Charging LifePO4 help !

waingroo · Sep 15, 2018

Hi; I get a second hand LifePO4 Schachner 36v / 9Ah batt XLR 5 pin mother-plug (measured, indicates 33V and can spin a brush motor-meaning battery is good). I tried to charge it with a TranzX charger 42V 2Ah XLR5 pin designed for my old TranzX Li-Ion BL05 battery, but the green LED, do not turn red, and both, battery and charger do not get warm as should do when charge.

Baterries (TranzX & Schachner) have the same plug XLR 5 pin and the charger works perfect on the TranzX battery charging it.

Can be different wiring behind the mother plug of the Schachner, or perhaps an electronic issue? Both batteries where made for european market and I suppose that the plug wiring should be the same.

I remind that on the charger write to be used on Li-Ion without telling something if it can be used on LifePO4.

AHicks · Sep 15, 2018

LifePo4 cells are 3.3v vs. LiPo at 3.6v

Thinking a LiPo charger is going to kill an LiFe pack pretty quickly....

billvon · Sep 15, 2018

waingroo said:
Hi; I get a second hand LifePO4 Schachner 36v / 9Ah batt XLR 5 pin mother-plug (measured, indicates 33V and can spin a brush motor-meaning battery is good). I tried to charge it with a TranzX charger 42V 2Ah XLR5 pin designed for my old TranzX Li-Ion BL05 battery, but the green LED, do not turn red, and both, battery and charger do not get warm as should do when charge.

Lipos need 4.2 volts per cell to charge. LiFePO4's need 3.6 volts per cell to charge. And you can't be "sort of close."

waingroo · Sep 16, 2018

AHicks said:
LifePo4 cells are 3.3v vs. LiPo at 3.6v

Thinking a LiPo charger is going to kill an LiFe pack pretty quickly....

Thanks for telling this. Hope I did not damage them and sure I need a LifePO4 charger. Just wanted to charge a bit not to go undervoltage, because it shows 33V.

waingroo · Sep 16, 2018

I'm a bit confused as I can't use a Li-Ion 42V charger bercause I can dammage the LFP battery, instead, searching on google for LFP charger for 36V, it actually have 43.8V. So, a LifePO4 charger provide with1.8V more voltage than Li-Ion one.

All I want, is to charge a bit that Schachner battery, not to dammage the cells because of low-voltage, as now, it shows only 33V.
I have not an LifePO4 charger... I must carefuly use the Li-Ion one just to charge a bit, for protection and not for day by day use, until I can buy an LifePO4 charger. I'll do on my own risk.

The main question was if the 5pin plug of Schachner LFP battery, must have the same wiring diagram? Meaning: mid pin (no.3) as "-" and no.1 as "+" , like how shows on the Li-Ion charger?

AHicks · Sep 16, 2018

Regarding your 5 pin plug, all I'm going to say is it's not at all unusual to have to correct mismatched wiring on components coming from different manf's.

waingroo · Sep 16, 2018

AHicks said:
Regarding your 5 pin plug, all I'm going to say is it's not at all unusual to have to correct mismatched wiring on components coming from different manf's.

Many thanks for the advice! I'll have to open the battery in search for wiring or maybe a burned fuse.

waingroo · Sep 16, 2018

billvon said:
waingroo said:

Hi; I get a second hand LifePO4 Schachner 36v / 9Ah batt XLR 5 pin mother-plug (measured, indicates 33V and can spin a brush motor-meaning battery is good). I tried to charge it with a TranzX charger 42V 2Ah XLR5 pin designed for my old TranzX Li-Ion BL05 battery, but the green LED, do not turn red, and both, battery and charger do not get warm as should do when charge.

Click to expand...

Lipos need 4.2 volts per cell to charge. LiFePO4's need 3.6 volts per cell to charge. And you can't be "sort of close."

Then, can I use a resistor on the charger "+" wire to drop the voltage to 36-37V ? Coz doing some research on internet, I've seen chargers for 36V LFP at 43.8V. Indeed, on the original Scachner charger seen on internet, write "output 36V".

billvon · Sep 16, 2018

waingroo said:
Then, can I use a resistor on the charger "+" wire to drop the voltage to 36-37V ? Coz doing some research on internet, I've seen chargers for 36V LFP at 43.8V. Indeed, on the original Scachner charger seen on internet, write "output 36V".

Absolutely not. Resistors work to drop voltage only when current is constant. During constant voltage charging, a resistor will allow higher and higher voltages through until the battery's BMS fires (or the battery catches on fire.)

To charge those batteries:

1) Count how many are in series.
2) Multiply by 3.6 volts.
3) Measure the open circuit voltage of the charger. If the two are equal (or within a few tenths of a volt) it will work.
4) If not, adjust the voltage of the charger.
5) If you can't do that, buy a new charger.

waingroo · Sep 16, 2018

billvon said:
waingroo said:

Then, can I use a resistor on the charger "+" wire to drop the voltage to 36-37V ? Coz doing some research on internet, I've seen chargers for 36V LFP at 43.8V. Indeed, on the original Scachner charger seen on internet, write "output 36V".

