Inverter In Transit Van.

[apprentice101]

Hi I'm a qualified electrician but new to car electrics. Basicly want to do a mate a favour he needs to to run a 1200 watt 230v cement mixer for about 20 minutes at a time. So i've googled and you tubed and recon i'm nearly there. Im thinking connect the starter battery under the seat to a deep cycle battery in the back which will feed the inverter. I'll put some sort of solonoid switching arrangment between the batteries so that the starter battery will not be drained by the inverter but the inverter battery will be charged when the ignition and engine are on. So my questions are:
1 what sized battery to use to feed the inverter. Id like a fair bit of over capacity in the amp hour department for obvious reasons. Ive done the maths which would suggest i could get away with a 6 amp hour gel battery but that just seems too small.
2 what kind of solenoid switch would be suitable.
3 can he plug a 110v step down transformer into it for an electric drill or will that cause problems. I dont think it will but a mate who is a sparks seems convinced it will burn out the inverter. Cant explain to me why though lol.
Cheers john.

 

[plugsandsparks]

First thoughts are, how many times does he need to use the mixer before he has a chance of charging the battery again. It may be easier to over club the inverter and get a 2KW inverter and simply get the guy to run the engine on the van to basically use the inverter powered through the vehicle alternator using the battery as a go between. Its basically what I do when I am using my power tools off the vehicle and it makes sure I have enough juice to start the vehicle at the end of the day. I don't bother with a second battery. As for a site transformer for 110V, good luck with that, they have horrendous start up currents and I would expect the inverter to simply shut down when you try. I have not done it but have had enough problems with them when connecting directly to the mains... lol

 

[UKMeterman]

Hi,
It sounds like a bad idea for many reasons, calculate the current at 12V for starters... Best get a small generator and transport that with the mixer.

 

[ruston]

Or a small petrol mixer.
The impression is that he cannot get a power supply where is working.

PS, one of the reasons is leaving the van running unattended is an offence. The other is that it might not be there when he gets back.

 

[telectrix]

1200 watts @ 12V is 100A. that's a hell of a load from a vehicle. as said before, a genny is a better option.

 

[ruston]

Aye and the battery is going down all the time unless he has a super dooper alternator lol.

 

[UNG]

PS, one of the reasons is leaving the van running unattended is an offence. The other is that it might not be there when he gets back.

It is not an offence if it is fitted with a Run Lock unit

This would be the best option for the OP http://www.powerall.co.uk/

 

[PEG]

Hi,1200 watts is a big yoke...what are you mixing? Epoxy?

Mine is half as big again,than a Belle transportable,and has a 300 watt motor...

A decent 1500W inverter,would cope easily for 20 mins,jump-lead clipped to the vehicle battery,engine running to assist with depletion.

I have regularly used a 3kVa 110 tranny,on a 2000W inverter,and had no issues,whereas it used to pop domestic MCB's on plug-in for fun,till i got bored with the walk-of-shame,to the DB, and stuck a thermistor in there...

 

[ruston]

@UNG
It does say in your link that it is not to be used on public highways, and in the PDF in read more it says this.

The Run Lock 2 supplied by RSG Engineering is sold ‘Not For Use On Public Highway’ because of the following points:

Leaving your vehicle unattended whilst the engine is running is known as "Quitting" and is an offence against S42 of the RTA 1988. It is dealt with by Regulation 107(1) of The Road Vehicles (Constriction and Use) Regulation 1986. Regulation 107(2)(a). This states that no person shall cause or permit to be on any road any motor vehicle which is not attended by a person duly licensed to drive it unless the engine is stopped and the parking brake is effectively set. Exemptions to the requirements of this Regulation as to the stopping of the engine include a fire brigade vehicle, the engine of which is being used for any fire brigade purpose. 2. Highway Code Rule #123 The Driver and the Environment. You MUST NOT leave a parked vehicle unattended with the engine running or leave a vehicle engine running unnecessarily while that vehicle is stationary on a public road. Generally, if the vehicle is stationary and is likely to remain so for more than a couple of minutes, you should apply the parking brake and switch off the engine to reduce emissions and noise pollution. However it is permissible to leave the engine running if the vehicle is stationary in traffic or for diagnosing faults. [Law CUR regs 98 & 107] 3. The Road Traffic (Vehicle Emissions) (Fixed Penalty) Regulations 2002 The regulation enables local authorities in England to issue fixed penalty notices to drivers who allow their vehicles to run unnecessarily while stationary. These regulations came into force on 18th July 2002. The powers to do this are automatically conferred by the regulations, therefore local authorities do not have to apply to be designated to use them. There are however a number of situations where action would not be taken: Where a vehicle is stationary ‘owing to the necessities of traffic’ - eg where a vehicle is stationary at traffic lights. Where an engine is being run so that a fault may be traced and rectified. Where machinery on a vehicle requires the engine to be running – eg where the engine powers a refrigeration unit, or compaction equipment in a refuse vehicle.

 

[Lucien Nunes]

Ive done the maths which would suggest i could get away with a 6 amp hour gel battery but that just seems too small.

Your hunch is right and your maths is way out. Always do a sanity check: 1200W x 1/3 hours = 400 watthours. 6Ah x 12V = 72 watthours. So based on energy capacity alone, the battery needs to be at least 5.5 times larger. In fact it needs to be much larger still, mainly because you can't fully utilise all the energy in a lead-acid battery in 20 minutes from full to flat. If you try to discharge it that fast, it becomes very inefficient and the voltage drops too low to be useful long before you've had nameplate capacity out of it. You might also exceed the maximum permissible current - it might overheat and outgas, or the plates might buckle. At that discharge rate you would probably need to double the minimum capacity to mitigate these effects. Also, to avoid premature loss of performance you would not want to take it to 100% depth of discharge, unless it's a traction battery (as in forklifts etc). You also need to allow for inverter and wiring losses. 1200Wh i.e. 100Ah at 12V is more realistic.

In fact the mixer won't consume 1200W continuously, but the 100Ah battery will be about the minimum size that will handle the starting current etc. Beware that the starting load of something like a mixer which might have an unbalanced load to raise, can trip an otherwise adequately sized inverter. Also that the motor torque may be reduced on a quasi-sine inverter.

All these limitations are why the engine-driven alternator mentioned above is a very good idea!

 

[Dan]

Or a small petrol mixer.
The impression is that he cannot get a power supply where is working.

PS, one of the reasons is leaving the van running unattended is an offence. The other is that it might not be there when he gets back.

I didn't know that. Are you not meant to leave a vehicle running unattended?

 

[ruston]

No. I added the text from the PDF , it is in post #9.
There are many things that a lot of drivers are unaware of that can attract a ticket, another one is 'at least two wheels on the road on a mini roundabout.' Not all four on the blocked or painted area.

 

[armour king]

I'm industrial commercial but have had vehicles as a hobby for 30+ years -
Note: a vehicle mounted alternator is not sophisticated , if you wish to use it to charge two 12v batteries in parallel it will allocate its charge rate to that of the lowest charge battery , so both batteries will receive the same level of charge .
This has the effect of heating the higher state of charge battery up.causing shorter life .-
Use a genny-
-
Or secure a split charger unit from a camper/cara van etc -
Vanner are good.