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

[goodboyr]

Could someone advice which battery to buy to replace the battery of a SRM DA 9000?

Remove the SRM from the bike and unbolt the torx head screws that secure the crank arm to the spider and you will then be able to remove the front cover with a precission screw driver. I cannot recall what the battery model was but unlike our Hollowgram SRM's, I was not able to source a direct replacement in the US, and you will need batteries with pre-soldered pigtails. As I cautioned above, the DA 9000 SRM uses a micro connector with 32-gauge wires, so unless you are a master with a soldering iron and micro electronic PCBs, I am going to dsuggest you send it to an SRM Sewrvice center. I managed to mangle the micro connector on mine, thus I had to send it to SRM anyway, but on the plus side, SRM updated the firmware so that now my Garmin displays the battery status under sensor details.

2 x Eve ER14250 1/2AA 3.6v 1200mah batteries

[Hoffy]

Replaced the battery just to see if that was the issue, works fine for a few day then starts to rapidly discharge after charging a few times. Indicating a short? Not really sure on what to do next, maybe send it in to SRM but then be charged an arm and a leg to look at it?

[sungod]

I just finished replacing the batteries on an SRM DA 7800. Second time I've done this. In Canada these batteries are 25$ each. As stated and shown, the connecting wires are thin gauge, soldered directly to the board. You need to be very carefull when stripping the insulation or you will pull the wires from the board. Which is what happened to me (probably because this is the second set I've changed in this srm). So I had to resolder them to the board. Amazing that after all these years, SRM doesn't use zero insertion force plugs to connect to the battery. And why do you think SRM needs such high amperage batteries in the first place? With two in this model, that's 1.5 amps! My guess is that they are lazy with the wireless design, so compensated by using lots of battery power. Downside of course is that when replacing these, be real careful with any bare wires. A short can release a lot of energy. I use small pieces of self vulcanizing rubber tape to insulate.

surely the battery choice is driven by discharge curve, operating range and the need for longevity

if the power drain was high the batteries would need changing far more often, mine lasts 2-3 years, that's a sign of good wireless design using very little power

i am tempted to fit connectors next time though!

[goodboyr]

A 2032 battery is 225 mah compared with the srm 7800 1500 mah. Using the quoted life from each manufacturer, a quarq Elsa is good for 300 hours on the 2032 battery. The srm quoted life is 1500 hours. So just ratio this (I know this is simplistic and it's a more complex question but at least this gives ballpark compares), the quarq is 25% more efficient. And a whole lot easier to deal with. Let us know how adding plugs goes. You must have super soldering skills.

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[Calnago]

Kudos to those who replace the battery successfully, but for my money I'd just as soon send it in to ensure it's all done, sealed up, and properly calibrated at the end of it all. The "efficiency" argument above is a bit like the strength of an ant analogy. For its weight, the ant is a pretty strong critter, but my little finger could crush that poor guy lickity split.
Most current SRM units have a battery life of 1900 hours, not 1500. And the Shimano SRM in particular has a battery life of 3000 hours. Let's see... supposing an average speed of 15mph (24km/h) that's 45,000 miles (~72,000km). I know some of you may put in mega miles per year, but 5,000 would be a good year for me. That would be 9 years of use before a battery replacement was required, or about 6 years on my lowly Campy SRM with its lesser 1900 hours. The weather sealing is excellent, it works, it's accurate... I guess I don't consider it a big deal to send a unit in for a new battery once every 6-10 years or so.

[goodboyr]

I'm sorry this is going a little off topic, but I don't know anyone that's gotten 9 years out of one. And only the da 9000 have the giant batteries.
Typically people get 2-4 years out of one.

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[Calnago]

Well, I'm still waiting for the battery on my first unit to die. So while I can't speak for others, my personal experience seems to be on track with what they claim and I have no reason to disbelieve it.

[goodboyr]

You need to ride more!
[emoji41]

[sungod]

A 2032 battery is 225 mah compared with the srm 7800 1500 mah. Using the quoted life from each manufacturer, a quarq Elsa is good for 300 hours on the 2032 battery. The srm quoted life is 1500 hours. So just ratio this (I know this is simplistic and it's a more complex question but at least this gives ballpark compares), the quarq is 25% more efficient. And a whole lot easier to deal with. Let us know how adding plugs goes. You must have super soldering skills.

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used to be in electronics design, i had years of making fiddly prototypes

thinking about it, better is to solder slide-on contacts to the ends of the srm wires, i.e. slide these onto the trimmed battery wires (which are around 0.8mm on a couple of spares i have). the key thing is making sure they won't work loose after months of vibration

[goodboyr]

That sounds like a great idea. Do you have a part number or description for those slide on contacts? As well, you should consider methods to insulate.

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[sungod]

That sounds like a great idea. Do you have a part number or description for those slide on contacts? As well, you should consider methods to insulate.

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this type is probably the most widely available...

http://www.hobbytronics.co.uk/cables-co ... res-ff-6in

...the header pins (aka berg pins) they're designed for are c. 0.64mm square, but probably will be ok on the battery wires, if a bit loose just 'tin' the wire with solder, or if you're careful you can extract the contact from the plastic cover and tweak the sprung contacts, if the cover is too bulky replace it with narrow bore heatshrink sleeving

remove existing wires from srm, cut the jumper lead to similar length, strip and tin ends, and solder in place

good soldering needs an iron at the right temperature, too hot (within reason) is better than too cold as you need to keep the iron on the pcb much longer to melt the solder, hot+fast transfers less heat into the surrounding area

use a magnifier to inspect the joint area afterwards, solder reel with multicore flux can splatter tiny balls of solder in the area, if not removed these can eventually become dislodged and cause shorts

[goodboyr]

Perfect! Going to give this a try on the next battery change I do. Thanks!

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[raulrock]

Guys, I hope somebody can help me.

I have changed batteries in several units. At least two wired ones, two dura aces wireless, also an cannondale and a sram wireless, but never in a MTB 1X model.

Does anyone has any idea on how to crack the 1X open? Would it open like the new ones from the 'face' side or like the old ones from the frame side? Was anyone able to do it?

Any help is welcomed, thanks!

[spandexboy817]

I did the battery replacement by myself and am having an issue I was hoping someone could shed some light on. Its a 2014 Wireless Sram SRM. Anyways, replaced and resoldered the two batteries and put it all back together. Cadence is working fine, it pairs fine, calibration is fine, but I am getting no power numbers. I pulled it back apart, made sure all the solder was good and the correct wires were going to the right places, and made sure all the wires connecting the strain guages to the circuit boards were happy... Wondering if maybe one of the batteries or the connector that the batteries are soldered to is bad?? Any help would be great! Thanks

[spandexboy817]

I did the battery replacement by myself and am having an issue I was hoping someone could shed some light on. Its a 2014 Wireless Sram SRM. Anyways, replaced and resoldered the two batteries and put it all back together. Cadence is working fine, it pairs fine, calibration is fine, but I am getting no power numbers. I pulled it back apart, made sure all the solder was good and the correct wires were going to the right places, and made sure all the wires connecting the strain guages to the circuit boards were happy... Wondering if maybe one of the batteries or the connector that the batteries are soldered to is bad?? Any help would be great! Thanks