Is it safe to connect a 40W elecric blanket to my ebike battery?

[guerney]

For cold days at my remote garden, I'm wondering if it's safe to connect this 40W electric blanket (they've changed the listing to king sized and 70W, but I bought a single):

Pardon our interruption...

...to my 36V ebike battery? Would the battery explode or be damaged?

 

[Nealh]

One would need to use an inverter (36v to240v) , then think about how much it will take out of the battery to allow you to get home again. Too much heat/power will be lost during conversion of the volatge.
Might be better with a 12v 55w blanket and a seperate 12v LFP but cost would be over £200 to set up.

 

[guerney]

Thank you - I'll look for a suitable inverter - it'd only be for about half hour at most, to get sufficiently warm on extremely cold days, to continue gardening or ride back. Perhaps 0.167 amps, plus a bit of loss in the conversion (?) might not be using much? I get at almost twice the journey to my garden and back from my 19.2ah battery, and if it goes flat... there's the bike fold and bus option.

 

[Nealh]

The easiest route may be a 12v rated blanket and a sealed /cased 36v - 12v buck converter, both will cost about £35.
A 240v inverter will be over £100 and bit heavy to lug about.

 

[guerney]

The easiest route may be a 12v rated blanket and a sealed /cased 36v - 12v buck converter, both will cost about £35.
A 240v inverter will be over £100 and bit heavy to lug about.

What an excellent idea! According to the reviewer, this:

https://www.amazon.co.uk/ELECTRIC-BLANKET-MOTORHOME-CARAVAN-CAMPERVAN/dp/B00DSPGHAQ/ref=

"Draws 3.4A at 13.2 V, so the 50 Watt rating is about right, at 12V. "

Which is about equivalent to the one I'm using right now, on the back of my office chair keeping me warm. Thanks a lot Neal, that's brilliant. Plenty of high power 12V converters on ebay and AliExpress - with a space blanket on top, plus a duvet/sleeping on top of that - the heat really builds, that's such a rapid and cheap way to get warm.

 

[Nealh]

DC-DC Step Down Buck Converter 36V/ 48V to DC 12V 25A 300W Output Aluminum NEW | eBay

 

[guerney]

I've got to say, the prospect of being able to warm my feet to a high temperature in a freezing cold garden shed, has got me very excited - my feet get mad cold on longer winter bike rides no matter what I do, start cramping, as do my calf muscles. Sometimes it's so bad I have to get off and walk for a bit. This way, I'll be ableto give my legs a good roasting!

 

[cyclebuddy]

I've got to say, the prospect of being able to warm my feet to a high temperature in a freezing cold garden shed, has got me very excited - my feet get mad cold on longer winter bike rides no matter what I do, start cramping, as do my calf muscles. Sometimes it's so bad I have to get off and walk for a bit. This way, I'll be ableto give my legs a good roasting!

I don't think the 12v blankets are up to much; there are plenty of reviews of all types on YT, many from Van Lifers (those living permanently in vans). My take is that 50w isn't much by way of heat output at all, and hardly any 12v ones have any option to adjust heat (at best it might be high/low/off).

I recently bought a 150w mains powered blanket/throw (£50 off amazon, but prices have increased dramatically with the onset of cold weather - it's now £70). Even then, a minority complain of it not being very "hot", although I find it toasty enough.

I'm running a 120w buck converter off my e-bike batteries. That's a 10A draw which is okay for my not exceptional e-bike cells. That provides 120w at 12v, and then I can optionally feed USB and/or a 240v inverter: That's fine for powering my laptop or charging my phone, but this lower powered 10A buck won't power my 150w blanket:

That's because this 150w blanket has 10 heat settings: On full heat, it's drawing 150w as you'd expect (too much for the buck), but at lower settings it pulses at 150w, the lower the heat setting the less frequent the pulse. But in all cases, it's still a 150w draw - too much for my 10A buck (and battery cells).

The 25A buck Nealh lists seems a good higher powered option so should work with a decently heated mains blanket/throw (or heat pad if it's just your feet that need warming), but can your battery cells cope?

 

[guerney]

The 25A buck Nealh lists seems a good higher powered option so should work with a decently heated mains blanket/throw (or heat pad if it's just your feet that need warming), but can your battery cells cope?

That's a good point, and I'll test it before connecting to the converter via a fuse, using another power adapter plugged into the mains, to see how true this reviewer's comment is ie:

"Draws 3.4A at 13.2 V, so the 50 Watt rating is about right, at 12V. "

My battery is quite happy at present supplying 15A, and with LG MH1 cells should be capable of up to 25A, but the BMS is limited to 22A. 3.4A should be fine.

I don't think the 12v blankets are up to much; there are plenty of reviews of all types on YT, many from Van Lifers (those living permanently in vans). My take is that 50w isn't much by way of heat output at all, and hardly any 12v ones have any option to adjust heat (at best it might be high/low/off).

I recently bought a 150w mains powered blanket/throw (£50 off amazon, but prices have increased dramatically with the onset of cold weather - it's now £70). Even then, a minority complain of it not being very "hot", although I find it toasty enough.

I agree that a 50W electric blanket isn't likely to warm much on it's own, but with a space blanket plus a good insulation layer (13.5 tog duvet) (with insulation layer, is when space blankets work best) 40W seems sufficient in a very cold room at home, gets warm... but it does take some time to build up. I think it's quite likely to do the job and will give it a go. Adding a space blanket layer to a duvet or sleeping bag is transformational, even without any additional heating.

