Jump to content
bsh

Hella SSR Relay fuel pump control issue.

Recommended Posts

Hi,

I setup FP Speed to control my Walbro 525 lph in tank pump. I use a Hella 4RA 007 865-031 SSR relay. 1000 hz. Problem is when the car starts, it just take about 1 min, and the fuel pump starts to see lower voltage from the relay and the relay starts to gets to hot to touch... I believed there was something wrong with my fuel pump, drawing to much current, so I scoped it and it was only about 10-12A @ about 50% duty cycle... The relay is rated 18A.

Should I use a different frequency and/or a flyback diode?

Any idea what can cause this? Have I got a fake Hella relay? Looks legit with the Hella stamp and part#.

See scope trace:

Hella PWM SSR Relay fuel pump.png

Share this post


Link to post
Share on other sites

You can't pwm a fuel pump with only a standard ssr, they are not able to drive an inductive load.  You will need a fuel pump controller or a circuit designed to pwm inductive loads.  

Something like this would be suitable :-

https://www.infineon.com/cms/en/product/power/smart-low-side-high-side-switches/automotive-smart-high-side-switch-profet/power-profet/bts50010-1tad/?redirId=103222

Share this post


Link to post
Share on other sites

Thanks for the reply,

I found a 15A diode from back in the days I raced Rc-cars with brushed motors/esc, which I soldered into the circuit, and now it seems to work, at least for about 10 mins when I tested. The diode was warm, but was able to hold it. The same for the relay, warm, but able to hold it. Stable voltage output as well. I guess I must find a more suitable SSR, but have seen other people use the Hella SSR controlling fuel pump...

Share this post


Link to post
Share on other sites

The Hella SSR's are quoted as being suitable for PWM of inductive loads up to 1000Hz.  I have used one at 1000Hz for fuel pump control before with no drama although it was a relatively small pump.  I have been working with another guy recently that is using one to drive a large solenoid operated diesel fuel pump and his was getting very hot at 1000Hz, but dropped back to 500Hz and it is happy.

Share this post


Link to post
Share on other sites

Any time you're running an inductive load it's a good idea to use a flyback diode. It'll even help normal relays last longer by saving the contacts from extra arc burn. I'm wondering if anybody has tried these Crydom SSR's? They have a huge current capacity, accept PWM, they isolate the ECU from any noise from the load with a optocoupler, and you can pick up a heat sync for cheap on amazon. I ordered two 60a (overkill, but they were unused old stock for 40% off) ones off eBay and am going to test them with a fuel pump and cooling fan with PWM from the ECU. But I will definitely be using some big diodes to protect them. They even have a wiring diagram showing how to wire the diode for an inductive load. I'm still waiting on delivery but I'll try and report back when I see how they work.

 

 

Screen Shot 2019-04-20 at 12.59.53 PM.png

Share this post


Link to post
Share on other sites

The Crydom DC-series SSR's work fine, I've been running my 450's off one all last year with no problems. But yes you do need a flyback diode at the pumps. ( 2x450's off one 60A ) I've a 3rd in tank pump if need be and a 100A relay sitting if and when I do need to use it

And in no way whatsoever is the little Hella relay suitable for such a purpose, even from the standpoint of coping with the current of such a pump, nevermind trying to pwm it too.

 

Haltech offer this drawing and is how I use mine with Syvecs. Although a high frequency would probably be better with a proper controller, it does seem SSR's dont really enjoy being pushed in this way. I found mine happy around 200Hz.

https://www.haltech.com/wp-content/uploads/2017/10/SSR_Power_SW_Web.pdf

 

I do use one of the Hella SSR relays for my water injection though.

Share this post


Link to post
Share on other sites
2 hours ago, Stevieturbo said:

The Crydom DC-series SSR's work fine, I've been running my 450's off one all last year with no problems. But yes you do need a flyback diode at the pumps. ( 2x450's off one 60A ) I've a 3rd in tank pump if need be and a 100A relay sitting if and when I do need to use it

And in no way whatsoever is the little Hella relay suitable for such a purpose, even from the standpoint of coping with the current of such a pump, nevermind trying to pwm it too.

