Batteries

ZOR

Senior Member
I am wanting to build batteries in a project to supply 9 volts.

I looked at AA and PP9 batteries and then came across lithium version of PP9.

Are the lithium batteries the best choice for getting 9 volts? Are there fire risks on battery discharging too low? Can I use a normal battery charger that takes ordinary PP9 batteries to charge these batteries. I will be drawing some 72ma when the unit is switched on (by a switch) It's a wireless remote control so use when on will not be lengthy. Thanks
 

premelec

Senior Member
I have used a single lithium battery with up converter for this sort of use... input current from battery about 4x output at 9volts... if there is danger of leaving the unit on over discharge device should be used to prevent battery from draining too low... i bought the devices on ebay at pretty low cost... you can used more cells in series to get the 9v and then have to have some sort of management to keep a cell from overdischarge in the string as well as preventing overcharge of a cell...
 

AllyCat

Senior Member
Hi,

Give us some links to the batteries you've "come across" and we may be able to give a more detailed reply. BUT...

Personally, I've never heard of a "lithium version of PP9", nor a "normal battery charger that takes ordinary PP9 batteries", since "normal" PP9 batteries are non-rechargeable. The only "9 volt" rechargeable batteries I've encountered are NiMH "PP3", but care is needed in their selection: The majority contain 6 cells so deliver only 7.2 volts; the better ones have 7 cells so at least give around 8.4 volts. They're generally trickle-charged at low current and probably used in applications where the number of recharge cycles is of little interest. Try to find the Low Self Discharge (LSD) type.

Most lithium rechargeable batteries deliver 3.7 volts (4.2 absolute max) per cell, so you'd have to choose between a nominal of 7.4 volts or 11.1 volts. Alternatively, 3 x LiFePO4 (Lithium Phosphate) cells would give a nominal 9.6 volts and are a good rechargeable technology, but quite hard to find. The nearest to 9 volts would be a stack of 3 rechargeable versions of the CR2032 or CR2532 "coin" cells (3.0 volts each) as used in some RTC modules, but I doubt if they'd be good for 70 mA.

Generally, battery chargers must be designed for the correct cell technology. Unless the specification of a charger specifically states that it is suitable for the exact type of battery, then you can assume that it isn't ! The only exception is that you might "get away with" trickle charging NiMH or LiFePO4 cells, if you're not too worried how long they last.

Cheers, Alan
 

Circuit

Senior Member
Personally, I've never heard of a "lithium version of PP9
Neither had I until I came across this; https://www.cef.co.uk/catalogue/products/1216270-9v-pp9-lithium-battery-1-pack
But it illustrates a PP3 battery. Perhaps this is confusing the enquirer?

I suspect that Zor is confusing PP3 and PP9 - Non-rechargeable PP3 lithium batteries are commonly available to give a 10 yr power source to smoke detectors, but again I have not come across 9 volt rechargeable lithium batteries of this size - and of course the common rechargeable lithium ion chemistry would produce multiples of 3.7 volts - so 9 volts is not achievable as you say.
 

hippy

Technical Support
Staff member

AllyCat

Senior Member
Hi,

Yes there appear to be several examples of PP3 batteries being misquoted as PP9, and many more "9 volt" batteries that aren't! According to Wikipedia, Lithium rechargeable "PP3"s are nominally 7.4 volts, like the cheaper (6 cell) NiMHs.

That might be perfectly acceptable because "Carbon" and Alkaline batteries may start at 9 volts, but this progressively falls, with the manufacturers only specifying their "end of life" at significantly below 6 volts. It depends why the OP has requested 9 volts; for many applications 7.5 volts will be fine, but if 9 volts is needed to drive a varicap or avalanche diode, for example, then he may be disappointed.

