T
his whole battery thing has got me all wired up. Found this on a EV sight.
================================================================
Zener-lamp regulator////
Lee Hart wrote on 2/26/03:
Here is a design I have been playing with for about a year. I have two working systems installed, and while not as aggressive as a full-blown Battery Management System, it does most of the job and at very low cost.
Battery regulators
Here is the wiring diagram of the battery regulators:
Battery -
5/16" 6 gauge
ring terminal
______________
| \ __ \
_______________|/|__\ / \ |
Battery + | |\| / \__/ |
5/16" 6 gauge ____|__ | __|____ |_____/________/
ring terminal / | |_|_| | \
______________ \____|__| |__|____/ zener diode
/ __ / | | | | | 1N5338B
| / \ /__|/|_____________|_____| 5.1v 5w
| \__/ \ |\|
\________\_____| 2 lamps in parallel
each #PR2
Charge Current Limiter
One simple way to force a charger to limit its output current is to put some resistance in series with its output. A light bulb is a good way to do this, because it acts like a crude constant-current source. The current only changes about 2:1 for a 10:1 change in voltage. For example, an ordinary 120vac 150w light bulb draws 150w / 120v = 1.25 amps at 120v, and about half this or 0.625 amps at 12v.
Wiring diagram:
lamp
120v 150w
__
__/ \__
| \__/ |
| |
charger+__________|___||/__|__________battery+
COM1 /|| NC1
______
hot________| |
| |____
120 | | _| relay
vac | | _| 120vac
| |____| coil
neutral____| |
|______|
children's "night light"
(turns light on in darkness)
Parts list:
1 - 120v 150 watt light bulb and socket (choose wattage for desired limiting current)
1 - relay, SPDT contacts to match charger max amps and volts, 120vac coil (for example, Potter & Brumfield T92 series, DPDT 30a 240vac contacts, 120vac coil, Mouser 655-T92P11A22-120, $10.50)
1 - children's night light with photocell that turns it off when it senses light. Replace its lamp with the relay coil
Locate the night light inside the battery box where its photocell gets exposed to light from any of the battery sensors. When no light is detected, the relay coil is off, so its normally-closed contacts short the light bulb and the charger delivers full power to the batteries. When the first battery regulator lights, it pulls in the relay, which opens the contacts and puts the light bulb in series with the charger, limiting its current.
Usage
Add my zener lamp regulators across each battery.
Add a timer to turn off the charger after a set time. I like the Intermatic mechanical timers that you can set for 0-12 hours with a knob; they count down and turn off ($15-$20).
Next time you charge, watch the lamps on the regulators. When the first one comes on, set the timer to only run another hour or so. If the pack is out of balance, you'll probably find that after an hour, only a few lamps are on.
Do the same thing for the next few charge cycles. Each time, you'll find that more lamps will be on after that final 1 hour of charging, as the batteries get pushed closer to balance. After a while, the last lamp should just be starting to light at the end.
If you have a fairly consistent driving cycle (say 10 amphours/day), you'll find you can set the timer for a specific time (like 5 hours) right at the beginning, and will automatically get that 1 hour extra charging time after the regulators light up.
If your cycle isn't that consistent, you'll have to figure out by trial and error how much charge time to select for each depth of discharge.
You can automate this process by adding a light sensor and high/low relay.
=================================================================
I'm working on my first EV conversion, and am wondering if anyone knows of where I could find a good balancer/equalizer BMS for flooded lead acid batteries. It is for a 96 volt pak.
Alternatively, you can look into multiple-bank chargers. Dual Pro makes a 4 by 15A charger that operates as 4 separate 12v smart chargers. Your 96V system would need two of these chargers. These chargers are connected to each 12V battery (or each pair of 6V) and do their charging without having to separate the pack. The electric boat people are very pleased with how this is working and many are switching back from bigger 48V chargers. The Dual Pro is basically a 900W charger
Pro-Mariner makes a 30A charger that will manage 4 different batteries. This charger has the ability to shift amperage to the neediest battery, effectively allowing for 30A of 12v charging if only 1 out of 4 batteries is low, but since the batteries are connected in a pack, that type of unbalance is unlikely. The ProMariner is essentially a 450W charger.
These are around $600That said, I'm using a 48V Elcon 2000+ with EV Works BMS modules for my lithium pack.
