Replacing an SRM battery... at home :o)

Discuss light weight issues concerning road bikes & parts.
whodesigns
in the industry
Posts: 161
Joined: Thu Jan 08, 2009 12:16 pm
Location: Melbourne Australia
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by whodesigns

mv2005 wrote:Hi all, first time poster with particular interest in this topic.

Also, I did notice a small amount of fluid adjacent to the battery. Not sure if this is some form of lubricant or signs of a leaking battery or moisture ingress. ANy thoughts on this would be appreciated.

Thanks in advance.
Mike


This fluid is silicon oil to help protect the electronics, there are also a few other tricks to help seal and protect the unit.

The first wireless units could also be used wired and some came with either a single rectangular or the round battery. SRM then went to the dual rectangular battery.
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Geoff
Posts: 5120
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

That is completely accurate. The 7800 SRM had an option to run a wired sending coil together with the wireless transmitter. The problem is that if you elected for the sending coil, you lost a battery. Do you have the copper wire sending coil?

mv2005
Posts: 3
Joined: Sat Feb 26, 2011 2:35 am

by mv2005

Just an update on my home made job...

Firstly, I haven't used a soldering iron for perhaps 20-25 years and even then I wouldn't have know much about what I was doing. Got the LTC-7PN-S4 batteries from an obscure technical gadget supplier (thanks to Phil 'McKnight' for the link!) at $16AUD a pop + $10 transcontinental shipping. Bought myself a cheap soldering iron. Opened the unit, pulled out the single battery and slid back the joint sheathing. Iron melted the existing join in seconds. The tricky part for me was getting the new solder nice and neat. I would get it looking pretty good and then decide I could maybe get a little bit extra on top and end up breaking the connection and having to start again. Probably wasn't using perfect solder technique either but in the end I got both terminals joined and slid the sheathing back over the top. THen when I went to put the battery back in realised I should have soldered the SRM wiring on the inside of the battery prong, as the SRM wire on the outside made it basically impossible to push the battery back into place. I ended up flipping the batter upside down (crossing over wires) and managing to fit it in that way.

Others have commented on how the white plastic disc doesn't seem to stay in but not to push it in hard. I obeyed this advice and waited until I fit the chain rings and sure enough the small ring catches a wider portion of the disc and seals it in nicely. Upon fitting the cranks the real test came. Spin the cranks and turn on the Edge 705. Power meter detected. Bingo! Took the bike for a spin around the block and the wattage figures seemed right on the money.

The summary is that it really wasn't that complicated. I didn't remove the right crank so had to tape the white disc up against the crank shaft so it was out of my way. Soldering was a little tricky but I was doing it outdoors with a bit of wind and inquisitive kids around. Cussing was a prerequisite! MIght not be the prettiest job but it certainly worked and in my case saved me about $250 AUD based on quoted battery replacement and shipping rates (if I insured to full value).

Mike

studodd
Posts: 52
Joined: Sun Jan 10, 2010 11:26 am

by studodd

mzagorski wrote:The battery in my Dura-Ace SRM died so I decided to repair it myself. Took some photos during the process if anyone is interested:

http://www.mikezagorski.com/archives/000700.php

Here are some photos...

i just changed the chainrings on my srm, when the back plate came away with the inner ring. there is a wire soldered to the plastic back plate and what looks like a copper loom. only seems to now be attached by a very small single copper strand. should it be like this? do i need to get it repaired? seems to work ok but not sure if it will affect the accuracy or whether its meant to be like this. what does the loom do?

any advice would be appreciated. i'm due away on a trng camp tomorrow and want to know if its worth taking it or not....

Geoff
Posts: 5120
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

That is the Sending Coil! Do not damage or sever that coil. Be gentle when you re-install the lid and test that the coil has not been damaged.

wetpaint
Posts: 82
Joined: Sat Feb 06, 2010 2:55 am
Location: USA

by wetpaint

My SRM battery lasted 400 hours this time. I found a new place to order the LTC-7PN-S4 batteries for those that are in the US. Total cost was $38.64 for 2 batteries shipped. They showed up on my doorstep 3 days after ordering.
http://www.osibatteries.com/p-742-eagle ... ttery.aspx

Grimpeur
Posts: 509
Joined: Tue Oct 18, 2005 6:02 pm
Location: The Netherlands

by Grimpeur

I have a wired SRM pro (older version, so regular SRM crankarms) in need of a new battery. Opened it up and it looks the same as zagorski's one (round), but it has two wires connecting to it, a red and a black one, instead of only a red one? Does this mean I need a different type of battery?
Here's a pic of what mine looks like:
Image
This is my Bike. There are many like it, but this one is mine. Without me, my bike is useless. Without my bike, I am useless.

dual
Posts: 153
Joined: Thu Dec 20, 2007 8:55 pm

by dual

No, you just need to solder the black wire to the battery's casing. It's an additional ground wire.

