one for the electrical gurus, would this work?

had a random idea but not sure if itll work for when i finally get a van mount. Was thinking of usung a 12-240v inverter and using that to charge my backpack & in winter an oil filled radiator off the leisure battery, an a scr to top up said battery through the day. Then it occured to me, would it be possible to use the inverter to run the battery charger to the leisure battery? I know its not going to be as effective as mains, but could it be sufficient to keep it topped up when used alongside the scr? Im keen to see what you guys think or if anyone has tried it. @spruce you expertise springs to mind here

I think if you run a 1500w oil filled radiator off a 110Ahr Leisure battery it will probably last 30 minutes.
Probably not your best solution matey.


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Clisty1989 said:

had a random idea but not sure if itll work for when i finally get a van mount. Was thinking of usung a 12-240v inverter and using that to charge my backpack & in winter an oil filled radiator off the leisure battery, an a scr to top up said battery through the day. Then it occured to me, would it be possible to use the inverter to run the battery charger to the leisure battery? I know its not going to be as effective as mains, but could it be sufficient to keep it topped up when used alongside the scr? Im keen to see what you guys think or if anyone has tried it. @spruce you expertise springs to mind here

Click to expand...

:1f633: I'll never understand why you guys think I'm the expert around here.

Here goes. In other fields inverters run off a leisure battery bank to power some 230v appliances or equipment. Lets think of the marine leisure industry as one example.

So if you wanted to use an inverter to charge a backpack then it will work, even although its an expensive way of doing it and can't be called the most efficient. If I wanted to try this I would rather go for a 12v charger and rig that up the the van's electrics. Our Citroen Xsara has one auxillary socket which is live all the time and the cigarette lighter which only works with the engine running. My Citroen Relay van has 2 auxillary sockets and a cigarette lighter and none of them work without the engine running/ignition on.

A good pure sine wave invertor is expensive. A 500 watt unit can cost more the £120. There are cheaper variants to the pure sine wave invertors that could well power a backpack charger, I just don't know. But these cheaper units are catagorized as modified sine wave invertors. You also have to be very careful that the invertor you want to buy is exactly wjhat it says it is on the tin. Just look at YouTube videos for invertor reviews.

I have never left our backpack charger on all night. Wjhen the charger is on the backpack it gets checked regularly, and when the charge light changes colour I switch it off. I've always meant to ask Alex Gardiner if his chargers can be left on all night but have never got round to asking the question.

Now, if we could run a oil filled radiator from a leisure battery through an invertor we would all be doing it.

If you had a oil filled radiator that draw 1000w (most are twice that size) then you would need an alternator charging at 92amps to supply that power. A leisure battery won't do that.

See page 5 of this document.

https://www.tlc-direct.co.uk/Technical/DataSheets/Skytronic/Guide_to_Inverters.pdf

Mark Munro started to do a video using a leisure battery to power a small 230v tube heater in his van. His idea was to use solar to charge the leisure battery by day and utilise that power at night to keep his pumps from freezing up. He made 2 of the 3 videos and declared it a no go. If I remember his tube heater was 120 watt one - but I could be wrong.

We don't drive enough miles to replenish our battery power draw through the day using a SCR so taking more current out of the battery isn't going to help us.

.

RhysEvans88 said:

I think if you run a 1500w oil filled radiator off a 110Ahr Leisure battery it will probably last 30 minutes.
Probably not your best solution matey.


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Click to expand...

Why can't I say it like you have. :1f602:

@spruce youve probably forgotten more than i know. Only reason i thought about it was that running an extension lead to van isnt always practicle, and this could have been a work around, at least short term.

the other thought was getting a mechanic mate to install a second, larger altenator, like we had in army landrovers, only charging the leisure battery. Would that work in your opinion?

spruce said:

:1f633: I'll never understand why you guys think I'm the expert around here.

Here goes. In other fields inverters run off a leisure battery bank to power some 230v appliances or equipment. Lets think of the marine leisure industry as one example.

So if you wanted to use an inverter to charge a backpack then it will work, even although its an expensive way of doing it and can't be called the most efficient. If I wanted to try this I would rather go for a 12v charger and rig that up the the van's electrics. Our Citroen Xsara has one auxillary socket which is live all the time and the cigarette lighter which only works with the engine running. My Citroen Relay van has 2 auxillary sockets and a cigarette lighter and none of them work without the engine running/ignition on.

