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PostPosted: Fri Apr 20, 2018 12:59 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13008
Location: Fircrest, WA
Car Model: 76 D100
This is not another thread about upgrading to a late mondel Nippondenso thread. Rather, it is a question about how to upgrade to the huge Chrysler 100 amp alternator in a charging system that has dual batteries separated by a battery isolator.

My 82 Ramcharger currently has a single pulley alternator of unknown amp output. It is a remanufactured unit so I have no way of knowing what the actual rating is. The previous owner of the truck had set it up for off-roading and had installed a Warn electric winch and winch bumper, but ran the truck into a tree, bending the bumper. I have replaced the winch and winch bumper with a stock bumper.

To support the electric winch, the prior owner installed a second battery and a battery isolator. I have kept the isolator and second battery in place as a power supply for the stereo system my brother installed in the truck. Two amps, six speakers, and a subwoofer. I have no idea how it all works.

I would like to install air conditioning in the truck. To that end, I have purchased a set of factory AC compressor mounting brackets to install a Sanden style compressor. Attached to the alternator bracket is one of the huge Chrysler 100 amp alternators. I would like to ugrade to this alternator, but I have a question about the wiring. I plan on using a field-sensing relay. I also plan on keeping both batteries if possible.

The alternator has a separate ground that will go to the frame of the truck. The field sensing relay gets wired in as mentioned in the factory service manual scan Dan sent me (thanks Dan!) and the field wires plug in as normal.

My question is how do I wire the batteries and isolator positive feeds/outputs. The isolator grounds through its body. The + feed of the alternator goes to a lug on the isolator and then the isolator has two outputs, one for each battery. If I plan on keeping both batteries do I just run 10 gauge wire from the alternator to the isolator and then from the isolator to (a) the second battery and (b) the starter motor/main battery?

Would it be a better idea to just ditch the isolator and second battery? Simpler circuit, less points of potential failure? Thanks.

P.S. while the Ramcharger has a 318, I also plan on doing this same upgrade (AC, big amp alternator) to my 76 D100 that is slant powered so anything I learn doing it on the Ramcharger will be directly applied to the D100.


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PostPosted: Fri Apr 20, 2018 4:00 pm 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
The sole purpose of a battery isolator is to keep the engine starting battery from being drained by accessory loads like a refrigerator or furnace. If you aren't operating accessory loads with the engine off you don't need it. I would not have installed a battery isolator with the winch myself and unless you intend to pump the stereo until the auxiliary battery is dead I wouldn't keep it.

Also, for 100 amps you want AWG 8 wire or better.

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Joshua


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PostPosted: Fri Apr 20, 2018 5:05 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13008
Location: Fircrest, WA
Car Model: 76 D100
Thanks, Josh! At this point I am just working with what was on the truck when I got it. I am not a big car stereo guy, so I will just remove the isolator and second battery and simplify the whole system.

8 gauge or bigger it is!


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PostPosted: Wed May 30, 2018 10:26 am 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 214
Location: Upper So. CA
Car Model: '65 Valiant 170 T5
It is likely that the isolator is a diode type, which is doing a disservice to the aux battery by never fully charging it. If you keep the aux battery you have two options; A) wire it directly parallel to the starting battery creating a starting battery bank, B) use a smart battery separator that does fully charge the aux battery while still keeping it isolated when the alternator is not charging.

If you opt for A, connect the batteries + to + and - to - with large cable. Then I would suggest that the grounding be at one battery only, and the power tap be at the other. A very slight difference in potential between the batteries can set up a destructive discharge see-saw cycle. I had this happen to me where both batteries were grounded to different points on the engine block. The resistance across the block between those points was enough to cause trouble. To do this the mil-spec battery terminals and eyelet lugs make things easy. Like these though my local CarQuest has better prices: https://www.amazon.com/dp/B00GOCGLZQ/ NOT like these poor Pico copies: https://www.amazon.com/Crimp-Supply-Mil ... B01FMOG3AO

If you opt for method B I suggest this smart combiner: http://www.bepmarine.com/en/710-140a

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Thom

Cross-threaded is tighter than Lock-tite


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PostPosted: Wed May 30, 2018 11:24 am 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
A diode battery isolator puts both batteries "downstream" of a diode and moves the voltage regulator sense downstream as well to compensate for the small voltage drop.

