Question re Boost switch

H

heinz wittenbecher

New member
Mar 1, 1998
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Is it's normally off position with bottom or top of switch pushed in?

I.e. for regular running, what is the correct switch position?

Still doing a little on the road troubleshooting re batteries.

Thanks in advance ( TIA )

Heinz
on wireless in Sacramento.
 
Thanks,
That means I've been running with boost on for many miles and would also mean that the front battery (of the 2 in the front) is actually the boost battery and that running it like that screwed up the regular battery.

hmmm... sure gets confusing.

Guess I'll flip the switch once I have the battery replaced, followed by proper labelling :-)

Thanks again

Heinz

Gene: sorry for the direct mail earlier...and thanks for your reply. I'm still having problems getting used to the handheld's emai prog. It defaults to the original poster's address instead of the net.

- ----Original Message-----
>From: Ken & Virginia Fitzgerald
>To: gmcmotorhome
>Subject: Re: GMC: Question re Boost switch
>Type: AirMail
>Date: Tuesday, March 23, 1999 12:17 PM
>
>Heinz,
>On our 75 gb the top of the switch in is the regular running
>position,bottom in is boost with spring return to normal. Hope this
>helps.
>Ken Fitzgerald
>

>>
>> Is it's normally off position with bottom or top of switch pushed in?
>>
>> I.e. for regular running, what is the correct switch position?
>>
>> Still doing a little on the road troubleshooting re batteries.
>>
>> Thanks in advance ( TIA )
>>
>> Heinz
>> on wireless in Sacramento.
>
>
>
 
Heinz,
On our 75 gb the top of the switch in is the regular running
position,bottom in is boost with spring return to normal. Hope this
helps.
Ken Fitzgerald

>
> Is it's normally off position with bottom or top of switch pushed in?
>
> I.e. for regular running, what is the correct switch position?
>
> Still doing a little on the road troubleshooting re batteries.
>
> Thanks in advance ( TIA )
>
> Heinz
> on wireless in Sacramento.
 
Cheech... I did it again. Not checking the return address. Them durn computers ought to know better.

Sorry Zak.

- ----Original Message-----
From: heinz
To: Zachary Zehnacker
Subject: RE: RE: GMC: Re: Question re Boost switch
Date: Tuesday, March 23, 1999 6:44 PM

It still clicks the solenoid and removes power for the radio when in normal position. If I recall the schematic correctly the radio is actually powered from the booster batt, which is now disconnected in my case.

Perhaps it was changed by previous owner. As from my old electrician days down means off, it's been like that for a l o n g time. Oh well, never too late to set it right.

Thanks for the info

Heinz



>
>Unless you have changed your boost solenoid to a continuous duty one, your
>boost solenoid has probably burned out by now if you have left it in the
>boost position for a long period of time. The original style solenoids
>were not continuous duty rated and burned out quickly on our GMC if
>mistakenly left in the on position (probably why they switched to a spring
>return switch later on in GMC production). The easiest way to check it is
>to flip the switch while listening to the solenoid. If you don't here any
>noise when the switch is switched, the solenoid is probably junk. If you
>do here a noise from the solenoid, then it should be fine. Cinnabar (and I
>assume others) sells a continuous duty solenoid which we have left on for
>very long periods of time without problems. It is pretty expensive, but
>well worth it IMO to avoid having to change the original style solenoids
>every time you forget to return the switch back to the normal position.
>
>Zak
 
>experience!!!!!
>J & N Shannon '74 Canyonland in Ms. >>
>
>Heinz -- the above is good advice. Whenever you connect two batteries
>together in parallel, the alternator (or converter, or battery charger) can
>only charge them up to the capacity of the worst one. If one of the batteries
>has a short it can affect the other one. This is why a battery isolator is
>used from the alternator to two batteries.



