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TDI Pro - External Battery Pack
Posted by: sandbandit
Date: July 15, 2017 02:32AM
Got creative recently and made an external battery pack for my TDI Pro - mostly because the stock battery was no longer available when I purchased my machine (no spare battery), and the stock battery it came with doesn't last very long in the field (about 4 hours of good power). The stock battery is 14.4 volts / 4.8 amp hours.

The new battery pack consists of 12 rechargeable "C-cell" NiMH batteries, wired in series (1.2 volts each x 12 batteries = 14.4 volts) held together using two 6 "C-cell" battery holders wired together "+" to "-". Fresh off the charger the voltage measured a safe 15.69 volts (less that the 18.5 volt maximum for the TDI Pro). Each battery is rated at 5000 mAh (5 amp hours = 1 amp draw for 5 hours), and when all 12 are connected in series it has 60,000 mAh (60 amp hours = 1 amp draw for 60 hours).

The TDI Pro draws 0.6 amp, so from a full charge to zero power = 100 hours (60 divided by 0.6). Naturally, battery capacity ratings are typically overstated so actual performance is less.

The bottom line is that this battery has a LOT of stored power, and I can to hunt for several days without having to worry about a low battery. No need to carry a spare battery either. Recharging is pretty fast - I recharge all 12 batteries at once in 3 EBL chargers - it takes about 3 hours.

The new external plug-in does not defeat the original design, so you can still use the stock battery inside the box by itself if you want. The cost to assemble everything was reasonable (12 batteries, 3 chargers, 1 pouch, 1 web belt, 2 battery holders, and assorted wiring) worked out to be less than the price of a new stock battery.

Pros: Long battery life (14.4 volts / 60 amp hours)
Lighter metal detector (stock battery removed)
Fast recharge time

Cons: Batteries must be removed from holder for re-charging
Battery pack is carried on your waist with a web belt




Re: TDI Pro - External Battery Pack
Posted by: Jim in Idaho
Date: July 15, 2017 07:37AM
Nice work, Bandit!
Jim

Re: TDI Pro - External Battery Pack
Posted by: sandbandit
Date: July 15, 2017 12:52PM
Thanks Jim! It's been on the drawing board for a little bit.

I also made a 1 x 12 "D" cell battery pack at the same time - it has twice the power (120 amp hours), the same voltage, and plugs in just like the 1 x 12 "C" cell battery pack. It weighs a few pounds, but you could probably hunt for a week with it! Would be perfect for long hunts - prospecting style.

Richard
San Diego

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Re: TDI Pro - External Battery Pack
Posted by: amberjack
Date: July 18, 2017 04:15AM
if your volt meter is right and you have wired in series which the volts would suggest your mah is only that of one cell, sorry to be the bearer of bad news. :blink:

a better plan would be to use li ion 26650 cells 4.2 volts fully charged per cell and get to your volts fast and have on average about 5000 mah per cell so 4 cells would get you to 16.8 volts and then wire the packs in parallel so then each pack of 4 cells would then up your capacity by 5000 mah so 2 packs of 4 10000 mah , 3 packs 15000 mah etc..

still great idea and should serve you well just your math is a bit out, not to worry :biggrin:

AJ

Re: TDI Pro - External Battery Pack
Posted by: Jim in Idaho
Date: July 18, 2017 09:36AM
LOL....you're right, AJ! I was complementing him on his work...didn't really pay attention to his configuration. Wouldn't it be nice if that pack delivered that many amp/hours?
jim

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Re: TDI Pro - External Battery Pack
Posted by: amberjack
Date: July 18, 2017 10:09AM
I like the set up Jim all to do now is amp it up with some lithium and it will last for longer than I can detect so full marks for the set up from me just change the batteries and a little bit of wiring :biggrin: and detect a long time at full power.

don't worry I had to look twice :buds:

AJ



Edited 1 time(s). Last edit at 07/18/2017 10:10AM by amberjack.