Grimpeur
Posts: 509
Joined: Tue Oct 18, 2005 6:02 pm
Location: The Netherlands

by Grimpeur

Thnx!
Btw, if anyone has any leads on where to get this battery (the QTC85 3B880) in Europe I'd love to hear it. I have been googling all over only to find one british webshop that has them, but they're out of stock there.. :(
This is my Bike. There are many like it, but this one is mine. Without me, my bike is useless. Without my bike, I am useless.

mormar02
Posts: 5
Joined: Mon Nov 07, 2011 11:11 pm

by mormar02

Hy..
I have the DA7800 with PC7..
what kind of battery is necessary? where I can find it in europe or in Italy?

After opened the SRM, changed the battery and solded the battery, how I must close the plastic plate?
I must use some kind fo glue to avoid the water come into? :welcome:

Ypsylon
Posts: 1403
Joined: Wed May 24, 2006 6:25 pm

by Ypsylon

The links to the battery are in this thread. I got a couple of the ones that said they were for a data logger and that went really well and fast, but creating an account with that webshop was a bit difficult and IIRC only in German. Let me know if you need help with that.

There is a rubber ring in the metal casing and you seal the entire thing by tightening the chain ring bolts.
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Tug Boat
Posts: 196
Joined: Tue Oct 30, 2007 3:09 pm

by Tug Boat

My turn.

Just picked up and installed a used SRM DA 7800, with a PCV. Wired. I get speed, but nothing from the actual SRM. I thought it was the batteries, but when I checked them with a voltmeter, I get 3.5 out of each (I have the rectangular ones). This makes me think I've got the pickup installed wrong.

I have the harness that goes on the cable guide under the BB. Mine is sandwiched between the cable guide and the frame, and the sensor is about as close to the white plastic cover as I can get it. But I'm wondering if the sensor is in the correct place. Should it go on top of the cable guide, as far from the frame as I can get it?

Here's my set up:
frame
sensor
cable guide.

I'm wondering if it should be:
frame
cable guide
sensor

If not, any thoughts on what's going on. Good battery voltage but not picking up any SRM data. Thanks for the help.

TB

sungod
Posts: 1539
Joined: Fri Dec 24, 2010 9:37 pm
Location: it's raining, it must be uk

by sungod

srm says...

For wired SRM Systems, the proper placement of the sensor cable is crucial for power measurement. Be sure that the sensor is placed so that magnetic end is over the Reed Switch, and the white square printed on the sensor is over the sending coil. If using the new style sensor cable (which mounts under the derailleur cable guide) be sure that the top of the plastic housing installs level to, or slightly higher than, the sending coil. From this position you can then move the sensor closer or further away, adjusting for proper transmission.

...not sure if that helps or not

otherwise, read the manual... http://www.srm.de/index.php/gb/support/ ... em-english

Geoff
Posts: 5120
Joined: Sat Dec 13, 2003 2:25 am
Location: Canada

by Geoff

Personally, I don't like the SRM instruction for the sensor instalation of the wired SRM.

I find that the best place to install the sensor (rear speed) is atop the chainstay at the junction of the chainstay and the bottom bracket. That way, you can more easily move the sensor to ensure that it lines-up with the sending coil.

Attach it with a dab from your wife/GF's glue gun, test it, then run a big bead around the base of the sensor once you confirm a signal.

bricky21
Posts: 1405
Joined: Tue Sep 14, 2010 3:28 pm

by bricky21

Tug Boat wrote:My turn.

Just picked up and installed a used SRM DA 7800, with a PCV. Wired. I get speed, but nothing from the actual SRM. I thought it was the batteries, but when I checked them with a voltmeter, I get 3.5 out of each (I have the rectangular ones). This makes me think I've got the pickup installed wrong.

I have the harness that goes on the cable guide under the BB. Mine is sandwiched between the cable guide and the frame, and the sensor is about as close to the white plastic cover as I can get it. But I'm wondering if the sensor is in the correct place. Should it go on top of the cable guide, as far from the frame as I can get it?

Here's my set up:
frame
sensor
cable guide.

I'm wondering if it should be:
frame
cable guide
sensor

If not, any thoughts on what's going on. Good battery voltage but not picking up any SRM data. Thanks for the help.

TB


I was never able to get a signal when mounting the sensor under the cable guide. I had to mount it on top of the guide and it worked well, but it's a pita. I modified a shimano cable guide so I could bolt the sensor to the guide separate from where the guide mounts to the bottom bracket. I dremeled out the bottom of the guide so it could accept a brake pad holder T nut and fastened the sensor to it with a short m4 or 5 bolt. For some reason I could never get the sensor to stay put when I mounted it using the bolt that holds the cable guide to the BB :noidea: It would work for a while but then all of a sudden at the worst time I'd loose the signal, because the sensor rotated.

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