In Car Power Inverter Problems.

Hi All.

I have had a power inverter fitted into my motability car, with the prime function of running a heated blanket to keep my disabled son warm. He has many complex problems, but one of the worst is he has lost the ability to maintain a body temperature. When indoors, we use a bair hugger or a heated blanket. I purchased the inverter and got the company who converted the vehicle to fit it. The inverter has a peak power output of 2000 watts, with a continuous output of 850 watts. The blanket is rated at 120 watts with a 3 amp fuse. A switch has been fitted, but for some reason they have only used a 20 ah battery inside the vehicle. When the blanket is plugged in, the control box gets red hot after a few minutes and displays a fault code. We have tried 3 other blankets with the same result. I have tried them on various heat settings. Same result. They have been back out twice and still doesn't work. I have tried various other electrical items with differing results. We looked at a cigarette lighter heated blanket, but it hardly gives off any heat. Our son has become a prisoner in our house. I reckon the battery isn't powerful enough, but am unsure if I can just take the current one out and replace or do I need to upgrade the wiring aswell. Any help would be gratefully received.

sounds more like a control box issue to me. A 20A battery is big enough to power that blanket for a few hours at least.

I have spoken to another company, who were also justified as to why they had used a 20ah battery instead of a 110ah battery. The idea of this was that we would be able to use the inverter with the engine running when taking our son out, or with the ignition off when we just want to warm him up. We have tried 3 different makes of blankets thinking that it may be the blanket, but all 3 for the same. It's so frustrating as this cost a fortune. Each blanket alone has cost £45. 

Forgot to say that all 3 blankets work fine in the house with the control box for each of them not heating up at all. 

What type of inverter have they put in? 

I bought the inverter. Peak output is 2000 watt, with a continuous output of 1000 watts. It is made by Lvyuan, and is a modified sine wave. Reason why I got this one was it said that it was designed to power multiple loads and major house hold appliances, so thought it would be ideal for an electric blanket. I thought it best to get it installed by a professional so correct cables and fuses where used, along with a switch over switch aswell. If you need anymore info let me know. 

Sounds really strange. On the face of it, it should work OK. I don't think it's the battery, more like an incompatibility between the invertor and the blanket.

Does just the same happen with the engine running?

I take it that the "control box" which is overheating is part of the blanket(?). Have you a link to its specification? Is it definitely only 120watt?; that doesn't seem much.

Will the invertor drive another load, such as an incandescent lamp, or a small (<1kW) convector heater ?  

Do you have a link to the invertor specification?

Might well be worth talking to this bunch http://www.bblbatteries.co.uk. They are very helpful. I suspect, might be totally wrong that, the modified sine wave may not be compatible with the blanket controls. I think you could do with 'true sine wave' , but could be talking garbage. 

Inverter sounds like cheap Chinese bolocks to me, sorry to be pessimistic, had cheap inverters on works vans that just die randomly before.

Best to invest in a pure sine wave inverter from a reputable source.

You have a modified sine wave inverter feeding the controller for the blanket?

There is an issue with the compatibility, the output of a modified sine wave inverter is not a clean pure sine wave, the controller may also have electronic switching which is causing the overheating.

The issue lay with the inverter, contact BBL as advised above & get a pure sinewave unit.

I have a 3kW Ring pure sinewave in my van, from BBL as it happens.

it does sound like the controller may not be liking the modified sinewave from the inverter

you say youve tried 3 blankets. have you tried them in the house plugged into a nromal socket? same result or working fine?

another option, skip the inverter and get a 12v blanket (thats if they exist, not something ive looked for)

The ' Control Box ' is part of the blanket. It turns the blanket on and off and alters the heat settings. All 3 work fine when used in the house. We have a blanket that you plug In to cigarette lighter but it gives off so little heat it's a waste of time. All 3 blankets are rated at 120 watts with a 3 amp fuse. Will try a lamp in the morning or another item that heats up and report back. Power inverter was from Amazon. Will also give BBL a ring. 

Some of these inverters are rubbish, unless you are spending a good chunk of money on it then don't bother. I bought one a few years ago to charge drill batteries in my van, it worked fine when connected to a battery sat on the garage floor and it charged the batteries, the problem came when it was connected in the van. Without the engine running it ran fine, start the engine however and it cut out and wouldn't work, it kept saying overvoltage. Some of these cheap chinese ones are not very good on the input and output. in the end I found mine was designed to work on 12v but it had no tolerance, so when the car engine started and the voltage increased to around 13.5 it was enough to cause it to shut down.

In short, if the OP needs a power source for something as critical as it sounds then like it or not I think he's going to have to lay out a few hundred quid for a decent unit. 

Quick update. I have plugged in the wife's hair straighteners. They use a 5amp fuse and rated at 47 watts. They got so hot I was unable to hold them and started smoking. This was done with the engine switched on. Have also plugged in a lamp aswell. This seemed to work ok. What makes this so frustrating is we were charged a stupid amount of money to have this installed, which was kindly paid for by a charity. All I want is to be able to run a heated blanket to keep my 6 yr old son warm. He has over come so much, 2 yrs of chemo, didn't work, then 2yrs solid in Hospital. He is now wheel chair bound, blind, unable to talk following a stroke, has suffered a cardiac arrest and beaten a brain tumour. Judging from what some of you have said, I now need to stump up yet another couple of hundred pounds to boot. Off to write a snotty email to OH Mobility to see it they will pay for it. If anyone has any other ideas please let me know.

Sounds definately like an inverter issue, it would be interesting to see what voltage it's throwing out, where are you, maybe one of us could check it for you. One other possibility is to do away with this thing altogether and use something like a truck night heater, there are quite a few cars that have these fitted as standard, of course this is only possible if the vehicle is diesel. My mate has one in his Seat Alhambra, we were out one night and it was literally freezing, outside temp was around -2 and it was freezing in the car, within a few minutes, the car was toasty warm, these things are actually fitted in most modern ambulances, think about it, someone almost naked in the back of the truck being treated, it has to be warm.

I hope this gives you some ideas, best wishes Phil 

phil d said:

 One other possibility is to do away with this thing altogether and use something like a truck night heater, there are quite a few cars that have these fitted as standard, of course this is only possible if the vehicle is diesel.

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you can add an additional tank for the heater, then you can use red

Andy™ said:

you can add an additional tank for the heater, then you can use red

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Forgot that one mate, cheers, of course even running on regular diesel they are not too bad.

phil d said:

Forgot that one mate, cheers, of course even running on regular diesel they are not too bad.

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they dont use much diesel. usually 15 lites in the tank will last me months

I have to agree the invertor is the main suspect, perhaps putting out some high voltage / high frequency waveform on top of the required "mains" voltage. 

One more point which struck me is that you said the low voltage blanket of the same power rating doesn't give the same warmth.  It should do.

The most likely reason for that is volt drop in the supply to it. I've sometimes found cigar lighter sockets which are useless above a couple of amps, either due to the socket/plug combination or to inadequate wiring in the car. If you could arrange to connect the blanket to the wiring that has been installed to supply the invertor you may find it works a whole lot better. Again an electrician with some test gear could possibly help you.

Just a thought?

have you got the original quote for the install, have they fitted what they said you need or changed it for the cheaper version? 

Ita clearly an issue with the differing inverters and your control gear of the blanket.