Inverter ( 12 v to 240) ?

[Deleted member 4366]

I have been building and installing alternative power supplies for the best part of 40 years as a successful business. I have worked hand in hand with "the industry" in improving, promoting and simplifying designs and applications for end users. I have learned through life's experience, that I don't always get it right, and I can learn further information from two year old to a one hundred year old and beyond. Part of my interest includes the use rechargeable forms of transport for use in remote locations where off grid supplies are the only source. When someone brigs up a question to the viability of using such a supply, I'm interested. You obviously have no idea the amount of time effort and money I've sunk into my "interests", in the same way I have no idea of who you are, and unlike you, I make no assumptions. For all I know, you could be one of the development engineers I am in daily contact with.

Your comments in this thread don't make sense. Flyingppg offered a very efficient and cheap way of charging an ebike from any off-grid power source or other low-voltage source of electricity. I would have thought that with your knowledge and experience of off-grid systems, you'd welcome that. I've never seen a better solution other than maybe a more expensive ready made MPPT variable voltage step up charge controllers you can get from Aliexpress.

 

[SHAN]

Your comments in this thread don't make sense. Flyingppg offered a very efficient and cheap way of charging an ebike from any off-grid power source or other low-voltage source of electricity. I would have thought that with your knowledge and experience of off-grid systems, you'd welcome that. I've never seen a better solution other than maybe a more expensive ready made MPPT variable voltage step up charge controllers you can get from Aliexpress.

Like many of your other "sniping" retorts through various posts you haven't read the thread properly.
My question was to the statement made about "not using invertors" and the reasons for, which has not been answered. Do you have some input into this, any viable information that I can add to my files ?
Of course the input regarding the charge controllers is of interest, but that is not what I asked about. If you are installing domestic systems costing £1000's and someone issue a point of doubt, I want to know about it.

 

[Flyingppg]

So no testing information, and no references to share from the guy that sees these things as all important. And as you've already pointed out without such things anything you say is about as useful in the real world as faith and religion.

I'm afraid I can't reconcile your lack of understanding of, what must be, basic core knowledge to someone with your declared experience and expertise.

Or maybe you just what to make commercial gain from other people's effort without being prepared to share yourself. That seems like a parasite.

Maybe you have been living off grid too long?

You started with the sneering aspersions and I was always told if you can't take a bit then don't give it out. You seem found out to me.

 

[SHAN]

You started with the sneering aspersions and I was always told if you can't take a bit then don't give it out. You seem found out to me.

Rather than answer a genuine question which I am still interested in, you degrade yourself by trading insults, my whole point of joining this forum was to learn about pedelecs as something to enjoy in my retirement which is two months away. My business interests are meaningless. I have not, and will not lower myself to behave in your manner out of respect for the forum guidelines.

 

[mike killay]

So no testing

You started with the sneering aspersions and I was always told if you can't take a bit then don't give it out. You seem found out to me.

First sneer.

However I have a feeling you really don't know your inverters from your transformers from your switched mode power supplies.

 

[SHAN]

First sneer.

However I have a feeling you really don't know your inverters from your transformers from your switched mode power supplies.

Thank you Mike. I think this post is best left in peace. I asked a genuine question, which if I had been inversely asked I would have done my level best to supply a genuine and helpful answer, and if I couldn't give the answer, then I would have held my hands up in admission. Two members who have "answered" in this thread have brought it down to the level of the infants playground, so for anyone else reading this, I'm off, and thanks to those who did answer my, and others, queries to conclusion. Good luck all and happy cycling.

 

[Deleted member 4366]

My question was to the statement made about "not using invertors" and the reasons for, which has not been answered.

I did read properly and he did answer that. That's the bit about what you said as not making sense. In case what he wrote was incomprehensible for some, I'll paraphrase: In the context of OP's question on how to charge from 12v, it would be better to charge from the converter that he recommended rather than to waste power and expense converting 12v to 230v via an inverter, then back down again to 42v using an ebike charger.

