diy solar

diy solar

Compact 4S compression enclosure using Eve LF280K cells

While I'm waiting for a few parts.....namely crimp terminals.........let's talk top balancing.....

I have a 60A Intellepower 9160 series RV charger, it outputs up to 60A at 13.6V.

I also have a fairly generic lab bench supply with a max amperage output of 5A.

My plan is to assemble the pack with the BMS, charge it with the intellepower to 3.4 volts per cell (13.6V for 4S), then rewire cells in parallel and use the bench top power supply fine tune top balancing at 3.5 3.55 volts or so.

The cells arrived all charged at 3.29V and I'm thinking it'll take a month of Sundays to get to 3.4+ volts per cell with the 5A lab power supply.

......is this a bad idea?
 
While I'm waiting for a few parts.....namely crimp terminals.........let's talk top balancing.....

I have a 60A Intellepower 9160 series RV charger, it outputs up to 60A at 13.6V.

I also have a fairly generic lab bench supply with a max amperage output of 5A.

My plan is to assemble the pack with the BMS, charge it with the intellepower to 3.4 volts per cell (13.6V for 4S), then rewire cells in parallel and use the bench top power supply fine tune top balancing at 3.5 3.55 volts or so.

The cells arrived all charged at 3.29V and I'm thinking it'll take a month of Sundays to get to 3.4+ volts per cell with the 5A lab power supply.

......is this a bad idea?

I charged eight cells in parallel with a 10 amp power supply. I used up a month's worth of patience, but it worked out well. I think mine took no more than three days. Your approach is OK.

I would take it all the way to 3.65 volts in parallel.
 
Thanks......I've been reading here on the forum tonight......either 3.6 or 3.65V seems to be the target voltage. I get the idea that you want to balance a bit higher than your max BMS voltage cutoff...so there is less chance of a cell wandering as you pass through say 3.5 or 3.55 volts in normal operation.
 
Thanks......I've been reading here on the forum tonight......either 3.6 or 3.65V seems to be the target voltage. I get the idea that you want to balance a bit higher than your max BMS voltage cutoff...so there is less chance of a cell wandering as you pass through say 3.5 or 3.55 volts in normal operation.

Many of us get to 3.65 volts, but do it in steps rather than setting the charge voltage at 3.65 volts right from the start.

My BMS high voltage disconnect is 3.65 volts as I recall. I have my charge devices set such that the cells would never come close to that. So the BMS is really there as a failsafe. After two years, my cells still end up well balanced.
 
I got the crimp terminals, and fully threaded 3mm x 30mm long screws to allow the BMS to stay assembled when removing it from the top plate.

I also ordered a 175A class T fuse and whipped up a fuse holder from some scrap Delrin and aluminum and mounted it to the front plate.

The fully threaded screws essentially replace the stock screws and just protrude from the heat sink enough to fasten the BMS to the top plate with the isolation spacers and some nuts..........using screws from the smooth heat sink side keeps the BMS from falling apart when removing it from the top plate. Fully threaded 3mm machine screws get rarer then hen's teeth in lengths exceeding 30mm, although McMaster has a few longer lengths.

I also doubled the belleville springs on each threaded rod from four (two stacks of two) to eight (four stacks of two); this cuts the spring rate in half and doubles the displacement for the same minumum and maximum loads. I now have .096" of spring travel instead of .048". If each cell grows by approx .5mm when fully charged I need enough spring displacement for 2mm or .080".
 

Attachments

  • BMS new screws.jpg
    BMS new screws.jpg
    1,007.6 KB · Views: 44
  • fuse holder.jpg
    fuse holder.jpg
    992.8 KB · Views: 45
Last edited:
...After reassembling the battery I charged it with my intellepower 60A charger in the driveway (just in case anything was going to burst into flames... ?). The cell voltages as-received were 3.29V. This charger put out 45+ amps for quite a while before tapering off a bit and got the pack up to a bit over 13.6V.

