** Tokyo Marui MP7A1 CHARGER WARNING **
 

Hey Guys!

Will here from Specarms Airsoft.

I just wanna post this up as a heads up for everyone purchasing TM MP7A1's.

As far as I know not too many Retailers out there have these in stock yet, so most retailers haven't even touched / used one of these yet.


I had a friend call me today inregards to the TM Charger that is included in the package.

On the back of the charger it specifically states Input: AC100V 50/60HZ 7.5VA.

Now in North America our wall plugs are AC110V.


Yesterday, my buddy fried his charger already, only after a few hours of owning the item.

So, head to your local Radio Shack and buy a convertor for your MP7's.

I hope this hint helps out other retailers because i KNOW that some people will come back kickin' and screamin'

Thanks for the heads up! I'm sure people will benefit from this! :tup:

Reading on Arnie's you can just clip off the wires, figure out what's + and what's - and then shove it in the charger that you use for your normal AEG batteries (assumption that you aren't using a crap wall charger)

At least that's what the European people are doing to cope with the problem.

lol, thats no problem at all.

All AEP chargers are rated to 100v, and mine certainly hasn't either craped out or overcharged. Just read mine, word for word says AC100V 50/60HZ 7VA, and the output is DC7.5v 300mA. Maybe he got a bad charger.

That's excellent logic you're spinning there;

By the same reasoning, my car's gastank is "rated" for 40L, so I should be able to magically force 10% more gas in for 44L.

With the limited electrical background I have, I'd wager that the guy got a bad charger. They should be able to take the 110-120V we have here. It's surprising that this is the first report of this supposed "problem" we've heard so far. Anybody else with an MP7 wanna chime in?

My TM Glock 18c AEP 7.2V Micro Charger reads:

Input : AC100V 50/60Hz 7VA
Output: DC7.5V 300mA

And yes, mine works fine on 110/120vac.

Actually very true on the G18C AEP point.

Let me ask my battery supplier his opinion on this, he's much more knowledgable about batteries/chargers than I am.


There could be a possibility that he did receive a crapped out charger, in that case i scared all of you for no reason :smack:

This is the perspective from an electrician (me). The charger will take the 100-120 volts and step it down as ratio, lets say 12:1. that means if the charger gets 120 volts AC from your wall it will pass through a transformer and be stepped down by a multiplier of 12 (just an arbitrary number, but sufficient for this explanation) to give you 10 volts AC.

This 10 volts AC is rectified to give you 10 volts DC, which is now suitable to charge your battery (neglecting for now other electronic parts like voltage regulators, FETS, etc.)

If you input 110 volts to your charger, the ratio of step down remains the same (12:1) to give you a charge voltage (no load) of 9.167 volts. A little lower, but no biggie.

If you input 100 volts, the new charge voltage will be 8.33 volts.

The ratios I used are arbitrary and are not necessarily what Marui has designed for their charger. But you can see how varying input voltage will affect your output charge voltage.

The reverse however, is also true. If this charger was designed to give 9.6 volts at 100 volts input, increasing the input voltage will also increase the transformer output voltage. A smart charger will not usually be affected by this increase as they usually have some voltage regulation to counter these changes.

If you increase the voltage to the battery during charging, it MAY cause a problem such as increased heat generated during charging. Under really extreme circumstances, like high ambient temperature or excessively long charging time, damage MAY occur to the battery.

The case that Will brought up may be the result of a dud battery, or other conditions not mentioned.

So... if I use my Fuzzy Logic TLP charger on these batteries, I should be OK. Right?

Why yes, it is excellent logic, because I happen to be an electrical engineer. :-x
I will charge slighlty faster that rated, but by slightly I mean possible 2-3% and since it has peak detection you should have no worries.

That's what I was thinking as well. The diffrence from 100 to 110 shouldn't be enough to fry the guts of the charger. Quite strange.

I stand corrected! Just how much of a voltage difference would it be able to stand then?

As a rule of thumb, around 10% either way can be had with little change in the effect. Most households in the US and Canada don't have a perfect 110v system anyways. My house for instance was build ~40 years ago and uses an older, different wiring standard, and as such we get about 104-105v. Doesn't make too much of a difference. The charger system acts as a transformer to step down the voltage and then provide steady current at a rate of 300 mAh. The end result from starting with a higher voltage before stepping it down is that it will carge at a ever so slightly higher mAh. Its a 200mAh battery on my AEP and it charges in about 40 min, just like its supposed to.

The final answer is than I and many others have had AEPs for months with no major disasters, and even the retailers say its ok:
http://redwolfairsoft.com/redwolf/pr...p?prodID=16773

Ouch. That's a silly mistake for TM to make. Japanese mains are 100V. I would have thought that they would have manufactured product for the export market which could handle 240/120VAC.

The little "brick" charger that comes with the G18c appears to be a transformer type adaptor. Not one of the nice new switch mode power supplies which often include universal input circuitry. I would not recommend using it at North American mains voltage.

Transformer type adaptors rarely come with peak detection circuitry for cost effectiveness. I would guess that they use a timer instead. IRC, the output from transformers tends to be more noisy than high frequency switch mode regulated supplies which makes them less amenable to peak detection in the same package.

I don't know where you get 2-3% increase in charge rate. If the input voltage is increased by 20%, the subsequent open cct output voltage is also increased by 20%. IRC the ratio of the battery's internal resistance and the impedance of the transformer will not vary by charge rate at the beginning of charge. This means that you can expect 20% more current flow during the first half or so of battery charge.

20% increased voltage and 20% increased current corresponds to 44% increased power (voltage*current). I would guess that TM wouldn't release a power supply with less than 100% safety margin, but 44% certainly does eat into that margin significantly. Extenuating circumstances like poor airflow or plugging into a power bar crowded with overheating bricks will reduce this margin further. I also note that the G18C brick is manufactured in China. I wonder if it is properly specified.

As a side note, we may be confusing Vp-p and Vrms in this discussion. In general Vp-p is used in discussions for appliance and accessory specifications. Actually I'm not sure if my calculations are correct. IRC I have to convert to Vrms if I want to work with power.