blackbox avatar image
blackbox asked

Issues with BULK CHARGE not staying on. MultiPlus 12/2500/120 with Multi Control

Not so new but still good Trojan deep cycle 6 volt large battery bank (12 units),
Charging system:
Solar panels, micro hydro electric,
New Genset Honda 2200W Inverter connected to battery charger.

I can't get the charger to stay on "Bulk charge" like it should. The built in charger kicks off quickly to taper down to float charge way before the battery bank is not even close to be charged. It usually kicks off Bulk charge in about 5 minutes.

  • I keep the multi control setting at 18. (Could it be higher with 2200W genset???)
  • Solar panels/micro hydro seem to charge the battery bank no problem...

Possible causes of charger Bulk charge issues?

  1. My guess is the battery bank is getting old and I need to readjust the settings (INFO PLEASE...)
  2. Wrong charger settings? (INFO PLEASE)
  3. Bad connection? (checked everything)
  4. Faulty temperature sensor? (Checked connection) (Should I disconnect it for test?)

I disconnected the solar panel system and getting the same problem...

Thank you Victron. These units are amazingly durable and well built. This community page is well put together AND HELPFUL (I hope!). I will definitely get a new unit if this one ever gives up...

Patrick, Canada

battery chargingGeneratorfloatlead-acid
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1 Answer
JohnC avatar image
JohnC answered ·

Hi Patrick. I'm not sure why you're worried about a short Bulk phase, but you're not the first to 'complain' about it.

To me, Bulk is a transition state, a place to passthrough on the way to the goal of Absorb and ultimately Float states. And the least time I spend there in Bulk, the better my batts get charged. Some Victron charge algorithms may delay the passage a little for batt protection, but this largely shouldn't be an issue for you. Charge rates can also be limited if you choose, to satisfy batt maker's specs.

* Your 18A set limit (@ 120V ac) is right up there at your genny's limit, and if you ever reach it, the genny will be working awfully hard.

* 3x chargers working together will surely reduce your Bulk time too. Once Abs/Float is approached, the charger(s) with the lower target will fade off, leaving the one with the higher target to maintain the charge state.

1. I once 'inherited' a bank of T105's, 12x @6V @12V system, and it became a balance nightmare. I won't expound, but ask if you need more info.

2. I use 14.4V Abs, 13.8V float (+/- temp comp) for those batts. Typical Victron defaults..

3. Likely not your issue, but if you run a multimeter across each of your batt connectors (from the stud itself) it should read 0.00V. Especially important for you.

4. Again unlikely, but if you watch your batt V's, you'll notice it happening in extreme temps. +/- 0.3V from the setpoint perhaps the max you'll ever see.

Yeh, I'm an end user and like Victron kit too. You could have called yourself 'Bluebox' too, hey.. :)

Hope these ramblings help. Return for more if you need..

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blackbox avatar image blackbox commented ·

Thanks John

My issue is I want the gas generator to charge the battery bank back up quickly so I don't waste fuel...

When the battery bank was new, the bulk charge stayed a lot longer then that. So I assume because the batteries are getting old, I need to change the setting to help things along. I have seen no issues of excessive gassing either on bulk charge.

Now, the charger goes to float charge rather quickly and the battery bank is definitely not charged. One peculiar thing is if I reset the Shore limiter control back to zero, then to 18 again, it starts again at bulk charge but again, won't stay there very long.

I don't think Bulk charge is really an issue for the battery bank. 1800 watts divided between all the batteries amount to about 150 watts each of charge. The batteries should be able to handle that rate of charge much longer than that.

I'm assuming because the batteries are getting old, I'm guessing they resist charging thus show a false reading of higher voltage when charging. I assume I can tweek somthing to conteract that. I'm not sure which setting to change...

I think it is may be possible to tweak the setting to compensate for the battery bank getting old.

I will try to disconnect the temp sensor and see if it makes a difference. Hopefully somebody will come up with some idea to tweak the settings to get it to stay on bulk charge longer...

Also, I'm wondering how to do an equalizing charge. Different voltage between the cell may also throw the sensors off somehow...

Never had to do any of this because everything used to work just fine. Just ttrying to get another year on the battery bank since I'm replacing my solar panels soon...


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JohnC avatar image JohnC ♦ blackbox commented ·

More random ramblings.. :)

* The shorter Bulk time isn't an issue in itself, but may be indicative of faulty and/or imbalanced batts.

* Cold batts are more reluctant to accept charge (& you're in Canada), so not much point removing temp compensation. If the charger is set up right, that should look after itself, raising the target V's to where they should be.

* Now firstly (and cringing with bad memories here), check your batt temps in the later stage of a charge. If you have an IR unit to do that then good, but you could just touch each one to see if you can detect a difference. If noticeable, you have a problem.

* If you have a faulty batt(s) you have to find and eliminate it. It may not be the hot one either, but it's mate in the same string could cause this too. Disconnect the mid point wire in each string and check each batt alone for V. Don't do this unless you've left the system to stand for a good long while, as a spark may cause a batt explosion, and your day will take a turn for the worse. :(

* Any batts that won't hold V on their own, remove & run with less strings.

* You could also test the mid-point V's under charge, and this can often help with diagnosis.

* Equalize to maker's specs, but best not to do this unattended, or before removing any duds. It may destroy rather than revive them if imbalance exists.

Good luck..

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blackbox avatar image blackbox JohnC ♦ commented ·

Thanks! I'll definitely look into the battery bank issue.

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