Grounding aux battery.

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Sep 11, 2012
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Vancouver, B.C.
 
I'm trying to set up an auxiliary battery for a winch, fridge, etc. Seems like there are a dizzying number of options for doing that. I'm not super skilled with electrical, so I go slow and careful. I have a couple of questions to start:

1. What is the best ground for the aux battery? Same ground on the engine as the starting battery?

2. Is it possible to overcharge and damage or fry a Deep cycle AGM battery with a normal voltage regulated alternator? My alternator puts out maybe 70 amps.
 
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Sep 11, 2012
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Truck is a 1990 w. 22RE. I've done a bunch more research on Mud and other sites. Still sticking to my playoff running a second alternator, and keeping my start battery totally isolated. I also posted in '95 and earlier Toyota Truck Tech. Need to redo some alternator wiring. Theoretically I just need to duplicate the wiring and fusing of the main alternator for a second alternator to work. I traced some of the wiring physically to the under hood fusebox. The charge warning and ignition circuits are a little harder to trace through the firewall, so I'm going on the multipage diagram in the FSM. I'm not excellent with wiring so I can't tell what's crucial, what can be upgraded, what can be eliminated, and so on. Any tips are good. Here is a rough diagram of the proposed alternator wiring and fusing:
20200527_225411.jpg
Sorry about the drawing. R = red to ignition switch. W = white to 40 amp fuse. Sensor wire. W= white to 80 amp fuse Alternator output to Batt. Y = yellow to charge warning circuit, dash voltmeter, and 2 fuses. F.L = Fusible link main between fuse box and batt positive. Basically my condensed version of the FSM. Questions: Sensor wire runs through 40 amp fuse before joining batt. wire circuit downstream of the 80 amp alt fuse? Do I even need the yellow charge warning circuit to make the alternator run? I can just put a voltmeter somewhere in the system later to watch voltage on second system? Keep all wire gauges the same as Toyota? Colours are the same in drawing. Splice T-junctions with? solder and heat shrink or? I will probably use mostly ring terminals at fuses and fuse boxes, alternator output post, etc. I'm presuming red wire turns voltage regulator on, sensor wire determines how much voltage is needed, and batt wire supplies the voltage to the battery.
 
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Sunnyvale, CA
 
 
 
The charge light on older alternators serves a very important job - on initial startup it provides +12V to the field to 'boot' the alternator up. That's why the light glows on during cranking/starting. Once the alternator is running, its field goes to +12V and so the charge light goes off, since it has +12V on both sides. So, yes, you need the charge light or at least a resistor that mimics the typical resistance of the charge bulb.

cheers,
george.
 
Joined
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Messages
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The charge light on older alternators serves a very important job - on initial startup it provides +12V to the field to 'boot' the alternator up. That's why the light glows on during cranking/starting. Once the alternator is running, its field goes to +12V and so the charge light goes off, since it has +12V on both sides. So, yes, you need the charge light or at least a resistor that mimics the typical resistance of the charge bulb.

cheers,
george.
So I would be best to wire the charge wire to a 7.5 fuse (charge), a light, another 7.5 fuse (ignition) splice to ignition 2, then the 30amp AM2 fuse? In other words duplicating the original change circuit on the first alternator. This is the part that confuses me the most. Or could I just splice into the start alternator system before the 7.5 charge fuse? That would mean two alternators being on the same charge circuit, but briefly? Or would that risk overloading that circuit?
 
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^ I would recommend the 2nd alternator gets its own fuse and charge light setup. Sharing a charge light between both alternators isn't a good idea since with only one light you wouldn't know if one of the alternators has a problem and isn't charging. Also, double the current would need to be provided with only one charge light and you may have to experiment with a different bulb (higher wattage) to ensure both alternators start up.

cheers,
george.
 
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I definitely won't be interfering with the original charge warning circuit. I need that. I want both circuits to be as separate as possible. In theory it looks very doable, but in practice I'm having trouble figuring out where to start the second charging, gauge, ignition wires and fuses. Looks possible to add downstream of the under hood fusebox charge fuse, but possible I have to go to the 2 AM1 and AM2 circuits that are activated by the ignition switch.
 

abuck99

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With the time and expense of installing totally isolated system with a 2nd alt, pulley(s), wiring, warning light etc- have you considered a GoalZero 1000 set up(100ah)- with a solar panel as a back up? You can charge the GZ from cig lighter while rolling, and top off from solar when stationary. And you can use it in the house when the power goes out.
 
