70 AMP BATTERY ISOLATOR

Anything electric, AC or DC

Postby Chuck Craven » Wed Jun 21, 2006 1:54 pm

Yes George I know that the car generators will not fully charge the batteries but with the diode type isolator. In my past systems I have found using pacific gravity readings, on the second battery it will charge to about 90% as long as there is no load on that battery and the battery is fairly new. When looking in to using an inverter for a camper, they seam to be about 75% to 85% efficient. So running basic 12 volt system with a 85% to 90% charged battery seems to me to be a good triad off. I don’t think that an AC, refrigerator, coffee maker and a microwave oven is really a basic system. I don’t have an Air Conditioner in my house don’t know why I need on in the camper. Never had one in the tent! :o
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Postby GeorgeTelford » Wed Jun 21, 2006 2:11 pm

Hi Chuck

Specific Gravity readings are as unreliable as Voltage readings as a guide to SOC, unless you have tested the specific gravity after charging with a good staged charger ie having a known good reference point.

BTW I am not saying your wrong above, in fact I rather hope you are right, as I guessed that about 90% would be the max if a diode was used with a standard alternator, I always like to confirm things acurately, with regards to the battery charging though, even on a basic system the more power you carry in the battery the longer you can boondock.

A modern invertor if sized right for the job will usually be 90%+ efficient.

I am not sure why you mentioned all that gear, its down to each individual what they want to take camping.

To the people questiong the wiring thickness, yes smaller wire will still pass some charge across, the voltage drop will increase though, lowering the charge efficiency even more.

Thats why I favour a smart regulator, as these increase the voltage to compensate for the wiring and diode losses, the staged charging is a big bonus and ensures you have a fully charged battery.
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Postby Leon » Wed Jun 21, 2006 3:22 pm

While a diode isolator will drop the voltage from the alternator by .7V, a way to make up for that is to hook the SENSE line from the alternator (not available on all units) to the car battery. If the alternator is putting out 13.7 v, after the isolator it will be 13v - the sense line will see that reading and cause the alternator to raise its output. This type of hookup will compensate for voltage losses in the charge wire since the sense line doesn't carry more current than what's required by the regulator to determine the battery voltage. Since the sense line is compensating for the drop going to the car battery, it will raise the output to the camper battery by the same amount. The drop in the wire going to the camper battery has a resistance that causes a drop, but as the battery charges, the drop becomes less as the current to the battery goes down. eventually, if given enough time, the camper battery will reach a full charge. As battery V goes up, the difference between alternator voltage and battery voltage goes down, as dV goes down, the current in the wire goes down, since the resistance is constant, the loss goes down. Battery voltage approaches alternator voltage (minus diode drop which was compensated for by the remote sense line)
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Postby GeorgeTelford » Wed Jun 21, 2006 4:24 pm

Hi Leon

Good point, if you have seperate sensing and can be done if you have a seperate sensing wire (not all alternators do on many you would have to strip the alternator and seperate it from the output internally)



The drop in the wire going to the camper battery has a resistance that causes a drop, but as the battery charges, the drop becomes less as the current to the battery goes down. eventually, if given enough time, the camper battery will reach a full charge. As battery V goes up, the difference between alternator voltage and battery voltage goes down, as dV goes down, the current in the wire goes down, since the resistance is constant, the loss goes down. Battery voltage approaches alternator voltage (minus diode drop which was compensated for by the remote


The voltage drop in the wire will always be there even when the ampage drops resistance is resistance. Later you say that the resistance is constant? in the wire it is, but overall the resistance of the battery changes internally as the state of charge changes, this is how the so called "automatic" chargers alter their output, the battery resistance !!


Leon, do you believe that a standard alternator fully charges the starter battery? Its just from what you write you apear to believe this.
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Postby Chuck Craven » Wed Jun 21, 2006 4:42 pm

Yes that is how I do it. Do a full slow charge, measure the battery voltage after sitting for 24 hours. Then measure each cell’s voltage with cadmium probes then I do the specific gravity of each cell. That is my reference. If a battery is going to go bad it will with in six months. I have had bad batteries replaced with out being charged the prorating with that data in hand. If you can prove the battery is defective you can get a full replacement at no charge. :twisted:
But it is nice to see how a battery will age and do a graph to see the difference between expensive and cheep batteries. If one takes care of their batteries the cheep batteries can last all most as long as the expensive ones. It’s just the cheep ones can’t take much abuse before they go bad.

