isolated battery-NEED pos,neg,earth isolated too!

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Old 05-01-16, 02:23 AM
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isolated battery-NEED pos,neg,earth isolated too!

I have a van with a fixed battery and a leisure battery separate from the car but connected to the alternator. Essentially recharging it only.
I have found that the isolated battery is giving current but my electrics are not functioning - UNTIL the earth value is made. eg. by not connecting the earth (not the neg) a difference to the neg isn't attained and the switch's wont light up etc.
Instead I need to make the earth separate from the vehicle earth because I don`t want to connect the two battery's together under any circumstances.
How do I go about making a earthing pole on the van? Put a rod with all things connected and attach it to the mud flap?
 
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Old 05-01-16, 03:19 AM
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I can't make sense out of what you are sating. All appliances (lights, plugs etc.) will have to have a ground wire going back to battery to work and be separate from van.
 
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Old 05-01-16, 04:30 AM
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I would isolate the separate battery, so it will only charge and not affect the rest of the circuits. THEN you could start your diagnosis.
 
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Old 05-01-16, 05:05 AM
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Welcome to our forums!

Normally on a negative ground vehicle with multiple batteries, the negative on all batteries is connected to ground.
Switching and isolation is done on the positive side only.

How is the second battery connected to the alternator?..........Is it connected to a battery isolator?
A pic of the components and connections might help us see what you do.
 
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Old 05-01-16, 04:18 PM
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I need to make the earth separate from the vehicle earth
I don't understand why you would need to do that. You only have to separate one pole, which usually is positive.

What is normally done is adding a diode (high current diode) to positive side so that current flows only one direction. This way you charge 2nd battery from the alternator, but won't drain back.
This diode is sometimes called battery isolator, but technically it is not really isolated.

Negative side is connected together, usually do the body of the vehicle. (Although, I'd still recommend ground wire all the way to 1st battery, or engine block)

There is no reason for your electronics to not function, unless it is wired incorrectly.
 
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Old 05-02-16, 12:50 AM
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OK, thank-you for so many reply's

first off (and not getting confusing) the attempt was made to parallel connect them. What happened cost $1000 damage to my starter, coil and hall sender in the VW, over heated the coil (60+deg red hot)sending the excess to the rest, so I have to rule out connecting to these components something to do with (1) recommended battery for starting the vehicle or maybe not a modern set up.(`97 model)- anyway mainly via the neg cables to the motor and chassis should be the only go around.

yes the neg and pos are connected but some switches need an earth to light up the diodes,amps,lights all relying on the EARTH to operate hence they dont ....
Ill get some pics but its just a cable from the alt peg to a main 12v on/off switch to a + bar with applications running off it then from the switch to the battery. a neg cable runs off it to a - bar.

The main problem is that the cable to the alternator from the 1st batt, coil, starter solenoid is LIVE when the cars off...I didn't expect this.(I contemplated putting the switch here but the van needs its power on all the time).

The things running off this 2nd battery are separate things to the main vehicles electrical system so there is no cross wiring. this being connecting to the chassis or similar will complete the circuit and re-occur the meltdown! so my Q is can I run a lead off the mud flap with a metal pipe on it for an earth????

hope that clears things up.
 
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Old 05-02-16, 01:16 AM
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I'm not quite sure where you are getting the mudflap idea for ground.

The two batteries being charged from a common source.... the vehicle alternator..... MUST share a common chassis ground.

The second battery needs a continuous duty relay (labeled R in my diagram) that closes when the key is in the run position. When the key is off..... the relay is open and the battery is isolated from the alternator and the vehicle battery.

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Old 05-02-16, 06:11 AM
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Ha, I assumed since the chassis couldn't be earthed then its the only option left...
So I have to get another component which will separate ... like the VICTRON Cyrix-ct Battery Isolator/Combiner 12/24V - 120A ???
I didn't know these things existed, especially when making the $100 worth of cabling, switch and labour !!
As long as the current doesn't BACK-FLOW then we have found a solution. any suggestions which diode isolator is better and I can use the chassis again-solving a large problem.
 
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Old 05-02-16, 09:46 AM
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I do not use the diode type isolators as they introduce unwanted voltage drop into the system.

I specifically use Cole-Hersee 12vdc continuous duty solenoids. They look like starting solenoids but starting solenoids are only rated for short duration uses.

