1986 TMC 102A3 - inverter design question

[jraynor]

Richard,

On my 102A3, the batteries are located forward of the first bay near the front of the bus. So the first bay is next door to the battery bay. The only wiring I'm debating on is the wire from the battery to the inverter. With them that close, I'm hoping it'll only be about 5': from the battery, through a bay wall into the inverter

[richard5933]

Richard,

On my 102A3, the batteries are located forward of the first bay near the front of the bus. So the first bay is next door to the battery bay. The only wiring I'm debating on is the wire from the battery to the inverter. With them that close, I'm hoping it'll only be about 5': from the battery, through a bay wall into the inverter

That would be different then. I was assuming that the batteries were near the engine. In that case, I'd say that you're good to go. Some would disagree, but I'd go with the welding cable if it's not running through the engine bay. Plan for the max size inverter/current draw you can have and then get the cable sized accordingly.

[jraynor]

Thank you Richard,

So Brian, is 1/0 still a good size for the 4kW,8kW surge inverter at 28volts with a cable length less than 10'? I just want to be sure as everything I have been searching and seeing says 3/0 or 4/0.

I'll post my electrical layout tomorrow with my inverter load calc shown on it

[buswarrior]

The old Trace 4024 that I have is getting close to 20 years old.

It is a sweet piece. Inverter charger, continuous power in the coach, regardless of power pole or battery or engine running.

Of great importance, this model can be told how much power is available. If you only have a 15 amp extension cord plugged into a friend's house, the Trace will not trip the house breaker, add whatever extra power is needed from the batteries, and automatically go back to charging the batteries when the load subsides.

I spent way too long screwing around with a mobile command/training unit on insufficient power, having to do load management...

Not doing it with my conversion.

Choose the top of the line unit FIRST, and skip wasting the ca$h on other stuff that you will replace later.

Smart folks: what is the equivalent Magnum model that performs like my old Trace?

Happy coaching!
Buswarrior

[eagle19952]

The old Trace 4024 that I have is getting close to 20 years old.

It is a sweet piece. Inverter charger, continuous power in the coach, regardless of power pole or battery or engine running.

Of great importance, this model can be told how much power is available. If you only have a 15 amp extension cord plugged into a friend's house, the Trace will not trip the house breaker, add whatever extra power is needed from the batteries, and automatically go back to charging the batteries when the load subsides.

I spent way too long screwing around with a mobile command/training unit on insufficient power, having to do load management...

Not doing it with my conversion.

Choose the top of the line unit FIRST, and skip wasting the ca$h on other stuff that you will replace later.

Smart folks: what is the equivalent Magnum model that performs like my old Trace?

Happy coaching!
Buswarrior

IF you ever get to Bradenton,FL Jaytron has a guy...
He laments when an old Trace hits the bin...
Guy knows his stuff.

[jraynor]

Low and Behold, my electrical design.

Ignore the fact that the inverter is not connected via 24volts yet, I haven't updated it yet. And yes, its quite confusing, but there is a method to the madness, here is the break down:
When OTR: The only things that will have power is the inverter powering the Travel panel (besides the DC rectifier) and the 12v panel that comes off the battery. I plan to use 100% 12V LED lighting so that lights are always on at any point.
When parked, we can use 30Amp or 50Amp service: At this point, the batteries will be charging (or being maintained) 120V power will provide power to the main panel which powers the sub panels A/C and Travel. The DC Rectifier will also be power which will give us 12V to the lights instead of using batteries
When off grid: we will have the genny to provide power. I haven't done any load calc on the Genny yet but its a 4.8kW 120V 20/30 Breaker set Onan that I got for $200. But I need a $150 card to possibly get it running. So it wasn't a bad price and I figure if we are off Grid, Then we can be more backwoods on our usage (I don't plan on camping backwoods style in 100+ heat)

Inverter load Calc: as you can see I have the following: Fridge running 12A (80% load on standard 15A breaker) which is the most it should ever draw if anything, TV and DVD for entertainment, and some 120v outlets(3 or 4 for charging a laptop or something) for OTR at 12A @120v. So im at 3kW so I figured id bump up to the next size. I would imagine that inverters only draw what they need to meet the demand versus putting out the full 4kW constantly

[bevans6]

The fridge will probably draw closer to 2 - 3 amps, and intermittently at that.  The other output string of TV, DVD, lap-tops around the same, if not less.  The only things that draw significant current in a bus environment are air conditioners, heaters of some sort, which include stove tops, induction cookers, hot water heaters, propane fridges when on AC power, and large electric motors, most typically an air compressor.  You can use 4/0 if you want to, for me it is over-kill.  Remember that you are not drawing the power from the battery bank, you are drawing from the alternator, which is connected by a five foot long piece of 1/0 cable to the starter motor stud in the engine bay, then 30 odd feet of 4/0 between the engine bay and the batteries.  So you are already running your inverter over 1/0 in the first place.  Also, the ampacity of 1/0 is 150 amps continuous (far higher intermittent), and at 28 volts (alternator output when running) that's 4200 watts.  But it's up to you what you do, all I can tell you is what I did. 