I also have a 1ltr flask full of boiling water for my gardening stints, and an empty hot water bottle to fill when needed...

 

[soundwave]

https://www.amazon.co.uk/Highlander-CS036-Survival-Bivi-Bag/dp/B003H0XGC4/ref=sr_1_1_sspa?adgrpid=61639061508&gclid=Cj0KCQiA4uCcBhDdARIsAH5jyUlrWQrMVjGWDl52VgUYBomTWwSp1A6PGp_A2yttfZkxxGf4FsjCWs8aAuMsEALw_wcB&hvadid=606109737599&hvdev=c&hvlocphy=9045572&hvnetw=g&hvqmt=e&hvrand=13805982641193504755&hvtargid=kwd-296471098734&hydadcr=1949_2253620&keywords=bivi+bag&qid=1670939146&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1&smid=A2QODR4IZFO7VH

you can get in that and sleep outside

 

[guerney]

Mylar will only reflect radiant heat, but we only lose about 50% of our heat due to radiation. If Mylar truly reflects 80%, that's only 80% of 50% = 40%. Therefore for more warmth, you need an insulation layer. Adding even just 40W, makes a net positive difference, or seems to thus far.

 

[guerney]

https://www.amazon.co.uk/Highlander-CS036-Survival-Bivi-Bag/dp/B003H0XGC4/ref=sr_1_1_sspa?adgrpid=61639061508&gclid=Cj0KCQiA4uCcBhDdARIsAH5jyUlrWQrMVjGWDl52VgUYBomTWwSp1A6PGp_A2yttfZkxxGf4FsjCWs8aAuMsEALw_wcB&hvadid=606109737599&hvdev=c&hvlocphy=9045572&hvnetw=g&hvqmt=e&hvrand=13805982641193504755&hvtargid=kwd-296471098734&hydadcr=1949_2253620&keywords=bivi+bag&qid=1670939146&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1&smid=A2QODR4IZFO7VH

you can get in that and sleep outside

Cheers! An electric blanket placed inside that, could melt he snow on my driveway. In small stages.

 

[soundwave]

if you get in one of those in 10 mins you will be boiling

 

[chris667]

Oooh, boil in the bag bivi bags! I haven't seen one of those since I was a kid. Sleeping in one of those is a rite of passage as is swimming out and getting freezing cold when you wake up.

It seems like a lot of money to get the bits to support heating yourself electrically with a little battery.

Why not take a thermos of really hot water, then use it to fill a hot water bottle when you get there? It's a lot simpler and cheaper!

 

[guerney]

if you get in one of those in 10 mins you will be boiling

I've got a couple of 2M X 2M clear thick plastic bags of about the same weight, so I could try it, but I don't think it'll get me properly hot enough after a couple of hours of gardening in the freezing cold, without a heating element. For some reason, circulation to my calf muscles and feet is very poor these days.

It seems like a lot of money to get the bits to support heating yourself electrically with a little battery.

I was thinking of soldering a 12V DC converter and outlet to the ebike battery anyway, to add very bright rear lights to the bike trailer. Plus an electric blanket will come in handy in during a winter power outage, connected to my 19.2ah ebike battery. It'd be a game changer for winter cycling and gardening, if it all works as intended.

Why not take a thermos of really hot water, then use it to fill a hot water bottle when you get there? It's a lot simpler and cheaper!

Yes, that's my other solution as stated in post #9 - trouble is, I'd have to stay still for about 20 minutes for my feet and calf muscles to warm up enough for the ride back, during which time the rest of me will freeze... hence 12V 50W 3.4A electric blanket + space blanket + sleeping bag + woolly hat.

 

[Nealh]

Every one feels and suffers fromt eh cold differently so one can only try out solutions to see if they work , excuse the pun but a blanket reply will not suit everyone.

Prior to my poorly feline being put to sleep last winter ,I used a 80w heat pad for him. The heat pad only produces decent heat affect/output if it has something laying on it/or is in close contact to the body , I placed an carpet section underneath and as well so the cold floor directly wasn't be heated and a fleece thin blanket between my boys bed and the heat pad .
Often even with the heat controller on low he moved off it as it got to warm for him.

The 12v 50/55w heat blanket and the mylar on the outside of the blanket might work well.

 

[Nealh]

What you need is a little camp fire going whilst you work then a little sit by it to toast your feet.

 

[guerney]

The 12v 50/55w heat blanket and the mylar on the outside of the blanket might work well.

If that's not enough - I'd be comfy and warm in a blizzard, if I put the whole lot into one of @soundwave 's bags, plus another mylar space blanket between me and the sleeping bag as a lining, over the electric blanket. And add a second electric blanket if necessary...

 

[chris667]

I've always wanted to try one of these:

Särmä TST Thermal Cloak - Varusteleka.fi

This multi-functional thermal cloak can be used as a cloak, sleeping bag and emergency shelter even in extreme weather. Fast international delivery!

www.varusteleka.com

 

[matthewslack]

When I lived in a ruin, a few years ago, I built a room within the ruin 10ft square and 7ft high with a foot of cheap rockwool insulation on all faces. With good draughtproofing too it only needed me and my laptop to keep it warm.