Cell voltages tracked nicely all the way past 3.4 V......then they started deviating a bit with about 200mv spread between the highest and lowest voltage cells....so I pulled the plug and removed the BMS and topped off each cell with my 5A bench supply to 3.65V. ...then wired them up in parallel and got all of them to 3.65V in short order. The whole excercise took a few hours......I was thinking it would take lots longer.....

I watched one of Andy's (off grid garage) videos on Youtube, and he demonstrated that the JDB BMS balances way more efficiently when you turn off "balance while charging". That seemed to help out a lot when I reassembled the pack and observed the cell voltages over the next few hours. I changed the balance tolerance from 20 mv to 10 mv and voila! a few hours later balanced even tighter.

The battery is now temporarily back in the van and I'm cleaning up wiring etc and installing a Victron DC-Dc converter and MPPT controller; I'm almost ready to do a discharge test with my 1000W inverter, so I've been looking around the house for something that's around 1000W and can run for three hours without melting...thinking the waffle iron. ...and I'll need to remember to reset the battery monitor at the start of the test.

I still need to fabricate the side panels, mount the fan t-stat and the class T fuse when it arrives......
 

Attachments

  • Charging in the driveway.jpg
    Charging in the driveway.jpg
    1.2 MB · Views: 46
Last edited:
Thanks! 2 month update.....Everything is bolted into the van and wired properly...battery fastened down. I've been on two camping trips; first one was 3 days and the second one a week, and the battery works great. Victron Orion charges at about 25A while driving, and 300W of solar adds to that.

After watching a zillion of Andy's (off-grid garage) youtubes, I've been playing with the float voltage in the Victron MPPT controller; cranking it up to 13.8V or more to keep the charging cycles up when camping and 13.4V when the van is parked in the driveway to really stretch the time between charge cycles. ....never thought I'd have a need to bluetooth to my battery but it's pretty sweet. Cells seem to stay really well balanced as long as I stay below the 3.65V ceiling...I've had the BMS shut off charging twice when playing with absorb and float voltage settings.

.....happy camper.........AGMs seem so last-century now.........
 
Very nice set up!
How many Ah is your alternator rated for and which Victron DC-DC charger did you buy?
I am getting ready to order a Victron DC-DC charger for my truck to charge my EVE LF280K battery in 4s configuration.

Thanks for taking the time to post all your stuff!
 
Last edited:
Very nice set up!
How many Ah is your alternator rated for and which Victron DC-DC charger did you buy?
I am getting ready to order a Victron DC-DC charger for my truck to charge my EVE LF280K battery in 4s configuration.

Thanks for taking the time to post all your stuff!
I upgraded the stock 130A econoline alternator to a 200A alternator........the new one had a tag on it that rates it at 130A at idle. The van consumes about 60-70A idling.....checked with my clamp-on ammeter.......it's a 2008 so headlights are on all the time. So I have 60+amps headroom at idle.

Is your truck an F-series Ford? If so the stock alternator for the 5.4L (130A) puts out about 70 amps at idle....there is an output table in the factory service manual......diesels are setup a little different.

I installed the Victron Orion 30 amp charger/converter. It's putting out around 25 amps. The Orion gets really hot.......I mounted a Papst Blower under the Orion heatsink that comes on when the van is running.

...and I forgot to mention above the Amazon thermostat works great; I have that set to about 105F and it turns on the enclosure vent fans and the fan on the battery.
 
Thank you for the valuable alternator data.

My 2018 Silverado truck alternator is rated at 150aH. If I turn on every electrical device on high (lights, radio, AC, wipers, emergency flashers, etc.) at the same time, at idle speed, I pull about 70 aH.

I will likely buy the Orion 18 aH isolated unit, rather than the 30aH unit, to be more conservative.

I already purchased a spare OEM alternator as a back up in case my current alternator burns up. I will turn the Orion off when I am at idle and/or when driving in town at lower rpm's. I will also install a 2 AWG wire from the alternator to the starter battery and run 2AWG wire from the starter battery back to the trailer. The OEM wire from the alternator to the starter battery is only 6 AWG.

Thanks again.
 
Back
Top