Test Evpower cell board

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Re: Test Evpower cell board

Postby Gordon-Loomberah » Thu Oct 06, 2016 7:38 am

None of my balance modules have failed after almost 4 years of use, but clearly they are not all identical in their behaviour, which is why I purchased another 3 of them some time ago. For a while I was using 2 or 3 on a cell that went high early, as they just do not have enough capacity for 400AH cells. Now I have the new balancing units, I just keep the extra 3 as spares.
Just by feeling them it was obvious that some were dissipating more power than others, and correspondingly the red LEDs glowed with differing intensity, which is disappointing.
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Re: Test Evpower cell board

Postby australsolarier » Thu Oct 06, 2016 7:47 am

besides they are way under powered and kick in at too high a voltage

but they seem to do their job in disconnecting the battery when one cell goes over 4v
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Re: Test Evpower cell board

Postby APR » Thu Oct 06, 2016 8:06 am

australsolarier wrote:you really have to check the voltages just before float.

Yes, I have checked the balance at the tail end of the absorb phase and see a variation of around 30 millivolt from the lowest to highest cell. I am far more happy with these new balancers, but will retain the EV Power shunt balancers also.

A question....or two..... the EV Power shunts make a circuit when the voltage is within range and break the circuit if the cell voltage goes out of range. Is the current carrying capability of these devices adequate to drive a 12v relay coil requiring a couple of hundred milliamperes? And, do I need a diode across the coil to control the back emf?
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Re: Test Evpower cell board

Postby APR » Thu Oct 06, 2016 8:20 am

Gordon-Loomberah wrote:but clearly they are not all identical in their behaviour....
.....which is disappointing.

The voltage/current shunting amps that I have measured has also shown a reasonable amount of variability which I was not happy with. The EV Power devices came with my cells, and I want to keep them and wire them up to disconnect the pack if a cell voltage goes out of range, I have have never been happy with the balancing voltages they achieved. Perhaps if the charger held the cells at 3.65v for an hour or two at low amps the low cells might come up more, but I found the high cells would end up going above 3.65v and the low. Ella didn't catch up.
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Re: Test Evpower cell board

Postby australsolarier » Thu Oct 06, 2016 8:54 am

the ev balancing boards in my system are connected to the ev power disconnect. you might just it get from them. you might have to get into contact with rod from ev-power. both my systems came with the disconnect relays. they are latching relays so do not draw power, just for a short time to change their open/closed status. and they also have a button that could be used as an emergency shut off.
like mentioned before all the voltages are set hardwired and not adjustable. it is certainly better than no shut off at all. so if one of your cell goes over 4v it actives the relay. there are other parameters for the shut offs with ev-power's devices as well.
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Re: Test Evpower cell board

Postby Gordon-Loomberah » Thu Oct 06, 2016 11:49 am

APR wrote: Is the current carrying capability of these devices adequate to drive a 12v relay coil requiring a couple of hundred milliamperes? And, do I need a diode across the coil to control the back emf?


I vaguely recall that it should be 100mA or less, so wouldn't want to attempt operating a relay requiring 200mA - which does seem rather high. Yes, I think a back emf flyback diode would be a good idea.
There's also the trick of charging a capacitor though a resistor to operate the relay- "high" power available from the cap to actuate the relay, but low current through the resistor to keep it actuated, to reduce overall energy use in a non-latching relay.
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