, there really isn't anything out there that is plug and play anymore for the 40, you basically have to figure it out on your own.
 
Last edited:
FJ40 that green thing

FJ40 that green thing

1996 KZJ78 Prado
Joined
Jul 8, 2004
Messages
198
Location
Wyoming
Oh, one last thing. One of the best things you can do for brighter headlights on an old FJ40 is to get a Hella H4 headlight relay harness. The factory harness and connectors get old and corroded and the wires are just not that thick of guage to begin with.


Very simple install, might take you 10 minutes. You just hook up power to battery and ground, then plug your factory harness into the connectors and the new connectors into your headlights. Everything will operate as it did before but you have a much beefier guage wire running straight from battery to your lights and allows you to run brighter bulbs too. You may be able to do this and just keep your standard 1 battery and stock alternator if that is the only problem you are trying to solve.
 
Last edited:
EWheeler

EWheeler

4 Cruisers, No Garage !
GOLD Star
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Messages
1,747
Location
Menifee, CA
I realize there are several threads out there currently but most are a decade old. I'm not sure the protocol for refreshing a conversation, but hopefully my noob status will afford me some leniency.

Here is the series of events: My lights started to dim at night a few weeks ago and I assumed that meant my alternator was going or I have some sort of electrical issue (battery is new). As I looked around online I saw there are more powerful alternators available, but really what I needed was more storage (I realize this is all dependent upon the accessories drawing power, but I'm planning on adding a winch and more lights so I think it applies). I then stumbled across the dual-battery threads with a lot of suggestions, components, vendors, and advice but all are fairly dated and I wasn't able to draw a conclusion. So, here is what I've garnered thus far:
  • A dual battery setup should have a starter battery and an accessory battery. The first for engine starting power, the second for longer term power for accessories.
  • Back in the day, Optima Red and Yellow top batteries were the answer, but they appear to have lost the confidence of the community
  • Regardless of battery choice, I'll need a tray and a dual-battery system like the IBS (Intelligent Battery System) that has components that tie the batteries to the alternator, and their respective power drawing components
  • A savvy mechanic can build their own system with easily available parts (probably not me)
  • Apparently there is room for a dual setup if there hasn't been a V8 upgrade (My 2F is still in place)
So, before I hang a bunch of accessories on my rig I figure I need to get this sorted. Is there now, in 2021, a community consensus on the best approach?
  • Which battery combo is best?
  • Which system is best?
  • Should I upgrade my alternator anyway?
I recognize there is probably a wide dollar range here but I'm shooting for best solution so for the time being I'm not going to sweat cost.

Thanks in advance,

Kevin
Honestly, unless you're overlanding (like real overlanding, not just outfitting your truck to look like you overland) and doing self-sustained long trips away from civilization, I just don't see the actual NEED for dual batteries. I get that many people want them, but you gotta sort out if you truly want or need it, and then determine what your budget can with stand.

Your symptoms of dimming lights while driving is likely a result of a bad or failing alternator, or an issue in the wiring of the charge circuit, not an issue of reserve capacity in your battery. I would start there FIRST. You state the battery is new, so I don't see the need to spend money on TWO batteries to replace one good one.

What are your intended uses for the truck?
 
EWheeler

EWheeler

4 Cruisers, No Garage !
GOLD Star
Joined
Apr 5, 2008
Messages
1,747
Location
Menifee, CA
Oh, one last thing. One of the best things you can do for brighter headlights on an old FJ40 is to get a Hella H4 headlight relay harness. The factory harness and connectors get old and corroded and the wires are just not that thick of guage to begin with.

Amazon product

Very simple install, might take you 10 minutes. You just hook up power to battery and ground, then plug your factory harness into the connectors and the new connectors into your headlights. Everything will operate as it did before but you have a much beefier guage wire running straight from battery to your lights and allows you to run brighter bulbs too. You may be able to do this and just keep your standard 1 battery and stock alternator if that is the only problem you are trying to solve.

Better yet is a TOYOTA OEM upgraded harness WITH lights, for the same price.

Here is a visual:

Here is where to get it for $40:


Granted, you gotta spend $75 for free shipping and use code FREESHIP at checkout.
 
kfmarshall

kfmarshall

Joined
May 17, 2021
Messages
16
Location
Oakton Virginia
You used to be able to buy a kit for the JF40 I believe from Specter and ManaFre but I couldn't find anything when I was ready to add dual batteries on the 45. With a winch, I don't see how you could get by with only 1 battery, I was surprised I was the only one seemingly looking for a solution. This is what I came up with.

Dual battery tray here: Amazon product

This is designed to fit Optima batteries but like you, I wasn't sure I could pay $200 ea with their reputation so I was actually able to get a couple Interstate Lead Acid batteries to fit in there and I have been happy with them so far. I hear Optima brand batteries are real nice AGM and worth the money but they are expensive! I removed the factory battery tray but kept the base mount in place, positioned this dual battery bracket in there at just the right angle and ran some new holes into the bottom of it so the bolts would thread into the factory base mount. This bracket is strong and works great.

