So I have a small diesel heater for my shed. It runs on a 12v automotive battery. I had a spare lawn and garden, 330CCA one around, so I use that. The battery will run the heater (consisting of some kind of igniter, a fan, a fuel pump, and an LCD control panel) for a few hours. I’ve been using an adjustable 30v / 5A DC power supply to charge the battery when not running the heater. It works fine, but there is nothing to charge the batter while the heater is running as would be the case in a car.
Can I leave the power supply charging the battery while the heater is also connected to and using the battery? Or is that a recipe for something bad to happen?
And while I don’t know what the current draw of the heater is, I do know that the power supply can’t run it directly. It almost works, but seems to draw just a bit more current than the supply can give and shuts down. It appears to draw the most current at startup, which takes about three minutes, and then settles into a lower operating draw.
And yes, I know that I can surely buy a 12v 10A power supply, but I get a kick out of making do with what I have lying around.
I’m having trouble getting the link to the actual unit to work, but this is essentially the same thing- in fact, I’m 99% sure it IS the same thing with a different name. I got mine through Amazon. Mine lists 15A in the literature, but I’m pretty confident it’s not actually pulling anywhere near that. Like I said, the 5A supply can almost manage it.
I don’t have any unfinished space in my house, so my only option for a workshop is my shed. I was running a propane heater, but it was causing a lot of moisture problems. This thing exhausts to the outside, and I’m very impressed with the amount of heat it makes
I’m really wondering what the battery is doing, here. If it’s a diesel heater, then presumably the heat should be coming from burning diesel fuel. At that point, the battery is for, what, a fan? Maybe a thermostat and controlling an actuator on the fuel supply valve? That shouldn’t be pulling 60 watts.
The heater’s power use will depend on its size, but generally, diesel heaters will use 8 to 12 amps during start-up, with some models then requiring as little as 0.5 amps to run continuously, and an average of 1-2 amps. Using a 12V power source, this equates to roughly 96–120W of start-up power, and then about 24Wh after that.
You should be okay keeping a charger on the battery at the same time as you use the device. The same basic getup is in use on cars, trucks, boats, motorcycles, generators, etc. all the time – load pulls current while the battery is charging.
Same with those Jackery and Bluetti power supplies, whether connected to 12V, 110V, solar, or a combination.
It’s either net charging, net neutral, or net discharging, depending on current in vs. current out.
I was wondering the same and why I asked if the battery alone runs the thing after starting. It might just be the glowplugs that are loading too much for the supply.
Right. That’s my guess as well. I referred to it as the igniter, because I have no idea if glowplugs would work in a setup like this (in a diesel ICE, once it’s going the compression keeps it going; in this case I don’t know how it works- is the flame self-sustaining?)
Once the ceramic glowplug is hot enough to ignite the fuel, the burning fuel keeps the glowplug hot, and it doesn’t need electrical power anymore; it just behaves like a candle wick soaked in diesel fuel. But you still need:
power for the controller
power for the fan that moves hot air into your living space
power for the combustion air fan
power for the diesel fuel pump
The fuel pump isn’t like the high-pressure common-rail pump on a modern diesel engine, which operates at tens of thousands of psi. OTOH, it doesn’t exactly seem to be dribbling fuel onto the glowplug; there appear to be distinct injection events at regular intervals, so it’s developing some fuel pressure (and consuming some electrical energy) with each injection event.
@DavidNRockies cites a source claiming 24 watts of power consumption once the ceramic glowplug powers down. Amazon lists some desk fans that are about 8 watts, so imagine maybe:
So last night I ran it with the battery, heater, and power supply all connected and it worked great. I could see from the power supply that we were net-discharging during startup, and net-charging during operation. So I think this will work well. At some point I’ll try running it off the power supply after startup, but based on its cooldown procedure, I worry a bit that if it were to shut down suddenly it wouldn’t be good for it.
That sounds real low for blowing 5kW of heat around a garage. I’m at work and just looked at a colleague’s fan next to her desk. It’s a little 10" floor pivot dealie, all plastic, and lists a .55 Amp draw, 60+ Watts. This one is similar and seems to be rated 30 W:
I recently discovered a nice workaround on this, very similar to what your application is. Well, I didn’t discover it, though I wish I had.
