Dual batteries under the hood
07-27-2003, 09:03 PM
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Dual batteries under the hood
[EDIT 6-13-05] I added an article to my website on the dual battery system. CLICK HERE
Hey folks, I first mentioned that I was working on a dual battery setup in WATRD's thread regarding his new high-output alternator. So, this is a follow up on the progress. Get ready for a looooooooong post
OK, first a brief summary of the setup. I started out with an Optima Red Top, and I got an Optima Yellow D31T to go with it. The D31T is a "group 31" battery, so it is a bit larger than the standard Optima car batteries. I found that the D31T will fit in the stock battery location of my '98 Tacoma, with a new bracket being necessary. The clearance from the top of the posts to the underside of the hood is pretty close, but it works. I had to trim the Toyota plastic battery tray a little bit to accomodate the additional length of this battery. I got the battery with the 3/8" threaded studs so I could easily attach accessories to it. The Red Top has been relocated to the pass. side wheel well (where my QuickAir II used to be), and is still the starting battery.
Now for some more details. I decided to go with a battery combiner/isolator. After giving it some thought, I decided that a standard diode type isolator has a voltage drop that would mean a longer charging time to get my aux. battery back up to a full charge. Standard isolators have up to a .70 volt drop, so whatever your alternator usually charges the batteries up to (13.8V ?) would be dropped by that much, and take that much longer to recharge. Some people are saying that this also does not fully charge the batteries, so their respective lives are shortened. I don't know how true that is. I figured this might not be good if we drain the aux. battery at a camp, and then only want to drive a short distance before the next camp. SteveS does fine with his, so I wasn't too worried about this, but figured I would avoid the voltage drop if I could.
So, I ended up getting a 100 amp Pathmaker unit (from the makers of the Link 10, 20 battery monitors). It will automatically combine both batteries for simultaneous charging when a voltage source (alternator) is present, and disconnect them when the alternator is off, so my aux. battery cannot drain the starter battery. Additionally, it has a cutoff switch that will disconnect the batteries altogether if they begin to overcharge. All of the switch points come with factory settings, but can be user adjusted. There are LED indicators to tell what state of operation the unit is in (connected, disconnected, shut off). There is also a moment switch that will combine the batteries for an emergency start, but I probably will not use this because I don't want to burn up the contacts. (...more on this if you care to know).
Cost was a major factor (unfortunately) and all of the units I looked at without a voltage drop (xantrex pathmaker, west marine, hellroaring, etc.) were really expensive. I found a used xantrex pathmaker with a 30 day guarantee for $55 incl. shipping (it's a $179 unit new) so I figured what the heck, that's not much more than a new diode type isolator. Now that I have it, I am finding out that it might be a challenge to water-proof it. I'll probably end up making a cover for it.
Now is the time for me to mention a HUGE THANKS to Mark (crawler#976 here at Yotatech) for building the new battery housing and bracketry required for this project. Yea, I helped him, but he did most of the work and all of the welding. Last weekend we did the housing for the Red Top, and this weekend we did the new bracket for the Yellow Top.
Today, I finished prepping the brackets/hardware for paint, and painted the necessary coats throughout the day. In between coats, I worked on taking apart some of the stock wiring, and making up new cables. I used copper lugs, and 1 gauge copper cable. I put the lugs in a vice and heated them up with a torch, filled them with molten rosen-core solder, and then stuffed the cables in while it was all hot. At this point I have the two batteries installed, but I don't have the combiner/isolater mounted and hooked up. I somehow ended up short of one lug, and a big storm was on it's way through town, so I figured it was time for me to call it a day at around 5:45 pm. I took a few pics. You might see some temporary wiring floating around in these pics, but you'll get the idea. I still need to rework the mount for the cruise control actuator, which will shift a bit from it's stock location, and be closer to the air box.
This is the first time I have seen two batteries under the hood of a Tacoma, let alone one of them being a group 31 battery. I'm sure I'm not the first person to do it (dual batteries under a Taco hood), but I have never seen it myself.
