NiMh Battery Charging (Dive-Xtras DPV) Issue?

[TheTrickster]

Haven't used my Sierra for a couple months, so I stuck the battery on charge a few days ago. I'm pretty sure the charger was working okay last time I used it!

But I think I'm either not reading the instructions probably or my charger is faulty...

Anyway... I put the battery on charge and it started normally (Yellow LED) and did the conditioning and main charge, it then continued to the ‘Supplemental Charging’ stage (Green Flashing LED)

- This is where is stays (with the fan on) it does not proceed to the Solid Green ‘Charge Completed / Trickle Charge’ stage - even after being on charge for over 10hrs (at this point the battery is very warm). The battery reads (via a Voltmeter) 29.2v - so the charger is 'charging' batteries - but I just don’t understand why it is not proceeding to switch to the trickle charge stage (Solid Green LED).

I disconnected the battery (let it cool) and burned tested the battery (standing in 50cm of water) and get over 50mins in high gear with it trimmed fully out so the battery (I feel) is good. After this I let the battery cool down and repeated the charging again - and again only gets to the Supplement charging stage - and also reads 29v.

Notes:
1. Charger starts up okay and does the pre-checks (3 Leds on, then only the Red)
2. Connecting a ‘warm’ battery - makes the Green/Yellow LEDs flash - so it looks likes the thermostat is working.
3. Fan is working, again so charger thermostat is working.
4. Charger is the newer black version

Anyone else using a sierra with similar results?

---------- Post added June 30th, 2014 at 05:13 PM ----------

This is the charger I have :

 

[lucca brassi]

It is good thing a charger which have PC data acquisition that could monitor charging curve , which may tell much more than any burning test

like Radio Control Planes, Helicopters, Cars, Boats, FPV and Quadcopters - Hobbyking or http://www.elprog.com.pl/english/?strona=1_firma&pstrona=02/01

(you need 24V which mean 20 cell NiMH (1,2*20 ) or more (reserve ; sharger adapt itself on required voltage) .. Cycle a few times with discharge/charge auto function.

software you get here Downloads & Infos | LogView

 

[TheTrickster]

Thanks Lucca,

I'm really thinking its the charger at fault, and might look at something more intelligent and informative... so thanks for the links..

I've tested the thermistor with my voltmeter, which I believe is a 10KΩ NTC type (not taken the battery apart to confirm mind)

Tested by measuring the resistance between the white and black wires from the charger plugs.

When the battery was warm last night after some charging it was reading around 5.2
This morning, when the battery was cool it was reading around 8.7
So it appears the battery - and the thermistor are okay.

 

[lucca brassi]

measure temp and compare to the table http://www.veris.com/docs/support/faq/rtd-thermistor_z202030-0n.pdf but termistor is hard to fail.

normaly is problem with some invidual battery which might have different interal resistance . Good charger in last phase rise up voltage for some value of 1 volt and get final push if because of resistance or

some other problem can not achive that , battery can not get full capacity

 

[TheTrickster]

Thanks for that PDF - that sort of confirms to me that the Thermistor is working

Here its warm - 25'c+ So this morning reading of 8.7~ would be about right - and that hotter reading yesterday giving me a lower reading would put the battery in a temp range of about 44'c (at a guess)

 

[lucca brassi]

well it is very annoying work ..., but you have to measure interal battery resistance , that mean you have measure voltage of invidual battery because

I is common = U1 /R1 =U2/R2 = U3/R3 =....= U20/R20 good battery have almost all discharging time low resistance

and U common (24V) = U1+U2+.......+U20

and it must be measured several times under load ( double car front light 12V+12V or something similar )

Technical Tips for NiCd and NiMH Battery Pack Users — CamLight Systems

 

[TheTrickster]

Okay Lucca - its a bit beyond me

The battery only has (from me about 5 charge/discharge cycles) and was built on the 10th Oct 2013 - So if an issue with the battery it will go back for replacement!

 

[Scubadude_LA]

I have the same charger on a sierra pack. Battery gets very warm charging. But from a full burn test to full depletion, 10hrs seems too long in my experience.
29.2 sounds too high, my pack is about 27ish when the charger goes green.

Call Will at Dive Xtras, he has helped me in the past.