Robbert
Solar Enthusiast
Parallel over night with a low SOC, doesn't make a difference.
Just put the pack in series, charge and after that a regular top balance in parallel. That is the fastest way.
Can I pre-charge before a top balance with my hybrid inverter?
- Thread starter Devo1982
- Start date
Just put the pack in series, charge and after that a regular top balance in parallel. That is the fastest way.
Devo1982
New Member
Okay, so it's all hooked up and currently charging at about 30a on my hybrid inverter. Stupid question but how will I know when one of the cells hits upper voltage limit and BMS shuts off? Because charging current will drop to zero?
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Devo1982
New Member
Devo1982
New Member
After a few hours at 30amps
Yes the bms should disconnect the charge MOS and leave a message in status information of the Daly. I like to be there and watch the first time, I don’t trust a new bms to do what it should. Did you review the defaults settings? The problem you may incur is when the charge stops (bms or charger) that bms may also stop balancing. Daly only balances on charge AND above balance active/start setting(3.4?) Hopefully you don’t trigger a high cell before you reach balance start and once you do, lower the charge current just enough to keep the balance active so that you can make slow progress to end of charge voltage in your inverter/charger. If you can’t progress, you can try again with a more powerful auxiliary balancer like a Heltec. Only one balancer should be on at time so turn the Daly’s off. This will speed up the fine balance. Once the pack is balanced your charge should never end because it relies on a trigger of a bms safety, but because of your end of charge setting. 27.5 to 28 volts is a good normal day to day end of charge voltage and doesn’t stress the cells. You gain very little going higher.
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Robbert
Solar Enthusiast
Looking good. The bms should disconnect charging if one cell reach high voltage. After that you can disassemble the pack, put it in parallel and do the final top balance. Depending on the difference in SOC, that still can take a day. But than you have a perfectly balanced pack.
Devo1982
New Member
Thanks for the comments and kind words. One last question I do have is what are the scenarios where you would bottom balance rather than top balance please?
Devo1982
New Member
So last night my batteries were happily charging at 30amps. Then we had a power cut from 10pm to 4am, so they were actually put into use. Now, this morning they won't charge above 17amps, even though the inverter is set to 40! Any reason why?
None of the batteries are anywhere close to my 3.6v protection limit.
None of the batteries are anywhere close to my 3.6v protection limit.
Devo1982
New Member
Cell 2 ran away earlier and triggered high voltage disconnect. But look at the other cells! They're way behind 
Devo1982
New Member
Update - I've now got all my batteries configured in parallel doing a top balance using a desktop psu at 3.6v. Let's see how they perform once they are all balanced and back in series with my BMS.
Looks normal for first trip near the top. If possible use some good wire about #8 to speed it up, the test leads the that comes with most power supplies are inadequate. Also connect to the battery from opposite ends. So that no battery has a shorter path.
It still could take a few days depending on the power supply.
It still could take a few days depending on the power supply.
Devo1982
New Member
I'm having to top balance them in two groups of four cells as I only have eight busbars. Not ideal, I know but I'm hoping the end result will be acceptable.
Devo1982
New Member
Robbert
Solar Enthusiast
Looking very good!
Devo1982
New Member
I've got BMS cell high volt protect set at 3.6v (28.8v) and low at 2.8v (22.4v). My hybrid inverter is set to 28v bulk charge, 27v float and 24v low disconnect. Does that sound okay?
Robbert
Solar Enthusiast
Yes that sounds good. Many people here on the forum go even a bit lower with bulk (3.45 per cell or even lower than that). I am pretty new in this game as well, but after reading the forum and watching tons of videos I lowered my bulk to 3.45 as well. Don't know if it makes a huge difference in the long run and life expectancy of the cells. Wrt the usable energy stored in the battery, it almost does not make a difference. Your settings sound ok, taking the recommended profiles on the forum into consideration.
pablo131
New Member
crimp, ideally with a quality hydraulic crimper.
Daddy Tanuki
Solar Wizard
they are talking about the BMS wires not the main cables. don't think they make dies that small for a hydraulic crimper.
Devo1982
New Member
Quick update: no power overnight so new batteries were working hard. I'm very pleased with that cell voltage diff this morning:
chrisski
Solar Boondocker
- Joined
- Aug 14, 2020
- Messages
- 5,602
I found there was A little bit of art to finding the best bulk and float settings.
I ended up going with 3.475 per cell In bulk charge, for float, I ended upsetting it so that when my batteries were fully charged by noon, I slowly put the float setting up to where power in from the SCC equaled the loads in the house. For my Victron SCCs, float ended up being equal to the bulk charge mode. That way I did not go into the night with a battery pack at 80% once the sun set. I want to go into the night at 100 %.
When I had float set lower, I found that once my batteries were fully charged, I might turn on a 300 watt load, and the SCC would only put 100 watts back in the system. In my case once I was charged at noon, there were five or more hours left where I could get enough energy from the sun to cover the loads. Don’t want to start the night at a low SOC.
When I started designing my system, I wanted the batteries to finish charging when the sun went down. That sounds good, but loads are not a steady kWh per day and very greatly. Anywhere from 1 kWh to 18 kWh per day is what I use. The solar harvest was not consistent. I found anywhere from 1 kWh on a cloudy day to 20 kWh on a sunny day in summer is a good expectation.
By setting float so high, my batteries may die earlier, but not in any time I will truly notice. Perhaps in 10 years instead of 12 Years. Not worth it to me. I can be in the RV up to 2 months a year, and no one really knows how long these batteries will last. I think 10 years is a worst case and at thousands of cycles, I expect my kids could be getting the batteries someday.
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