EI back up power (concept)

[Freemasm]

This is a truly bad idea for less than obvious but well discussed reasons; the relative safety associated with the different chemistries.

Assuming the DeWalt is LIon = potential for runaway thermal events. Fires and aircraft are a bad combo. Very low probability, very high consequence.

The Life chemistry of the referenced purpose made batteries has a different catastrophic failure mode but one that is fairly easily managed.

No thanks for the drill battery approach for me.

[Walt]

TCW has been making backup batteries for quite some time and I’ve installed many, never heard of any problems. May cost a little more but it works well for it’s intended function.

[Bcone1381]

Lots of good stuff here regarding EI and Battery backups.

Back up batteries have a human risk factor we need to keep in mind. They are kind of like checking the air pressure in your spare tire...never is not the right answer. Like the spare tire, they sit and do nothing for most of their lives. We forget they deteriorate over time.

It might be a good idea to place limitations on your backup batteries. Inflight test, Load Test every so often, replaced every so often. Etc. Dual EI really needs some thought put into this arena. A backup alternator gives relief from this human risk element of forgetting to check the backup battery and may be less weight and cost in the long run.

[rv8ch]

Originally Posted by Walt

TCW has been making backup batteries for quite some time and I’ve installed many, never heard of any problems. May cost a little more but it works well for it’s intended function.

I agree completely. These TCW guys are much smarter than I am (not hard) and have designed their solution to handle things most of us have not even thought of. The instructions are very clear, professional, and updated regularly. They now have FAA certification for their products. Not saying that "FAA Certified" automatically means "good", but it shows a serious investment in time, and rigor in testing and documentation.

Here's a link to some of the documentation - I found it very impressive.

https://www.tcwtech.com/product/inte...p-system-ibbs/