Technical section question re charging.

[fatts]

Hi,
I have a trailer, big box one and as a project was going to turn into a chaging point for 4 electric tricycles and carriage of said tricycles.
All tricycles are 36v 10 0r 15ah sla's.
Now my question is, I know can I wire solar panels in series to form 36v and agm batteries in series to do the same but would I get a control panel ( I think thats the name ) and a charger that would take a input of 36v and same output.

Or will it lead to loss slower charging etc and panel size to cope?

Or stick to panels and batts in parallel and use inverter and normal charger that comes with bike.

many thanks in advance for any help.
Fatts

 

[Old_Dave]

Just off the top of my head ... why 36v, have a large capacity 12v battery charged by split charging from the towing vehicle and then use inverters for the normal chargers (if the chargers will work on the less than perfect sine wave that the inverter outputs).. you could then top up the battery with 12v solar which maybe more cost effective ?

 

[rog_london]

It's a bit complicated - sounds simple but isn't.

Generally 12 volt solar panels come with suitable controllers so you can attach a 12 volt battery. These generally voltage limit to maintain a fully charged battery without overdoing it even if the solar panel is in full sunlight but the battery has a full charge.

If you connect the panels and batteries in series and attempt to run a 36 volt system you can run into all sorts of problems which can be expensive - the sort of thing would be that the controllers can get very confused, not to mention overloaded. Think about one panel being in shadow and the other two in full sun - the one in shadow would 'see' 24 volts-plus from the other two and it and its controller might not survive that. The safest way would probably be to connect the batteries in series but don't attempt to do the same for the panels themselves or the controllers - in other words, one panel and one controller per battery, and then series the batteries. As long as your connections are well made you shouldn't have a problem with that.

As to dedicated chargers - the only manufacturer I know of which supplies a low voltage charger (at some expense) is Wisper, and it's a 12/14 volt to 42 volt job I believe. Most 36 volt ebike batteries need a 42 volt basic charger supply in order to have enough 'overhead' to charge a 36 volt battery.

So - if you get 36 volts it won't be quite enough and you're only likely to get enough overhead (42 volts) when the solar panels are in good light.

Your simplest solution would definitely be to stick to 12 volts and use an inverter so you have a pseudo-mains supply for charging. Even those can be troublesome because they don't like poor power factor loads - if you've used those inverters, you'll probably know they don't seem to like certain loads which should in theory be well within their capabilities - some laptop and smartphone chargers spring to mind, and also cheap and nasty Chinese energy saving lamps. It's to do with power factor. You'd almost certainly have no problem with a Kalkhoff ebike charger on an inverter (a good power factor), but some (maybe most) other manufacturers' Oriental chargers might be a problem.

I hope that's helpful and not too confusing!

Rog.

 

[morphix]

An interesting eco-friendly idea fatts, I'd be very interested to see some pics if you do decide to go ahead with your unusual solar project.. I'm interested in all things solar power.

 

[Deleted member 4366]

Why can't you use three 12v solar panels that come with charge regulators and charge the batteries directly at 12v each. All you need then is 6 additional wires and three connectors (per bike). This seems a lot more simple than messing about with inverters and mains chargers with all their efficiency losses.

 

[rog_london]

Why can't you use three 12v solar panels that come with charge regulators and charge the batteries directly at 12v each. All you need then is 6 additional wires and three connectors (per bike). This seems a lot more simple than messing about with inverters and mains chargers with all their efficiency losses.

I was assuming, from the nature of the question, that Fatts might not want to open up batteries in order to take taps from them and attach solar panels. Not everyone is up to that. It's also possible that the 36 volt battery might not split conveniently into three exactly equal parts, and you'd need to consider what to do about any BMS which might - probably would - be fitted.

The solar panel regulator/controller would be set up for a dryfit lead acid battery. The lithium battery probably needs slightly different treatment.

Your idea of what's simple is certainly different to mine!

Rog.

 

[fatts]

Thank you for your suggestions,
It would appear keeping them at 12v and having a decent pwm inverter in place and charger is possibley best
I shall look into the wisper 12 to 42v charger though.
All the bikes are 36v 10/ 15 ah and the sla's are in the case so I did not want to take the cases apart.
I understand I need 42v for charging.
Morphix I will do a photo file as I go. I wont be using the trailer now as that has to store my 6 Bmx Chariots ( bmx with sidecars ) as of now. So I will use a Vwlt35 I got given and after much welding i nearly ready for mot.
Now to start reading up what size panels I need, time for brain fugg
again many thanks
Fatts

 

[rog_london]

Keep an eye on Maplins. They do some good discounts from time to time and those 60 watt panels are a useful size if they're on special offer. This is a good time of year to be looking for heavy discounts on solar kit because obviously in our wonderful climate they won't be much use until the middle of next year - if you're lucky. Obviously also you need to factor in a lead acid battery for the solar panel(s) to charge, and a wet battery (car or truck) will come in much cheaper than an SLA of similar storage capacity. If you're hoping to maintain several bikes (you mentioned four) you either need lots of good sunny weather or several 60 watt panels. A good rule of thumb for what you might need for a charge would be to take the watt-hour rating of the battery in a bike and add on 40-50% to allow for the three losses in the system: (1) efficiency of the inverter - 90% driven hard if your lucky (2) efficiency of the bike's charger - probably around 80% - and (3) any battery doesn't give back as much as it takes in - could be 90% but generally much less due to the heavy discharge currents when riding.