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Joshua


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PostPosted: Wed May 30, 2018 1:55 pm 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 214
Location: Upper So. CA
Car Model: '65 Valiant 170 T5
Nope, not all of them do that. In fact most of them floating around out there don't do that. Only recent production versions do it. And none of them allow the starting battery to be fully re-charged before connecting the aux battery like the smart(er) relay type isolators do. Diode type just aren't found in systems where battery charging is taken seriously. They're only found in systems where the cheapest solution is desired.

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Thom



Cross-threaded is tighter than Lock-tite


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PostPosted: Wed May 30, 2018 3:53 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
Use a relay on starting battery.

Starting battery is only connected to rest of system when IGN is on.

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

8)


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PostPosted: Fri Jun 08, 2018 2:24 am 
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3 Deuce Weber

Joined: Fri Oct 12, 2012 7:35 pm
Posts: 60
Car Model:
Relay is a good way of doing it. You can get Voltage sensitive relays now pretty cheap. Try searching for VSR.
They parallel the batteries once the first battery (usually starting battery) reaches a certain voltage, usually around 14 volts and then it parallels the battery to the second battery.

As above a simple relay will also work. You could fit it to the ignition switch, but that does not safe guard against accidentally leaving ignition on, and you could end up with two flat batteries. I have an oil pressure switch connected to a relay, so it will only parallel the batteries once engine is running.

As above forget Diodes. For a start you automatically reduce the voltage by half a volt, so it will not charge as efficiently and reaching a fully charged battery will be reduced.

As for the High amp alternator, remember that when charging full output that it takes a lot of power to drive. I have a 30 amp alternator on my boat that is charging a 400 amp hour battery. It is run by a single B section belt, and when the batteries are fairly discharged the belt really struggles. You have to have it really tight, or it slips, and it always has dust around it. If you want serious charging for big batteries, you really need to consider your belts that are driving, either double belts, multi rib, or notched belts.
A lot of people get confused about the output of an alternator. It is regulated by voltage, so once the regulated voltage is reached, the output is cut back. People go and purchase a big output alternator and put it on a small battery. The output is only high for the first few seconds until it reaches say approx 14 volts and then you get the alternator reducing its output to say 10 - 20 amps.

It may be a good idea if you consider how big of alternator you really need. A smaller output alternator will be most likely a lot cheaper.
In most cases, if you want better charging, starting at the regulator is often best. You can get smart regulators now that optimise the charge rates. It takes factors into account such as battery temperature etc, and will allow the voltage to go higher when the battery allows it, so you get a better charged battery in a quicker time.

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1967 VC Valiant


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PostPosted: Fri Jun 08, 2018 7:22 am 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
ntsqd wrote:
Nope, not all of them do that. In fact most of them floating around out there don't do that. Only recent production versions do it. And none of them allow the starting battery to be fully re-charged before connecting the aux battery like the smart(er) relay type isolators do. Diode type just aren't found in systems where battery charging is taken seriously. They're only found in systems where the cheapest solution is desired.


Huh, I guess the sense wire connection on the 20+ year old diode isolator unit I have doesn't really exist then. :roll:

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Joshua


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PostPosted: Fri Jun 08, 2018 9:15 am 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 214
Location: Upper So. CA
Car Model: '65 Valiant 170 T5
You didn't read what I said. That was that not all of them have the sense terminal, only newer versions do. Since they've been around since the 60's that means that there are a lot more out there that don't have the sense terminal than those that do have it.

In any case, a diode bridge, sense terminal or not, is a poor solution to this need. The various "Voltage Sensing Relay"s or "Automatic Charge Relay"s currently on the market are a far better solution if you care about battery and alternator life.

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Thom



Cross-threaded is tighter than Lock-tite


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PostPosted: Fri Jun 08, 2018 4:12 pm 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
I read what you wrote, but I don't agree. How many of those 1960's diode isolators, and the campers and RVs they were installed to support do you think are extant?