 

[Flyingppg]

I suspect even a decent 1kw inverter will be cheaper than 12v ( input). Charger from Yamaha.
But not even seen one ?

If you want to go the inverter route and you're charging with a commercial charger the input amps will be written on the charger and over stated. For a typical 42v 2a 230vac charger a 250w pure sine wave inverter will be more than enough but still much heavier and less flexible in the motorhome and much more expensive than the simplest option of the mppt 7210a unit I suggested before.

Have you got a solar panel on your motorhome already? If you do, if I were you, and this is what I actually do in my motorhome, I'd run the 7210a limited to 3a output (I'm charging at 42v) from the 12v power output on your existing solar charge controller (you need one rated at 20 amps or more). You will be pulling max 15 amps from your solar panel and batteries. This is also the usual limit from a standard cigarette lighter socket. This way if you draw too much and flatten your leisure batteries too far your solar charger will cut the supply to the 7210a bike battery charger. The 7210a also has a timer facility so you can limit the charging time too if you want to.

When you are driving, if your bike battery will take it, you can also up the amps out of the 7210a because you have the benefit of the vehicle alternator but be mindful of the current draw from the 12v input. That 7210a can put out 600w, and draw over 50 amps at 12v! I just stick to 3 amps.

I can also divert the power from my solar panels direct to the 7210a for charging, for example when driving. Doing this you can, of course, be sure you never flatten your leisure battery and the 7210a will do the best mppt it can from the solar panel whenever the sun is shining.

My one real criticism of the 7210a is that the fan is really noisy and so I changed it in mine, 99p for two 40mm fans on eBay. Really annoying. I'm never running it that hard. The mppt tracking can also be a bit flaky if going pure solar and drops out from time to time when a cloud goes over but then it was less than £30.

Good luck!

 

[wheeliepete]

Thanks Flyingppg for bringing these mppt's to the forum. I love new tech that doesn't cost a fortune.
Is the output voltage on the 7210a stepped 24/36/48 etc, or can you charge between those voltages?

 

[Flyingppg]

https://www.alibaba.com/product-detail/Waterproof-dc-dc-step-up-power_60266247471.html?spm=a2700.7724857.main07.245.7345f025QOmrbT

Would this work?

Might do but it's behaviour when operating below 42v is unclear from the listing also if it switches off when charging reduces below a certain threshold, usually you want it to around 100ma. What you can't do with lithium it's leave it on trickle charge and you need a charger that will turn off completely at full charge.

 

[Flyingppg]

Thanks Flyingppg for bringing these mppt's to the forum. I love new tech that doesn't cost a fortune.
Is the output voltage on the 7210a stepped 24/36/48 etc, or can you charge between those voltages?

No, it's not stepped like that. You can have any maximum current/voltage you like output up to 10a and 60v, power source and battery state of charge permitting and it will cccv charge up to those limits and then turn off when the battery is "full", in actual fact when the charging current drops to around 5% of the maximum limit set.

I'm getting into the habit of sometimes charging my battery up to 41v if going on a shorter ride to try and make my battery last longer.

 

[wheeliepete]

No, it's not stepped like that. You can have any maximum current/voltage you like output up to 10a and 60v, power source and battery state of charge permitting and it will cccv charge up to those limits and then turn off when the battery is "full", in actual fact when the charging current drops to around 5% of the maximum limit set.

I'm getting into the habit of sometimes charging my battery up to 41v if going on a shorter ride to try and make my battery last longer.

That's great. I was hoping it was variable between those voltages. I run at 50v, or 52v if you prefer and also charge to 80-90% sometimes for the same reason. I am aware that this practice is not agreed upon by all, and I wouldn't recommend it to anyone, but hey, it's my battery.

 

[danielrlee]

*Ahem*

Right, I'm going to give it a go.

Most electronic goods that 'require' an AC input, actually operate on DC – Alternating current is rectified into direct current, before being stepped down via a transformer or SMPS, then goes on to power the device in question.

