NiMH Batteries Refusing to Power an AEG

[theoriginaltwig]

Guys,

After 12 years of playing airsoft I've finally swapped my old NiCad batteries for some NiMH ones, however, they are refusing to function my AEG! All I get is the classic quiet motor click as it tries to turn (i.e. sounds like a jammed gearbox). When I fit a normal NiCad the gun functions fine. Here's the setup I'm trying to use:

-Gun; Prime Gen 1 Ltd Edition LR300 (Marui gearbox, 350fps spring, upgraded gears, piston, cylinder, cylinder head, nozzle, spring, bearing spring guide, bearing piston head, bearing metal bushings, the gun is fused with a 20 amp 20mm glass fuse, front wired, with the shortest possible lengths of wire).

-Charger; my old faithful Pro-peak Varipulse 2500 VP (states its for slow and fast charge 7.2-9.6v NiCad/NiMH packs using AC).

-Batteries; all 2 part nun-chuck arrangements (1x 9.6v/4.0Ah, 1 x 8.4v/4.0Ah and 1 x 8.4v 2.3Ah), I've tried fast charging them at 0.8A and slow charging them at 0.3A. The largest battery produced 10.1v on my multi-meter (could be wrong as I'm a biff) and powers a 12v car bulb for ages (I forgot to time it) so there's definately charge in them.

What's the problem? What readings do I need to take with my multi-meter (I'm an electrics biff so don't actually know how to use one!) that might identify the problem? Whilst typing this I thought I'd test them in my bog-standard MP5K; the rate of fire is pretty sluggish. Are the cells likely to be damaged? Do I need to need to increase the voltage or consider switching to LiPo? Am I charging them incorrectly? Why are NiMH apparently so pump!

Thanks for your help in advance,

Twig

[a_flea]

Re: NiMH Batteries Refusing to Power an AEG

Well i'd just switch to LiPo personally... Just a stupid question though, are the terminals on the gun (motor or connector) and battery correct? Sounds like it's clicking against the ARL, might have damaged the battery... Also, have you given the battery a deep cycle charge?

[Stealthkiller]

Re: NiMH Batteries Refusing to Power an AEG

How old are the nimh battery's you are trying to use ?

[theoriginaltwig]

Re: NiMH Batteries Refusing to Power an AEG

Well i'd just switch to LiPo personally... Just a stupid question though, are the terminals on the gun (motor or connector) and battery correct? Sounds like it's clicking against the ARL, might have damaged the battery... Also, have you given the battery a deep cycle charge?

I thought this too; the Tamiya connectors are fitted correctly but I couldn't see the +/- on the cells due to the protective heatshrink. So rather than go cutting them open I carefully tried swapping over the motor connectors in the pistol (my logic being that if plus and - were reversed the motor would be going backwards) and I got exactly the same thing. It's definitely not a problem with the ARL/gearbox as the gun cycles skirmishes perfectly all day when I run the gun on a 3000mAh 9.6 large battery mounted in a fake-LAM. My assumption is that the clicking is the motor lacking the 'umph to cycle the mechanism.

The batteries were fully dischargered (using a 12v car bulb) although I don't have one of these posh new digital chargers. My deep charging cycle do you mean slow charge?

How old are the nimh battery's you are trying to use ?

The cells are only 12 months old, and have only ever gone 3 charging cycles (or rather attempts). I've had them since new.

[Stealthkiller]

Re: NiMH Batteries Refusing to Power an AEG

A bulb won't tell you if the battery is fully charged . Sounds like a dead / non charged battery to me . Maybe your charger isn't charging them properly , remember you need 4/ 6 hours if the nimhs are flat

[theoriginaltwig]

Re: NiMH Batteries Refusing to Power an AEG

A bulb won't tell you if the battery is fully charged . Sounds like a dead / non charged battery to me . Maybe your charger isn't charging them properly , remember you need 4/ 6 hours if the nimhs are flat

I've already done the maths, and given the size of the cells I've both slow and fast charged them for the correct amount of time. Additionally, the charger allegedly tells you when it thinks the battery is charge (fast charge only), at which point it flicks to a fast charge. Whilst the bulb won't necessarily indicate an exact charge, the brightness and amount of time that it's staying on (several hours and comparable to one of my NiCads) does suggest that there's definitely a healthy charge going into the battery.

I was thinking perhaps a dead cell? But then that wouldn't be the case in all three batteries!

[Stealthkiller]

Re: NiMH Batteries Refusing to Power an AEG

The bulb isn't drawing the same ampage as a motor and mech box !
On minimal load a battery will light a bulb , but won't have enough power to turn a heavier ampage draw . Ie your motor

[theoriginaltwig]

Re: NiMH Batteries Refusing to Power an AEG

Finally solved; a combination of some poor batteries and what can only be described as a "yee-haa" gearbox spring being fitted by the gun's supplier (despite quoting it as an M100 on the invoice...... Thank god I hadn't skirmished the thing...... However what I can say is that 11.1v Lipos absolutely rock and I'm never going back to NICADs!

[Mickydoos]

Re: NiMH Batteries Refusing to Power an AEG

Finally solved; a combination of some poor batteries and what can only be described as a "yee-haa" gearbox spring being fitted by the gun's supplier (despite quoting it as an M100 on the invoice...... Thank god I hadn't skirmished the thing...... However what I can say is that 11.1v Lipos absolutely rock and I'm never going back to NICADs!

Question mate: Do you have a MOSFET fitted? A 11.1v LiPo will end your trigger contacts pretty soon...

[Stealthkiller]

Re: NiMH Batteries Refusing to Power an AEG

+ 1 to that

[theoriginaltwig]

Re: NiMH Batteries Refusing to Power an AEG

I had already ordered a cheap and cheerful non-braked Airfet MOSFET; I don't really use the gun enough to warrant spending anymore and I don't need any of the fancy features.

On a similar vain, can anyone suggest a really-small (and ideally inexpensive) MOSFET that includes a built in thermal fuse? I now want to use an 11.1 in the buffer-tube of my C8 (I want the ROF to be even -ore insane for CQB), but there simply isn't the room for a MOSFET and a normal inline-fusebox. Any suggestions?

[Sir Stephen]

Re: NiMH Batteries Refusing to Power an AEG

i can't tell you where to get it form but there is a retailer who sells thermal fuses separately for £10. would just be a case of soldering it into your positive line