I needed quite a bit bigger alternator since I'm running fridge, on board air, multiple accessory lights, etc. so I went with the Vintage Air alternator/ A/C bracket and a GM 1 wire 200 amp alternator. I went ahead and installed the AC compressor so all the belts and accessories worked properly. I bypassed the factory harness and built a power distribution box with relays for the individual components, you could really design this however you want, thats just how I chose to do it.

Vintage Air FJ40 Alternator bracket: Vintage Air 158209 68-83 FJ40 Land Cruiser Compressor/Alt Bracket - https://www.speedwaymotors.com/Vintage-Air-158209-68-83-FJ40-Land-Cruiser-Compressor-Alt-Bracket,442231.html?sku=721158209&utm_medium=CSEGoogle&utm_source=CSE&utm_campaign=CSEGOOGLE&gclid=Cj0KCQiA-K2MBhC-ARIsAMtLKRsYMELObjcgYBQ6yysZBsP9wIfFyanBNrTWUu1UrTeqIpbkJIz3bKUaAkAVEALw_wcB

I chose not to isolate 1 battery from the other because I would rarely have to worry about running both batteries down and I kept hearing keep it simple is better but you certainly could go with a more sophisticated charging system. Redarc and others have some nice off the shelf products. I simply wired my batteries parallel which keeps the voltage the same but doubles the Ah.

This is the best solution I could find for dual battery and high amp alternator, I hope that helps, there really isn't anything out there that is plug and play anymore for the 40, you basically have to figure it out on your own.

Great reply. Thank you. Looks like I have a bit more research to do. I hadn't really thought about a refrigerator but now that's on the list too. Thanks!
 
kfmarshall

kfmarshall

Joined
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Messages
16
Location
Oakton Virginia
Honestly, unless you're overlanding (like real overlanding, not just outfitting your truck to look like you overland) and doing self-sustained long trips away from civilization, I just don't see the actual NEED for dual batteries. I get that many people want them, but you gotta sort out if you truly want or need it, and then determine what your budget can with stand.

Your symptoms of dimming lights while driving is likely a result of a bad or failing alternator, or an issue in the wiring of the charge circuit, not an issue of reserve capacity in your battery. I would start there FIRST. You state the battery is new, so I don't see the need to spend money on TWO batteries to replace one good one.

What are your intended uses for the truck?
 
FJ40 that green thing

FJ40 that green thing

1996 KZJ78 Prado
Joined
Jul 8, 2004
Messages
198
Location
Wyoming
Better yet is a TOYOTA OEM upgraded harness WITH lights, for the same price.

Here is a visual:

Here is where to get it for $40:


Granted, you gotta spend $75 for free shipping and use code FREESHIP at checkout.
Yup, that would be even better since the lenses usually are ready for replacement as well.
 
kfmarshall

kfmarshall

Joined
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Messages
16
Location
Oakton Virginia
Thanks for this. I will definitely be checking the alternator as well. I'll also look up "charge circuit" and report back. My intended uses for my rig are exactly what it was built for... off roading. And the occasional shopping trip.

Thanks for the response.
 
EWheeler

EWheeler

4 Cruisers, No Garage !
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Messages
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Thanks for this. I will definitely be checking the alternator as well. I'll also look up "charge circuit" and report back. My intended uses for my rig are exactly what it was built for... off roading. And the occasional shopping trip.

Thanks for the response.

When you're off-roading, what are your electrical loads? Does your truck have an engine driven or electric cooling fan? Does your truck have AC? When you say accessories, I assume you're talking about a winch and maybe some LED lights? Anything else? 12v fridge?

I would suggest also switching all lights on your truck to LED bulbs (tail, clearance, turn, marker, dash, etc) . You can get decent LED's for pretty cheap from SuperBrightLEDS.com. A winch is a very intermittent load, as long as you have a good battery and a functioning stock alternator, you should have no issues with intermittent winch use. I never have? LED off-road lights really have a small power draw compared to the old halogens or HID's, so again, you're not really straining your system with a few LED lights. If you want to sit there lit up without the engine on for periods of time, you'll need a battery with decent reserve capacity. Make sure you keep jumper cables in the truck. A small portable jump charger is also a good investment. Odyssey batteries are really top of the line and is what I would put in my truck if/when I need to replace my optima's (optima's in multiple trucks, all with single batteries).
 
P

peesalot

Joined
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Messages
2,943
Location
here
When they dim it is current flow related, bad/corroded connections causing voltage loss, and/or low voltage to start with, the hi/lo beam floor switch is often a source of the resistance. just add a relay.
 
kfmarshall

kfmarshall

Joined
May 17, 2021
Messages
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Location
Oakton Virginia
When you're off-roading, what are your electrical loads? Does your truck have an engine driven or electric cooling fan? Does your truck have AC? When you say accessories, I assume you're talking about a winch and maybe some LED lights? Anything else? 12v fridge?