 

Haltech offer this drawing and is how I use mine with Syvecs. Although a high frequency would probably be better with a proper controller, it does seem SSR's dont really enjoy being pushed in this way. I found mine happy around 200Hz.

https://www.haltech.com/wp-content/uploads/2017/10/SSR_Power_SW_Web.pdf

 

I do use one of the Hella SSR relays for my water injection though.

I'm glad to someone else has blazed this path! I'm very new to all of this and the learning curve has been steep. That 1k pull-up resistor is interesting. I've never seen it used for PWM on anything else, but I bet it makes for a much cleaner signal coming from the ECU...

How big of flyback are you using? I know when it's going to a solenoid, it's supposed to be rated for the amperage that it takes to operate the solenoid. But that's not really feasible with pumps drawing 20+ amps and fans drawing 40+ amps...

Share this post


Link to post
Share on other sites
13 hours ago, Scrufffy said:

Any time you're running an inductive load it's a good idea to use a flyback diode.

The Hella relay that this thread was about has a flywheeling diode built in and specifically states suitable for inductive loads and controlling motors.  

 

9 hours ago, Scrufffy said:

I'm glad to someone else has blazed this path! I'm very new to all of this and the learning curve has been steep. That 1k pull-up resistor is interesting. I've never seen it used for PWM on anything else, but I bet it makes for a much cleaner signal coming from the ECU...

The pull-up resistor shown on the Haltech diagram is because their ECU's dont have a pull-up built-in.  Ours do so you dont need that.  It does not make the signal "cleaner", it is just needed when driving an solid state device to prevent a "floating input". 

From the few SSR's that I have played around with, the Crydom and other similar industrial ones only seem to work up to about 100-200Hz max and the controllable range of the motor seems to suffer a lot at that.  The Hella one worked at 1000Hz for me, although as I said above earlier, I know another guy that had to run his at 500Hz as it got very hot at 1000Hz with a large inductive load.

I would like to try one of these one day, but havent had a job for one recently:  https://www.holley.com/products/nitrous/controllers_and_accessories/parts/15620NOS

Share this post


Link to post
Share on other sites

The little Hella units are not rated for any sensible current in a steady load. Peak, surges yes they can do higher, but not continuous duty and I think they quote even less when PWM'ing. And a fuel pump is very much continuous duty. That 525 will easily be pulling 15A or near at base pressures, nevermind with boost. That's already exceeding what the Hella can cope with

 

For water injection, I think my pump only pulls around 5A, so no big deal there, the Hella works great for that....although I will also add it seemed to work best at only 50Hz. At higher frequencies, the pump really struggled.

 

With the Crydoms and my 450's I used this diode across the pump wiring. Probably overkill, but figured may as well go big. Flyback current should never really be high.

https://uk.farnell.com/vishay/vft4045bp-m3-4w/diode-schottky-45v-40a-ito-220ac/dp/2115198?CMP=i-ddd7-00001003

 

Again, I tested this at various frequencies and watched fuel pressure to see if it changed and at various duties, and ended up leaving mine at 200Hz. The likes of a 100A DC Crydom states max is 650Hz.  Some lower current versions claim to allow higher frequencies.

 

As for the resistor across the input terminals...really no idea what it is for. I have used it with and without and both seemed to work fine ( with Syvecs ). But I left it in there, as presumably they wanted it there for a reason and it can do no harm being there anyway.

Share this post


Link to post
Share on other sites
39 minutes ago, Ducie54 said:

How close are you guys putting the flyback diode to the load? Does it matter how close it is to the load. 

It doesn't need to go near the load.  It is protecting the switch contacts so closer to the relay is better.

Share this post


Link to post
Share on other sites

Little update regarding the Hella SSR relay. It still gets very hot, and after a while, it wont output full voltage... I believe I must look for something else... I just wired a normal relay so SSR relay get bypassed and pump get full voltage at about 35% injector dutycycle... Have anyone tried the AC Delco/GM fan controller?

Share this post


Link to post
Share on other sites

Why not just use a SSR that is already proven to work ? The Hella SSR will not work for this application.

 

Fan controller might work, but I've heard they have a very slow response to changes which may not be ideal for a fuel pump.

 

Some Range Rovers or vehicles do use a FPCM which may be able to be used, but a SSR is so simple anything else just seems pointless.

Share this post


Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...

×
×
  • Create New...