Click to expand...

Absolutely not. Resistors work to drop voltage only when current is constant. During constant voltage charging, a resistor will allow higher and higher voltages through until the battery's BMS fires (or the battery catches on fire.)

To charge those batteries:

1) Count how many are in series.
2) Multiply by 3.6 volts.
3) Measure the open circuit voltage of the charger. If the two are equal (or within a few tenths of a volt) it will work.
4) If not, adjust the voltage of the charger.
5) If you can't do that, buy a new charger.

Ok, I'll try what you told me and I will open the battery tomorrow making some photos of what's inside. Thanks a lot for reply and for help. I will let you know once I done all those things.

e-beach · Sep 16, 2018

LiFePO cells are fully charged at 3.65v per cell. A 36v pack should charge to 43.8v or your bms may not balance you cells. You could charge them at a lower voltage then 43.8, however you will not be able to balance charge them a lower voltage.

How are you metering you batteries, do you access to the bms so you can meter every cell?

Can you post clear and in-focus pictures of you pack?

waingroo · Sep 17, 2018

e-beach said:
LiFePO cells are fully charged at 3.65v per cell. A 36v pack should charge to 43.8v or your bms may not balance you cells. You could charge them at a lower voltage then 43.8, however you will not be able to balance charge them a lower voltage.

How are you metering you batteries, do you access to the bms so you can meter every cell?

Can you post clear and in-focus pictures of you pack?

In fact, the battery I talk about I found it cheap, without charger (like 20$ on internet) having at home a rack for that type (Schachner 36V LPF 9AH made in Austria); and because I never deal with LFP, I asked all questions above. The only battery and charger I have, are Tranzx Li-Ion 36V & his original charger 42V - 5 pin plug. I opened the Schachner battery just to see the wiring behind the plug without seing the BMS. It may have not a BMS as I can see. I also made a scheme of "behind of the cover". Seems that ground is on 4 and 5 pins. Instead on the Li-Ion charger shows it as being the no 3 pin. On the no3 pin of the battery plug, there is a gryish wire who goes on the pack. (I made a scheme for better view plus some photos.)

waingroo · Sep 17, 2018

The Li-Ion charger I have, as you can see, the ground is on the no 3 pin.

waingroo · Sep 17, 2018

billvon said:
waingroo said:

Then, can I use a resistor on the charger "+" wire to drop the voltage to 36-37V ? Coz doing some research on internet, I've seen chargers for 36V LFP at 43.8V. Indeed, on the original Scachner charger seen on internet, write "output 36V".

Click to expand...

Absolutely not. Resistors work to drop voltage only when current is constant. During constant voltage charging, a resistor will allow higher and higher voltages through until the battery's BMS fires (or the battery catches on fire.)

To charge those batteries:

1) Count how many are in series.
2) Multiply by 3.6 volts.
3) Measure the open circuit voltage of the charger. If the two are equal (or within a few tenths of a volt) it will work.
4) If not, adjust the voltage of the charger.
5) If you can't do that, buy a new charger.

I can't really see the BMS on the pack. Nor between the cells or in the box.

waingroo · Sep 17, 2018

Here I found on internet how the replace pack looks. Also, there is no BMS.... Strange!

https://akkuplus.de/Akkupack-fuer-Schachner-RNA-LFP-396-Volt-8000mAh-LiFePO4-zum-Selbsteinbau?utm_source=pricerunner&utm_medium=cpc&utm_campaign=pricerunner

waingroo · Sep 17, 2018

Measuring the Li-Ion battery, it shows the corect voltage of 41.2V at the pin no.1 "+" and the pin no.3 "-". Instead, measuring at the pin no.1 "+" and pin no.3 "unknown gray wire" on the LifePo4 one, it gives 26V, but measuring between no.1 and no 4 "-" gives exactly 33V as measured on the exit + and - . So, I believe that the Lifepo4 Schachner battery, have the negative for charging on pin no.4 and not like the Li-Ion TranzX one on pin no.3 . A dlayed pin (the "-" one) .

I also done some research and people talk about LFP's without BMS in some cases like electric car batteries. Meaning is quite possible for my LFP battery not to use a BMS at all.

e-beach · Sep 17, 2018

OK, please explain to me again why you think this is a LiFePO battery and not a NiMH battery pack.

waingroo · Sep 17, 2018

e-beach said:
OK, please explain to me again why you think this is a LiFePO battery and not a NiMH battery pack.

I thought the same like you, but I bought a sealed battery with a sticker and printed as LFP.

What will be will be. I already put at charge. From charger pin 1 to batt pin 1 and from charger pin 3 to batt pin 4. The green light turned red and battery is charging. I can loose 20 $ if something goes wrong. I believe is better a wrong charging than over-discharged cells.