Solenoid information Continuous Duty SPST Series - High Current Relays - Littelfuse

They are sometimes called golf cart relays too. Here's a few choices from amazon.
amazon - Continuous Duty Solenoid 80AMP 12V: Automotive


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Last edited by PJmax; 05-03-16 at 09:14 AM. Reason: major typo
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Old 05-03-16, 12:31 AM
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GEE it looks tough....
"..Diodes have a small voltage drop. Relays do not. Unless the alternator's voltage regulator monitors the voltage, ideally, at the battery, or not quite as ideally, downstream of the diode isolator the batteries will never see a full charge.

There are constant duty solenoids (BIG relays) and there are automatic relays. The constant duty solenoids pre-date the diode isolators and are still a better option though the automatic relays are better still. I don't buy the marketing for those semi-automatic relays that have a remote switch. I prefer to use a robust marine battery switch for those needs.

The Automatic Charge Relays and Voltage Sensing Relays (different names for essentially the same product) don't have any voltage drop and do something that the diodes can't. They allow the alt. to first bring the starting battery back up to full charge before connecting the 'house' battery to charge it. Diodes force the alt. to charge both at the same time, even when they are not at the same state of charge. Relays also disconnect when the charge voltage drops, be that because you turned the engine off or there was some large draw on the starting battery.

There are two versions of the ACR/VSR's, single sensing and dual sensing. Single sense relays only sense the voltage from one side. Dual sensing look at both sides. With a single sense relay set up to allow the alt. to charge the 'house' battery last it will never turn on when the solar panel has charged the 'house' battery. A dual sense relay will allow solar or any other charge system connected to the house battery to charge the starting battery once the house battery is fully charged.

Can buy an ACR/VSR in combination with a marine battery switch so that you can force the two batteries to be paralleled or even switch the starting chores to the house battery if need be. This combo is what I would buy were I going to do it again...."

this is from another old forum, but the topic is certainly bigger than i expected.
I have a lot more reading to do...
 
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Old 05-03-16, 09:33 AM
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I've driven vans for thirty years. Each one had multiple batteries wired with a continuous duty solenoid. I've had customers with fleets of service vehicles that also used them with excellent results.
 
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Old 05-03-16, 11:33 PM
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will this do?
Continuous Duty Solenoid 12 Volt 90 AMP Normally Open OEX ACX3304 12V Solenoid | eBay
do i get one with the same amps as my alt as above?
What is its set up, obviously now I can use the van chassis again but is it grounded to the van and runs the + only, then I have the switch.
 
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Old 05-04-16, 12:03 AM
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The coil of the relay is wired to the positive of an accessory circuit that is only on when the ignition switch is on and ground. That way when the ignition is turned off the relay is open isolating the auxiliary battery from the truck battery.

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Old 05-04-16, 04:48 AM
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you do nice pictures, I have always wanted to look this professional on the net.

I Still Need To Know What Voltage to get, Id assume the same but Im no good with calculating electrical stuff.
Thanks for your help with the thin ,getting around the earthing problem was looking hard, mainly to get an isolated earth peg it has to be a certain amount of thickness..????
 
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Old 05-04-16, 08:06 AM
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...i mean the amperage...not volts.
 
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Old 05-04-16, 10:02 AM
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That solenoid will work fine for you. A little pricey but your choices are probably limited there.

Ray's diagram is correct but here is one BIG piece of information.... the ignition source to the solenoid must not be active in start position. You DO NOT want the vehicle starting off of both batteries.

If you don't understand this.... ask.
 
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Old 05-04-16, 04:37 PM
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Thanks, all of it is information. I read on the cole hersee FAQ site about the connection to the ignition (and many other things) but I have the heavy duty switch on the cable BEFORE i put the solenoid so it will have a different ON source.
OK I`m off to buy one.
Thanks again.
The reason for your big information, wouldn't happen to be about it being `normally open` or closed would it? There are ones that are open (meaning closed circuit at start) and others mentioned as closed but I`m not sure if its is literal. Is there a difference in the making of them, some open others closed.
strange if it is.
 

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Old 05-04-16, 05:56 PM
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Is there a difference in the making of them, some open others closed.
strange if it is.
You only want it closed when the ignition switch is on with the engine running. That way the two batteries are never connected when the ignition switch is off.
I have the heavy duty switch on the cable BEFORE i put the solenoid so it will have a different ON source.
What is the "it" that will have a different on? Are you saying you are not going to control the solenoid with the ignition switch? That would be a mistake. It defeats the main purpose of the isolator setup to prevent accidental connection of the two batteries when the engine is off or starting. If you are going to do it as described there is no reason for an additional switch.

If you may occasionally want to have the auxiliary battery disconnected when the engine is running you can put a switch on the wire to the coil but then you open yourself again to accidentally not charging the auxiliary battery.

Heavy duty switch is a meaningless term. How many amps DC is it rated for.
 