PIC 1 - an overview (kinda large photo 100kb)
PIC 2 - The Red Top mounted on it's side in the new housing, and hooked up
PIC 3 - The Yellow Top in the stock battery location, with new bracket
Why am I doing all of this? See this post
Hey folks, I first mentioned that I was working on a dual battery setup in WATRD's thread regarding his new high-output alternator. So, this is a follow up on the progress. Get ready for a looooooooong post
OK, first a brief summary of the setup. I started out with an Optima Red Top, and I got an Optima Yellow D31T to go with it. The D31T is a "group 31" battery, so it is a bit larger than the standard Optima car batteries. I found that the D31T will fit in the stock battery location of my '98 Tacoma, with a new bracket being necessary. The clearance from the top of the posts to the underside of the hood is pretty close, but it works. I had to trim the Toyota plastic battery tray a little bit to accomodate the additional length of this battery. I got the battery with the 3/8" threaded studs so I could easily attach accessories to it. The Red Top has been relocated to the pass. side wheel well (where my QuickAir II used to be), and is still the starting battery.
Now for some more details. I decided to go with a battery combiner/isolator. After giving it some thought, I decided that a standard diode type isolator has a voltage drop that would mean a longer charging time to get my aux. battery back up to a full charge. Standard isolators have up to a .70 volt drop, so whatever your alternator usually charges the batteries up to (13.8V ?) would be dropped by that much, and take that much longer to recharge. Some people are saying that this also does not fully charge the batteries, so their respective lives are shortened. I don't know how true that is. I figured this might not be good if we drain the aux. battery at a camp, and then only want to drive a short distance before the next camp. SteveS does fine with his, so I wasn't too worried about this, but figured I would avoid the voltage drop if I could.
So, I ended up getting a 100 amp Pathmaker unit (from the makers of the Link 10, 20 battery monitors). It will automatically combine both batteries for simultaneous charging when a voltage source (alternator) is present, and disconnect them when the alternator is off, so my aux. battery cannot drain the starter battery. Additionally, it has a cutoff switch that will disconnect the batteries altogether if they begin to overcharge. All of the switch points come with factory settings, but can be user adjusted. There are LED indicators to tell what state of operation the unit is in (connected, disconnected, shut off). There is also a moment switch that will combine the batteries for an emergency start, but I probably will not use this because I don't want to burn up the contacts. (...more on this if you care to know).
Cost was a major factor (unfortunately) and all of the units I looked at without a voltage drop (xantrex pathmaker, west marine, hellroaring, etc.) were really expensive. I found a used xantrex pathmaker with a 30 day guarantee for $55 incl. shipping (it's a $179 unit new) so I figured what the heck, that's not much more than a new diode type isolator. Now that I have it, I am finding out that it might be a challenge to water-proof it. I'll probably end up making a cover for it.
Now is the time for me to mention a HUGE THANKS to Mark (crawler#976 here at Yotatech) for building the new battery housing and bracketry required for this project. Yea, I helped him, but he did most of the work and all of the welding. Last weekend we did the housing for the Red Top, and this weekend we did the new bracket for the Yellow Top.
Today, I finished prepping the brackets/hardware for paint, and painted the necessary coats throughout the day. In between coats, I worked on taking apart some of the stock wiring, and making up new cables. I used copper lugs, and 1 gauge copper cable. I put the lugs in a vice and heated them up with a torch, filled them with molten rosen-core solder, and then stuffed the cables in while it was all hot. At this point I have the two batteries installed, but I don't have the combiner/isolater mounted and hooked up. I somehow ended up short of one lug, and a big storm was on it's way through town, so I figured it was time for me to call it a day at around 5:45 pm. I took a few pics. You might see some temporary wiring floating around in these pics, but you'll get the idea. I still need to rework the mount for the cruise control actuator, which will shift a bit from it's stock location, and be closer to the air box.
This is the first time I have seen two batteries under the hood of a Tacoma, let alone one of them being a group 31 battery. I'm sure I'm not the first person to do it (dual batteries under a Taco hood), but I have never seen it myself.
PIC 1 - an overview (kinda large photo 100kb)
PIC 2 - The Red Top mounted on it's side in the new housing, and hooked up
PIC 3 - The Yellow Top in the stock battery location, with new bracket
Why am I doing all of this? See this post
Last edited by BajaTaco; 06-13-2005 at 09:07 AM.
07-28-2003, 06:56 AM
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This looks really good, almost stock like the optional dual battery setup on the Diesel Surfs (like mine). Interestingly on the Surfs it seems that the Dual batteries are wired in Parallel to increase the current capacity for the starter however a few people just use bigger batteries and wire one as a Leisure battery (deep Cycle) for running stuff when off road.
I presume that the Petrol engine takes more space that is why you don't see factory dual battery setups.
Only problem that it gives on the Surf is that changing the headlamp bulbs is a 40 minute job instead of a couple of minutes job.
Good job you done there.
