Help with my Lithium Upgrade

[TheCartBoy]

If the heater wire is essentially a resistor, you should be able to use it on 48v DC directly. It will be a bit less than half the watts. Try it with a bench supply.
You could then convert your 120v AC to ~60v DC using a single diode (half bridge rectifier) so that either power source is close to the same watts on the heater wire.

[davros]

McMaster has a line of silicone heater mats, have used them

[Murby]

Originally Posted by TheCartBoy

If the heater wire is essentially a resistor, you should be able to use it on 48v DC directly. It will be a bit less than half the watts. Try it with a bench supply.
You could then convert your 120v AC to ~60v DC using a single diode (half bridge rectifier) so that either power source is close to the same watts on the heater wire.

That's what I was thinking.. Just plug it into battery voltage directly.. it won't be as powerful, but if I'm parked at a friend's house for a few hours in really cold weather, it should be good enough..

[Murby]

Originally Posted by Capt. Lenny

Here's an interesting 12 volt option for warming lithium batteries.
https://justalittlefurther.com/just-...ttery%20warmer

I considered those.. and a few other 12v series heaters. The problem is the watt density. Squeezing 25 watts into a 3 inch silicone heater means that pad is going to get HOT.. really hot.

What we cold weather lithium folks need is a 48 volt silicone heating pad that puts out no more than 1 watt per square inch, and preferably about 0.5 watts per square inch.
If we could get a 60 watt silicone pad that matches the 12 x 12.75 foot print of the standard 48v 105ah lithium golf cart battery, we'd have a good product.

With some 1/2 inch EPS foam board on the sides of the battery and the silicone heating mat on the bottom, the battery would heat up evenly with no hot or cold spots.

All the heaters on ebay and amazon are up in the 5 to 7 watts per square inch range.. I can't see how they could NOT damage a battery, and these would certainly melt a plastic case..

[Camaro69]

I'm just starting to look at converting to Lithium, but wouldn't it be better to purchase a Lithium battery that is self heating?

[Murby]

Originally Posted by Camaro69

I'm just starting to look at converting to Lithium, but wouldn't it be better to purchase a Lithium battery that is self heating?

Maybe, but I don't know of any reputable brands that have a self heating feature with a 250 amp continuous output BMS.

Also, I don't want to have to keep the cart plugged in and charged to 100% all the time just to get the heaters to work.

The way I'm doing it, I can choose between grid powered heating, grid powered heating+charging, or battery powered heating.

My cart works on a farm and it works all year long through cold winters.

[Murby]

So here's the latest update..

I tried using the gutter deicing cable, it works well, but there's no way to wire it without making a huge mess. The stuff is stiff as fiberglass rod..

So I got on Amazon and ordered some 12v 25 watt silicone heater pads.. put them under the battery on the corners. Wired in series, hooked them to a 48 volt power supply and let them do their thing. They work well!! Very well!

Now my problem is controlling them. No one makes a 48 volt controller for that purpose.. Even the SSR relays are 3-32VDC input.. and anything I can find that works at 48vdc is either limited to 48vdc (on a 58 volt battery), or they cost $400.
Tried looking for a digital temperature controller.. They're either AC input, or 12/24v input.
WTF is going on? All these 48VDC systems out there from solar power batteries to electric golf carts, and no one sells stuff designed for 48 volt power?
Even checking Mouser and Digikey, their 48 volt coil relays can't pass 48VDC through the contacts.. I'm stunned..

Solutions? I don't want to put something on that battery that is going to continuously draw juice when it's not needed.. And I don't want to turn it into a messy Rube Goldberg device with power converters, step up/down boards, and a whole bunch of other crap..

[TheCartBoy]

I've used those cheapo 120v temperature PID controllers, it just toggles a relay to turn the heater on, so that would work fine for your 48v DC load.

But since you want the controller to run on 48V, that seems more limited options of off the shelf products. For lithium batteries that have this feature, it would be built into the BMS itself.

https://a.co/d/h8XZpcP
Here's a fan controller that says it'll run on upto 60V DC, has temperature probes and is configurable. The output for a fan is way less current than your heaters, so you should use the fan output to activate a relay instead, which will supply power to the heaters.

Rube Silverberg?