A good pure sine wave invertor is expensive. A 500 watt unit can cost more the £120. There are cheaper variants to the pure sine wave invertors that could well power a backpack charger, I just don't know. But these cheaper units are catagorized as modified sine wave invertors. You also have to be very careful that the invertor you want to buy is exactly wjhat it says it is on the tin. Just look at YouTube videos for invertor reviews.

I have never left our backpack charger on all night. Wjhen the charger is on the backpack it gets checked regularly, and when the charge light changes colour I switch it off. I've always meant to ask Alex Gardiner if his chargers can be left on all night but have never got round to asking the question.

Now, if we could run a oil filled radiator from a leisure battery through an invertor we would all be doing it.

If you had a oil filled radiator that draw 1000w (most are twice that size) then you would need an alternator charging at 92amps to supply that power. A leisure battery won't do that.

See page 5 of this document.

https://www.tlc-direct.co.uk/Technical/DataSheets/Skytronic/Guide_to_Inverters.pdf

Mark Munro started to do a video using a leisure battery to power a small 230v tube heater in his van. His idea was to use solar to charge the leisure battery by day and utilise that power at night to keep his pumps from freezing up. He made 2 of the 3 videos and declared it a no go. If I remember his tube heater was 120 watt one - but I could be wrong.

We don't drive enough miles to replenish our battery power draw through the day using a SCR so taking more current out of the battery isn't going to help us.

.

Click to expand...

Probably because you give answers that nobody else does. 

Clisty1989 said:

had a random idea but not sure if itll work for when i finally get a van mount. Was thinking of usung a 12-240v inverter and using that to charge my backpack & in winter an oil filled radiator off the leisure battery, an a scr to top up said battery through the day. Then it occured to me, would it be possible to use the inverter to run the battery charger to the leisure battery? I know its not going to be as effective as mains, but could it be sufficient to keep it topped up when used alongside the scr? Im keen to see what you guys think or if anyone has tried it. @spruce you expertise springs to mind here

Click to expand...

I'm going to comment separately to this question as I have always wondered about this.

ATM I have a simple 90 amp alternator charging my leisure battery through a SCR. Now we all know that alternators don't make good battery chargers, but for the purpose of topping up the starter battery with the small amount of current its taken to start the engine it will suffice. What it is good at is supplying all the current needed to keep the vehicle electrical accessories with the power they need. Hence the reason why manufacturers haven't got anything better. (Remember all vehicles supplied before the 1960's had generators - alternators weren't popular. I remember replacing a generator on my Dad's 1963/4 International van with an alternator in 1967. No one had a clue how to wire it up. Generators were not good at charging batteries but also weren't good at supplying the needs of the car's accessories either.)

We know that a 230v intelligent charger will charge a leisure battery more efficiently, so why not use a 230v intelligent charger through a pure sine wave invertor as this should do a better job.

However, my Numax intelligent battery charger still takes around 2 hours to fully charge our battery after a days work. So our short drive home of 20/30 minutes at the max isn't going to be long enough even with an intelligent charger in our application. So although I'm intrigued with the idea, I haven't bothered exploring it as I would be wasting money.

.

I've also been thinking about this a lot lately. I've got a 2012 van so I think a SCR would not work, I would need a more expensive b2b charger. I use my van for personal use too and probably do 60 miles business and 60-100 personal per week.

I have often wondered if it would be cheaper buying an inverter to plug into cigarette lighter near my leisure battery in the back and it can "bench" charge as I drive. My current 10a smart charger is 307w. If anyone has tried this I would be very interested. Honestly I can't see why it wouldn't work, surely it's only pulling the same power as a SCR would? @seymour sunshine maybe you would have some input? You have some really insightful electronic posts lately

Clisty1989 said:

@spruce youve probably forgotten more than i know. Only reason i thought about it was that running an extension lead to van isnt always practicle, and this could have been a work around, at least short term.

the other thought was getting a mechanic mate to install a second, larger altenator, like we had in army landrovers, only charging the leisure battery. Would that work in your opinion?

Click to expand...

No matter what they tell you a leisure battery will only accept a certain rate of charge. On our leisure battery I have only seen a max of 22 amps going into it briefly before it quickly settles down to 7 or 8 amps even after a full day's hard work. I have never seen our 10 amp Numax battery charger pushing in more than 4 or 5 amps. If a leisure battery is flat it has a low resistance inside it, so will accept a higher charge rate. As the battery gets more fully charged the resistance increases so reducing the rate of charge the battery will accept. So we generally see just 2 or 3 amps being driven into the battery with the alternator at 14.5vdc.