I'll let you figure out some ballpark statistics when your 'brain fugg' clears! It won't be accurate but at least you'll have something to be going on with.

I've just noticed something I'd missed - your bikes all have SLAs. Some of my points might not be entirely relevant, though generally most of it would be. No BMS for one thing, and splitting into three equal parts for another..... Sorry d8veh - not such a bad idea because of that but at least I got it right that Fatts didn't want any extra semi-permanent wiring on the bikes/trikes themselves.

Rog.

 

[jhruk]

You may find this YouTube video of interest. I rather liked the idea of modifying a normal cheap mains charger to accept the supply direct from the panels, thus avoiding the cost and losses in an inverter.

 

[Deleted member 4366]

I was assuming, from the nature of the question, that Fatts might not want to open up batteries in order to take taps from them and attach solar panels. Not everyone is up to that. It's also possible that the 36 volt battery might not split conveniently into three exactly equal parts, and you'd need to consider what to do about any BMS which might - probably would - be fitted.

The solar panel regulator/controller would be set up for a dryfit lead acid battery. The lithium battery probably needs slightly different treatment.

Your idea of what's simple is certainly different to mine!

Rog.

Fatts said that they're SLAs at the beginning of his first post.

 

[flecc]

I think you'll find Fatts said the tricycles were both types, 36 volt 10 Ah and 3 x 15 Ah SLAs, hence him needing a 36 volt charging facility, the 36 volt 10 Ah presumably being a lithium or NiMh battery

 

[fatts]

Sorry for confusion what I meant to say was they are between 10 and 15ah packs but all sla's. I have some at 10, 12 and 15

 

[flecc]

Thanks Fatts, that clears things up. Best charge everything at 12 volts as d8veh suggests then, avoiding all the complications.

 

[rog_london]

Thanks Fatts, that clears things up. Best charge everything at 12 volts as d8veh suggests then, avoiding all the complications.

Now *I'm* confused!

Rog.

 

[rog_london]

Fatts said that they're SLAs at the beginning of his first post.

He did! I missed it. I did apologize.

It's bloody hard work in here at times, isn't it? Anyone want a job in tech support? I'm told the climate is better in India than here. I must just cultivate my impenetrable Mumbai accent.

Rog.

 

[oigoi]

Fatts I will tell you of my experiences with solar charging and hopefully it will be helpful to you.

I have a 24v solar power system, big lead acid batteries (total 525ah @24v)

I can tag onto it a pair of 28ah 12v agm batteries in series at 24v. It will charge them up but to get a really full charge into the two 28ah batteries the solar battery bank has to be full, causing the charging voltage from the solar panels / regulator to go up high enough to charge the 28h batteries fullly.

If the solar batteries are a bit flat and I tag on the two 28ah agm batteries then the agm ones do not get fully charged as the solar batteries soak up almost all the charging current.


The idea you are trying to achieve, to charge numerous trikes from a solar power trailer, has numerous areas that can be an issue.

The issue of whether you charge at 12v or 36v is not really significant in my opinion. For simplicity of wiring I would buy a 36v regulator and plug in each bike with just two wires. BUT:

1) I would only charge one bike at a time or the bike with poorest batteries will hog more of the charge.
2) You will only get a full proper charge if it is bright and sunny to give you a high charging voltage
3) you would need a switch to disconnect the panels from the regulator before you disconnect the trike's batteries or the power coming from the solar panels will damage the regulator's input

3) If you want to charge more than one bike at a time stick with the method of using an inverter and using the trike's normal mains charger. Most mains chargers are the SMPS type and will work fine on an inverter in my experience

4) Using an inverter on a 12 or 24v battery (about 100ah?)charged by the solar panels also gives you the advantage of being able to charge the bikes on a dull day using the charge stored in the battery

Hope this helps, feel free to ask any questions I have done quite a lot with solar power, best achievement to date is running a 180amp mig welder on it. Welding by the power of the sun!

 

[fatts]

Thank you for that oigoi, I shall take you up on your offer of advice a lot of help has been forthcoming.
I have now seen step up voltage things with variable input and output volt adjustment, so I can adjust to 42v for charging purpuses from 12v with various ah output approx 1/2 to 3ah dependant on model and I have been advised by a friend to keep a couple of battery packs in reserve for events incase of bad weather. The easy part was the 3 tricycles I have various batteries and packs so can make up a spare one or two and also a couple of spare powabyke wheels which will need respoking and new rims from Frank of Powabyke. Even the van I am putting to use was given to me to do as I wished was heading for the scrapyard but with welding done by a friend its nearly ready for the road, all good recycling eco footprint etc.
The solar panel sketch scares me as in what size to buy, where to source cheaply
The battery welding I first come accross about 12yrs ago in the wilds of Wales when the gear lever snapped on our coach on way to Glatonbury festival a mate came out with a couple of batteries, jump leads and welding rods and away we went after he welded it.
regards
Fatts