I have a battery that has charged for around seven hours on a 5A charger and wont go above 38 volts. Unless I'm reading the multimeter wrong. which on setting for 150 volt dc range it says to add 20 to whatever it reads, and its reading 18. soo this is where I'm at. Dogman mentioned to charge it for days in order to let the BMS balance? is this safe? is this what I should do?
this is the battery.
http://conhismotor.com/ProductShow.asp?id=343
Sounds like you have an old analogue volt meter. I still have a couple of those hanging around. If you know how to read them then they are OK, but not as accurate as a modern digital multi meter (DMM).
Go out and get a DMM tomorrow and meter the pack. If you have a Harbor Freight around then they have inexpensive meters. Radio Shack has DMM's but they are more expensive.
As for leaving the charger on the pack over night..., if your bms is working then you are fine. I sometimes leave my charger on my pack for 24 hours but that is because I periodically check my charging progress with my DMM to make sure my charger, bms and batteries are all working in harmony. Nothing left to chance.
yep, the hole on the left where it says 10A is for measuring current only. do not put the probe in there and touch the battery. yep, i have done that too, 3 times.
make sure you use the voltmeter scale and never put the probes on any voltage source unless it is on the volts scale. if you put it on the ohmeter or amps scale and touch the battery it will blow up and you have to buy a new one. yep, done it a buncha times.
Until the green light on the charger goes on.......and then longer still. The charger should indeed stop charging at 54.6v. Now, the problem here IMHO is that your pack is sealed up and there is no way to really know if the cells are balanced unless you open the pack and meter the BMS wiring or the cells individually.
But before we get into that, just let it charge until the charger stops charging.
actually you can tell if the pack is balancing without opening the pack and measuring each cell.
if you measure the charging current then you can tell where the charging current drops down to the level of the current that can flow through the shunt resistors.
if you knew what size the resistors are on that BMS you could calculate it exactly. sometimes it is 100ohm, sometimes 50, sometimes 33 but they don't tell you stuff like that when you buy it.
but if you can measure the charging current you can tell when the pack is balanced by the amount of current flowing out of the charger.
that is what the 10A plug hole is for. you use it to measure current. so get some alligator clips and solder them onto a jumper cable and then run the charging current through your DVM set to the 10A scale, and with the black probe in that 10A hole.
the current reads positive when it goes through the meter from the red probe to the black probe.
I hope u meant to say put the red probe in the hole marked 10A (on the left) and leave the black (common) in the black hole. Make sure u don't use the red hole on the right when reading amps (current). I don't know any meters that really care when reading current but it best to develop good habits in beginners. If he always uses the black as common will make more sense when reading voltages.
Omnivore, it would be a good idea to get a basic book on ohms law and make sure u understand the difference between redaing current (in series) and reading Voltage (in parallel or across it) Then u mightnot blow up any meters...... as an example: when reading current on the Amps scale, the current actually flowsin series through a heavy loop of wire called a shunt in the meter and the voltmeter is connected across this shunt and actually reads the voltage drop. This is then displayed as current......on an analogue meter, simply by markings on the current scale.
no, i never said anything like that and i did not say to plug the red probe into the 10A spot like that guy said i did.
you use the ammeter as a measuring tool in one wire of the circuit, not across the voltage of the circuit.
so to measure the charging current you would need to open one of the wires carrying current from the charger to the battery and insert the ammeter inline. not across the charger output.
if you have access to the BMS then you can put the ammeter in the wire that goes to the charging spot on the BMS.
or you can put it in the positive lead to the battery from the charger.
but inline with the current flow, and you cannot put voltage across the ammeter because it has no resistance in ammeter mode and the meter will blow up. i am surprised it did not blow up when you did that already.
i had just blown up the 15A fuse in my meter like his but they want to replace it with a great big Bussman type that cost like $20 so i popped my old one out, and since the fuse holder is for the big body/hi voltage type fuses, i had to solder a small 5x20mm fuse onto the traces going to the fuse holder. i was able to get the cover back on so now i have only a 10A glass fuse instead of the big 15A fast blow/hi voltage type fuse.
I quote " and with the black probe in that 10A hole." and u want to be careful swapping fuse values.....once had a crypto set go down because the op put an incorrect fuse value in that was the wrong resistance.....(not complaining mind u, got a trip to Burma out of it) .. they say oils aint oils...(well they do here) well fuses aren't always fuses....especially in their operating times...you can ? (could) buy fusewire and replace it in the glass/fibreholder by soldering it in.....remember the fibre ones are used t reduce the risk of fire. 15A glass fuses can shatter....seen it many times...
PS remember fuses have resistance otherwise they won't operate (blow) at their advertised value... P=I x I x R ??