Last edited by ray2047; 05-04-16 at 06:15 PM.
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Old 05-05-16, 01:56 AM
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So......the solenoid you suggest is a closed at ignition? "...Contacts: Normally Open (NO)..." their description is confusing.
Yes your right, the solenoid will do IT`s job ( basically the whole system to recharge the second battery is IT) but the main control of when IT-the recharging system- is used will be the 24 volt (capable) On/Off switch used in this case on 12 volt (a boat shop sold the complete set with cables tailored and all...) THEN the solenoid leading to all the other applications-bars,relays,fuses,switches and spotlights ETC. in their own element. Really when the battery is fully charged I can switch it off and use the alternator just on the usual van requirements without busting my sides to get both filled up all the time- maybe overworking the alt. (or maybe not!?)
Anyway when the spotlights get going they eat up the power so I guess it makes it easy to direct the flow one side or the other for the alternator usage.

Ray's diagram is correct but here is one BIG piece of information.... the ignition source to the solenoid must not be active in start position. You DO NOT want the vehicle starting off of both batteries.
If my ideas not good then why wouldn't to solenoid work? Should I safe guard its usage just in case?
 
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Old 05-05-16, 08:53 AM
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I cant see the problem...as long as the solenoid is treated to current at the ignition pole, then the switch just acts as `delayed ignition ON event`. I get 2 bangs for my buck AND it still works the same as it is supposed to!
YES?!

(im brilliant)
 
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Old 05-05-16, 04:30 PM
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Yes... the solenoid is normally open (NO) and it closes when you supply it with 12vdc.

From what I understand... you want to put a switch in the + line to the solenoid control coil so that it doesn't always close when the ignition is on. That's fine.

Yes... the second battery in charging will be using power from the alternator. It will shorten the alternator life somewhat. In my opinion.... it's better to keep the battery topped off then to allow it to discharge and put a heavier load on the alternator.

Just to reinforce a point I made previously. It is important to connect to the proper ignition wire. There are two ignition sources.... one becomes live as soon as the key is turned on and stays live the entire time the key is on.... even when vehicle is starting.

The second ignition line turns off when the key is turned to start. That usually includes things like heater blower motor and windshield wipers. This is the line you want.
 
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Old 05-05-16, 11:44 PM
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these sound interesting, do they do the same job?

ITEM DESCRIPTION:
Voltage Sensitive Relay 12V 140Amp Narva 61092BL

Narva’s new Voltage Sensitive Relays have been specifically designed for a wide variety of 12V & 24V applications. The VSR units sense the input voltage generated and automatically connect/ disconnect the appliance or circuit at pre-set voltages, eliminating the possibility of discharging the primary starting battery.
Constructed with a weatherproof body (IP65) and durable silver tipped contacts, the VSR units also feature surge protection and a L.E.D indicator designed to alert the user when the unit is engaged. Narva’s VSR units are ideal for dual battery set-ups as they enable two batteries to be charged at the same time and then isolates the batteries from each other when the vehicle is turned off, ensuring your starting battery is always charged & ready to go.


• Surge protection • Durable silver tipped contacts • L.E.D indicator •
P/No: 61092BL Cut-in: 13.3V Cut-out: 12.7V (5 second delay) 160A at 12V for 60 seconds 140A at 12V continuous load maximum
P/No. 61093BL Cut-in: 26.8V Cut-out: 25.6V (5 second delay) 160A at 24V for 60 seconds 140A at 24V continuos load maximum
 
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Old 05-06-16, 12:33 AM
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Yes.... although I have never heard of those..... they do the same job just a little differently.
 
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Old 05-06-16, 05:20 AM
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Its time to buy something and end the thread......
which one would you recommend please, and I will get that one.
(because I would choose a relay)
 
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Old 05-06-16, 11:05 AM
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Umm...just one final Q, the earth from the solenoid-IS THAT ONLY FOR a safety precaution to earth the unit just in case OR is it for the units operation in recharging with the positive connected.?
I felt comfortable with it until I realized that it is not to contact the chassis with the positive combined....any ideas?
The coil of the relay is wired to the positive of an accessory circuit that is only on when the ignition switch is on and ground. That way when the ignition is turned off the relay is open isolating the auxiliary battery from the truck battery.
 
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Old 05-06-16, 01:48 PM
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The solenoid contains an electromagnet, the coil. To work it requires a positive and a negative wire. Ground is your negative.

Terminology: There is no earth. there is chassis ground which uses the vehicles metal frame as the connection to the negative side of the battery for any electric devices.
 