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I'm looking at solar down the road, to charge when camped for multiple days. I sometimes leave the truck for multiple days at -30, so I'm trying to keep the starting battery as isolated as possible. Solar won't be that useful for about 6 months here, but great if I travel South. If the border ever opens.:) I have always had the second alt and the pulley ( there is not ac on the truck, just the bolt holes), so I just need to figure out the wiring and fusing, and the second battery will charge while driving. Mostly it will run the fridge, some charge outlets, and maybe some camp lights down the road. There is a winch too, but that use should be limited, and is not fused. I have at least 3 alternators kicking around, so the biggest cost is the battery, and a lot of time faffing about to put it in.
 
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4,673
 
 
 
 
Not to sway you from the 2nd alternator route because that is interesting in itself...You might be surprised how well a panel will keep a battery (or batteries) maintained if you have no big load on them when parked. I'm in the Fraser Valley. I threw one of those cheap Cdn Tire 40 watt panels on the roof of my 80 one winter, parked on the south side of a building with no shading for the low winter sun. This would keep the two 27 series DP batteries topped right up for months through the grey. Turned the fridge on as an experiment and within 2-3 days the batteries were low. But with no big load it was fine. When you're parked and away this would depend on if you can locate yourself outside of any winter shadows and does not account for snow. And two legged critters that might think your panel is theirs.

I've got a 100 watt 12V panel and MPPT charge controller full time in the 80 now and when it's out in the winter it's always putting something into the batteries, unless parked in a shadow.

hth's
gb
 
Joined
Sep 11, 2012
Messages
533
Location
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Not to sway you from the 2nd alternator route because that is interesting in itself...You might be surprised how well a panel will keep a battery (or batteries) maintained if you have no big load on them when parked. I'm in the Fraser Valley. I threw one of those cheap Cdn Tire 40 watt panels on the roof of my 80 one winter, parked on the south side of a building with no shading for the low winter sun. This would keep the two 27 series DP batteries topped right up for months through the grey. Turned the fridge on as an experiment and within 2-3 days the batteries were low. But with no big load it was fine. When you're parked and away this would depend on if you can locate yourself outside of any winter shadows and does not account for snow. And two legged critters that might think your panel is theirs.

I've got a 100 watt 12V panel and MPPT charge controller full time in the 80 now and when it's out in the winter it's always putting something into the batteries, unless parked in a shadow.

hth's
gb
That's good to know. I'm hoping to get into solar pretty soon. Can you also charge with 120volt shore power with the MPPT or just with the solar panels? Are your panels fixed in place on the roof or can you move or adjust them to follow the sun?
 
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That's good to know. I'm hoping to get into solar pretty soon. Can you also charge with 120volt shore power with the MPPT or just with the solar panels? Are your panels fixed in place on the roof or can you move or adjust them to follow the sun?
Can not charge 120V with the Victron charge controller (though mine is the 100/15 simply due to availability at the time) and the panel is fixed. Not ideal, but a fixed panel is way better then no panel right off the get go. When parking I do have to consider shade and orientation for the morning sun. The plan is to put T's in place at the roof connection so if choosing shade or lay of the land is not ideal I can T in a flexible or folding panel which can be placed in the sun. There are some good threads with different ideas presented and discussed to weed through in this section when you get to that point.

hth's
gb
 
Joined
Sep 11, 2012
Messages
533
Location
Vancouver, B.C.
 
Not to sway you from the 2nd alternator route because that is interesting in itself...You might be surprised how well a panel will keep a battery (or batteries) maintained if you have no big load on them when parked. I'm in the Fraser Valley. I threw one of those cheap Cdn Tire 40 watt panels on the roof of my 80 one winter, parked on the south side of a building with no shading for the low winter sun. This would keep the two 27 series DP batteries topped right up for months through the grey. Turned the fridge on as an experiment and within 2-3 days the batteries were low. But with no big load it was fine. When you're parked and away this would depend on if you can locate yourself outside of any winter shadows and does not account for snow. And two legged critters that might think your panel is theirs.

I've got a 100 watt 12V panel and MPPT charge controller full time in the 80 now and when it's out in the winter it's always putting something into the batteries, unless parked in a shadow.

hth's
gb
What kind of fridge is it and what does it draw?
 
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Mar 28, 2002
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4,673
 
 
 
 
Its a 2005 ARB (the old school metal sided ones that are a mirror of the Engel MT-45). I have not hooked it up to the load side of the solar controller so don't have accurate 24hr usage stats. Would be around a couple AH anyway I would think.

hth's
gb
 
Joined
Sep 11, 2012
Messages
533
Location
Vancouver, B.C.
 
Anybody have any idea of the size, model and location of the diode in a charge warning circuit for a 1990 Toyota pickup? In the gauge cluster? or? I'm trying to avoid pulling my dash apart if I don't need to.
 
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