Large Scale Central

Recharging a 9volt?

Electronics Power and Sound
#1

I have a enercell (radio shack) 9 volt NI-MH battery that I’m using in a engine to power an older Dallee sound system. these older systems don’t charge from the track voltage so the battery wears down over time.

The battery is inside the engine under the hood so I put a charging plug in when I was wiring it. I thought I would use a converter but now I’m second guessing the charger I have. It is an adapter with a output of 9 volt 210 mA. I’m concerned this is too much output and will cook the battery.

What should I be using to charge this battery?

#2

That is not a charger, it is an uncontrolled source of voltage and current. Also, you need to see what voltage the battery is, some are 7.2 and some are 8.4.

You probably need a universal charger with a multi-cell nimih setting.

Greg

#3

The battery is a regular 9volt type 170mAh Ni-MH.

I thought the AC adaptor would be OK but I guess not. This electronic stuff is confusing. I do have a charger for batteries but I have to take the battery out of the engine to put it into that. Taking the battery out is not convenient.

#4
  1. no combination of Ni-Mh will make 9 volts, even though that’s what it says on the outside, nimih cells are 1.2 volts… I’m assuming you are using one of the small “transistor radio” types…

6 cells in series will give you 7.2 volts, 7 cells in series will give you 8.4 volts, I have seen both… (you never see them with 8 cells because it is over 9 volts).

There’s nothing different here, all rechargeable batteries need SOME control during charging. Yes, picked carefully, and manually started and stopped, you can charge at a low rate and not damage a battery, but that is a terrible way to do it, and can easily damage the battery.

I’m guessing that because it was a small battery, it would be easier/less hassle to charge. Actually the reverse is true, it is easier to overcharge the battery since it needs such a small charging current, so it’s easy to overcharge.

I’d put a supercap system in there, or bring the battery wires out to an external jack.

Greg

#5

Greg you may be over thinking or I haven’t been clear enough. The battery is a typical 9 volt like you would find in a smoke detector. It is a enercell rechargeable from radio shack. The dallee and mylocosound call for a backup battery for idle sounds until the track voltage gets up high enough to take over. The mylocosound will charge back from the track but according to the instructions I have for the 2 older dallee systems the battery does not get charged back from the track voltage.

I brought the battery wires out of the engine and mounted an external charging jack on one of the engines so far. From what you have written it seems like I need to buy a smart charger with a plug so I can charge these batteries properly.

Thanks for the info.

#6

Yes, you are right, a small smart charger for a 9v is what you need (I think that’s my last statement ha ha).

Not overthinking, just giving you a really complete answer, and for those reading the thread also. The problem with those rechargeable 9v is the 2 different configurations sold “as 9v”… that difference in voltage can cause trouble, and if the battery is inside your loco, the last thing you need is damaged battery messing up your loco.

Regards, Greg