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Old 05-06-16, 05:24 PM
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Ray's diagram back in post 13 illustrates the - or ground connection to the coil.
The metal housing of the relay does not need to be attached to metal or be grounded.
 
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Old 05-06-16, 06:28 PM
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However fastening the solenoid's metal housing to the metal chassis does no harm.
 
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Old 05-07-16, 05:57 AM
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sorry my misquote, I meant neg not earthed.

This is no good now, I just assumed that the positive was the only active capable part to the whole solenoid. That the working solenoid was able to `RESIST (its the best word I have...) all the working elements` in isolating the battery pos and neg together AND do the ON/OFF thing as well, but if it uses the same principle then it will conduct the current exactly the same as joining the two together.

you've said it is grounded but really it is the neg pole.....isn't it?
I can accept grounded but not the pole neg thing

mind you i am illiterate in electrics..

(oops more posts)
so the word is grounded not neg earthed. OOHHH !!(thanks PJmax) the neg is from the leisure battery NEG , like I connect it to the neg terminal. (very deceiving to say `chassis`, I should have realized.)
 

Last edited by custum; 05-07-16 at 06:03 AM. Reason: oops
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Old 05-07-16, 10:49 AM
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very deceiving to say `chassis`, I should have realized
Why is it deceiving?
the neg is from the leisure battery
Yes, but it is also the negative from the truck battery and in the case of the solenoid coil the voltage return is through the metal chassis to the truck battery not the auxiliary battery.

I strongly suggest you have an automotive electrical shop connect this up for you. You still seem confused.

chas·sis
ˈCHasē,ˈSHasē/
noun
noun: chassis; plural noun: chassis

the base frame of a motor vehicle or other wheeled conveyance.
synonyms: framework, frame, structure, substructure, shell, casing
"the chassis of the car is in mint condition"
the outer structural framework of a piece of audio, radio, or computer equipment.
synonyms: framework, frame, structure, substructure, shell, casing
 
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Old 05-07-16, 10:12 PM
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Ha,ha just jokes.
That works - from the leisure battery, its running off the neg from the destination, shouldn't matter where it gets its grounding from. (I mean really it would only complete the circuit the other way whats the difference) and the metal case isn't a problem. Completely reversed the situation from dont touch to `all access`
yes a shop might be the go.(although that`s were I went before and they didn't put in a solenoid?!) I`m just confused beyond `conducting` electricity that`s just me.
Thanks anyway.
 
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Old 05-07-16, 10:24 PM
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That`s positively only positive alternator output-with no connecting neg connection.
Right?
 
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Old 05-07-16, 10:40 PM
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An alternator has both a positive and negative output*. Any DC device needs both negative and positive. A battery can't be charged without both a positive and a negative.

*Tech note: Alternators produce AC not DC. It produces 3 phase AC voltage which is converted to DC by rectifiers.
 
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Old 05-08-16, 05:57 AM
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??? ????
I`ll have to check on that?
???? ???
noticed only 1 red wire.
oh.
 
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Old 05-08-16, 12:18 PM
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The negative of the alternator may be connected internally to the metal housing of the alternator the housing is then fastened to the metal chassis of the vehicle so no second wire is needed. It is not uncommon for a device with a metal housing to have just one wire since the housing bolted to the the metal frame is the path for negative.

Notice the grounding in the diagram below of a typical 3 phase car alternator.

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Old 05-09-16, 04:42 AM
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....well the neg is all around-inescapable.Making an earth point is harder now.
anyway Ive ordered one in and fix it in this week.
 
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Old 05-09-16, 09:10 AM
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just as a matter of consequence, would you know how a parallel battery system could place so much current to overload components-like it did with my starter etc. which caused all this. The `Right` battery recommended is in then another (similar) was connected. I cant see why unless components rely on the very exact output of just one...????
 
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Old 05-09-16, 09:20 AM
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Your last question makes very little sense.

Like I mentioned previously..... the additional load of a second battery will shorten the alternator life.
 
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Old 05-09-16, 11:24 PM
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..two battery's in parallel blew up the starting components, over heated the coil..etc.

I cant understand how it can-has same volts, is more current responsible?? simple (if you know how a cars components work I guess)

Have you ever heard of this happening elsewhere?
I may just have faulty parts...OR HAD them.
 
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Old 05-10-16, 12:38 AM
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two battery's in parallel blew up the starting components, over heated the coil..etc.
Two batteries wouldn't. This is proved every time some one uses one cars battery to jump another cars battery. The battery does not "pump" amps into devices. The device draws just the amps it needs.

If however you connected the two batteries in series that would doubel the voltage and burn out a lot of equipment.

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