Fmtv no more dual voltage

Ronmar

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Lot of details... My plan when the dual volt alt or reg fails is to go with a 24V alt. Get the 12V out of the battery bank and use a 24-12 power supply. I have identified a 70A unit with an adjustable output(10.5-15V) and a 13V cuttoff/dropout voltage. The beauty of this is if the power supply takes a dump, you can still tap 12V out of the bank to get you home/until a replacement power supply is sourced...
 

Ohiobenz

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Has anyone pursued this to a completion?
I am in the process on my 98 A0 M1079 and mainly have some wiring questions.
The new alternator is a 200A 24v internally regulated unit.
A Bussman Equalizer Replaces the polarity unit, with 12v coming off the lug on the Bussman.

I'm assuming that the 12v coming off the polarity unit goes into the cab fuse panel and powers the 12v side????

I'm concerned with all the extra wires that were on the dual voltage Niehoff and the external regulator.

Any advice and maybe screenshots of the TM electrical schematic pages would be helpful in identifying my direction.

Thanks!
 

Ronmar

Well-known member
699
282
63
Location
Port angeles wa
Has anyone pursued this to a completion?
I am in the process on my 98 A0 M1079 and mainly have some wiring questions.
The new alternator is a 200A 24v internally regulated unit.
A Bussman Equalizer Replaces the polarity unit, with 12v coming off the lug on the Bussman.

I'm assuming that the 12v coming off the polarity unit goes into the cab fuse panel and powers the 12v side????

I'm concerned with all the extra wires that were on the dual voltage Niehoff and the external regulator.

Any advice and maybe screenshots of the TM electrical schematic pages would be helpful in identifying my direction.

Thanks!
Yes the 12v coming off of the polarity box 12v output terminal feeds the 12v lug in the power panel, as does the 24v coming off of the polarity box 24v output terminal.

You can remove the 12v cable coming from the alt and the 12v cable coming from the battery. They are connected to the same 12v input terminal On the polarity box.

The 24v line from the battery, from the alt and from the Power panel can all be connected to the 24v terminal on the bussman. The 12v line to the power panel can get connected to the 12v output terminal on the bussman and of course ground gets connected to ground...
 

Ohiobenz

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The Bussman schematic still shows a 12v tap coming from the battery. I was wondering about the necessity of that since it is also a converter.

FB_IMG_1595551240951.jpg

The right side schematic is from the Bussman. The left is from the Smart Isolator. I am not doing any disconnect switches on the Bussman side, and using marine circuit breakers instead of fuses.
 

Ohiobenz

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Yes the 12v coming off of the polarity box 12v output terminal feeds the 12v lug in the power panel, as does the 24v coming off of the polarity box 24v output terminal.

You can remove the 12v cable coming from the alt and the 12v cable coming from the battery. They are connected to the same 12v input terminal On the polarity box.

The 24v line from the battery, from the alt and from the Power panel can all be connected to the 24v terminal on the bussman. The 12v line to the power panel can get connected to the 12v output terminal on the bussman and of course ground gets connected to ground...
Here is the Bussman schematic as a "converter"

Screenshot_20200726-110429_Drive.jpg

What it doesn't state in their data sheets is whether the unit still works as an equalizer when wired as a "converter". I'm inclined to run the extra cable as in the equalizer circuit, it's technically there anyway.
I'll be using these terminal blocks on the other side of the Bussman bracket.
Screenshot_20200723-102320_Chrome.jpg
 

Ronmar

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In the first schematic the switched connection to 12v Could basically be used for emergencies, like in the event the converter should fail. If it fails, you can still easily pull the needed 12v out of the middle of the battery string to keep you going till new parts are sourced...

The installation manual states the 12v output is always 1/2 of the 24v input(Its always an equalizer)... However, If you are not pulling any load out of the middle of the 24v battery String, there is no need to connect the equalizer to the middle of the battery String. Just like a 12v battery doesnt have an equalization connection in the middle, Two 12v batteries in series(With a proper connection) will behave as a single 24v battery if left alone:)

like in the second drawing, the converter will act as a standalone power supply to feed the 12v Loads. The converter will always pull a little 24v idle current to keep 12v available on the 12v output terminal Even with no load, I am not sure how much current this is, so a disconnect on the 24v leg is not a bad idea if the truck sets for longer periods.
 
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chucky

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Or just put a Vanner on your batteries wired in 24v the Vanner breaks the 12v out you need and balances the batteries Prevost has been doing it this way for 30 yrs i know of and its super simple.
 

coachgeo

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The Bussman schematic still shows a 12v tap coming from the battery. I was wondering about the necessity of that since it is also a converter.

