Charging on a trailer

[Alibee]

Hi all,

Was wondering if anyone had experience of charging something on a trailer via the switched supply (pin 10 on a 13 pin setup)?

We're designing and building an eMTB trailer, which will have 1 or 2 car batteries on it, to charge 3 bikes via an inverter, and looking to charge the car batteries while driving. Ideally we would charge them directly from the same feed that charges the leisure batteries (so they would charge under hook-up) but I'm not sure if that is possible / advisable or even tolerated on a vehicle still under warranty.

We're also looking to have a separate 16A hook-up on the trailer, complete with battery charger and bike chargers, as charging 3 x 36v batteries (4A chargers) will obviously place a lot of drain on the system.

 

[MattBW]

Easiest least invasive way would be to get a cheap hookup splitter and have a separate hookup cable for the trailer from the same feed?

To charge whilst driving may be more difficult but is doable.
The batteries would need to be the same voltage to avoid the full ones discharging into any that are emptier. Based on your usage that may not be feasible. If you get them all permanently into one circuit then they could be charged and discharged as a bank but each battery must be identical capacity and at the same level of charge to be effective.

The best bet may be something like a sterling battery to battery charger which will put any excess charge from your existing circuit into the trailer batteries when required.

 

[soulstyledevon]

Agree with Matt.
Probably best to have a separate supply & batteries on the trailer.
What about solar panels on the trailer roof to charge trailer batteries...?

 

[Loz]

Also buy the 12V version of your e-bike chargers to cut out the need for the inverter.
Or create a charger carrier inside the vehicle and use 12v chargers...

 

[cbdubs]

If you did use a 12v charger, could you not just run a permanent live and earth off the tow vehicle using a caravan socket like you would for a fridge? Don't know, just a thought.

 

[Alibee]

If you did use a 12v charger, could you not just run a permanent live and earth off the tow vehicle using a caravan socket like you would for a fridge? Don't know, just a thought.

This would be an ideal solution but we cannot source a 12v charger (let alone 3!) for these bikes. One exists, but no one has stock anywhere, nor seems to know how to get them. This is the correct charger but has the wrong connector for our bikes:

https://www.ebay.co.uk/itm/Modiary-...Akkus-Rundstecker-DC-2A-Ausgang-/253533271845

Our bikes use the RoPD connector that seems to be becoming the de facto standard for eMTB

Unfortunately, it's not as simple as changing them over as the data cables need to be active to tell the bike to start charging.

So, at the moment, we're stuck with having to replicate most of the Cali electrics in the trailer! This is not all bad news, as it will allow the trailer to be used by other cars (there are three of us involved in this) so the investment will at least be shared across many uses.

@MattBW - great call on the Sterling charger. They look just the job, even if they are bleedin' expensive!

@soulstyledevon - already plan to have at least a 12v trickle charging solar panel, but actually have a spare boat one available if I can work out a schema that won't break anything!

Thanks all for the input, definitely making progress.

 

[soulstyledevon]

Report back.
Its an interesting idea, would love to see the finished article

 

[Loz]

Our bikes use the RoPD connector that seems to be becoming the de facto standard for eMTB

We have the Bosch systems with the 4 blade plug and fortunately there is a 12v version of our charger but we are just using the mains charger on hookup..

 

[Alibee]

We have the Bosch systems with the 4 blade plug and fortunately there is a 12v version of our charger but we are just using the mains charger on hookup..

Yes, the Bosch system seems to have much better accessory support (perhaps unsurprisingly).

We have Focus bikes, but the charger is the same as the Specialized / Raleigh / Kalkhoff / Univega ones too. I have a slim hope that the manufacturer may be able to provide something, but our next major trip is in early April so not much time to find the solution.