I disagree that the diode isolator is a poor choice. Is it the Cadillac choice? No. It's also not the Cadillac price. They are simple and highly reliable, more so than a solenoid. The drawback is the voltage drop, but that's not a serious issue. Has it been made out to be a serious issue? Sure. By those selling competing products. If the charging system were to put 100 amps through a 0.6V drop the isolator will only dissipate (lose to heat) 60W. Sure, that's 4 amps at 15V, but this is an extreme condition for most road vehicles where the batteries are relatively small compared to the alternator output. Most battery recharging is done at a lower rate and over a long period of time as the battery's charge acceptance does not support high rate charging at healthy charging system voltages. A lead acid battery wants, for long life, to be recharged at about .2C or 20 amps for a 100 ah capacity.

The scenario changes when there is a large battery bank that can load the alternator for a significant amount of time. If the battery required full alternator output for even an hour to recharge then I would consider other battery isolation schemes. A group 34 deep cycle is about 75 amp hours. With 2 such batteries and 50% depth of discharge (75 ah removed) you need about 90 amp hours to recharge them and they will not charge at 90 amps for 1 hour at 14.5 volts so the loss in the diode isolator is less.

The best guide to the care and feeding of lead acid batteries that I've ever come across was published by the US Bureau of Reclamation. It's a wealth of information.

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Joshua


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PostPosted: Fri Jun 08, 2018 7:08 pm 
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Supercharged
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Joined: Sun Nov 03, 2002 9:20 pm
Posts: 13008
Location: Fircrest, WA
Car Model: 76 D100
Joshie225 wrote:
The best guide to the care and feeding of lead acid batteries that I've ever come across was published by the US Bureau of Reclamation. It's a wealth of information.


Thanks, Josh! I will look that up.


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PostPosted: Sat Jun 09, 2018 6:35 am 
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TBI Slant 6

Joined: Sat Nov 12, 2011 10:04 am
Posts: 214
Location: Upper So. CA
Car Model: '65 Valiant 170 T5
Actually it isn't just those selling competing products. It's pretty everyone involved multiple battery bank storage systems. Look into off-grid solar, you won't see them. Look into deep water marine, you won't see them. Look into well built and equipped RV's, you won't see them.

And I think that you've missed a critical point, they do not immediately combine the batteries as soon as a charging source is applied. They allow the starting battery to be either fully re-charged first, or they allow enough time to elapse that a healthy starting battery should be approaching the Float stage before closing. This means that the alternator is working only one battery bank at a time, not both all of the time. Something that no diode isolator can do. You can justify them all you want. They're still junk leftover from the days when they were the best option.

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Thom



Cross-threaded is tighter than Lock-tite


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PostPosted: Sat Jun 09, 2018 8:27 am 
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Supercharged
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Joined: Thu Jan 27, 2005 8:32 pm
Posts: 7834
Location: Portland-ish
Car Model: Fiat 500e
ntsqd wrote:
Actually it isn't just those selling competing products. It's pretty everyone involved multiple battery bank storage systems. Look into off-grid solar, you won't see them. Look into deep water marine, you won't see them. Look into well built and equipped RV's, you won't see them.


All situations different than one or two extra batteries in a pickup or van.

ntsqd wrote:
And I think that you've missed a critical point, they do not immediately combine the batteries as soon as a charging source is applied. They allow the starting battery to be either fully re-charged first, or they allow enough time to elapse that a healthy starting battery should be approaching the Float stage before closing. This means that the alternator is working only one battery bank at a time, not both all of the time. Something that no diode isolator can do. You can justify them all you want. They're still junk leftover from the days when they were the best option.


I still disagree that diode isolators are junk. Most automotive and light truck applications have much more generating capacity than the batteries can accept. Switching/connecting charging capacity to the start battery and then to the house battery (or the opposite) is irrelevant when the charging system far exceeds the charge acceptance of the combined battery capacity. In fact doing so would waste the time needed to recharge the batteries.

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Joshua


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PostPosted: Sat Jun 09, 2018 4:27 pm 
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Supercharged

Joined: Thu May 12, 2005 11:50 pm
Posts: 6291
Location: So California
Car Model: 64 Plymouth Valiant
A diode can actually be beneficial to the life of a lead-acid battery.

Some alternator/regulators are set too high for the optimum voltage so that batteries recharge faster after a start.

Without going into the temp of the battery (optimum charge voltage varies a bit with temp and battery chemistry), you really shouldn't go above 14.4 Volts charging. (There is a tendency to start bubbling above 2.4v/cell) I like setting the regulator to 14.2.

The diode will drop the voltage below 14.4 if your regulator is a bit high...........

_________________
Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

8)


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