Please test your batteries

I want to give everyone a heads up for the batteries you have in inventory. Your batteries may have been idle for the past year or two and may no longer have the capacity they did when new. It is best to perform some sort of test to determine your batteries still have sufficient capacity to use during a match. You can use one of the many load testers or you can use a CBA from AndyMark or West Mountain Radio. You could also run sample matches with an old robot to see if the batteries will hold up in a three minute match. I am finding some of our inventory has vastly reduced capacity.


Tested 11. 8 failed. Still testing the rest. Test your batteries or you WILL be disappointed.


And of course, don’t just toss them. Run with an inverter for scouting tablets and laptops, old robot demonstrations, solar panel projects, etc. I’ve even been using a “dead” battery with an adapter cable to jump start a few dozen cars. Way better than those $60 jump packs that usually just melt.


I totally fried one of those the only time I needed it. Are there any inverters you recommend?

I haven’t bought a 12v inverter for a few years, but my recommendation system has just devolved to Googling “[thing] reddit” and usually you’ll get some detailed reviews and recommendations from relevant communities, not just ‘randos’ on Amazon. I imagine the vanlife people have some pretty solid choices.

Also recently found this website for jumper cables, as some people have been asking about premade SB50 cables: Anderson SB50 Copper Battery Cable Assembly 6 Gauge AWG w lug/terminal/clamp
Might have the swap the housings, iirc the grey plug doesn’t fit the red one, but a 3’ full copper cable with all the crimps done already is $20 shipped.


So next steps:

What’s the best place to buy batteries?

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While true, they are unfortunately currently backordered. Not that it stopped us from ordering from them still, just later delivery than we’d typically like.

What’s MK? If you call and tell them you’re with FIRST they typically have some discounts/free shipping.

We used to buy MK batteries where the shipping cost alone was the entire $400 voucher. >.<
Now we are lucky to have sourced it locally in Hawaii.

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Even if batteries appear to work well, still test them well, and check how old they are! I’ve had some experiences with 8-10 year old batteries in FRC matches and that did not work out particularly well.

“We believe we will be able to start filling orders in early March” is what I got from MK…so I ordered eight batteries from a local battery place. They’re not the exact brand/specification I was hoping for, but they are batteries!

We use those and are happy with them: AmazonSmile: Wagan TrueRated™ 400 Watt 5V 2.1 Amp Continuous Power Inverter with USB Charging Ports - EL2003-5 : Automotive

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Excellent tip. We had a couple of teams visit our facility last season to use our practice field. They were experiencing noticeable battery issues with their batteries that had been sitting idle for months during spring / summer / fall 2020. Really stinks, as that’s a significant investment to replace those.

Adding an inverter and an old battery to your robot cart is SUPER helpful!
And, it can also deliver 12vdc for LED bling :wink:

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I’d go with a pure sine wave if you can.

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For that sweet clean power feeling!

We tested our 8 “in rotation” batteries today, with the battery beak, which said they’re all OK. I don’t know what OK means though…what is a threshold internal resistance number? or 18 amp load voltage reading?

We also put the BB on a couple of the “old” batteries, they’ve not been charged for a long time, so I think they’ll probably all get recycled. What to do with a dozen cable harnesses?


Make sure that the screws holding the battery cables on the battery terminals are tight. A loose connection will cause a voltage drop when discharging the battery and make it appear to be worse than it really is. It will also cause a voltage drop when charging the battery and since the charger senses the voltage on the battery cables, it will terminate the charge before the battery is fully charged. It should not be possible to move the battery cables using one finger and thumb.

Should one find batteries that can not be used any longer, for any purpose, recycle them by taking them to your local auto parts store. I just took in two smaller SLA batteries from a UPS and the alarm system in my house to O’Reily’s and they gave me a gift card for $20 ($10 per battery). It may be worth contacting them by phone to make sure they will take a battery that did not come from a car since the staff at the auto parts store are quite variable.