An inverter takes a DC input and outputs AC. This conversion process comes with an efficiency hit. I am assuming that the point being made is “Why go to the trouble of converting the DC into AC, just to convert it back into DC?”

A number of solutions have been provided as a way around this unnecessary conversion process, and allows a direct DC-DC step-up/down that is far more efficient than using an inverter. Is there a reason that these aren't an acceptable solution for your requirements?

EDIT: Damn it! d8veh beat me to the point.

 

[Flyingppg]

You can have any maximum current/voltage you like output up to 10a and 60v

Correcting myself: 10a and 90v output. Can be powered from between 10 to 60v dc.

 

[cyclebuddy]

... a 250w pure sine wave inverter will be more than enough but still much heavier and less flexible in the motorhome and much more expensive than the simplest option of the mppt 7210a unit I suggested before.

Mmmm. I do get both arguments... Yes, the MPPT/7210 idea is more direct and has lower conversion losses, but...

Your 7210 at £28 weighs 480g. The Bestek 300w pure sine-wave inverter costs £40 and weighs about 600g. It's physically not much bigger either. I personally do also have an MPPT solar set-up in my van, but I still find an inverter in a mobile home/camper to be a far more flexible solution in that it powers a multitude of normal household devices, rather than the DC-DC converter idea which powers just a very limited number of low-voltage DC ones.

The other issue with a DC-DC converter: my e-bike batteries need a five-wire charger connection, not just a straight 42v+/-... so a DC-DC converter isn't a workable solution for everyone.

 

[wheeliepete]

I notice that the OP has a Yamaha battery, so the MPPT solution is prob. not going to work for him as I'm sure they have multi wire connections on them,(please correct me if I'm wrong) so will need to go the inverter route.
As D8veh says, there's no golden rules to suit all. This is a great example of that statement.

 

[Deleted member 4366]

I notice that the OP has a Yamaha battery, so the MPPT solution is prob. not going to work for him as I'm sure they have multi wire connections on them,(please correct me if I'm wrong) so will need to go the inverter route.
As D8veh says, there's no golden rules to suit all. This is a great example of that statement.

Yes, that only works for Chinese type bikes. Shimano, Suntour, Transx, bosch, Yamama, Brose, Giant, Kalkhoff, Bionx, etc are all out. Bit of a bummer really. Another reason not to buy one of those bikes, where a spare charger is going to cost £100.

 

[cyclebuddy]

Another reason not to buy one of those bikes, where a spare charger is going to cost £100.

I do agree with you. But when even a basic camper van costs upwards of £40,000, is £100 really an issue?

 

[Danidl]

There are grand big textbooks going under the titles of invertors and convertors. . The usual terminology is that a convertor converts a DC voltage at some voltage into a DC voltage, at some other voltage, either bigger or smaller depending..
An invertor on the other hand converts a DC voltage into an AC voltage at some frequency.

There is of course no need to use electronics to alter an AC voltage from one level to another voltage level at the same frequency as a simple transformer will do the task perfectly well....
Any of these conversion processes will never be 100% efficient, and achieving more than 90% to 95% is difficult.
If a number of these processes must be carried out in sequence, the overall efficiency is the product of each stage efficiency so will drop very rapidly.

Since i assume that all the contributors knew all this, why have we had 38 postings?.

 

[cyclebuddy]

There are grand big textbooks going under the titles of invertors and convertors. . The usual terminology is that a convertor converts a DC voltage at some voltage into a DC voltage, at some other voltage, either bigger or smaller depending..
An invertor on the other hand converts a DC voltage into an AC voltage at some frequency....
Since i assume that all the contributors knew all this, why have we had 38 postings?.

You have answered your own question... there are two ways of answering the OPs dilemma: You can use an Invertor, or a DC to DC convertor. Both have advantages and disadvantages. Stored power in an off-grid mobile/camper situation is precious, but the less efficient method has some advantages. That's what the debate is about.