Using 5 1.2V rechargeables to reach 6V?

I have a couple of things* that use 4-AA creating 6V. As you know 4 rechargables gets you 4.8V.
So I’m thinking of using a battery box and using 5 rechargeables = 1.2V X 5 = 6V

Am I looking at this right?

*An LED & fiber optic lighted girly house thing and the remote thermostat for my pellet stove.

Thanks in advance.

Alkaline AA don’t have a voltage much higher than Nimh :

Even at very light load (as in a remote) :

A properly designed device that uses AA cells will keep working until ~1V (per cell), and so will work just as well with Nimh cells.
That said some not so well made devices will stop working at a higher voltage like 1.3V and won’t work for long on Nimh (but also will lose a lot of runtime on alkaline). You can check that by measuring the voltage of the cells when the device stop working.

Anyhow just try with 4 first.

If I do a static, no-load voltage test on a cheap alkaline battery it will show about 1.54. Same test on an Energizer “Ultimate Lithium” battery is 1.67. I just tested several NiMH batteries right after fully charging them on a Nitecore charger and got 1.4 V. I find it hard to believe that both types of batteries would give about the same voltage under load. Yes, you can use 5 NiMH in series to get 6 volts.

I wasn’t aware you could buy 5 battery AA holders but apparently they are used for Arduino to get 7.5V. I used to buy stuff from China where these are as cheap as $2 but the shipping charges and long transit times make that unfavorable compared to buying them from a US seller on eBay. You can get a pair of holders for $7 with free shipping 2x 5-AA Slots Battery Holder Case Spring Clip Plastic Storage Box Series 7.5V | eBay.

It usually is not a problem. Most devices that I have used that are designed to run on alkaline batteries run just fine, or even better on NiMH batteries. Just try using your device with 4 x NiMH batteries and see if it works.

There are a couple reasons for this. First of all, a historical difference in battery voltage ratings. Alkaline batteries are referred to as 1.5V batteries, but they actually only produce 1.5V when they’re almost completely full, and under light loads. They effectively got rated at their peak voltage.

In more recent years, it became common to list battery voltages based on the average voltage over the course of the discharge. NiMH cells are listed as 1.2V because of this, but they’re actually typically around 1.4V when fully charged. Alkaline and NiMH voltages are closer than the labeled voltage suggests.

The load is also important. At 10mA current draw, a load at which an AA battery would last over a week, alkaline AA battery that is 3/4 full will be at about 1.4V. An NiMH battery in the same conditions will be at about 1.3V. Very similar, but the alkaline battery has a slightly higher voltage.

Increase the load to 500mA, which is a realistic load in many flashlights or motor-driven devices, and the 3/4 full alkaline battery has had its voltage sag to 1.2V, while the NiMH battery is still very close to 1.3V - at these higher loads, the rechargeable battery actually can maintain its voltage better.

One of the implications of this is the types of devices that don’t run on NiMH batteries also tend not to run well on alkaline batteries. The alkaline battery likely has most of its charge remaining when such a device stops working, because the designer did not give it very much flexibility for the voltage it can use.

Interestingly, I get a lot of free alkaline batteries as a result of this. Any time I need batteries, I grab a handful out of the recycling bin at work. I’d say at least 25% of them are over 1.4V. Clearly there are a bunch of devices that didn’t run well at lower voltages (I think it’s the walkie-talkies the maintenance crew uses), so they throw out far more batteries than they should need to.

In the heater thermostat receiver I used Re chargeables for around two or three weeks until they wouldn’t work, then swapped out to alkaline AA’s and it is fine.

On the LED toy, things were dim. I put in alkaline AA alkies and it was all good.

Thus, I was thinking of powering with five rechargeables = 6 Volts in series. Can anyone see anything wrong with that?

Depends on the toy. If it’s any kind of well made, you should be fine. If not, and the batteries are fully charged, the magic blue smoke required to make the toy function may get loose…

OK, you can pull the somewhat depleted NiMh and put in Alk and it works. How long do the Alk actually work?
If its somewhat high draw, the NiMh should work better.
If it’s low draw the NiMh should work better.
If it’s……very….low draw the Alk may ‘outlive’ NiMh, but with 3 weeks use it seems like that is not the issue.
Which brings up an important issue……what BRAND, how OLD, and what QUALITY are your NiMh? You could be using poor cells. Rarely does an Alk work better than a good NiMh.

The problem can be devices that are very voltage specific. Fortunately they are few. (some electronic locks seem to be like this)
This can be a place the 1.5v lithium rechargeables actually are superior. They are relatively expensive, quality is quite variable, and opens up another issue to deal with.

I’ll keep you posted. Battery boxes on the way.

Regarding 1.5V lithium rechargeable: when Eneloop sells them, I’ll buy them.

EBL’s 1.5 rechargeable:
From reviews I have read may be selling “pulls” from recycled battery packs. A fancy label and Made in China, does not warm mynheart.

Doubt Enloop will ever sell them. To date they have nothing to do with lithium of any sort I know of.
I’ve no great love for EBLs of any variety. They are likely just a rebrand anyway. I’m not sure EBL makes any battery at all.

I do have a dozen Tenavolt, which HKJ reviewed.
2 years of use and I’m satisfied…so far. BUT, I bought them on significant sale, about the same price as Eneloop. No way would I buy them, or any 1.5v lithium at the standard retail price.

I like to use energizer ultimate lithiums in things that i’ll rarely get to. They come from the factory in nest co/smoke detectors. The six in it lasted around 5 years even with the nightlight function on med. I also put one on a time of day switch on the waterheater. It took a single aa and I’d never want it getting ruined by a alkaline and it lasts way longer than an eneloop.
They won’t leak like every single alkaline eventually will and they should last a very long time. Other than that I use eneloops in everything and haven’t had any problems.

I’ve done it many times. worked every time. but in your case the load is very small, use low self discharge cells, or the cells may be self discharging at faster rate than due to load

What charger are you using? I only realised how good rechargeable NiMH cells are when I stopped using dumb chargers which didn’t charge the cells separately…