Doctorbass wrote:Thanks Inwo for posting that interesting product!
That BMS look very interesting!! as it cover up to 24s and have most of the features we want.
That said, the 1.2A balance current is also very interesting however it is not constant current regulated I guess, it is constant resistance like most BMS bleeding circuit so it also depend on the size and length of the wiring lead that connect to the cells. We must keep in mind that if it balance UP TO 1.2A this is probably for a 4.2V channel witch mean a bleeding resistance of about 3.5ohms. Then if you use a conventional DB25 with 28AWG wires inside and couple foot length this add easy few ohms in addition of the 3.5 ohm bleed resistor this increase the total bleeding resistance value witch reduce a lot the bleeding current, AND also introduce false reading of the cell voltage as there is too much voltage drop in the wires witch also make the BMs to balance some wrong channel. One great way to measure each cell voltage WITHOUT being affected by the bleeding current is to pause the bleeding current for a brief period and measure voltage of the cells during that moment. The Popular 6s balance charger 8A tool model BC168 does that with great results.
1.2 amps is pulsed. Measure-pulse-measure-pulse-etc.
As for the standby current ( Off state), I agree with Luke, that is very important to have it as low as possible. 0.7mA seem ok if we switch ok our EV AND BMS during no use. But it also would be great to have it convinient for some of our <10-15 Ah setup..
I like the fact that the screen is very informative and don’t require a PC or tablet. External remote display option possible? I see you show little PCB but it it an option available?
I make the fpc cable to rj-45 and db25 pcbs. Waiting for results from a customer. I'll post pictures of his progress. Works great for me with 10' cable. I will make them available at low cost to MY customers.
HEAT design management:
It would be interesting to measure how the heat generated by full current balancing could affect the rest of the circuit in term of accuracy. Sometime cheap electronic components are more affected by temperature like capacitor for exemple. As the internal temperature increase, how the cell voltage measurement is affected by that. Could the BMS measurement accuracy drift with temperature variation… Is it well desithen to handle full balance on full channel?.. 1.2a x 4.2 x 23 = 115 watts of heat.. wicth naturally happen in very rare conditions.
Heat is controlled internally. There is no thermal conduction path from internal heatsink to case. For fast balance it must be modified to dump more heat. I have to say, in a couple days it will balance a 120ah 24s pack. 150mv
Does it have the possibility to get firmware upgrade? Will it be well supported by the Chargery company over the time
Yes. Better yet I'm in direct contact with designer. He is open to my suggestions. Already came up with LTO defaults for me. Sometimes getting me new file overnight.
COMPARE TO ? :
To me it is not perfect but it seem way better and complete than many actual existing products. It look like it was designed for large ebike users. My reference of the best design from now is the Adaptto BMS which is already incorporated to the controller and display and also offer BOOST voltage possibility to charge from any source above 12V.
I have a 24s bms with remote display and Bluetooth. Not ready for general market. Works perfectly. Long learning curve. At least for me. I would sell it to an advance user for less than cost. Info by request. A matching boost charger is in the works.
I saw on your ebay auction page that you talk about the compatibilyty to connect to the deltaQ charger with the white trigger wire they commonly use, can you give us more details?
Certainly. When DQ chargers are updated to do Lithium profiles, the wire that previous was temp. sense, is a logic level enable. Pull low to enable charging. The BMS-24 outputs B+ voltage to relay coil. All I do is package an led and open collector NPN to pull to logic low for "enable charger" signal. As internal logic is referenced to B-, it only requires one wire. C to white charger wire.
However, the Chargery 24s BMS can be used stand alone as a tool which is a very good point!
That's what I use one for. Last night and today I'm measuring Volt battery capacity before selling a 4kw pack.
From 4.13 (limit of charger) draining 3.5kw volts of lowest cell = 3.00 bouncing back to 3.05 after removing 10 amp load.
As this was done at 35F, I believe 2012 Volt battery is doing well.