Here some photos with batt case.

e-beach · Sep 17, 2018

According to the model number it it indeed a LiFePO battery pack.

http://www.elektrobikes.com/Akku

It might be made so the cell groups self balance until it looses it's range due to bad cells. Seems like a cheap way to make a battery, but it might be a way to generate new sales.

Anyway, charge it to 43.8v and see what it will do for you.

waingroo · Sep 17, 2018

e-beach said:
According to the model number it it indeed a LiFePO battery pack.

http://www.elektrobikes.com/Akku

It might be made so the cell groups self balance until it looses it's range due to bad cells. Seems like a cheap way to make a battery, but it might be a way to generate new sales.

Anyway, charge it to 43.8v and see what it will do for you.

For me is better. I don't realy like too much electronics and I use Heinzmanns brushed motors wishing to find a way not to use a controller. I have two NiMh heinzmann batteries too, but are heavy and don't fully charge. Schachner also made NiMh batteries for the same rack, but inside have bigger cells.

waingroo · Sep 17, 2018

I charge it up to 39.4V (from 33).

The charger get a bit to hot and I was careful not to burn it. So, I decided to disconnect it. I'll wait until I can find a cheap LFP 43.8 charger (best if I can see the original one like Volts and amps).

Now I know the pins for charging, also know it have no BMS. Wonder where the two gryish wires goes?... perhaps a thermistor.

Regarding no BMS i've found this discussion. It seems that "The cells automatically balance themselves much like Lead Acid chemistries when charging."

https://endless-sphere.com/forums/viewtopic.php?t=3285

Schachner is not a cheap baterry at all. Is around 500 $. I don't believe is worst made.... even without BMS. I know Heinzmann NiMh that last more than 10 years.

e-beach · Sep 18, 2018

waingroo said:
I charge it up to 39.4V (from 33).

The charger get a bit to hot and I was careful not to burn it. So, I decided to disconnect it. I'll wait until I can find a cheap LFP 43.8 charger (best if I can see the original one like Volts and amps).

The internal resistance of the cells might be causing the charger to work hard, so it gets hot. A 36v 2a LiFePO4 charger will work. They often ship at 44v output.

waingroo said:
Regarding no BMS i've found this discussion. It seems that "The cells automatically balance themselves much like Lead Acid chemistries when charging."

Yes and no. The parallel sets of cells will self balance the best they can, but the series groups will not self balance themselves.
So if you have a weak group of paralleled cells, then the battery will only perform until that group is diminished.

billvon · Sep 18, 2018

waingroo said:
Regarding no BMS i've found this discussion. It seems that "The cells automatically balance themselves much like Lead Acid chemistries when charging."

Nope. Lead acid cells just outgas a bit if you overcharge them. This allows the rest of the cells to "catch up" to the overcharged cells.

LiFePO4 just get damaged and eventually die.

waingroo · Sep 18, 2018

e-beach said:
waingroo said:

I charge it up to 39.4V (from 33).

The charger get a bit to hot and I was careful not to burn it. So, I decided to disconnect it. I'll wait until I can find a cheap LFP 43.8 charger (best if I can see the original one like Volts and amps).

Click to expand...

The internal resistance of the cells might be causing the charger to work hard, so it gets hot. A 36v 2a LiFePO4 charger will work. They often ship at 44v output.

waingroo said:

Regarding no BMS i've found this discussion. It seems that "The cells automatically balance themselves much like Lead Acid chemistries when charging."

Click to expand...

Yes and no. The parallel sets of cells will self balance the best they can, but the series groups will not self balance themselves.
So if you have a weak group of paralleled cells, then the battery will only perform until that group is diminished.

For this battery I've found a chinese charger at 43.8. But the original one seems to have 36V. I seen two photos on internet: One is from a seller and not good quality, and the other photo, with an original labeled charger at 36V. So here is the point! is better a 44V or a 36 one?

Watch the photos. (I think the bad quality photo from a seller is also labeled as 36V)

I already sent an email to Schachner and waiting for an answer.

PS. I charged once again and seems that won't go more than 40.3V ... or hardly the voltage grow with this charger who becomes hot quite quickly.

Indeed. is better with BMS. Without BMS need to be careful for both, overcharging and low voltage.

waingroo · Sep 18, 2018

billvon said:
waingroo said:

Regarding no BMS i've found this discussion. It seems that "The cells automatically balance themselves much like Lead Acid chemistries when charging."

Click to expand...

Nope. Lead acid cells just outgas a bit if you overcharge them. This allows the rest of the cells to "catch up" to the overcharged cells.

LiFePO4 just get damaged and eventually die.

I believe you, but why they ask 500$ for a poor battery in Germany. I'm also confuse with the proper charger as the original is 36 and non-original is 44. On the Li-ion charger, hardly go up to 40V and charger get too warm. One more think :there are two graysh wires... where they go? can be a thermistor or a very well hidden BMS that I can't see it?

Charging LifePO4 help !

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