I use a solenoid to get evey last ounce (volt/mini-volt) instead of the isolator. I changed after the 3rd isolator failed. Of course that was back when I relied on outside mtce :-)

Well, now that I have it all figured out, thanks to all the web'sters, I'm just going to put the switch in it's proper position once I have replaced all batteries and leave it alone. I can't recall having to actually use the boost more than a time or 2 and I may be better at remembering next time ( of course could be worse too :-)

Thanks again

Heinz
 
Heinz,
The off position is with the top pushed in on my '74'' Don't drive far
with it in the boost position or you may go dead . That's my
experience!!!!!
J & N Shannon '74 Canyonland in Ms.

> Is it's normally off position with bottom or top of switch pushed in?
>
> I.e. for regular running, what is the correct switch position?
>
> Still doing a little on the road troubleshooting re batteries.
>
> Thanks in advance ( TIA )
>
> Heinz
> on wireless in Sacramento.
 
Heinz,

Unless you have changed your boost solenoid to a continuous duty one, your
boost solenoid has probably burned out by now if you have left it in the
boost position for a long period of time. The original style solenoids
were not continuous duty rated and burned out quickly on our GMC if
mistakenly left in the on position (probably why they switched to a spring
return switch later on in GMC production). The easiest way to check it is
to flip the switch while listening to the solenoid. If you don't here any
noise when the switch is switched, the solenoid is probably junk. If you
do here a noise from the solenoid, then it should be fine. Cinnabar (and I
assume others) sells a continuous duty solenoid which we have left on for
very long periods of time without problems. It is pretty expensive, but
well worth it IMO to avoid having to change the original style solenoids
every time you forget to return the switch back to the normal position.

Zak

>
>Thanks,
>That means I've been running with boost on for many miles and would also
mean that the front battery (of the 2 in the front) is actually the boost
battery and that running it like that screwed up the regular battery.
>
>hmmm... sure gets confusing.
>
>Guess I'll flip the switch once I have the battery replaced, followed by
proper labelling :-)
>
>Thanks again
>
>Heinz
 
Top of sw pushed in means boost off, on my coach. Then when I want boost,
I push down to engange switch.
Al

> Is it's normally off position with bottom or top of switch pushed in?
>
> I.e. for regular running, what is the correct switch position?
>
> Still doing a little on the road troubleshooting re batteries.
>
> Thanks in advance ( TIA )
>
> Heinz
> on wireless in Sacramento.
 
Heinz, I don't think you hurt your batteries. The battery switch simply
connects the two battery systems. The purpose of the switch is to isolate
the "house" battery(s) from the "engine" battery, so that you don't
accidentally use up all of the batteries when stopped, and have no battery
to start the engine. Connecting them will not harm any of the batteries,
but if one of them has a bad cell, it could discharge all of the batteries
if they are connected with the switch.

Scott Shean
78 Royale
Baton Rouge, LA

> -----Original Message-----
> From: owner-gmcmotorhome
> [mailto:owner-gmcmotorhome]On Behalf Of Heinz
> Wittenbecher
> Sent: Tuesday, March 23, 1999 11:49 AM
> To: gmcmotorhome
> Subject: RE: GMC: Re: Question re Boost switch
>
>
>
> Thanks,
> That means I've been running with boost on for many miles and
> would also mean that the front battery (of the 2 in the front) is
> actually the boost battery and that running it like that screwed
> up the regular battery.
 
>Heinz, I don't think you hurt your batteries.

At least only the bad one :-)

I checked all 3 batteries and my other 2 are still good. The coach battery
is tired, but still checked good and the remaining front one took a charge
right down to almost zero on a battery charger.

Basically what I've been doing I guess is running with the reserve tank on
it seems.

'nother lesson learned... sure is nice to bounce things off around here :-)

The final proof of all ok will be Friday or Saturday... as I'll be 'on the
road again' heading for San Diego, National City actually.

Heinz
 
>Again, I strongly recommend using a temporary contact boost switch or
hanging
>a sign on the dash to remind you to turn the boost switch off after
starting,

Emery,

I don't think I'm going to have any problem remembering the switch as I've
been quite good at making sure it's in the down position thinking it meant
off :-)

In retrospect, had I had the switch correct I might've found out that the
one battery was going sooner.