Cheers
I presume that the Petrol engine takes more space that is why you don't see factory dual battery setups.
Only problem that it gives on the Surf is that changing the headlamp bulbs is a 40 minute job instead of a couple of minutes job.
Good job you done there.
Cheers
07-28-2003, 07:37 AM
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Re: Dual batteries under the hood
You should be very happy with the Pathmaker unit. I sell them out of my shop and have never seen one returned, which is rare in electrical equip. Very nice looking install also. I have two group 31 AGM batteries, similar to Optima blue tops, mounted in the bed, along with a starting battery under the hood. The two AGMs have the option of running accessories like the Hella lights, or they can be combined for 24 volts for the DC welder I just received (see thread in 4x4 section). I went with a West Marine combiner to charge the AGMs (I get them cheap) and have 2 gauge wire linking all the batteries through an on/off switch if I need the extra power for the winch. My installation isn't as pretty as yours, but neither is my truck. At this point I'm just going for functional. If I get to AZ this fall I'll be sure to come find you on the trails for a cold one.
Originally posted by BajaTaco
[So, I ended up getting a 100 amp Pathmaker unit (from the makers of the Link 10, 20 battery monitors). It will automatically combine both batteries for simultaneous charging when a voltage source (alternator) is present, and disconnect them when the alternator is off, so my aux. battery cannot drain the starter battery.
This is the first time I have seen two batteries under the hood of a Tacoma, let alone one of them being a group 31 battery. I'm sure I'm not the first person to do it (dual batteries under a Taco hood), but I have never seen it myself.
]
[So, I ended up getting a 100 amp Pathmaker unit (from the makers of the Link 10, 20 battery monitors). It will automatically combine both batteries for simultaneous charging when a voltage source (alternator) is present, and disconnect them when the alternator is off, so my aux. battery cannot drain the starter battery.
This is the first time I have seen two batteries under the hood of a Tacoma, let alone one of them being a group 31 battery. I'm sure I'm not the first person to do it (dual batteries under a Taco hood), but I have never seen it myself.
]
Last edited by MNBOY; 07-28-2003 at 07:38 AM.
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07-28-2003, 07:46 AM
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Thanks Andy! Do you have the dual-batt. setup on your Surf? It must be nice to have that as a factory option! You mentioned parallel bateries, so I am assuming that they are mounted side-by-side? You could almost do that on the Tacoma, but the space isn't quite large enough to place tandem batteries.
07-28-2003, 08:19 AM
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The batteries are mounted the same as yours, one either side. They are wired in parallel basically cos the stock batteries aren't really man enough for the starter motor on the Diesel. They are only an option mind you on the SSRX and SSRG, not available on the SSR or SSRV or SSR Limited. Wired together the provide the 700 amps plus that the starter needs.
However with an Optima Red Top and a Yellow top you get a battery that will run the Starter and one that will work as a leisure battery. I think that is really the ideal setup mind you at least with the Toyota option you can run quite a lot of electrics and still start the car OK.
Cheers
However with an Optima Red Top and a Yellow top you get a battery that will run the Starter and one that will work as a leisure battery. I think that is really the ideal setup mind you at least with the Toyota option you can run quite a lot of electrics and still start the car OK.
Cheers
07-28-2003, 12:17 PM
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Re: Re: Dual batteries under the hood
Originally posted by MNBOY
You should be very happy with the Pathmaker unit. I sell them out of my shop and have never seen one returned, which is rare in electrical equip............
You should be very happy with the Pathmaker unit. I sell them out of my shop and have never seen one returned, which is rare in electrical equip............
Does the mounting location have to be 100% dry? After looking at the unit, I was concerned about exposing the circuit board to underhood conditions-----
later
07-28-2003, 12:32 PM
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That's the way to go. Very good and clever setup.
Your right about the voltage drop. A normal (non-adjustable voltage) alternator will only recharge your battery up to 85-90%. And eventually shorten its life substancialy if its a lead cell bat. I'm not sure about the optima's. Wouldn't recommend it though!
Your right about the voltage drop. A normal (non-adjustable voltage) alternator will only recharge your battery up to 85-90%. And eventually shorten its life substancialy if its a lead cell bat. I'm not sure about the optima's. Wouldn't recommend it though!