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Postby PaulC » Wed Jun 21, 2006 5:17 pm

madjack wrote:...I read the manual also and here is my problem...I know that you can run a 10ga wire from the alternator to the camper battery(did it for years onna 22'er I had). I had no isolator but simply unhooked the wire when stopped so...why do I want to use somehing that requires that I run a full sized battery cable all the way to the camper...isn't there some kind of isolator that I can put in the camper and just run that same 10 ga wire??? I don't want the expense of a full sized battery cable(20/30'worth) and its attendant routing problems...there has to be a simpler way such as I did on my old 22'camper...
madjack 8)


Hi Madjack, if you run that 10g via a relay you will have an automatic isolating switch. Once you turn the vehicle off the relay will cut out thus isolating the trailer battery from the car circuit. The only problem I can see is that you will have a live wire back to the relay(I think). If you can fit the relay to the rear of the tow vehicle you will shorten this. This is the set up I had on my old tipper trailer and, as I said earlier, it worked for me.
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Postby Chuck Craven » Wed Jun 21, 2006 5:22 pm

Where I like to go camping I would have to have a 100000 + foot extension cored to use a staged charger or an inverter. So I need another way to charge a battery. The forest rangers do not like generators. And with all the trees in the way, solar is not a viable way to charge. The only thing lift is to use two batteries and the car as the charging source.
Then keep the current draw down to a minimum. I will still have a staged charger in the tear for when it is stored at home. When camping at a campground I will use a 13.5 v power supply to power things instead of the batteries, off the shore power. I know down in the southern states AC is a necessity. Some people think when camping one must have all the comforts of home. Not me! I just want to be somewhat dry and comfortable. Also don’t want to sleep on the ground anymore. Other than that I will put-up with just about anything nature will through at me accept flood, fire and snow.

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Postby PaulC » Wed Jun 21, 2006 5:26 pm

GeorgeTelford wrote:Hi Paul

I don't need to know! I use the Henry Ford principle in cases like this


So you dont know?

Nothing at all wrong with keeping it simple, as long as simple works well.


George, I did'nt say I don't know I said I don't need to know. I have a very close friend who owns an Auto Electrical business and he has supplied me with all the info I require. He also has the uncanny knack of being able to explain principles in layman terms, so that even a "dummy" like me can understand.

I like your take on the smart regulator, I think I will be asking a couple of questions today on that one.

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Postby GeorgeTelford » Wed Jun 21, 2006 7:19 pm

Hi Chuck

I think you are misreading something somewhere.

The smart regulator turns the alternator into a staged charger, which then fully charges the battery. No need for 100,000 ft extension cables. The great effect is that compared to normal charging you will get twice as much from a battery (saves carrying 2 if you charge 1 properly)

Hi Paul

Well theres the rub on this kinda thing, If I say do it this way, then I am being arrogant and then asked why? If I then explain it simply, you always get someone who as heard/knows different, so then it gets a little technical and then people get left behind.

If you look back at any electrical subject, I have explained it simply at first.

The problem with asking auto electricians is that they think that an alternator is a battery charger and also think it fully charges a battery, unfortunately that is wrong on both counts.
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Postby PaulC » Wed Jun 21, 2006 8:04 pm

George, No disrespect intended here but I think I'll stick with over 50 years experience in an industry that is continually evolving. The boys at Hampstead Auto Electrical are well known in little old Adelaide as the people to go to when the others can't sort it out. As far as 12volt goes in this town they have no peers.

Quote:"the problem with asking auto electricians is that they think that an alternator is a battery charger and also think it fully charges a battery, unfortunately that is wrong on both counts"
We were only talking about that last week, at the auto electricians, as I had a starting problem with my car. They informed me that the main reason car batteries eventually fail, even if carefully maintained with correct fluid levels, is because an alternator is incapable of fully charging said battery. They said that the only way to keep a battery at it's peak was to use one of those battery chargers that you continually refer to, on a regular basis. Even by doing this they said that the battery will eventually fail anyway, but it would take longer.
Cheers George and thanks for the info on the smart regulator'
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Postby Chuck Craven » Wed Jun 21, 2006 8:07 pm

My 2005 Toyota has a smart regulator all ready built in. Talked to them about a battery isolator and it will work but it will still mainly charge the starting battery. The second battery will charge but will take longer to charge do to the regulator think it is a load. Also that battery will only charge to about 90% max as the regulator will not let the batteries over charge no mater what the load is. As for after market regulators, they will not work with the Toyota system, its regulator is connected to the main computer, which monitors all the loads. I am not to worried about having two batteries as the one in the truck can be used to jump start it in the winter if it gets to cold. Have seen –30 F here.
In Wisconsin one never knows what the weather will be like from day to day.
I will be using the second battery for my radios when not camping, so it will be in use.
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Postby Leon » Wed Jun 21, 2006 11:33 pm

GeorgeTelford wrote:The voltage drop in the wire will always be there even when the ampage drops resistance is resistance. Later you say that the resistance is constant? in the wire it is, but overall the resistance of the battery changes internally as the state of charge changes, this is how the so called "automatic" chargers alter their output, the battery resistance !!

