Solar trickle charging

[ChrisCM]

Hi!
I have 2 folding pedelecs which we keep down in our apartment in Spain. There is often a 3-4 month gap between visits, I obviously charge them fully after use and before I leave but I'm worried about the self discharge between visits. When not there the power in the apartment is switched off so I can't leave them on trickle either permanently or via a timer.
Currently I am travelling to Spain by car so I am bringing the batteries and charger home to the UK where I can maintain them correctly, but I will soon be flying down and back and as you are probably aware Lithium Ion batteries cannot be carried on an Aircraft so I will need to find another solution.
What. I do have is an 80w solar panel plus regulator, a 75Ah leisure battery and inverter. My batteries are 24v 9Ah, the supplied charger has an output of 29.4v at 1.5A. My inverter is a 250W unit . By my maths there should be sufficient output from the inverter to power the chargers (29.4 x 1.5 x 2 = 88.2W) even allowing for loses.
Obviously the solar panel is only 80W but I would hope that the current draw by the chargers when trickle charging is a lot less than the maximum rated output would draw. Hopefully the charge in the leisure battery would be enough to power the chargers overnight with any excess solar energy during the day re-charging the leisure battery.
Has anyone got any views on my problem/suggested solution?

Thanks,

Chris

 

[Deleted member 4366]

Don't trickle charge them .Lithium batteries are not like car batteries. They get damaged if you over-charge them. They should be OK for 3 months. I, ve got batteries that haven't been charged for a year.. The other thing you shouldn't do is leave them in a discharged state.

 

[ChrisCM]

Interesting - I thought it was ok to leave the charger plugged in and connected more or less permanently (even though I have never done so), I usually plug in and charge overnight so it may be plugged in for a couple of hours after reaching full charge.
The reason for my concern about keeping them charged is the warning label on the batteries telling me to charge them at least once every 3 months.

Chris

 

[Deleted member 4366]

The charger charges to 42v, then the bleed resistors bleed the cells down to about 4.15v each to balance them. They get quite hot for a few minutes whilst bleeding. If you left a 42v trickle charger on, they would get very hot, especially in Spain.

 

[ChrisCM]

Many thanks, looks like I will have to risk leaving them, fully charged, for 3 or 4 months!. I suppose I can still be green and do a standard charge with the solar panel etc whilst I'm down there .

Chris

 

[Deleted member 4366]

Solar charging of an ebike is more or less a no-go. It can be done but it's complicated. If you already have substantial panels and a grid inverter, it would be better to tip your charge into the grid and charge your bike from the mains, otherwise it would probably be greener to forget about it, and just charge from the mains. There's been loads of discussion about solar charging, but I haven't heard of anybody that does it other than a few with specialist knowledge.

 

[ChrisCM]

Oh well, there goes that idea!
Re your previous post re the charging , my charger only had a simple co-axial plug to connect to the battery, does this mean that the control electronics are contained within the battery, the charger is labeled Type 2 with no manufacturers name on the battery or charger, the bikes are Connect Coyotes from Halfords.

Chris

 

[Deleted member 4366]

It's fully automatic. The charger has its own control electronics, plus the battery is protected by the BMS.

 

[ChrisCM]

Ok, thanks for all the info, much appreciated!!

 

[flecc]

Although I wouldn't remote charge batteries, since you are prepared to do it there is a way.

Just leave the charger and battery plugged into the mains via a GSM switch and remote control it by mobile phone. You could then switch on for a couple of hour charge top-up at the two month point of your four month absence.

The one on this link operates in Europe and at 110 to 240 volts. It's got the UK 13 amp base but I would think there are other versions available at the other end or you could use a jumper lead adapter.
.

 

[ChrisCM]

Thanks for the link, amazing what you can get now, and the price??? It's a wonder it's cost effective to produce and ship them here!

Something to think about.

Chris