Charging e-bike from leisure battery: blown fuse

[Diveywivey]

Hi I recently bought a 12v charger for my van to charge my e-bike from the leisure battery (bought from the UK dealer specifically for this bike) when not plugged into a mains EHU. I plugged the charger into a 12v cigarette lighter style socket connected to leisure battery and a green light came on showing the socket was working. When I plugged the other end into the bike battery, the light went out and I appear to have blown the 7.5A fuse. I'm hoping someone with better electrical knowledge or experience of doing this can offer some advice e.g. do I need a bigger fuse? Is there an initial surge current that the fuse must cope with?

The spec on back of the chargers says:
Input DC 12-28v 100w
Output DC 42.0v 2.0a
LED:green <= 0.2a

Any ideas much appreciated. Cheers all.

 

[TallPaul_S]

100w divided by 12v is 8.3a.

So if it's trying to pull 100w from a 7.5a fused 12v socket, that's your reason!

I presume the 7.5a fuse is on the vehicle side, not on the charger? Swap out for a 10a - 12v sockets are OK up to 10a, anything more and you'll run the risk of melting them.

 

[Pete C]

Even at 8 Amps it will get hot - be really careful.

Pete

 

[Diveywivey]

Ah ok. Thanks for the swift reply. That makes sense. (For my own understanding tho, what about the 'output' numbers: do they suggest 42v times 2a = 84w output ? Or is it a case of 100w in and only 84w out cos it's '84% efficient' ?)

Obviously nervous about e-bike chargers generally after all the news items but it's supposedly a charger specifically for this bike from a reputable UK supplier (tho it's Chinese inevitably). We will carefully try out a 10a fuse and stay for a while to see what happens.

Thanks all

 

[Howzat]

The difference will be the inefficiency with the charger, spot on.

 

[Salty Spuds]

Cut off the cig plug & fit a small anderson socket/plug or similar, to the leisure battery via 10A fuse. You're very close to being dodgy as you are.

Search Results

Suppliers of high quality electrical parts, components & accessories for campervans, motorhomes, boats & off-grid applications.

www.12voltplanet.co.uk

 

[TallPaul_S]

Cut off the cig plug & fit a small anderson socket/plug or similar, to the leisure battery via 10A fuse. You're very close to being dodgy as you are.

Yeah was about to suggest this.

Get a set of 15a or 30a Anderson power pole connectors

Anderson PP15/30/45 Powerpole Connector Housing (1.5 - 6.0mm² cable)

Anderson PP15/30/45 Powerpole connectors for quick & easy connection of cables. Modular housings interlock & can be 'keyed' to prevent errors. 6mm2 cable max.

www.12voltplanet.co.uk

Hardwire 2 connectors to your LB, with the other 2x on the charger. Much safer and more secure, the connection won't work loose like a cigarette plug can.

 

[z1ts]

the connection won't work loose like a cigarette plug can

They do work loose and get hotter and hotter in the process - play it safe bud...!

 

[Diveywivey]

Hmm cheers all. It's all starting to sound like a bad idea. I spend most time on camp sites so perhaps I'll just stick to using the 240v charger off the mains EHU. Maybe I'll report this discussion back to the seller too for comment as it sounds like these things need a dedicated supply really. Thanks again.

 

[TallPaul_S]

Well, 'technically' a 12v cigarette lighter is capable of 15a.

But technically you can do a lot of things which really aren't a good idea!!

Tbh, having an Anderson connector hard wired into your system isn't a bad idea as it'll let you connect no end of stuff in a much safer way than the 12v socket, and connect stuff over the 10a limit - like portable solar panels.

Tbh if you're only using it on hookup then I'd stick with 240v. If you want to charge it when driving along then go for the Anderson connector route.

 

[Salty Spuds]

Well, 'technically' a 12v cigarette lighter is capable of 15a.

But technically you can do a lot of things which really aren't a good idea!!

Tbh, having an Anderson connector hard wired into your system isn't a bad idea as it'll let you connect no end of stuff in a much safer way than the 12v socket, and connect stuff over the 10a limit - like portable solar panels.

Tbh if you're only using it on hookup then I'd stick with 240v. If you want to charge it when driving along then go for the Anderson connector route.

I agree that cig lighters are rated at 15A, but that’s not continuous. Don’t forget that they were originally designed to be….a cig lighter. 15A for 30 seconds or so that it took for the lighter to heat up is waaay different to drawing 10A for hours. Personally I detest them & avoid using them whenever possible, the Hella type plug & socket is much better, but even then only good for 10A.