24V vs 12V decision time - that's driving my Invertor choice

blutow

Well-known member
Victron makes a (ground) isolated version of their 30 amp DC-DC charger. In theory you should be able to cascade two of them to make a 24V charger. But since chargers are most of the time voltage sensing, I am not sure if it would work. It should be possible to connect each to one of the 4S cells and that way charge each 12V battery individually. I am curious if anybody has tried either approach or communicated with Victron about the feasibility.
They make a DC-DC that works with a 12v chassis system and outputs 24v. You can run 2, but in parallel.
 

Graphite Dave

Dave Orton
Dave

I read about your vehicle powered invertor and thought that was really neat idea - what stopped me form going down that route was if I wanted to say get upto 80 amps @ 12v from alternator i would need an at least 1,000W invertor - and at that point it would be close to costs of a dedicated DC to DC charger unit ~ $300 - and if i look at the KISAE i picked out I get free MPPT along for the ride - For solar I plan to have a fixed on the roof rigid panel (maybe two If I can fit them) and these will be powered using either the DSSR/Electradaus or the DMT2430. I would then later down line add in some flex panels plopped on top of an awning for extra sun juice. Lots of moving parts but hoping my logic makes sense and hoping that I dont have to spend so much brain power on the fluid systems either ins or outs :p)
The 08 Sprinter build had a 600 watt pure sine inverter. On the Transit build I installed a 1000 watt inverter. With a diesel Sprinter it is important not to set the dash controls for heat if the engine is cold. Sprinter has an automatic electric air heater to provide warm air to the cab when engine is cold. I believe the electric air heater consumes around 1000 watts so you do not want to run the vehicle powered inverter at the same time as the Sprinter electric air heater. As I recall the Sprinter voltage dropped about 1/2 volt when the air heater is running. I had a Scan Gage so could watch the voltage change to determine when heater was running. I had the Scan Gage set to read voltage and water temperature. I believe the heater stopped running when the water temperature reached about 150 degrees.

The advantage of the vehicle powered inverter is having 120 volt AC power available with engine running. With my low electrical power requirements, I seldom need to charge from the engine. The single 300 watt solar panel almost always gets me back to 100% SOC each day. Even in overcast weather. Charging from the engine is my backup if weather conditions force its use. I do regularly use the 120 volt AC power to heat shower water or run a 750 watt electric air heater.
 

Airtime

Well-known member
I have a 24V system including 24V Multiplus 3000. If I were to do it over again, I would go 12V. My Multiplus is next to my battery so those cables are very short. As for the rest of the van, choices in 24V are either few or non-existent. And where they do exist, are more expensive.
- Alternator charging--must install DC-DC converter
- Maxxair--12V only
- Lighting--I gave up on 24V choices and went all 12V
- Tank heaters and heat trace--either 12V or 120V are available at reasonable cost, forget 24V
- Water pump, macerator pump--24V available but costs 50% more, I went with 12V
- Nations alternator--N62 2 belt kit only for 12V
- REC BMS (was looking at for Wakespeed/Nations integration)--24V version is less capable and more expensive, can't handle DC load disconnects

I ended up with a 24V breaker panel with just 3 items (fridge, Espar, macerator toilet) plus a feeder for my 24-12 70A DC-DC converter to feed my 12V fuse block, which supplies most of the van's wiring.
 

spaner

Florence - 144 AWD Cargo
I wanted to get folks opionions on "Orton" method for vehicle shore power vs DC to DC charger for my system

I had orginally planned on a 12/24v Dc to DC unit from KISAE but it is delayed until sometime next year . Pricing out multiple Victron 24v units gets me over $822 list price and adding complexity (and I suppose on flip side redundancy) of controlling these via my Electrodacus. Lets say I want to draw 100 amp from Alternator on 12V side- I can get a reasonable 2,000W PSW Invertor only for around $400 which I would use as dedicated vehicle shore power

I would need a two way switch for selecting convetional shore power and vehicle shore power which I assume does not have to be crazy specced as I would only make the selection with no power being drawn (if I am driving whilst plugged into conventinal shore power I am going to have bigger problems)

Can I draw 2,000W / 12V = 166 Amps from vehicle side - I would restrict it to max 100 amps - or am i better for efficiency getting a smaller invertor and running close to max

Can I run invertors for extended times (I am thinking 5 hours for a very depleted battery as worse case)
I can plan some fans for heat extraction - I know the DC Dc convertors all seem to get hot also so that means three extraction fans..