Heinz
 
>
>No two batteries are identical in the condition or amount of charge it will
>take. If you don't use an isolator the vehicle alternator will only charge
>both batteries to the level that the weakest battery will take. So, you'll
>probably get out a lot less energy if you use constantly use the solenoid.
>
>Emery Stora

Arild replies:

There are ofter market alternators which have dual output regulators.
These are usually sold to marine and commercial operators who need
multiple battery banks. The dual output means each battery will get a full
charge.
Most of these regulators also have remote sensing so that each output is
tailored to the specific battery. The remote sensing allows for the
voltage drop across an isolation diode. Power 1, HEI, and Balmor, are
some of the makes of high output alternators I have seen in these
applications with special external regulators.

Cheers

Arild
 
Let me echo what emery says. You can damage the battery when one is not
functioning correctly. By isolating the two, you have protection.
Al

>
> isolator>>.
>
> No two batteries are identical in the condition or amount of charge it will
> take. If you don't use an isolator the vehicle alternator will only charge
> both batteries to the level that the weakest battery will take. So, you'll
> probably get out a lot less energy if you use constantly use the solenoid.
>
>
>
> There is a high probability that leaving the two batteries connected with the
> boost switch is the cause of failure of the isolators.
>
> Heinz - it is my feeling that the two batteries should only be connected
> together through the solenoid when your engine battery is dead or low and you
> need the boost to start the engine; or, your alternator is not charging or the
> engine battery is not taking a charge, etc., and you need it for emergency
> power to get home or to someplace where you can get service.
>
> Again, I strongly recommend using a temporary contact boost switch or hanging
> a sign on the dash to remind you to turn the boost switch off after starting,
> similar to what people do with their crank up TV antennas.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM
 
>If you don't use an isolator the vehicle alternator will only charge
>both batteries to the level that the weakest battery will take.

Actually this is not the case.

An alternator is a constant voltage source. It produces as much or as
little current as is required to keep the voltage up to where the regulator
is set. The actual voltage is a function of temperature. Lower temperature
results in higher voltage and vice-versa.

The only time the alternator produces less than full voltage is when the
load exceeds the capacity of the alternator. That typically happens when
you first begin charging. The after discharging for a while the batteries
will take all the amperage an alternator will produce for a brief period.
But, usually after a few minutes on the road, the alternator will be
producing full voltage.

If you have a new battery connected along with an older battery, both will
receive the full voltage produced by the alternator and both batteries will
be charged to their capacity. The newer battery will accept its full rated
charge, the older battery will have less capacity and thus will accept less
of a charge (fewer amps for fewer hours).

An exception is if a cell in one of the batteries is shorted. In that case,
the bad battery will take the bulk of the current and may prevent the
alternator from coming up to full voltage. But the problem will be pretty
obvious because the water in the remaining good cells (of the bad battery)
will quickly boil off.

So using a Solenoid relay to connect the two batteries will not result in
the batteries charging un-evenly.

Of course discharging is a whole other story...
But the Boost relay should never be left on during discharge.

>
>There is a high probability that leaving the two batteries
>connected with the boost switch is the cause of failure
>of the isolators.

This is a good possibility. The isolator is actually two diodes connected
back to back. The output of each diode is connected to each battery. The
diodes will let the current flow from the alternator to each battery. But
the diodes will not allow the current to flow back toward the alternator or
between the two batteries.

The problem with leaving the boost relay turned on is related to the nature
of diodes. Each diode has a unique "forward drop" voltage. That is the
voltage dropped across the diode when its turned on (when its conducting
current). The difference between diodes is quite small but it is large
enough that if you connect two diodes in parallel, only one will turn on!
That is what happens when the Boost relay is closed.

At the isolator input there are two diodes connected together (inside the
isolator). When the Boost relay is turned on it connects the output of each
of the diodes together (at the battery side of the isolator). The end
result is that only one of the two diodes will be conducting the full
current supplied by the alternator.

