Can i Go Solo with solar

[elm70]

"pushing current directly into the battery" is not a very good idea at all with a Li-Ion battery. It will lead to overheating, batteries brewing up and possibly fire and explosion. Witness the Boeing 787, Samsung 7, and ~ Mitsubishi PHEV woes in that respect.
(The first 4000 PHEV vehicles were pulled off the road for batteries overheating, production was held up for two months for a redesign)

:ugeek:

When we are speaking of pushing max 1amp (possibly with solar 0.5A or less is more realistic) in the battery back , that has 40Ah cells .. this should ever ever be a problem if the battery pack has been properly designed.

Now .. control the charge from outside .. it means nothing .. absolutely nothing.

We have 80 Cells in series .. and for how good is japanese QC, each is slightly different, with different capacity and behaviour under load or charge ... so the battery puck .. MUST HAVE .. a system for balance these 80cells ... in ideal situation the voltage of these cells should be always the same, but it is mandatory that his happen when the voltage is approaching the MAX and the MIN allowed ... especially in faulty case when the MAX voltage is exceed , it is when bad thing can happen.

For example .. you can have a pack with all cell at 3.9V .. but one with 4.2V (or 4.1V is the max for these Lithium battery) ... anyhow ... charging from outside .. at best it can be seen the max voltage of the battery pack ... so .. it may look like that fast charging is still allowed .. but in reality charging should be stopped .. since one cell is on the edge to be overcharged.

Note: I'm coming from the usage of LiPo battery in RC hobby since over 15 years ... in the RC hobby world .. the common charger for Lithium battery have a balancing handling included .. some smart battery may have integrated balancer (but in the small scale and price and lightweight optimization, it make little sense and small usage) .. what it is unknown here is how the balancing happen , since it is definitely mandatory, for safety and for efficiency ... so the most important aspect ... it is hidden ... and it is not part of Chademo or J1772 since balancing is not part of Chademo or J1772

BTW .. charging LiPo .. is very very easy ... they can take up to X amp of charge ... does not have to be constant this charge ... only issue ... is that each cell should never be above X voltage ... it does not need a big science for it .. and there is no risk at all when these two limit are kept under control.

Clearly ... at high amp charge ... cell temperature can play a role, and it need to be controller ... anyhow ... if cells are getting warm under charging .. in my book we are already "ageing" the battery (this is why we should not use high amp charging on this PHEV, since clearly these cells don't like high current charging) ... Tesla that is "power" oriented ... they have integrated cooling in the batter pack .. since they want to charge and discharge fast the battery .. for performance and for fast charging .. two aspect that don't really apply to this PHEV, and absolutely are not in the scope of a portable solar panel charger

PS: From my LiPo hobby RC charging .. I'm normally never charging faster then 2h .. or at best I go to 1h for 80% charge .. in other word , if the battery capacity is 6Ah .. I would not normally charge over 3A ... or if I'm in time pressure .. I use 6A (it is also called 0.5C charge or 1C charger) ... so .. at 0.5C charge and as well at 1C charge .. never my battery got any difference in temperature (this is different then NiMh cells, that are always getting warmer at the end of charging process) ... Lithium battery get hot ,in my case, only when discharged fast (if I use them for have 10 or 5min fly time .. it means I discharge them at 6C or 12C) ... anyhow .. each battery has its limit ... but a good indicator of "ageing" ... it is to make the battery warmer ...

 

[jaapv]

The balancing is probably handled by the software on fixed parameters, as Mitsubishi offers a rebalancing service.

 

[elm70]

The balancing is probably handled by the software on fixed parameters, as Mitsubishi offers a rebalancing service.

Balancing should happen at every charge ... else ... it is a very bad design

Where I can find info about this service ?

 

[jaapv]

At your dealer. They call it öptimizing the Battery Ï guess. I'll hand mine in in a few weeks, it takes overnight

 

[elm70]

At your dealer. They call it öptimizing the Battery Ï guess. I'll hand mine in in a few weeks, it takes overnight

Did you check the battery status before ask for this service ?

Via the specific apps you get exact voltage of each cell, if at full charge status they are all at the same voltage you are fine ... no need to balance them


Anyhow ...

