Automotive 11 to 13.8v step-up

Hi all,

What a cool site! I dabble with electronics and dabble is the correct word. I'm somewhat surprised I haven't killed myself yet. This looks like an outstanding place to learn!

I have an old car and a couple of devices on it require a bit more than 12v. I saw many step-down solutions on the net using the LM317T.

I need to step-up from 11 to 13 volts. Are there any simple circuits and off-the-shelf components that would allow for the economical (in terms on size and cost)?

The exact item I'm working on is a windshield washer pump that will not work at 11 volts (which is what I'm getting at the 2 factory leads). This is because of resistance in the power supply (harness, fuse boxes, switches). Getting the battery voltage (13) would require me ripping out and replacing about a mile of harness and I'd rather not do that. If I can step from 11 to 13 or so, It would work perfectly. I verified this on a bench.

Thanks guys! I look forward to leaning a lot here and will try not to be a pest.

Sounds like the windshield washer pump is near failure. It should still work at 11V. It may not squirt as far, but it should still work.

Thought so myself. So, I bought a new one. It's behavior is exactly the same. Now I have an extra.

Locate where the negative of the battery connects to.

Disconnect the distributor so it won't start. Crank starter for 10 seconds. Touch the battery terminals and where the negative wire connects to at the chassis.
If any point is warm, you have a poor/corroded/loose contact.
Correct that by grinding to bare metal, use a wire brush, or clean to shiny metal all those points/terminals/posts and re-tighten in licking clean condition.

Come back with findings.

Externet's advice is good. If that doesn't work, what is the max current that you need from the boosted 13V? There are some "boost" converter IC's out there that may do the job, but it's more complicated than a LM317 circuit.

Thought so myself. So, I bought a new one. It's behavior is exactly the same. Now I have an extra.

Click to expand...

By "new" do you mean brand new or from a wrecker?

Excellent test. Never heard of that one before! Disconnected coil, crank for 10 seconds: no temp change - checked with IR thermometer (and touch), before and after.

New is factory OEM. I can actually source many new Peugeot parts even though the car hasn't been sold in NA for 18 years. It's a SEIM unit. **broken link removed**

Being a mechanic I can assure you that a wiper pump will work fine at 11v. I'd be looking for restrictions in the hoses. Grab a few feet of hose and connect it to the pump outlet. Squeeze the tip of the hose at the other end and I bet it squirts all over.

$.02

As above - 11 volts will drive a washer pump fine.

I was thinking car voltages should be around 13-14vDC while running. 11V sounds like an electrical problem.

Mikebits said:

I was thinking car voltages should be around 13-14vDC while running. 11V sounds like an electrical problem.

Click to expand...

True, his alternator (or generator) should be around 13.8-14.2. He took the measurement at the pump. I'll assume while the pump is running and it doesn't suprise me if it was 11v even with 14v on the battery. OEM's use the smallest gauge they can get away with.

He stated his battery was at 13v

You guys got off subject.

I am interested in a voltage doubler circuit also for use with POE for WiFi APs.
I'm running a solar powered NOC with voltages between 10 to 16 VDC. I
need a circuit to increase that to 24 to 36VDC. Max current would be at most
1 amp. Right now I use an inverter but that requires too much draw on the
batteries.

MrUmunhum said:

You guys got off subject.

Click to expand...

No you're the one who has got off the subject.

Please create a new thread rather than hijacking someone else's.

Peugeot :

Measure the battery voltage at the battery posts; should be around 12.5V with engine not running and about 14V engine running.

[Check the same in another healthy vehicle, there is a chance your voltmeter lies.]

If readings are lower, chances are your battery is bad, try with another battery and repeat.
If the same readings are obtained with another battery, chances are the charging voltage regulator is bad.

Miguel

Results:
Engine running: 14.75
After stopping: 13.05
After dissipating surface charge (headlights on for 5 mins): 12.49
Corrected for temp (64 degrees F) [-.072v] : 12.418

Battery: Johnson Controls, 3 years old
State of charge: 75%

All power hungry accessories (rear window defroster, power windows, heated seats, etc.) work great and at proper speeds. All electrical (& mechanical) parts of the car work as they should.

A little more backstory to what I know about the problem. I have a bench 12v power supply and tested the motor. At 11 volts, it doesn't work, but at 13 it does - well. As the pot is turned up and the motor starts spinning, you can hear the first startup as the windings overpowering the permanent magnets.

-12 is grounded well. My multimeter confirmed nil loss of continuity with (-) battery.

