48V 1000W kit : delivery & question regarding the 48V 2,5A charger

[mitch_781]

Hello, I am new on the forum I just want to share my first impressions regarding golden motor, I also have a question regarding the charger delivered :
- I received my rear motor hub kit 48V 1000W, everything seems to to be ok, everything is conform to my order (I did not tested the controller for the moment,I hope it is the good one because there is nothing written on (nor 36 or 48 volt)), I leave in France and I received it only 2 weeks after my order. (for infomation I had just to pay additional 69euros of tax at the french customs)

I received a charger for for lead acid battery it is written 59V 2,5A, it looks good with a fan inside for cooling.
I have 48V 4,2Ah NiMH battery, is it possible to use this charger to charge this battery :

- Is the voltage 59V on the charger and 48V NiMh on the battery suitable ?

- I think there is no delta peak detection on the charger, but do you know if the chager cut charging after a level of tension ? (if yes which one ?)
If no at which level of tension should I stop charing the battery to avoid overcharging it ? (I know it is important for NiMH battery)

Thank you, I hope somebody can help me

[Lanchon]

NiMH requires a very specific charger, you can't just use any old charger. the charger should probably measure pack temperature, maybe in more than one place to be extra safe. NiMH can't reliably be charged using a cutoff voltage; the algorithm is more complex, google it up. even if you say "this is a low, safe voltage to charge the pack with without using proper end-of-charge detection" you'd be wrong; one unbalanced cell could be overcharging and could catch fire or explode.

golden has shipped many chargers, I think they are CC-CV and may include a low current cutoff in the CV phase. I wouldn't trust these chargers to be very precise though, I'd use them only with a BMS-protected pack so that a failure wouldn't be catastrophic.

BTW, if you do charge you NiMH with an improper charger, check cell balance and make sure to do it where a fire wouldn't have serious consequences.

cheers!

[bernix]

bonjour Mitch_781

je vis aussi en France.
je possede le meme kit que toi.
c'est mon troisieme kit.
un 36v roue avant, un autre 36v roue arriere et enfin le 48v aussi en roue arriere
la taxe... vacherie !
le chargeur est prévu uniquement pour les batteries au plomb
la tensoin est réglée précisément pour le plomb
arrivé au courant de maintient de charge, il coupe.
pas de detection de delta peak.
tu peux l'utiliser, à tes risques.
simplement quand les batteries commencent à chauffer, débranche, c'est qu'elles sont pleines.
tu peux à ce moment vérifier la tension de ta batterie chargée qui do it etre de 40x1,4 = 56v
j'ai dégrossi certains petits defauts sur ces kits.
suis à disposition si t'as des problemes.

à ++

[mitch_781]

OK thanks for your answers, I understand that if one cell on the 40 in damaged, and I just check the voltage to cut the charging there is a risk of fire  because the pack will never go to the required voltage. So I will not do that.

I also did not find any battery management system for NiMH like for lipo so it is not a solution.

I think (hope) this topic would interest lots of people because we are a lot to use nicd and nimh batteries, and it is always better to have 2 chargers like one at home and the other at work, so we have all an lead acid charger not used and the question is how to use it.

the voltage is ok, the current is ok, the question is how to find end of charging.

I think delta peak is just cutting the charger at the maximum voltage or after a very small decrease.

I am not an expert in electronical componants but it should be possible to build a simple system to do that ?  If anybody knows how to build it...

I found componants that do delta peak, the question is now how to use it :
http://www.ni-cd.net/accusphp/chargeur/realisation/composants.php#MAX712%20/%20MAX713

or also a schema (last schema of the page) is named how to make a simple delta peak, but I don't understand how it works and if it is possible to adapt it with our charger :
http://a190754.free.fr/ELECTRO1.php

If anyone has good knowledge is electronic, thank you :-)

[Lanchon]

hi,

your links are in french so no use for me.

> I think delta peak is just cutting the charger at the maximum voltage or after a very small decrease.

I think I remember the EoC detection for NiMH involves various independent cutoffs: max voltage, "delta" detection, time and temperature. Even so, sometimes it fails.

> the voltage is ok, the current is ok, the question is how to find end of charging.
> I also did not find any battery management system for NiMH like for lipo so it is not a solution.

a system that detects EoC and disconnects the charger would be a BMS.

detecting the "delta" is possible measuring a single cell. I don't know whether it gets more difficult the more series cells you connect; you may need to measure more than just total pack voltage. I've seen NiMH packs in which subpacks of 10 cells were charged independently; but I don't know the rationale for this limitation, maybe they just had 12V NiMH chargers.

if you don't have EE experience maybe your best option is to buy a charger. now you just have a power supply, but a NiMH charger is much more complex.

[mitch_781]

Hi,

Thank you for your answer, I already have a smart charger for NiMH but it is a 24V with 1,2A so with my 48V and 4,2Ah it is not so easy to charge the pack every night (I will have to do it in 2 times).

So that is why it would be a good opportunity to convert the lead acid charger to a delta peak charger.

Regarding the other protections (temp, voltage and time), it is easy to add a timer to the charger so I will do this in case delta peak fail.

the first link is just a list of all the componants used in the chargers (description of use is often in english)

the second link and the last schema explain how to buid a simple delta peak, the translation is :

This electronics compare with the use of a LM358 (max 32V), the voltage in the battery and the voltage of the battery stored in the capacity which decharge is stopped by a diode. The question is to find the good capacity which can store the voltage a long time to be able to catch the voltage reduction as quick as possible.

I don't know if this electronic could work , if somebody knows ? thank you
and if there is another LM358 that could go to 48 or 72V ?


Also about charging a NiMH pack, we have to catch a reduction of 5 to 10 mV.
There is an interesting graph at the end of the following page :

http://www.ni-cd.net/accusphp/theorie/nickel/charge.php

Thank you have a nice day