Numax did once tell me that a leisure battery should not be charged at more than 10% of its amperage. So my 115amp leisure battery shouldn't be charged at more than 11.5 amps.

They could well use double alternators in the army to supply stuff they need to power, it certainly won't be to charge starter batteries.

In NHS ambulances Sterling Products had a contract to replace the alternators and fit quality auxillary battery chargers to quicker charge the leisure batteries on board used to power their emergency equipment. I can't remember the exact figures but the alternators doubled in output capacity (around 180 - 220 amp) and their regulators were replaced with controllers that did a much better job at charging batteries. I believe the current battery to battery chargers for use with modern diesel are a miniature example of that equipment which cost a small fortune in those days. They were fan blown air cooled units and they were big enough to charge the starter battery and a bank of leisure batteries as well.

Some marine engines are supplied with 2 alternators, one to charge the starter battery and the other to charge the leisure battery bank.  But I think this is more to do with having a backup. (Our recently retired neighbour but one has recently bought a fishing boat with an outboard motor. Regulations require them to have a backup motor if using it out at sea which they do.) Most marine sailing vessels also have an on board generator to power heavy current draw appliances. For example, if they have a washing machine on board they need to run the generator.

There is also a 230v generator a similar size to a 12 v alternator that can also be used to drive 230v appliances with the engine running.

.

Dr Von Samstein said:

I've also been thinking about this a lot lately. I've got a 2012 van so I think a SCR would not work, I would need a more expensive b2b charger. I use my van for personal use too and probably do 60 miles business and 60-100 personal per week.

I have often wondered if it would be cheaper buying an inverter to plug into cigarette lighter near my leisure battery in the back and it can "bench" charge as I drive. My current 10a smart charger is 307w. If anyone has tried this I would be very interested. Honestly I can't see why it wouldn't work, surely it's only pulling the same power as a SCR would? @seymour sunshine maybe you would have some input? You have some really insightful electronic posts lately

Click to expand...

Sorry. Completely outside my sphere of knowledge.

My initial thoughts are: Using an inverter to drive a mains charger to charge a battery seems to me to be introducing too much complication into the system. And every time you introduce a device, you're losing energy since nothing is 100% efficient, so you'll certainly be drawing a higher current than you're charging the battery with.

Dr Von Samstein said:

I've also been thinking about this a lot lately. I've got a 2012 van so I think a SCR would not work, I would need a more expensive b2b charger. I use my van for personal use too and probably do 60 miles business and 60-100 personal per week.

I have often wondered if it would be cheaper buying an inverter to plug into cigarette lighter near my leisure battery in the back and it can "bench" charge as I drive. My current 10a smart charger is 307w. If anyone has tried this I would be very interested. Honestly I can't see why it wouldn't work, surely it's only pulling the same power as a SCR would? @seymour sunshine maybe you would have some input? You have some really insightful electronic posts lately

Click to expand...

All of this is also out of my field of expertise.

Here's an example

To work out current/battery capacity requirement (for 12V system):

Power (Watts) / 12V = Current hour (Ah)

This is the rough calculation for the size of a vehicle alternator you would need to keep up with a specific load, as an

inverters efficiency is only rated around 90%, the current requirement will need to be 10% higher; for example, to keep up with a continuous draw of 1000W, you would need:

(1000 ÷ 12) × 1.1 = 91.67 Ah

Therefore an alternator with minimum output current of 91.67A at 12V is required to run continuously. Alternatively a fully charged 12V battery with capacity of 91.67Ah can run continuously for around an hour.

So at 307 watts you would be using 1/3 of the power in this example. So you would need a 500w invertor hard wired onto your vans starter battery via a 140amp Durite vsr and 70 amp supply cables. This would disconnect the invertor when the engine was switched off and reconnect it when the engine is started again. Forget the cigarette lighter.

I am however not sure when you will be drawing the max of 300 watts as I've never seen my intelligent charger at more than 6 amps at 13.9vdc. That's just slightly over half the 30 amps it would draw on maximum. But then again, I have never seen my intelligent battery charger record a leisure battery charge capacity of less than 50% - its between 75 and 100% charged 99.9% of the time.

.

sounds like there is potential for an idea here, but possibly not feasible in our field of work. One of my customers os an electrical engineer, i think ill pose the question to him next time i see him, get his input. If he sees a way of it working that wont cost the earth, itll probably make a lot of our lives a lot easier, perhaps it could work in conjuction with other means of charging, such as solar power, a type of regenerative braking etc.

a window cleaning van that never needs a bench charge, and can charge all the electrical appliances needed to be self sufficient, that would be the dream.