OT inverting power from 24 volts (help, please!), (2 batteries in my wheelchair) Options

[Korijo]

I want to invert some power from my wheelchair. It has 2 12v batteries. It already converts 110v to charge them.

Here's what I want to do...

1) Power my video camera/charge the camera battery.

2) Run my electric lawn mower. (IMG:style_emoticons/default/wink.gif)

3) anything that needs 110v... (IMG:style_emoticons/default/idea.gif)


Anyone know what I need ? I dont know where to begin...

[Dr Evil]

You can get an inverter fom radioshack that would normally be used on 12v car systems. I bet you could even get one on ebay for less. But, you may wish to add a third battery as I am not sure of the current draw. Here is a basic concept: Voltage inverters work by either exchanging amps for volts, or volts for amps. So If when charging your chair you are going from 110v to 24 0r 12v then I would bet you that the current coming out is large. If you wish to do the reverse it will take large current from your battery and convert it to a low amp/high voltage output (E=IR).

You may have a harder time finding a 24v converter, but you could just hook a 12v up to one battery.

[larryp]

Harbor Freight has a number of small inverters. You don't need anything very large, or your chair is not going to be going far. They are pretty inexpensive; one is here.

Inverter

[Korijo]

i've found some around (target, ebay).

i just dont know if i need to be 'worried' about surge protection, or wattage.


700 watts huh ?? (IMG:style_emoticons/default/idea.gif)

[Dr Evil]

P=IE so at 700Watts I would expect you would get around (700/110=) 6.36 amps out of the inverter. I am not sure what it would draw from your battery though.

[TonyAKAVW]

I would be careful getting a 12v inverter and trying to run it off of 24V. You might let all the magic smoke out of those electronic components that do the inverting.

There are 24V inverters made, and I did a quick search on Google's Froogle search and there are a bunch out there, presumably for marine applications since those systems tend to run off of 24 volts rather than 12.

Addnig a third battery to the chair is a good idea, but then you either use the third battery by itself for the inverter, or put it in parallel with one of the batteries. The downside there is that one battery will always be more charged than the other, forcing the other battery to work harder (discharge deeper) and have a shorter life.

On the other hand you could get a tiny portable Honda generator and strap it on there and then you acn recharge your batteries while in motion and technically you have a hybrid powered chair!!!!

-Tony

[Dr Evil]

On the other hand you could get a tiny portable Honda generator and strap it on there and then you acn recharge your batteries while in motion and technically you have a hybrid powered chair!!!!

Good idea, Tony. Ya, no 12v on 24v power.

[lapuwali]

Check the power ratings on some of the devices you intend to use. The lawnmower almost certain draws more than the 5 amps or so you'll get out of a 700W inverter. So will a vacuum cleaner. Simply multiply the amperage rating on the device by 110v to get the number of watts drawn. I'd expect a 700W inverter will have a 7-8 amp fuse on the output. The batteries on your chair are very likely capable of delivering 1000W or thereabouts, at least for short periods. 750W is about 1HP, btw. That should give you some idea of how much power is being dealt with.

[Joe.D]

P=IE so at 700Watts I would expect you would get around (700/110=) 6.36 amps out of the inverter. I am not sure what it would draw from your battery though.

Replace 110 with 24 in the same formula. 700 watts at 24v would draw nearly 30 Amps from the 24 volt battery. The Amp-hour rating of the battery will tell you how long the battery can sustain that load.

[Korijo]

Looks like i have 2 70AH batteries.

Found this 24v inverter : 24v inverter
$$$

Is there no cord, or adapter thing to draw power from the charging port ?

[TonyAKAVW]

Usually for the larger inverters (>400 watts maybe) they don't use connectors, rather you just wire the cables directly to the battery, they might ahve an internal fuse (best to have a second fuse unless you want to risk having that heated seat option).

The current draw will be very high on the 24 volts, so a connector unless specifically made for high current will likely melt.

Also remember when doing your calculations, that the inverters are not 100% efficient. Most are somewhere around 80% efficient.

-Tony

[Joe.D]

Looks like i have 2 70AH batteries.

Found this 24v inverter : 24v inverter
$$$

Is there no cord, or adapter thing to draw power from the charging port ?

I'm not sure I understand what you're asking here.

If the "charging port" is the AC "in" connection for power to charge the batteries. I think you're asking if you can get AC back out of the same connection.

It takes 110 VAC input and creates 28V DC output to apply to the batteries to charge them. The "charger (really, a rectifyer)" converts alternating current (AC) to direct current (DC) and steps down the voltage. It probably also adjusts the power applied to the batteries as they get closer to fully charged.

To get AC 110 from the 24 VDC batteries, you need an "inverter" that converts DC to AC and steps up the voltage to 110.

A battery charger isn't bi-directional; it can't create 110VAC by taking power back out of the batteries. You need an inverter to do that.

Joe

[smdubovsky]

Whoo hoo, something I know something about;) Try a solar energy business (like www.energyoutfitters.com). Off grid solar apps come in 12, 24, and 48V varieties and make inverters to suit. Don't connect a 12v inverter to only one battery. It will unbalance the pack and cause the set to fail over repeated charging cycles (Im a battery charging engineer, so trust me on this one.) Or find one on ebay...

SMD

[Gary]

Dave,

Here's a site with very reasonably priced inverters: 24V power inverters. I just bought 3 of the 400W jobbers. They'll be used to run a laptop and some medical simulation equipment in a hummer. They should work well for your smaller devices: camcorder, laptop. I don't think you'll have enough juice in your wheelchair batteries for the lawnmower; might need to run a cord for that.

[bondo]

Find yourself a dead 2 battery UPS (battery backup for computers). There's your 24v inverter! Should be dirt cheap as replacement batteries for UPSs cost more than replacing them. Functional UPSs with dead batteries are all over the surplus market. You may need to disable a buzzer, as some UPSs have an alarm to indicate they're running off batteries.

[Korijo]

Dave,

Here's a site with very reasonably priced inverters: 24V power inverters. I just bought 3 of the 400W jobbers. They'll be used to run a laptop and some medical simulation equipment in a hummer. They should work well for your smaller devices: camcorder, laptop. I don't think you'll have enough juice in your wheelchair batteries for the lawnmower; might need to run a cord for that.

nice !! thanks (IMG:style_emoticons/default/biggrin.gif)

would i need only 1 ?

[Gary]

Dave,

Here's a site with very reasonably priced inverters: 24V power inverters. I just bought 3 of the 400W jobbers. They'll be used to run a laptop and some medical simulation equipment in a hummer. They should work well for your smaller devices: camcorder, laptop. I don't think you'll have enough juice in your wheelchair batteries for the lawnmower; might need to run a cord for that.

nice !! thanks (IMG:style_emoticons/default/biggrin.gif)

would i need only 1 ?

Yup. One should do you. We have a couple vehicles and I wanted a spare, which is why we bought three... If your're running a camcorder and a laptop, I'd imagine you'd be fine with the 400W version. Again, check the equipment (typically the wallwart that plugs into the 110V socket) for the power draw, to be sure.