I'm pretty sure the +12 wire is suspect. Your right, it's a small dude - 16 gauge. I took an tiny emery board to the ATC fuse holder for that circuit as well as the fuse itself. I went from 10v to 11v. The +12 goes through a couple of harnesses and through the wiper stalk. I don't want to disassemble that part of the car at this time only to get "on the edge" of motor functionality.

That's the reason for the +2 v step up circuit request. As well, I would also adapt this circuit to the power window motors which from the factory are slow and are about 60% the speed as new cars. The motors are made by AOP and Rockwell. I haven't found another car that uses them, so apples-to-apples comparisons to other cars isn't possible. A EE guy on the car specific maillist made his own DC-DC step up near the fuse box and ran a few select circuits off it after exhaustively testing the motor speeds & loads. He was running 20v (!). I don't think I'll go that nuts, but a couple of more volts here and there would do wonders.

Thanks for the all the great input!

I'd find another motor. I used a pump from a Honda Civic in my squirtgun with a 9.6v nicad pack when I was a kid. lol

Thanks for the details, you did your 'homework' right.

Seen older European cars wiring suffering from poor contact at specially the fuse holders due to a whitish corrosion and lack of firmness. Check if any gets warm under load.
As you suspect, I agree; smaller cables are not good for large currents; but still feel I should push one more time for trying to find a contact problem

There is a main feed cable from the battery + (or from the starter +Bat node) to the fuse box (perhaps via the keyswitch !) that has to be checked under some load, advancing your voltmeter + from the battery + post at 12.5V trough every node, junction and connection up to the fuse box and determine where is it dropping 1.5V ending in 11V.

You did well confirming that by cleaning such point gained 1V already from 10V to 11V. There has to be more of those along the supply circuit.

Miguel

Don't take this the wrong way...

But as others have noted in suggestions to move to another automaker's or aftermarket pump, the factory setup needs a boost. The harness gets pretty nasty (in terms of access) after the fuse box. I agree that I could find other points of current loss along the line, but I think the part is asking more than the circuit is designed for.

Other have said that 11v should do this no problem. I agree. The problem with other pumps is fit into the system. I do not want to pitch the pump.

Let's just say I'm going to go with a step-up regulator. Any suggestions on that line?

Thanks again!

You can measure the drop between point-a and point-b by connecting your meter leads between those 2 points or anywhere in between. You will read 1.5v if that is the drop your finding. I thought I'd suggest it if that method might help in any way. I've used that method to locate breaks in wires before. I would poke the wire every 6 inches or so untill I saw a larger drop.
Unplug the pump and place a headlamp there instead, then have someone hold the squirt button while you poke around. That way you can have a load without having to worry about burning out your pump motor or wiring.

That pump motor should run on 11v. I'm really suprised it doesn't. Are you -SURE- thats a new pump and not some old junkyard pull with a swolen/hard impeller?

EDIT - I just saw your recent post. You could leave your pump in place and suck through with an in inline pump. That is MUCH cheaper then building a boost converter. If you insist on a boost converter, most of what you need can be found in an old car audio amp that has a switched mode power supply. You will have the PWM IC (SG3525/SG3524 ect), N-ch mosfets, and a nice toroid to rewind, rectifiers, filter caps, the works.

...or maybe something like this.

DC/DC Converters, retail, wholesale, off-the-shelf and custom, DC/DC 5 watts to 1500 watts

Peugeot said:

Hi all,

What a cool site! I dabble with electronics and dabble is the correct word. I'm somewhat surprised I haven't killed myself yet. This looks like an outstanding place to learn!

I have an old car and a couple of devices on it require a bit more than 12v. I saw many step-down solutions on the net using the LM317T.

I need to step-up from 11 to 13 volts. Are there any simple circuits and off-the-shelf components that would allow for the economical (in terms on size and cost)?

The exact item I'm working on is a windshield washer pump that will not work at 11 volts (which is what I'm getting at the 2 factory leads). This is because of resistance in the power supply (harness, fuse boxes, switches). Getting the battery voltage (13) would require me ripping out and replacing about a mile of harness and I'd rather not do that. If I can step from 11 to 13 or so, It would work perfectly. I verified this on a bench.

Thanks guys! I look forward to leaning a lot here and will try not to be a pest.

Click to expand...

PLs tel me your pump current drown from battery (inrush and continuous) at 13.5 volt

How do I determine that?

(sigh - pump is fine - both old and new)

I have another car like this (one model year away) and pump in inop as well. It's pretty endemic with this pump/application with this model.

Lazzer408: Guaranteed it was new. In sealed factory bag.