I would suggest also switching all lights on your truck to LED bulbs (tail, clearance, turn, marker, dash, etc) . You can get decent LED's for pretty cheap from SuperBrightLEDS.com. A winch is a very intermittent load, as long as you have a good battery and a functioning stock alternator, you should have no issues with intermittent winch use. I never have? LED off-road lights really have a small power draw compared to the old halogens or HID's, so again, you're not really straining your system with a few LED lights. If you want to sit there lit up without the engine on for periods of time, you'll need a battery with decent reserve capacity. Make sure you keep jumper cables in the truck. A small portable jump charger is also a good investment. Odyssey batteries are really top of the line and is what I would put in my truck if/when I need to replace my optima's (optima's in multiple trucks, all with single batteries).
This is great information. Thank you. I replaced my headlights with LEDs but I was planning on getting my battery situation sorted before I swapped out all the others. Sounds like I should go ahead and pull the trigger. I'll look at the Odysseys. Thanks for the response.
 
Jonathan Hanson

Jonathan Hanson

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Ewheeler offered some excellent advice, to which I will add:

The number one and two causes of breakdowns in the backcountry are tire issues and battery failure. Having some form of battery backup is therefore a smart idea if you plan to travel off the beaten track. If a fridge is on your wish list, a second, deep-cycle, battery is almost a must. Contrary to what some think, if you have a starting battery and a deep-cycle battery in your system, the winch should be run off the starting battery. A starting battery is designed to deliver a lot of amperage for a short time, which describes most winching scenarios. A deep-cycle battery is designed to deliver lower amperage over a longer period.

Redarc makes superb battery management systems for this application, and the tried and true National Luna system is excellent as well.

Dropping a high-power alternator in an FJ40 is problematic, since all the alternator output runs through the ammeter in your gauge cluster. Realistically, unless you run an ammeter shunt, 55 amps or so is about maximum, and that's plenty, especially if you swap to LED bulbs and LED driving lamps, if you run the latter.

Optima did indeed go through a bad period after they moved their factory, but in the last few years things seem to have improved. With that said, I agree that Odyssey is a top choice for AGM batteries right now.
 
kfmarshall

kfmarshall

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Messages
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Location
Oakton Virginia
Ewheeler offered some excellent advice, to which I will add:

The number one and two causes of breakdowns in the backcountry are tire issues and battery failure. Having some form of battery backup is therefore a smart idea if you plan to travel off the beaten track. If a fridge is on your wish list, a second, deep-cycle, battery is almost a must. Contrary to what some think, if you have a starting battery and a deep-cycle battery in your system, the winch should be run off the starting battery. A starting battery is designed to deliver a lot of amperage for a short time, which describes most winching scenarios. A deep-cycle battery is designed to deliver lower amperage over a longer period.

Redarc makes superb battery management systems for this application, and the tried and true National Luna system is excellent as well.

Dropping a high-power alternator in an FJ40 is problematic, since all the alternator output runs through the ammeter in your gauge cluster. Realistically, unless you run an ammeter shunt, 55 amps or so is about maximum, and that's plenty, especially if you swap to LED bulbs and LED driving lamps, if you run the latter.

Optima did indeed go through a bad period after they moved their factory, but in the last few years things seem to have improved. With that said, I agree that Odyssey is a top choice for AGM batteries right now.
The winch comment makes a ton of sense. Thanks. That's the first time I've seen that (maybe because it's intuitive and most just understand it to be true). I've got a few more years of getting my rig in order before I go off grid for days on end, but that is the ultimate objective. I really appreciate the well-crafted answer. It filled in a lot of blanks for me. Thank you.
 
FJ40 that green thing

FJ40 that green thing

1996 KZJ78 Prado
Joined
Jul 8, 2004
Messages
198
Location
Wyoming
"Dropping a high-power alternator in an FJ40 is problematic, since all the alternator output runs through the ammeter in your gauge cluster. Realistically, unless you run an ammeter shunt, 55 amps or so is about maximum, and that's plenty, especially if you swap to LED bulbs and LED driving lamps, if you run the latter."

Not necessarily, depends how you do it. You can bypass the factory charge wire and ammeter all together with a 1 wire internally regulated alternator and use a voltmeter. Running a high power alternator through the factory system is problematic however.
 
Adarcy

Adarcy

Joined
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Messages
170
Location
Carlsbad, CA
I run a dual battery setup, currently an Optima Red top for starting and a Yellow top for a house battery. House battery is primarily for the winch and fridge for camping trips. Probably not necessary, but it gives some nice peace of mind.

Key is to protect your starting battery. I use one of the Bluesea ACR's that disconnects the batteries if the starting battery drops too low.

Your original problem though of dimming lights sounds alternator or wiring related as the others pointed out :)

Oh, and I will say that I recently put dual Odyssey batteries in my 4runner. They blow away the Optima's in terms of reserve capacity in like for like sizes. Very pleased.
 

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