Damned ... they are like 15 years behind the LiPo hobby usage in RC ... if this car does not have any balancing in place

This sound an additional good reason for get access to the battery pack ... balancing can be done also "manually" ... but it may take ages to be done manually for a pack of 80 cells ... still it is quite easy to "fix" the cells that have too high voltage compared to the others

My official dealer and service in Poland, possible has seen the PHEV first time today when I bring my car for make my 1st service ... I guess they have no idea how to balance the battery pack

I'm crossing fingers that they will put in the right oil ... I'm smelling they never got any stock of the special oil for this PHEV

 

[elm70]

Back to solar charging option.

I see that a 12V DC to 220AC capable of 1500w cost less then 50 USD. (J1772 charging allow as low as 6Amp .. that is around 1.3kw ... so 1500w DC-AC converter will make the job

So ... normal panel have no problem to charge a 12V battery

So what it is needed is a 12V battery capable to handle 100A discharge for few minutes

That means for practicality a 3S Lipo with 20Ah capacity ... something that should cost no more then 80 USD ... in theory a little 50AH LeadAcid could do the same job ... but it will be much more heavy ... again ... in theory it could be used the 12V car battery .. but it will be a bit "odd" the charging process

So the idea is following ...

A controller check the status of the 12V battery, and if voltage is less then X .. it will enable the charging from solar panel
Same controller check the status of 12V battery .. and if voltage is more then Y .. it will start power up the J1772 6Amp charger (is enough to switch on the DC-AC inverter)
Finally .. same controller check the 12V battery if battery is below Z .. and then it will stop the power of the car charger (switch off the inverter)

Plus one additional option ... a push button that allow to discharge the 12V down to W ... for flash out the energy accumulated in the battery before remove the solar panel from the car roof.

I guess the charging time should be around 5min .. that means release 110wh ... something that need around 20min for charge time from solar panel .. so every 20min the car get a 5 min charge

Now ... 300W solar panel should cost around 200USD ... Inverter is 50USD ... DIY J1772 6Amp is ~100USD ... Lipo 80USD .. and 10USD for controller ... plus some hardware for keep together the panels and stick on the car roof (20 USD)... so ... in total is less then 500 USD .. for get 2Kwh at best in the 8h of working while the car is on a sunny parking place

I guess it could have a market such a thing ... :ugeek: :ugeek: :ugeek:


EDIT : 500USD for a solar charge 300W for car .. capable of 2kw a day ... will get a ROI in just 2 years time
EDIT : The hobby grade battery for 80USD .. may have a short life to ... maybe 2 years ... setting 5min charge burst .. it means using only 8AH from the 20AH capacity ... so ... it can be configured to be on the sweet spot ... and 5C discharge is not to hard for a LiPo ... anyhow .. replace battery every 2 years of 500 days of usage ... is not a too hard thing ... still economically convenient ...

 

[zzcoopej]

plus some hardware for keep together the panels and stick on the car roof

I don't think the gains will be as much as you hope, as aerodynamic efficiency and weight will count against you.

How about this - think of "the grid" as a virtual battery. Install solar panels on your house and store your energy in "the grid", and then use this "stored" energy to charge your PHEV. It's by far the most cost effective solution today if your house is grid connected. Having the solar panels stationary at close to optimum angle to the sun and not on weighing down your PHEV and being shaded by trees you park under, building shadows etc.

If you don't have a sunny roof, you could look for a community solar scheme to subscribe to.

 

[jaapv]

Isn't it much simpler to park your car at a charging station? Plenty of those around.

http://www.oplaadpalen.nl/

Given that according to your figures you are going to get 1km/hour charge*, -if the sun is shining, a rare enough event in out climate- and that you will have an estimated 10% efficiency loss all the time you are moving due to the contraption on your roof, it appears to me that the net result will be negative.

*the car can charge 10 kWh and drive 40 km approx.

 

[elm70]

I don't think the gains will be as much as you hope, as aerodynamic efficiency and weight will count against you.

Added weight is marginal ... like 10kg/20kg of extra weight to carry in the car

Aerodynamic impact is none ... this is only to be used when car is parked, when not in use it will be stored in the trank

Isn't it much simpler to park your car at a charging station? Plenty of those around.

Definitely better ... but where are I am ... there is not such of plenty .. actually you can cant with one hand fingers the one available in 100km range

Anyhow ... having this "solar kit" ... it allow to park everywhere without bother .. clear it make sense only for parking outdoor