Re: TDI Pro - External Battery Pack
Posted by: Jim in Idaho
Date: July 18, 2017 11:32AM
Yeah...nice thing about an external pack is you can make it as big as you want. I find my 4 cell Li-ion gives me about 6.5 hours max in my TDI SL, which is longer than I can usually stand to run it anyway. Still would be nice to have another pack ready to go. My 4 cell pack is made up of 3400MAH cells. I rarely run it all the way down to 3v/cell, however....that's hard on the batteries.
Jim



Edited 1 time(s). Last edit at 07/18/2017 11:34AM by Jim in Idaho.

Re: TDI Pro - External Battery Pack
Posted by: sandbandit
Date: July 19, 2017 02:32AM
Yup - you're right. That didn't work out like I had hoped for - was sure I had it roped. Ran it today at the beach - it lasted most of the day, but you're right, it tapped out around the 5000 mAh limit. Oops - back to the drawing board - will try your 4 x AA Lithium pack suggestion next - maybe 4 to 6 packs wired in parallel to raise the mAh run time. Thanks for pointing that out AJ.

Richard
San Diego

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Re: TDI Pro - External Battery Pack
Posted by: amberjack
Date: July 19, 2017 04:29AM
Not to worry Richard I have made heaps of mistakes we all have just most cant admit it, google li ion 26650 cells or 18650 cells and read a lot, 18650's are most used I have made packs for all sorts of detectors there are 4 cell holders on ebay for like $1 each 3 of those would give you about 10000 mah get a couple of chargers , have a look at fasttech they have brand name cells at a good price, anyway do some research and see how you go :biggrin:

for the TDI I would go 2 packs of 4 of the 26650 cells that's going to give you around that 10000 mah which has to be enough for a looong day detecting..

good luck and well done once we get over having to shove the cells in the detector the whole world opens up. so you are well past the 1st hurdle :bouncy:

AJ



Edited 1 time(s). Last edit at 07/19/2017 04:31AM by amberjack.

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Re: TDI Pro - External Battery Pack
Posted by: amberjack
Date: July 19, 2017 08:52AM
Richard another option is lipo and people seem to run when the hear lipo but I can tell you RNB use lipo battery's in their excel pack never heard anyone have any dramas as like you have said detectors don't pull huge amps and they can be slow charged so its not a bad option as in ease one battery.

https://hobbyking.com/en_us/multistar-high-capacity-4s-10000mah-multi-rotor-lipo-pack.html?wrh_pdp=3 this is 16.5 volts fully charged and only need one charger https://hobbyking.com/en_us/turnigy-accucel-6-80w-10a-balancer-charger-lihv-capable.html?wrh_pdp=3 have the charger here charge anything with it but great for the lipo as it balances with those 2 connectors.

I know it sounds a bit confusing but its not really :biggrin:

just have to spend some cash is all which is par for the course with detecting isn't it :punch:

they make a 15000 mah one as well but that's starting to get over a kilo ...

just more options !!

AJ

Re: TDI Pro - External Battery Pack
Posted by: sandbandit
Date: July 23, 2017 01:12PM
PERFORMANCE CORRECTION

The 1 x 12 "C" NiMH external battery pack produces 5,000 mAh (similar to a single stock battery in power - but pretty heavy at 2.2 pounds)
The 1 x 12 "D" NiMH external battery pack produces 10,000 mAh (similar to 2 stock batteries in power - but much heavier at 4.5 pounds)

My apologies to the Forum members for my posting of inaccurate power ratings for the 1 x 12 batteries. AJ was correct in pointing out this mistake, and recommending the use of 26650 (or similar) Lithium Ion batteries which have a much better power-to-weight ratio. For example: a 1 x 4 Lithium Ion 26650 battery pack (16.8 volt / 5,000 mAh) would weigh about 13.85 ounces (less than 1 pound), and a 2 x 4 Lithium Ion 26650 battery pack (16.8 volt / 10,000 mAh) would weigh about 27.71 ounces (less than 1 3/4 pounds). Much better power-to-weight than NiMH batteries.

Thank you AJ for your recommendation!

Richard
San Diego

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