Pro - simplified control for electrodacus BMS - one device controlling charging (Victron Multiplus ), <$. I think I can place this invertor under passenger seat so will only need a small gauge 120V AC cable to get power to rear
Cons Redunadancy, double invertor losses (vehicle shore plus multiplus) - have to run Multiplus longer and that also will generate heat / noise

adding @Graphite Dave to the many tags :p) @3Play @Airtime
 
Last edited:

Graphite Dave

Dave Orton
Do you need 100 amps from the alternator? Will you be using enough power to require that charging rate?

I believe 2000 watt inverter is too large for a vehicle powered inverter. Be aware that a NCV3 has an automatic electric air heater that uses about 900 watts of alternator output when it is operating. Electric air heater turns on when dash controls are set for heat and engine is cold. Turns off when engine water temperature is high enough to provide heat. As I recall it shuts off around 140 degrees.

I have two selector switches. First one selects real shore power or vehicle powered inverter shore power or off. Second selector switch selects charging (power to the house inverter/charger/transfer switch) or electric air heater or electric water heater. I limit the power from the vehicle powered inverter by limiting the connected load. The shore power charger is set for 40 amps.

Inverter can be run continuous if you have adequate cooling. Do not bury the inverter in a cabinet. I did that and overheated the inverter. An additional 120 volt AC cooling fan can be plugged into the inverter duplex outlet, so it runs when the inverter runs.

Both a DC to DC and an inverter have efficiency losses. Which is higher? Do not believe that is important. Doubt you can see a measurable difference in fuel economy when alternator is providing power.

Electrical | Orton Travel Transit (ortontransit.info)
 

HarryN

Well-known member
Actually you don't need a switch to move from charging via the alternator / inverter to charging from shore power.

On a lot of RVs, there is a power cord that you move from being plugged into the generator to plugging into shore power.

If you want to keep life simple, you could do exactly the same thing - just unplug from the inverter instead of a generator.
 

spaner

Florence - 144 AWD Cargo
Do you need 100 amps from the alternator? Will you be using enough power to require that charging rate?

I believe 2000 watt inverter is too large for a vehicle powered inverter. Be aware that a NCV3 has an automatic electric air heater that uses about 900 watts of alternator output when it is operating. Electric air heater turns on when dash controls are set for heat and engine is cold. Turns off when engine water temperature is high enough to provide heat. As I recall it shuts off around 140 degrees.

I have two selector switches. First one selects real shore power or vehicle powered inverter shore power or off. Second selector switch selects charging (power to the house inverter/charger/transfer switch) or electric air heater or electric water heater. I limit the power from the vehicle powered inverter by limiting the connected load. The shore power charger is set for 40 amps.

Inverter can be run continuous if you have adequate cooling. Do not bury the inverter in a cabinet. I did that and overheated the inverter. An additional 120 volt AC cooling fan can be plugged into the inverter duplex outlet, so it runs when the inverter runs.

Both a DC to DC and an inverter have efficiency losses. Which is higher? Do not believe that is important. Doubt you can see a measurable difference in fuel economy when alternator is providing power.

Electrical | Orton Travel Transit (ortontransit.info)
I have a 6,700 W (280ah @ 24V) of battery that I am trying to charge up - I have on order a VS30 which I hope will be fitted with the new for MY23 280 A alternator - with 80 amp being ok for the standard 22 version in 23 I think i can get 100 out of one that . I am going to try and replish a system that will be driving a mini split air conditioner which i calculate may last max of two days with current battery system

re 2,000W invertor with the alternator i plan to have assume that will be ok
 

Graphite Dave

Dave Orton
Actually you don't need a switch to move from charging via the alternator / inverter to charging from shore power.

On a lot of RVs, there is a power cord that you move from being plugged into the generator to plugging into shore power.

If you want to keep life simple, you could do exactly the same thing - just unplug from the inverter instead of a generator.
The Blue Sea 3 position switch # 9009 I used disconnects one source before connecting the second source.


Read the paragraph "The purpose of the AC source selector switch". It states that the switch disconnects the first source before connecting the second source.
 

spaner

Florence - 144 AWD Cargo
Actually you don't need a switch to move from charging via the alternator / inverter to charging from shore power.

On a lot of RVs, there is a power cord that you move from being plugged into the generator to plugging into shore power.

If you want to keep life simple, you could do exactly the same thing - just unplug from the inverter instead of a generator.
Indeed I guess I just terminate the AC in to the multiplus with female/socket pig tail
 

spaner

Florence - 144 AWD Cargo
The Blue Sea 3 position switch # 9009 I used disconnects one source before connecting the second source.


Read the paragraph "The purpose of the AC source selector switch". It states that the switch disconnects the first source before connecting the second source.
I do like idea of switch to make it somwhat idiot proof - not imediately but eventually I might trust the yound uns to take van out - I trust them but their friends not so much ...
 

Top Bottom