The "USB batteries" contain a dc-dc converter, similar to a "power bank". That's fine for charging the cell(s), or for transferring charge to another battery, but to supply a "continuous" voltage, the losses in the (step up) conversion process will soon flatten the source. Actually, almost any Lithium rechargeable battery should contain a protection circuit to prevent excessive charge and/or discharge, but often it's not clear which ones do.

Cheers, Alan.
 

premelec

Senior Member
Example Up converter pictures; Li to 9v

Example of kluged old battery pack lithium with battery to switch to protection to up converter to 9 volts -The parts are small and cheap.
 

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ZOR

Senior Member
Please, Please excuse me not getting back sooner, problem with family member took me away. Yes I saw PP9 mentioned on one search, but it's a PP3 Size I was wanting. The lithium battery I saw was PHILIPS LITHIUM ULTRA 9v BATTERY PP3 CR-V9 U9VL U9VL-J L522 MN1604 SMOKE ALARM on Ebay.

I was unsure if Lithium batteries had their own discharge protection. The battery is not rechargeable. The batteries out there are a minefield to choose. Many quote crazy mHa figures, many cheap Chinese fire starters. I will read all these excellent replies and make my mind up. Many thanks again all for the welcomed help.
 

Flenser

Senior Member
Zor,

My understanding is that the Batteries that use a chemistry which is not rechargeable are refrerred to as primary and those that use a chemistry which are rechargeable are referred to as secondary.

This applies to lithium batteries as well and there are primary Lithium batteries on the market.

A quick google came up with this link to a Phillips web page: http://www.p4c.philips.com/cgi-bin/cpindex.pl?ctn=6FR61LB1A/10&dct=QAC&faqview=1&mid=Link_FAQs&refnr=0111815&scy=SI&slg=AEN&view=aa12_view_partial.html
Where the answer to the FAQ question "Can primary batteries be recharged ?" is "Primary batteries (Philips LongLife, Power Alkaline, Ultra Alkaline, Premium Alkaline, Lithium Ultra) cannnot be charged. .... In fact, charging primary batteries can cause them to leak, become very hot and cause explosion."
 

srnet

Senior Member
Zor,

My understanding is that the Batteries that use a chemistry which is not rechargeable are refrerred to as primary and those that use a chemistry which are rechargeable are referred to as secondary.

This applies to lithium batteries as well and there are primary Lithium batteries on the market.

A quick google came up with this link to a Phillips web page: http://www.p4c.philips.com/cgi-bin/cpindex.pl?ctn=6FR61LB1A/10&dct=QAC&faqview=1&mid=Link_FAQs&refnr=0111815&scy=SI&slg=AEN&view=aa12_view_partial.html
Where the answer to the FAQ question "Can primary batteries be recharged ?" is "Primary batteries (Philips LongLife, Power Alkaline, Ultra Alkaline, Premium Alkaline, Lithium Ultra) cannnot be charged. .... In fact, charging primary batteries can cause them to leak, become very hot and cause explosion."
Which is a good example of do not always believe what you read on the Internet.

I have had an Alkaline battery charger for a good many years, if you re-charge before they go completly flat then you might get up to 5 re-charges out of them, not perfect of course, but there are sometimes good reasons for using Alkalines over other rechargeable batteries.
 

ZOR

Senior Member
Thanks srnet. As you agree, there are so many false claims out there for batteries, many really risky to use Chinese firelighters. Even CE approved etc labels can be faked. I have seen Duracell AA batteries with 2100mAh. Best regards
 

srnet

Senior Member
What I cannot remember is whether you can charge Alkaline batteries that are a series of cells, such as the PP3.

I recall the charging process involves a pulsing the cell with short duration reverse charges, not sure how that would work for cells in series.
 

erco

Senior Member
I received my 9V lithium battery from Banggood today. Nice little unit, it's rated at 400 mAh capacity and actually tested at 350 mAh, lower cutoff 8.1V, steady 90 mA discharge current. Not bad and much closer than most Chinese battery claims. Red LED charge indicator on bottom goes out when fully charged.
 
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