View attachment 807149

The right side schematic is from the Bussman. The left is from the Smart Isolator. I am not doing any disconnect switches on the Bussman side, and using marine circuit breakers instead of fuses.
interesting that the bussman can also act like a 24v to 12v converter/(charger? ) what is the amp output of the 12v off the
? and does it regulate in anyway???

what is confusing to my feeble brain is the 12v connection to the bussman..... seems it is input and output.
 
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chucky

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what is Provost?
Prevost bus they use 4 12 v batteries wired 24v most of the bus is 24 v but some 12v stuff and its just run a cable from hot side 24 into vanner it gives you 12v out the other side is the simplistic version of it
 

Ronmar

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The 12v on the bussman is always an output. It is exactly half of whatever voltage is applied to the 24v terminal. If the 12v terminal is connected to the 12v in the middle of the 24v source Battery string, it provides up to 100A of 12v to balance whatever load is being drawn from the middle of the string, all the while striving to maintain the voltage at that point as exactly half of whatever the total 24v string Voltage is at...

As a converter that 12v terminal provides up to 100A of exactly half of whatever is applied to the 24v terminals...
 

coachgeo

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The 12v on the bussman is always an output. It is exactly half of whatever voltage is applied to the 24v terminal. If the 12v terminal is connected to the 12v in the middle of the 24v source Battery string, it provides up to 100A of 12v to balance whatever load is being drawn from the middle of the string, all the while striving to maintain the voltage at that point as exactly half of whatever the total 24v string Voltage is at...

As a converter that 12v terminal provides up to 100A of exactly half of whatever is applied to the 24v terminals...
1. so sounds like this bussman unit "balances" things on the output side of itself you could say with the input side being some form of a charger. So is what keeps the batteries balanced in situation where 12v is being drawn from 24v bank.... is that the battery/(ies) with the 12v load drawn from it/them; draws that equal 12v amount from the bussman output to keep it all balanced?

2. Would a 200amp alternator burn out this bussman" or would the bussman just limit its input to 100amp and the other 100amp potential gets canceled out?

3. Purchased a "small balancer" below to use with my common man's copy of a Pulse tech solar balancer/pulse maintainer* Im getting the feeling this balancer works different than the bussman above. Would I be right to guess it pulls 24v juice thru it from all the bats connected to it and distributes it back out to each of two 12v batts accordingly to create balance between the two? Judging by wiring diagram shown on Amazon it would not "directly help" a single 12v batt that got out of balance if it was part of bank four batt 24v system; cause it does its balancing as if each pair of 12v was a single battery?


https://www.amazon.com/dp/B07FD1DYXW/?ref=idea_lv_dp_ov_d = small balancer

*but larger solar panel so it will actually charge too instead of what Pulse Tech version does; which is only match the drain created by the pulse system.
 

Ronmar

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A charged 24v battery bank is capable of delivering way more than 200A@24v,so a 200@ alt should have no effect upon it... what would ultimately do it in I think is trying to feed more than 100A Out of the 12v output...
 

coachgeo

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A charged 24v battery bank is capable of delivering way more than 200A@24v,so a 200@ alt should have no effect upon it... what would ultimately do it in I think is trying to feed more than 100A Out of the 12v output...
how would one circumvent that?? 90amp fuse or breaker?
 

mechanicjim

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how would one circumvent that?? 90amp fuse or breaker?
i think its the heat that kills it as it gets/ stays hot from trying to convert down to 12V from 24V all the time.

note: on battery equalization in a 24V system with two 12V batteries, the batteries are like two kids in a trench coat pretending to be a adult 24v battery.
So we have an upper(one you take 24V from) and a lower battery(the one connected to ground/chassis.)
In normal operation the voltage of both batteries should be equal. but when we take 12V loads(current) from the lower battery its voltage drops below that of the upper battery. With no equalization the 24V changing system doesn't see this imbalance and does nothing to fix it.
we add in a equalizer/dual voltage alt to bring the lower battery back up to an equal charge voltage as the upper battery. we do this by sending current back to charge the battery/provide current to loads so the battery it self doesn't need to do it. also if the lower battery voltage is higher than the upper no equalizer/dual alt can do anything about that and you need to either discharge via 12v loads or swap battery locations.

so technically you can treat the lower battery like a load and "charge" it with a Converter/Equalizer. this is why the bussman has the two different hook up methods.
 

Ronmar

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Port angeles wa
how would one circumvent that?? 90amp fuse or breaker?
Y0u mean in the event of a short circuit? A Large 90-100A marine breaker like Ohiobenz mentioned on the output 12v Would be advisable. They spec fuses for the Bussman(Seen on the drawings) those reccomendations should also be followed...
 
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