CellLog 8 switching ss relay

[mervchally]

Looking at using a cellog 8 to switch a ss relay (100 a Jaycar ) Was wondering if A/ the CellLog will do the job and 2/ is there a trick to get it to work reliably. I have a 60 ah Li battery that I would like to switch the load off if the battery was to go flat , before it did any damage.

Thanks
Merv .

[T1 Terry]

You need to make the switching ratcheted, as soon as the load is removed the cell/pack voltage will rise and the Junsi will stop the alarm turning the SSR back on, then the cycle repeats. A better method is switching the relay using the relay outputs on a Victron 700BMV. Then you can set the cut off voltage and cut back in voltage as well as state of charge off and back on. This will also give you a better indication of just what is left in the battery. For around the $200 mark they are a worthwhile investment.

T1 Terry

[mervchally]

Thanks Terry, when I ran the battery down a bit one cell voltage was dropping further than the others , so I thought the cell log would be good to switch the relay off if one cell dropped too far , but I forgot about the cut-out/ cut- in problem around a single voltage point.
Anyway I have a BMV 702 so will set that up with mid point monitoring.

Merv

[BruceS]

Ideally you need two separate items to cut off.
One for too low .... cut supply out of batteries.
The other for too high .... cut off solar or charger.

[mervchally]

Yes I was going to use 2 cell log's but unless I can find a control circuit for them it wont work. I have set the Dingo at 13.8 v bulk and 13 float so hope that will work for high volt control. just thinking I wonder if I could use the Dingo to cut off load and BMV to cut off solar, must have a read..

[BruceS]

Not really because both cutoffs need to be at the cell level .... not the battery bank level.
It really does come back to the Junsi's.
Of course you CAN still cut off high & low bank voltages with the two items your mention but you really do need the cell control to avoid cell damage. (if cells get too far out of 'level')

[T1 Terry]

The idea of using the 702 and mid point monitoring will determine if one cell goes low in one pair, as long as a cell in the other pair doesn't go low at the same time. Now the real issue, if you are seeing a cell drop below 3v you are over discharging the battery. 100% SOC down to 0% SOC will still see all cells above 3v even under a light load, so you do need to set up the Victron correctly and stop the discharge at 0% SOC as the very minimum, most stop at 5% SOC. The alarm should be set to 20% and have been screaming and flashing for quite some time before the actual battery isolation cuts in. The isolation is the very last line of protection to avoid damage, it shouldn't be used as a control function.

T1 Terry

[exscott]

Hi everyone,
I have to say after deciding to change up to lithium I have joined a lot of forums trying to research systems with not that much luck. It seems to be a very touchy subject.
So I saw this subject and it's also one of my stumbling blocks. I am planning on using the solar reg for (viltron pwmpro) lvc but I am also after a cell level lvc/hvc. The best answer seems to be a cellog8 switching a latching relay for both high and low disconnect as an emergency backup but I am having trouble finding a high amp (probably 60A) latching relay that can be powered by the cellog.
If anyone has any suggestions that would be great
Thanks
Scott

[BruceS]

The cellog alarm contacts can only provide a small current for any relay or alarm. Most that I know feed them into a mini relay that then feeds the main heavy relay.
There are only a couple I'm aware of that use latching relays. William (Bill) is one.
LVC is a difficult one because if it's already low, there's no point in cutting solar or charging of any sort.
Many have gone the Gigavac contactor route. They need a decent pulse but immediately after they only need a very small amount of power to keep them in. Totally different to a starter solenoid for example!
Terry will chime in with more detail Scott.
Where are you located?

[exscott]

Thanks Bruce I hadn't seen the gigavac site but will look at those and see if theres something with a low enough current draw. The mini relay onto a larger latching relay was something I looked at but obviously not ideal. I am thinking the cell lvd/hvd would be only an emergency backup so a total disconnect with no ongoing power to hold open would be best (besides I guess the cellog) until I can manually check why it has tripped.
Also looks like theres a few of you experienced with lfp still on this forum so will do a few searches on previous posts here for some of my other concerns.
I think I have read every post on some other forums that you guy's used to post on.
Thanks again
Scott