12v Li-ion to power 15v

[jimmyjimmy19702010]

The long, thin 12volt SLA batteries could be a solution if they could be made to fit. Old tech but very dependable and safe. A good quality automatic SLA 12v charger won’t break the bank either.

 

[mulaz]

i had the same idea and tried the exact same battery it did fit but i just couldn't get the battery cover on without having to start chopping away at the plastic internals!

 

[Reli]

These are only 1.2V instead of 1.5v, in a device expecting 15V i wonder if this is a significant enough drop to affect performance?

I use Tenergy Premium whites. I charged them last Friday and they reached 1.37 or 1.38V. I put them in a radio and played it for maybe 15 minutes, and then took the out. That was 3 days ago. Today they're down to 1.35V. So bottom line, they perform a lot better than the promised 1.2V.

However, once they fall below 1.2V, they start draining really fast. Much faster than an alkaline.

Reli, almost all batteries have a phenomenon known as "surface charge" after a fresh charge. Google it if you want to know what it is. It's not nearly as pronounced in NiMH batteries but on lead acid type batteries, it's enough to require that the batteries be used for a bit to bleed out the surface charge before testing or else you will get a false reading.






I agree, but it must be a pretty long surface charge, because today (2 weeks later) I put them back into a radio, played some bass-heavy tracks for an hour, took them out and they're still showing 1.25 to 1.3V on my Fluke. So I feel I got more than I paid for.

 

[Transistorized]

These are only 1.2V instead of 1.5v, in a device expecting 15V i wonder if this is a significant enough drop to affect performance?

I use Tenergy Premium whites. I charged them last Friday and they reached 1.37 or 1.38V. I put them in a radio and played it for maybe 15 minutes, and then took the out. That was 3 days ago. Today they're down to 1.35V. So bottom line, they perform a lot better than the promised 1.2V.

However, once they fall below 1.2V, they start draining really fast. Much faster than an alkaline.

Reli, almost all batteries have a phenomenon known as "surface charge" after a fresh charge. Google it if you want to know what it is. It's not nearly as pronounced in NiMH batteries but on lead acid type batteries, it's enough to require that the batteries be used for a bit to bleed out the surface charge before testing or else you will get a false reading.



I agree, but today I put them back into a radio, played some bass-heavy tracks for an hour, took them out and they're still showing 1.25 to 1.3V on my Fluke. So I feel I got more than I paid for.


They're just really good batteries Reli. I have 30 of them that I use in rotation. I get the exact same results as you. Surface charge right off my charger is 1.39 to 1.47V depending on the cell. After 1 day 1.39V to 1.37V after 2 days of sitting 1.35V to 1.37V and after about a week 1.36 to 1.34V and hold steady there.

I have read every post here because I excel in battery technology and find it interesting chemistry. Superduper is spot on with everything he has said.

As we have already covered, NiMH in 10,000mAh size are expensive. We all know overcharging is bad however, one thing about NiMH batteries I have not seen in this post are the dangers of over discharging them. It is just as bad as over charging and is often overlooked or unknown. I am sure you want to keep them healthy for many years to get the most out of your investment. We have touched on smart vs dumb chargers to avoid overcharging. That is one way to kill them so......get a good smart charger. Over discharge is also Very life shortening and can cause a smart charger to refuse to charge them after just ONE offense!!! As mentioned by Superduper NiMH run with consistent results right up to the point at which they are depleted and then fall on their face. I should add that NiCad has this trait as well. On the Tenergy NiMH batteries, the rapid fall off point of depletion usually happens right around the 1.2V mark. 1.25 to 1.23V is about the halfway mark and 1.35 to 1.27 is fairly topped off and healthy

Here is where the danger comes in for most of us ruining these batteries in our devices and/or shortening their life tremendously.

When you are using NiMH cells in series (which we all are in our boxes to achieve the voltage we need), you have the potential for a weaker cell or cells in the group to fall below 1.0V (which is bad) but even worse you could get polarity reversal where the weaker cell is being carried by the surrounding healthier cells to the point where it goes beyond negative voltage from the current passing through it and actually Reverses it's polarity aka reads positive on the Negative end and Negative on the Positive post Even if it bounces back after charge this is a KILLER! That cell will never be the same even if it appears okay and reads good voltage after a charge. The longer you leave it in this discharged state the more harm you will do to it.

Best bet is to keep an eye on your boxes battery status indicator. It will read low to begin with due to the reasons that Superduper explained with 12V series NiMH vs 15V Alkaline series however, you need to get acquainted with your batteries, charger and your boxes battery status indicator/meter. Once you know where the needle or LED's sit on your box after a complete charge, keep and eye on it every now and then. When you are seeing the needle drop or LED start to indicate voltage change STOP! This is a sign that a cell or two is below 1.2V and this is a good time to charge. If your box doesn't have a battery status indicator check each cells voltage with a meter every now and then. When they avg 1.2 or less, you notice any cell that is 1.1 or lower or you notice a change in your boxes behavior stop and charge them.

Some may say to just go ahead and top off the charge after each use to avoid over discharging. It is true that NiMH batteries do not have memory like NiCad and this is good advice and a safe bet for those who have a high end professional charger but I find most people have consumer grade smart chargers. Not all smart chargers are equal. Mid grade consumer smart chargers do use delta-V to detect voltage drop (to indicate full charge) but can sometimes miss this since NiMH voltage drop is Very slight when the charge is complete when compared to NiCad. This can result in the batteries getting hot from overcharging if thermal cutoff is not part of your chargers secondary protection circuitry. This is bad as well....so for most of us, using the batteries until a voltage drop change is detected on our box is actually better. Your batteries should only feel warm when topped off. If they're almost too hot to touch while charging you are roasting them and your charger has missed the delta-V, does NOT have thermal shutdown and is over charging.

So, in a nutshell. If you want to have the best experience with these. Do not over charge (obviously) or (not so obvious) allow a cell to go below 1.0V or worse Reverse Polarity. Stop using your box and charge the batteries when any change is noted on your battery voltage indicator and you will have happy cells for many years to maximize your enjoyment and your investment.

I have 5 years on my first set of Tenergy D's. I have only noticed a slight marginal change when compared to the set I got this Christmas so what I'm doing must be working

 

[T-STER]

Thanks for this write up mate, I have been contemplating getting some tenergys or similar and trying to decide and decipher the technology and this has helped me make my decision