If you have a dedicated power supply controller that will run the heater, you want to float the battery. Ordinarily an automotive starting battery isn’t the best choice, here a deep cycle is suited for this purpose.
The problem with batteries and chargers and floating them is it is all temperature dependent. Everything is temperature compensated, electrolyte specific gravity, charging temperatures, open circuit voltages.
So let’s say your popular brand name gee-whiz bang smart charger ends up at 13.2 volts. That’s an accepted figure, but it only applies to 77°F, it won’t do anything as the temperature declines. Worse, modern cars and trucks have constant parasitic loads. A float charge won’t work right here either.
Someone suggested using a Variac combined with a manual charger, the old school transformer based chargers. Usually 2 and 6 amps. These are unregulated taper chargers. They do the job well, but in warmer temperatures will boil a battery dry if left connected. But when combined with a variac, they basically become a variable DC supply. Get your thermometer, voltmeter, and temperature compensated charging chart. Applying the correct voltage, current, etc for the correct amount of time at a given temperature is the only way I can get a battery to charge to 100% quickly, or what passes for it given lead acid is sluggish. It takes a long time even if the voltages/current is right.
So I thought it was working fine. Once the heater was running, the readout on the power supply would stabilize at 14v and slowly drop to 0A. Which I took to mean that the battery was now full and the power supply was either providing the power or recharging the battery at the same rate the heater was consuming. As you can probably tell, this is not my area of expertise.
But last night the heater shut down due to low voltage (I know this because it threw a low voltage error code). After I disconnected everything the battery was reading 11v and when I hooked just the power supply up it was back to 14v/5A. I’ve since recharged the battery and it seems to be holding voltage.
If the power supply is reading 0A, that means there’s no electrical current (and therefore no power) coming from the power supply. At that point, the battery is the only thing left that’s supplying electrical power to operate the heater, so it’s no surprise that it ran down over time.
You need to figure out why the power supply refused to supply current even when the battery voltage was getting low.
I have almost no expertise in this area, and that’s kinda what I’m asking you guys.
I thought the drop to 0A was because little or no current was being drawn- as we’ve discussed, once past startup it’s only drawing for a fan, a controller, and a tiny fuel pump. But of course I understand that some current is required to do anything.
But why I thought it was happening that way is this:
Low battery, no heater: Connect power supply, the PS reads 14v / 5A. The amperage on the PS slowly drops to 0 as the battery is charged. Once the PS is at 0A the battery is (as far as I can tell) charged.
Low battery, with heater: Start heater, connect PS. PS will read 14v/5A, and as the over time the PS drops to 0A. I took this to mean that the PS was net-charging, faster than the heater was consuming. Clearly not the case.
So it SEEMS like when I start it up, the heater is drawing and the PS is charging. But then the battery goes full and the PS stops supplying current. But then never starts again.
FWIW, I have the current dial all the way up, and I adjusted the voltage dial to 14. I could turn that up or down. Also, and not surprisingly, my meter always reads what the display on the PS reads, if the PS is connected.
Just to be clear, this isn’t a huge issue in any way- there are multiple ways I could run this thing. But now I’m just trying to understand what’s happening .
Many battery chargers are not intended for continuous trickle charging. They charge a battery up to the charger’s idea of 100% and then shut off. This is like the behavior you describe.
Yes, OP needs to tell us more about the power supply/charger. There must be a timer, topoff threshold detector, or (my guess) perhaps an inrush current exceeds the supply’s capacity causing an overload provision to kick in, cutting the supply.
Something caused the power supply to quit so the battery ran down. Disconnecting/rebooting restored the supply.
330CCA is an automotive starting battery specification. But that indicates a pretty small battery.
Sounds like the diesel heaters draw about 2 amperes. This would nuke a large deep cycle in a day or two. Ordinarily a 100 ah battery is only drawn down to ~ 50% and recharged for longer service life. What you want is something that is standalone like an RV controller?
Some of the smart chargers aren’t necessarily so smart, and without temperature compensation, mostly defective. They “see” a battery is 87% charged and don’t charge nearly long enough to plus them back up, or make no temperature adjustments. About 30% of battery capacity is in that last 10%.