If the isolator is sized properly that should not be a problem. But its
hard to tell exactly what the numbers on an isolator really mean. I suspect
that a 100 amp isolator actually has two 50 amp diodes. It is assumed that
the load will be divided between the two outputs. For reliabilitys sake I
use an isolator that is rated for twice what the alternator can produce. An
oversize isolator will have bigger diodes and more cooling area. It will be
much less likely to fail. Especially if the boost switch is left on while
driving.

Dave
73 Sequoia
 
Need to explain a situation. I was looking at my digipanel and the light was on
showing a large chargins, and the gen light was lit. I didn't know what was
happening, and after a few hours of driving, I lost my alternator. When I got
home, I went to get it checked. It was the rear golf cart batteries that had
been overcharged by the old charging system ( the 40 lb brick converter).
Because the batteries had overcharged, the water had gone out of the batteries
and the alternator was attempting to charge the system. Since it couldn't bring
up the level of the rear batteries it crashed. Now I keep both batteries full
of water and watch when they appear to be charging incorrectly. ie more charge
going to one over the other. When the rv has been driven a while, there should
be no more going into the batteries if all is well.
Al

> > > >If you don't use an isolator the vehicle alternator will only charge
> >both batteries to the level that the weakest battery will take.
>
> Actually this is not the case.
>
> An alternator is a constant voltage source. It produces as much or as
> little current as is required to keep the voltage up to where the regulator
> is set. The actual voltage is a function of temperature. Lower temperature
> results in higher voltage and vice-versa.
>
> The only time the alternator produces less than full voltage is when the
> load exceeds the capacity of the alternator. That typically happens when
> you first begin charging. The after discharging for a while the batteries
> will take all the amperage an alternator will produce for a brief period.
> But, usually after a few minutes on the road, the alternator will be
> producing full voltage.
>
> If you have a new battery connected along with an older battery, both will
> receive the full voltage produced by the alternator and both batteries will
> be charged to their capacity. The newer battery will accept its full rated
> charge, the older battery will have less capacity and thus will accept less
> of a charge (fewer amps for fewer hours).
>
> An exception is if a cell in one of the batteries is shorted. In that case,
> the bad battery will take the bulk of the current and may prevent the
> alternator from coming up to full voltage. But the problem will be pretty
> obvious because the water in the remaining good cells (of the bad battery)
> will quickly boil off.
>
> So using a Solenoid relay to connect the two batteries will not result in
> the batteries charging un-evenly.
>
> Of course discharging is a whole other story...
> But the Boost relay should never be left on during discharge.
>
> >
> >There is a high probability that leaving the two batteries
> >connected with the boost switch is the cause of failure
> >of the isolators.
>
> This is a good possibility. The isolator is actually two diodes connected
> back to back. The output of each diode is connected to each battery. The
> diodes will let the current flow from the alternator to each battery. But
> the diodes will not allow the current to flow back toward the alternator or
> between the two batteries.
>
> The problem with leaving the boost relay turned on is related to the nature
> of diodes. Each diode has a unique "forward drop" voltage. That is the
> voltage dropped across the diode when its turned on (when its conducting
> current). The difference between diodes is quite small but it is large
> enough that if you connect two diodes in parallel, only one will turn on!
> That is what happens when the Boost relay is closed.
>
> At the isolator input there are two diodes connected together (inside the
> isolator). When the Boost relay is turned on it connects the output of each
> of the diodes together (at the battery side of the isolator). The end
> result is that only one of the two diodes will be conducting the full
> current supplied by the alternator.
>
> If the isolator is sized properly that should not be a problem. But its
> hard to tell exactly what the numbers on an isolator really mean. I suspect
> that a 100 amp isolator actually has two 50 amp diodes. It is assumed that
> the load will be divided between the two outputs. For reliabilitys sake I
> use an isolator that is rated for twice what the alternator can produce. An
> oversize isolator will have bigger diodes and more cooling area. It will be
> much less likely to fail. Especially if the boost switch is left on while
> driving.
>
> Dave
> 73 Sequoia
 
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