The Heybridge Railway, 1889 to 1913

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RichardG

RichardG

Western Thunderer
simond said:
we use Ansmann extensively for our products at work.
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One of the negatives of retirement is you lose all connections with current practices. Still, it sounds like I am in good company.

simond said:
I would want to check, but my recollection is that NiMH chargers will detect the battery voltage and simply float continuously once they’re fully charged. They don’t shut down per se, but the current will be tiny.
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I have checked the instruction book for the ACS48, from which I quote:

"The charger continues to charge the battery
pack while connected. Therefore, determine
the charging time based on the table (see
picture 2). Disconnect the battery pack
after the calculated time in order to prevent
overcharging".

This is a menace when the battery manufacturer's claimed capacity is greater than the true capacity.

I have given my battery pack a fresh dose of 116 mA for another 100 minutes, with no sign of the current falling away and no signs of overheating either. So the pack has now had 3 hr 30 min of charge.

3.5 (hours) x 116 mA = 406 mAh, which is near enough the capacity printed on the batteries and rather more than my estimates. Yet I still don't have a clue whether the pack is fully charged.

Something else I don't know is, does the charging process waste power? I mean, if a battery had a true capacity of 300 mAh, and I charged it for three hours at 100mA, would it end up fully charged? Or maybe I have to add some extra energy (extra time) to compensate for losses.
 
simond

simond

Western Thunderer
Oh, that’s not what I expected. Bit of a nuisance, but I guess you could make a timer as a charge controller. Or even a coulomb counter. Arduino?

re your question about adding extra energy. I’d say “yes” because if they get (even just a bit) hotter than ambient, then some of the charging energy has been wasted.
 
RichardG

RichardG

Western Thunderer
From the point of view of a battery charger, the battery pack inside 'Quintus' looks like a rather large PP3 battery. I mean, seven cells, 8.4V, NiMh technology. So I am going to try the Annsmann model 'Powerline 2', which is designed to charge such PP3 batteries. Most of the spec looks sensible:
  • Intelligent charger for 1 or 2x 9V PP3 NiMH rechargeable batteries with 8.4V nominal voltage
  • Automatic charge start after rechargeable battery is inserted
  • Microcontroller-monitored charge control
  • Multiple over-charging protection through voltage monitoring (-dU) and safety timer
  • Fully-charged detection and automatic changeover to pulse maintenance charging
On the downside the charge rate is just 70 mA, so perhaps a four-hour process to recharge 'Quintus'. Better four hours and a cool loco than one hour and a big worry (Vapex) or an indefinite time and indefinite result (ACS48).

If this works, I might convert 'Lady Marion' from LiPo to NiMh. This would overcome a different worry.
 
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