Edit:  Your diagram shows you running the 12 volt inverter from a center tap off the start batteries.  You CANNOT do that, it will kill the batteries in very short order.  The most you can draw from that center tap reliably is around 30 amps, and even then you need to have an equalizer to supply that 12 volt current from both batteries.

[richard5933]

If you have  24v chassis battery bank, then you need a 24v maintainer and not two 12v units. If you're installing a 24v inverter, then you have the option of having that do the battery charging for you, or you can just get a multi-stage 24v battery charger. I'd recommend either of those over a maintainer, since if you inadvertently run down the chassis batteries a 'maintainer' is not going to get you going anytime soon.

[jraynor]

Brian,

Yeah I haven't updated the drawing to show me pulling the 24 v to the inverter. The only thing I'll be using 12v for is LED lighting throughout and the other few things show in the 12v panel. Would it be best to pull off the center that or from the far end of the 2nd battery? The inverter calc is way over kill so I won't ever have an issue. Plus once I choose a fridge I will update it with the specs. And I will go with 1/0. Better for the wallet anyway.

Richard,
Where do you buy a multi stage 24v charger? I searched the web for when I first went to charge my batteries and could never find one.

Thank you

[richard5933]

Here's the charger I'm using when needed on the chassis batteries. It's only slightly more money than some of the better battery minders and much  better. I believe that they also have a 40-amp version of the 24v charger. You can also get the remote dongle to plug in and see what's going on from in the bus.

https://www.ltdrvparts.com/PROGRESSIVE-DYNAMICS-25-AMP-24-VOLT-CONVERTER-CHARGER-PD9225-24-PD9225-24.htm

[bevans6]

You can charge two 12v batteries in series with two 12v chargers, the output's float so each one sees only it's battery.  The converter chargers noted are excellent units for 24v charging.  Other options:  https://www.batterystuff.com/battery-chargers/24-volt/

You really do want an equalizer (Vanner, or others) to maintain the equal charge in your batteries when tapping for 12 volt loads.  An equalizer is basically a 24 volt power supply that draws power from both batteries, puts out a 12 volt load output that is exactly half of the 24 volt input, and that is what actually supplies the 12 volt loads while at the same time forces the two 12 volt batteries to each have the same state of charge.

Brian

[Lee Bradley]

Low and Behold, my electrical design.

Ignore the fact that the inverter is not connected via 24volts yet, I haven't updated it yet. And yes, its quite confusing, but there is a method to the madness, here is the break down:
When OTR: The only things that will have power is the inverter powering the Travel panel (besides the DC rectifier) and the 12v panel that comes off the battery. I plan to use 100% 12V LED lighting so that lights are always on at any point.
When parked, we can use 30Amp or 50Amp service: At this point, the batteries will be charging (or being maintained) 120V power will provide power to the main panel which powers the sub panels A/C and Travel. The DC Rectifier will also be power which will give us 12V to the lights instead of using batteries
When off grid: we will have the genny to provide power. I haven't done any load calc on the Genny yet but its a 4.8kW 120V 20/30 Breaker set Onan that I got for $200. But I need a $150 card to possibly get it running. So it wasn't a bad price and I figure if we are off Grid, Then we can be more backwoods on our usage (I don't plan on camping backwoods style in 100+ heat)

Inverter load Calc: as you can see I have the following: Fridge running 12A (80% load on standard 15A breaker) which is the most it should ever draw if anything, TV and DVD for entertainment, and some 120v outlets(3 or 4 for charging a laptop or something) for OTR at 12A @120v. So im at 3kW so I figured id bump up to the next size. I would imagine that inverters only draw what they need to meet the demand versus putting out the full 4kW constantly

My 50 amp cable enters the bus and connects to a 50 amp disconnect/breaker panel within 18". The disconnect feeds a 240 vac breaker panel that feeds loads I don't want to power through the inverter (mostly). That panel feeds the inverter 110 vac, three way water heater 110 vac, mini split 220 vac, hydronic heating boiler 220 vac. Only one side of the panel is powered when using a 30 amp adapter on the 50 amp cable so make sure that side feeds the inverter breaker. I use a 4024 Trace inverter on a 50 amp breaker to power a sub panel (all 110 vac) 12 breakers that feeds all the bus 110 vac systems refrigerator, TV, outlets, microwave, washer/dryer, outlet in the engine bay for air compressor, start battery maintainer, block heater, an outlet in electrical bay to power the mini split through a 5,000 watt step up transformer. I have a 220 vac welder socket off the first panel and a welder socket off the transformer and I plug the mini split into either one depending weather or not I have 50 amp service. The inverter charges the house batteries when powered by pole power if the pole power is not enough for the bus load the inverter uses battery power to make up the short fall and if the batteries get to low the inverter starts the generator to add power and if this falls and the battery voltage gets down to a set voltage it shuts down the system. The DC side is mostly LED lighting 24 volt with some 12 systems so I have a 30 amp Vanner on the house batteries plus some solar; 20 amp of 26.8 volts on float.       

[sledhead]

very nice set up Lee

dave

[Lee Bradley]

Pretty much right out of George Myers' "Designing Electrical Layouts for Coach Conversions".