I've also seen some people suggest separate small, inexpensive 12V chargers for each battery. This will perform the same type of balancing as BMS or multi-bank chargers.
Eric
=================================================================
I have seen this too. How does one go about isolating each individual battery for this?
most of the newer smart chargers are isolated...note the most not all.
You don't have to isolate the batteries when charging, as long as the entire bank is being charged at once.
You can imagine that applying a single 12V charger to part of your battery pack will never complete charging the battery that it is hooked up to because the other batteries that are not charging would be adding load. In this situation, the hooked up battery would be taking considerable abuse by having all the current flowing through it to the other discharged batteries.
But if you had a separate 12V charger attached to each battery, charging all at once, each battery has enough autonomy, even while wired in series, to allow the charger to select the charging phase according to that battery's needs. So the first battery to the constant current cutoff would start the constant voltage phase with decreasing amps, even while it's neighbor was getting still taking full amps. You won't get much cross battery flow since they are all in a charging phase and should be close to the same voltage. Once all the batteries get to the constant voltage phase, there won't be any cross flow, because there is no voltage difference. As each charger drops into the float phase, reduced voltage and amps, there will be some minor cross flow, but since the amps are down across the entire pack, the amount of current flow should be negligible. As long as one charger is pushing current, all of the batteries would stay at a higher than resting voltage, but not really getting any more charge. Once the last charger shut off, the whole pack would return to it's resting voltage.
While there is some room for a massively out-of-balance battery to confuse some of the chargers, this strategy will keep the batteries top balanced by tailoring the charge to each battery, so a dramatically out-of-balance situation would be rare. If you noticed that one charger ran consistently longer than the others, it would indicate a failing cell. This is similar to noting that one battery never hit peak voltage and starting shunting with BMS.
This is why the multi-bank chargers, hooked up to individual batteries that are connected in series (like ours) or parallel (house batteries in RV's and boats) work so well in keeping the batteries in balance.
Eric
Well Eric, have you tried it, this sounds too good to be true but worth investigating I priced some smart chargers as low as 40$. ================================================================
Flooded batteries do not need Equalizers. After 3-stage charging, you finish with an equalizing charge of 3 to 5 amps for a few hours. This bubbles the electrolyte and is a way of dissipating energy as ALL the cells come up to full charge.
The ZIVAN NG3 does ALL this and is isolated.
I have an order out for 9 PowerCheq modules for my 120V pack. Another forum user DONEAL has had success with these balancers (11 of them) for his 144V pack. I'll let you know how they work when I get them. I asked DONEAL how they were working and he said great.
I have a single charger for my 10 AGMs and they get out of balance very quickly.
I don't think most people bother with a BMS on a pack of floodies.... if one goes over-voltage at the end of the cycle, it would just gas a little until others caught up.
Dan
=================================================================
more people now days are using lithium batteries because of its various advantages. but lead acid batteries are much cheaper. and generally no need BMS.
maybe you can try to use lithium battery pack +BMS+charger
or lead acid battery+elcon charger
elcon charger has high efficiency and overall protection functions.
we can offer this charger to you at very good price.
Email:sales.wicom@gmail.com
Skype:sales.evparts
supply lifepo4 batteries+BMS+charger
=============================================================
I'm not sure I would use an equalizer on floodies, but if you AGM/sealed batteries... I wouldn't run without them. I bought these.... awesome....
http://www.hdm-sys.com/pdf/hdm_equalizer_specs.pdfI have 5 of them on a 192 volt pack. Equalize 5 amps during charge, discharge and idle. I've even heard of them used with mixed batteries.
Shiva.
=================================================================
I don't think most people bother with a BMS on a pack of floodies.... if one goes over-voltage at the end of the cycle, it would just gas a little until others caught up.
I did this on my pack of 24 6V batteries and ran them for nearly 9000 miles. A charger that will do an equalization charge is all you need. I have a Zivan NG5 that I used. The end charge was about 181V or 7.54V for a 6V battery. It just wastes a lot of power doing so but so would a BMS I suspect.
=================================================================
MK3SMT Digital Lead Acid Regulator ::: One for each battery, ManzanitaMicro.com, very fancy, lots of cool state of the art digital monitoring stuff $125 each.