Yes, I was talking about the resistance of the wire. When the amperage drops, and resistance in the wire stays the same, the voltage drop also reduces.
E=IxR E is directly proportional to I.

GeorgeTelford wrote:Leon, do you believe that a standard alternator fully charges the starter battery? Its just from what you write you apear to believe this.

I'm talking about charging as practical as can be achieved with an automotive system. The point I was making is that an isolator, when properly hooked up, will perform as well as the stock charge system of a vehicle, and the charge line to the camper doesn't have to be a 1/0 wire for it to work. Many people put diode isolators in without looking at the sense line (the computerized cars have them, too - you just have to know where to look) and therefore have low voltage going to their vehicle. In street rod construction the trend is to go to one-wire alternators for a clean installation, but doing so causes voltage problems that can be overcome by having a sense wire wired to the proper junction piont. My '03 computerized chevy has a sense line, but it is burried in the harness and connects to a junction that you wouldn't be able to see without taking harness appart.
The advantage of a Diode isolator over a relay is that a camper battery that has been hooked up to a charger at a campsite won't feed back to a starter battery that has been in a car for 5 years and has just started the car. The two batteries are very different construction, and diode isolation is a little safer way of "connecting" them together. The diode won't arc and pit the contacts and are a maintenance free device.
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Postby GeorgeTelford » Thu Jun 22, 2006 3:53 am

Hi Chuck

The Toyota regulator is not a smart regulator (as in staged charger)

Sterling have developed a Special Battery to battery charger to overcome the fact that some manufacturers are incorporating the regulator into the engine management systems, This takes power from the starter battery and converts it to staged charging for the leisure battery('s) Obviously the starter battery does not benefit from the staged charging

http://www.sterling-power.com/htm/btb.htm

These are more expensive than a standard smart regulator, but have the advantage of being easier to fit and hence easier to swap into your next vehicle.

Starter and leisure batteries are supposed to have different constructions, in reality there is little if any difference, My local camper shop had their van battery fail, so they stuck a leisure battery in to get them going, several years later it was still going strong.

Talked to them about a battery isolator and it will work but it will still mainly charge the starting battery. The second battery will charge but will take longer to charge do to the regulator think it is a load.


Classic example of vehicle electricians talking rot, it is "semi true" but as nothing to do with the regulator "thinking"

Consider

Starter battery only ever expend's a fraction of an AmpHour starting the vehicle and then is constantly fed while the engine is running, ie if the system stays at 65 % charged it will hardly move from 65 % charged even while starting.

A leisure battery however is often much lower than 65 % and much higher (if its charged via a staged charger it can be 100% charged)

This is reason one why it takes longer to charge (if its at one of the Lower points)

Secondly the leisure battery is subject to voltage drop, from the Diode isolator and the wire (second batteries are usually much further away)



Hi Paul

I am impressed with your auto electricians, you will be amazed to know that they are the first and only auto-electricians in the world (so far) who have not got that wrong...

Hi Leon

Reduces by a fraction but there is still voltage drop and enough to ruin charging...

I understand your sense line point and if this is done a much better charge can be achieved with a diode isolater.

Note of caution, The reason they moved the sensing wire to internal on the alternator (or short external run to the output 1 or 2 inches away) is that if this wire breaks, the alternator goes into balls out mode and destroys itself (and occasionally some of the vehicle electrics !) so do be extremelycareful about anything you do with this wire.

I have to disagree about the "most practical can be achieved" practical is a relative word adding a smart regulator or B2Battery charger is easily achieved, with much better results.
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Postby PaulC » Thu Jun 22, 2006 4:10 am

GeorgeTelford wrote:



Hi Paul

I am impressed with your auto electricians, you will be amazed to know that they are the first and only auto-electricians in the world (so far) who have not got that wrong...
.


Well George,I'm doubly impressed to think that you have canvassed most of the auto electricians in the world to be able to make that statement. :lol:

Cheers
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Postby GeorgeTelford » Thu Jun 22, 2006 4:24 am

Hi Paul

Now thats being ridiculous and just a little rude, taking the mickey out of a badly worded statement, next you will be attacking peoples spelling just to score a point.

But getting involved with these discussions on many different forums and in real life as led me into contact with many many auto-electricians, both directly and through other posters.

So the true statement is that of the many auto electricians I have had contact with, none (except yours) have ever got that right.
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