Rc-M70 Battery pack mods

[Mark34]

Has anyone here created, or know of a rechargeable battery pack mod for use in the JVC RC-M70 (or other similarly sized boxes)?
I did find a you tube video of someone who had it in his, but he doesn't describe how he did it or where he got it. I tried to contact him, but no response as of yet.

Also, Has anyone tried, or had success using the AA battery to D size converters for the rechargeable AA's to power these larger boomboxes. I have A few of the converters, but I don't have 10 of them for the M-70, which it requires, to try it myself. I'm willing to get more if anyone knows if this method works (obviously it would be for a much shorter playing time).

Thanks

 

[Superduper]

I’m sure it would work but you’ll get short playing time like you are aware. Why don’t you get the actual D sized nimh batteries instead? Yes they’re expensive but you won’t need adapters and they’ll last a real long time.

 

[Reli]

Tenergy nimh 10,000 mAh

 

[Mark34]

Thanks guys!...I've seen some reviewers say that D size rechargeables are actually AA's in shells tho?...Tenergy is an honest brand tho?

 

[floyd]

Thanks guys!...I've seen some reviewers say that D size rechargeables are actually AA's in shells tho?...Tenergy is an honest brand tho?

I've been using these batteries for about 10 years and I've never had any problems .

 

[Mark34]

Thanks, I'm on Amazon Now! Wish they had 10 packs...8/12/16 seem to be the standard

 

[Mark34]

What charger do you use for these? The dedicated one, or another brand that can charge more than 4 at a time?

 

[Superduper]

Thanks guys!...I've seen some reviewers say that D size rechargeables are actually AA's in shells tho?...Tenergy is an honest brand tho?

If they’re cheap, they might be AA stuffed but true D cell ones are pricey compared to the C and AA ones, and they will weigh as much as a true D cell. If they’re light, like a AA battery with a plastic shell, well then you know what’s up. BTW you might can get away with C cells if you can find C to D cell spacers. I use the nimh C cells for high intensity flashlights and they last a really long time.

 

[Reli]

Thanks guys!...I've seen some reviewers say that D size rechargeables are actually AA's in shells tho?...Tenergy is an honest brand tho?

Those people must not be reviewing the right product. Tenergy Premiums and Tenergy Centuras are indeed real D-cells, not AAs stuffed into a D shell. Otherwise there's no way they'd be able to get 10,000 mAh out of them. And they weight just as much, if not more, as an alkaline D-cell.

If you don't plan on using them regularly, like every week, then I would recommend the Tenergy Centuras instead of the Premiums. The Centuras are "Low Self-Discharge" and keep their charge a lot longer than the Premiums do. With the Premiums, if you let them sit around for a couple months or more, they will drop below 1.0V, sometimes way less than that, forcing you to use a special "trick" to get the charger to accept them.

 

[floyd]

What charger do you use for these? The dedicated one, or another brand that can charge more than 4 at a time?

I use the universal rapid charger it only holds four batteries at a time.

 

[Superduper]

I use the universal rapid charger it only holds four batteries at a time.

Me too, takes 3 charge rounds to refill 10 cells. Luckily you don’t need to do it that often.

 

[Mark34]

Thanks guys for all your advise. I ended up buying a 14 pack of Duracell's from Costco. When I originally had the M70 in the 80's that was the way to go (but I can't recall how long a set lasted). So, I'm trying a set of these first to see how long they last. I'm mostly going to have it plugged in when I'm home, but still want the option available to take it elsewhere without the plug.
If the length of playtime is not satisfactory for the regular D cells, I will get the Tenergy set up! I will advise

 

[Superduper]

If you stuff the unit with alkaline batteries, but you mostly use the plug, be mindful that the batteries will drain and you will probably forget about them being in there since you probably won't use it often enough to notice the batteries getting low. When alkaline batteries drain down to a certain point, the internal chemical composition causes the cells to expand and burst leaking battery acid that's going to do a real number (not in a good way) on the battery compartment and all the springs and contacts. I would suggest you either leave 1 or 2 cells out, stuff them back in when you need to go portable.

 

[Mark34]

If you stuff the unit with alkaline batteries, but you mostly use the plug, be mindful that the batteries will drain and you will probably forget about them being in there since you probably won't use it often enough to notice the batteries getting low. When alkaline batteries drain down to a certain point, the internal chemical composition causes the cells to expand and burst leaking battery acid that's going to do a real number (not in a good way) on the battery compartment and all the springs and contacts. I would suggest you either leave 1 or 2 cells out, stuff them back in when you need to go portable.

Great advice! Thank You

 

[Transistorized]

These pictured are over 8 years old. They are slowly showing signs of internal resistance going up and run time going down but they'll still run my C100 and M90 for 8 hours.

I have 3 sets of 10 because I am always swapping fresh charged for tired batteries every week or so. I use my radios a lot. Smart chargers will charge them separately and evenly. Smart chargers and not allowing their voltage to tank are key ways to make them last. At 1.2V it's time to charge. But unlike Ni-Cad, Ni-Mh doesn't form a memory so you can charge them anytime (with a smart charger).

Only potential issue are radios that do not have a battery indicator. This may cause you to tank a cell when using them in series. The radio will still operate with the other cells pushing a dead cell. Taking them below 1.0V isn't good for them.

But if you do everything right and are responsible with maintenance, they'll run the most power hungry box for up to 12 and 14hrs during their peak period for many years.

They do weigh a little more than an Alkaline but I've not seen one of these leak which is the worst thing that can literally happen to your radio.

If you do run Alkaline, take them out when your radio isn't in use. And definitely stay away from Dura-leaks. No Alkaline battery is immune to leaking but they are the worst.

Rechargeable will certainly save you money in the long run. Again, I have 8 years on my 1st set of Ds and they're still going.

I use a Maha charger which seems to do a great job of balancing the cells for use in series.

 

[Reli]

Is your MAHA charger the PowerEx MH-C808M?

 

[Transistorized]

Is your MAHA charger the PowerEx MH-C808M?

Hi Reli.

Yes sir

 

[Reli]

Thanks! The 4-cell charger that came with my Tenergys has a habit of overcharging them to like 13.7V. After I take them out, they drop to 13.3 a couple hours later.

 

[Superduper]

That's called a "surface charge" Reli. All batteries do that. You can disipate that float charge rather quickly by putting a load on it for a couple minutes (or as you've discovered, give it some time to settle down).

 

[Mark34]

Thanks again
So do you recommend leaving all the Alkaline batteries out when not using, or just removing one or two, like another poster suggested?