07-28-2003, 01:56 PM
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Re: Re: Dual batteries under the hood
Originally posted by MNBOY
You should be very happy with the Pathmaker unit. I sell them out of my shop and have never seen one returned, which is rare in electrical equip. Very nice looking install also. I have two group 31 AGM batteries, similar to Optima blue tops, mounted in the bed, along with a starting battery under the hood. The two AGMs have the option of running accessories like the Hella lights, or they can be combined for 24 volts for the DC welder I just received (see thread in 4x4 section). I went with a West Marine combiner to charge the AGMs (I get them cheap) and have 2 gauge wire linking all the batteries through an on/off switch if I need the extra power for the winch. My installation isn't as pretty as yours, but neither is my truck. At this point I'm just going for functional. If I get to AZ this fall I'll be sure to come find you on the trails for a cold one.
You should be very happy with the Pathmaker unit. I sell them out of my shop and have never seen one returned, which is rare in electrical equip. Very nice looking install also. I have two group 31 AGM batteries, similar to Optima blue tops, mounted in the bed, along with a starting battery under the hood. The two AGMs have the option of running accessories like the Hella lights, or they can be combined for 24 volts for the DC welder I just received (see thread in 4x4 section). I went with a West Marine combiner to charge the AGMs (I get them cheap) and have 2 gauge wire linking all the batteries through an on/off switch if I need the extra power for the winch. My installation isn't as pretty as yours, but neither is my truck. At this point I'm just going for functional. If I get to AZ this fall I'll be sure to come find you on the trails for a cold one.
Whoa - weird... I never saw your post until I saw Mark quoting it. Then I went back up the thread and saw it - I guess I was writing my response to Andy when you posted. Thanks - that's good to hear about the Pathmaker. Your setup sounds POWERFUL! That sounds like a great way to go when you have a winch and a welder
NICE!!!SteveS - yea, I like the reason too!! hehehehe
Mark - I just called Xantrex regarding the Pathmaker. They said it's not suitable for the Taco engine bay (dust/moisture). They are rated for working temps of -40F to 149F, so if I make a cover for it I might try it. Or maybe I'll just sell it and go with something else - but I really want to use it!!
Hey 96 and 4ever - thanks!!
07-28-2003, 06:00 PM
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Re: Re: Re: Dual batteries under the hood
Just mount the combiner in the cab and run battery cable to and from it through the firewall. I have mine mounted under the dash on the drivers side where the crappy stock speaker used to be. Works great and I can see the LEDs while I'm driving. Let me know if you have any questions on the install, I've put quite a few of them in boats.
Originally posted by BajaTaco
Whoa - weird... I never saw your post until I saw Mark quoting it. Then I went back up the thread and saw it - I guess I was writing my response to Andy when you posted. Thanks - that's good to hear about the Pathmaker. Your setup sounds POWERFUL! That sounds like a great way to go when you have a winch and a welder NICE!!!
Mark - I just called Xantrex regarding the Pathmaker. They said it's not suitable for the Taco engine bay (dust/moisture). They are rated for working temps of -40F to 149F, so if I make a cover for it I might try it. Or maybe I'll just sell it and go with something else - but I really want to use it!!
Whoa - weird... I never saw your post until I saw Mark quoting it. Then I went back up the thread and saw it - I guess I was writing my response to Andy when you posted. Thanks - that's good to hear about the Pathmaker. Your setup sounds POWERFUL! That sounds like a great way to go when you have a winch and a welder
NICE!!!Mark - I just called Xantrex regarding the Pathmaker. They said it's not suitable for the Taco engine bay (dust/moisture). They are rated for working temps of -40F to 149F, so if I make a cover for it I might try it. Or maybe I'll just sell it and go with something else - but I really want to use it!!
07-28-2003, 07:20 PM
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Wow, good job. I may have to copy your setup when I finally get around to doing the dual-batt.
One quick question...where's your QuickAirII now?
I've been thinking on keeping that same spot open for a second battery...and about all I can think of for onboard air is to mount a York compressor on the lower / passenger-side of the engine.
(this all depends how the York does if it gets wet)
Or...move it to the bed of the truck...
Jim
One quick question...where's your QuickAirII now?
I've been thinking on keeping that same spot open for a second battery...and about all I can think of for onboard air is to mount a York compressor on the lower / passenger-side of the engine.
(this all depends how the York does if it gets wet)
Or...move it to the bed of the truck...
Jim
07-29-2003, 09:22 AM
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One thing with mounting the combiner in the cab, you will need to use really good battery cable as the resistance of the cables can be considerable. I once ran a remote battery isolator on a mini and untill I upgraded the original cables that I put in, the starter would only turn over very slowly.
Cheers
Cheers
